What VOCs are most common in well water?

USGS data consistently shows four VOC groups as most common in US domestic wells: solvents (particularly TCE and PCE from dry cleaning and industrial use), BTEX compounds (benzene, toluene, ethylbenzene, xylene from gasoline and fuels), trihalomethanes (found in wells near chlorinated municipal systems that contribute to groundwater), and fumigants like DBCP (agricultural use, now banned but persistent). MTBE from fuel additives appears near gas stations and underground storage tank leaks.

How do VOCs get into private wells?

The main pathways are underground storage tank leaks (from gas stations, commercial operations), industrial discharge that reaches groundwater, agricultural chemical application, dry cleaning operations that used TCE or PCE, and waste disposal sites. VOC contamination is largely a geographic and land-use issue. Wells near industrial areas, former gas stations, or agricultural operations face the highest risk.

Are VOCs regulated in private wells?

No. The EPA's VOC MCLs apply to public water systems, not private wells. Well owners are responsible for their own testing. Many states have VOC testing programs for private wells in areas with known contamination, but there's no federal requirement for private well owners to test.

Does activated carbon remove VOCs from well water?

Yes. Granular activated carbon (GAC) or solid block carbon filters are effective at adsorbing most VOCs. NSF/ANSI 53 certification covers some VOCs specifically. For the broadest coverage, look for a filter certified to NSF 53 with a list of the specific VOCs it's tested to reduce. Reverse osmosis also removes most VOCs, though it's better at ionic contaminants than molecular ones.

How do I know if my area has VOC contamination?

Check your state environmental agency's known contamination sites database. The EPA's ECHO database shows enforcement actions against facilities that have caused groundwater contamination. If you're near a current or former industrial site, gas station, or dry cleaner, contact your state environmental or health agency to ask about any monitoring data for your area.

VOCs in Well Water: Sources, Risk, and What to Test For

This page covers contaminants with established health risks. The information here is for educational purposes only and does not constitute medical advice. If you suspect VOC contamination in your well water, contact a certified laboratory and your state environmental agency.

The USGS found detectable VOCs in about 65% of domestic well water samples tested under their National Water Quality Assessment Program. Most concentrations were below health limits, but the finding shows how common these chemicals are in groundwater. Well owners don’t have the safety net of utility testing and reporting. If there are VOCs in your well, you won’t know unless you test.

The Main Sources

VOCs reach groundwater through a handful of consistent pathways.

Industrial solvents are the most widely detected category. Trichloroethylene (TCE) and tetrachloroethylene (PCE, also called perchloroethylene) were used heavily in manufacturing and dry cleaning for decades. Both compounds are dense and move through soil readily. They’ve been found at contamination sites across the country, often persisting decades after the original source was cleaned up or closed.

Petroleum products contribute BTEX compounds: benzene, toluene, ethylbenzene, and xylene. These come from gasoline spills, leaking underground storage tanks at gas stations, and fuel handling operations. MTBE, a fuel additive that was widely used until the early 2000s, travels even more easily through soil than benzene and shows up frequently near former fueling operations.

Agricultural areas have their own profile. Fumigants like DBCP (dibromochloropropane) and EDB (ethylene dibromide) were used heavily on crops before being banned in the 1970s and 1980s. They’re still detectable in some agricultural groundwater because they persist in soil.

Landfills and waste disposal sites add a mixed VOC profile depending on what was disposed of. Older unlined landfills that accepted industrial waste are particularly common sources of VOC-contaminated leachate.

The common thread is land use. VOCs don’t appear randomly in groundwater. They follow human activity.

The High-Risk Locations

Risk tracks with what was or is nearby.

Wells within a mile of active or former gas stations, dry cleaners, auto repair shops, or light manufacturing facilities face meaningfully higher risk than rural wells surrounded by low-activity land. Urban wells and wells in mixed-use periurban areas show the highest VOC detection rates in USGS data.

