EPA legal limit
No federal limit
Maximum Contaminant Level
EWG health guideline
0.1 ppb
Science-based, stricter target
IARC classification
Group 2B — possibly carcinogenic to humans
Cancer research classification
Health effects
TCA is classified as a possible human carcinogen (Group 2B) by IARC. Animal studies have shown liver tumours and skeletal abnormalities. Reproductive toxicity studies suggest effects on embryo development at doses above those found in drinking water. TCA is generally considered less potent than DCA but still contributes meaningfully to HAA5-associated health risk.
Where it comes from
Formed during chlorination of water containing natural organic matter (humic substances). Levels are higher in warm months and in utilities treating surface water with high organic content. Like DCA, TCA formation increases with higher chlorine doses.
How it's regulated
No individual EPA MCL — regulated as part of the HAA5 group standard of 60 ppb. EWG health guideline: 0.2 ppb, based on cancer risk. Typically detected at lower levels than DCA in most US water systems.
How to filter trichloroacetic acid
Not all filters address trichloroacetic acid. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is trichloroacetic acid?
Trichloroacetic acid (TCA) is one of the five haloacetic acid compounds regulated under the HAA5 standard. It is typically the second most prevalent HAA in chlorinated water after dichloroacetic acid. TCA forms when chlorine reacts with natural organic matter in source water.
What are the health effects of trichloroacetic acid?
TCA is classified as a possible human carcinogen (Group 2B) by IARC. Animal studies have shown liver tumours and skeletal abnormalities. Reproductive toxicity studies suggest effects on embryo development at doses above those found in drinking water. TCA is generally considered less potent than DCA but still contributes meaningfully to HAA5-associated health risk.
Is trichloroacetic acid regulated in drinking water?
No individual EPA MCL — regulated as part of the HAA5 group standard of 60 ppb. EWG health guideline: 0.2 ppb, based on cancer risk. Typically detected at lower levels than DCA in most US water systems.
Where does trichloroacetic acid come from?
Formed during chlorination of water containing natural organic matter (humic substances). Levels are higher in warm months and in utilities treating surface water with high organic content. Like DCA, TCA formation increases with higher chlorine doses.
How do I remove trichloroacetic acid from tap water?
The most effective methods for removing trichloroacetic 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 trichloroacetic acid in your water?
Enter your ZIP code to see the measured level in your specific utility.