Total Haloacetic Acids (HAA5)
HAA5 is the sum of five haloacetic acids formed when chlorine reacts with organic matter. Unlike trihalomethanes they are non-volatile, so they are an ingestion concern rather than a shower concern. The EPA limits HAA5 to 60 ppb (0.060 mg/L).
EPA MCL
0.06 mg/L
EPA has not set a health goal (MCLG) for this contaminant. This is the enforceable limit water systems must meet.
Health Effects
Long-term exposure is associated with an increased cancer risk; dichloroacetic acid, one of the five, is classified a probable human carcinogen. The risk is chronic and lifetime rather than acute.
Source: EPA — IRIS Chemical Assessment Summary — Dichloroacetic Acid (retrieved 2026-07-27)
Common Sources
- Byproduct of disinfecting drinking water with chlorine
- Formed when chlorine reacts with natural organic matter such as decaying leaves, runoff, and algae
- Levels are highest in warm-season surface water
Is your Total Haloacetic Acids (HAA5) result safe? Get a free reading
The EPA MCL for Total Haloacetic Acids (HAA5) is 0.06 mg/L. Upload your water test (PDF or a photo) and we'll email a plain-English reading of where your result lands — and every other number — free. Educational only, no medical claims.
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Water filters certified under the following NSF standards are effective at removing Total Haloacetic Acids (HAA5):
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Where is Total Haloacetic Acids (HAA5) Found?
Total Haloacetic Acids (HAA5) has been detected above EPA health guidelines in 3 cities serving 0.0M people across the US.
About the EPA MCL
This is the enforceable federal limit water systems must meet. EPA has not set a separate non-enforceable health goal (MCLG) for this contaminant.
Contaminant Type
Total Haloacetic Acids (HAA5) is classified as a Disinfection Byproducts contaminant.
Related Disinfection Byproducts Contaminants
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