What is Chloroethane and Why Does It Matter?

Chloroethane is a colorless, flammable gas that becomes a liquid under pressure. It's a synthetic chemical used mainly in industrial manufacturing, particularly in the production of tetraethyl lead (a former gasoline additive) and as a chemical intermediate in plastics and pharmaceuticals. It can enter drinking water through industrial discharge, improper waste disposal, and the breakdown of other chlorinated solvents in groundwater. Underground storage tank leaks are another common entry point, especially near older industrial sites.

Across the U.S., 77 water systems have detected chloroethane in their supplies. The average level sits at 1.002 parts per billion (ppb), with the highest recorded amount reaching 4.18 ppb. While no systems currently exceed established health guidelines, detection alone is worth understanding — especially for families with young children or pregnant women.

The health picture for chloroethane is still developing. Animal studies have linked high-dose exposure to liver and kidney damage, and the International Agency for Research on Cancer (IARC) has classified it as a possible human carcinogen. At the low levels found in most drinking water, the immediate risk appears minimal. However, long-term, low-level exposure to chlorinated compounds as a group raises legitimate concerns. The EPA notes that chronic exposure may affect the central nervous system, causing symptoms like dizziness and headaches at higher concentrations. Drinking water isn't the only exposure route — chloroethane can also be inhaled when it off-gasses from tap water during showering or cooking.

The EPA has not set a Maximum Contaminant Level (MCL) specifically for chloroethane in drinking water, which means utilities aren't legally required to limit it. The EWG recommends treating any detection as a signal worth acting on, particularly given the chemical's carcinogenic potential in animal studies. The absence of a legal limit doesn't mean the absence of risk — it often just reflects how slowly regulatory frameworks catch up with emerging science. This is one of those cases where the data is ahead of the rules.

Geographically, Maryland accounts for the largest share of detections by far, with 48 of the 77 affected systems located there. New York follows with 8 systems, Texas with 7, and Georgia and California each with 2. Maryland's pattern likely reflects its concentration of older industrial corridors and manufacturing facilities along the Chesapeake Bay region, where historical chemical use has left a legacy in groundwater. New York's detections cluster in areas with similar industrial histories, particularly around older manufacturing zones in the Hudson Valley and Long Island. Texas detections are consistent with petrochemical activity in the Gulf Coast region, where chlorinated compounds appear more frequently in groundwater monitoring data.

The good news is that chloroethane is removable. Activated carbon filtration — the kind found in quality under-sink and countertop filters — can reduce chloroethane levels significantly. For the most thorough protection, a reverse osmosis (RO) system is the gold standard. RO systems push water through a semi-permeable membrane that blocks a wide range of contaminants, including chlorinated compounds like chloroethane. Echo Water's reverse osmosis systems are designed specifically for this kind of whole-contaminant protection, giving you cleaner water at the tap without guesswork. If you're in Maryland, New York, or Texas — where detections are most common — it's worth testing your water first to know exactly what you're dealing with. A certified water test gives you a clear baseline, so any filtration choice you make is based on your actual water, not a general assumption.

Regulatory Standards for Chloroethane

Cities With the Highest Chloroethane Levels

States Most Affected by Chloroethane

Frequently Asked Questions

Related Contaminant Guides