1,1,1-Trichloroethane in Drinking Water: Complete Guide (2026)

What is 1,1,1-Trichloroethane and Why Does It Matter?

# 1,1,1-Trichloroethane (TCA): What You Need to Know

## What It Is and Where It Comes From

1,1,1-Trichloroethane is a colorless liquid that was widely used as a degreaser and solvent in manufacturing, dry cleaning, and metal processing for decades. The EPA phased out its production in the United States in 2002 because of its ozone-depleting properties, but the chemical persists in groundwater across the country. Once TCA seeps into soil—from industrial spills, improper disposal, or leaking storage tanks—it moves slowly through groundwater and can contaminate drinking water supplies for years. Even though new sources have largely stopped, legacy contamination from old industrial sites and former military bases continues to appear in wells and municipal water systems.

## Health Effects and Safety Concerns

At low exposure levels, 1,1,1-trichloroethane primarily affects the central nervous system and liver. Short-term exposure causes dizziness, headaches, and fatigue. Long-term exposure at higher concentrations raises concerns about liver damage and potential cancer risk, though human studies are limited. The EPA classifies TCA as a possible carcinogen based on animal studies. Most people exposed through drinking water face minimal immediate risk, but children and pregnant women warrant extra caution since their bodies are still developing and more sensitive to chemical exposures.

The good news: current detections rarely reach dangerous levels. Our data shows 98 water systems detected TCA, with an average concentration of 0.609 ppb (parts per billion). Only one sample reached the maximum of 25.9 ppb—still well below the EPA's safety limit.

## Regulatory Standards and Guidelines

The EPA set the Maximum Contaminant Level (MCL) for 1,1,1-trichloroethane at 200 ppb. This means water systems must treat the water if levels exceed this threshold. However, the Environmental Working Group (EWG), which applies stricter health-based standards, recommends a guideline of 0.066 ppb—roughly 3,000 times lower than the EPA's limit. This gap reflects the EWG's more conservative approach to protecting vulnerable populations like children.

None of the 98 systems in our data exceeded the EPA's legal limit, which is why TCA doesn't trigger mandatory action notices. However, the fact that TCA appears in nearly 100 systems nationwide shows how widespread legacy contamination remains, even at low levels.

## Geographic Hotspots and Why

California leads with 19 detections, followed by New York with 18 and Pennsylvania with 11. Florida and Ohio also show significant presence. This pattern reflects where industrial activity was heaviest in the mid-to-late 20th century. California's aerospace and electronics manufacturing sectors, New York's chemical plants, and Pennsylvania's steel mills all relied on TCA-based solvents. Older industrial sites in these states often lack proper remediation, allowing TCA to continue leaching into groundwater. The Northeast and Mid-Atlantic regions show particularly high detection rates because of their dense manufacturing history and aging infrastructure.

## How to Remove It from Your Drinking Water

Activated carbon filters and reverse osmosis systems both effectively remove 1,1,1-trichloroethane from drinking water. Activated carbon adsorbs the chemical molecules, trapping them in the filter material. Reverse osmosis forces water through a semipermeable membrane, removing TCA and other contaminants with 99%+ effectiveness. For households in areas with detected TCA, a point-of-use system on your kitchen tap provides targeted protection where you drink and cook.

If you live in California, New York, Pennsylvania, Florida, or Ohio, request a copy of your water system's annual water quality report (called a Consumer Confidence Report). It lists all detected contaminants. If TCA appears, a simple activated carbon or reverse osmosis filter gives you direct control over your family's exposure.

Regulatory Standards for 1,1,1-Trichloroethane

Cities With the Highest 1,1,1-Trichloroethane Levels

States Most Affected by 1,1,1-Trichloroethane

Frequently Asked Questions

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