A Comparative Analysis of Perc Dry Cleaning
and an Alternative Wet Cleaning Process

Executive Summary

A project submitted in partial fulfillment of requirements for the degree of Master of Science at the University of Michigan School of Natural Resources and Environment by Catie Blackler, Richard Denbow, William Levine, Kathy Nemsick, and Ruth Polk: Faculty Advisor: Gregory A. Keoleian.
U-M School of Natural Resources and Environment
Ann Arbor, Michigan; April 1995
Both this document and the complete report may be reproduced freely for non-commercial educational purposes; please remember to cite the source.



Most people don't think about how their clothes are going to be cleaned when they drop them off at a neighborhood dry cleaner. They are only interested in receiving professionally cleaned and pressed clothing, at a reasonable price, within a short amount of time. But the cleaning method a professional cleaner chooses affects the environment, human health, the profitability of the business, the number of regulations with which the business must comply, and the cleanliness and appearance of the clothes.

As concern has increased over the manufacture, use, and disposal of halogenated solvents and chlorinated chemicals, the search for alternatives and pollution prevention strategies has become more urgent. Perchloroethylene (PCE, or "perc") is the chlorinated solvent used by the majority of dry cleaners today. In an effort to reduce perc use, people in the garment care industry and environmental community have been experimenting with, analyzing, debating, and lobbying over an alternative wet cleaning method that would replace the need for perc.

This study is a comparative analysis of two professional clothes cleaning methods: (1) traditional perc dry cleaning and (2) wet cleaning, which uses water and biodegradable detergents in sophisticated washing machines (70 percent) in conjunction with a hand-washing method called multiprocess wet cleaning (30 percent). This study is not a risk assessment of perc. It is a comparison of two cleaning methods, one which relies on a toxic solvent and one which does not. The study uses evaluative techniques from Life Cycle Assessment and Life Cycle Design. It analyzes the use and disposal of cleaning agents, but does not cover the manufacturing and resource extraction impacts of these cleaning agents; therefore, it understates the full environmental impacts, risks, and associated regulatory issues of perc and wet cleaning. The two cleaning methods are analyzed with respect to environmental and human health impacts, cleaning performance, economics, and regulations. The study does not score either cleaning method, but instead provides a framework so that policymakers, regulators, dry cleaners and consumers can assess the relative benefits and disadvantages of both cleaning methods.


Environmental Impacts

Perc is a member of the chlorinated solvents family. There is increasing concern about the use of chlorinated compounds due to their persistence in the environment and their potential to bioaccumulate. There are no known, naturally occurring sources of perc in the environment.

Perc is used by more than 80 percent of U.S. dry cleaners. In 1991, perc consumed by the commercial dry cleaning sector, which consists of about 30,000 machines in operation nationwide, totaled 122,700 metric tons (270 million pounds).

Of this amount, about two-thirds, or 180 million pounds, is released annually into the atmosphere. Some of perc's breakdown components, such as vinyl chloride and phosgene, are toxic to humans; another, trichloroacetic acid, is a known herbicide that causes forest damage.

Most of the remaining 90 million pounds are captured in the form of a solid waste, which is classified as hazardous under the Resource Conservation and Recovery Act (RCRA). Disposal of waste products containing perc must be handled by authorized facilities. Most cleaners pay to have perc-laden waste removed by an off-site disposal service, which reclaims some of the waste and sells the rest to cement kiln incinerators. Perc is also discharged into sewer systems each year in the form of wastewater. Perc can migrate through concrete sewer pipes and also escape through sewer systems which are designed to leak. Once in the soil, perc is mobile and can reach groundwater, where it remains fairly stable. Perc contamination of groundwater has been documented in many areas of the country. For instance, in California's Central Valley region, more than a third of 750 tested wells contained perc, many at levels higher than the permissible limit. Dry cleaning was found to be the likely source of contamination in 20 out of 21 wells that were extensively tested.

A dry cleaning machine using the latest perc technology consumes more electricity to clean a garment than a high-tech wet cleaning machine; this higher demand for energy generation causes more air pollution over time. This is primarily because the dry cleaning machine employs energy-intensive emission control technology equipment, such as refrigerated condensers.

The wet cleaning machine consumes a great deal of water since that, rather than a chemical solvent, is the cleaning medium. Thus, the environmental impacts of using and treating water are much higher with wet cleaning than with dry cleaning. Further study is being done on recycling water, which can reduce wet cleaning's negative environmental impacts.

