Toxicology
(TOK-sih-KAH-loh-jee) The study of poisons, including the source, effect, and treatment of poisoning. It is a branch of pharmacology (the study of drugs).
Glossary of Toxicology
See abiotic
abiological Not associated with living organisms.
Process in which a substance is converted to simpler products by physical or chemical mechanisms: examples include hydrolysis and photolysis.
Process in which a substance in the environment is modified by non-biological mechanisms.
Substance causes pregnancy to end prematurely and causes an abortion.
Lowest concentration of a substance in an environmental medium which kills 100 % of test organisms or species under defined conditions. Note: This value is dependent on the number of organisms used in its assessment.
Lowest amount of a substance which kills 100 % of test animals under defined conditions. Note: This value is dependent on the number of organisms used in its assessment.
- absorbance, A
Logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects of sample cell walls). Depending on the base of the logarithm, a decadic and Napierian absorbance are used. Symbols: A, A10, Ae. This quantity is sometimes called extinction, although the term extinction, better called attenuance, is reserved for the quantity which takes into account the effects of luminescence and scattering as well. Corrected from Note: When natural logarithms are used, the Napierian absorbance is the logarithm to the base e of the incident spectral radiant power, essentially monochromatic, divided by the transmitted spectral radiant power, Pλ.
internal dose Amount (of a substance) taken up by an organism or into organs or tissues of interest. See absorption, systemic
Energy imparted by ionizing radiation to a specified volume of matter divided by the mass of that volume.
Ratio of the absorbed to the incident radiant power. Also called absorption factor. When α ≤ 1, α ≈ Ae, where Ae is the Napierian absorbance.
See also absorbance
Process of one material (absorbate) being retained by another (absorbent). Note: The process may be the physical solution of a gas, liquid, or solid in a liquid, attachment of molecules of a gas, vapor, liquid, or dissolved substance to a solid surface by physical forces, etc. Transfer of some or all of the energy of radiation to matter which it traverses. Note: Absorption of light at bands of characteristic wavelengths is used as an analytical method in spectrophotometry to identify the chemical nature of molecules, atoms or ions and to measure the concentrations of these species. Corrected from
uptake Penetration of a substance into an organism and its cells by various processes, some specialized, some involving expenditure of energy (active transport), some involving a carrier system, and others involving passive movement down an electrochemical gradient. Note: In mammals absorption is usually through the respiratory tract, gastrointestinal tract, or skin into the circulatory system and from the circulation into organs, tissues and cells.
Phenomenon in which radiation transfers some or all of its energy to matter which it traverses.
Uptake to the blood and transport via the blood of a substance to an organ or compartment in the body distant from the site of absorption.
absorption factor Ratio of the absorbed quantity (uptake) of a substance to the administered quantity (intake). Note: For exposure by way of the respiratory tract, the absorption coefficient is the ratio of the absorbed amount to the amount of the substance (usually particles) deposited (adsorbed) in the lungs.
See absorptance (in chemistry), absorption coefficient (in biology)
Improper use of drugs or other substances.
Substance intended to kill mites, ticks or other Acaridae.
Estimate by JECFA of the amount of a food additive, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk. Note 1: For calculation of ADI, a standard body mass of 60 kg is used Note 2: Tolerable Daily Intake (TDI) is the analogous term used for contaminants.
See no-acceptable-daily-intake-allocated
Acceptable concentration of a residue which has been established for an antibiotic found in human or animal foods.
Probability of suffering disease or injury which is considered to be sufficiently small to be “negligible”, Note: Calculated risk of an increase of one case in a million people per year for cancer is usually considered to be negligible.
Probability of suffering disease or injury which is accepted by an individual.
Unintended contact with a substance or change in the physical environment (including for example radiation) resulting from an accident.
Processes, including selection and adaptation, by which a population of micro-organisms develops the ability to degrade a substance, or develops a tolerance to it. In animal tests - allowing an animal to adjust to its environment prior to undertaking a study.
See bioaccumulation
Quantity referring to the differences between the mean of a set of results or an individual result and the value which is accepted as the true or correct value for the quantity measured.
Equilibrium constant for the following reaction of an acid HB:
where co = 1 mol dm-3 is the standard amount concentration and activity coefficients have been neglected.
Note 1: This constant, because activity coefficients are neglected, is valid at a specified ionic strength. The thermodynamic dissociation constant is found by suitable extrapolation of the conditional constant to zero ionic strength. Note that it is defined as a dimensionless quantity, but sometimes it is given dimensions by omitting the standard amount concentration.
Note 2: Because this constant differs for each acid and varies over many degrees of magnitude, the acidity constant is often represented by the additive inverse of its common logarithm, represented by the symbol pKa (using the same mathematical relationship as (H+) is to pH), viz.:
pKa = -log10Ka
In general, a larger value of Ka (or a smaller value of pKa) indicates a stronger acid, since the extent of dissociation is larger at the same concentration.
antonym alkalosis Pathological condition in which the hydrogen(1+) (hydron) amount concentration of body fluids is above normal and hence the pH of blood falls below the reference interval.
Concentration of a substance in air, soil, water or other defined medium at which specified emergency counter-measures, such as the seizure and destruction of contaminated materials, evacuation of the local population or closing down the sources of pollution, are to be taken. Concentration of a pollutant in air, soil, water or other defined medium at which some kind of preventive action (not necessarily of an emergency nature) is to be taken.
Conversion of a xenobiotic to a more toxic derivative by modification not involving biological catalysis.
See bio-activation
Component of a mixture responsible for the biological effects of the mixture. Compare inert ingredient
Metabolite causing biological and (or) toxicological effects. After See metabolite
Movement of a substance across a cell membrane against an electrochemical gradient, in the direction opposite to normal diffusion and requiring the expenditure of energy.
antonym chronic
Of short duration, in relation to exposure or effect; the effect usually shows a rapid onset. Note: In regulatory toxicology, ‘acute’ refers to studies where dosing is either single or limited to one day although the total study duration may extend to two weeks to permit appearance of toxicity in susceptible organ systems. In clinical medicine, sudden and severe, having a rapid onset. After
Effect of finite duration occurring rapidly (usually in the first 24 h or up to 14 d) following a single dose or short exposure to a substance or radiation. Note: Acute effects may occur continuously following continuous dosing or repeatedly following repeated dosing. After
antonym chronic exposure Exposure of short duration.
See (acute, exposure)
antonym chronic toxicity
Adverse effects of finite duration occurring within a short time (up to 14 d) after administration of a single dose (or exposure to a given concentration) of a test substance or after multiple doses (exposures), usually within 24 h of a starting point (which may be exposure to the toxicant, or loss of reserve capacity, or developmental change etc.). Ability of a substance to cause adverse effects within a short time of dosing or exposure.
Change in an organism, in response to changing conditions of the environment (specifically chemical), which takes place without any irreversible disruptions of the given biological system and without exceeding normal (homeostatic) capacities of its response. Process by which an organism stabilizes its physiological condition after an environmental change. Note: If this process exceeds the homeostatic range, it becomes pathological and results in symptoms of disease (adverse effects).
Difference between the incidence of an adverse effect in a treated group (of organisms or a group of exposed humans) and a control group (of the same organisms or the spontaneous incidence in humans).
Surrender and devotion to the regular use of a medicinal or pleasurable substance for the sake of relief, comfort, stimulation, or exhilaration which it affords; often with craving when the drug is absent.
Consequence which follows exposure to two or more physico-chemical agents which act jointly but do not interact: the total effect is the simple sum of the effects of separate exposures to the agents under the same conditions.
New chemical species AB, each molecular entity of which is formed by direct combination of two separate molecular entities A and B in such a way that there is change in connectivity, but no loss, of atoms within the moieties A and B. Note 1: Stoichiometries other than 1:1 are also possible, e.g. a bis-adduct (2:1). An ‘intramolecular adduct’ can be formed when A and B are groups contained within the same molecular entity. Note 2: This is a general term which, whenever appropriate, should be used in preference to the less explicit term complex. It is also used specifically for products of an addition reaction.
Malignant tumor originating in glandular epithelium or forming recognizable glandular structures.
Benign tumor occurring in glandular epithelium or forming recognizable glandular structures.
In pharmacology, a substance added to a drug to speed or increase the action of the main component. In immunology, a substance (such as aluminum hydroxide) or an organism (such as killed mycobacterium) which increases the response to an antigen.
Application of a known amount of a substance to an organism in a reproducible manner and by a defined route.
Secreting adrenaline (epinephrine) and (or) related substances; in particular referring to sympathetic nerve fibers. See sympathomimetic
Increase in the concentration of a substance at the interface of a condensed and a liquid or a gaseous layer owing to the operation of surface forces.
See also interfacial layer
Ratio of the amount of substance adsorbed at the interface of a condensed and a liquid or gaseous phase to the total amount of the substance available for adsorption.
See astringent
Process of transport of a substance in air or water solely by mass motion.
Change in biochemistry, physiology, growth, development morphology, behavior, or lifespan of an organism which results in impairment of functional capacity or impairment of capacity to compensate for additional stress or increase in susceptibility to other environmental influences. After
Occurrence which causes an adverse effect. Note: An adverse event in clinical studies is any untoward reaction in a human subject participating in a research project; such an adverse event, which may be a psychological reaction, must be reported to an institutional review board.
Organism which requires dioxygen for respiration and hence for growth and life.
Requiring dioxygen.
Diameter of a spherical particle with relative density equal to unity which has the same settling velocity in air as the particle in question.
Mixture of small particles (solid, liquid or a mixed variety) and a carrier gas (usually air). Note 1: Owing to their size, these particles (usually less than 100 µm and greater than 0.01 µm in diameter) have a comparatively small sedimentation velocity and hence exhibit some degree of stability in the earth’s gravitational field. Note 2: An aerosol may be characterized by its chemical composition, its radioactivity, the particle size distribution, the electrical charge and the optical properties.
See etiology
Ability of a poison to produce a change in an organism after cessation of contact.
Quantitative and qualitative age dependence of an effect.
antonym antagonist Substance which binds to cell receptors normally responding to a naturally occurring substance and which produces an effect similar to that of the natural substance. Note 1: A partial agonist activates a receptor but does not cause as much of a physiological change as does a full agonist. Note 2: A co-agonist works together with other co-agonists to produce a desired effect.
Presence of substances in the atmosphere resulting either from human activity or natural processes, in sufficient concentration, for a sufficient time and under circumstances such as to interfere with comfort, health or welfare of persons or to harm the environment.
Network of organizations which monitor air pollution. Group of measures or processes used to minimize or prevent air pollution.
Presence of albumin, derived from plasma, in the urine.
Substance intended to kill algae.
Known amount of a homogeneous material, assumed to be taken with negligible sampling error. Note 1: The term is usually applied to fluids. Note 2: The term “aliquot” is usually used when the fractional part is an exact divisor of the whole; the term “aliquant” has been used when the fractional part is not an exact divisor of the whole (e.g., a 15 mL portion is an aliquant of 100 mL). Note 3: When an aliquot is taken of a laboratory sample or test sample or the sample is otherwise subdivided, the samples have been called split samples.
antonym acidosis Pathological condition in which the hydrogen(1+) (hydron) substance concentration of body fluids is below normal and hence the pH of blood rises above the reference interval.
Substance which introduces an alkyl substituent into a compound.
One of several alternate forms of a gene which occur at the same relative position (locus) on homologous chromosomes and which become separated during meiosis and can be recombined following fusion of gametes.
Immunostimulant antigenic substance which may or may not cause a clinically significant effect but which is capable of producing immediate hypersensitivity.
Symptoms or signs occurring in sensitized individuals following exposure to a previously encountered substance (allergen) which would otherwise not cause such symptoms or signs in non-sensitized individuals. The most common forms of allergy are rhinitis, urticaria, asthma, and contact dermatitis.
Pertaining to a systematic relationship between growth rates of different parts of an organism and its overall growth rate.
Pertaining to a systematic relationship between size, shape, and metabolism in different species.
Regular and systematic pattern of growth such that the mass or size of any organ or part of a body can be expressed in relation to the total mass or size of the entire organism according to the allometric equation: Y = bχα where Y = mass of the organ, χ = mass of the organism, α = growth coefficient of the organ, and b = a constant.
Adjustment of data to allow for change in proportion between an organ or organs and other body parts during the growth of an organism. Adjustment of data to allow for differences and make comparisons between species having dissimilar characteristics, e.g., in size, shape, and metabolism. After
Measurement of the rate of growth of a part or parts of an organism relative to the growth of the whole organism.
Semiochemical that is produced by an organism inducing a response in an organism of another species that is favorable to the emitter. See kairomone, synomone
See quantal effect
Baldness; absence or thinning of hair from areas of skin where it is usually present.
- alveol-us (pulmonary), -i pl., -ar
Terminal air sac of the lung where gas exchange occurs.
Surrounding (applied to environmental media such as air, water, sediment or soil).
Continuous or repeated measurement of agents in the environment to evaluate ambient exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between exposure and resultant adverse health effects.
See environmental quality standard
In vitro test for mutagenicity using mutant strains of the bacterium Salmonella typhimurium which cannot grow in a given histidine-deficient medium: mutagens can cause reverse mutations which enable the bacterium to grow on the medium. The test can be carried out in the presence of a given microsomal fraction (S-9) from rat liver (see microsome) to allow metabolic transformation of mutagen precursors to active derivatives.
Serious illness which is a consequence of consumption of bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing domoic acid; acute symptoms include vomiting, diarrhea, and in some cases, confusion, loss of memory, disorientation and even coma.
antonym catabolism Biochemical processes by which smaller molecules are joined to make larger molecules.
See anemia.
antonym aerobe Organism which does not require dioxygen for life. Note: Obligate (strict) anaerobes grow only in the absence of dioxygen. Facultative anaerobes can grow either in the presence or in the absence of dioxygen.
antonym aerobic Not requiring dioxygen.
See anesthetic
Substance which relieves pain, without causing loss of consciousness.
Process by which a normally non-biodegradable compound is biodegraded in the presence of a structurally similar compound which can induce the necessary enzymes.
Study designed to examine associations, commonly putative or hypothesized causal relationships.
Of or resembling anaphylaxis.
Life threatening type 1 hypersensitivity allergic reaction (see allergy) occurring in a person or animal exposed to an antigen or hapten to which they have previously been sensitized. Note: Consequences of the reaction may include angio-edema, vascular collapse, shock, and respiratory distress.
Loss of normal cell differentiation, a feature characteristic of most malignancies.
Condition in which there is a reduction in the number of red blood cells or amount of hemoglobin per unit volume of blood below the reference interval for a similar individual of the species under consideration, often causing pallor and fatigue.
Substance which produces loss of feeling or sensation: general anesthetic produces loss of consciousness; local or regional anesthetic renders a specific area insensible to pain.
Cell or organism with missing or extra chromosomes or parts of chromosomes and thus an abnormal number of chromosomes which is not an exact multiple of the haploid number.
Strictly total absence of oxygen but sometimes incorrectly used instead of hypoxia to mean a decreased oxygen supply in tissues.
Combined effect of two or more factors which is smaller than the solitary effect of any one of those factors. Note: In bioassays, the term may be used when a specified effect is produced by exposure to either of two factors but not by exposure to both together.
antonym agonist Substance which binds to a cell receptor normally responding to a naturally occurring substance and which prevents a response to the natural substance.
antihelminth helminthagogue helminthic vermifuge
n., Substance intended to kill or cause the expulsion of parasitic intestinal worms, such as helminths. adj., Acting to expel or kill parasitic intestinal worms.
Form of pneumoconiosis caused by accumulation of anthracite carbon deposits in the lungs due to inhalation of smoke or coal dust.
Caused by or influenced by human activities. Describing a conversion factor used to calculate a dose or concentration affecting a human that has been derived from data obtained with another species, e.g. the rat.
See sympatholytic
Substance produced by, and obtained from, certain living cells (especially bacteria, yeasts and moulds), or an equivalent synthetic substance, which is biostatic or biocidal at low concentrations to some other form of life, especially pathogenic or noxious organisms.
Protein (immunoglobulin) produced by the immune system in response to exposure to an antigenic molecule and characterized by its specific binding to a site on that molecule (antigenic determinant or epitope).
adj., Preventing transmission of parasympathetic (acetylcholine releasing) nerve impulses. n., Substance which prevents transmission of parasympathetic nerve impulses.
Substance which prevents blood clotting, e.g., warfarin.
Substance capable of specifically counteracting or reducing the effect of a potentially toxic substance in an organism by a relatively specific chemical or pharmacological action.
Substance or a structural part (epitope) of a substance which causes the immune system to produce specific antibody or specific cells and which combines with specific binding sites (epitopes) on the antibody or cells.
Substance that blocks or counteracts the action of histamine.
See anthelmint(h)ic
Substance, structurally similar to a metabolite, which competes with it or replaces it, and so prevents or reduces its normal utilization.
n., Substance inhibiting or preventing the actions of muscarine and muscarine-like agents, e.g., atropine, on the muscarinic acetylcholine receptors. adj., Inhibiting or preventing the actions of muscarine and muscarine-like agents on the muscarinic acetylcholine receptors.
fungicide Substance used to kill a fungus or to inhibit its growth.
n., Substance inhibiting or preventing the actions of nicotine and nicotine-like agents, e.g., suxamethonium chloride, on the nicotinic acetylcholine receptors. adj. Inhibiting or preventing the actions of nicotine and nicotine-like agents on the nicotinic acetylcholine receptors.
Substance which relieves or reduces fever.
Substance used as an additive to a pesticide formulation in order to reduce the resistance of insects to the pesticide, e.g., an antimetabolite that inhibits metabolic inactivation of the pesticide.
Serum containing antibodies to a particular antigen either because of immunization or after an infectious disease. Note: Usually the antibodies are polyclonal.
See virucide
Loss or impairment of the power of speech or writing, or of the ability to understand written or spoken language or signs, due to a brain injury or disease.
Substance intended to kill aphids.
Common name for a harmful plant parasite in the family Aphididae, some species of which are vectors of plant virus diseases.
Lack of development of an organ or tissue, or of the cellular products from an organ or tissue.
- apopto-sis n., tic
Active process of programmed cell death, requiring metabolic energy, often characterized by fragmentation of DNA, and cell deletion without associated inflammation.
See necrosis
Substance intended to kill trees and shrubs.
Widespread origin of emissions.
Area between a curve and the abscissa (horizontal axis), i. e., the area underneath the graph of a function: often, the area under the tissue (plasma) concentration curve of a substance expressed as a function of time.
Area between a curve and the abscissa (horizontal axis) in a plot of (concentration x time) versus time.
argyrosis Pathological condition characterized by grey-bluish or black pigmentation of tissues (such as skin, retina, mucous membranes, internal organs) caused by the accumulation of metallic silver, due to reduction of a silver compound which has entered the organism during (prolonged) administration or exposure.
Any variation from the normal rhythm of the heartbeat.
Chronic arsenical poisoning.
Observation, effect, or result which is inaccurate because it is produced by the methodology used in scientific investigation or by experimental error
Hardening and thickening of the walls of the arteries.
Pain in a joint.
Chronic inflammation of a joint, usually accompanied by pain and often by changes in structure.
arthrosis Disease of a joint.
Joint or articulation.
Form of pneumoconiosis caused by inhalation of asbestos fibers.
Substance intended to kill roundworms (Ascaridae).
Condition resulting from insufficient intake of oxygen: symptoms include breathing difficulty, impairment of senses, and, in extreme, convulsions, unconsciousness and death.
Substance that blocks the transport or use of oxygen by living organisms. Note: Examples include both physical (nitrogen gas) and chemical (carbon monoxide) asphyxiants.
Process of quantitative or qualitative analysis of a component of a sample. Results of a quantitative or qualitative analysis of a component of a sample.
Uptake and incorporation of substances by a living organism.
Weakness; lack or loss of strength.
Chronic respiratory disease characterized by bronchoconstriction, excessive mucus secretion and edema of the pulmonary alveoli, resulting in difficulty in breathing out, wheezing, and cough.
Adj. Causing contraction, usually locally after topical application. N. Substance causing cells to shrink, thus causing tissue contraction or stoppage of secretions and discharges; such substances may be applied to skin to harden and protect it.
Unsteady or irregular manner of walking or movement caused by loss or failure of muscular co-ordination.
Pathological condition in which there is thickening, hardening, and loss of elasticity of the walls of blood vessels, characterized by a variable combination of changes of the innermost layer consisting of local accumulation of lipids, complex carbohydrates, blood and blood components, fibrous tissue and calcium deposits. In addition, the outer layer becomes thickened and there is fatty degeneration of the middle layer.
Wasting away of the body or of an organ or tissue, involving a decrease in size and (or) numbers of cells.
Regulation of gene expression in bacteria by premature termination of transcription of a biosynthetic operon.
Substance which attracts animals. Some attractants fulfill natural biological functions such as mating or predation: others may be used to attract animals for monitoring or for control. See also pheromone
Part of a risk that is identified as due to exposure to a defined substance.
Pathological condition resulting when an organism produces antibodies or specific cells which bind to constituents of its own tissues (autoantigens) and cause tissue injury: examples of such disease may include rheumatoid arthritis, myasthenia gravis, systemic lupus erythematosus, and scleroderma.
See autoxidation
Membrane-bound body (secondary lysosome) in which parts of the cell are digested.
necropsy Post-mortem examination of the organs and body tissue to determine cause of death or pathological condition.
Any chromosome other than a sex chromosome.
Reaction with dioxygen at moderate temperatures.
Apparently spontaneous, usually slow reaction of foodstuff components with dioxygen in an aerobic environment at moderate temperatures.
Organism unable to synthesize an organic molecule which is required for its growth: when the compound is given to the organism with the other nutrients it requires, growth of the organism may occur.
Inability of a micro-organism to synthesize a particular organic compound required for its growth.
Substance intended to kill birds.
See germ-free animal
Absence of live motile spermatozoa in semen. Failure to form live spermatozoa.
Process which reverses the effect of a mutation which had inactivated a gene; thus it restores the wild phenotype.
DNA vector into which large DNA fragments can be inserted and cloned in a bacterial host.
Substance intended to kill bacteria.
Lung disease caused by the inhalation of dust from sugar-cane residues.
- basal lamina, pl -ae
Triple-layered structure on which epithelium sits: it consists of an electron dense layer (lamina densa) between two electron transparent layers (lamina lucida). The lamina densa is composed of type IV collagen and the lamina lucida contains the glycoprotein laminin.
Linking of the complementary pair of polynucleotide chains of nucleic acids by means of hydrogen bonds between complementary purine and pyrimidine bases, adenine with thymine or uracil, cytosine with guanine.
Specialized layers of extra-cellular matrix (basal laminae) that separate epithelial tissue from underlying connective tissue: cancer cells must break through the basement membrane in order to migrate to other parts of the body and form metastases.
Equation expressing the build up and decay in concentration of a substance (usually in plasma) based on first order uptake and elimination in a one compartment model, having the form C = (ƒDκa-V(κa - κe(exp(-κet) - exp(-κat where C is the concentration and D the dose of the substance, ƒ the fraction absorbed, and V the volume of distribution. κa and κe) are the first order rate constants of uptake and elimination, respectively, and t is time.
See B lymphocyte
Statistically calculated lower 95% confidence limit on the concentration that produces a defined response (called the benchmark response or BMR, usually 5 % or 10 %) for an adverse effect compared to background, often defined as 0 % or 5%.
Statistically calculated lower 95 % confidence limit on the dose that produces a defined response (called the benchmark response or BMR, usually 5 % or 10 %) of an adverse effect compared to background, often defined as 0 % or 5 %.
Biological monitoring guidance value set at the 90th percentile of available biological monitoring results collected from a representative sample of workplaces with good occupational hygiene practices.
Response, expressed as an excess of background, at which a benchmark dose or benchmark concentration is set.
Advantage to or improvement in condition of an individual or a population.
antonym (malignant)
Of a disease, producing no persisting harmful effects. Tumor which does not invade other tissues (see metastasis), having lost growth control but not positional control. Note: Such a tumor is not carcinogenic but may cause mechanical damage to adjacent tissues.
berylliosis Serious and usually permanent lung damage resulting from chronic inhalation of beryllium.
Deviation of results or inferences from the truth, or processes leading to such deviation. Any trend in the collection, analysis, interpretation, publication, or review of data which can lead to conclusions which are systematically different from the truth.
antonym random sample Any sample which is not a random sample.
Orange-yellow pigment, a breakdown product of heme-containing proteins (hemoglobin, myoglobin, cytochromes), which circulates in the blood plasma bound to albumin or as water soluble glucuronide conjugates, and is excreted in the bile by the liver.
Potential for a substance to come in contact with a living organism and then interact with it. This may lead to absorption. Note: A substance trapped inside an insoluble particle is not bio-accessible although substances on the surface of the same particle are accessible and may also be bio-available. Bio-accessibility, like bio-availability, is a function of both chemical speciation and biological properties. Even surface-bound substances may not be accessible to organisms which require the substances to be in solution.
Able to come in contact with a living organism and interact with it. See bio-accessibility
Progressive increase in the amount of a substance in an organism or part of an organism which occurs because the rate of intake exceeds the organism's ability to remove the substance from the body. Note: Bio-accumulation often correlates with lipophilicity. See also bioconcentration, biomagnification
Ability of living organisms to concentrate a substance obtained either directly from the environment or indirectly through its food.
Metabolic conversion of a xenobiotic to a more toxic derivative or one which has more of an effect on living organisms.
Procedure for estimating the concentration or biological activity of a substance by measuring its effect on a living system compared to a standard system.
- bio-availability (general)
biological availability physiological availability Extent of absorption of a substance by a living organism compared to a standard system.
Ratio of the systemic exposure from extravascular (ev) exposure to that following intravenous (iv) exposure as described by the equation:
F = AevDiv - Biv Dev
where F (fraction of dose absorbed) is a measure of the bioavailability, A and B are the areas under the (plasma) concentration time curve following extravascular and intravenous administration respectively, and Dev and Div are the administered extravascular and intravenous doses.
Able to be absorbed by living organisms. See bio-availability
Reaction or series of reactions, usually enzyme-catalysed, associated with a specific physiological event in a living organism.
Amount concentration of oxygen taken up through the respiratory activity of micro-organisms growing on organic compounds present when incubated at a specified temperature (usually 20° C) for a fixed period (usually 5 days). It is regarded as a measure of that organic pollution of water which can be degraded biologically but includes the oxidation of inorganic material such as sulfide and iron(II). The empirical test used in the laboratory to determine BOD also measures the oxygen used to oxidize reduced forms of nitrogen unless their oxidation is prevented by an inhibitor such as allyl thiourea.
- biocid-e n., -al
Substance intended to kill living organisms.
Process leading to a higher concentration of a substance in an organism than in environmental media to which it is exposed. See bioaccumulation
Measure of the tendency for a substance in water to accumulate in organisms, especially fish. Note 1. The equilibrium concentration of a substance in fish can be estimated by multiplying its concentration in the surrounding water by its bioconcentration factor in fish. Note 2. This parameter is an important determinant for human intake of aquatic food by the ingestion route.
