Haloacetic Acids (HAA5) in Drinking Water

EPA Limit: 0.060 mg/L (annual average)

HAA5 is regulated alongside TTHMs under the Stage 2 Disinfectants and Disinfection Byproducts Rule. The MCL of 0.060 mg/L is based on a locational running annual average.

Where Does Haloacetic Acids (HAA5) Come From?

Like TTHMs, haloacetic acids are disinfection byproducts formed when chlorine reacts with organic matter in source water. The five regulated haloacetic acids (HAA5) are among the most common DBPs found in chlorinated drinking water.

Health Risks

Long-term exposure may increase cancer risk. Animal studies have shown liver, kidney, and reproductive effects. The EPA classifies some individual haloacetic acids as possible human carcinogens.

What Should I Do?

Activated carbon filters can reduce HAA5 levels. As with TTHMs, the disinfection itself is essential — the risk from byproducts is far lower than the risk of waterborne disease from untreated water.