Ethanethiol in Drinking Water: Complete Guide (2026)

What is Ethanethiol and Why Does It Matter?

ETHANETHIOL IN YOUR TAP WATER: WHAT YOU NEED TO KNOW

What Is Ethanethiol and Where Does It Come From?

Ethanethiol is a volatile organic compound (VOC) — a type of chemical that easily evaporates into the air. You might recognize its smell: it's the pungent odor added to natural gas so you can detect leaks. In nature, ethanethiol occurs in small amounts in crude oil and is produced during the breakdown of organic matter in soil and water. It enters tap water supplies through two main pathways. First, industrial discharge from petroleum refineries, chemical plants, and food processing facilities can introduce ethanethiol directly into groundwater and surface water. Second, it can form when chlorine-based disinfectants react with sulfur-containing organic compounds already present in raw water — a process called disinfection byproduct formation.

The chemical's volatile nature means it often escapes into the air during water treatment or sits in pipes, which is why it's more commonly detected in areas with significant industrial activity or aging water infrastructure.

Health Effects and Exposure Concerns

Ethanethiol is classified as a volatile organic compound, and the EPA has not established a mandatory drinking water standard (Maximum Contaminant Level) for it. This doesn't mean it's harmless — it means there isn't enough human health data to set a firm safety threshold. Limited animal studies suggest that high-level exposure can affect the nervous system and liver, but direct human health studies are sparse.

The good news: the average concentration detected in affected water systems is only 1.686 parts per billion (ppb), well below levels that typically trigger health concerns in toxicology research. However, some systems have measured ethanethiol as high as 5.0 ppb. For perspective, the EPA's drinking water standard for benzene, a similar volatile organic compound, is 5 ppb — the same as the maximum ethanethiol level found in these systems. This suggests ethanethiol at these concentrations warrants attention, especially for pregnant women, young children, and people with compromised immune systems who may be more sensitive to chemical exposure.

The Regulatory Picture

Currently, the EPA does not regulate ethanethiol as a drinking water contaminant, meaning water utilities are not required to test for it or remove it. The Environmental Working Group (EWG), a nonprofit that sets stricter health-based guidelines than the EPA, has not published a specific guideline for ethanethiol either — partly because research on human health effects remains limited. This regulatory gap means many people don't know if ethanethiol is in their water.

What's noteworthy: 78 water systems across the country have detected ethanethiol, and zero systems exceeded any established guideline. This reflects the absence of a regulatory standard rather than a clean bill of health.

Why Texas Is the Hotspot

All 78 detected cases of ethanethiol in tap water occurred in Texas. This concentration makes sense given Texas's industrial profile. The state is home to massive petroleum refineries, petrochemical plants, and natural gas processing facilities — particularly along the Gulf Coast and in the Houston area. These industries are major sources of ethanethiol release. Additionally, Texas has extensive groundwater-dependent water systems, and industrial discharge can more easily contaminate groundwater than surface water.

The warm Texas climate also plays a role: higher temperatures increase evaporation rates, meaning more ethanethiol escapes from water sources before it reaches your tap — which actually reduces exposure in some cases but indicates the chemical is present in the source water.

How to Remove Ethanethiol From Your Water

Effective removal of ethanethiol requires activated carbon filtration or reverse osmosis systems. Activated carbon absorbs volatile organic compounds, making it the most practical choice for removing ethanethiol. A whole-house carbon filter can reduce ethanethiol throughout your home, while point-of-use filters (like pitcher or faucet filters) work for drinking water specifically.

Reverse osmosis systems remove up to 99.9% of VOCs, including ethanethiol, making them highly effective if you want maximum protection. If you live in a Texas area with industrial activity nearby, testing your water is the first step — it tells you whether ethanethiol is actually present in your supply. From there, a certified water quality professional can recommend the right filtration approach for your home.

Regulatory Standards for Ethanethiol

Cities With the Highest Ethanethiol Levels

States Most Affected by Ethanethiol

Frequently Asked Questions

Related Contaminant Guides