See conjugate
Breakdown of a substance catalysed by enzymes in vitro or in vivo. This may be characterized for purposes of hazard assessment as:
Primary. Alteration of the chemical structure of a substance resulting in loss of a specific property of that substance. Environmentally acceptable. Biodegradation to such an extent as to remove undesirable properties of the compound. This often corresponds to primary biodegradation but it depends on the circumstances under which the products are discharged into the environment. Ultimate. Complete breakdown of a compound to either fully oxidized or reduced simple molecules (such as carbon dioxide-methane, nitrate-ammonium, and water. It should be noted that the products of biodegradation can be more harmful than the substance degraded.
Removal, usually from the aqueous phase, of a test substance in the presence of living organisms by biological processes supplemented by physico-chemical reactions.
- bio-equivalen-ce n., -t
Relationship between two preparations of the same drug in the same dosage form that have a similar bioavailability.
Metabolic conversion of a xenobiotic to a less toxic derivative.
Discipline encompassing the development and utilization of computational facilities to store, analyse and interpret biological data.
Science of the movements involved in the distribution of substances.
See acclimatization, biological
See bioavailability
Complete circulatory process through which a substance passes in the biosphere. It may involve transport through the various media (air, water, soil), followed by environmental transformation, and carriage through various ecosystems.
Continuous or repeated measurement of early biological effects of exposure to a substance to evaluate ambient exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and biological effects.
Guidance values recommended by ACGIH for assessing biological monitoring results.
For a substance the time required for the amount of that substance in a biological system to be reduced to one half of its value by biological processes, when the rate of removal is approximately exponential.
- biological half time, t1-2
Species or group of species which is representative and typical for a specific status of an ecosystem, which appears frequently enough to serve for monitoring and whose population shows a sensitive response to changes, e.g., the appearance of a toxicant in an ecosystem.
See biomarker
biological assessment of exposure biomonitoring Continuous or repeated measurement of any naturally occurring or synthetic chemical, including potentially toxic substances or their metabolites or biochemical effects in tissues, secreta, excreta, expired air or any combination of these in order to evaluate occupational or environmental exposure and health risk by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and resultant adverse health effects.
biological biopreparation Compound derived from living organisms and their products for use in medicine or as a pesticide etc.
Organ, tissue (including blood), secretion or excretion product taken from an organism as a sample reflecting the state of the whole organism. Organism taken as a sample reflecting the state of a population or their environment.
Military operations using any organism (bacteria, virus or other disease-causing organism) or toxin found in nature, to kill, injure or incapacitate human beings, animals, or plants.
ecological magnification Sequence of processes in an ecosystem by which higher concentrations are attained in organisms at higher trophic levels (at higher levels in the food web); at its simplest, a process leading to a higher concentration of a substance in an organism than in its food.
Indicator signaling an event or condition in a biological system or sample and giving a measure of exposure, effect, or susceptibility. Note: Such an indicator may be a measurable chemical, biochemical, physiological, behavioral or other alteration within an organism.
effect biomarker Biomarker that, depending upon the magnitude, can be recognized as associated with an established or possible health impairment or disease.
exposure biomarker Biomarker that relates exposure to a xenobiotic to the levels of the substance or its metabolite, or of the product of an interaction between the substance and some target molecule or cell that can be measured in a compartment within an organism.
susceptibility biomarker Biomarker of an inherent or acquired ability of an organism to respond to exposure to a specific substance.
Total amount of biotic material, usually expressed per unit surface area or volume, in a medium such as water. Material produced by the growth of micro-organisms, plants or animals.
Complete conversion of organic substances to inorganic derivatives by living organisms, especially micro-organisms.
Substance that is synthesized by and occurs naturally in living organisms.
Biological agent with pesticidal activity, e.g., the bacterium Bacillus thuringiensis when used to kill insects. After
Excision of a small piece of living tissue for microscopic or biochemical examination; usually performed to establish a diagnosis.
Portion of the planet earth which supports and includes life.
Adjective applied to a substance which arrests the growth or multiplication of living organisms.
All living organisms as a totality.
bioconversion Chemical conversion of a substance that is mediated by living organisms or enzyme preparations derived there from.
British anti-Lewisite dimercaprol 2,3-dimercaptopropan-1-ol Metal chelator which has been used in the treatment of arsenic, antimony, gold, mercury and lead poisoning.
Mammalian embryo at the stage at which it is implanted into the wall of the uterus.
Physiological interface between brain tissues and circulating blood created by a mechanism that alters the permeability of brain capillaries, so that some substances are prevented from entering brain tissue, while other substances are allowed to enter freely. After
Physiological interface between maternal and fetal blood circulations that filters out some substances which could harm the fetus while favoring the passage of others such as nutrients: many fat soluble substances such as alcohol are not filtered out and several types of virus can also cross this barrier. Note: The effectiveness of the interface as a barrier varies with species and different forms of placentation.
Physiological interface between the blood supply and the spermatozoa of the seminiferous tubules. Note: This interface consists of specific junctional complexes between Sertoli cells. After
B cell Type of lymphocyte which synthesizes and secretes antibodies in response to the presence of a foreign substance or one identified by it as foreign. The protective effect can be mediated to a certain extent by the antibody alone (contrast T lymphocyte).
Total amount of a substance present in an organism at a given time.
Single dose of a substance, originally a large pill. Dose of a substance administered by a single rapid intravenous injection. Concentrated mass of food ready to be swallowed.
Substance with activity against pests, that is produced naturally within a plant and may act as a defense against predators.
Acute food poisoning caused by botulinum toxin produced in food by the bacterium Clostridium botulinum and characterized by muscle weakness and paralysis, disturbances of vision, swallowing, and speech, and a high mortality rate.
antonym tachy- Prefix meaning slow as in bradycardia or bradypnoea.
antonym tachycardia Abnormal slowness of the heartbeat.
antonym tachypnoea Abnormally slow breathing.
Space within a radius of 0.5 m from a person’s face.
See 2,3-bis(sulfanyl)propan-1-ol
antonym bronchodilation Narrowing of the air passages through the bronchi of the lungs.
antonym bronchoconstriction Expansion of the air passages through the bronchi of the lungs.
Intermittent violent contraction of the air passages of the lungs.
Material which enhances or maintains the cleaning efficiency of a surfactant, in a detergent, principally by inactivating water hardness; complex phosphates (especially sodium tripolyphosphate, i.e. pentasodium triphosphate), sodium carbonate, and sodium silicate are the builders most commonly used.
Pneumoconiosis caused by inhalation of dust and associated microbial contaminants and observed in cotton, flax, and hemp workers.
Liability of members of the general public to come in contact with substances arising from operations or processes carried out by other individuals in their vicinity.
Imagined perception of vile odors, including coprosmia (smelling feces) and necrosmia (the smell of death).
Form of mineralization in which organic tissue becomes hardened by deposition of calcium salts within its substance.
Operation that, under specified conditions, in a first step establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication.
Disease resulting from the development of a malignant tumor.
carboxyhemoglobin Compound which is formed between carbon monoxide and hemoglobin in the blood of animals and humans and which is incapable of transporting oxygen.
- carcinogen n., -ic
Agent (chemical, physical or biological) which is capable of increasing the incidence of malignant neoplasms, thus causing cancer. Note: Annex 3 describes the classification systems for carcinogens.
- carcinogen-esis n., -etic
Induction, by chemical, physical, or biological agents, of malignant neoplasms and thus cancer.
Process of induction of malignant neoplasms, and thus cancer, by chemical, physical or biological agents.
Long term (chronic) test designed to detect any possible carcinogenic effect of a test substance.
epithelioma Malignant tumor of an epithelial cell.
Chemically harmful to the cells of the heart.
Substance in appreciable amount which, when associated with a trace of a specified substance, will carry the trace with it through a chemical or physical process. Person who is heterozygous, that is carries only one allele, for a recessive genetic character leading to disease, and hence does not, under most circumstances, display the disease phenotype but can pass it on to the next generation.
Gas, liquid, or solid substance (often in particulate form) used to absorb, adsorb, dilute or suspend a substance to facilitate its transfer from one medium to another.
carrier prodrug Compound that contains a temporary linkage between a given active substance and a transient carrier group, the latter producing improved physicochemical or pharmacokinetic properties and easily removable in vivo.
Protein to which a specific ligand or hapten is conjugated Unlabeled protein introduced into an assay at relatively high concentrations which distributes in a fractionation process in the same manner as labeled protein analyte, present in very low concentrations. Protein added to prevent nonspecific interaction of reagents with surfaces, sample components, and each other. Protein found in cell membranes which facilitates transport of a ligand across the membrane.
Substance which binds to another substance and transfers it from one site to another.
Transfer in farming and agricultural processing of a component from one system such as soil or feed to another system such as a plant, animal or human being: carry-over is expressed as the concentration of the component in the second system divided by its concentration in the first. Process in analytical studies by which materials are carried into a reaction mixture in which they do not belong. Persistence of a substance in soil, e.g., a pesticide, such that injury may occur subsequently to a new crop. Persistence of a test substance in participants undergoing a cross-over clinical trial study, in which each participant randomly receives the placebo and test substance with an intervening washout period.
Variant of the case control study in which the controls are drawn from the same cohort as the cases but are identified before the cases develop; some of the controls may later become cases.
case comparison study case compeer study case history study case referent study retrospective study Study which starts with the identification of persons with the disease (or other outcome variable) of interest, and a suitable control (comparison, reference) group of persons without the disease. The relationship of an attribute to the disease is examined by comparing the diseased and non-diseased with regard to how frequently the attribute is present or, if quantitative, the levels of the attribute, in the two groups.
antonym anabolism
Reactions involving the oxidation of organic substrates to provide chemically available energy (for example ATP) and to generate metabolic intermediates. Generally, process of breakdown of complex molecules into simpler ones, often providing biologically available energy.
Schizophrenia marked by excessive, and sometimes violent, motor activity and excitement, or by generalized inhibition.
See laxative
Airborne concentration of a potentially toxic substance which should never be exceeded in a worker's breathing zone.
Regulated biochemical steps that cells go through involving DNA replication and cell division, usually depicted as a sequential cyclical series of events.
Defined unique population of cells obtained by culture from a primary source through numerous generations. See also transformed cell line
State in which an individual reacts with allergic effects caused by the reaction of antigen-specific T-lymphocytes following exposure to a certain substance (allergen) after having been exposed previously to the same substance or chemical group.
Immune response mediated by antigen-specific T-lymphocytes.
Rapid increase in cell number.
Cells having specific properties or markers derived from a primary culture or cell line.
Sample observations for which the complete distribution is not known: for example, a cohort study in which some persons cannot be followed to the predetermined end of the study (“right-censored data”) or environmental assay data in which some results are less than the sample detection limit (“left-censored data”).
Reference material, accompanied by documentation issued by an authoritative body and referring to valid procedures used to obtain a specified property value with uncertainty and traceability. Example: human serum with assigned quantity value for the concentration of cholesterol and associated measurement uncertainty stated in an accompanying certificate, used as calibrator or measurement trueness control material.
Sequence of responsibility for a substance from the manufacturer to the distributor, to the user, or to the person(s) ultimately responsible for waste disposal. This term is also used in controlled transmission of samples from collection to analysis, especially of samples of materials used for medico-legal or forensic purposes.
Treatment with a chelating agent to enhance the elimination or reduce the toxicity of a metal ion.
Sensations that arise when chemical compounds activate receptor mechanisms for other effectors, such as light, pain, pressure, and heat, in the eye, skin, nose, mouth and throat; e.g., the burning feeling from chili pepper, the cooling from the menthol in mouthwash, and the stinging feeling of carbonation.
See toxic substance
Change from one chemical species to another.
See toxic substance
Measure of the amount of oxygen, divided by the volume of the system, required to oxidize the organic (and inorganic) matter in wastewater using a chemically oxidizing agent. In practice, it is usually expressed in milligrams O2 per litre.
Practical certainty that there will be no exposure of organisms to toxic amounts of any substance or group of substances: this implies attaining an acceptably low risk of exposure to potentially toxic substances.
Specific form of an element defined as to isotopic composition, electronic or oxidation state, and (or) complex or molecular structure.
Military operations using the toxic properties of chemical agents to kill, injure or incapacitate human beings, animals, or plants.
Irrational fear of chemicals.
Chemically induced swelling around the eye caused by edema of the conjunctiva.
Substance used to sterilize mites, insects, rodents or other animals.
Acne-like eruption caused by exposure to certain chlorinated organic substances such as polychlorinated biphenyls or 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetrachlorooxanthrene) and other polychlorinated dibenzo dioxins and furans.
Substance which inhibits the action of acetylcholinesterase (EC 3.1.1.7) and related enzymes which catalyse the hydrolysis of choline esters: such a substance causes hyperactivity in parasympathetic nerves. Note: Examples include organophosphate and carbamate pesticides.
Either of two filaments joined at the centromere into which a chromosome divides as it duplicates itself during cell division.
Stainable complex of DNA and proteins present in the nucleus of a eukaryotic cell.
Abnormality of chromosome number or structure.
Self-replicating structure consisting of DNA complexed with various proteins and involved in the storage and transmission of genetic information; the physical structure that contains the genes.
antonym acute Long-term, (in relation to exposure or effect).
In experimental toxicology, chronic refers to mammalian studies lasting considerably more than 90 days or to studies occupying a large part of the lifetime of an organism. In clinical medicine, long established or long lasting.
long-term effect antonym acute effect Consequence which develops slowly and (or) has a long-lasting course: may be applied to an effect which develops rapidly and is long lasting.
long-term exposure antonym acute exposure Continued exposure or exposures occurring over an extended period of time, or a significant fraction of the test species' or of the group of individuals', or of the population's life-time.
long-term toxicity antonym acute toxicity
Adverse effects following chronic exposure. Effects which persist over a long period of time whether or not they occur immediately upon exposure or are delayed.
long-term toxicity test antonym acute toxicity test Study in which organisms are observed during the greater part of the life span and in which exposure to the test agent takes place over the whole observation time or a substantial part thereof.
Study of the influence of biological rhythms on the toxicity of substances or of the influence of a toxicant on biological rhythms.
Serious illness caused by eating carnivorous fish such as snappers and barracuda that have become contaminated by toxins produced by the micro-alga, Gambierdiscus toxicus; gastrointestinal symptoms may accompany a wide variety of neurological symptoms including ataxia, vertigo, flaccid paralysis, respiratory arrest, and reversed perception of hot and cold; the neurological symptoms may persist for many years.
nychthemeral Relating to or exhibiting an approximately 24-hour periodicity.
Movement of xenobiotic substances in the environment with air flow, river current, soil, water, etc.
Liver disease defined by histological examination and characterized by increased fibrous tissue, abnormal morphological and physiological changes such as loss of functional liver cells, and increased resistance to blood flow through the liver (portal hypertension). Chronic interstitial inflammation and fibrosis of an organ.
Describing an organ showing cirrhosis.
Agent causing chromosome breakage and (or) consequent gain, loss or rearrangement of pieces of chromosomes.
Formation (or generation) of chromosomal breaks and (or) consequent gain, loss or rearrangement of pieces of chromosomes.
- clearance (general) (co-ci)(ΔV-Δ t)
Product of the concentration co of a component in an output system and the volume flow rate of the output system divided by the concentration ci of this component in the input system. Note: The term ‘mean volume rate’ is recommended for this quantity.
Volume of blood or plasma or mass of an organ effectively cleared of a substance by elimination (metabolism and excretion) divided by time of elimination. Note : Total clearance is the sum of the clearances of each eliminating organ or tissue for that component (in pulmonary toxicology) Volume or mass of lung cleared divided by time of elimination; used qualitatively to describe removal of any inhaled substance which deposits on the lining surface of the lung. (in renal toxicology) Quantification of the removal of a substance by the kidneys by the processes of filtration and secretion; clearance is calculated by relating the rate of renal excretion to the plasma concentration.
Splitting of a molecule into smaller molecular entities.
Scientific study involving research, education, prevention and treatment of diseases caused by substances such as drugs and toxins. Note: Often refers specifically to the application of toxicological principles to the treatment of human poisoning.
- clon-e n., -al
Population of genetically identical cells or organisms having a common ancestor. To produce such a population., Recombinant DNA molecules all carrying the same inserted sequence.
Pertaining to alternate muscular contraction and relaxation in rapid succession.
Small circle of DNA (e.g., a plasmid) or modified bacteriophage (bacterial virus) that can carry a segment of foreign DNA into an appropriate host organism (e.g. a bacterial, yeast or mammalian cell). After
A method of sampling in which the population is divided into aggregates (or clusters) of items bound together in a certain manner. A sample of these clusters is taken at random and all the items which constitute them are included in the sample. A sampling method in which each unit selected is a group of persons (all persons in a city block, a family, etc.) rather than an individual.
See agonist
Chemical, physical or biological factor which intensifies the effect of a carcinogen.
Collection of internationally adopted food standards drawn up by the Codex Alimentarius Commission, the principal body implementing the joint FAO-WHO Food Standards Programme.
Component of the population born during a particular period and identified by period of birth so that its characteristics (such as causes of death and numbers still living) can be ascertained as it enters successive time and age periods. The term “cohort” has broadened to describe any designated group of persons followed or traced over a period of time, as in the term cohort study (prospective study).
Tabulation and analysis of morbidity or mortality rates in relationship to the ages of a specific group of people (cohort), identified by their birth period, and followed as they pass through different ages during part or all of their life span. In certain circumstances such as studies of migrant populations, cohort analysis may be performed according to duration of residence in a country rather than year of birth, in order to relate health or mortality experience to duration of exposure.
concurrent study follow-up study incidence study longitudinal study prospective study Analytic study of epidemiological study in which subsets of a defined population can be identified who are, have been, or in the future may be exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease or other outcome. The main feature of the method is observation of a large population for a prolonged period (years), with comparison of incidence rates of the given disease in groups that differ in exposure levels.
Simultaneous or successive effect of two or more poisons on the organism by the same route of exposure.
Process by which a normally non-biodegradable substance is biodegraded only in the presence of an additional carbon source. See also metabolism
Means of measuring DNA damage, particularly DNA strand breaks. A cell is embedded in agar and exposed to a DNA-damaging agent. The cell is then permeabilized with a detergent and an electric field is applied. If the cell's genomic DNA has been broken into small fragments, these fragments move out of the cell by electrophoresis and form a streak or “tail” leading away from the cell which looks like a comet.
See control group
Study of the relationship of genome structure and function across different biological species. After
Conceptualized part of the body (organs, tissues, cells, or fluids) considered as an independent system for purposes of modeling and assessment of distribution and clearance of a substance.
Mathematical process leading to a model of transport of a substance in terms of compartments and rate constants, usually taking the form C = Ae-αt + Be - βt… where each exponential term represents one compartment. C is the substance concentration; A, B, … are proportionality constants; α, β, … are rate constants; and t is time.
Separate into compartments.
pseudo-adaptation Adaptation of an organism to changing conditions of the environment (especially chemical) is accompanied by the emergence of stresses in biochemical systems which exceed the limits of normal (homeostatic) mechanisms. Compensation is a temporary concealed pathology which later on can be manifested in the form of explicit pathological changes (decompensation).
In the context of European Community Council Directive 79-831-EEC, the Sixth Amendment to the European Community Council Directive 67-548-EEC relating to the Classification, Packaging and Labeling of Dangerous Substances, official government organization or group receiving and evaluating notifications of new substances.
Culture of bacteria (or yeast) treated in such a way that their ability to take up DNA molecules without transduction or conjugation has been enhanced.
DNA generated from an expressed messenger RNA through a process known as reverse transcription.
Complete breakdown of a complex organic compound to carbon dioxide, water, oxides and oxidative inorganic products such as nitrate or sulfate.
Simultaneous or successive effect made on an organism by poisons entering from different media, from air, from water, from food or through the skin.
Application of mathematical and computer models to predict adverse effects and to better understand the mechanism(s) through which a given chemical causes harm.
Any one of a group of three quantities characterizing the composition of a mixture and defined as one of mass, amount of substance (chemical amount) or number divided by volume, giving, respectively, mass, amount (of substance) or number concentration. Short form for amount (of substance) concentration (substance concentration in clinical chemistry).
exposure-effect curve Graph of the relation between exposure concentration and the magnitude of the resultant biological change.
exposure-effect relationship
Association between exposure concentration and the resultant magnitude of the continuously graded change produced, either in an individual or in a population.
exposure-response curve Graph of the relation between exposure concentration and the proportion of individuals in a population responding with a defined effect.
exposure-response relationship Association between exposure concentration and the incidence of a defined effect in an exposed population.
- concord-ance n., -ant
Pairs or groups of individuals of identical phenotype. Note: In twin studies, this is a condition in which both twins exhibit or fail to exhibit a trait under investigation.
See cohort study
Measurement and its criterion refer to the same point in time: an example would be a visual inspection of a wound for evidence of infection validated against bacteriological examination of a specimen taken at the same time.
Situation in which the effects of two processes are not distinguishable from one another: the distortion of the apparent effect of an exposure on risk brought about by the association of other factors which can influence the outcome. Relationship between the effects of two or more causal factors as observed in a set of data, such that it is not logically possible to separate the contribution which any single causal factor has made to an effect. Situation in which a measure of the effect of an exposure on risk is distorted because of the association of exposure with other factor(s) which influence the outcome under study.
confounder Changing factor that can cause or prevent the outcome of interest, is not an intermediate variable, and is associated with the factor under investigation.
One of two or more substances related to each other by origin, structure, or function.
Trait, condition or disorder that exists in an organism from birth. After
Chemical species produced in living organisms by covalently linking two chemical moieties from different sources. Example; A conjugate of a xenobiotic with some group such as glutathione, sulfate or glucuronic acid, to make it soluble in water or compartmentalized within the cell. See also phase II reaction Material produced by attaching two or more substances together, e.g. a conjugate of an antibody with a fluorochrome, or an enzyme.
Mucous membrane which covers the eyeball and lines the under-surface of the eyelid.
Inflammation of the conjunctiva.
Assessment of risk which assumes the worst possible case scenario and therefore gives the highest possible value for risk: risk management decisions based on this value will maximize safety.
Extent to which a measurement corresponds to theoretical concepts (constructs) concerning the phenomenon under study; for example, if on theoretical grounds, the phenomenon should change with age, a measurement with construct validity would reflect such a change.
Inflammatory condition of the skin resulting from dermal exposure to an allergen (sensitizer) or an irritating (corrosive, defatting) substance.
Chemical which injures the target organism through physical contact and skin absorption rather than through ingestion or inhalation.
Pesticide (herbicide) that causes injury to only the plant tissue to which it is applied or which is not appreciably translocated within plants.
Process by which possible release, discharge or spill of a toxic substance during normal use or after an accident is prevented by appropriate action.
Minor impurity present in a substance. Extraneous material inadvertently added to a sample prior to or during chemical or biological analysis In some contexts, as in relation to gas cleaning equipment, used as a synonym for “pollutant”, especially on a small scale. Unintended component in food that may pose a hazard to the consumer.
Extent to which the measurement incorporates the domain of the phenomenon under study; for example, a measurement of functional health status should embrace activities of daily living, occupational, family, and social functioning, etc.
antonym indication Any condition which renders some particular line of treatment improper or undesirable.
comparison group Selected subjects of study, identified as a rule before a study is done, which comprises humans, animals, or other species who do not have the disease, intervention, procedure or whatever is being studied, but in all other respects are as nearly identical to the test group as possible.
Control (individual or group or case) selected to be similar to a study individual or group, or case, in specific characteristics: some commonly used matching variables are age, sex, race and socio-economic status.
Predominantly vertical motion of air or of water, induced by the expansion of the air or of water heated by the earth’s surface, or by human activity, and its resulting buoyancy.
See chemical conversion, biotransformation
Quality rating, based on standard evaluation criteria established by the US Office of Pesticide Programs regulatory agencies, given to toxicological studies after submission by registrants.
Causing a surface-destructive effect on contact; in toxicology, this normally means causing visible destruction of the skin, eyes, or the lining of the respiratory tract or the gastrointestinal tract.
Mean of the diameters of all particles in a population. See also mass mean diameter
Calculated diameter in a population of particles in a gas or liquid phase above which there are as many particles with larger diameters as there are particles below it with smaller diameters.
See also mass mean diameter
See crepitations
crackles râles Abnormal respiratory sounds heard on auscultation of the chest, produced by passage of air through passages which contain secretion or exudate or which are constricted by spasm or a thickening of their walls; also referred to as rhonchi. Note: Auscultation is the process of listening for sounds within the body by ear unassisted or using a stethoscope.
- criteri-on (pl. -a
Validated set of data used as a basis for judgment.
Extent to which the measurement correlates with an external criterion of the phenomenon under study.
Concentration of a substance at and above which adverse functional changes, reversible or irreversible, occur in a cell or an organ.
Dose of a substance at and above which adverse functional changes, reversible or irreversible, occur in a cell or an organ.
For deterministic effects, the first adverse effect which appears when the threshold (critical) concentration or dose is reached in the critical organ: adverse effects with no defined threshold concentration are regarded as critical.
Toxic effect used by the USEPA as the basis for a reference dose.
Part of a target population most in need of protection because it is most susceptible to a given toxicant.
Organ which first attains the critical concentration of a substance and exhibits the critical effect under specified circumstances of exposure and for a given population. After
Mean concentration of a substance in the critical organ at the time the substance reaches its critical concentration in the most sensitive type of cell in the organ.
Stage of development of an organism, e.g., organogenesis in the fetus, that is of particular importance in the life cycle if the normal full development of some anatomical, physiological, metabolic, or psychological structure or function is to be attained.
pivotal study Investigation yielding the no-observed-adverse-effect-level that is used by the USEPA as the basis of the reference dose.
See odds ratio
disease frequency survey prevalence study Study that examines the relationship between diseases (or other health-related characteristics) and other variables of interest as they exist in a defined population at one particular time. Note: Disease prevalence rather than incidence is normally recorded in a cross-sectional study and the temporal sequence of cause and effect cannot necessarily be determined.
Proportion of a defined group that die within the specified time period (e.g., month, year). Note: It may refer to all deaths or to deaths from a specific cause or specific causes.
Overall change which occurs after repeated doses of a substance or radiation.
incidence proportion Number or proportion of individuals in a group who experience the onset of a health-related event during a specified time interval. Note: This interval is generally the same for all members of the group, but, as in lifetime incidence, it may vary from person to person without reference to age.
Proportion of the cumulative incidence to the total population.
Value obtained by dividing the cumulative incidence rate in the exposed population by the cumulative incidence rate in the unexposed population.
Estimate of the total administered amount of a substance which is associated with the death of half a population of animals when the substance is administered repeatedly in doses which are generally fractions of the median lethal dose.
Probability of a common harmful effect associated with concurrent exposure by all relevant pathways and routes of exposure to a group of substances that share a common chemical mechanism of toxicity. Total probability of a harmful effect over time.
dermal Pertaining to the skin.
Compounds able to produce cyanide. Examples: Cyanogenic glycosides such as amygdalin in peach and apricot stones.
Bluish coloration, especially of the skin and mucous membranes and fingernail beds, caused by abnormally large amounts of reduced hemoglobin in the blood vessels as a result of deficient oxygenation.
