Dichloroacetic acid in Drinking Water: Complete Guide (2026)

What is Dichloroacetic acid and Why Does It Matter?

DICHLOROACETIC ACID: WHAT'S IN YOUR WATER AND WHY IT MATTERS

What Is Dichloroacetic Acid and How Does It Get Into Your Water?

Dichloroacetic acid (DCAc) is a chemical byproduct created when chlorine or bromine reacts with organic matter in water during the disinfection process. Water utilities add chlorine to kill bacteria and viruses that cause diseases like cholera and typhoid. But when that chlorine meets naturally occurring organic compounds—leaves, algae, decaying plant material—it forms unwanted byproducts called disinfection byproducts (DBPs). Dichloroacetic acid is one of the most common ones. This means the chemical that's supposed to protect you from one threat inadvertently creates another. The more organic matter in the source water and the higher the chlorine dose, the more dichloroacetic acid forms. Utilities in areas with heavily vegetated watersheds or older treatment plants tend to see higher levels.

Health Effects: What the Research Shows

At low levels, dichloroacetic acid exposure may cause minor effects. But the Environmental Working Group (EWG) has identified it as a concern at much lower levels than the EPA currently allows. Studies in animals show that dichloroacetic acid can affect the liver and kidneys, the organs responsible for filtering toxins from your body. Exposure during pregnancy and early childhood appears particularly risky—research suggests it may interfere with fetal development. The National Toxicology Program found that dichloroacetic acid caused cancer in laboratory mice at high doses, though human studies remain limited. Most concerning: nearly all affected water systems exceed EWG's health guideline. Out of 20,332 water systems tested, 19,995 systems—that's 98%—had levels above what EWG recommends for safe long-term exposure.

The Regulation Gap: EPA vs. EWG Standards

Here's where things get complicated. The EPA sets a legal limit of 60 ppb (parts per billion) for dichloroacetic acid as part of the Total Trihalomethanes rule. Most utilities stay below this threshold and consider their water "safe." But EWG's health guideline is just 0.6 ppb—100 times stricter. The data shows the average dichloroacetic acid level across affected systems is 6.802 ppb, with some systems reaching 240 ppb. That means even "compliant" water can contain levels 11 times higher than EWG considers safe for vulnerable populations. The EPA's standard was set in 1979 and hasn't been updated despite newer health research. This gap between legal compliance and health protection is why many families choose additional filtration.

Where the Problem Is Worst

Dichloroacetic acid contamination isn't random—it follows clear geographic patterns. Texas leads with 2,418 affected systems, followed by Illinois (1,522), North Carolina (1,136), New York (1,121), and California (1,093). These states share common factors: large populations requiring extensive water treatment, aging infrastructure, and in some cases, water sources rich in organic matter. Texas's challenge stems partly from its vast geography and reliance on surface water sources that pick up organic compounds. The Midwest's older water systems often use outdated treatment methods that produce more byproducts. Coastal and humid regions naturally have more vegetation in their watersheds, increasing organic precursors. If you live in these five states, there's a higher statistical likelihood your tap water contains elevated dichloroacetic acid.

Removing Dichloroacetic Acid From Your Water

The good news: dichloroacetic acid is removable. Activated carbon filters—the kind in pitcher filters or under-sink systems—reduce dichloroacetic acid by 50-70% if you replace them regularly. Reverse osmosis systems are more effective, removing up to 99% of dichloroacetic acid and most other disinfection byproducts. Whole-house systems protect your entire family, including water used for cooking and bathing. If you're concerned about your specific water, get it tested first. Many utilities provide free water quality reports, or you can use Echo Water's testing service to measure dichloroacetic acid levels in your home. Once you know your levels, you can choose the right filtration approach for your family's needs and budget.

Regulatory Standards for Dichloroacetic acid

Cities With the Highest Dichloroacetic acid Levels

States Most Affected by Dichloroacetic acid

Frequently Asked Questions

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