What is Tetrachloroethylene (perchloroethylene)* and Why Does It Matter?

Tetrachloroethylene, commonly known as PCE or "perc," is a colorless industrial solvent with a sharp, sweet smell. Dry cleaners have used it for decades to remove stains from fabric without water. It also shows up in metal degreasing operations, auto shops, and some consumer products like paint strippers and spot removers. PCE enters drinking water primarily through industrial discharge and improper disposal — when businesses dump contaminated wastewater or let chemicals seep into the ground, PCE travels down through soil and into underground water sources called aquifers. Once it's in groundwater, it moves slowly and persists for years.

The health risks from PCE are serious enough that researchers and regulators have studied it extensively. Short-term exposure at high levels can cause dizziness, headaches, and liver damage. Long-term exposure is the bigger concern. The EPA classifies PCE as a likely human carcinogen, meaning consistent exposure over time raises the risk of cancer — particularly kidney cancer and non-Hodgkin's lymphoma (a cancer of the immune system). The International Agency for Research on Cancer (IARC) goes further, classifying it as a probable human carcinogen. Children and pregnant women face heightened risks, since PCE can cross the placenta and has been linked to developmental problems in infants exposed before birth.

Current U.S. regulations set the legal limit for PCE in drinking water at 5 parts per billion (ppb), a standard the EPA established in 1991. The Environmental Working Group (EWG) argues that limit is dangerously outdated. Their health guideline sits at just 0.1 ppb — 50 times stricter than the federal standard — based on more recent cancer research. The data here tells a clear story: across 92 water systems where PCE was detected, the average level measured 0.453 ppb. That's more than 4 times above the EWG's health guideline. The highest recorded level hit 2.29 ppb. While that technically stays under the EPA's legal limit, it sits more than 22 times above what EWG considers safe. Of the 92 systems that detected PCE, 72 of them — about 78% — registered levels above the EWG health guideline.

Geographically, PCE contamination clusters in states with older industrial histories and dense urban development. California leads with 17 affected systems, followed by Pennsylvania with 9, West Virginia with 8, New York with 7, and Kansas with 5. California's contamination often traces back to decades of dry cleaning operations concentrated in older neighborhoods, particularly in the Los Angeles and San Francisco Bay areas. Pennsylvania and West Virginia's numbers reflect their industrial manufacturing past — both states have significant histories with metal fabrication and chemical processing. New York's contamination follows a similar pattern, with older urban infrastructure and legacy industrial sites contributing to groundwater pollution. Kansas shows up partly due to agricultural and light industrial activity. In all these states, communities drawing water from wells or older municipal systems face the greatest exposure risk.

The good news is that PCE responds well to filtration. Activated carbon filters — the kind found in many under-sink and whole-house systems — can significantly reduce PCE levels. Granular activated carbon (GAC) is especially effective, as the carbon material binds to PCE molecules and pulls them out of the water. For the most thorough protection, reverse osmosis (RO) systems remove up to 99% of PCE and are widely considered the gold standard for volatile organic compounds like this one. Echo Water's reverse osmosis systems are designed specifically to address contaminants like PCE that standard municipal treatment may not fully eliminate. If you're in one of the states listed above — or if you're simply unsure what's in your water — getting a water quality test is the smartest first step. Knowing your actual contamination level helps you choose the right filter rather than guessing. You don't need to panic, but you do need a plan.

Regulatory Standards for Tetrachloroethylene (perchloroethylene)*

Cities With the Highest Tetrachloroethylene (perchloroethylene)* Levels

States Most Affected by Tetrachloroethylene (perchloroethylene)*

Frequently Asked Questions

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