Toxin produced by Cyanobacteria, sometimes called bluegreen algae. Note: Examples are microcystin and cylindrospermin.
Substances, such as aspirin and ibuprofen, which block the activity of cyclo-oxygenase (COX), an enzyme that is responsible for the formation of prostanoids (including prostaglandins, prostacyclin and thromboxane); inhibition of COX can provide relief from inflammation and pain.
Conjugated proteins containing heme as the prosthetic group and associated with electron transport and with redox processes.
Inactive derivative of cytochrome P-450 found in microsomal (see microsome) preparations.
Obsolete term for cytochrome P-450 I, A1, and A2, one of the major families of the cytochromes P-450 hemoproteins. Note: During the mono-oxygenation of certain substances, often a detoxification process, these iso-enzymes may produce intermediates which can initiate mutations, cancer, immunotoxic reactions and adverse effects.
Member of a superfamily of heme-containing mono-oxygenases involved in xenobiotic metabolism, cholesterol biosynthesis, and steroidogenesis, in eukaryotic organisms found mainly in the endoplasmic reticulum and inner mitochondrial membrane of cells. ‘P-450’ refers to the observation that a solution of this enzyme exposed to carbon monoxide strongly absorbs light at a wavelength of 450nm compared with the unexposed solution, (a difference spectrum caused by a thiolate in the axial position of the heme opposite to the carbon monoxide ligand). After
Branch of genetics which correlates the structure and number of chromosomes as seen in isolated cells with variation in genotype and phenotype.
Any of a group of soluble proteins that are released by a cell causing a change in function or development of the same cell (autocrine), an adjacent cell (paracrine), or a distant cell (endocrine); cytokines are involved in reproduction, growth and development, normal homeostatic regulation, response to injury and repair, blood clotting, and host resistance (immunity and tolerance).
Fundamental substance or matrix of the cell (within the plasma membrane) which surrounds the nucleus, endoplasmic reticulum, mitochondria and other organelles.
Causing damage to cell structure or function.
Estimate of the proportion of a population which dies during a specified period. The numerator is the number of persons dying during the period; the denominator is the size of the population, usually estimated as the mid-year population. The death rate in a population is generally calculated by the formula:
10n (Number of deaths during a specified period) - (Number of persons at risk of dying during the period) where n is usually either 3 or 5 giving rates per 1 000 or per 100 000 people in the population studied.
Note 1: This rate is an estimate of the person-time death rate, the death rate per 10n person-years: usually n = 3. If the rate is low, it is also a good estimate of the cumulative death rate. Note 2: This term is sometimes described as the crude death rate
Unit of perceived air quality: air on mountains or the sea has a decipol = 0.01; city air with moderate air pollution has a decipol = 0.05- 0.03; acceptable indoor air quality has decipol = 1.4 (for 80% satisfaction).
Explicit pathophysiological changes following compensation for adverse effects.
Process of rendering harmless (by neutralization, elimination, removal etc.) a potentially toxic substance in the natural environment, laboratory areas, the workplace, other indoor areas, clothes, food, water, sewage etc.
Substance used for removal of leaves by its toxic action on living plants.
Enzyme which catalyses oxidation of compounds by removing hydrogen.
latent effect Consequence occurring after a latent period following the end of exposure to a toxic substance or other harmful environmental factor.
See risk de minimis
Addition of methanol, acetone or other suitable chemical(s) to alcohol to make it unfit for drinking. Change in molecular structure of proteins so that they cannot function normally, often caused by splitting of hydrogen bonds following exposure to reactive substances or heat.
Reduction of nitrates to nitrites, nitrogen oxides or dinitrogen (N2) catalysed by facultative aerobic soil bacteria under anaerobic conditions.
Tooth enamel malformations due to excessive fluoride exposure during dental development.
Constituent of chromosomes which stores the hereditary information of an organism in the form of a sequence of purine and pyrimidine bases: this information relates to the synthesis of proteins and hence it is a determinant of all physical and functional activities of the cell, and consequently of the whole organism.
Replication of DNA sequences ligated into a suitable vector in an appropriate host organism. See deoxyribonucleic acid
Restoration of the molecular structure of DNA after it has been damaged by a chemical or physical agent: this may involve direct DNA damage reversal, base excision repair, nucleotide excision repair, mismatch repair, or double-strand break repair
Determining the order of base pairs in a DNA molecule. See deoxyribonucleic acid After
A psychic craving for a drug or other substance which may or may not be accompanied by a physical dependency. Reliance on a drug or other substance to maintain health.
Substance causing loss of hair.
Process by which a substance arrives at a particular organ or tissue site, for example the deposition of particles on the ciliated epithelium of the bronchial airways. Process by which a substance sediments out of the atmosphere or water and settles in a certain place.
cutaneous Pertaining to the skin.
Skin reaction resulting from a single or multiple exposure to a physical or chemical entity at the same site, characterized by the presence of inflammation; it may result in cell death.
Inflammation of the skin: contact dermatitis is due to local exposure and may be caused by irritation, allergy or infection.
Study of the occurrence of disease or other health-related characteristics in populations, including general observations concerning the relationship of disease to basic characteristics such as age, sex, race, occupation, and social class; it may also be concerned with geographic location. The major characteristics in descriptive epidemiology can be classified under the headings: individuals, time and place.
Suppression of sensitivity of an organism to an allergen to which the organism has been exposed previously.
Drying agent. In agriculture, a substance used for drying up plants and facilitating their mechanical harvesting.
Opposite of adsorption; a decrease in the amount of adsorbed substance.
Shedding of an outer layer of skin in scales or shreds.
Term applied to health effects, the severity of which varies with the dose and for which a threshold is believed to exist.
deterministic process Phenomenon committed to a particular outcome determined by fundamental physical principles. See also stochastic effect
detoxication
Process, or processes, of chemical modification which make a toxic molecule less toxic. Treatment of patients suffering from poisoning in such a way as to promote physiological processes which reduce the probability or severity of adverse effects.
Estimated measure of the expected harm or loss associated with an adverse event, usually in a manner chosen to facilitate meaningful addition over different events. It is generally the integrated product of arbitrary values of risk and hazard and is often expressed in terms such as costs in US dollars, loss in expected years of life or loss in productivity, and is needed for numerical exercises such as cost-benefit analysis.
Adverse effects on the developing organism (including structural abnormality, altered growth, or functional deficiency or death) resulting from exposure through conception, gestation (including organogenesis), and postnatally up to the time of sexual maturation.
Profuse perspiration.
sudorific Substance that causes sweating.
diarrheal shellfish poisoning Serious illness which is a consequence of consumption of bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing a group of high molecular weight polyethers such as okadaic acid, dinophysis toxins, pectenotoxins, and yessotoxin; gastroenteritis develops shortly after ingestion and generally lasts 1-2 days.
Spontaneous differential movement of components in a system. Note: In molecular terms, the driving force for diffusion is random thermal motion. In thermodynamic terms, the driving force is a gradient of chemical potential.
Proportionality constant D, relating the flux (flux density) of amount No Entry of entities B, Jn,B, to their concentration gradient Jn= –D grad cB After
2,3-dimercaptopropan-1-ol See 2,3-bis(sulfanyl)propan-1-ol
Chromosome state in which the chromosomes are present in homologous pairs. Note: Normal human somatic (non-reproductive) cells are diploid (they have 46 chromosomes), whereas reproductive cells, with 23 chromosomes, are haploid.
See emission
Maximum amount of a pollutant released from a given source to a specified medium which is acceptable under specified circumstances.
antonym concordance Any difference in a character between individuals due to genetic differences such as may occur in dizygotic twins, or between matched pairs in a case cohort study.
Literally, dis-ease, lack of ease; pathological condition that presents a group of symptoms peculiar to it and which establishes the condition as an abnormal entity different from other normal or pathological body states.
Dilution of a pollutant by spreading in the atmosphere or water due to diffusion or turbulent action.
Natural tendency shown by an individual or group of individuals, including any tendency to acquisition of specific diseases, often due to hereditary factors. Total of the processes of absorption of a chemical into the circulatory systems, distribution throughout the body, biotransformation, and excretion.
Reduction in the amount of a pesticide or other compound which has been applied to plants, soil etc. (used when it is not clear whether this is by mineralization degradation, binding, or leaching).
See area source
Apportionment of a solute between two phases. The term partition or extraction may also be used in this sense where appropriate.
Dispersal of a substance and its derivatives throughout the natural environment or throughout an organism.
Final location(s) of a substance within an organism after dispersal.
See partition ratio
Theoretical volume of a body compartment throughout which a substance is calculated to be distributed.
See 2,3-bis(sulfanyl)propan-1-ol
Excretion of urine, especially in excess.
micturitic Agent which increases urine production.
See adduct, deoxyribonucleic acid
See gene amplification, deoxyribonucleic acid
See deoxyribonucleic acid cloning
See deoxyribonucleic acid repair
See deoxyribonucleic acid sequencing
Allele which expresses its phenotypic effect when present in either the homozygous or the heterozygous state. After
Half life of a fraction of a substance in a specific organ or compartment if it defines approximately the overall clearance rate for that substance at a specific time point.
Genetic change occurring in a germ cell which does not cause dysfunction of the gamete but which is lethal to the fertilized egg or developing embryo which develops from it. Note: Induction of a dominant lethal event after exposure to a chemical substance (dominant lethal test) indicates that the substance has affected germinal tissue of the test species.
Dose divided by product of mass of organism and time of dose. Note: Often expressed as mg (kg body weight)-1 day-1 and may be used as a synonym for dose.
(of a substance Total amount of a substance administered to, taken up, or absorbed by an organism, organ, or tissue.
(of radiation Energy or amount of photons absorbed by an irradiated object during a specified exposure time divided by area or volume.
Relation between dose and the magnitude of a measured biological change.
Graph of the relation between dose and the magnitude of the biological change produced measured in appropriate units.
Association between dose and the resulting magnitude of a continuously graded change, either in an individual or in a population.
Graph of the relation between dose and the proportion of individuals in a population responding with a defined biological effect.
Association between dose and the incidence of a defined biological effect in an exposed population usually expressed as percentage.
Evaluation of materials for their potential to cause dermal or ocular irritation and corrosion following local exposure; generally using the rabbit model (almost exclusively the New Zealand White) although other animal species have been used.
medicine pharmaceutical Any substance which when absorbed into a living organism may modify one or more of its functions. Note: The term is generally accepted for a substance taken for a therapeutic purpose, but is also commonly used for abused substances.
duplicate diet study Study in which test persons consume their ordinary diet but, for each meal, they prepare for subsequent analysis a duplicate portion of all food as prepared, served and consumed.
Two (or multiple) samples taken under the same or comparable conditions.
Imperfect articulation of speech due to neuromuscular damage.
Abnormal, impaired, or incomplete functioning of an organism, organ, tissue or cell.
Abnormal development of an organ or tissue identified by morphological examination.
Difficult or labored breathing.
Study of the influence of hereditary factors on the effects of xenobiotics on individual organisms.
Branch of biology which studies the interactions between living organisms and all factors (including other organisms) in their environment: such interactions encompass environmental factors which determine the distributions of living organisms.
Grouping of organisms (micro-organisms, plants, animals) interacting together, with and through their physical and chemical environments, to form a functional entity within a defined environment.
Concentration of a pesticide (active ingredient, formulations, and relevant metabolites) that is likely to affect a determinable ecological characteristic of an exposed system. After
Study of the toxic effects of chemical and physical agents on all living organisms, especially on populations and communities within defined ecosystems; it includes transfer pathways of these agents and their interactions with the environment.
See pheromone
Substance intended to kill parasites living on the exterior of the host.
Acute or chronic skin inflammation with erythema, papules, vesicles, pustules, scales, crusts or scabs, alone or in combination, of varied etiology.
oedema Presence of abnormally large amounts of fluid in intercellular spaces of body tissues.
Concentration of a substance that causes a defined magnitude of response in a given system. Note: EC50 is the median concentration that causes 50 % of maximal response.
Dose of a substance that causes a defined magnitude of response in a given system. Note: ED50 is the median dose that causes 50 % of maximal response.
Fluid, solid or gas discharged from a given source into the external environment.
Sequence in the promoter region of a gene that regulates expression of that gene through interaction with a trans-acting factor.
Disappearance of a substance from an organism or a part thereof, by processes of metabolism, secretion, or excretion.
See also clearance
Period taken for the plasma concentration of a substance to decrease by half. Note: May also be applied to other body compartments such as blood, specific organs, or tissues.
Differential with respect to time of the concentration or amount of a substance in the body, or a part thereof, resulting from elimination.
Substance that contributes to the elimination of a poison from an organism.
Stage in the developing mammal at which the characteristic organs and organ systems are being formed: for humans, this involves the stages of development from the second to the eighth week (inclusive post conception). In birds, the stage of development from the fertilization of the ovum up to hatching. In plants, the stage of development within the seed.
Period from fertilization to the end of major organogenesis.
Production by a substance of toxic effects in progeny in the first period of pregnancy between conception and the fetal stage. Any toxic effect on the conceptus as a result of prenatal exposure during the embryonic stages of development: these effects may include malformations and variations, malfunctions, altered growth, prenatal death, and altered postnatal function.
Change in the embryo and the regulation of its development.
Vomiting.
discharge effluent release Release of a substance from a source, including discharges to the wider environment.
Technical and administrative procedures and specifications applied for the monitoring, reduction or elimination of emissions from a source or exposure to a target.
Quantitative limit on the emission or discharge of a substance from a source, usually expressed in terms of a time-weighted average concentration or a ceiling value.
Present in a community or among a group of people; said of a disease prevailing continually in a region.
Portion of a conjugated metabolite which is derived from a natural product (such as a sugar, amino acid or other organic acid) of the metabolizing organism. See also exocon, phase II reaction. After
Pertaining to hormones or to the glands that secrete hormones directly into the bloodstream.
endocrine modifier Exogenous chemical that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, its progeny or (sub)populations.
Uptake of material into a cell by invagination of the plasma membrane and its internalization in a membrane-bounded vesicle.
See also phagocytosis, pinocytosis
antonym exogenous Produced within or caused by factors within an organism.
Intracellular complex of membranes in which proteins and lipids, as well as molecules for export, are synthesized and in which the biotransformation reactions of the mono-oxygenase enzyme systems occur. Note: May be isolated as microsomes following cell fractionation procedures.
Pertaining to the layer of flat cells lining the inner surface of blood and lymphatic vessels, and the surface lining of serous and synovial membranes.
Layer of flattened epithelial cells lining the heart, blood vessels and lymphatic vessels.
Toxin that forms an integral part of the cell wall of certain bacteria and is released only upon breakdown of the bacterial cell.; endotoxins do not form toxoids.
Intestinal inflammation.
Cyclical process involving intestinal re-absorption of a substance that has been excreted through the bile, followed by transfer back to the liver, making it available for biliary excretion again.
Aggregate, at a given moment, of all external conditions and influences to which a system under study is subjected.
Adverse effects to the natural environment.
Level (concentration or amount or a time integral of either) of a substance to which an organism or other component of the environment is exposed in its natural surroundings.
Destiny of a chemical or biological pollutant after release into the natural environment.
Human welfare and its influence by the environment, including technical and administrative measures for improving the human environment from a health point of view.
Estimate of the adverse effects to health or risks likely to follow from a proposed or expected environmental change or development.
Critical publications of IPCS containing reviews of methodologies and existing knowledge - expressed, if possible, in quantitative terms - of selected substances (or groups of substances) on identifiable, immediate, and long-term effects on human health and welfare.
environmental sanitation Practical control measures used to improve the basic environmental conditions affecting human health, for example clean water supply, human and animal waste disposal, protection of food from biological contamination, and housing conditions, all of which are concerned with the quality of the human environment.
Appraisal of the possible environmental consequences of a past, ongoing, or planned action, resulting in the production of an environmental impact statement or ‘finding of no significant impact (FONSI)’.
Report resulting from an environmental impact assessment.
Specialty devoted to the prevention and management of environmentally-induced injury, illness and disability, and the promotion of the health of individuals, families, and communities by ensuring a healthy environment.
Continuous or repeated measurement of agents in the environment to evaluate environmental exposure and possible damage by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and resultant adverse effects.
Actions taken to prevent or minimize adverse effects to the natural environment. Complex of measures including monitoring of environmental pollution, development and practice of environmental protection principles (legal, technical, and hygienic), including risk assessment, risk management and risk communication.
Overall state to be aimed for in a particular aspect of the natural environment, for example, “water in an estuary such that shellfish populations survive in good health”. Note: Unlike an environmental quality standard, the EQO is usually expressed in qualitative and not quantitative terms.
ambient standard Amount concentration or mass concentration of a substance that should not be exceeded in an environmental system, often expressed as a time-weighted average measurement over a defined period.
Estimate of the probability that harm will result from a defined exposure to a substance in an environmental medium. The estimate is valid only for a given species and set of conditions.
See sidestream smoke
Chemical transformation of substances resulting from interactions in the environment.
See ecotoxicologically relevant concentration
Present in a community or among a group of animals; said of a disease prevailing continually in a region.
Biological catalyst: a protein, nucleic acid or a conjugate of a protein with another compound (coenzyme).
Process whereby an enzyme is synthesized in response to a specific substance or to other agents such as heat or a metal species.
Study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems.
Pertaining to the upper-middle region of the abdomen.
- epigen-esis n., -etic
Changes in an organism brought about by alterations in the expression of genetic information without any change in the genome itself (e.g. base hypermethylation or histone modification). Note: The genotype is unaffected by such a change but the phenotype is altered.
Occurring in severe or sudden spasms, as in convulsion or epilepsy.
Any tumor derived from epithelium.
Sheet of one or more layers of cells covering the internal and external surfaces of the body and hollow organs.
Any part of a molecule that acts as an antigenic determinant: a macromolecule can contain many different epitopes each capable of stimulating production of a different specific antibody.
State of a system in which the defining variables (temperature, pressure, chemical potential) have constant values in time.
Diameter of a spherical particle of the same density as a particle under investigation that, relative to a given phenomenon or property, would behave in the same way as the particle under investigation.
Redness of the skin produced by congestion of the capillaries.
Slough or dry scab on an area of skin that has been burnt.
Prediction of the daily intake of a residue of a potentially harmful agent based on the most realistic estimation of the residue levels in food and the best available food consumption data for a specific population: residue levels are estimated taking into account known uses of the agent, the range of contaminated commodities, the proportion of a commodity treated, and the quantity of home-grown or imported commodities. Note: The EDI is expressed in mg residue per person.
Predicted concentration of a substance, typically a pesticide, within an environmental compartment based on estimates of quantities released, discharge patterns and inherent disposition of the substance (fate and distribution) as well as the nature of the specific receiving ecosystems. See also expected environmental concentration After
Measured or calculated amount or mass concentration of a substance to which an organism is likely to be exposed, considering exposure by all sources and routes.
Measured or calculated dose of a substance to which an organism is likely to be exposed, considering exposure by all sources and routes.
Prediction of the maximum daily intake of a residue of a potentially harmful agent based on assumptions of average food consumption per person and maximum residues in the edible portion of a commodity, corrected for the reduction or increase in residues resulting from preparation, cooking, or commercial processing. Note: The EMDI is expressed in mg residue per person.
aetiology
Science dealing with the cause or origin of disease. In individuals, the cause or origin of disease.
antonym prokaryote Cell or organism with the genetic material packed in a membrane-surrounded structurally discrete nucleus and with well-developed cell organelles. Note: The term includes all organisms except archaebacteria, eubacteria and cyanobacteria (until recently classified as cyanophyta or blue-green algae).
List of all substances supplied either singly or as components in preparations to persons in a Member State of the European Community on any occasion between 1 January 1971 and 18 September 1981.
Describes a body of water with a high concentration of nutrient salts and a high or excessive rate of biological production.
Adverse change in the chemical and biological status of a body of water following depletion of the oxygen content caused by decay of organic matter resulting from high primary production as a result of enhanced input of nutrients.
Additional or excess risk incurred over the lifetime of an individual by exposure to a toxic substance.
See rate difference
Method of active artificial elimination of toxicity consisting in complete replacement of blood of the patient by donor blood.
Any largely inert substance added to a drug to give suitable consistency or form to the drug.
Pathological process by which neurons are damaged and killed by the overactivation of receptors for the excitatory neurotransmitter glutamate, such as the NMDA receptor and AMPA receptor. Note: Excitotoxins like NMDA and kainic acid bind to glutamate t receptors, and can cause excitotoxicity by allowing high levels of calcium ions to enter cells, activating enzymes such as phospholipases, endonucleases, and proteases such as calpain which damage cell structures including the cytoskeleton, membranes, and DNA.
Discharge or elimination of an absorbed or endogenous substance, or of a waste product, and (or) its metabolites, through some tissue of the body and its appearance in urine, feces, or other products normally leaving the body. Note: Excretion does not include the passing of a substance through the intestines without absorption.
See also clearance, elimination
Amount of substance and (or) its metabolites that is excreted divided by time of excretion.
Portion of a conjugated metabolite that is derived from the parent molecule.
antonym endogenous Resulting from causes or derived from materials external to an organism.
See xenobiotic
Coding section of a gene that is separated from other coding sequences of the same gene by intervening noncoding sequences. See intron
Layer of flattened epithelial cells external to an organ or tissue.
Calculated concentrations of a substance, typically a pesticide, in various environmental compartments based on calculations using maximum-exposure scenarios. Note: EEC models assume a maximum number of applications per growing season at the maximum rate of application according to the application methods stated on the product label. After
See microcosm
Living tissue removed from its normal environment and transferred to an artificial medium for growth.
Variation of a quantity according to the law A = Ae– λt where A and A0are the values of the quantity being considered at time t and zero respectively, and λ is an appropriate constant.
antonyms non-exposed, unexposed Subject to a factor that is under study in the environment, for instance an environmental hazard.
- exposed group (sometimes abbreviated to exposed (in epidemiology)
People (or other organisms) who have been exposed to a supposed cause of a disease or health state of interest, or possess a characteristic that is a determinant of the health outcome of interest.
Concentration, amount or intensity of a particular physical or chemical agent or environmental agent that reaches the target population, organism, organ, tissue or cell, usually expressed in numerical terms of concentration, duration, and frequency (for chemical agents and micro-organisms) or intensity (for physical agents). Process by which a substance becomes available for absorption by the target population, organism, organ, tissue or cell, by any route. For X- or gamma radiation in air, the sum of the electrical charges of all the ions of one sign produced when all electrons liberated by photons in a suitably small element of volume of air completely stopped, divided by the mass of the air in the volume element.
Process of measuring or estimating concentration (or intensity), duration and frequency of exposures to an agent present in the environment or, if estimating hypothetical exposures, that might arise from the release of a substance, or radionuclide, into the environment.
See emission and exposure control
See concentration-effect curve
General term defining an administrative substance concentration or intensity of exposure that should not be exceeded.
In a case control study, value obtained by dividing the rate at which persons in the case group are exposed to a risk factor (or to a protective factor) by the rate at which persons in the control group are exposed to the risk factor (or to the protective factor) of interest.
See concentration-response relationship, dose-response relationship
Surface on a target where a substance, e.g., a pesticide is present. With mammals, examples of outer exposure surfaces include the exterior of an eyeball, the skin surface and a conceptual surface over the nose and open mouth. Examples of inner exposure surfaces include the gastrointestinal tract, the respiratory tract and the urinary tract lining.
Determination of the level, concentration or uptake of a potentially toxic compound and (or) its metabolite(s) in biological samples from an organism (blood, urine, hair etc.) and the interpretation of the results to estimate the absorbed dose or degree of environmental pollution; or the measuring of biochemical effects, usually not direct adverse effects of the substance, and relating them to the quantity of substance absorbed, or to its concentration in the environment.
Partial or full complementary DNA sequence which can serve as a marker for a region of the genome which encodes an expressed product.
Conversion of the genetic information encoded in DNA into a final gene product (either a protein or any of the different types of RNA). Note: Because changes in RNA synthesis are often estimated by measuring mRNA levels, the term “gene expression” is often misleadingly used as synonymous with transcription. The term “gene expression” includes transcription, processing, and splicing of mRNA, as well as translation, and post-translational modification of the protein product.
Generalizability of the results of a particular study, beyond the limits of the population actually studied.
Volume within a tissue, outside cells and excluding vascular and lymphatic space.
Volume of fluid outside the cells but within the outer surface of an organism.
Amount of substance extracted from a source divided by the total contained within the source.
Probability that an agent produces an observed response, as distinguished from the probability that the response is caused by a spontaneous event unrelated to the agent.
Refers to a pesticide residue or contaminant arising from environmental sources (including former agricultural uses) other than the use of a pesticide or contaminant substance directly or indirectly on the commodity. It is the maximum concentration of a pesticide residue or contaminant that is recommended by the Codex Alimentarius Commission to be legally permitted or recognized as acceptable in or on food, agricultural commodity or animal feed. Note: The mass content is expressed in milligrams of pesticide residue or contaminant per kilogram of commodity.
Calculation, based on quantitative observations in exposed test species or in vitro test systems, of predicted dose-effect and dose-response relationships for a substance in humans and other biota including interspecies extrapolations and extrapolation to susceptible groups of individuals. Note: The term may also be used for qualitative information applied to species or conditions that are different from the ones in which the original investigations were carried out.
Involuntary movements, e.g., those that occur as a side effect of psychiatric medications.
Ability to produce offspring frequently and in large numbers. In demography, the physiological ability to reproduce. Ability to produce offspring within a given period of time.
ectohormone pheromone Substance used in olfactory communication between organisms of the same species eliciting a change in sexual or social behavior.
Ability to conceive and to produce offspring: for litter-bearing species the number of offspring per litter is used as a measure of fertility. Note: Reduced fertility is sometimes referred to as subfertility.
Produces abnormalities of male or female reproductive functions or impairs reproductive capacity.
Substance applied to soil or hydroponic systems for improving the root nutrition of plants with the aim of increasing crop yields and (or) controlling production.
See fetus
- fetus (often incorrectly foetus)
Young mammal within the uterus of the mother from the visible completion of characteristic organogenesis until birth. Note: In humans, this period is usually defined as from the third month after fertilization until birth (prior to this, the young mammal is referred to as an embryo).
Abnormal formation of fibrous tissue.
Form of confidence limit given as a stated probability, for example P = 0.95. Note: In toxicology the terms fiducial limits and confidence limits are generally considered to be synonymous.
first-order reaction
Chemical reaction where the initial rate is directly proportional to the concentration of one of the reactants.
Any process in which a variable decreases with time at a constant fractional amount.
Biotransformation and, in some cases, elimination of a substance in the liver after absorption from the intestine and before it reaches the systemic circulation.
Acute toxicity test in which a substance is tested initially at a small number (3 or 4) predefined doses to identify which produces evident toxicity without lethality: the test may be repeated at one or more higher or lower defined discriminating doses to satisfy the criteria.
See fluorosis
fluoridosis Adverse effects of fluoride, as in dental or skeletal fluorosis.
- flux (of a quantity) Flow rate of an entity through a cross-section perpendicular to the flow divided by the cross-sectional area.
