Fact Sheet: Tetrachloroethene (PERC) in Indoor & Outdoor Air (2023)

  • This Fact Sheet is also available in Portable Document Format (PDF, 186KB).

This fact sheet answers questions about a chemical called tetrachloroethene (PERC), which is widely used to dry-clean clothes. It provides information on health effects seen in humans exposed to PERC in air. It also provides information about the New York State Department of Health's new guideline of 30 micrograms of PERC per cubic meter of air (30 mcg/m3) or 0.03 milligrams of PERC per cubic meter of air (0.03 mg/m3). The fact sheet focuses on the health risks from air exposures because most of the PERC released into the environment goes into air.

What is Tetrachloroethene (PERC)?

Tetrachloroethene is a manufactured chemical that is widely used in the dry-cleaning of fabrics, including clothes. It is also used for degreasing metal parts and in manufacturing other chemicals. Tetrachloroethene is found in consumer products, including some paint and spot removers, water repellents, brake and wood cleaners, glues, and suede protectors. Other names for tetrachloroethene include PERC, tetrachloroethylene, perchloroethylene, and PCE. PERC is a commonly used name and will be used in the rest of the fact sheet.

PERC is a nonflammable, colorless liquid at room temperature. It readily evaporates into air and has an ether-like odor. Because most people stop noticing the odor of PERC in air after a short time, odor is not a reliable warning signal of PERC exposure.

How Can I Be Exposed to PERC?

People may be exposed to PERC in air, water, and food. Exposure can also occur when PERC or material containing PERC (for example, soil) gets on the skin. For most people, almost all exposure is from PERC in air.

PERC gets into outdoor and indoor air by evaporation from industrial or dry-cleaning operations and from areas where chemical wastes are stored or disposed. People living in homes located near these operations may be exposed to higher levels of PERC than the general population not living near such operations. Groundwater near these areas may become contaminated if PERC is improperly dumped or leaks into the ground. People may be exposed if they drink the contaminated water. They also may be exposed if PERC evaporates from contaminated drinking water into indoor air during cooking and washing. PERC may evaporate from contaminated groundwater and soil into the indoor air of buildings above the contaminated area. PERC also may evaporate from dry-cleaned clothes into indoor air or may get into indoor air after PERC-containing products, such as spot removers, are used. Indoor air PERC levels may get high if PERC-containing products are used in poorly ventilated areas.

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How Does PERC Enter and Leave my Body?

When people inhale air containing PERC, the PERC is taken into the body through the lungs and passed into the blood, which carries it to all parts of the body. A large fraction of this PERC is exhaled, unchanged, through the lungs into the air. Some of this PERC is stored in the body (for example, in fat, the liver, and the brain) and some is broken down in the liver to other compounds and eliminated in urine. PERC can also be found in breastmilk. Once exposure stops, most of the PERC and its breakdown products leave the body in several days. However, it may take several weeks for all of the PERC and its breakdown products to leave the body.

What Kinds of Health Effects Can Be Caused By Exposure to PERC in Air?

In humans, PERC may affect the central nervous system, the liver, kidneys, blood, immune system, and perhaps the reproductive system. The available data are insufficient to draw conclusions regarding effects of PERC exposure on development in infants and children.

For all health effects, the potential for an increased health risk depends on several factors, including the amount of exposure, the frequency of exposures, and the duration of the exposures. It also depends on the characteristics of the exposed person, such as age, sex, diet, family traits, lifestyle, genetic background, the presence of other chemicals in their body (e.g., alcohol, prescription drugs), and general state of health. Although difficult to quantify, these differences can affect how people will respond to a given exposure. This is known as sensitivity. Differences in sensitivity should be kept in mind when reading the following information on the human health effects of PERC.

  • Short-Term Exposure

    Studies with volunteers show that exposure of eight hours or less to 700,000 micrograms per cubic meter of air (mcg/m3) cause central nervous system symptoms such as dizziness, headache, sleepiness, lightheadedness, and poor balance. Exposure to 350,000 mcg/m3 for four hours affected the nerves of the visual system and reduced scores on certain behavioral tests (which, for example, measure the speed and accuracy of a person's response to something they see on a computer screen). These effects were mild and disappeared soon after exposure ended.

