Air pollutants

Air pollutants are substances in the air that can cause harm to humans and the environment. They are classified into two main categories: primary and secondary pollutants. Primary pollutants are those that are directly emitted from a process, such as ash from a volcanic eruption or carbon monoxide gas from a motor vehicle exhaust. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.

Primary Air Pollutants

Primary air pollutants are emitted directly from both anthropogenic sources (human activity) and natural sources. The main primary pollutants known to cause harm to humans include:

• Carbon monoxide (CO): A colorless, odorless gas emitted from combustion processes. In urban areas, the majority of carbon monoxide emissions come from vehicles.
• Sulfur oxides (SOx): Emitted from the burning of coal and oil, especially in power stations and from motor vehicles.
• Nitrogen oxides (NOx): Emitted from high temperature combustion, and are produced naturally during electrical storms, bacterial action and volcanic eruptions.
• Particulate matter (PM): Solid particles or liquid droplets suspended in the air. They can be either human-made or naturally occurring.

Secondary Air Pollutants

Secondary pollutants are formed by a chemical reaction that occurs in the atmosphere. These include:

• Ground-level ozone (O3): Formed from NOx and volatile organic compounds (VOCs) in the presence of sunlight.
• Sulfuric acid (H2SO4): Formed from sulfur dioxide, which can lead to formation of acid rain.
• Nitric acid (HNO3): Formed from nitrogen dioxide, which can lead to formation of acid rain.

Health Effects

Air pollutants have been associated with a range of adverse health effects, including respiratory diseases, heart disease, and lung cancer. According to the World Health Organization, air pollution is the largest environmental health risk, causing millions of deaths worldwide every year.

Environmental Effects

Air pollutants can also have detrimental effects on the natural environment. They can damage forests, harm wildlife, and degrade water quality. Air pollutants are also the main cause of climate change and global warming.

Control Measures

Efforts to control air pollution include legislation, policies and practices that seek to reduce pollutant emissions and improve air quality. These measures include technological solutions, such as the use of clean energy sources, and regulatory measures, such as emission standards for vehicles and industrial facilities.