- foci (singular focus in neoplasia
Small groups of cells distinguishable, in appearance or histochemically, from the surrounding tissue: indicative of an early stage of a lesion that may lead to the formation of a neoplastic nodule.
See fetus
See cohort study
Any substance, not normally consumed as a food by itself and not normally used as a typical ingredient of a given food, whether or not it has nutritive value, that is added intentionally to food for a technological (including organoleptic) purpose in the manufacture, processing, preparation, treatment, packing, packaging, transport or holding of the food. Addition results, or may be reasonably expected to result (directly or indirectly), in the substance or its byproducts becoming a component of, or otherwise affecting, the characteristics of the food to which it is added. Note: The term does not include “contaminants” or substances added to food for maintaining or improving nutritional qualities.
Hypersensitivity reaction to substances in the diet to which an individual has previously been sensitized.
Sequence of transfer of matter and energy in the form of food from organism to organism in ascending or descending trophic levels.
Physiologically based reproducible, unpleasant (adverse) reaction to a specific food or food ingredient that is not immunologically based.
Network of food chains.
Method of stimulating diuresis based on performing hydrational therapy, sometimes with parallel introduction of diuretics, with the aim of achieving increased clearance of a toxic substance in urine.
See xenobiotic
Changes in allelic frequencies that occur when a small group is separated from a large population and establishes a colony in a new location.
Process of classification of an analyte or a group of analytes from a sample according to physical (e.g. size, solubility) or chemical (e.g. bonding, reactivity) properties.
Point mutation involving either the deletion or insertion of one or two nucleotides in a gene: by the frame shift mutation, the normal reading frame used when decoding nucleotide triplets in the gene is altered.
Substance that is vaporized in order to kill or repel pests.
Development and implementation of technologies to characterize the mechanisms through which genes and their products function and interact with each other and with the environment.
Substance intended to kill fungi.
Substance obtained from fungi that has an insecticidal effect reflecting the pathogenicity of the fungi for insects.
Reproductive cell (either sperm or egg) containing a haploid set of chromosomes.
Substance intended to kill gametes.
Inflammation of the stomach and intestine.
Pertaining or communicating with the stomach and intestine.
Administration of materials directly into the stomach by esophageal intubation.
Length of DNA that encodes a functional product, which may be a polypeptide or a ribonucleic acid. Note: A gene is the fundamental unit of heredity After
Occurrence of extra copies of a gene; with respect to a plasmid, an increase in the number of plasmid copies per cell, which may be induced by a specific treatment. Note: Spontaneous gene amplification frequently occurs in tumor cells.
Transcriptional activation of a gene so that its functional product is produced.
Introduction of genetic material into an individual, or the modification of the individual’s genetic material, in order to achieve a therapeutic or prophylactic objective. After
Study of the correlations between phenotypic trends and genetic variation across population groups and the application of the results of such a study to control of health problems.
Map showing the positions in the genome of genes or other genetic markers, either relative to each other or as a physical map of absolute distances.
Phrase used to describe the U.S. FDA philosophy that justifies approval of food additives that may not meet the usual test criteria for safety but have been used extensively and have not demonstrated to cause any harm to consumers.
Bacterium, plant or animal whose deoxyribonucleic acid has been deliberately altered.
Existence of inter-individual differences in DNA sequences coding for one specific gene, giving rise to different functional and (or) morphological traits. After
Predisposition to a particular disease or sensitivity to a substance due to the presence of a specific allele or combination of alleles in an individual’s genome. After
Study of chemically or physically induced changes to the structure of DNA, including epigenetic phenomena or mutations that may or may not be heritable.
Complete set of chromosomal and extrachromosomal genes of an organism, a cell, an organelle, or a virus, i.e. the complete DNA component of an organism. Note: This includes both the DNA present in the chromosomes and that in subcellular organelles (e.g. mitochondria or chloroplasts). It also includes the RNA genomes of some viruses.
Science of using DNA and RNA based technologies to demonstrate alterations in genes expression. (in toxicology) Method providing information on the consequences for genes expression of interactions of the organism with environmental stress, xenobiotics, etc.
Capable of causing a change to the structure of the genome.
Genetic constitution of an organism as revealed by genetic or molecular analysis; the complete set of genes possessed by a particular organism, cell, organelle or virus.
axenic animal
Animal grown under sterile conditions in the period of postnatal development: such animals are usually obtained by Caesarean operation and kept in special sterile boxes in which there are no viable micro-organisms (sterile air, food and water are supplied).
Cell with a haploid chromosome content. Note: In animals, the germ-line cells are the sperm or egg (synonym gamete); in plants, the pollen cell or the ovum. After
Complete failure of gonad development.
Pertaining to a tuft or cluster, as of a plexus of capillary blood vessels or nerve fibers, especially referring to the capillaries of the glomerular of the kidney.
Tuft or a cluster, as of a plexus of capillary blood vessels or nerve fibers, e. g. capillaries of the filtration apparatus of the kidney.
Formation of an ultrafiltrate of the blood occurring in the glomerulus of the kidney.
Volume of ultrafiltrate formed in the kidney tubules from the blood passing through the glomerular capillaries divided by time of filtration.
Solvent abuse using plastic cement or other solvent-based adhesives.
See glycomics
Description of the complete set of carbohydrates and their functions in a living organism.
glycobiology Global study of the structure and function of carbohydrates, especially oligosaccharides (short chains of sugars) in a living organism.
See gnotobiote
Specifically and entirely known microfauna and microflora of a specially reared laboratory animal.
- gnotobiot-e n., -ic
gnotobiont Specially reared laboratory animal whose microflora and microfauna are specifically known in their entirety.
Noncancerous enlargement of the thyroid gland, visible as a swelling at the front of the neck, that is often associated with iodine deficiency.
Any substance (such as thiouracil) that induces the formation of a goiter.
Pertaining to effects on sex glands and on the systems that regulate them.
Nationally authorized safe uses of pesticides under actual conditions necessary for effective and reliable pest control. Note: It encompasses a range of levels of pesticide applications up to the highest authorized use, applied in a manner that leaves a residue which is the smallest amount practicable. Authorized safe uses include nationally registered or recommended uses, that take into account public and occupational health and environmental safety considerations. Actual conditions include any stage in the production, storage, transport, distribution, and processing of food commodities and animal feed.
Fundamental rules incorporated in OECD guidelines and national regulations concerned with the process of effective organization and the conditions under which laboratory studies are properly planned, performed, monitored, recorded, and reported.
Fundamental rules incorporated in national regulations concerned with the process of effective organization of production and ensuring standards of defined quality at all stages of production, distribution and marketing. Note: Minimization of waste and its proper disposal are part of this process.
antonyms all-or-none effect, quantal effect, stochastic effect Consequence that can be measured on a graded scale of intensity or severity and its magnitude related directly to the dose or concentration of the substance producing it.
Pesticide (herbicide) used for the control of weedy grasses (Gramineae).
Granular growth or tumor, usually of lymphoid and epithelial cells.
Dusting or spraying of plants with pesticides by hand, by special machines, or by apparatus fixed to tractors or driven by them.
Scientifically judged quantitative value (a concentration or number) of an environmental constituent that ensures aesthetically pleasing air, water or food and from which no adverse effect is expected concerning noncarcinogenic endpoints, or that gives an acceptably low estimate of lifetime cancer risk from those substances which are proven human carcinogens or carcinogens with at least limited evidence of human carcinogenicity.
Quantitative measure (a concentration or a number) of a constituent of an environmental medium that ensures aesthetically pleasing air, water, or food and does not result in a significant risk to the user.
Sets of atmospheric concentrations and exposure times that are associated with specific effects of varying degrees of pollution on man, animals, vegetation, and the environment in general.
Sets of concentrations, numbers and exposure times that are associated with the specific effects of factors in environmental media on man, animals, vegetation, and the environment in general.
Magnusson and Kligman test Widely used skin test for screening possible contact allergens: considered to be a useful method to identify likely moderate and strong sensitizers in humans.
See heme
- half life, t1-2
half time Time required for the concentration of a reactant in a given reaction to reach a value that is the arithmetic mean of its initial and final (equilibrium) values. For a reactant that is entirely consumed it is the time taken for the reactant concentration to fall to one half of its initial value. Note: The half life of a reaction has meaning only in special cases:
For a first-order reaction, the half life of the reactant may be called the half life of the reaction. For a reaction involving more than one reactant, with the concentrations of the reactants in their stoichiometric ratios, the half life of each reactant is the same, and may be called the half life of the reaction. If the concentrations of reactants are not in their stoichiometric ratios, there are different half lives for different reactants, and one cannot speak of the half life of the reaction. See also biological half life, elimination half life
- half time, t1-2
See half life
monoploid State in which a cell contains only one set of chromosomes.
Contraction of the phrase "haploid genotype", the genetic constitution of an individual with respect to one member of a pair of allelic genes: haplotype can refer to only one locus or to an entire genome (a genome-wide haplotype would comprise half of a diploid genome, including one allele from each allelic gene pair). Set of single nucleotide polymorphisms found to be statistically associated on a single chromatid.
Low-molecular-mass species which is not itself antigenic unless complexed with a carrier, such as a protein. Once bound, it presents an epitope that can cause the sensitization of lymphocytes. After
adverse effect Damage or adverse effect to a population, species, individual organism, organ, tissue or cell.
- harmful occupational factor
Component of the work environment the effect of which on a worker under certain conditions leads to ill health or reduction of working ability.
noxious substance Substance that, following contact with an organism can cause ill health or adverse effects either at the time of exposure or later in the life of the present and future generations.
Set of inherent properties of a substance, mixture of substances or a process involving substances that, under production, usage or disposal conditions, make it capable of causing adverse effects to organisms or the environment, depending on the degree of exposure; in other words, it is a source of danger. See also risk
- hazard assessment
Determination of factors controlling the likely effects of a hazard such as the dose-effect and dose-response relationships, variations in target susceptibility, and mechanism of toxicity.
- hazard communication standard
US OSHA standard requiring all employers to inform employees of the hazard of substances in the workplace and the steps necessary to avoid harm.
- hazard evaluation
Establishment of a qualitative or quantitative relationship between hazard and benefit, involving the complex process of determining the significance of the identified hazard and balancing this against identifiable benefit. Note: This may subsequently be developed into a risk evaluation.
- hazard identification
Determination of substances of concern, their adverse effects, target populations, and conditions of exposure, taking into account toxicity data and knowledge of effects on human health, other organisms and their environment.
- hazard index (HI
Sum of the hazard quotients for substances that affect the same target organ or organ system. Note: Ideally, hazard quotients should be combined for pollutants that cause adverse effects by the same mechanism. Aggregate exposures below a hazard index of 1.0 were unlikely to result in adverse health effects over a lifetime of exposure. A hazard index greater than 1.0 does not necessarily suggest a likelihood of adverse effects. The hazard index cannot be translated to a probability that adverse effects will occur, and is not likely to be proportional to risk.
- hazard quotient (HQ
Ratio of toxicant exposure (estimated or measured) to a reference value regarded as corresponding to a threshold of toxicity. Note: If the hazard quotient exceeds unity, the toxicant may produce an adverse effect but normally this will require a hazard quotient of several times unity; a hazard quotient of less than one indicates that no adverse effects are likely over a lifetime of exposure.
- hazardous production factor
hazard at work hazardous occupational factor Production factor the effect of which on a worker under certain conditions results in injury or some impairment of health.
State of complete physical, mental and social well-being, and not merely the absence of disease or infirmity. State of dynamic balance in which an individual's or a group's capacity to cope with the circumstances of living is at an optimal level. State characterized by anatomical, physiological and psychological integrity, ability to perform personally valued family, work and community roles; ability to deal with physical, biological, psychological and social stress; a feeling of wellbeing; and freedom from the risk of disease and untimely death. In ecology, a sustainable steady state in which humans and other living organisms can coexist indefinitely.
- health advisory level (HAL
In the USA, non-regulatory health-based reference level of chemical traces (usually in ppm, i.e., mg L-1) in drinking water at which there are no adverse health risks when ingested over various periods of time. Note: Such levels are established for one day, 10 days, long-term and life-time exposure periods. They allow for a wide margin of safety.
- health-based exposure limit
Maximum concentration or intensity of exposure that can be tolerated without significant effect (based on only scientific and not economic evidence concerning exposure levels and associated health effects).
- health hazard
Any factor or exposure that may adversely affect health.
- health surveillance
Periodic medico-physiological examinations of exposed workers with the objective of protecting health and preventing occupationally related disease.
- healthy worker effect
Epidemiological phenomenon observed initially in studies of occupational diseases: workers usually exhibit lower overall disease and death rates than the general population, due to the fact that the old, severely ill and disabled are ordinarily excluded from employment. Death rates in the general population may be inappropriate for comparison, if this effect is not taken into account.
- heat shock proteins
stress proteins Group of proteins whose synthesis is increased by increased transcription when cells are exposed to elevated temperatures. Note: Production of high levels of heat shock proteins can also be triggered by exposure to different kinds of environmental stress conditions, e.g., infection, inflammation, exposure of the cell to chemicals (such as ethanol, arsenicals, or certain metal species), ultraviolet light, starvation, hypoxia (oxygen deprivation), nitrogen deficiency (in plants), or water deprivation. Hence, the alternative name, stress proteins. Their upregulation is sometimes described more generally as part of the stress response.
- heavy metal
toxic metal Erroneous terms used commonly in the toxicological literature but having no generally agreed meaning, sometimes even applied to nonmetals, and therefore a source of confusion and to be avoided. The term "metal" is adequate without the qualifying adjective but may be misleading since it implies a solid material when toxicological concern is mostly for the ionic form or another chemical species.
See anthelmint(h)ic
See anthelmint(h)ic
Vomiting of blood.
Localized accumulation of blood, usually clotted, in an organ, space, or tissue, due to a failure of the wall of a blood vessel.
Adverse changes in blood caused by exposure to chemicals.
Presence of blood in the urine.
haem Complex consisting of an iron ion coordinated to a porphyrin acting as a tetradentate ligand, and to one or two axial ligands. After
Hereditary disorder affecting iron metabolism in which excessive amounts of iron accumulate in the body tissues. Note: The disorder is characterized by diabetes mellitus, liver dysfunction, and a bronze pigmentation of the skin.
Use of an artificial kidney to remove toxic compounds from the blood by passing it through a tube of semipermeable membrane. Note: The tube is bathed in a dialysing solution to restore the normal chemical composition of the blood while permitting diffusion of toxic substances from the blood.
Heme-containing protein in red blood cells with an important function in transporting oxygen from the lungs to body tissues.
Presence of free hemoglobin in the urine.
Substance that damages the membrane of erythrocytes causing the release of hemoglobin.
Release of hemoglobin from erythrocytes, and its appearance in the plasma.
Passing blood through a column of charcoal or adsorbent resin for the removal of drugs or toxins.
Insoluble iron(III) hydroxide-based pigment deposited in cells in conditions of iron overload.
Equation of the form: pH = pKa – lg((HA)-(A– for the calculation of the pH of solutions where the ratio (HA)-(A–) is known and HA and A- are the hydronated and dehydronated forms of an acid, respectively. Corrected from
At constant temperature and pressure, the ratio of the partial pressure of a gas above a liquid to its solubility in the liquid and therefore a measure of its partition between the gas phase and the solute phase. Note 1: The solubility may be expressed in any convenient units, such as amount fraction, molality or amount (substance) concentration. The exact definition used should always be given. Note 2: Rigorously, the Henry’s law constant is the limiting value at zero partial pressure.
Pertaining to the liver.
Poisonous to liver cells.
Substance intended to kill plants.
Organism which has different allelic forms of a specified gene on each of a pair of homologous chromosomes or describing the genome of that organism. After
Graphical method for analysing binding of a molecule A to a macromolecule P with n binding sites. A Hill plot of lg(Θ-(1-Θ vs lg(A) has a slope of 1 if binding is non-co-operative and >1 for co-operative binding, where Θ = (A)bound-n(P)total is the fraction of sites occupied.
2-(1H-imidazol-4-yl)ethan-1-amine, an amine derived from histidine by decarboxylation and released from cells in the immune system as part of an allergic reaction: it is a powerful stimulant of gastric secretion, constrictor of bronchial smooth muscle, and vasodilator.
- histogenic origin
Germ cell layer of the embryo from which a given adult tissue develops.
Study (usually microscopic) of the anatomy of tissues and their cellular and subcellular structure.
Microscopic pathological study of the anatomy and cell structure of tissues in disease to reveal abnormal or adverse structural changes.
- hit-and-run effect
Toxicity which follows a single exposure to a substance.
Normal, internal stability in an organism maintained by co-ordinated responses of the organ systems that automatically compensate for environmental changes.
Degree of identity existing between the nucleotide sequences of two related but not complementary DNA or RNA molecules. Note 1: 70% homology means that on the average 70 out of every 100 nucleotides are identical in a given sequence. Note 2: The same term is used in comparing the amino acid sequences of related proteins.
Organism which has the same allelic form of a specified gene on each of a pair of homologous chromosomes or describing the genome of that organism. After
- horme-sis n., -tic
Benefit at low dose of a substance that is harmful at a higher dose.
Substance formed in one organ or part of the body and carried in the blood to another organ or part where it selectively alters functional activity.
- human ecology
Interrelationship between humans and the entire environment - physical, biological, socio-economic, and cultural, including the interrelationships between individual humans or groups of humans and other human groups or groups of other species.
- human equivalent dose
Human dose of an agent that is believed to induce the same magnitude of a toxic effect that the known animal dose has induced.
- human exposure threshold (of toxicological concern
Generic value of exposure to a substance, or a group of substances falling within a defined structural class, below which there is expected to be no appreciable risk to human health.
Chemical reaction of a substance with water, usually resulting in the formation of one or more new compounds.
- hydrophilic- adj., -ity n.
lipophobic antonym hydrophobic Describing the character of a substance, material, molecular entity or group of atoms which has an affinity for water.
- hydrophobic- adj., -ity n.
antonym hydrophilic Describing the character of a substance, material, molecular entity or group of atoms which is insoluble or confers insolubility in water, or resistance to wetting or hydration.
Science of health and its preservation.
antonym hypo- Prefix meaning above or excessive: when used with the suffix "-emia" refers to blood and with the suffix "-uria" refers to urine, for example "hyperbilirubinemia".
Excessive amount of blood in any part of the body.
Ingestion or administration of nutrients in excess of optimal amounts.
Excessive concentration of bilirubin in the blood.
Excessive concentration of calcium in the blood.
Excessive concentration of glucose in the blood.
Excessive concentration of potassium in the blood.
Excessive concentration of sodium in the blood.
Abnormally increased parathyroid gland activity that affects, and is affected by, plasma calcium concentration.
Abnormal multiplication or increase in the number of normal cells in a tissue or organ.
Term used to describe the responses of (effects on) an individual to (of) an agent when they are qualitatively those expected, but quantitatively increased.
Exaggeration of reflexes.
State in which an individual reacts with allergic effects following exposure to a certain substance (allergen) after having been exposed previously to the same substance. Note: Most common chemical-induced allergies are Type I (IgE-mediated) and Type IV (cell-mediated) hypersensitivity.
Excessive reaction following exposure to a given amount or concentration of a substance as compared with the large majority of other exposed subjects.
Persistently high blood pressure in the arteries or in a circuit, for example pulmonary hypertension or hepatic portal hypertension.
Excessive growth in bulk of a tissue or organ through increase in size but not in number of the constituent cells.
Condition resulting from the ingestion of an excess of one or more vitamins.
Prefix meaning under, deficient: when used with the suffix "-emia" refers to blood and with the suffix "-uria" refers to urine, for example "hypocalcemia".
Abnormally low calcium concentration in the blood.
Abnormally low potassium concentration in the blood.
abnormally low magnesium concentration in the blood.
Abnormally low sodium concentration in the blood.
Pertaining to an abnormally decreased volume of circulating fluid (plasma) in the body.
Deficient oxygenation of the blood.
Abnormally low dioxygen content or tension. Deficiency of dioxygen in the inspired air, in blood or in tissues, short of anoxia.
Dioxygen deficient.
Any adverse condition resulting from medical treatment.
Excess of bile pigment in the blood and consequent deposition and retention of bile pigment in the skin and the sclera.
See multiple chemical sensitivity
Genetically based unusually high sensitivity of an organism to the effect of certain substances.
According to the US NIOSH, the maximum exposure concentration from which one could escape within thirty minutes without any escape-impairing symptoms or any irreversible health effects.
Environmental concentration of a pollutant resulting from a combination of emissions and dispersals (often synonymous with exposure).
Ligand-binding assay that uses a specific antigen or antibody, capable of binding to the analyte, to identify and quantify substances. The antibody can be linked to a radioisotope (radioimmunoassay, RIA) or to an enzyme which catalyses an easily monitored reaction (enzyme-linked immunosorbent assay, ELISA), or to a highly fluorescent compound by which the location of an antigen can be visualized (immunofluorescence).
Product of an antigen-antibody reaction that may also contain components of the complement system.
Selective reaction of the body to substances that are foreign to it, or that the immune system identifies as foreign, shown by the production of antibodies and antibody-bearing cells or by a cell-mediated hypersensitivity reaction.
Integrated network of organs, glands, and tissues that has evolved to protect the body from foreign substances, including bacteria, viruses, and other infection-causing parasites and pathogens. Note: The immune system may produce hypersensitivity reactions reactions which, in the extreme, can be fatal. If the immune system misidentifies normal body components as foreign, this leads to autoimmune disorders, such as lupus, in which the body destroys its own constituents.
Study of biochemical and molecular aspects of immunology, especially the nature of antibodies, antigens and their interactions.
See antigen
Family of closely related glycoproteins capable of acting as antibodies and present in plasma and tissue fluids; immunoglobulin E (IgE) is the source of antibody in Type I hypersensitivity (allergic) reactions.
- immunoglobulin E-mediated hypersensitivity
State in which an individual reacts with allergic effects caused fundamentally by the reaction of antigen-specific immunoglobulin E following exposure to a certain substance (allergen) after having been exposed previously to the same substance.
Modification of the functioning of the immune system by the action of a substance that increases or reduces the ability to produce antibodies.
Enhancement of the capacity of the immune system to produce an effective response.
Reduction in the functional capacity of the immune response; may be due to:
Inhibition of the normal response of the immune system to an antigen. Prevention, by chemical or biological means, of the production of an antibody to an antigen by inhibition of the processes of transcription, translation or formation of tertiary structure.
Mechanisms by which the immune system is able to recognize and destroy malignant cells before the formation of an overt tumor.
Harmful to the immune system.
Of a membrane, not allowing a given substance to pass through. When applied to nonbiological membranes with no qualification, the term normally refers to water.
Attachment of the fertilized ovum (blastocyst) to the endometrium and its subsequent embedding in the compact layer, occurring 6 or 7 days after fertilization of the ovum.
Phrase applied to data generated and analysed using computer modeling and information technology.
antonym in vivo In glass, referring to a study in the laboratory usually involving isolated organ, tissue, cell, or biochemical systems.
antonym in vitro In the living body, referring to a study performed on a living organism.
Number of occurrences of illness commencing, or of persons falling ill, during a given period in a specific population: usually expressed as a rate. Note: When expressed as a rate, it is the number of ill persons divided by the average number of persons in the specified population during a defined period, or alternatively divided by the estimated number of persons at the mid-point of that period.
- incidence rate (epidemiology)
Measure of the frequency at which new events occur in a population. Note: This is the value obtained by dividing the number of new events that occur in a defined period by the population at risk of experiencing the event during this period, sometimes expressed as person-time.
- incremental unit risk estimate
For an air pollutant, this is the additional lifetime cancer risk occurring in a hypothetical population in which all individuals are exposed continuously from birth throughout their lifetimes to a concentration of 1 microgram per cubic meter (μg m-3) of the pollutant in the air they breathe.
Quantity value provided by a measuring instrument or a measuring system.
- indirect exposure
Exposure to a substance in a medium or vehicle other than the one originally receiving the substance. Exposure of people to a substance by contact with a person directly exposed.
- individual monitor
See personal sampler
- individual protective device (IPD
personal protective device (PPD) See personal protective equipment
- individual risk
Probability that an individual person will experience an adverse effect.
Substance that causes induction.
Increase in the rate of synthesis of an enzyme in response to the action of an inducer or environmental conditions. Note: Often the inducer is the substrate of the induced enzyme or a structurally similar substance (gratuitous inducer) that is not metabolized.
- induction period
latent period Time from the onset of exposure to the appearance of signs of disease.
- industrial hygiene
- inert chemical
Substance that is not generally reactive.
- inert ingredient
Any intentionally added ingredient of a mixture which does not contribute to the desired biological effect: this definition does not include impurities and does not imply that the inert ingredient has no biological effects. Related term: active ingredient
- infertility (in human medicine
Inability to become pregnant within 1 year of unprotected intercourse.
Reaction of the body to injury or to infectious, allergic, or chemical irritation; characterized by redness, swelling, heat, and pain resulting from dilation of the blood vessels accompanied by loss of plasma and leucocytes (white blood cells) into the tissues.
- infusion (in physiology
Therapeutic introduction of a fluid other than blood, as a (usually saline) solution, into a vein.
Process of taking food and drink into the body by mouth. Process of taking in particles by a phagocytic cell.
Act of drawing in of air, vapor or gas and any suspended particulates into the lung.
- inherently biodegradable
Class of compounds for which there is unequivocal evidence of biodegradation (primary or ultimate) in any test of biodegradability.
- inhibitory concentration (IC
Concentration of a substance that causes a defined inhibition of a given system. Note: IC50 is the median concentration that causes 50% inhibition.
- inhibitory dose (ID
Dose of a substance that causes a defined inhibition of a given system. Note: ID50 is the median dose that causes 50% inhibition.
Agent that induces a change in a chromosome or gene that leads to the induction of tumors after a second agent, called a promoter, is administered to the tissue. Substance that starts a chain reaction Note: An initiator is consumed in a chain reaction, in contrast to a catalyst.
Substance intended to kill insects.
Amount of a substance that is taken into the body, regardless of whether or not it is absorbed: the total daily intake is the sum of the daily intake by an individual from food, drinking-water, and inhaled air.
- integral indicator of toxic effect
Parameter (such as body weight or temperature) characterizing the overall changes in the general state of the organism exposed to a toxic substance.
Large scale protein–protein interaction map.
Inhomogeneous space region intermediate between two bulk phases in contact, and where properties are significantly different from, but related to, the properties of the bulk phases.
- intermittent effect
discontinuous effect Biological change that comes and goes at intervals.
- internal dose
See absorbed dose
Selection and comparison of index and comparison groups in such a manner that, apart from sampling error, the observed differences between these groups with respect to dependent variables under study may be attributed only to the hypothesized effect under investigation.
Estimation of a value between two known data points.
- interpretation (of data or findings)
Evaluation of the observations from an investigation or study in order to determine their significance for human health, for the environment or for both.
- interspecies dose conversion
Process of extrapolating from the doses of one animal species to another, for example from rodent dose to human equivalent.
- interstitial fluid
Aqueous solution filling the narrow spaces between cells.
Chronic form of pneumonia involving increase of the interstitial tissue and decrease of the functional lung tissue.
