Trihalomethane

Group of chemical compounds

Trihalomethanes

Fluoroform

Chlorodifluoromethane

Chloroform

Bromodichloromethane

Dibromochloromethane

Bromoform

Iodoform

Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH_) are replaced by halogen atoms. The general formula for trihalomethanes is CHX_, where X represents a halogen atom, such as fluorine, chlorine, bromine, or iodine.

Formation

Trihalomethanes are often formed as a byproduct of water chlorination, a process used to disinfect drinking water. When chlorine or other disinfectants react with natural organic matter in water, trihalomethanes can be produced. The presence of THMs in drinking water is a concern due to their potential health effects.

Health effects

Exposure to trihalomethanes has been associated with various health risks. Some studies suggest a link between long-term exposure to THMs and an increased risk of cancer, particularly bladder cancer. Additionally, there may be reproductive and developmental effects associated with THM exposure.

Regulation

Due to their potential health risks, the concentration of trihalomethanes in drinking water is regulated in many countries. For example, the United States Environmental Protection Agency (EPA) has set a maximum contaminant level for total trihalomethanes (TTHMs) in drinking water at 80 parts per billion (ppb).

Types of trihalomethanes

There are several common types of trihalomethanes, each with different halogen atoms:

• Fluoroform (CHF_)
• Chlorodifluoromethane (CHClF_)
• Chloroform (CHCl_)
• Bromodichloromethane (CHBrCl_)
• Dibromochloromethane (CHBr_Cl)
• Bromoform (CHBr_)
• Iodoform (CHI_)

Related pages

• Haloform reaction
• Disinfection by-product
• Water purification