EPA legal limit
No federal limit
Maximum Contaminant Level
EWG health guideline
0.7 ppb
Science-based, stricter target
Health effects
MCAA is acutely toxic at high concentrations and is a central nervous system toxicant at industrial exposure levels. At concentrations found in drinking water, the primary concern is its contribution to overall HAA5 exposure. IARC has not classified MCAA as a carcinogen; the EWG guideline of 0.7 ppb is based on neurological and kidney effects.
Where it comes from
Formed during water chlorination. Present at lower concentrations than DCA and TCA in most treated water systems. Also formed as a metabolite during the breakdown of other HAA compounds in the body.
How it's regulated
No individual EPA MCL — regulated within the HAA5 group limit of 60 ppb. EWG health guideline: 0.7 ppb, based on toxicological effects rather than carcinogenicity.
How to filter monochloroacetic acid
Not all filters address monochloroacetic acid. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is monochloroacetic acid?
Monochloroacetic acid (MCAA) is one of the five haloacetic acids in the HAA5 group. It is typically the least prevalent HAA5 compound by mass in treated water. MCAA forms from chlorination of natural organic matter and is also a metabolite of trichloroacetic acid in the body.
What are the health effects of monochloroacetic acid?
MCAA is acutely toxic at high concentrations and is a central nervous system toxicant at industrial exposure levels. At concentrations found in drinking water, the primary concern is its contribution to overall HAA5 exposure. IARC has not classified MCAA as a carcinogen; the EWG guideline of 0.7 ppb is based on neurological and kidney effects.
Is monochloroacetic acid regulated in drinking water?
No individual EPA MCL — regulated within the HAA5 group limit of 60 ppb. EWG health guideline: 0.7 ppb, based on toxicological effects rather than carcinogenicity.
Where does monochloroacetic acid come from?
Formed during water chlorination. Present at lower concentrations than DCA and TCA in most treated water systems. Also formed as a metabolite during the breakdown of other HAA compounds in the body.
How do I remove monochloroacetic acid from tap water?
The most effective methods for removing monochloroacetic acid are: Activated carbon block filter, NSF 53 certified filter, Reverse osmosis (RO). Look for NSF-certified systems—independent certification confirms removal claims have been verified.
Is monochloroacetic acid in your water?
Enter your ZIP code to see the measured level in your specific utility.