Epidemiological investigation designed to test a hypothesized cause-effect relationship by intentional change of a supposed causal factor in a population.
Absorption further down the intestinal tract of a substance or substances that have been absorbed before and subsequently excreted into the intestinal tract, usually through the bile.
Poisoning: pathological process with clinical signs and symptoms caused by a substance of exogenous or endogenous origin. Drunkenness following consumption of beverages containing ethanol or other compounds affecting the central nervous system.
- intrinsic activity
Maximal stimulatory effect induced by a compound in relation to that of a given reference compound.
- intrinsic clearance
Volume of plasma or blood from which a substance is completely removed in a period of time under unstressed conditions.
Specific protein required for the absorption of vitamin B12 and secreted by cells in the gastric glands of the stomach.
Non-coding sequence within genes which separates the exons (coding regions). Note: Introns are spliced out of the messenger RNA molecule created from a gene after transcription and prior to translation. After
- ionizing radiation
Any radiation consisting of directly or indirectly ionizing particles or a mixture of both or photons with energy higher than the energy of photons of ultraviolet light or a mixture of both such particles and photons.
- irreversible alteration
Change from normal structure or function that persists or progresses after cessation of exposure of the organism.
n., Substance that causes inflammation following immediate, prolonged or repeated contact with skin, mucous membrane, or other biological material. Note: A substance capable of causing inflammation on first contact is called a primary irritant. adj., Causing inflammation following immediate, prolonged or repeated contact with skin, mucous membrane or other tissues.
Local deficiency of blood supply and hence oxygen to an organ or tissue owing to constriction of the blood vessels or to obstruction.
Denoting a liquid exerting the same osmotic pressure or chemical potential of water (water potential) as another liquid with which it is being compared.
- itai-itai disease
Illness (renal osteomalacia) observed in the Toyama prefecture of Japan, resulting from the ingestion of cadmium-contaminated rice. Note: Damage occurred to the renal and skeleto-articular systems, the latter being very painful (“itai” means “ouch” in Japanese and refers to the intense pain caused by the condition).
Pathological condition characterized by deposition of bile pigment in the skin and mucous membranes, including the conjunctivae, resulting in yellow appearance of the patient or animal.
Simultaneous or successive effect of factors of diverse types (chemical, physical, biological) on an organism.
Semiochemical that is produced by one organism inducing a response in an organism of another species that is unfavorable to the emitter. Related terms: allomone, synomone
Branch of chemistry concerned with measuring and studying rates of chemical reactions.
Acetoacetate, beta-hydroxybutyrate and acetone, produced from acetyl-CoA, mainly in the mitochondria of liver cells when carbohydrates are so scarce that energy must be obtained from breaking down fatty acids; beta-hydroxybutyrate is not itself a ketone but is called a ketone body because, like the other compounds, it is produced from ketones.
Pathological increase in the production of ketone bodies, e.g., following blockage or failure of carbohydrate metabolism.
See toxicokinetics
Technique used to decrease the expression of a particular gene in a cell or living organism in order to define its function.
Technique used to express a exogenous gene or to overexpress an endogenous gene in a living organism in order to define its function. Note: In mammalian toxicology, this technique is most readily applied to the mouse.
Technique used to inactivate a particular gene in a living organism in order to define its function. Note: In mammalian toxicology, this technique is most readily applied to the mouse.
See lacrimation
Secretion and discharge of tears.
See lacrimator
Substance that irritates the eyes and causes the production of tears or increases the flow of tears.
Substance intended to kill larvae.
Reflex spasmodic closure of the sphincter of the larynx, particularly the glottic sphincter.
Main organ of voice production, the part of the respiratory tract between the pharynx and the trachea.
Weakness; exhaustion.
See latent period
- latent effect
See delayed effect
- latent period
Delay between exposure to a harmful substance and the manifestations of a disease or other adverse effects. Period from disease initiation to disease detection.
Irrigation or washing out of a hollow organ or cavity such as the stomach, intestine or the lungs.
cathartic purgative Substance that causes evacuation of the intestinal contents.
- lead colic (painters’ colic
Chronic intestinal pains and constipation caused by lead poisoning.
Area of pathologically altered tissue. Injury or wound. Infected patch of skin.
Deadly; fatal; causing death.
- lethal concentration (LC
Concentration of a substance in an environmental medium that causes death following a certain period of exposure.
- lethal dose (LD
Amount of a substance or physical agent (e.g. radiation) that causes death when taken into the body.
- lethal synthesis
Metabolic formation of a highly toxic compound often leading to death of affected cells.
Progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of leucocytes and their precursors in the bone marrow and blood.
Reduced concentration of leukocytes in the blood. See lgPow
lgPow
lgKow
Logarithm to the base 10 of the partition coefficient of a substance between octan-1-ol and water. Note: This is used as an empirical measure for lipophilicity in calculating bioaccumulation, fish toxicity, membrane adsorption and penetration etc.
- library (in DNA bio-informatics
Collection of DNA sequences in a searchable electronic form.
- library (in molecular biology)
Collection of genomic or complementary DNA sequences that have been cloned in a vector and grown in an appropriate host organism (e.g. bacteria, yeast). After
- life-long exposure
Subjection to a potentially toxic substance during the whole lifetime.
Ion, molecule, or molecular group that binds to another chemical entity to form a larger complex.
Substance intended to kill mollusks including the gastropod mollusk, Limax.
- limit recommended
See recommended exposure limit
- limit test
Acute toxicity test in which, if no ill-effects occur at a pre-selected maximum dose, no further testing at greater exposure levels is required.
- limit value (LV
Limit concentration at or below which Member States of the European Community must set their environmental quality standard and emission standard for a particular substance according to Community Directives.
- limited evidence
According to the US EPA's guidelines for Carcinogen Risk Assessment, “limited evidence” is a collection of facts and accepted scientific inferences that suggests that an agent may be causing an effect, but this suggestion is not strong enough to be considered established fact.
- linearized multistage model
Sequence of steps in which (a) a multistage model is fitted to tumor incidence data; (b) the maximum linear term consistent with the data is calculated; (c) the low-dose slope of the dose-response function is equated to the coefficient of the maximum linear term; and (d) the resulting slope is then equated to the upper bound of potency.
- lipophilic- adj., -ity n.
hydrophobic- adj., -ty n. antonyms hydrophilic- -ity, lipophobic- -ity Having an affinity for fat and high lipid solubility. Note: This is a physicochemical property which describes a partitioning equilibrium of solute molecules between water and an immiscible organic solvent, favoring the latter, and which correlates with bioaccumulation.
- lipophobic- adj., -ity n.
hydrophilic- adj., -ity n. antonyms hydrophobic- adj. ity n., lipophilic- adj. ity n. Having a low affinity for fat and a high affinity for water.
Artificially formed lipid droplet, small enough to form a relatively stable suspension in aqueous media, useful in membrane transport studies and in drug delivery. Lipid droplet in the endoplasmic reticulum of a fatty liver. After
- local effect
Change occurring at the site of contact between an organism and a toxicant.
In competitive binding assays, the logit-log dose relationship, in which the response is defined by: R = logit (y) = lg (y-(1 – y where y = b-b0 with b = fraction of tracer bound and b0 = value of b with no unlabelled ligand in the system. Note: Logit-transformed assay data frequently yield straight-line dose-response data, amenable to statistical analysis. More generally in toxicology, the transformation is applied to dose-response data where b0 denotes the maximum response in the absence of a toxic substance.
- log-normal distribution
Distribution function F(y), in which the logarithm of a quantity is normally distributed, i.e. F(y) = ƒgauss(ln y) where ƒgauss(χ) is a Gaussian (or normal) distribution.
- log-normal transformation
Transformation of data with a logarithmic function that results in a normal distribution.
- long-term effect
See chronic effect
- long-term exposure
See chronic exposure
- long-term toxicity
See chronic toxicity
- lowest effective dose (LED)
Lowest dose of a chemical inducing a specified effect in a specified fraction of exposed individuals.
- lowest lethal concentration found
See minimum lethal concentration
- Lowest-observed-adverse-effect level lowest-observed-adverse-effect level (LOAEL)
Lowest concentration or amount of a substance (dose), found by experiment or observation, which causes an adverse effect on morphology, functional capacity, growth, development, or life span of a target organism distinguishable from normal (control) organisms of the same species and strain under defined conditions of exposure.
- lowest-observed-effect level (LOEL)
Lowest concentration or amount of a substance (dose), found by experiment or observation, that causes any alteration in morphology, functional capacity, growth, development, or life span of target organisms distinguishable from normal (control) organisms of the same species and strain under the same defined conditions of exposure.
Animal cell that interacts with a foreign substance or organism, or one which it identifies as foreign, and initiates an immune response against the substance or organism. Note: There are two main groups of lymphocytes, B lymphocytes and T lymphocytes.
General term comprising tumors and conditions allied to tumors arising from some or all of the cells of lymphoid tissue.
Laboratory column of selected representative soil or a protected monolith of undisturbed field soil with which it is possible to sample and monitor the movement of water and substances.
Membrane-bound cytoplasmic organelle containing hydrolytic enzymes. Note: Release of these enzymes from lysosomes damaged by xenobiotics can cause autolysis of the cell.
Large (10-20 μm diameter) amoeboid and phagocytic cell found in many tissues, especially in areas of inflammation, derived from blood monocytes and playing an important role in host defense mechanisms.
Study of changes associated with disease that are visible to the naked eye without the need for a microscope.
See mercurialism
See guinea-pig maximization test
Smoke that is inhaled by the smoker.
Vague feeling of bodily discomfort.
Population of cells showing both uncontrolled growth and a tendency to invade and destroy other tissues. Note: A malignancy is life-threatening.
antonym benign
Tending to become progressively worse and to result in death if not treated. In cancer, cells showing both uncontrolled growth and a tendency to invade and destroy other tissues.
Emotional disorder (mental illness) characterized by an expansive and elated state (euphoria), rapid speech, flight of ideas, decreased need for sleep, distractibility, grandiosity, poor judgment and increased motor activity.
Ratio of the no-observed-adverse-effect level (NOAEL) to the theoretical or estimated exposure dose (EED) or concentration (EEC).
Diameter of a spherical particle with a mass equal to the mean mass of all the particles in a population.
Diameter of a spherical particle with the median mass of all the particles in a population.
Compilation of information required under the US OSHA Hazard Communication Standard on the identity of hazardous substances, health and physical hazards, exposure limits, and precautions.
Regulatory value defining the concentration that if inhaled daily (in the case of work people for 8 hours with a working week of 40 hours, in the case of the general population 24 hours) does not, in the present state of knowledge, appear capable of causing appreciable harm, however long delayed during the working life or during subsequent life or in subsequent generations.
peak daily average concentration of an air pollutant Highest of the average daily concentrations recorded at a definite point of measurement during a certain period of observation.
Under the Safe Drinking Water Act (USA), primary MCL is a regulatory concentration for drinking water which takes into account both adverse effects (including sensitive populations) and technological feasibility (including natural background levels): secondary MCL is a regulatory concentration based on “welfare”, such as taste and staining, rather than health, but also takes into account technical feasibility. Note: MCL Goals (MCLG) under the Safe Drinking Water Act do not consider feasibility and are zero for all human and animal carcinogens.
Occupational exposure limit legally defined in GB under COSHH as the maximum concentration of an airborne substance, averaged over a reference period, to which employees may be exposed by inhalation under any circumstances, and set on the advice of the HSC Advisory Committee on Toxic Substances.
See maximum allowable concentration
Maximum daily dose of substance whose penetration into a human body during a lifetime will not cause diseases or health hazards that can be detected by current investigation methods and will not adversely affect future generations.
Level, usually a combination of time and concentration, beyond which any exposure of humans to a chemical or physical agent in their immediate environment is unsafe.
Maximum contents of a pesticide residue (expressed as mg kg-1 fresh weight) recommended by the Codex Alimentarius Commission to be legally permitted in or on food commodities and animal feeds. Note: MRL’s are based on data obtained following good agricultural practice and foods derived from commodities that comply with the respective MRL's are intended to be toxicologically acceptable.
Maximum contents of a drug residue (expressed as mg kg-1 or μg kg-1 fresh weight) recommended by the Codex Alimentarius Commission to be legally permitted or recognized as acceptable in or on food commodities and animal feeds. Note: The MRL is based on the type and amount of residue considered to be without any toxicological hazard for human health as expressed by the acceptable daily intake (ADI) or on the basis of a temporary ADI that uses an additional uncertainty factor. It also takes into account other relevant public health risks as well as food technological aspects.
Highest concentration of a substance in an environmental medium that does not cause death of test organisms or species (denoted by LC0).
Highest amount of a substance that, when introduced into the body, does not kill test animals (denoted by LD0).
Maximum amount (dose) or concentration of a substance to which an organism can be exposed without leading to an adverse effect after prolonged exposure time.
High dose used in chronic toxicity testing that is expected on the basis of an adequate subchronic study to produce limited toxicity when administered for the duration of the test period. Note 1: It should not induce: (a) overt toxicity, for example appreciable death of cells or organ dysfunction, or (b) toxic manifestations that are predicted materially to reduce the life span of the animals except as the result of neoplastic development or (c) 10% or greater retardation of body weight gain as compared with control animals. Note 2: In some studies, toxicity that could interfere with a carcinogenic effect is specifically excluded from consideration.
maximum rate In Michaelis-Menten kinetics, the maximum rate of conversion of a substrate when its concentration is not rate limiting.
mean time Average lifetime of a molecular, atomic, or nuclear system in a specified state. Note: For an exponentially decaying system, it is the average time for the number of molecules, atoms or nuclei in a specified state to decrease by a factor of e, the base of natural logarithms.
- mean residence time (in pharmacokinetics) (MRT
Average time a drug molecule remains in the body or an organ after rapid intravenous injection. Note 1: Like clearance, its value is independent of dose. Note 2: After an intravenous bolus: tr = Am- A where tr is the MRT, A is the area under the plasma concentration-time curve, and Am is the area under the moment curve. Note 3: For a drug with one-compartment distribution characteristics, MRT equals the reciprocal of the elimination rate constant. After
See uncertainty
Statistically derived median concentration of a substance in an environmental medium expected to produce a certain effect in 50% of test organisms in a given population under a defined set of conditions. Note: ECn refers to the median concentration that is effective in n% of the test population.
Statistically derived median dose of a chemical or physical agent (radiation) expected to produce a certain effect in 50% of test organisms in a given population or to produce a half-maximal effect in a biological system under a defined set of conditions. Note: EDn refers to the median dose that is effective in n% of the test population.
Statistically derived median concentration of a substance in an environmental medium expected to kill 50% of organisms in a given population under a defined set of conditions.
Statistically derived median dose of a chemical or physical agent (radiation) expected to kill 50% of organisms in a given population under a defined set of conditions.
Statistically derived median time interval during which 50% of a given population may be expected to die following acute administration of a chemical or physical agent (radiation) at a given concentration under a defined set of conditions.
Statistically derived median concentration of a substance in an environmental medium expected to cause narcotic conditions in 50 % of a given population under a defined set of conditions.
- median narcotic dose (ND50
Statistically derived dose of a substance expected to cause narcotic conditions in 50 % of test animals under a defined set of conditions.
Science and practice of diagnosing, treating, or preventing disease and other damage to the body or mind. Any drug or therapy used to treat disease or injury. Note: Any substance may be used as a drug or a remedy; the end effect will depend on the dose.
Process of “reductive” cell division, occurring in the production of gametes, by means of which each daughter nucleus receives half the number of chromosomes characteristic of the somatic cells of the species. See also miosis.
Mad Hatter syndrome Chronic poisoning caused by exposure to mercury, often by breathing its vapor but also by skin absorption and, less commonly, by ingestion. Note: Central nervous system damage usually predominates.
See microcosm
Malignant tumor of the mesothelium of the pleura, pericardium or peritoneum, that may be caused by exposure to asbestos fibers and some other fibers.
bio-activation Biotransformation of a substance to a more biologically active derivative.
Proteins that catalyse chemical transformations of body constituents and, in more common usage, of xenobiotics.
metabolic half time Time required for one half of the quantity of a substance in the body to be metabolized. Note: This definition assumes that the final quantity in the body is zero. See half life.
Analysis and theoretical reconstruction of the way in which the body deals with a specific substance, showing the proportion of the intake that is absorbed, the proportion that is stored and in what tissues, the rate of breakdown in the body and the subsequent fate of the metabolic products, and the rate at which it is eliminated (see elimination) by different organs as unchanged substance or metabolites.
Biotransformation of a substance that takes place within a living organism.
Sum total of all physical and chemical processes that take place within an organism from uptake to elimination. In a narrower sense, the physical and chemical changes that take place in a substance within an organism, including biotransformation to metabolites.
Intermediate or product resulting from metabolism.
See metabonomics
metabolomics Evaluation of cells, tissues or biological fluids for changes in metabolite levels that follow exposure to a given substance, in order to determine the metabolic processes involved, to evaluate the disruption in intermediary metabolic processes that results from exposure to that substance, or to determine the part of the genome that is responsible for the changes. Note: Although “metabolomics” and “metabonomics” are frequently used as synonyms, there is a growing consensus that there is a difference in that “metabolomics” places a greater emphasis on comprehensive metabolic profiling, while “metabonomics” is used to describe multiple (but not necessarily comprehensive) metabolic changes caused by a biological perturbation. After
Abnormal transformation of an adult, fully differentiated tissue of one kind into a differentiated tissue of another kind.
Movement of bacteria or body cells, especially cancer cells, from one part of the body to another, resulting in change in location of a disease or of its symptoms from one part of the body to another. Growth of pathogenic micro-organisms or of abnormal cells distant from the site of their origin in the body.
See methemoglobin
methaemoglobin Derivative of hemoglobin that is formed when the iron(II) in the heme porphyrin is oxidized to iron(III); this derivative cannot transport dioxygen.
methaemoglobinaemia Presence of methaemoglobin in the blood in greater than normal proportion.
methaemoglobin-forming substance Substance capable of oxidizing directly or indirectly the iron(II) in hemoglobin to iron(III) to form methemoglobin.
Substance concentration of substrate at which the rate of reaction is equal to one half of the limiting rate (maximum rate). Note: Also called the Michaelis concentration. The Michaelis constant (Michaelis concentration) may be used only when Michaelis-Menten kinetics is obeyed.
Description of the dependence of an initial rate of reaction upon the concentration of a substrate S that is present in large excess over the concentration of an enzyme or other catalyst (or reagent) E with the appearance of saturation behavior following the Michaelis-Menten equation:
n = V(S)o-(KM + (S
where v is the observed initial rate, V is its limiting value at substrate saturation (i.e. (S) > > KM), and KM the substrate concentration when v = V-2. The definition is experimental, i.e. it applies to any reaction that follows an equation of this general form. The symbols Vmax or vmax are sometimes used for V. Note 1. The parameters V and KM (the ‘Michaelis constant’) of the equation can be evaluated from the slope and intercept of a linear plot of 1-v vs. 1-(S) (‘Lineweaver-Burk plot’) or from slope and intercept of a linear plot of v vs. v-(S) (‘Eadie-Hofstee plot’). Note 2. A Michaelis-Menten equation is also applicable to the condition where E is present in large excess, in which case the total concentration (E)o appears in the equation instead of (S)o. Note 3. The term has sometimes been used to describe reactions that proceed according to the scheme:
in which case KM = (k–1 + kcat)-k1 (Briggs-Haldane conditions). It has more usually been applied only to the special case in which k–1 >> kcat and KM = k–1-k1 = KS, the dissociation constant of the complex. In this case KM is a true dissociation constant (Michaelis-Menten conditions).
See also rate-controlling step
Simplest mechanism that explains Michaelis-Menten kinetics. Note 1: According to the mechanism, a substrate S first combines with a molecule of enzyme E, and this process is followed by a step in which the enzyme-substrate complex ES breaks down (sometimes with the participation of the solvent) into enzyme and reaction products:
If, as is usual, the substrate S is present in great excess of the enzyme it can be shown that steady-state conditions apply, and that the rate equation is:
where (E)o , (S)o are the total concentrations of enzyme and substrate. This equation is of the required general form of the Michaelis-Menten equation. Note 2: Other, more complicated, mechanisms lead to the Michaelis-Menten equation, adherence to which therefore does not require that the Michaelis-Menten mechanism applies.
Chronic presence of albumin in slight excess in urine.
Grid of nucleic acid molecules of known sequence linked to a solid substrate, which can be probed with a sample containing either messenger RNA or complementary DNA from a cell or tissue to reveal changes in gene expression relative to a control sample. Note: Micro-array technology, which is also known as “DNA gene chip” technology, allows the expression of many thousands of genes to be assessed in a single experiment. After
experimental model ecosystem Artificial test system that simulates major characteristics of the natural environment for the purposes of ecotoxicological assessment. Note: Such a system would commonly have a terrestrial phase, with substrate, plants and herbivores, and an aquatic phase, with vertebrates, invertebrates and plankton. The term “mesocosm” implies a more complex and larger system than the term “microcosm” but the distinction is not clearly defined.
Early or subclinical effects of exposure to elemental mercury detected at the low exposure levels.
Test for mutagenicity in which animals are treated with a test agent after which time the frequency of micronucleated cells is determined; if a test group shows significantly increased levels of micronucleated cells compared to a control group, the chemical is considered capable of inducing chromosomal damage.
Chronic presence of microprotein (alpha-1 and beta-2 microglobulin) in blood indicating proximal renal tubule damage.
Artefactual spherical particle, not present in the living cell, derived from pieces of the endoplasmic reticulum present in homogenates of tissues or cells. Note: Microsomes sediment from such homogenates (usually the S9 fraction) when centrifuged at 100 000 g for 60 minutes: the microsomal fraction obtained in this way is often used as a source of mono-oxygenase enzymes.
See diuretic
Taking an aliquot of a flowing liquid, such as urine, avoiding initial and terminal flow periods which are likely to be unrepresentative.
Neurological disease caused by methylmercury, first seen in subjects ingesting contaminated fish from Minamata Bay in Japan.
Complete conversion of organic substances to inorganic derivatives, often visible as microscopic deposits which may be associated with damage to soft tissue, e.g., in the kidney.
Estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure: this substance specific estimate is used by ATSDR health assessors to identify contaminants and potential health effects that may be of concern at hazardous waste sites.
Lowest concentration of a toxic substance in an environmental medium that kills individual organisms or test species under a defined set of conditions.
- minimum lethal dose (LDmin
Lowest amount of a substance that, when introduced into the body, may cause death to individual species of test animals under a defined set of conditions.
meiosis (obsolete) myosis Abnormal contraction of the pupil of the eye to less than 2 mm.
Liquid substances capable of mixing without separation into two phases; refers to liquid mixtures.
Substance used for the control of mites.
- mitochondri-on sing., -a pl.
Eukaryote cytoplasmic organelle that is bounded by an outer membrane and an inner membrane; the inner membrane has folds called cristae that are the centre of ATP synthesis in oxidative phosphorylation in the animal cell and supplement ATP synthesis by the chloroplasts in photosynthetic cells. Note: The mitochondrial matrix within the inner membrane contains ribosomes, many oxidative enzymes, and a circular DNA molecule that carries the genetic information for a number of these enzymes.
Substance that induces lymphocyte transformation or, more generally, mitosis and cell proliferation.
Process by which a cell nucleus divides into two daughter nuclei, each having the same genetic complement as the parent cell: nuclear division is usually followed by cell division.
See mono-oxygenase
See safety factor, uncertainty factor
limacide molluscicide Substance intended to kill mollusks.
Continuous or repeated observation, measurement, and evaluation of health and (or) environmental or technical data for defined purposes, according to prearranged schedules in space and time, using comparable methods for sensing and data collection. Note: Evaluation requires comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and adverse effects.
Pertaining to a specific protein from a single clone of cells, all molecules of this protein being the same.
Antibody produced by cloned cells derived from a single lymphocyte.
mixed-function oxidase Enzyme that catalyses reactions between an organic compound and molecular oxygen in which one atom of the oxygen molecule is incorporated into the organic compound and one atom is reduced to water; involved in the metabolism of many natural and foreign compounds giving both unreactive products and products of different or increased toxicity from that of the parent compound. Note: Such enzymes are the main catalysts of phase 1 reactions in the metabolism of xenobiotics by the endoplasmic reticulum or by preparations of microsomes.
- Monte Carlo simulation
Analysis of a sequence of events using random numbers to generate possible outcomes in an iterative process. After
Any departure, subjective or objective, from a state of physiological or psychological well-being: in this sense, “sickness”, “illness”, and “morbid condition” are similarly defined and synonymous.
Term (to be avoided) used loosely to refer to incidence or prevalence rates of disease.
Method for the estimation of the prevalence and (or) incidence of a disease or diseases in a population.
Substance that fixes a dyestuff in or on a material by combining with the dye to form an insoluble compound, used to fix or intensify stains in a tissue or cell preparation.
Death as studied in a given population or subpopulation. Note: The word mortality is often used incorrectly instead of mortality rate.
See death rate
Investigation dealing with death rates or proportion of deaths attributed to specific causes as a measure of response.
Process of removal of particles from the bronchi of the lungs in a mucus stream moved by cilia, thus contributing to uptake from the gastrointestinal tract.
Partitioning scheme based on the use of density and overlap matrices, at one time used for allocating the electrons of a molecular entity in some fractional manner among its various parts (atoms, bonds, orbitals).
Product of a compartmental analysis requiring more than two compartments.
Illness with pathogenesis dependent on complex interplay of genetic and (or) environmental factors. After
Toxicity test in which two to three generations of the test organism are exposed to the substance being assessed. Toxicity test in which only one generation is exposed and effects on subsequent generations are assessed.
idiopathic environmental intolerance Intolerance condition attributed to extreme sensitivity to various environmental chemicals, found in air, food, water, building materials, or fabrics. Note: This syndrome is characterized by the patient's belief that his or her symptoms are caused by very low-level exposure to environmental chemicals. The term “chemical” is used to refer broadly to many natural and man-made chemical agents, some of which have several chemical constituents. Several theories have been advanced to explain the cause of multiple chemical sensitivity, including allergy, toxic effects and neurobiologic sensitization. There is insufficient scientific evidence to confirm a relationship between any of these possible causes and symptoms.
Procedure that has evolved by combining single screening tests, and is the logical corollary of mass screening. Note 1: Where much time and effort have been spent by a population in attending for a single test such as mass radiography, it is natural to consider the economy of offering other tests at the same time. Note 2: Multiple (or multiphasic) screening implies the administration of a number of tests, in combination, to large groups of people.
Of a cell, capable of giving rise to several different kinds of structure or types of cell.
Cluster sampling with more than two stages, each sampling being made on aggregates (or clusters) in which the clusters already obtained by the preceding sampling have been divided.
Dose -response model for cancer death estimation of the form
P = 1 - exp(-(qo + q1d1+ q2d2 + … +qkdk
where P is the probability of cancer death from a continuous dose rate, di, of group (or stage) i = 0, 1, 2... , the q's are constants, and k is the number of dose groups (or, if less than the number of dose groups, k is the number of biological stages believed to be required in the carcinogenesis process). With the multistage model, it is assumed that cancer is initiated by cell mutations in a finite series of steps.
