Trichloroacetic acid in Drinking Water: Complete Guide (2026)

What is Trichloroacetic acid and Why Does It Matter?

# Trichloroacetic Acid in Tap Water: What You Need to Know

Trichloroacetic acid (TCAa) is a chemical byproduct created when chlorine—the most common disinfectant in municipal water systems—reacts with organic matter already present in water. It's not added intentionally. Instead, it forms during the water treatment process itself, a problem water utilities have struggled with for decades. TCAa can also enter groundwater from industrial sources and pesticide breakdown. Once in your water supply, it persists through standard treatment and reaches your tap.

The scale of this problem is significant. Our analysis found TCAa in 16,784 water systems out of 17,052 tested—meaning 98.4% of systems exceed the EWG health guideline of 0.6 ppb (parts per billion). The average level detected was 6.448 ppb, more than 10 times the recommended safe threshold. Some systems recorded levels as high as 190 ppb. To put this in perspective: that's like having 190 grains of salt in an Olympic-sized swimming pool. For most people, it shouldn't be detectable at all.

Health research links TCAa exposure to several concerns. The International Agency for Research on Cancer (IARC) classifies it as a possible carcinogen. Studies have also associated chronic TCAa exposure with liver and kidney damage, and potential impacts on the nervous system with long-term consumption. Children and pregnant women may be more vulnerable to these effects because their bodies are still developing. The EWG's 0.6 ppb guideline was set to protect against these risks with a safety margin—but the EPA's legal limit is currently 200 ppb, which is far less protective. This gap between EPA regulation and EWG health science is why so many systems technically "pass" EPA standards while still exceeding health recommendations.

Texas, Illinois, California, New York, and Louisiana carry the heaviest burden, with 1,942, 1,288, 987, 920, and 855 affected systems respectively. These states share common factors: large populations served by municipal water systems, older infrastructure where disinfection byproducts accumulate, and in some cases, higher levels of organic matter in source water that reacts with chlorine. The Midwest and South tend to see higher TCAa levels partly because many systems there rely heavily on chlorination for disinfection, whereas some Western systems use alternative methods like ozonation or UV light.

Removing TCAa requires filtration methods that go beyond basic carbon filters. Activated carbon can reduce TCAa, but only if the filter is specifically designed for disinfection byproducts and changed frequently—typically every 6 months. Reverse osmosis systems are far more effective, removing up to 99.9% of TCAa and other chemical contaminants. Ion exchange resins also work well. If you live in one of the affected states or have noticed your water has a chemical smell or taste, testing your tap water is the first step. An Echo Water test will tell you exactly what's in your water and at what levels. From there, you can choose a filtration system matched to your specific contaminants. For drinking water and cooking, a point-of-use filter (installed at your tap or under the sink) is typically sufficient. If you're concerned about exposure through showering, a whole-home system may be worth considering, though skin absorption of TCAa during bathing is lower than ingestion risk.

Regulatory Standards for Trichloroacetic acid

Cities With the Highest Trichloroacetic acid Levels

States Most Affected by Trichloroacetic acid

Frequently Asked Questions

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