EPA legal limit
60 ppb
Maximum Contaminant Level
EWG health guideline
0.1 ppb
Science-based, stricter target
Health effects
Dichloroacetic acid and trichloroacetic acid have shown carcinogenic activity in animal studies. Human epidemiological studies associate elevated HAA5 exposure with increased cancer risk and adverse reproductive outcomes. The EPA MCL of 60 ppb is 600× higher than the EWG health guideline of 0.1 ppb.
Where it comes from
Like TTHMs, HAA5 compounds are disinfection byproducts — they are not present in source water but form during chlorination. Surface water utilities with higher organic matter loads tend to produce more HAAs. They are also formed when chloramines are used as a secondary disinfectant.
How it's regulated
Regulated under EPA Stage 2 Disinfectants and Disinfection Byproducts Rule. MCL is 60 ppb as a running annual average. HAA5 and TTHMs are monitored together and often found in the same utilities, though their ratio varies by source water chemistry.
The EPA vs EWG gap
The legal limit (60 ppb) is 600× higher than the EWG health guideline (0.1 ppb). Water can be legally compliant while still exceeding the science-based threshold.
How to filter haloacetic acids
Not all filters address haloacetic acids. Look for independently certified filters — NSF International certification means the removal claim has been independently verified.
Haloacetic acids are not removed by water ionization. An NSF 53 certified activated carbon block filter is the appropriate solution for HAA5 reduction.
Frequently asked questions
What is haloacetic acids?
Five regulated haloacetic acid compounds — monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid — formed alongside trihalomethanes during chlorine disinfection.
What are the health effects of haloacetic acids?
Dichloroacetic acid and trichloroacetic acid have shown carcinogenic activity in animal studies. Human epidemiological studies associate elevated HAA5 exposure with increased cancer risk and adverse reproductive outcomes. The EPA MCL of 60 ppb is 600× higher than the EWG health guideline of 0.1 ppb.
Is haloacetic acids regulated in drinking water?
Regulated under EPA Stage 2 Disinfectants and Disinfection Byproducts Rule. MCL is 60 ppb as a running annual average. HAA5 and TTHMs are monitored together and often found in the same utilities, though their ratio varies by source water chemistry.
Where does haloacetic acids come from?
Like TTHMs, HAA5 compounds are disinfection byproducts — they are not present in source water but form during chlorination. Surface water utilities with higher organic matter loads tend to produce more HAAs. They are also formed when chloramines are used as a secondary disinfectant.
How do I remove haloacetic acids from tap water?
The most effective methods for removing haloacetic acids are: Activated carbon block filter, NSF 53 certified filter, Reverse osmosis (RO), NSF 58 certified RO system. Look for NSF-certified systems — independent certification confirms removal claims have been verified.
Is haloacetic acids in your water?
Enter your ZIP code to see the measured level in your specific utility.