Type of sampling in which the sample is selected by stages, the sampling units at each stage being subsampled from the larger units chosen at the previous stage.
Set of statistical tools to analyse data matrices using regression and (or) pattern recognition techniques.
Of or belonging to the family of rats and mice (Muridae).
Agent that can induce heritable changes (mutations) of the genotype in a cell as a consequence of alterations in or loss of genetic material.
Induction (or generation) of heritable changes (mutations) of the genotype in a cell as a consequence of alterations or loss of genes or chromosomes (or parts thereof).
Ability of a physical, chemical, or biological agent to induce (or generate) heritable changes (mutations) in the genotype in a cell as a consequence of alterations or loss of genes or chromosomes (or parts thereof).
Any relatively stable heritable change in genetic material that may be a chemical transformation of an individual gene (gene or point mutation), altering its function, or a rearrangement, gain or loss of part of a chromosome, that may be microscopically visible (chromosomal mutation). Note: Mutation can be either germinal, and inherited by subsequent generations, or somatic and passed through cell lineage by cell division.
Pain or tenderness in a muscle or group of muscles.
Muscular weakness.
Toxin produced by a fungus. Note: Examples are aflatoxins, tricothecenes, ochratoxin and patulin.
Extreme dilation of the pupil of the eye, either as a result of normal physiological response or in response to a chemical exposure.
Reduction of bone marrow activity leading to a lower concentration of platelets, red cells and white cells in the blood.
Microscopic particle whose size is measured in nanometers, often restricted to so-called nanosized particles (NSPs; < 100 nm in aerodynamic diameter), also called ultrafine particles (see separate entry).
Scientific discipline involving the study of the actual or potential danger presented by the harmful effects of nanoparticles on living organisms and ecosystems, of the relationship of such harmful effects to exposure, and of the mechanisms of action, diagnosis, prevention and treatment of intoxications.
Nonspecific usage - an agent that produces insensibility or stupor. Specific usage - an opioid, any natural or synthetic drug that has morphine-like actions.
Substance increasing the rate of excretion of sodium ion in the urine.
Presence of a substance in nature, as distinct from presence resulting from inputs from human activities. Note: The contamination of the natural environment by some man-made compounds may be so widespread that it is practically impossible to get access to biota with a truly natural level; only ‘normal’ levels can be measured, those which are usually prevalent in places where there is no obvious local contamination.
See autopsy
- necro-sis n., -tic
Sum of morphological changes resulting from cell death by lysis and (or) enzymatic degradation, usually accompanied by inflammation and affecting groups of cells in a tissue. Note: Not to be confused with apoptosis
Probability of adverse effects occurring that can reasonably be described as trivial. Probability of adverse effects occurring that is so low that it cannot be reduced appreciably by increased regulation or investment of resources.
nematocide Substance used for the control of nematodes.
- neonat-e n., -al
Infant during the first 4 weeks of postnatal life Note: For statistical purposes some scientists have defined the period as the first seven days of postnatal life. The precise definition varies from species to species.
- neoplas-ia, -m
New and abnormal formation of tissue as a tumor or growth by cell proliferation that is faster than normal and continues after the initial stimulus (i) that initiated the proliferation has ceased.
Inflammation of the kidney, leading to kidney failure, usually accompanied by proteinuria, hematuria, edema, and hypertension.
renopathy Any disease or abnormality of the kidney.
Disease of the kidneys marked by degeneration of renal tubular epithelium.
Chemically harmful to the cells of the kidney.
Pertaining to a nerve or to the nerves.
Serious illness which is a consequence of consumption of toxic bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing brevetoxin; symptoms include gastroenteritis; rectal burning; paresthesias of the face, trunk, and limbs; myalgias; ataxia; vertigo; and reversal of hot-cold sensation. See also amnesic shellfish poisoning, diarrheal shellfish poisoning
Nerve cell, the morphological and functional unit of the central and peripheral nervous systems.
Any disease of the central or peripheral nervous system.
- neurotoxic- adj., -ity n.
Able to produce chemically an adverse effect on the nervous system: such effects may be subdivided into two types.
Central nervous system effects (including transient effects on mood or performance and pre-senile dementia such as Alzheimer's disease). Peripheral nervous system effects (such as the inhibitory effects of organophosphorus compounds on synaptic transmission).
Sequential oxidation of ammonium salts to nitrite and nitrate by micro-organisms.
Adverse effects occurring when the generation of reactive nitrogen species in a system exceeds the system’s ability to neutralize and eliminate them; nitrosative stress may lead to nitrosylation reactions that can alter protein structure thus inhibiting normal function.
This expression is applicable to a substance for which the available information is not sufficient to establish its safety, or when the specifications for identity and purity are not adequate, or when the available data show that the substance is hazardous and should not be used. Note: The basis for the use of the expression should be determined before action is taken; in the first two cases above, not being able to allocate an ADI does not mean that the substance is unsafe.
Obsolete for octan-1-ol-water partition coefficient See octan-1-ol-water partition coefficient
Small node or boss that is solid and can be detected by touch.
Maximum dose (of a substance) that produces no detectable changes under defined conditions of exposure. Note: This term tends to be substituted by no-observed-adverse-effect level (NOAEL) or no-observed-effect level (NOEL).
Change in the chemical or physical nature of a substance occurring as a result of physicochemical conditions and independent of any biological system.
subthreshold dose Amount of a substance that has no effect on the organism. Note: It is lower than the threshold of harmful effect and is estimated while establishing the threshold of harmful effect.
Electromagnetic radiation of low energy that is not capable of causing ionization.
Environmental exposure outside the workplace to substances that are otherwise associated with particular work environments and (or) activities and processes that occur there.
See deterministic.
Organism affected by a pesticide although not the intended object of its use.
Greatest concentration or amount of a substance, found by experiment or observation, which causes no detectable adverse alteration of morphology, functional capacity, growth, development, or life span of the target organism under defined conditions of exposure.
Greatest concentration or amount of a substance, found by experiment or observation, that causes no alterations of morphology, functional capacity, growth, development, or life span of target organisms distinguishable from those observed in normal (control) organisms of the same species and strain under the same defined conditions of exposure.
Maximum dose of a substance at which no specified response is observed in a defined population and under defined conditions of exposure.
Associated with a hospital or infirmary, especially used of diseases that may result from treatment in such an institution.
- nucle-us (in cell biology) sing., -ei pl.
Compartment in the interphase eukaryotic cell bounded by a double membrane and containing the genomic DNA, with the associated functions of transcription and processing.
Lowest concentration of an air pollutant that can be considered objectionable.
Procedure for evaluating the dietary intake of a large number of people. Note 1: The accuracy of the method depends on the accuracy with which records of the food consumption can be established and the accuracy of the nutritional tables specifying the concentration of various nutrients, vitamins, essential, and non-essential substances including pesticide residues. Note 2: For each record of quantity of food consumed during a certain time period, the daily intake of the substance in question is calculated by multiplying the substance concentration in the food item (as obtained from the nutritional table) by the quantity of food consumed and dividing by the time of observation.
circadian Relating to or exhibiting a nychthemeron or 24-hour period.
Involuntary, rapid, rhythmic movement (horizontal, vertical, rotary, mixed) of the eyeball, usually caused by a disorder of the labyrinth of the inner ear or a malfunction of the central nervous system.
objective environment Actual physical, chemical, and social environment as described by objective measurements, such as noise levels in decibels and concentrations of air pollutants.
occupational environment Surrounding conditions at a workplace.
occupational exposure Experience of substances, intensities of radiation etc. or other conditions while at work.
occupational exposure limit (OEL Regulatory level of exposure to substances, intensities of radiation etc. or other conditions, specified appropriately in relevant government legislation or related codes of practice.
occupational exposure standard (OES
Level of exposure to substances, intensities of radiation etc. or other conditions considered to represent specified good practice and a realistic criterion for the control of exposure by appropriate plant design, engineering controls, and, if necessary, the addition and use of personal protective clothing. In GBR, health-based exposure limit defined under COSHH Regulations as the concentration of any airborne substance, averaged over a reference period, at which, according to current knowledge, there is no evidence that it is likely to be injurious to employees, if they are exposed by inhalation, day after day, to that concentration, and set on the advice of the HSE Advisory Committee on Toxic Substances. occupational hygiene Identification, assessment and control of physicochemical and biological factors in the workplace that may affect the health or well-being of those at work and in the surrounding community.
occupational medicine Specialty devoted to the prevention and management of occupational injury, illness and disability, and the promotion of the health of workers, their families, and their communities.
occupational safety and health See occupational hygiene
octanol-water partition coefficient Pow, Kow
Ratio of the solubility of a chemical in octanol divided by its solubility in water. Note: Measure of lipophilicity, used in the assessment of both the uptake and physiological distribution of organic chemicals and prediction of their environmental fate.
ocular Pertaining to the eye.
odds Ratio of the probability of occurrence of an event to that of non-occurrence, or the ratio of the probability that something is so, to the probability that it is not so.
odds ratio (OR, Θ cross-product ratio relative odds Quotient obtained by dividing one set of odds by another. The term “odds” or “odds ratio” is defined differently according to the situation under discussion. Consider the following notation for the distribution of a binary exposure and a disease in a population or a sample.
Exposed
Nonexposed
Disease
a
b
No disease
c
d
The odds ratio (cross-product ad-bc. Note 1: The exposure-odds ratio for a set of case control data is the ratio of the odds in favor of exposure among the cases (a-b) to the odds in favor of exposure among non-cases (c-d), which is equal to ad-(bc). With incident cases, unbiased subject selection, and a “rare” disease (say, under 2% cumulative incidence rate over the study period), ad-bc is an approximate estimate of the risk ratio. With incident cases, unbiased subject selection, and density sampling of controls, ad-bc is an estimate of the ratio of the person-time incidence rates (force of morbidity) in the exposed and unexposed. No rarity assumption is required for this. Note 2: The disease-odds (rate-odds) ratio for a cohort or cross section is the ratio of the odds in favor of disease among the exposed population (a-c) to the odds in favor of disease among the unexposed (b-d), which is equal to ad-bc and hence is equal to the exposure-odds ratio for the cohort or cross section. Note 3: The prevalence-odds ratio refers to an odds ratio derived cross sectionally, as, for example, an odds ratio derived from studies of prevalent (rather than incident) cases. Note 4: The risk-odds ratio is the ratio of the odds in favor of getting disease, if exposed, to the odds in favor of getting disease if not exposed. The odds ratio derived from a cohort study is an estimate of this.
odor threshold odour threshold odor detection threshold In principle, the lowest concentration of an odorant in the air that can be detected by a human being. Note: In practice, a panel of “sniffers” is often used, and the threshold taken as the concentration at which 50% of the panel can detect the odorant (although some workers have also used 100% thresholds). The odor concentration at the detection threshold may be defined as one odor unit.
oedema See edema
olf unit used to measure scent emission of people and objects; one olf is defined as the scent emission of an “average person”, a sitting adult that takes an average of 0.7 baths per day and whose skin has a total area of 1.8 m2; the scent emission of an object or person is measured by specially trained personnel comparing it to normed scents. Note: The olf should not be confused with the of unit of scent immission (as opposed to emission), the decipol which also takes into account the ventilation system’s air volume flow.
olfactometer Apparatus for testing the power of the sense of smell.
oligozoospermia Sperm concentration less than a reference value.
oliguria
Excretion of a diminished amount of urine in relation to fluid intake.
-omics, -omes Neologism referring to the fields of study in biology ending in the suffix -omics, such as genomics or proteomics: the related neologism -omes are the objects of study of the field such as the genome or proteome, respectively.
oncogene Gene that can cause neoplastic (see neoplasia) transformation of a cell; oncogenes are slightly changed equivalents of normal genes known as proto-oncogenes.
oncogenesis Production or causation of tumors.
oncogenic Capable of producing tumors in animals, either benign (non-cancerous) or malignant (cancerous).
one-compartment model
Kinetic model, where the whole body is thought of as a single compartment in which the substance distributes rapidly, achieving an equilibrium between blood and tissue immediately.
one-hit model
Dose-response model of the form
P =1 - e-bd
where P is the probability of cancer death from a continuous dose rate, d, and b is a constant.
onycholysis Loosening or detachment of the nail from the nail bed following some destructive process.
oogenesis Process of formation of the ovum (plural ova), the female gamete.
operon Complete unit of gene expression and regulation, including structural genes, regulator gene(s) and control elements in DNA recognized by regulator gene product(s).
ophthalmic Pertaining to the eye.
organ dose Amount of a substance or physical agent (radiation) absorbed by an organ.
organelle Microstructure or separated compartment within a cell that has a specialized function, for example ribosome, peroxisome, lysosome, Golgi apparatus, mitochondrion, nucleolus, nucleus.
organic carbon partition coefficient, Koc
Measure of the tendency for organic substances to be adsorbed by soil or sediment, expressed as:
Koc = (mass adsorbed substance) - (mass organic carbon)____
(mass concentration of absorbed substance)
The Koc is substance-specific and is largely independent of soil properties.
organoleptic Involving an organ, especially a sense organ as of taste, smell or sight.
osteo- Prefix meaning pertaining to bone.
osteodystrophy Abnormal development of bone.
osteogenesis Formation or development of bone.
osteomalacia Condition marked by softening of the bones (due to impaired mineralization, with excess accumulation of osteoid), with pain, tenderness, muscular weakness, anorexia and loss of weight, resulting from deficiency of vitamin D and calcium.
osteoporosis Significant decrease in bone mass with increased porosity and increased tendency to fracture.
ovicide Substance intended to kill eggs.
oxidative stress Adverse effects occurring when the generation of reactive oxygen species (ROS) in a system exceeds the system’s ability to neutralize and eliminate them; excess ROS can damage a cell’s lipids, protein or DNA.
Unduly rapid or throbbing heartbeat that is noted by a patient; it may be regular or irregular. Undue awareness by a patient of a heartbeat that is otherwise normal.
Loss or impairment of motor function.
Serious illness which is a consequence of consumption of toxic bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae containing saxitoxin or its derivatives. Note: Initially there is tingling, numbness and burning of the tongue and lips, which spreads to the face, neck, arms, fingertips, legs and toes and this is followed by weakness of the upper and lower limbs, loss of motor coordination and, in severe cases, paralysis.
Exposure of a worker’s family to substances carried from the workplace to the home. Exposure of visitors to substances in the workplace.
Of, relating to, or affecting the parasympathetic nervous system which stimulates digestive secretions, slows the heart, constricts the pupils of the eyes, and dilates blood vessels
Producing effects resembling those caused by interruption of the parasympathetic nerve; also called anticholinergic.
cholinomimetic Producing effects resembling those caused by stimulation of the parasympathetic nervous system.
Method of introducing substances into an organism avoiding the gastrointestinal tract (subcutaneously, intravenously, intramuscularly etc.).
Slight or incomplete paralysis.
paraesthesia Abnormal or unexplained tingling, pricking, or burning sensation on the skin.
General term used to describe airborne solid or liquid particles of all sizes. Note: The term aerosol is recommended to describe airborne particulate matter. Particlesin air, usually of a defined size and specified as PMn where n is the maximum aerodynamic diameter (usually expressed in μm) of at least 50% of the particles.
Concentration of a substance in one phase divided by the concentration of the substance in the other phase when the heterogeneous system of two phases is in equilibrium. Note 1: The ratio of concentrations (or, strictly speaking, activities) of the same molecular species in the two phases is constant at constant temperature. Note 2: The octanol-water partition coefficient is often used as a measure of the bioconcentration factor for modeling purposes.
Note 3: This term is in common usage in toxicology but is not recommended by IUPAC for use in chemistry and should not be used as a synonym for partition constant, partition ratio or distribution ratio.
Ratio of the concentration of a substance in a single definite form, A, in the extract to its concentration in the same form in the other phase at equilibrium, e.g. for an aqueous-organic system: KD(A) = (A)orgc-(A)caq
Device for taking samples of environmental media following diffusional contact with a suitable collecting material. See personal sampler
Inhalation of sidestream smoke by people who do not smoke themselves. See also sidestream smoke
Test for allergic sensitivity in which a suspected allergen is applied to the skin on a small surgical pad. Note: Patch tests may be used to detect exposure to pesticides.
See maximum average daily concentration of an atmospheric pollutant
Action of entering or passing through a cell membrane. Ability or power to enter or pass through a cell membrane.
perceived risk See subjective environment
Through the skin following application on the skin.
Act of pouring over or through, especially the passage of a fluid through the vessels of a specific organ. Liquid poured over or through an organ or tissue.
Relating to the period shortly before and after birth, usually from the twentieth to the twenty-ninth week of gestation to one to four weeks after birth.
Method of artificial detoxication in which a toxic substance from the body is transferred into liquid that is instilled into the peritoneum. Note: Effectively this represents the employment of the peritoneum surrounding the abdominal cavity as a dialysing membrane for the purpose of removing waste products or toxins accumulated as a result of renal failure.
Ability or power to enter or pass through a cell membrane.
Quantity defining the permeability of molecules across a cell membrane and expressed as:
where K is the partition coefficient, D is the diffusion coefficient, and Δx is the thickness of the cell membrane. Note: SI units m s-1; frequently-used units cm s-1, with units cm2 s-1 for D, cm for Δx.
Of a membrane, allowing a given substance to pass through. Note: When applied to nonbiological membranes with no qualification, the term normally refers to water.
Action of entering or passing through a cell membrane.
Recommendation by US OSHA for a TWA concentration that must not be exceeded during any 8-hour work shift of a 40h working week.
Organelle, similar to a lysosome, characterized by its content of catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7) and other oxidative enzymes.
Attribute of a substance that describes the length of time that the substance remains in a particular environment before it is physically removed or chemically or biologically transformed.
Inorganic substance that is stable in the environment, is liable to long-range transport, may bio-accumulate in human and animal tissue, and may have significant impacts on human health and the environment. Note 1: Examples are arsenides, fluorides, cadmium salts and lead salts. Note 2: Some inorganic chemicals, like crocidolite asbestos, are persistent in almost all circumstances, but others, like metal sulfides, are persistent only in unreactive environments; sulfides can generate hydrogen sulfide in a reducing environment or sulfates and sulfuric acid in oxidizing environments. As with organic substances, persistence is often a function of environmental properties.
Organic chemical that is stable in the environment, is liable to long-range transport, may bio-accumulate in human and animal tissue, and may have significant impacts on human health and the environment. Examples: dioxin, PCBs, DDT, tributyltin oxide (TBTO). Note: The Stockholm Convention on Persistent Organic Pollutants was adopted at a Conference of Plenipotentiaries held from 22 to 23 May 2001 in Stockholm, Sweden; by signing this convention, governments have agreed to take measures to eliminate or reduce the release of POPs into the environment.
Type of environmental monitoring in which an individual's exposure to a substance is measured and evaluated. Note: This is normally carried out using a personal sampler.
See personal protective equipment
individual protective device (IPD) personal protective device (PPD) Equipment (clothing, gloves, hard hat, respirator and so on) worn by an individual to prevent exposure to a potentially toxic substance
individual sampler Compact, portable instrument for individual air sampling, measuring, or both, the content of a harmful substance in the respiration zone of a working person. See also passive sampler
Organism that may harm public health, that attacks food and other materials essential to mankind, or otherwise affects human beings adversely.
A substance intended to kill pests. Note: In common usage, any substance used for controlling, preventing, or destroying animal, microbiological or plant pests.
Any substance or mixture of substances found in man or animals or in food and water following use of a pesticide: the term includes any specified derivatives, such as degradation and conversion products, metabolites, reaction products and impurities considered to be of toxicological significance.
Process by which particulate material is endocytosed by a cell.
See also endocytosis, pinocytosis
Medicinal drug.
Process of interaction of pharmacologically active substances with target sites in living systems, and the biochemical and physiological consequences leading to therapeutic or adverse effects.
Study of the influence of genetic factors on the effects of drugs on individual organisms.
Methods and science permitting identification of the genes which influence individual variation in the efficacy or toxicity of therapeutic agents, and the application of this information in clinical practice.
Process of the uptake of drugs by the body, the biotransformation they undergo, the distribution of the drugs and their metabolites in the tissues, and the elimination of the drugs and their metabolites from the body. Study of such processes.
Science of the use and effects of drugs: may be subdivided into pharmacokinetics and pharmacodynamics defined above.
Throat, the part of the digestive tract between the esophagus below and the mouth and nasal cavities above and in front.
Enzymic modification of a substance by oxidation, reduction, hydrolysis, hydration, dehydrochlorination or other reactions catalysed by enzymes of the cytosol, of the endoplasmic reticulum (microsomal enzymes) or of other cell organelles. See also cytochrome P450
Binding of a substance, or its metabolites from a phase I reaction, with endogenous molecules (conjugation), making more water-soluble derivatives that may be excreted in the urine or bile. Note: Phase II reactions include glucuronidation, sulfation, acetylation, amino acid (e.g., glycine) and glutathione conjugation.
Further metabolism of conjugated metabolites produced by phase II reactions.
Complete phenotypic description of an organism (by analogy with genome).
Observable structural and functional characteristics of an organism determined by its genotype and modulated by its environment.
See feromone
Inflammation of the skin caused by exposure to light, especially that due to metabolites formed in the skin by photolysis.
Cleavage of one or more covalent bonds in a molecular entity resulting from absorption of light, or a photochemical process in which such cleavage is an essential part. Note: Term often used incorrectly to describe irradiation of a sample, although in the combination flash photolysis this usage is accepted.
Oxidation reactions induced by light. Common processes are: (1) Loss of one or more electrons from a chemical species as a result of photoexcitation of that species; (2) Reaction of a substance with oxygen under the influence of ultraviolet, visible, or infrared light. When oxygen remains in the product this latter process is also called photooxygenation. Reactions in which neither the substrate nor the oxygen are electronically excited (i.e., photosensitized oxidations) are sometimes called photoinitiated oxidations.
Abnormal visual intolerance of light.
Allergic reaction (see allergy) due to a metabolite formed by the influence of light.
Adverse effects produced by exposure to light energy, especially those produced in the skin.
Map showing how much DNA, measured in base pairs, separates two genes. Note: Not to be confused with a genetic map which shows the position of genes in relation to each other, based on the frequency of crossing overs.
See bioavailability
See physiologically-based pharmacokinetic modeling
toxicologically based pharmacokinetic modeling (TBPK) Mathematical modeling of kinetic behavior of a substance, based on measured physiological parameters.
Type of endocytosis in which soluble materials are taken up by the cell and incorporated into vesicles for digestion.
Substance intended to kill fish.
See critical study
Formation of a placenta in the uterus. Type or structure of a placenta. In botany, arrangement of placentas within the plant ovary.
Fluid component of blood in which the blood cells and platelets are suspended. Fluid component of semen produced by the accessory glands, the seminal vesicles, the prostate, and the bulbo-urethral glands. Cell substance outside the nucleus, i.e. the cytoplasm.
Removal of blood from the body and centrifuging it to obtain plasma and packed red blood cells: the blood cells are resuspended in a physiologically compatible solution (usually type-specific fresh frozen plasma or albumin) and returned to the donor or injected into a patient who requires blood cells rather than whole blood.
Autonomous self-replicating extra-chromosomal circular DNA molecule present in bacteria and yeast. Note 1: Plasmids replicate autonomously each time a bacterium divides and are transmitted to the daughter cells. Note 2: DNA segments are commonly cloned using plasmid vectors. After
Lining of the lung.
Term indicating the number of sets of chromosomes present in an organism.
saturnism Chronic poisoning caused by absorption of lead or lead salts.
Usually fibrosis of the lungs that develops owing to (prolonged) inhalation of inorganic or organic dusts. Note: Cause-specific types of pneumoconiosis are:
anthracosis: from coal dust. asbestosis: from asbestos dust. byssinosis: from cotton dust. siderosis: from iron dust. silicosis: from silica dust. stannosis: from tin dust.
Inflammation of the lung.
Reaction that changes a single base pair in DNA.
Single emission source in a defined location.
Substance that, taken into or formed within the organism, impairs the health of the organism and may kill it.
Containing a poison.
intoxication Morbid condition produced by a poison.
Any undesirable solid, liquid or gaseous matter in a solid, liquid or gaseous environmental medium. Note 1: ‘Undesirability’ is often concentration-dependent, low concentrations of most substances being tolerable or even essential in many cases. Note 2: A primary pollutant is one emitted into the atmosphere, water, sediments or soil from an identifiable source. Note 3: A secondary pollutant is a pollutant formed by chemical reaction in the atmosphere, water, sediments, or soil.
Introduction of pollutants into a solid, liquid, or gaseous environmental medium, the presence of pollutants in a solid, liquid, or gaseous environmental medium, or any undesirable modification of the composition of a solid, liquid or gaseous environmental medium.
Antibody produced by a number of different cell types.
Chronic excessive thirst.
Technique by which specific DNA segments are amplified selectively using cycles of annealing, chain extension, and thermal dissociation. After
Interindividual variations in metabolism of endogenous and exogenous compounds due to genetic influences, leading to enhanced side effects or toxicity of drugs (for example, poor versus fast metabolizers) or to different clinical effects (metabolism of steroid hormones).
Excessive production and discharge of urine.
Totality of related items under consideration. Note 1: A clearly defined part of a population is called a subpopulation. The term ‘population segment’ is sometimes used as a synonym for subpopulation. Note 2: In the case of a random variable, the probability distribution is considered as defining the population of that variable.
Assemblage of individuals with defined characteristics.
Persons who can and may develop an adverse health effect and who are potentially exposed to a substance under study. People already having chronic disease are excluded from the population at risk in studies of the incidence of the adverse effect.
Concentration of a substance in the critical organ at which a specified percentage of the exposed population has reached the individual critical organ concentration. Note: The percentage is indicated by PCC-10 for 10%, PCC-50 for 50% etc. (similar to the use of the term LD50).
Absolute number or incidence rate of cases occurring in a group of people.
See societal risk
Disturbance of porphyrin metabolism characterized by increased formation, accumulation, and excretion of porphyrins and their precursors.
Natural pigment containing a fundamental skeleton of four pyrrole nuclei united through the α-positions by four methine groups to form a macrocyclic structure (porphyrin is designated porphine in Chemical Abstracts indexes).
Pharmacological study of the choice of appropriate dose of a drug in relation to the physiological factors, such as age, that may influence its effect.
Processes by which proteins are biochemically modified within a cell following their synthesis in the ribosomes.
Expression of relative toxicity of an agent as compared to a given or implied standard or reference.
Dependent action in which a substance or physical agent at a concentration or dose that does not itself have an adverse effect enhances the harm done by another substance or physical agent. See also synergism
Numerically specified low risk of exposure to a potentially toxic substance (for example, 1 in 1000) or socially acceptable low risk of adverse effects from such an exposure applied to decision making in regard to chemical safety.
Approach to risk management that can be applied in circumstances of scientific uncertainty, reflecting a perceived need to take action in the face of a potentially serious risk without waiting for definitive results of scientific research. Note: The 1992 Rio Declaration on Environment and Development says: “In order to protect the environment, the precautionary approach shall be widely applied by states according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”
Closeness of agreement between indications obtained by replicate measurements on the same or similar objects under specified conditions. Note: Measurement precision is usually expressed numerically by measures of imprecision, such as standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Pertaining to the region over the heart and lower thorax.