  • Long-Term Exposure

    Numerous studies of dry-cleaning workers indicate that long-term exposure (7 to 20 years, for example) to workplace air levels (41,000 mcg/m3 to 120,000 mcg/m3) caused reduced scores on neurobehavioral or color vision tests, increased levels of biochemical indicators of liver or kidney damage, reduced red blood cells, and blood and immune system effects [increased white blood cells and blood levels of a certain type of antibody (immunoglobulin E)]. The effects were mild and required special tests to be detected. It is not known how long these effects last.

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    The New York State Department of Health (NYSDOH, 2010) measured visual function [visual contrast sensitivity (VCS); color vision]1 in adults and children living in the apartments located in buildings with or without a dry-cleaner using PERC and also measured PERC indoor air levels. PERC levels were higher in the indoor air of apartments in buildings with dry-cleaners. Elevated indoor air PERC levels were associated with a slightly increased risk for children to have decreased VCS scores. The effect of PERC on VCS scores was most noticeable in a small group of children living in buildings with co-located dry cleaners using PERC. In those apartments, indoor air PERC levels ranged from 127 to 710 mcg/m3, with a 50th percentile2 (also known as the median) level of 340 mcg/m3. For affected children (7 years mean duration of residency), the decrease was very small and occurred for only one eye in one of five tests. Mean VCS test scores were still within a normal range. Therefore, the risk for decreased VCS scores among affected children is considered to be small. Elevated indoor air PERC levels were not associated with effects on adult VCS scores, or with color vision of either children or adults. The observed associations between elevated indoor air PERC levels and children's VCS suggests that indoor air PERC levels in the range detected may have subtle effects on the brain.

    A few epidemiological studies showed positive associations between workplace PERC exposure and reproductive effects (increased risk of spontaneous abortion, sperm disorders, and reduced fertility or delayed conception). Data on workplace air levels were not reported or were limited; however, workplace air levels during the times these studies were conducted were considerably higher than those typically found in indoor or outdoor air. These data suggest, but do not prove, that the reproductive effects were caused by PERC and not by some other factor or factors.

    Lastly, epidemiological studies provide a pattern of evidence for a positive association between PERC exposure in the workplace and several types of cancer, specifically bladder cancer, non-Hodgkin lymphoma, and multiple myeloma. These associations were observed in studies with high quality assessments of the likelihood of PERC only exposures. However, data on PERC workplace air levels were not reported, but measurements from other studies indicate that workplace air levels during the times the workers were exposed were considerably higher than those typically found in indoor or outdoor air. Moreover, it is unlikely that the associations were dependent, totally or in part, on factors other than PERC exposures, such as common lifestyle factors as smoking or drinking alcohol. Data from more limited studies suggest that other types of cancer (esophageal, kidney, lung, liver, cervical, and breast cancer) are associated with PERC exposure. In laboratory studies, PERC caused cancer in rats and mice when they ingested or inhaled high doses almost daily for a lifetime. Based on human and animal data, the United States Environmental Protection Agency (USEPA) classifies PERC as "likely to be carcinogenic in humans by all routes of exposure."

What are Background Levels for PERC in Outdoor & Indoor Air in Areas that Are Not Near a Known Environmental Source of PERC?

Various studies provide data on background levels of PERC in outdoor and indoor air. The New York State Department of Environmental Conservation collects data on outdoor air levels of air toxics under the Toxics Monitoring System (also known as Volatile Organics Network). The monitoring sites were selected to provide air quality data from the state's urban, industrial, residential, and rural areas. Based on 5882 samples collected across the state during 1999 to 2008, the 50th percentile (median) and 95th percentile3 PERC levels were 0.41 mcg/m3 and 4.8 mcg/m3, respectively. NYSDOH (2005) conducted a study between 1997 and 2005 on the occurrence of volatile organic chemicals, including PERC, in the indoor and outdoor air of about 100 homes across the state (excluding New York City). Two outdoor samples were collected just outside each home for a total of 200 samples. The 50th percentile and 95th percentile PERC levels were less than 0.25 mcg/m3 and 1.6 mcg/m3, respectively. Finally, the 50th percentile and 95% percentile PERC levels in 587 outdoor air samples collected in 1999-2011 during the investigation of NYS remedial sites not known to have nor suspected to have sources of PERC were 0.52 mcg/m3 and 2.6 mcg/m3, respectively (NYSDOH, 2013b). Collectively, these three data sets, particularly given the low 95% percentile level in the large dataset from the Toxics Monitoring System, indicate that fewer than 5% of the background PERC levels in outdoor air are above 10 mcg/m3.

