Chloroethane in Drinking Water
Found in 81 water systems • vocs
Updated September 2026 • Data from EWG & EPA
What is Chloroethane and Why Does It Matter?
CHLOROETHANE: WHAT YOU NEED TO KNOW ABOUT THIS INDUSTRIAL CHEMICAL IN YOUR WATER
What Is Chloroethane and How Does It Get Into Drinking Water?
Chloroethane (also called ethyl chloride) is a colorless, flammable gas used primarily in industrial manufacturing. It's a solvent in pesticide production and appears in some pharmaceutical manufacturing processes. The chemical enters groundwater through industrial discharge, improper disposal of manufacturing waste, and contamination from old industrial sites. Once in the water supply, chloroethane persists because it doesn't break down easily in the environment. Our analysis found chloroethane in 81 water systems across the United States, with concentrations averaging 0.984 ppb (parts per billion) and peaking at 4.18 ppb in the most contaminated system.
The geographic pattern is striking: Maryland accounts for 49 of the 81 affected systems—more than 60 percent of all detections. This concentration suggests either historical industrial activity in the region or specific hydrogeological conditions that allow the chemical to persist in groundwater. New York follows with 11 systems, Texas with 7, and Georgia and California with 2 systems each. The Maryland clustering points to legacy contamination from mid-20th century manufacturing rather than ongoing widespread pollution.
Health Effects and Exposure Risks
The health effects of chloroethane exposure depend on concentration and duration. At low levels found in drinking water, the primary concern is long-term exposure. Animal studies show that chronic chloroethane exposure can affect the liver and nervous system. The EPA classifies chloroethane as a possible human carcinogen based on animal research, though human epidemiological data remains limited. This classification means the chemical *may* increase cancer risk with prolonged exposure, but evidence in humans isn't conclusive.
For the levels we're seeing in water systems—averaging under 1 ppb—acute (short-term) health effects are unlikely. However, vulnerable populations including pregnant women, young children, and people with compromised immune systems should take extra precaution. Most health concerns center on cumulative exposure over months and years rather than single exposures.
The Regulatory Picture
Here's where things get complicated: the EPA has not set a maximum contaminant level (MCL) for chloroethane in drinking water. This means there's no federal enforceable limit. However, the EPA does list it as a volatile organic compound (VOC) that water systems should monitor. The Environmental Working Group (EWG), which sets stricter health-based guidelines than the EPA, recommends a limit of 0.35 ppb for chloroethane. Using this standard, none of the 81 systems we detected exceeded the EWG guideline, though some came close—the highest reading at 4.18 ppb is 12 times the EWG recommendation.
The absence of an EPA MCL doesn't mean the chemical is safe. It reflects the EPA's regulatory priorities and the challenge of setting limits for thousands of possible contaminants. Many states, particularly those with significant detections like Maryland, have their own monitoring and advisory programs.
Removing Chloroethane From Your Water
If you live in one of the 81 affected systems, several filtration methods effectively remove chloroethane. Activated carbon filters are highly effective at trapping volatile organic compounds like chloroethane, removing 85-95 percent of the chemical. Reverse osmosis systems provide even better protection, eliminating 99% of chloroethane and other VOCs. Whole-home systems offer comprehensive protection for all water uses, while point-of-use filters under the sink or pitcher-style filters work for drinking and cooking water.
Your first step: contact your local water utility and request their latest water quality report. Ask specifically about chloroethane levels in your area. If your system detected chloroethane, an activated carbon filter or reverse osmosis system provides reliable protection. For Maryland residents especially, given the concentration of detections in your state, testing your water and installing appropriate filtration is a smart precaution.
Regulatory Standards for Chloroethane
| Standard | Level | Notes |
|---|---|---|
| Average Detected Level | 0.98 ppb | Across all tested systems |
| Highest Detected Level | 4.18 ppb | Worst-case system |
Cities With the Highest Chloroethane Levels
| # | City | Detected Level | People Served |
|---|---|---|---|
| 1 | Snow Hill, MD | 4.18 ppb | 0 |
| 2 | Olympia, WA | 3.80 ppb | 1,274 |
| 3 | Austin, TX | 3.25 ppb | 570 |
| 4 | Frederick, MD | 3.25 ppb | 49,200 |
| 5 | Berlin, MD | 3.09 ppb | 40 |
| 6 | Sabinal, TX | 3.05 ppb | 0 |
| 7 | Berlin, MD | 3 ppb | 48 |
| 8 | Orchard Park, NY | 2.78 ppb | 150 |
| 9 | Sinclairville, NY | 2.58 ppb | 772 |
| 10 | Berlin, MD | 1.78 ppb | 4,500 |
| 11 | Berlin, MD | 1.78 ppb | 150 |
| 12 | Indian Head, MD | 1.52 ppb | 4,100 |
| 13 | Waldorf, MD | 1.50 ppb | 40 |
| 14 | La Plata, MD | 1.41 ppb | 280 |
| 15 | Millersville, MD | 1.35 ppb | 275 |
States Most Affected by Chloroethane
How to Remove Chloroethane From Your Water
Activated carbon strongly adsorbs chloroethane and other volatile organic compounds due to high lipophilicity and surface area affinity.
Standard pitcher filters and carbon block filters can provide some reduction of Chloroethane, though effectiveness varies by brand and flow rate. For maximum protection, a certified RO system is recommended.
Activated carbon block filters effectively remove most VOCs including chloroethane when properly maintained; pitcher filters may be less efficient than countertop carbon blocks.
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Shop Hydrogen FlaskFrequently Asked Questions
Is Chloroethane in my drinking water?
Chloroethane was detected in 81 water systems across the US. Check your city's water quality report to see if it affects your water supply.
What are the health effects of Chloroethane in water?
Chloroethane has been associated with various health concerns at elevated levels. The EWG has set health guidelines that are typically stricter than EPA legal limits.
Which city has the most Chloroethane in its water?
Based on our analysis, Snow Hill, MD has the highest detected levels of Chloroethane in its water supply.
How do I remove Chloroethane from my water?
Reverse osmosis (RO) systems are generally the most effective at removing this contaminant. Check the filtration recommendations section for specific guidance.
Related Contaminant Guides
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: September 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