Substance from which another, usually more biologically active, substance is formed.
predicted exposure concentration See estimated environmental concentration
Concentration that is expected to cause no adverse effect to any naturally occurring population in an environment at risk from exposure to a given substance.
Reliability of a measurement expressed in terms of its ability to predict the criterion: an example would be an academic aptitude test that was validated against subsequent academic performance.
Percentage of positive results that are true positives or of negative results that are true negatives.
Follicular depletion by the age of 35 years.
Before the formation of a tumor.
Number of instances of existing cases of a given disease or other condition in a given population at a designated time; sometimes used to mean prevalence rate. Note: When used without qualification, refers usually to the situation at a specified time (point prevalence).
Total number of individuals who have an attribute or disease at a particular time (or during a particular period) divided by the population at risk of having the attribute or disease at this point in time or midway through the period.
See pollutant
Concept in law and medicine which states that before one is subjected to a risk, especially a risk of bodily harm, one is entitled to be fully informed well in advance of the nature of that risk in order to make an informed decision about whether to accept it or not.
Accepted maximum level of a pollutant (or its indicator) in the target organism, or some part thereof, or an accepted maximum intake of a pollutant or nuisance into the target under specified circumstances.
Probability unit obtained by adding 5 to the normal deviates of a standardized normal distribution of results from a dose response study. Note 1: Addition of 5 removes the complication of handling negative values. Note 2: A plot of probit against the logarithm of dose or concentration gives a linear plot if the response follows a logarithmic normal distribution. Estimates of the LD50 and ED50 (or LC50 and EC50) can be obtained from this plot.
Substance that has to be metabolized before it becomes a carcinogen.
Precursor converted to an active form of a drug within the body.
Increase in the size of a tumor or spread of cancer in the body.
Unicellular organism, characterized by the absence of a membrane-enclosed nucleus. Note: Prokaryotes include bacteria, blue-green algae and mycoplasmas.
Sequence of nucleotides in a DNA molecule to which RNA polymerase binds so as to start transcription.
Agent that induces cancer when administered to an animal or human being who has been exposed to a cancer initiator.
Erroneous spelling of promoter (in molecular genetics), found in some literature.
Substance applied in a form that is not active as a pesticide and which becomes active once it enters an organism and undergoes chemical modification.
Latent state of a phage genome in a lysogenic bacterium.
Proportion of observed deaths from a specified condition in a defined population divided by the proportion of deaths expected from this condition in a standard population, expressed either
Nonprotein entity essential for an enzyme’s activity and tightly bound to the enzyme molecule in its active form.
Excretion of excessive amounts of protein (derived from blood plasma or kidney tubules) in the urine.
Description of the complete set of proteins encoded by the genome.
Global analysis of gene expression using a variety of techniques to identify and characterize proteins. Note: It can be used to study changes caused by exposure to chemicals and to determine if changes in mRNA expression correlate with changes in protein expression: the analysis may also show changes in post-translational modification, which cannot be distinguished by mRNA analysis alone.
Intake for a substance derived by applying a thousandfold uncertainty factor to the lowest low-effect level for noncarcinogenic endpoints.
Apparent adaptation of an organism to changing conditions of the environment (especially chemical) associated with stresses in biochemical systems that exceed the limits of normal (homeostatic) mechanisms. Note: Essentially there is a temporary concealed pathology that later on can be manifested in the form of explicit pathological changes sometimes referred to as ‘decompensation’.
Any major mental disorder characterized by derangement of the personality and loss of contact with reality.
Exerting an effect upon the mind and capable of modifying mental activity.
Applying risk assessment to a specific target population of known size, giving as the end product a quantitative statement about the number of people likely to be affected in a particular population.
Pertaining to the lung(s).
See laxative
Condition in which the temperature of a human being or mammal is above normal.
Any substance that produces fever.
All those planned and systematic actions necessary to provide adequate confidence that a product or service will satisfy given requirements for quality.
Operational techniques and activities that are used to fulfill requirements for quality. In toxicology, procedures incorporated in experimental protocols to reduce the possibility of error, especially human error. Note: This is a requirement of good laboratory practice.
Describing a condition that can be expressed only as occurring or not occurring, such as death.
- quantal effect
all-or-none effect antonym graded effect Condition that can be expressed only as ‘occurring’ or ‘not occurring’, such as death or occurrence of a tumor.
- quantitative structure-activity relationship (QSAR
Quantitative structure-biological activity model derived using regression analysis and containing as parameters physicochemical constants, indicator variables or theoretically calculated values. Note: The term is extended by some authors to include chemical reactivity, i.e. activity and reactivity are regarded as synonyms. This extension is discouraged.
- (quantitative structure metabolism relationship (QSMR
Quantitative association between the physicochemical and (or) the structural properties of a substance and its metabolic behavior.
Power emitted, transferred or received as radiation.
Scientific study involving research, education, prevention and treatment of diseases caused by ionizing or nonionizing radiation.
See crepitations
antonym biased sample Subset of units of a population that is arrived at by selecting units such that each possible unit has a fixed and known probability of selection.
Measure of the frequency with which an event occurs in a defined population in a specified period of time. Note 1: Most such rates are ratios, calculated by dividing a numerator, e.g. the number of deaths, or newly occurring cases of a disease in a given period, by a denominator, e.g. the average population during that period. Note 2: Some rates are proportions, i.e. the numerator is contained within the denominator (as when a number of patients with a given disease is divided by the total population from which they come).
rate coefficient Numerical constant in a rate-of-reaction (v) equation; for example, v = k (A)a(B)b.......where (A), (B) etc. are reactant concentrations, k is the rate constant, and a, b, etc. are corresponding empirical constants. Note: For further consideration of the relevant mathematics, see
rate-determining step rate-limiting step In a reaction occurring by a composite reaction sequence, an elementary reaction, the rate constant for which exerts a strong effect, - stronger than that of any other rate constant - on the overall rate. Note 1: It is recommended that the expressions rate-controlling, rate-determining and rate-limiting be regarded as synonymous, but some special meanings sometimes given to the last two expressions are considered under a separate heading. Note 2: For further consideration of this term, see .
Absolute difference between two rates. Note 1: For example, the difference in incidence rate between a population group exposed to a causal factor and a population group not exposed to the factor. Note 2: In comparisons of exposed and unexposed groups, the term ‘excess rate’ may be used as a synonym for rate difference.
Value obtained by dividing the rate in an exposed population by the rate in an unexposed population.
Substance intended to kill rats.
Absorption by a living organism of a substance which it has previously absorbed and then released, e.g., the uptake of a substance from the proximal renal tubule following glomerular filtration.
Radical nitrogen-based molecules that can act to facilitate nitrosylation reactions; reactive nitrogen species include dioxidonitrogen(•) (nitrogen dioxide, nitryl radical) NO2•, oxidonitrogen(•) (nitrogen monoxide, nitrosyl radical) NO• oxidonitrogen(1+) (nitrosyl cation) NO+, hydroxyoxidonitrogen (nitrous acid) HNO2 and oxidonitrate(1-) NO-.
Intermediates in the reduction of molecular dioxygen O2 to water. Note: Examples are superoxide anion O2-•, hydrogen peroxide H2O2, and hydroxyl radical HO•.
Arbitrary classification of substances that have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that such compounds will be rapidly and completely biodegraded in a wide variety of aerobic environments. See also biodegradation
Highest exposure that is reasonably expected to occur. Note: Typically the 95% upper confidence limit of the toxicant distribution is used: if only a few data points (6-10) are available, the maximum detected concentration is used.
Ability of a substance to remain in a particular environment in an unchanged form.
Molecular structure in or on a cell which specifically recognizes and binds to a compound and acts as a physiological signal transducer or mediator of an effect.
Endocytosis of a substance and its receptor following receptor binding.
Allele which in the heterozygous state is expected to have no effect on the phenotype of the organism which carries it. After
DNA made by transplanting or splicing DNA into the DNA of host cells in such a way that the modified DNA can be replicated in the host cells in a normal fashion.
Methods involving the use of restriction enzymes to cleave DNA at specific sites, allowing sections of DNA molecules to be inserted into plasmid or other vectors and cloned in an appropriate host organism (e.g. a bacterial or yeast cell). After
Highest allowable regulatory airborne concentration. Note: This exposure concentration is not expected to injure workers. It may be expressed as a ceiling limit or as a time-weighted average (TWA).
Restoration to original form of a substance previously for preservation and storage
Process leading to partial or complete restoration of a cell, tissue, organ or organism following its damage from exposure to a harmful substance or agent. Term used in analytical and preparative chemistry to denote the fraction of the total quantity of a substance recoverable following a chemical procedure.
Fraction or percentage of the total quantity of a substance extracted under specified conditions.
- (recycling (of waste
Process or method allowing for the recovery of some value from a waste, either as re-usable material or as energy.
An estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups which include children, asthmatics and the elderly) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Note: It can be derived from various types of human or animal data such as NOAEL, LOAEL, or benchmark concentration, with uncertainty factors generally applied to reflect limitations of the data used. It is generally used in EPA's noncancer health assessments.
Statistical distribution of reference values.
An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Note: It can be derived from a NOAEL, LOAEL, or benchmark dose, with uncertainty factors generally applied to reflect limitations of the data used. It is generally used in EPA's noncancer health assessments.
Person selected with the use of defined criteria for comparative purposes in a clinical study.
Area between and including two reference limits, for example the percentiles 2.5 and 97.5.
Boundary value defined so that a stated fraction of the reference values is less than or exceeds that boundary value with a stated probability.
calibration material standard material standard Material, sufficiently homogeneous and stable regarding one or more properties, used in calibration, in assignment of a value to another material, or in quality assurance.
Group of all reference individuals used to establish criteria against which a population that is being studied can be compared.
Selected reference individuals, statistically adequate numerically to represent the reference population.
Quantity value, generally accepted as having a suitably small measurement uncertainty, to be used as a basis for comparison with values of quantities of the same kind.
Terms referring to a reaction in which one direction of bond making or breaking occurs preferentially over all other possible directions. Note: Reactions are termed completely (100%) regioselective if the discrimination is complete, or partially (x%), if the product of reaction at one site predominates over the product of reaction at other sites.
Statistical methods for modeling a set of dependent variables, Y, in terms of combinations of predictors, X.
Term used by the USEPA to describe the expected dose resulting from human exposure to a substance at the level at which it is regulated in the environment.
DNA sequence to which specific proteins bind to activate or repress the expression of a gene.
Measure that can be used in comparison of adverse reactions to drugs, or other exposures, based solely on the component of risk due to the exposure or drug under investigation, removing the risk due to background exposure experienced by all in the population. The relative excess risk, R, is given by R = (R1-R0) - (R2-R0) where R1is the rate in the population, R2 is the rate in the comparison population, and R0is the rate in the general population. Note: Rate is used here as in epidemiology.
See odds ratio
risk ratio rate ratio
Ratio of the risk of disease or death among the exposed to the risk among the unexposed. Ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed.
Quantity of metabolizable substance divided by product of quantity of absorbed substance and exposure.
Giving a remedy. Removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water for the general protection of human health and the environment.
Anything, such as a medicine or therapy, that relieves pain, cures disease, or corrects a disorder.
Pertaining to the kidneys.
Volume of plasma passing through the kidneys in unit time.
See nephropathy
measurement repeatability Measurement precision under repeatability conditions of measurement.
repeatability condition of measurement Condition of measurement in a set of conditions including the same measurement procedure, same operator, same measuring system, same operating conditions and same location, and replicated measurements over a short period of time.
Substance used mainly to repel blood sucking insects in order to protect man and animals. Note: This term may also be used for substances used to repel mammals, birds, rodents, mites, plant pests, etc.
Act of taking multiple samples concurrently under comparable conditions. Note: Replicate sampling may be accomplished by taking samples adjacent in time or space.
Duplicated or repeated performance of an experiment under similar (controlled) conditions to reduce to a minimum the error, and to estimate the variations and thus obtain a more precise result: each determination, including the first is called a replicate. Process whereby the genetic material is duplicated.
measurement reproducibility Measurement precision under reproducibility conditions of measurement.
reproducibility condition of measurement Condition of measurement in a set of conditions including different locations, operators, and measuring systems. Note 1: The different measuring systems may use different measurement procedures. Note 2: A specification should give the conditions changed and unchanged, to the extent practical.
Substance or preparation that produces non-heritable adverse effects on male and female reproductive function or capacity and on resultant progeny.
Study of the nonheritable adverse effects of substances on male and female reproductive function or capacity and on resultant progeny.
Physiological or biochemical capacity that may be available to maintain homeostasis when the body or an organism is exposed to an environmental change.
Storage compartment from which a substance may be released with subsequent biological effects.
Health risk remaining after risk reduction actions are implemented.
Contaminant remaining in an organism or in other material such as food or packaging, following exposure.
Ability to withstand the effect of various factors including potentially toxic substances.
Process in which the components of some differentiated structure that has been produced by the body undergo lysis and assimilation. Note: Specifically in developmental toxicology, term applied to the lysis and assimilation of the fetus caused by chemical or biological stress of the pregnant mother.
Action of a substance after its re-absorption from the gut into the blood.
respirable particles Mass fraction of dust (particles) that penetrates to the unciliated airways of the lung (the alveolar region). Note: This fraction is represented by a cumulative log-normal curve having a median aerodynamic diameter of 4 μm, standard deviation 2 μm (values for humans).
Proportion of an exposed population with a defined effect or the proportion of a group of individuals that demonstrates a defined effect in a given time at a given dose rate.
Endonucleases which recognize specific base sequences within a DNA helix, creating a double-strand break of DNA. Note: Type I restriction enzymes bind to these recognition sites but subsequently cut the DNA at different sites. Type II restriction enzymes both bind and cut within their recognition or target sites.
Amount of a substance that is left from the total absorbed after a certain time following exposure. Holding back within the body or within an organ, tissue or cell of matter that is normally eliminated.
Research design used to test etiological hypotheses in which inferences about exposure to the putative causal factor(s) are derived from data relating to characteristics of the persons or organisms under study or to events or experiences in their past. Note: The essential feature is that some of the persons under study have the disease or other outcome condition of interest, and their characteristics and past experiences are compared with those of other, unaffected persons. Persons who differ in the severity of the disease may also be compared.
Enhancement of the dose-effect relationship for a poison following repeated exposure to decreasing doses.
- reverse mutation (back mutation)
Mutation in a mutant allele which makes it capable of producing the nonmutant phenotype; this may result from restoration of the original DNA sequence of the gene or from production of a new DNA sequence which has the same effect.
Process by which an RNA molecule is used as a template to make a single-stranded DNA copy.
Change from normal structure or function, induced by a substance or other agent(s), that returns to normal status or within normal limits after cessation of exposure.
Acute, fulminating, potentially lethal disease of skeletal muscle that causes disintegration of striated muscle fibers as evidenced by myoglobin in the blood and urine.
Inflammation of the nasal mucosa.
- rhonch-us sing., -i pl.)
Harsh crepitation in the throat, often resembling snoring.
Linear, usually single stranded, polymer of ribonucleotides, each containing the sugar ribose in association with a phosphate group and one of 4 nitrogenous bases: adenine, guanine, cytosine, or uracil. Note: RNA encodes the information for the sequence of amino-acids in proteins synthesized using it as a template.
Probability of adverse effects caused under specified circumstances by an agent in an organism, a population or an ecological system. Probability of a hazard causing an adverse effect. Expected frequency of occurrence of a harmful event arising from such an exposure. After
Identification and quantification of the risk resulting from a specific use or occurrence of a chemical or physical agent, taking into account possible harmful effects on individuals or populations exposed to the agent in the amount and manner proposed and all the possible routes of exposure. Note: Quantification ideally requires the establishment of dose-effect and dose-response relationships in likely target individuals and populations.
Global term for the whole process from hazard identification to risk management.
Probability of the occurrence of a specified undesirable event following exposure of an individual person from a given population to a specified substance at a defined level for the expected lifetime of the average member of that population.
Tendency of an individual person to avoid risk.
Outcome of hazard identification and risk estimation applied to a specific use of a substance or occurrence of an environmental health hazard. Note: Risk characterization requires quantitative data on the exposure of organisms or people at risk in the specific situation. The end product is a quantitative statement about the proportion of organisms or people affected in a target population.
Interpretation and communication of risk assessments in terms that are comprehensible to the general public or to others without specialist knowledge.
negligible risk risk that is negligible and too small to be of societal concern (usually assumed to be a probability below 10-5 or 10-6). Note 1: This term can also mean ‘virtually safe’. Note 2: In the USA, this is a legal term used to mean ‘negligible risk to the individual’.
Assessment, with or without mathematical modeling, of the probability and nature of effects of exposure to a substance based on quantification of dose-effect and dose-response relationships for that substance and the population(s) and environmental components likely to be exposed and on assessment of the levels of potential exposure of people, organisms and environment at risk.
Establishment of a qualitative or quantitative relationship between risks and benefits, involving the complex process of determining the significance of the identified hazards and estimated risks to those organisms or people concerned with or affected by them.
Recognition of a potential hazard and definition of the factors required to assess the probability of exposure of organisms or people to that hazard and of harm resulting from such exposure.
See risk marker
Decision-making process involving considerations of political, social, economic, and engineering factors with relevant risk assessments relating to a potential hazard so as to develop, analyse, and compare regulatory options and to select the optimal regulatory response for safety from that hazard. Note: Essentially risk management is the combination of three steps: risk evaluation; emission and exposure control; risk monitoring.
risk indicator Attribute that is associated with an increased probability of occurrence of a disease or other specified outcome and that can be used as an indicator of this increased risk. Note: A risk marker is not necessarily a causal factor.
Process of following up the decisions and actions within risk management in order to check whether the aims of reduced exposure and risk are achieved.
Subjective perception of the gravity or importance of the risk based on a person's knowledge of different risks and the moral, economic, and political judgment of their implications.
Word groups identifying potential health or environmental hazards required under CPL Directives (European Community); may be incorporated into Safety Data Sheets.
Ratio of predicted exposure concentration to predicted no effect concentration.
- predicted environmental concentration (PEC) predicted no effect concentration (PNEC
Note: The higher this value above one, the greater the risk. If the value is below one, there should be no risk as a result of the predicted exposure.
Value obtained by dividing the probability of occurrence of a specific effect in one group by the probability of occurrence of the same effect in another group, or the value obtained by dividing the probability of occurrence of one potentially hazardous event by the probability of occurrence of another. Note: Calculation of such ratios is used in choosing between options in risk management.
Amount of exposure corresponding to a specified level of risk.
Substance intended to kill rodents.
- (route of (exposure)
Means by which a toxic agent gains access to an organism by administration through the gastrointestinal tract (ingestion), lungs (inhalation), skin (topical), or by other routes such as intravenous, subcutaneous, intramuscular or intraperitoneal routes.
Supernatant fraction obtained from an organ (usually liver) homogenate by centrifuging at 9000 g for 20 minutes in a suitable medium; this fraction contains cytosol and microsomes.
Reciprocal of risk: practical certainty that injury will not result from a hazard under defined conditions. Note 1. Safety of a drug or other substance in the context of human health: the extent to which a substance may be used in the amount necessary for the intended therapeutic purpose with a minimum risk of adverse health effects. Note 2. Safety (toxicological): The high probability that injury will not result from exposure to a substance under defined conditions of quantity and manner of use, ideally controlled to minimize exposure.
Single page giving toxicological and other safety advice, usually associated with a particular preparation, substance or process.
Science directed to the discovery, development and safe therapeutic use of biologically active substances as a result of the identification, monitoring and characterization of potentially undesirable pharmacodynamic activities of these substances in nonclinical studies.
See natriuretic
Group of individuals often taken at random from a population for research purposes. One or more items taken from a population or a process and intended to provide information on the population or process. Portion of material selected from a larger quantity so as to be representative of the whole.
That part of the total error (the estimate from a sample minus the population value) associated with using only a fraction of the population and extrapolating to the whole, as distinct from analytical or test error. Note: Sampling error arises from a lack of homogeneity in the parent population.
Malignant tumor arising in a connective tissue and composed primarily of anaplastic cells resembling supportive tissue (see anaplasia).
Elimination that becomes concentration-independent at a concentration at which the elimination process is functioning maximally.
Pain in a joint resulting from lead poisoning.
plumbism Intoxication caused by lead.
Method for analysing data for freely reversible ligand-receptor binding interactions. Note: The graphical plot is (bound ligand)-(free ligand) against (bound ligand), with slope the negative reciprocal of the binding affinity and intercept on the x-axis the number of receptors.
Area of diminished or lost vision within the visual field, surrounded by an area of less affected or normal vision.
Hardening of an organ or tissue, especially that due to excessive growth of fibrous tissue.
Carrying out of a test or tests, examination(s) or procedure(s) in order to expose undetected abnormalities, unrecognized (incipient) diseases, or defects: examples are mass X-rays and cervical smears. Pharmacological or toxicological screening consists of a specified set of procedures to which a series of compounds is subjected to characterize pharmacological and toxicological properties and to establish dose-effect and dose-response relationships.
Decision limit or cut-off point at which a screening test is regarded as positive.
Product of biochemical processes other than the normal metabolic pathways, mostly produced in micro-organisms or plants after the phase of active growth and under conditions of nutrient deficiency.
See sidestreamsmoke
Intracellular effector substance increasing or decreasing as a result of the stimulation of a receptor by an agonist, considered as the ‘first messenger’.
secretion
Process by which a substance such as a hormone or enzyme produced in a cell is passed through a plasma membrane No Entry to the outside, for example the intestinal lumen or the blood (internal secretion). Solid, liquid or gaseous material passed from the inside of a cell through a plasma membrane to the outside as a result of cell activity.
Substance that exerts a soothing or tranquillizing effect.
- self-cleaning of water (in a reservoir)
Water purification by natural biological and physico-chemical processes.
Purification of the atmosphere from contaminants by natural biological and physico-chemical processes.
See subchronic
Substance produced by plants or animals, or a synthetic analogue thereof, that evokes a behavioral response in individuals of the producing species or other species (e.g. allomones, kairomones, pheromones, and synomones).
Membrane that will preferentially allow certain molecules or ions to pass through it while preventing the passage of others.
See sensitization
Quotient of the change in the indication and the corresponding change in the value of the quantity being measured.
Slope of the calibration curve. If the curve is in fact a ‘curve’, rather than a straight line, then of course sensitivity will be a function of analyte concentration or amount. If sensitivity is to be a unique performance characteristic, it must depend only on the chemical measurement process, not upon scale factors.
Extent (usually expressed as a percentage) to which a method gives results that are free from false negatives. Note 1: The fewer the false negatives, the greater the sensitivity. Note 2: Quantitatively, sensitivity is the proportion of truly diseased persons in the screened population who are identified as diseased by the screening test.
Immune response whereby individuals become hypersensitive to substances, pollen, dandruff, or other agents that make them develop a potentially harmful allergy when they are subsequently exposed to the sensitizing material (allergen).
Substance causing sensitization.
Intensity, where the detection threshold level is defined as the lower limit of the perceived intensity range (by convention the lowest concentration that can be detected in 50% of the cases in which it is present). Quality, where the recognition threshold level is defined as the lowest concentration at which the sensory effect can be recognized correctly in 50% of the cases. Acceptability and annoyance, where the nuisance threshold level is defined as the concentration at which not more than a small proportion of the population, less than 5%, experiences annoyance for a small part of the time, less than 2%. Note: Since annoyance will be influenced by a number of factors, a nuisance threshold level cannot be set on the basis of concentration alone.
Clear watery fluid especially that moistening the surface of serous membranes or that exuded through inflammation of any of these membranes.
blood serum Watery proteinaceous portion of the blood that remains after clotting.
Serious illness which is a consequence of consumption of bivalve shellfish (mollusks) such as mussels, oysters and clams that have ingested, by filter feeding, large quantities of micro-algae. See amnesic shellfish poisoning, diarrheal shellfish poisoning, neurologic shellfish poisoning, paralytic shellfish poisoning
See acute effect
Fifteen minute time weighted average (TWA) exposure recommended by ACGIH which should not be exceeded at any time during a workday, even if the 8-hour TWA is within the threshold limit value-time-weighted average, TLV-TWA. Note: Workers can be exposed to a maximum of four STEL periods per 8 hour shift, with at least 60 minutes between exposure periods.
See acute toxicity.
Action of a drug other than that desired for beneficial pharmacological effect.
Pneumoconiosis resulting from the inhalation of iron dust. Excess of iron in the urine, blood or tissues, characterized by hemosiderin granules in urine and iron deposits in tissues.
environmental tobacco smoke (ETS) secondhand smoke Cloud of small particles and gases that is given off from the end of a burning tobacco product (cigarette, pipe, cigar) between puffs and is not directly inhaled by the smoker. Note: This is the smoke that gives rise to passive inhalation on the part of bystanders.
Objective evidence of a disease, deformity or an effect induced by an agent, perceptible to an examining physician.
Molecular pathways through which a cell senses changes in its external or internal environment and changes its pattern of gene expression or enzyme activity in response. After
Pneumoconiosis resulting from inhalation of silica dust.
Procedure designed to predict the rate of biodegradation of a compound under relevant environmental conditions.
Single base variation at a chromosomal locus which exists stably within populations (typically defined as each variant form being present in at least 1-2% of individuals). After
In environmental chemistry, an area or part of the environment in which, or a process by which, one or more pollutants is removed from the medium in which it is dispersed. Note: For example - moist ground acts as a sink for sulfur dioxide in the air.
Reciprocal exchange of chromatin between two replicated chromosomes that remain attached to each other until anaphase of mitosis; used as a measure of mutagenicity of substances that produce this effect.
Osteosclerosis due to fluoride.
Substance intended to kill slime-producing organisms. Note: Used on paper stock, water cooling systems, paving stones etc.
slope factor Value, in inverse concentration or dose units, derived from the slope of a dose-response curve; in practice, limited to carcinogenic effects with the curve assumed to be linear at low concentrations or doses. Note: The product of the slope factor and the exposure is taken to reflect the probability of producing the related effect.
Total probability of harm to a human population including the probability of adverse effects to health of descendants and the probability of disruption resulting from loss of services such as industrial plant or loss of material goods and electricity.
Experimental ratio of a substance's concentration in the soil to that in the aqueous (dissolved) soil phase at equilibrium: it is valid only for the specific concentration and solid-solution ratio of the test. See also organic carbon partition coefficient
solvent sniffing Deliberate inhalation (or drinking) of volatile solvents, in order to become intoxicated.
See solvent abuse
Pertaining to the body as opposed to the mind. Pertaining to nonreproductive cells or tissues. Pertaining to the framework of the body as opposed to the viscera.
Substance producing sleep.
Noncommittal term used instead of adsorption or absorption when it is difficult to discriminate experimentally between these two processes.
Distribution of an element amongst defined chemical species in a system.
Analytical activities of identifying and (or) measuring the quantities of one or more individual chemical species in a sample.
In biological systematics, group of organisms of common ancestry that are able to reproduce only among themselves and that are usually geographically distinct. See chemical species
Quantitative or qualitative differences of response to the action(s) of a potentially toxic substance on various species of living organisms.
