VOCs in water are among the most common and most studied chemical contaminants in US groundwater, and two of them carry the heaviest health burden: trichloroethylene and tetrachloroethylene. Both are industrial solvents, both are regulated by the EPA at 5 parts per billion, and both have driven some of the most consequential drinking water contamination cases in American history, from Camp Lejeune to the leukemia cluster behind A Civil Action. This profile explains what VOCs are, how TCE and PCE reach the tap, what they do to the body, how they are regulated, and how households can remove them.
What Are VOCs (TCE and PCE)?
Volatile organic compounds (VOCs) are a broad family of carbon-based chemicals that evaporate readily at room temperature. In drinking water, the most significant are synthetic industrial solvents — and the two that dominate both detection records and litigation are trichloroethylene (TCE) and tetrachloroethylene (PCE), also called perchloroethylene or “perc.”
TCE (chemical formula C2HCl3) is a colorless liquid with a sweet, chloroform-like odor, used for decades as a metal degreaser and solvent. PCE (C2Cl4) is a closely related chlorinated solvent and the workhorse chemical of the dry-cleaning industry. Both are denser than water, meaning that when they spill or leak, they sink through soil and groundwater rather than floating — forming persistent underground pools known as dense non-aqueous phase liquids (DNAPLs) that can contaminate aquifers for decades.
The broader VOC group regulated in drinking water also includes benzene, vinyl chloride (a TCE and PCE breakdown product), carbon tetrachloride, and 1,1-dichloroethylene. These share a defining trait that sets them apart from most other contaminants: volatility. Because VOCs evaporate easily, they do not just pose an ingestion risk — they off-gas from water during showering, dishwashing, and laundry, and they can migrate as vapor from contaminated groundwater up into buildings. This makes inhalation a major exposure route, a fact that shapes how VOCs must be treated.
At the low concentrations relevant to drinking water health limits, TCE and PCE are undetectable by taste or smell. Like 1,4-dioxane and PFAS, they are legacy industrial pollutants that resist natural breakdown and require laboratory testing to detect.
How VOCs Get Into Drinking Water
VOCs enter drinking water almost entirely through industrial activity, improper disposal, and the slow migration of solvent plumes through groundwater. Because TCE and PCE are dense and only slowly biodegradable, contamination at a single site can spread for decades and affect water systems miles from the original release.
Industrial Degreasing and Solvents
TCE was for decades the standard solvent for cleaning grease and oil off metal parts in aerospace, automotive, electronics, and machine-tool manufacturing. Vapor degreasers, parts-washing operations, and military depots used it by the ton. Spills, leaks from storage tanks, and routine disposal onto bare ground sent TCE seeping into the subsurface, where it pooled as DNAPL and slowly dissolved into the aquifers below. The same facilities often used carbon tetrachloride and 1,1,1-trichloroethane, which stabilized TCE-related solvents and frequently co-occur with 1,4-dioxane in the same plumes.
Dry Cleaning
PCE is the dominant source of dry-cleaning contamination. A typical dry-cleaning machine cycles solvent continuously, and decades of small leaks, spills, and improper waste-solvent disposal at the back of strip-mall cleaners have created thousands of localized PCE plumes across the country. Because PCE migrates readily through soil and concrete, contamination from a single former dry cleaner can reach nearby water-supply wells.
Superfund and Landfills
TCE and PCE are among the most frequently identified contaminants at Superfund National Priorities List sites — chlorinated solvents are detected at well over half of all NPL sites. Municipal and industrial landfills are a second major reservoir: discarded solvents, contaminated rags, and industrial sludge leach VOCs into groundwater through landfill leachate. Leaking underground storage tanks (USTs) at former gas stations and industrial yards add benzene and other petroleum-associated VOCs to the same groundwater.
Vapor Intrusion
Because TCE and PCE are volatile, contaminated groundwater does not stay underground. Solvent vapors rise through soil and seep into buildings through foundation cracks, sumps, and utility lines — a pathway called vapor intrusion. This exposes occupants to TCE and PCE in indoor air even when they never drink the contaminated water. Vapor intrusion is now a central concern at solvent-contaminated sites and is regulated separately from drinking water, but it underscores why VOC contamination is an inhalation problem as much as an ingestion one.
Health Effects
The defining health concern with TCE and PCE is cancer, but the two solvents carry meaningfully different risk profiles. Both also affect the liver, kidneys, immune system, and developing fetus. Critically, exposure is not limited to drinking — inhalation during showering and from vapor intrusion contributes substantially to total dose.
Cancer
TCE is one of the few drinking water contaminants classified as a known human carcinogen. In 2012, the International Agency for Research on Cancer (IARC) upgraded TCE to Group 1 — carcinogenic to humans — based primarily on strong evidence linking occupational exposure to kidney cancer. IARC and the National Cancer Institute also identify positive, if less consistent, associations with non-Hodgkin lymphoma and liver cancer. The EPA classifies TCE as carcinogenic to humans by all routes of exposure.
