Tetrachloroethylene (Dry-Cleaning Solvent) and Cancer

Tetrachloroethylene is a halogenated alkene with the CAS number 127-18-4. Most people know it by one of its trade names: perchloroethylene, or simply perc. It is a colorless liquid at room temperature with a mildly sweet, ether-like odor. That odor is the one you notice when you open a bag of freshly cleaned clothes.

It was first prepared in 1821. United States commercial production began in 1925, reached 1.1 million pounds in 1941, and peaked at 763 million pounds in 1980.

The use pattern shifted sharply once regulation tightened. In the 1970s, United States use split roughly this way:

• 58% dry cleaning and textile processing
• 18% metal cleaning
• 12% chemical intermediates
• 12% everything else

By 2002 the same list looked very different:

• 15% dry cleaning
• 10% metal cleaning
• 65% chemical intermediates
• 10% everything else

Dry cleaning fell from the leading use to a minor one. Stricter workplace rules drove most of that shift. Perc also turns up in paint removers and printing inks. It is used in adhesives, paper coatings, and leather treatments. It appears in spot removers, silicone lubricants, and car cleaners.

The National Toxicology Program calls this chemical reasonably anticipated to be a human carcinogen. It was first listed in the Fifth Annual Report on Carcinogens, in 1989. The basis is sufficient evidence in animals. It is not evidence in people.

The animal findings are specific. Breathing tetrachloroethylene caused benign and malignant liver tumors in mice of both sexes, and mononuclear-cell leukemia in rats of both sexes. In male rats it also raised the rate of tubular-cell kidney tumors, which are rare in rats. Given by stomach tube, it caused liver tumors in mice of both sexes.

Human studies have been harder to read. Dry-cleaning workers rarely met one solvent alone. Trichloroethylene was often present as well. In 1995, IARC concluded the human evidence was limited. That judgment rested on steady links with three cancers: esophageal, cervical, and non-Hodgkin lymphoma. IARC added two cautions. Other chemicals could not be ruled out as the cause. And the combined study groups were small.

EPA reached a firmer position. Its 2005 carcinogen guidelines call this chemical likely to be carcinogenic in humans by all routes of exposure. EPA's own hazard summary lists the diseases involved. Workplace studies have found links with bladder cancer, non-Hodgkin lymphoma, and multiple myeloma. Two of those diseases are covered here in bladder cancer and multiple myeloma.

Workers in dry cleaning, metal degreasing, and fluorocarbon making carry the highest exposure. Air levels in dry-cleaning shops have fallen sharply over five decades:

• 1970s: 350 to 700 milligrams per cubic meter, about 50 to 100 parts per million.
• 1980s: 70 to 350 milligrams per cubic meter, about 10 to 50 parts per million.
• 2003: a mean of 3.8 parts per million across United States facilities.

The highest exposures happen during loading and unloading of the machines.

People who never set foot in a dry cleaner are exposed too. The routes are well documented:

• Apartments and a day-care center in buildings that housed dry cleaners had much higher indoor air levels. Buildings without a dry cleaner were far lower.
• Laundromats show raised levels even months after the dry-cleaning machines are removed.
• Homes storing freshly dry-cleaned clothes in closets can run 2 to 30 times above average background levels.
• Dry-cleaning workers carry the solvent home on skin and clothing. In one study, apartments where dry-cleaning workers lived had indoor air levels more than 10 times higher than other apartments in the same building.

The National Health and Nutrition Examination Survey measured it in blood. In 2013 to 2014, across a sample of 2,970 people of all ages, the 95th-percentile whole-blood level was 0.083 nanograms per milliliter. The level did not vary much by smoking status or race, with one exception. Among male smokers over the age of 50 it was 1.2 nanograms per milliliter, more than ten times the general figure.

Perc reached drinking water in an unusual way. It leached out of the vinyl lining of asbestos-cement water distribution pipes.

Cape Cod, Massachusetts is the documented case. The highest single level reported was 18 milligrams per liter from a pipe in Falmouth. Pipes running along dead-end streets, where water sat longest, measured 1,600 to 7,750 micrograms per liter.

EPA made an estimate for 1985. About 11.4 million Americans were drinking city water holding at least 0.5 micrograms per liter. About 874,000 were drinking water holding at least 5 micrograms per liter.

The solvent has since been detected in rainwater, seawater, rivers, groundwater, dairy products, meats, fats and oils, beverages, fruit and vegetables, bread, fish, and shellfish. FDA's Total Diet Study found it in 67 items. It has even been measured in Antarctic snow.

These are the thresholds that actually apply:

• Drinking water. EPA's maximum contaminant level is 0.005 milligrams per liter. FDA sets the same limit for bottled water.
• Workplace air, OSHA. The permissible exposure limit is 100 parts per million. The ceiling is 200 ppm for 5 minutes in any 3 hours, with an acceptable peak of 300 ppm.
• Workplace air, ACGIH. The threshold limit value is 25 ppm as an 8-hour average, with a short-term limit of 100 ppm.
• Biological monitoring. ACGIH's biological exposure index, measured before a shift, is 3 ppm in end-exhaled air or 0.5 milligrams per liter in blood.
• NIOSH. The immediately dangerous to life and health limit is 150 ppm. NIOSH lists perc as a potential occupational carcinogen and recommends minimizing exposure.
• Spills and waste. The CERCLA reportable quantity is 100 pounds. The RCRA toxicity characteristic leaching threshold is 0.7 milligrams per liter.

One line in the record deserves attention. OSHA says its listed limits were legally enforceable in 2018. It then adds that specific limits may not reflect newer studies. They may not fully protect workers. The gap between OSHA's 100 ppm and ACGIH's 25 ppm is that warning in numbers.

Environmental releases fell sharply. EPA's Toxics Release Inventory recorded 37.7 million pounds released in 1988 and 2.2 million pounds in 2008, a drop of almost 94%. In 2008 most of the remaining releases, from 225 facilities, went to air.

United States imports tell the same story. They ran between 36 million and 140 million pounds a year from 1977 to 2008, then fell below 5 million pounds by 2017.

For most people today, exposure is low and still falling. Two situations are worth raising with a clinician. One is living above or beside a dry cleaner. The other is having a family member who works in one. A closely related solvent with its own listing is covered in trichloroethylene and cancer.

• U.S. Environmental Protection Agency, Tetrachloroethylene Hazard Summary, accessed August 6, 2026
• National Toxicology Program, Report on Carcinogens, 15th Edition: Tetrachloroethylene, accessed August 6, 2026
• U.S. Environmental Protection Agency, IRIS Chemical Assessment Summary: Tetrachloroethylene, accessed August 6, 2026