The NYSDOH, the USEPA, and others have collected and analyzed information on PERC levels in indoor air. The table contains the results from air samples collected inside of buildings that were not near known sources of PERC and other chemicals (for example, a home not known to be near a chemical spill, a hazardous waste site, a dry-cleaner, or a factory). The five studies that reported 90th percentile PERC air levels indicate that fewer than 10% of the background PERC levels in indoor air are above 10 mcg/m3. In addition, the results for six of the eight studies that reported 95th percentiles and contained most of the samples indicate that fewer than 5% of the background PERC levels in indoor air are above 10 mcg/m3. The other two studies (NYSDOH, 2009, 2013b; USEPA, 2001, 2013) indicate that fewer than 5% of the background indoor air levels are above 20 mcg/m3.

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Background Indoor Air Levels in US Buildings (1990-2013)
Study DescriptionSampling YearsNumber of SamplesAir Level Percentiles (mcg/m3)Reference
50th(median)90th a95th
Residential Buildings
Thirteen studies on residential properties, number not reported, in North America1990-20052312bNot Detected - 2.2 (range)cNot Detected - 7 (range)c4.1 - 9.5(range)cUSEPA (2011); also see Dawson & McAlary (2009)
Screening study of 284 households in urban or non-urban areas of Minnesota19972841.4Not Reported4.9Adgate et al. (2004)
Subset of the 101 screened households in Minnesota19971011.3Not Reported5.2
Single family homes, about 100, heated with fuel oil from across New York State, excluding New York City1997-20034000.342.93.9NYSDOH (2005, 2013a)d
Households, about 100 each, in Elizabeth, New Jersey, Houston, Texas, and Los Angeles, California1999-20015540.56Not Reported6.0Weisel et al. (2005)
Sixty-one apartments in New York City building without a co-located dry-cleaner2001-2003612.28.519.09NYSDOH (2009, 2013b)
Office Buildings
Seventy public & commercial office buildings in United States1994-19962091.59.318USEPA (2001, 2013)
Mixed-Use Buildings
Buildings, number not reported, near New York State remedial sites not known nor suspected to have sources of PERC1999-201116250.722.86.6NYSDOH (2013b)
  • a 90% of the results are less than or equal to this value.
  • b Total number of samples, but number of samples associated with each percentile range is less than 2312, but was not reported.
  • c The range from 13, 8, and 5 studies that reported the 50th, 90th, and 95th percentiles, respectively.
  • d One of the 13 studies included in USEPA (2011) and Dawson & McAlary (2009).

What is the New York State Department of Health's New Guideline of PERC in Air?

After consideration of the potential health effects of PERC, background levels of PERC in air, and analytical techniques (the ability and reliability of methods to measure PERC in air), NYSDOH recommends that the average air level not exceed 30 mcg/m3. This determination considered continuous, lifetime exposure and sensitive people. Three other ways of expressing the new guideline are 0.03 milligrams per cubic meter of air (0.03 mg/m3), 4.4 parts per billion (ppb) or 0.0044 parts per million (ppm). This replaces the old guideline of 100 mcg/m3.

An air guideline of 30 mcg/m3 is below the PERC air levels known to cause noncancer effects, including developmental and reproductive effects, in humans and animals, and should be protective against those effects. It is lower than the USEPA's (2012) reference concentration (RfC)4 for PERC of 40 mcg/m3. The estimated excess cancer risk associated with lifetime, continuous exposure to 30 mcg/m3 is about one-in-one-hundred thousand. Decisions about whether to take actions to further reduce exposure are generally made on a case-by-case basis at this level of risk.

