Haloacetic Acids in Public Water and Health

haloacetic acid in public water

Haloacetic Acids are a family of chemicals formed when disinfectants used to kill viruses and bacteria in community water supplies react with naturally occurring organic matter and other substances in the source water. The risk of illness from haloacetic acids is much lower than the risk of illness from drinking most surface water and some groundwater sources that have not been disinfected.

Haloacetic Acids include five related chemicals and have a combined maximum contaminant level (MCL) of 60 mcg/L:

  • trichloroacetic acid
  • dichloroacetic acid
  • monochloroacetic acid
  • dibromoacetic acid
  • monobromoacetic acid

Exposure and Risk

When people consume haloacetic acids at high levels over many years, they increase their risk of developing bladder cancer. Other health effects that may be associated with haloacetic acids include rectal and colon cancer, and adverse developmental and reproductive effects during pregnancy. They have been studied with mixed results; however, the weight of evidence of the health effects data suggests a potential association.

There are several ways that haloacetic acids can get into your body.

  • Ingestion (through your mouth): drinking water with haloacetic acids
  • Inhalation (through your nose): Some haloacetic acids can be released into the air in your home when you use your tap water. This can happen when you are taking a shower or washing dishes. The hotter the water is, the more likely it is that haloacetic acids will be released into the air. Haloacetic acids can also get into the air when you boil your tap water, such as when you make tea or soup.
  • Dermal (through your skin): You can be exposed to haloacetic acids when your skin comes into direct contact with water, like when you are bathing or showering. But for most people, only very small amounts of haloacetic acids get into the body through the skin. However, much higher levels of haloacetic acids can get in your body when your contact time with water increases. This can happen if you typically take long baths or swim frequently in public pools.


Community Public Water Supplies are already being tested for haloacetic acids, and are required to provide that information each year to consumers in the annual Consumer Confidence Report. If your Public Water System has notified you of a haloacetic acids violation, it does not mean that the people who consume the system's water will become sick.

The U.S. Environmental Protection Agency (EPA) requires that water systems use treatment methods to reduce the formation of haloacetic acids and to protect people from waterborne disease and the potential harmful effects of haloacetic acids.