New Jersey Environmental Public Health Tracking Program

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Haloacetic Acids in Drinking Water

What Are Haloacetic Acids?

Haloacetic acids (HAAs) form in drinking water as a by-product of chlorine disinfection, through the reaction of chlorine with naturally-occurring organic chemicals in the water. There are five regulated HAAs: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid.   By removing organic contaminants from drinking water before chlorine disinfectant is applied, one can minimize the formation of HAAs.

People can be exposed to HAAs by drinking tap water.  HAAs are not absorbed through the skin and do not enter the air.  When consumed, HAAs are rapidly absorbed into the bloodstream and are carried throughout the body. 

Surface water (from rivers, lakes and reservoirs) is likely to contain natural organic materials from plants, especially during the warmer months of year.  As a result, drinking water from surface water supplies is likely to contain HAAs after chlorine is added during water treatment.  Groundwater, such as well water, does not commonly contain the organic materials necessary to form significant levels of HAAs.

How Do HAAs Affect Human Health?

hHAAs have low human and animal toxicity.  At levels encountered in drinking water, they are not expected to produce any acute health effects. However, over long periods of time, exposure to high levels of HAAs may cause injury to the brain, nerves, liver, kidneys, eyes or reproductive system.  Animal studies suggest that HAAs increase the risk of cancer, and they are currently classified as possible human carcinogens.  Decreased fertility and spontaneous abortion have been linked in some studies to HAA exposure in laboratory animals.

What is Being Done to Protect Human Health?

The U.S. Environmental Protection Agency has established a drinking water limit for HAAs. The Maximum Contaminant Level (MCL) for the sum of the concentrations of the five regulated HAAs in drinking water is 60 micrograms per liter (µg/L), averaged over a year.  New Jersey community water systems are required to monitor the formation of HAAs in the drinking water every three months and to comply with the MCL.

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