Quantitative and qualitative features of response to the action(s) of a potentially toxic substance that are characteristic for a particular species of living organism.
Death rate computed for a subpopulation of individual organisms or people having a specified characteristic or attribute, and named accordingly. Example: age-specific death rate, the number of deaths of persons of a specified age during a given period of time, divided by the total number of persons of that age in the population during that time.
Proportion of truly non-diseased persons who are identified by the screening test.
Describing an animal removed from its mother under sterile conditions just prior to term and subsequently reared and kept under sterile conditions.
Specifically selected portion of any substance, material, organism (specifically tissue, blood, urine or faeces) or environmental medium assumed to be representative of the parent substance etc. at the time it is taken for the purpose of diagnosis, identification, study or demonstration.
The radiant power at wavelength lambda (λ) per unit wavelength interval.
Processes through which introns are removed from a messenger RNA prior to translation and the exons joined.
Agent used in some pesticide formulations to extend the even disposition of the active ingredient.
Time required for the amount of a substance in a formulation to decrease, for any reason, by one-half (50%). See also half life, half time
That which is established as a measure or model to which others of a similar nature should conform.
technical directive Technical specification, usually in the form of a document available to the public, drawn up with the consensus or general approval of all interests affected by it, based on the consolidated results of science, technology and experience, aimed at the promotion of optimum community benefits and approved by a body recognized on the national, regional or international level.
See reference material, standard material
Making any substance, drug or other preparation conform to type or precisely defined characteristics. Establishment of precisely defined characteristics, or precisely defined methods, for future reference. Definition of precise procedures for administering, scoring and evaluating the results of a new method that is under development.
standard See reference material
Ratio of the number of deaths observed in the study group or population to the number of deaths that would be expected if the study population had the same specific rates as the standard population, multiplied by 100. Note: This ratio is usually expressed as a percentage.
Pneumoconiosis resulting from inhalation of tin dust.
State of a system in which the conditions do not change in time. Note: For further information, see .
Multipotent cell with mitotic potential that may serve as a precursor for many kinds of differentiated cells.
Chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereoisomeric) products in unequal amounts. Note: Traditionally called asymmetric synthesis.
Specificity of chemical reactivity of stereoisomers based on their three-dimensional molecular structure.
Pertaining to or arising from chance and hence obeying the laws of probability.
stochastic process Phenomenon pertaining to or arising from chance, and hence obeying the laws of probability.
Process of or result of separating a sample into several subsamples according to specified criteria such as age groups, socio-economic status, etc.
Subset of a population selected according to some important characteristic.
Chemical grouping which is known to be associated with a particular type of toxic effect, e.g. mutagenicity.
Association between specific aspects of molecular structure and defined biological action. See also quantitative structure-activity relationship
- (structure-metabolism relationship (SMR
Association between the physicochemical and (or) the structural properties of a substance and its metabolic behavior.
See subchronic
Repeated over a short period, usually about 10 % of the life span; an imprecise term used to describe exposures of intermediate duration.
Biological change resulting from an environmental alteration lasting about 10 % of the lifetime of the test organism. Note: In practice with experimental animals, such an effect is usually identified as resulting from multiple or continuous exposures occurring over 3 months (90 days). Sometimes a subchronic effect is distinguished from a subacute effect on the basis of its lasting for a much longer time.
Animal experiment serving to study the effects produced by the test substance when administered in repeated doses (or continually in food, drinking-water, air) over a period of up to about 90 days.
Biological change with detectable symptoms following exposure to an agent known to cause disease either before symptoms of the disease occur or when they are absent.
Fertility below the normal range for a given species.
perceived environment Surrounding conditions as perceived by persons living in these conditions.
Substance material on which an enzyme acts. Surface on which an organism grows or to which is attached.
See diaphoretic
According to the USEPA's Guidelines for Carcinogen Risk Assessment, sufficient evidence is a collection of facts and scientific references that is definite enough to establish that an adverse effect is caused by the agent in question.
Maximum dose or concentration that on current understanding is likely to be tolerated by an exposed organism without producing any harm.
Formation of irreversible cleavage complexes (also referred to as ‘suicide complexes’) leading to cell death.
Two-to-four page summary of a risk assessment.
Process of addition of separate postsynaptic responses caused by stimuli that are adjacent in time and space. Note: Excitation of a synapse evokes a graded potential change in the postsynaptic membrane that may be below the threshold required to trigger an impulse. If two or more such potentials are caused either nearly simultaneously, at different synapses on the same neuron (spatial summation), or in rapid succession at the same synapse (temporal summation), the summed response may be sufficient to trigger a postsynaptic impulse. Summation may occur between excitatory potentials, inhibitory potentials, or between an excitatory and an inhibitory potential.
Federal authority, established by the US Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) in 1980, to respond directly to releases or threatened releases (such as from landfills or waste disposal areas) of hazardous substances that may endanger health or welfare.
Enzymatic antioxidant that removes the potentially toxic superoxide ion (O2- ) by disproportionating it to O2 and hydrogen peroxide (H2O2).
See toxic dose
Region of space comprising and adjoining the phase boundary between a solid and liquid phase, between a solid and gas phase, or between a liquid and gas phase within which properties of matter are significantly different from the values in the adjoining bulk phases.
Relatively well studied toxicant whose properties are assumed to apply to an entire chemically and toxicologically related class; for example, benzo(a)pyrene data may be used as toxicologically equivalent to that for all carcinogenic polynuclear aromatic hydrocarbons.
Systematic ongoing collection, collation, and analysis of data and the timely dissemination of information to those who need to know in order that action can be taken to initiate investigative or control measures.
vulnerable Describing a group of organisms more vulnerable to a given exposure than the majority of the population to which they belong. Note: Susceptibility may reflect gender, age, physiological status, or genetic constitution of the organisms at risk.
See biomarker of susceptibility
Condition of lacking the power to resist a particular disease or infection; thus in susceptible people ‘normal expected’ results occur but with a lower exposure (or dose) than in the rest of the population.
anti-adrenergic
adj., Blocking transmission of impulses from the adrenergic (sympathetic) postganglionic fibers to effector organs or tissues. n., Agent that blocks transmission of impulses from the adrenergic (sympathetic) postganglionic fibers to effector organs or tissues.
adrenergic
adj., Producing effects resembling those of impulses transmitted by the postganglionic fibers of the sympathetic nervous system. n., Agent that produces effects resembling those of impulses transmitted by the postganglionic fibers of the sympathetic nervous system.
Any subjective evidence of a disease or an effect induced by a substance as perceived by the affected subject.
General description of all of the signs and symptoms of exposure to a toxicant Note: Signs are the overt (observable) responses associated with exposure (such as convulsions, death, etc.) whereas symptoms are covert (subjective) responses (such as nausea, headache, etc.).
Functional junction between two neurons, where a nerve impulse is transmitted from one neuron to another.
See synapse
Set of signs and symptoms occurring together and often characterizing a particular disease-like state.
synergistic effect synergy (in toxicology Pharmacological or toxicological interaction in which the combined biological effect of exposure to two or more substances is greater than expected on the basis of the simple summation of the effects of each of the individual substances.
Substance which contributes more than additively to a mutual effect with another substance.
See synergism
See synergism
Semiochemical that is produced by one organism inducing a response in an organism of another species that is favorable to both the emitter and the responding organism. See allomone, kairomone
Property of genes which reside on the same chromosome.
Subset selected according to some simple rule such as specified date or alphabetic classification.
Relating to the body as a whole. Occurring at a site in the body remote from the point of contact with a substance. After
Consequence that is either of a generalized nature or that occurs at a site distant from the point of entry of a substance. Note: A systemic effect requires absorption and distribution of the substance in the body.
Study of the mechanisms underlying complex biological processes as integrated systems of many, diverse, interacting components. Note: It involves (1) collection of large sets of experimental data (by high-throughput technologies and-or by mining the literature of reductionist molecular biology and biochemistry), (2) proposal of mathematical models that might account for at least some significant aspects of this data set, (3) accurate computer solution of the mathematical equations to obtain numerical predictions, and (4) assessment of the quality of the model by comparing numerical simulations with the experimental data.
Prefix meaning rapid as in tachycardia and tachypnoea.
antonym bradycardia Abnormally fast heartbeat.
antonym bradypnoea Abnormally fast breathing.
Substance intended to kill tapeworms.
- target (in biology
Any organism, organ, tissue, cell or cell constituent that is subject to the action of an agent.
- target population (in epidemiology
Collection of individuals, items, measurements, etc. about which inferences are required: the term is sometimes used to indicate the population from which a sample is drawn and sometimes to denote any reference population about which inferences are needed. Group of persons for whom an intervention is planned.
See T lymphocyte
- technical directive
See standard
Structure which terminates the arm of a chromosome. Note: A similar term ‘telomer’, with a different meaning is found in the IUPAC Gold Book
- temporary acceptable daily intake
Value for the acceptable daily intake proposed for guidance when data are sufficient to conclude that use of the substance is safe over the relatively short period of time required to generate and evaluate further safety data, but are insufficient to conclude that use of the substance is safe over a lifetime. Note: A higher-than-normal safety factor is used when establishing a temporary ADI and an expiration date is established by which time appropriate data to resolve the safety issue should be available.
- temporary maximum residue limit
Regulatory value established for a specified, limited time when only a temporary acceptable daily intake has been established for the pesticide concerned or, with the existence of an agreed acceptable daily intake, the available residue data are inadequate for firm maximum residue recommendations.
Agent that, when administered prenatally (to the mother), induces permanent structural malformations or defects in the offspring.
Potential to cause the production of nonheritable structural malformations or defects in offspring. Production of nonheritable structural malformations or defects in offspring.
Study of malformations, monstrosities or serious deviations from normal development in organisms.
- testing of chemicals
In toxicology, evaluation of the therapeutic and potentially toxic effects of substances by their application through relevant routes of exposure with appropriate organisms or biological systems so as to relate effects to dose following application. In chemistry, qualitative or quantitative analysis by the application of one or more fixed methods and comparison of the results with established standards.
Pertaining to tetanus, characterized by tonic muscle spasm.
- theoretical maximum daily intake (TMDI
Predicted maximum daily intake of a residue, assuming that it is present at the maximum residue level and that average daily consumption of foods per person is represented by assessed regional diets: it is expressed in milligrams of residue per person per day. After
Generation and manipulation of stem cells with the objective of deriving cells of a particular organ or tissue to treat a disease.
- therapeutic index
Ratio between toxic and therapeutic doses (the higher the ratio, the greater the safety of the therapeutic dose).
- three-dimensional quantitative structure-activity relationship (3D-QSAR
Quantitative association between the three-dimensional structural properties of a substance and its biological properties.
See quantitative structure-activity relationship
Dose or exposure concentration below which a defined effect will not occur. See also critical effect
- threshold concentration
See threshold
- threshold dose
See threshold
- threshold limit value-ceiling (TLV-C
As defined by ACGIH, concentration of a potentially toxic substance that should not be exceeded during any part of the working exposure.
- threshold limit value-short term exposure limit (TLV-STEL
As defined by ACGIH, concentration to which it is believed that workers can be exposed continuously for a short period of time without suffering from 1) irritation, 2) chronic or irreversible tissue damage, or 3) narcosis of sufficient degree to increase the likelihood of accidental injury, impair self rescue or materially reduce work efficiency, and provided that the daily TLV-TWA is not exceeded. Note: It is not a separate independent exposure guideline; rather, it supplements the TLV-TWA limit where there are recognized acute effects from a substance whose toxic effects are primarily of a chronic nature. TLV-STELs are recommended only where toxic effects have been reported from high short-term exposures in either humans or animals.
- threshold limit value-time-weighted average (TLV-TWA
As defined by ACGIH, time-weighted average concentration for a conventional 8-hour workday and a 40-hour workweek, to which it is believed nearly all workers may be repeatedly exposed, day after day, without adverse effect.
- threshold of toxicological concern (TTC
Human exposure threshold value for a group of chemicals below which there should be no appreciable risk to human health.
Decrease in the number of blood platelets (thrombocytes).
Condition resulting from excessive concentrations of thyroid hormones, as in hyperthyroidism, characterized by bulging eyes and rapid heart rate.
- tidal volume
Quantity of air or test gas that is inhaled and exhaled during one respiratory cycle.
- time-weighted-average-exposure (TWAE), or concentration (TWAC
Concentration in the exposure medium at each measured time interval multiplied by that time interval and divided by the total time of observation. Note: For occupational exposure a working shift of eight hours is commonly used as the averaging time.
Continual noise in the ears, such as ringing, buzzing, roaring, or clicking.
- tissue dose
Amount of a substance or physical agent (radiation) absorbed by a tissue.
- tissue-plasma partition coefficient
See partition ratio
Animal cell which possesses specific cell surface receptors through which it binds to foreign substances or organisms, or those which it identifies as foreign, and which initiates immune responses.
- tolerable daily intake (TDI
Estimate of the amount of a potentially harmful substance (e.g. contaminant) in food or drinking water that can be ingested daily over a lifetime without appreciable health risk. Note 1: For regulation of substances that cannot be easily avoided, a provisionally tolerable weekly intake (PTWI) may be applied as a temporary limit. Note 2: Acceptable Daily Intake is normally used for substances not known to be harmful, such as food additives.
- tolerable risk
Probability of suffering disease or injury that can, for the time being, be tolerated, taking into account the associated benefits, and assuming that the risk is minimized by appropriate control procedures.
- tolerable weekly intake (TWI
Estimate of the amount of a potentially harmful substance (e.g. a contaminant) in food or drinking water that can be ingested weekly over a lifetime without appreciable health risk.
Adaptive state characterized by diminished effects of a particular dose of a substance: the process leading to tolerance is called “adaptation”. In food toxicology, dose that an individual can tolerate without showing an effect. Ability to experience exposure to potentially harmful amounts of a substance without showing an adverse effect. Ability of an organism to survive in the presence of a toxic substance: increased tolerance may be acquired by adaptation to constant exposure. In immunology, state of specific immunological unresponsiveness.
Characterized by tension, especially muscular tension. Medical preparation that increases or restores normal muscular tension.
- topical (in medicine
Applied directly to the surface of the body.
- topical effect
Consequence of application of a substance to the surface of the body which occurs at the point of application.
- torsade (de pointes
potentially lethal form of ventricular tachycardia following chronic abuse of alcohol and mainly due to hypomagnesemia.
- total diet study
Study designed to establish the pattern of pesticide residue intake by a person consuming a defined diet. Study undertaken to show the range and amount of various foodstuffs in the typical diet or to estimate the total amount of a specific substance in a typical diet.
- total terminal residue (of a pesticide
Summation of levels of all the residues of a defined pesticide in a food. See also residue After
- toxemia (blood poisoning)
Condition in which the blood contains toxins produced by body cells at a local source of infection or derived from the growth of microorganisms. Pregnancy-related condition characterized by high blood pressure, swelling and fluid retention, and proteins in the urine.
Able to cause injury to living organisms as a result of physicochemical interaction.
See toxic substance
- toxic chemical
See toxic substance
- toxic dose
super-threshold dose Amount of a substance which produces intoxication without lethal outcome.
Capacity to cause injury to a living organism defined with reference to the quantity of substance administered or absorbed, the way in which the substance is administered and distributed in time (single or repeated doses), the type and severity of injury, the time needed to produce the injury, the nature of the organism(s) affected and other relevant conditions. Adverse effects of a substance on a living organism defined as in 1. Measure of incompatibility of a substance with life: this quantity may be expressed as the reciprocal of the absolute value of median lethal dose (1-LD50) or concentration (1-LC50).
- toxicity equivalency factor (TEF, f
Ratio of the toxicity of a chemical to that of another structurally related chemical (or index compound) chosen as a reference.
- toxicity equivalency factor (in risk assessment) (TEF), f
Ratio of the toxicity of a chemical to that of another structurally related chemical (or index compound) chosen as a reference. Factor used to estimate the toxicity of a complex mixture, commonly a mixture of chlorinated dibenzo-p-dioxins (oxanthrenes), furans, and biphenyls: in this case, TEF is based on relative toxicity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetrachlorooxanthrene) for which the f = 1.
Contribution of a specified component (or components) to the toxicity of a mixture of related substances. Note 1: The amount-of-substance (or substance) concentration of total toxicity equivalent is the sum of that for the components B, C … N. Note 2: Toxicity equivalent is most commonly used in relation to the reference toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetrachlorooxanthrene) by means of the toxicity equivalency factor (TEF, f) which is 1 for the reference substance. Hence, where c is the amount-of-substance concentration:
- toxicity exposure ratio (TER
Ratio of the measure of the effects (e.g., LD50, LC50, NOEC) to the estimated exposure. Note: It is the reciprocal of a risk quotient or hazard quotient.
- toxicity test
Experimental study of the adverse effects of exposure of a living organism to a substance for a defined duration under defined conditions.
- toxic material
See toxic substance
chemical etiologic agent poison toxicant toxic chemical toxic material Material causing injury to living organisms as a result of physicochemical interactions.
Process of interaction of potentially toxic substances with target sites, and the biochemical and physiological consequences leading to adverse effects.
Scientific sub-discipline that combines toxicology with genomics to determine how an organism’s genetic make-up influences its response to a toxic substance.
Study of the influence of hereditary factors on the effects of potentially toxic substances on individual organisms.
Generally, the overall process of the absorption (uptake) of potentially toxic substances by the body, the distribution of the substances and their metabolites in tissues and organs, their metabolism (biotransformation), and the elimination of the substances and their metabolites from the body. In validating a toxicological study, the collection of toxicokinetic data, either as an integral component in the conduct of non-clinical toxicity studies or in specially designed supportive studies, in order to assess systemic exposure.
- toxicological data sheet
Document that gives in a uniform manner data relating to the toxicology of a substance, its production and application, properties and methods of identification. Note: The data sheet may also include recommendations on protective measures.
- toxicologically based pharmacokinetic modeling (TBPK
See physiologically based pharmacokinetic modeling
Scientific discipline involving the study of the actual or potential danger presented by the harmful effects of substances on living organisms and ecosystems, of the relationship of such harmful effects to exposure, and of the mechanisms of action, diagnosis, prevention and treatment of intoxications.
Term sometimes used to indicate a combination of investigative methods and techniques for making a quantitative assessment of toxicity and the hazards of potentially toxic substances.
Morbid dread of poisons.
- toxicophoric group
toxogenic group toxophoric group Structural moiety that upon metabolic activation exerts toxic effects: the presence of a toxicophoric group indicates only potential and not necessarily actual toxicity of a drug or other substances.
Active process of identification, investigation, and evaluation of various toxic effects in the community with a view to taking measures to reduce or control exposure(s) involving the substance(s) which produces these effects.
Metabolic conversion of a potentially toxic substance to a product that is more toxic.
Poisonous substance produced by a biological organism such as a microbe, animal, plant or fungus. Note: Examples are botulinum toxin, tetrodotoxin, pyrrolizidine alkaloids and amanitin.
Scientific discipline involving the study of the chemistry, biochemistry, pharmacology and toxicology of toxins.
- toxogenic group
- toxophoric group
- traceability (in metrology
Property of a measurement result whereby the result can be related to a stated reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.
Means by which something may be followed; for example a radioactive isotope may replace a stable chemical element in a toxic compound enabling the toxicokinetics to be followed. Labeled member of a population used to measure certain properties of that population.
Substance which can be tracked through one or more reactions or systems, often by detecting an incorporated isotope.
Process by which the genetic information encoded in a linear sequence of nucleotides in one strand of DNA is copied into an exactly complementary sequence of RNA.
Total messenger RNA expressed in a cell or tissue at a given point in time.
Global analysis of gene expression to identify and evaluate changes in synthesis of mRNA after chemical exposure.
Alteration of a cell by incorporation of foreign genetic material and its subsequent expression in a new phenotype. Conversion of cells growing normally to a state of rapid division in culture resembling that of a tumor. Chemical modification of substances in the environment.
- transformed cell
Cell which has become genetically altered spontaneously or by incorporation of foreign DNA to produce a cell with an extended lifetime in culture.
- transformed cell line
See cell line, transformed cell
Gene from one source that has been incorporated into the genome of another organism.
Adjective used to describe animals carrying a gene introduced by micro-injecting DNA into the nucleus of the fertilized egg.
Process through which a polypeptide chain of amino acid molecules is generated as directed by the sequence of a particular messenger RNA sequence.
Mobile nucleic acid element.
In relation to waste water, the amenability of substances to removal without adversely affecting the normal operation of biological treatment processes (such as a sewage treatment plant).
Process for sorting people into groups based on their need for or likely benefit from immediate medical treatment. Note: Triage is used in hospital emergency rooms, on battlefields, and at disaster sites when limited medical resources must be allocated. System used to allocate a scarce commodity, such as food, to those most likely to benefit from it. Process in which things are ranked in terms of importance or priority.
Amount of energy in terms of food that an organism needs. Note: Organisms not needing organic food, such as plants, are said to be on a low trophic level, whereas predator species needing food of high energy content are said to be on a high trophic level. The trophic level indicates the level of the organism in the food chain.
Closeness of agreement between the average of an theoretically infinite number of replicate measured quantity values and a reference quantity value.
- tubular reabsorption
Transfer of solutes from the renal tubule lumen to the tubular epithelial cell and normally from there to the peritubular fluid.
Able to cause tumors.
tumour neoplasm
Any abnormal swelling or growth of tissue, whether benign or malignant. An abnormal growth, in rate and structure, that arises from normal tissue, but serves no physiological function.
- tumor necrosis factor (TNF
cachectin cachexin Protein produced by several of the body's cell types, such as white blood cells, red blood cells, and other cells that line the blood vessels; it promotes the destruction of some types of cancer cells and is a cytokine involved in systemic inflammation.
- tumor progression
Sequence of changes by which a benign tumor develops from the initial lesion to a malignant stage.
Gene which serves to protect cells from entering a cancerous state. Note: According to Knudson’s “two-hit” hypothesis, both alleles of a particular tumor suppressor gene must acquire a mutation before the cell will enter a transformed state.
- turnover time
- two-compartment model
Product of compartmental analysis requiring two compartments.
See compartmental modeling, multicompartment analysis
Defect, often associated with inflammation, occurring locally or at the surface of an organ or tissue owing to sloughing of necrotic (see necrosis) tissue.
- ultrafine particle
Particle in air of aerodynamic diameter less than 100 nm. Note: As a group, ultrafine particles are referred to as PM0.1 (100 nm is 0.1 μm).
uncertainty (in metrology) Parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used. Note: The parameter may be, for example, a standard deviation or the half-width of an interval, having a stated coverage probability.
In assay methodology, confidence interval or fiducial limit used to assess the probable precision of an estimate.
In toxicology, value used in extrapolation from experimental animals to man (assuming that man may be more sensitive) or from selected individuals to the general population. For example, a value applied to the no-observed-effect-level (NOEL) or no-observed-adverse-effect-level (NOAEL) to derive an acceptable daily intake (ADI) or tolerable daily intake (TDI).
Note: The NOEL or NOAEL is divided by the value to calculate the ADI or TDI.
Aee also modifying factor, safety factor
- unit risk
Upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 μg L-1 in water, or 1 μg m-3 in air. Note: The interpretation of unit risk is as follows: if unit risk = 1.5 x 10-6 μg L-1, 1.5 excess tumors are expected to develop per 1 000 000 or 106 people if exposed daily for a lifetime to 1 μg of the chemical in 1 litre of drinking water.
- upper boundary
Estimate of the plausible upper limit to the true value of a quantity. Note: This is usually not a statistical confidence limit.
Entry of a substance into the body, into an organ, into a tissue, into a cell, or into the body fluids by passage through a membrane or by other means.
Vascular reaction of the skin marked by the transient appearance of smooth, slightly elevated patches (wheals, hives) that are redder or paler than the surrounding skin and often attended by severe itching.
Membrane-bound cavity within a cell.
Expression of the degree to which a measurement measures what it purports to measure.
Degree to which the inferences drawn, especially generalizations extending beyond the study sample, are warranted when account is taken of the study methods, the representativeness of the study sample, and the nature of the population from which it is drawn.
antonym vasodilation Decrease of the caliber of the blood vessels leading to a decreased blood flow.
antonym vasoconstriction Increase in the caliber of the blood vessels, leading to an increased blood flow.
See cloning vector
Substance(s) used to formulate active ingredients for administration or use. Note: In this context, it is a general term for solvents, suspending agents, etc.
Animal toxin generally used for self-defense or predation and usually delivered by a bite or sting.
Process of supplying a building or room with fresh air. Process of exchange of air between the ambient atmosphere and the lungs. In physiology, the amount of air inhaled per day. Oxygenation of blood.
Irregular heartbeat characterized by uncoordinated contractions of the ventricle.
Substance intended to kill intestinal worms.
See anthelmint(h)ic
Dizziness; an illusion of movement as if the external world were revolving around an individual or as if the individual were revolving in space.
adj., Producing blisters on the skin. n., Substance that causes blisters on the skin.
In cell biology, small bladder-like, membrane-bound sac containing aqueous solution or fat. In pathology, blisterlike elevation on the skin containing serous fluid.
Human exposure over a lifetime to a carcinogen which has been estimated, using mathematical modeling, to result in a very low incidence of cancer, somewhere between zero and a specified incidence, e.g. one cancer in a million exposed people.
antiviral Substance used to control viruses.
Apparent (hypothetical) volume of fluid required to contain the total amount of a substance in the body at the same concentration as that present in the plasma assuming equilibrium has been attained.
Any organic compound having, at 293.15 K, a vapor pressure of 0.01 kPa or more, or having a corresponding volatility under the particular condition of use.
See susceptible
Anything that is discarded deliberately or otherwise disposed of on the assumption that it is of no further use to the primary user.
- wasting syndrome
Disease marked by weight loss and atrophy of muscular and other connective tissues that is not directly related to a decrease in food and water consumption.
- water potential (in physiology
Difference in free energy or chemical potential (per unit molal volume) between pure water and water in cells and solutions.
Dose-response model of the form
where P(d) is the probability of a tumor (or other response) from lifetime, continuous exposure at dose d until age t (when tumor is fatal), α is a fitted dose parameter (sometimes called the Weibull parameter), Β is a fitted dose parameter, and γ is the background response rate.
- weight-of-evidence for toxicity
Extent to which the available biomedical data support the hypothesis that a substance causes a defined toxic effect such as cancer in humans.
- withdrawal effect
Adverse event following withdrawal from a person or animal of a drug to which they have been chronically exposed or on which they have become dependent.
- working zone
Space measuring up to 2 m over the level of the floor or platform that contains a worker's permanent or temporary station.
Hyperkeratotic disease in cattle following exposure to chlorinated dibenzo-p-dioxins, naphthalenes and related compounds.
Compound with a chemical structure foreign to a given organism. Note: Frequently restricted to man-made compounds.
Genetic method for analysing the interactions of proteins.
Kinetics of a reaction in which the rate is independent of the concentration(s) of the reactants.
Substance intended to kill animals.
Cell such as a fertilized egg resulting from the fusion of two gametes. Cell obtained as a result of complete or partial fusion of cells produced by meiosis.
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