Former military bases are a specific high-risk category. The Department of Defense used TCE and other solvents extensively in maintenance and manufacturing operations. Dozens of installations have documented groundwater contamination, and some plumes extend well beyond base boundaries.

Agricultural areas have elevated risk for fumigant residues, even decades after those chemicals were banned. The Central Valley in California, for example, has documented DBCP contamination from decades-old applications.

The land-use history of your area is the best predictor of what you might find. A property that has been farmland for 100 years in an area with no industrial history has a very different risk profile than a property on the edge of an industrial corridor, even if both are served by private wells.

Health Concerns

The VOC group is diverse and the health profiles differ substantially by compound.

Benzene has an MCL of 5 ppb and an MCLG of zero. The MCLG of zero means the EPA considers any exposure to carry some cancer risk, specifically leukemia. This is a well-documented carcinogen with no established safe threshold.

TCE has been classified as carcinogenic to humans by the EPA since 2011. It has an MCL of 5 ppb and an MCLG of zero. The kidney is the primary target organ for cancer risk, though neurological effects have been documented at higher exposures.

PCE has an MCL of 5 ppb and an MCLG of zero. It shares similar health concerns with TCE, with kidney and liver effects documented in occupational exposure studies.

MTBE has a different profile. Its MCL is advisory (20 ppb) rather than federally enforceable, though many states have set their own limits. The primary concern at low concentrations is taste and odor, which is detectable at levels far below any health threshold. But its presence strongly indicates nearby petroleum contamination, which typically comes with other BTEX compounds that do carry direct health risk.

The challenge with VOCs is that they’re a catch-all category covering dozens of compounds with different toxicology. A positive test result needs to be read by compound, not as a category.

Testing for VOCs

A standard basic well water test doesn’t include VOCs. Most basic panels cover bacteria, nitrates, and hardness. To test for VOCs, you need to ask specifically for a VOC panel.

A certified laboratory will run EPA Method 524.2 or 524.4, which covers a broad range of VOC compounds in drinking water. The test typically costs $75 to $150 depending on the lab and how many compounds are included. Your state environmental or health agency can provide a list of certified labs, and many offer discounted testing programs for private well owners.

If you’re near a known contamination site, your state environmental agency may already have monitoring data for your area. It’s worth calling before spending money on private testing. In some cases, they’ll test your well for free if you’re within a documented contamination zone.

Our mail-in water test guide covers labs that handle VOC panels and what to expect from the process.

Treatment Options

Activated carbon is the primary treatment for VOCs in drinking water. Granular activated carbon (GAC) filters and solid block carbon filters adsorb most VOC compounds through contact with the carbon surface. Look for NSF/ANSI 53 certification covering the specific VOCs detected in your test results.

Not all activated carbon filters cover the same compounds. The NSF certification database lists what each certified product has been tested to reduce. If you’re treating for benzene and TCE specifically, confirm those compounds appear on the product’s NSF 53 certification, not just a general VOC claim.

Reverse osmosis removes most VOCs, though it’s not ideally suited to VOCs by design. RO is optimized for ionic contaminants, but its semipermeable membrane does restrict most VOC molecules. Pairing RO with a carbon pre-filter gives you stronger coverage.

Aeration strips volatile compounds out of water by increasing surface contact with air. It’s an effective technology but more common in whole-house or municipal applications than in point-of-use systems.

See our well water testing guide for guidance on finding a certified lab and interpreting your results.

For VOC treatment options and what to look for in NSF 53 certification, see how to remove VOCs from drinking water. For the broader picture on VOCs in both well and municipal water, see the VOCs contaminant overview.

Sources

USGS. “Volatile Organic Compounds in the Nation’s Drinking-Water Supply Wells.” National Water Quality Assessment Program. https://www.usgs.gov/mission-areas/water-resources/science/national-water-quality-assessment-nawqa
EPA. “National Primary Drinking Water Regulations.” https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations
EPA. “Trichloroethylene (TCE) Health Assessment.” https://www.epa.gov/iris/toxicological-review-trichloroethylene