PCE carries a slightly lower classification. IARC rates PCE as Group 2A — probably carcinogenic to humans, based on sufficient evidence in animals and limited human evidence, with the strongest signal being an excess of bladder cancer among dry-cleaning workers. Studies have also examined associations with non-Hodgkin lymphoma and esophageal cancer. The practical takeaway: TCE has the firmer human cancer evidence (kidney), while PCE’s human signal centers on the bladder.
Developmental and Pregnancy Effects
TCE is also a developmental toxicant. Animal and epidemiological studies have linked prenatal TCE exposure to congenital cardiac defects — malformations of the developing heart — and EPA’s risk assessment treats fetal cardiac development as one of the most sensitive endpoints, occurring at lower doses than cancer. This is why TCE risk is often anchored to pregnant women rather than the general adult. Developmental TCE exposure is also associated with immune system effects, including autoimmune disease, and with neurological effects.
PCE exposure during pregnancy has been studied most thoroughly in communities served by PCE-contaminated water mains, where researchers found associations with certain birth defects and neurobehavioral effects in children, though the evidence is less definitive than for TCE’s cardiac findings. Both solvents cross the placenta.
TCE Versus PCE Risk
The two compounds are chemically similar but not interchangeable in risk terms. TCE is the more potent carcinogen by current classification (Group 1 versus 2A) and the clearer developmental hazard, with kidney cancer and fetal cardiac defects as its signature effects. PCE’s profile is weighted toward bladder cancer and liver toxicity. Both are also central nervous system depressants at high doses, producing dizziness, headache, and impaired coordination, and both damage the liver and kidneys with chronic exposure. Because vinyl chloride — a known Group 1 carcinogen tied to liver angiosarcoma — forms when TCE and PCE break down underground, contaminated sites often expose people to several carcinogenic VOCs at once.
EPA Regulation and Limits
The EPA regulates TCE and PCE under the Safe Drinking Water Act, both at a Maximum Contaminant Level (MCL) of 5 ppb (0.005 mg/L). The TCE standard took effect in 1989 and the PCE standard in 1992. For both compounds — as for the other carcinogenic VOCs — the Maximum Contaminant Level Goal (MCLG) is set at zero, reflecting the EPA’s position that there is no level of a genotoxic carcinogen in drinking water that is known to be without risk. The gap between an MCLG of zero and an enforceable MCL of 5 ppb exists because the MCL is set at the lowest level the EPA judges feasible to achieve and reliably measure with available treatment technology.
| Contaminant | MCL | MCLG | Notes |
|---|---|---|---|
| Trichloroethylene (TCE) | 5 ppb | 0 | IARC Group 1 carcinogen; effective 1989 |
| Tetrachloroethylene (PCE) | 5 ppb | 0 | IARC Group 2A; effective 1992 |
| Vinyl chloride | 2 ppb | 0 | TCE/PCE breakdown product; known carcinogen |
| Benzene | 5 ppb | 0 | From leaking USTs and fuel; known carcinogen |
Beyond the drinking water rules, the EPA moved aggressively against TCE and PCE under the Toxic Substances Control Act (TSCA). On December 17, 2024, the EPA finalized a rule banning all uses of TCE, phasing out most uses within one year and allowing longer timelines for limited workplace applications. A companion PCE rule finalized the next day tightly restricts most uses of PCE while phasing out its use in dry cleaning over roughly a decade. Both rules drew legal challenges; as of 2026 the TCE rule has taken effect with certain exemptions and extended compliance dates still being litigated, so the regulatory status continues to evolve.
How Widespread Are VOCs?
VOCs are among the most frequently detected organic contaminants in US groundwater. USGS National Water-Quality Assessment (NAWQA) sampling has detected at least one VOC in roughly one-third of wells tested, with chlorinated solvents — chiefly PCE and TCE — and chloroform among the most common. Solvents specifically turned up in about 8 percent of sampled wells nationally, and regional surveys of principal aquifers in the western US have found VOC detection frequencies ranging from 10 to 46 percent. Detections cluster around industrial corridors, urban areas, military installations, and former dry-cleaning sites rather than spreading uniformly.
The human cost is captured by several landmark cases. At Camp Lejeune, North Carolina, drinking water serving the Marine Corps base was contaminated with TCE, PCE, benzene, and vinyl chloride from roughly 1953 to 1987 — exposing an estimated hundreds of thousands of military personnel and family members and leading to a federal settlement program for affected veterans, covered in our Camp Lejeune settlement update. In Woburn, Massachusetts, TCE and PCE in municipal wells were tied to a childhood leukemia cluster in the 1970s and 1980s — the case dramatized in A Civil Action. In Toms River, New Jersey, decades of industrial solvent and chemical discharges were investigated in connection with a childhood cancer cluster. Together these cases established VOC contamination as one of the defining public-health water stories of the late 20th century.
How WaterVerge Tracks VOCs
WaterVerge pulls VOC monitoring data from EPA SDWIS, the Safe Drinking Water Information System. TCE, PCE, vinyl chloride, benzene, and the other regulated VOCs are required monitoring parameters for community water systems, which test on a schedule and report any detections and violations of the 5 ppb (or 2 ppb for vinyl chloride) limits.