However, NYSDOH recommends that reasonable and practical actions should be taken to reduce PERC exposure whenever air levels are above background. The purpose of the guideline is to help guide decisions about the urgency of the actions to reduce PERC exposure. The urgency to initiate these actions and to determine, in a timely manner, whether they have reduced exposure, increases with indoor air levels, particularly when air levels are above the guideline.

Indoor air levels substantially above the guideline indicate a significant PERC source and may require more immediate remedial action. NYSDOH has concerns about lengthy exposure (months to years) to air levels higher than 300 mcg/m3 because the results of a recent NYSDOH study suggested that indoor air PERC levels in apartments (median value of 340 mcg/m3) may have subtle effects on the nervous system (vision function ) of children (NYSDOH, 2010). Thus, NYSDOH recommends taking immediate and effective action to reduce exposure when an air level is equal to or above 300 mcg/m3. In all cases, the specific corrective actions to be taken depend on a case-by-case evaluation of the situation. The goal of the recommended actions is to reduce PERC levels in indoor air to as close to background as practical.

Why Did the Health Department Reduce the Guideline for PERC in Air from 100 mcg/m3 to 30 mcg/m3?

The guideline of 100 mcg/m3 was issued in 1997 and was based on the toxicological data available at the time. Since then, many new toxicity studies have been published and the USEPA has completed a comprehensive, state-of-the-science, peer-reviewed risk assessment of PERC. Based on the risk assessment, the USEPA recommended values for evaluating the potential for noncancer and cancer effects from exposure to PERC in air [a RfC (40 mcg/m3) and an air level (4 mcg/m3) associated with an estimated excess cancer risk of one-in-one million, assuming continuous, lifetime exposure]. NYSDOH staff reviewed the USEPA risk assessment and determined that the recommended values are scientifically robust and should replace the values derived in 1997. The USEPA publication of its RfC (40 mcg/m3) necessitated a re-evaluation of the health-protectiveness of the old NYSDOH guideline (100 mcg/m3) because it has been the past practice of NYSDOH to set guidelines at air levels that are equal to or less than a RfC. Consequently, the guideline was reduced to 30 mcg/m3 after consideration of new toxicity data (e.g., NYSDOH, 2010) and the USEPA risk assessment.

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Should I be Concerned about Health Effects if I am Exposed to an Air Level Slightly Above the Guideline?

The guideline is not a bright line between PERC levels that cause health effects and those that do not. The differences between exposure at the guideline and exposure levels known to cause effects in humans and animals are large. Thus, exposure to levels above but near the guideline will not cause health effects in most, if not all, people. In addition, the guideline is based on the assumption that people are continuously exposed to PERC in air all day, every day for as long as a lifetime. Continuous exposure is rarely true for most people, who, if exposed, are more likely to be exposed for a part of the day and part of their lifetime.

Is There a Test to Determine Whether I Have Been Exposed to PERC?

PERC levels can be measured in the breath for weeks following a high exposure to PERC because it is stored in body fat and is slowly released into the bloodstream and then exhaled in the breath. PERC can be measured in blood. Also, breakdown products of PERC can be detected in the blood and urine for several days after exposure to PERC. Because exposure to other chemicals can produce the same breakdown products in the urine and blood as PERC, the tests for breakdown products cannot determine if you have been exposed only to PERC. Although the tests can show if PERC levels in the body are elevated compared to background levels, they cannot conclusively determine when and for how long a person was exposed, what the source of that exposure was, or whether or not the person will develop adverse health effects.

When Should My Children or I See a Physician?

If you believe you or your children have symptoms that you think are caused by PERC exposure, you and your children should see a physician. You should tell the physician about the symptoms and about when, how, and for how long you think you and/or your children were exposed to PERC.

Where Can I Get More Information?

If you have any questions about the information in this fact sheet, would like to know more about PERC, or are concerned that you may be exposed to elevated levels of PERC, please call the New York State Department of Health at 518-402-7800 or 1-800-458-1158, send an e-mail to btsa@health.state.ny.us or write to us at the following address.

