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Looking Good, Feeling Bad; or, What's the Problem with Perc (Percholorethylene)?

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By Jennifer Manning

[March 7, 2006]

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"We all may be exposed to perc because it is found in the air and drinking water nationwide." - EPA Design for the Environment

Putting on your fresh, dry-cleaned clothes, have you ever noticed that sweet odor? It is not enough to bother many people, and after a few minutes as you rush off to work you likely will forget about it, but it's not something that should be forgotten: it is toxic, it is chemical, and you are wearing it next to one of your body's most sensitive organs: your skin.

And it is worth noting that its distinguishing characteristic is its odor, since the breathable form is the most common way for people to be exposed to it. In fact, breath analysis is a widely accepted method of testing for exposure. It is perc, aka percholorethylene, PCE, tetrachloroethylene, and tetrachloroethene ("perc" will be used herein as a synonym for these chemicals).

What is Perc?

The chemical commonly known as perc has been with us since 1821, when British physicist and chemist Michael Faraday synthesized tetrachloroethylene. Tetrachloroethylene is a clear liquid with a somewhat harsh, sweet smell with an odor threshold of 1 part per million (ppm). This means that most people can smell it when it is present in the air at this relatively low level, although more sensitive persons may smell it at even lower amounts.

While it has been argued that some perc is natural and produced by algae (American Council on Science and Health [ACSH, 2001), it is generally considered a strictly manmade, artificial material. According to the Environmental Protection Agency's (EPA's) Office of Pollution Prevention and Toxics (OPPT), it "does not occur naturally but is produced in large amounts (310 million pounds in 1991) by three companies in the United States" (EPA OPPT, 1994).

Not only is perc used for dry cleaning, it is also used for metal degreasing - two uses that would seem incompatible. There are also other sources of perc - it is used in shoe polish, printing inks, textiles, and other manufactured products. However, perc is used the most by dry cleaning establishments, and they use a lot of it: it is estimated that 80 to 85 percent use the chemical.

Many National Priorities List (NPL) sites (Superfund sites) are contaminated by perc. According to the Agency for Toxic Substances and Disease Registry (ATSDR), perc has been found in at least 771 of the nation's 1,430 NPL sites (ATSDR, 1997).

A Brief History of Dry Cleaning

Most of us have never even seen the inner workings of a dry cleaning plant. To understand what a dry cleaning machine looks like, imagine something that is a hybrid of your home washing machine and clothes dryer. "Dry cleaning" is something of a misnomer since liquids such as perc are involved.

The earliest dry cleaners used petroleum-based solvents including fuels such as gasoline and kerosene. Needless to say, these cleaners were the perpetrators and victims of many fires and explosions. As a result, dry cleaning became a heavily regulated industry.

Perc was introduced to the U.S. dry cleaning industry around 1934, and was considered a better cleaning agent than the once-favored petroleum-based products. Perc's popularity was also fueled by petroleum shortages caused by World War II. In addition, "because perc was not considered a fire hazard, professional cleaners were able to move into residential and commercial areas of cities. By the early 1960s, perc became the most widely used dry cleaning solvent in the United States. It was not until the late 1970s that increasing evidence demonstrated perc use by professional dry cleaners to be harmful to human health and the environment" (Coalition for Clean Air, 2002).

Today, according to the Centers for Disease Control's (CDC's) National Institute for Occupational Safety and Health (NIOSH), "The commercial drycleaning industry in the United States consists of approximately 36,000 shops. Most of these shops are small businesses with fewer than 10 employees. Approximately 85% of drycleaning shops in the U.S. use perchloroethylene as their primary solvent" (CDC NIOSH, 2006).

What Does the Science Say about Perc Exposure?

The EPA monitors perc through several of its offices and laws or regulations, including the Office of Pollution Prevention and Toxics (through the Toxic Substances Control Act), air (through the Clean Air Act), the Office of Solid Waste and Emergency Response (through Superfund), and water (through the Clean Water Act and the Safe Water Drinking Act).

Chemicals are typically assessed in terms of acute (short-term) exposure and chronic (long-term) exposure. Within those exposure terms there are varieties of exposure: e.g., dermal contact, inhalation, ingestion, etc.

The following is a summary of the state of the scientific knowledge of perc based on studies reported on EPA's Technology Transfer Network (TTN) website (EPA TTN, 2000):

  • Acute effects from exposure to perc include irritation of the upper respiratory tract and eyes, kidney dysfunction, and neurological effects (mood and behavioral changes, impairment of coordination, dizziness, headache, sleepiness, and unconsciousness).
  • Chronic, non-cancerous effects from inhalation include neurological effects, impairments in cognitive and motor neurobehavioral functioning, and color vision decrements. Other effects noted in humans include cardiac arrhythmia, liver damage, and possible kidney effects.
  • Cancer risk, based on studies of dry cleaning workers who were exposed, may include an increase in a variety of cancers (esophagus, kidney, bladder, lung, pancreas, and cervix). However, it should be noted that these studies are complicated by potential exposure by these workers to other chemicals, and that lifestyle choices such as drinking alcohol and smoking were not factored into the studies.
  • Reproductive/developmental effects have been reported in studies of dry cleaning workers. These include spontaneous abortions, menstrual disorders, altered sperm structure, and reduced fertility; however, no definitive conclusions can be made because of study limitations.

EPA considers perc to be an air and water toxin. The agency also notes that repeated skin contact may cause irritation. For example, increased incidence of some cancers and other illnesses in dry cleaning workers is likely due to dermal exposure, as workers handle the chemical. In the mid-1980s EPA considered the epidemiological and animal evidence on perc as "intermediate between a probable and possible human carcinogen (Group B/C)... but is currently reassessing its potential carcinogenicity" (EPA TTN, 2000).

The most hazard from perc is via occupational exposure, primarily in dry cleaning establishments and at industries manufacturing or using the chemical (EPA TTN, 2000). According to Greenpeace, a NIOSH study "found that dry cleaning workers exposed to perc suffered an elevated death rate from several forms of cancer" (Greenpeace, 2003).

Other organizations are concerned about dermal contact: "Serious, negative health effects are also suffered by people who live above dry cleaners, and others still are directly exposed to perc from their dry cleaned clothes" (Greenpeace, 2003).

Also, according to EPA, "High perc levels in residences would be of special concern for irritation and other health effects, including a potential for cancer for occupants who are at home a lot and might be exposed to perc for extended periods of time, such as the elderly, young children, or pregnant women. Scientists do not know if perc exposures cause developmental changes in children" (EPA DFE, 2005).

CONTINUED: Effects of Perc on the Environment

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