City pages on WaterVerge display the most recent regulated-VOC results for the serving utility and flag any historical MCL violations on the system’s compliance record. Two important limitations apply. First, vapor intrusion is not a drinking water metric — it is an indoor-air pathway tracked by state environmental agencies and the EPA’s site-cleanup programs, not by SDWIS, so a clean drinking water record does not rule out vapor intrusion near a contaminated site. Second, private wells are not covered by SDWIS or any federal monitoring program. If you draw from a private well near an industrial site, former dry cleaner, landfill, or military base, laboratory testing is the only way to know your exposure. See our guides on well water testing and how to test your tap water.
How to Remove VOCs
Start with what does not work, because the volatility that defines VOCs cuts both ways. Boiling water does not safely remove TCE or PCE — it drives them into the air you breathe, raising indoor inhalation exposure. Standard sediment filters and water softeners do nothing for them. And because TCE and PCE off-gas during showering and laundry, point-of-use treatment at a single tap leaves the inhalation pathway open; point-of-entry (whole-house) treatment is the recommended approach for VOC contamination.
| Method | Removal Rate | Certification | Best For |
|---|---|---|---|
| Granular activated carbon (GAC), whole-house | 90-99% | NSF/ANSI 53 (VOC reduction) | Point-of-entry for VOC-contaminated wells |
| Air stripping (packed-tower aeration) | 90-99%+ | Municipal scale | Utility-scale VOC treatment |
| Carbon block, point-of-use | 90-99% | NSF/ANSI 53 (VOC reduction) | Single-tap drinking water |
| Reverse osmosis | Limited / variable | NSF/ANSI 58 | Less effective for small volatile molecules |
| Boiling | Negligible / worsens inhalation | N/A | Not recommended for VOCs |
The two standard removal technologies both exploit VOC chemistry directly. Air stripping, usually as packed-tower aeration, forces large volumes of air through the water so that volatile compounds transfer from water into air and are vented away — it is the workhorse of municipal VOC treatment and routinely achieves better than 99 percent removal. Granular activated carbon (GAC) adsorbs VOCs onto a high-surface-area carbon bed; it is highly effective for TCE and PCE and is the standard household and point-of-entry solution. Many utilities pair air stripping with GAC polishing for redundancy.
For homes, a whole-house GAC system certified to NSF/ANSI 53 for VOC reduction treats every tap, shower, and appliance, closing both the ingestion and inhalation pathways. Look specifically for the NSF/ANSI 53 VOC-reduction claim rather than a generic “carbon filter” label. See best whole-house water filters for point-of-entry options.
A note on reverse osmosis: unlike with arsenic or perchlorate, where RO excels, RO is less effective for small volatile molecules like TCE and PCE, which can partly pass through the membrane. Most under-sink RO units rely on their carbon pre- and post-filters to capture VOCs. If you choose RO for other contaminants, confirm it carries an NSF/ANSI 53 VOC claim from its carbon stages; see best reverse osmosis systems. For VOCs alone, well-designed carbon — ideally whole-house — is the better tool.
Check Your City
VOC contamination is concentrated near industrial corridors, military bases, landfills, and former dry-cleaning sites, and it varies sharply from one water system to the next. If you live near any of these — or in a community with a known solvent plume or Superfund site — it is worth checking whether your utility has recorded TCE, PCE, or other VOC detections and whether it has any history of MCL violations. Search your city to see VOC monitoring data, historical violations, and how your water system compares. If you draw from a private well near a contamination source, laboratory testing is the only way to know your exposure.
Frequently Asked Questions
Are TCE and PCE the same thing?
No. TCE (trichloroethylene) and PCE (tetrachloroethylene, or perc) are closely related chlorinated solvents but differ chemically and in risk. TCE was used mainly for industrial metal degreasing and is classified as a known human carcinogen, while PCE is the standard dry-cleaning solvent and is classified as a probable human carcinogen.
Does boiling water remove VOCs like TCE and PCE?
No, and it can make exposure worse. Because TCE and PCE are volatile, boiling drives them out of the water and into the surrounding air, increasing inhalation exposure. Granular activated carbon is the recommended removal method for home treatment.
Can I get exposed to TCE and PCE without drinking the water?
Yes. These compounds evaporate easily, so you can inhale them while showering, washing dishes, or doing laundry with contaminated water. Solvent vapors from contaminated groundwater can also seep into buildings through a pathway called vapor intrusion, exposing occupants through indoor air alone.
What is the EPA limit for TCE and PCE in drinking water?
Both TCE and PCE have an EPA Maximum Contaminant Level of 5 parts per billion, with a health goal (MCLG) of zero because both are carcinogens. The EPA also finalized rules in December 2024 to ban most uses of TCE and tightly restrict PCE under the Toxic Substances Control Act.
Does reverse osmosis remove TCE and PCE?
Reverse osmosis is less effective against TCE and PCE than against many other contaminants because these small volatile molecules can partly pass through the membrane. Most RO systems rely on their built-in carbon filters for VOC removal, so confirm the unit carries an NSF/ANSI 53 VOC-reduction certification. A dedicated activated carbon system, ideally whole-house, is the more reliable choice.
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