Center for Environmental Health
Bureau of Toxic Substance Assessment
Empire State Plaza-Corning Tower, Room 1743
Albany, New York 12237


  • Adgate JL, Eberly LE, Stroebel C, et al. 2004. Personal, indoor, and outdoor VOC exposures in a probability sample of children. J Expo Anal Environ Epidemiol. 14 Suppl 1:S4-S13.
  • Dawson HE, and McAlary T. 2009. A compilation of statistics for VOCs from post-1990 indoor air concentration studies in North American residences unaffected by subsurface vapor intrusion. Ground Water Monit. Remediat. 29 (3):60–69.
  • NYSDOH (New York State Department of Health). 2005. Study of Volatile Organic Chemicals in Air of Fuel Oil Heated Homes. Albany, NY: Bureau of Toxic Substance Assessment. Last accessed on 04 26 2013 at http://www.health.ny.gov/environmental/indoors/air/fuel_oil.htm.
  • NYSDOH (New York State Department of Health). 2009. Summary Data of the New York City Perc Project. Personal communication from Kim Mazor to Kenneth Bogdan. Albany, NY: Bureau of Toxic Substance Assessment.
  • NYSDOH (New York State Department of Health). 2010. Tetrachloroethylene (Perc) Exposure and Visual Contrast Sensitivity (VCS) Test Performance in Adults and Children Residing in Buildings With or Without a Dry Cleaner. Troy, NY: Center for Environmental Health, Bureau of Toxic Substance Assessment. Last accessed on 04 26 2013 at http://www.nyhealth.gov/environmental/investigations/perc/info_sheet.htm.
  • NYSDOH (New York State Department of Health). 2013a. The 95th Percentile Concentrations of Tetrachloroethene in Indoor and Outdoor Air Samples from the "Study of Volatile Organic Chemicals in Air of Fuel Oil Heated Homes". Personal communication from Todd Crawford to Kenneth Bogdan. Albany, NY: Bureau of Toxic Substance Assessment.
  • NYSDOH (New York State Department of Health). 2013b. Summary Statistics on Tetrachloroethene Air Levels in Indoor and Outdoor Air Samples Collected near NYS Remedial Sites Not Known to Have, or Suspected of Having, Sources of Tetrachloroethene. Personal communication from Kim Mazor to Kenneth Bogdan. Albany, NY: Bureau of Toxic Substance Assessment
  • USEPA (United States Environmental Protection Agency). 2001. Draft: A Standard EPA Protocol for Characterizing Indoor Air Quality in Large Buildings. Washington, DC. Office of Air and Radiation.
  • USEPA (United States Environmental Protection Agency). 2011. Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences (1990–2005): A Compilation of Statistics for Assessing Vapor Intrusion. EPA 530-R-10-001. Washington, DC: Office of Solid Waste and Emergency Response. Last accessed on 04 26 2013 at http://www.epa.gov/oswer/vaporintrusion/documents/oswer-vapor-intrusion-background-Report-062411.pdf.
  • USEPA (United States Environmental Protection Agency). 2012. Toxicological Review of Tetrachloroethylene (Perchloroethylene) (CASRN 127-18-4) in Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/011. Last accessed on 05 23 2013 at http://cfpub.epa.gov/ncea/iris/index.cfm?fuseaction=iris.showSubstanceList&list_type=alpha&view=T.
  • USEPA (United States Environmental Protection Agency). 2013. Building Assessment, Survey and Evaluation Study (BASE). Volatile Organic Compounds Master List. Washington, DC: Office of Air and Radiation. Last accessed on 04 26 2013 at http://www.epa.gov/iaq/base/voc_master_list.html.
  • Weisel C P, Zhang J, Turpin BJ, et al. 2005. Relationships of Indoor, Outdoor, and Personal Air (RIOPA). Boston, MA: Health Effects Institute and Houston, TX: National Urban Air Toxics Research Center.


  • 1 VCS is a measure of a person's ability to distinguish the contrast between a viewed object and its background. It is easier to detect images of high contrast (e.g., a black cat on snow) than low contrast (e.g., a white cat on snow).
  • 2 Half the results are less than or equal to this value and half are above this value.
  • 3 95% of the results are less than or equal to this value.
  • 4 The reference concentration is an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.


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