Human Health Impacts

The National Institute for Occupational Safety and Health (NIOSH) recommends perc be handled as a human carcinogen. The State of California has designated perc as a carcinogen. The International Agency for Research on Cancer plans to revise its classification of perc from "possible" carcinogen to "probable" carcinogen. Currently, the U.S. EPA's unofficial classification of perc falls on a continuum between possible (classification C) and probable (classification B2) human carcinogen. Despite this classification, in 1991 the EPA's Science Advisory Board noted that due to existing levels of uncertainty and the widespread use of perc, it would be wise to reduce workers' exposure.

A 1994 NIOSH study found significant excesses of esophageal cancer and elevated "observed to expected" numbers of deaths from intestinal and pancreatic cancer in populations exposed to perc. A 1993 Boston University study associated perc-contaminated drinking water supplies with an "elevated relative risk" of leukemia and "increased relative risk" of bladder cancer. Previous studies of human populations dealt with people exposed to a variety of solvents used in the dry cleaning industry and thus were unable to isolate the contribution from perc; the NIOSH and Boston University studies are significant because they did isolate perc's effects.

As recently as 1989, the Occupational Safety and Health Administration (OSHA) lowered the Permissible Exposure Limits (PELs) for workers' exposure to perc from 100 parts per million (ppm) to 25 ppm. However, due to a procedural technicality, an industry-sponsored lawsuit overturned the new standard. Although dry cleaners are advised to limit exposure to 25 ppm, workers can still legally be exposed to levels OSHA has ruled unsafe.

Some perc can remain in garments after dry cleaning, resulting in human exposure. According to one study, after 100 days only 40 percent of the perc, which was held in the fiber pores, had diffused to the surface and evaporated.

The adverse health impacts associated with dry cleaning result from exposure to perc and the spotting agents. Wet cleaning, which uses nontoxic detergents, essentially eliminates the known health risks to cleaners and the public associated with perc use.


Perc is an effective clothes cleaning solvent. It dissolves lipophilic stains such as oils, greases, fats, and waxes; does not readily penetrate textile fibers; and evaporates quickly, reducing the potential for garment shrinkage. Perc is non-flammable and easily treated for reuse.

Water can clean many garments, but it is not capable of dissolving lipophilic soils. With wet cleaning, nonchlorinated solvents are used to treat these stains. For the large majority of fabrics, water does not dissolve or weaken fibers or cause bleeding of dyes, and water is compatible with readily available detergents.

Because garment shrinkage results, in part, from over-drying, a wet cleaner must pay special attention to the residual moisture content in a garment while drying. Wet cleaners eliminate shrinkage problems by using specially designed drying machines, which are programmed for specific garments' needs, or by drip-drying.

Environment Canada's Green Clean wet cleaning demonstration project received 177 survey responses during June, July and, August 1994, with 97 percent indicating the clothes were clean overall and 98 percent responding that they would have their clothes wet cleaned again.


Our model facility analysis found that wet cleaning can be an economically viable alternative to dry cleaning. The profitability of wet cleaning depends on many variables, including the cost of labor, equipment, detergents, electricity, and water. Wet cleaning facilities in operation today offer prices similar to those offered by dry cleaners.

Uncertainties exist regarding the amount of labor required for wet cleaning. Because cost estimates are highly sensitive to assumptions about labor, this raises problems in analyzing the profitability of wet cleaning. To achieve the labor productivity required to compete with dry cleaning, the wet cleaner may need to invest in worker training.

Wet cleaning involves significantly fewer up-front capital expenditures than dry cleaning. For example, the cost of an Aqua Clean System washer and dryer is roughly $30,000. In comparison, a similar-size dry cleaning machine costs roughly $54,000.

The cost of perc and charging detergents is significantly cheaper than the cost of wet cleaning detergents and sizing agents. However, dry cleaning entails additional costs associated with disposal of hazardous, perc-contaminated wastes. The disposal costs of perc make it more expensive than the cleaning agents used in wet cleaning.

Wet cleaning involves significantly lower electricity costs than dry cleaning, in large part because dry cleaning uses energy-intensive pollution control equipment. However, these savings are fully offset by wet cleaning's higher water-usage expenses.


Dry cleaners using perc must comply with several environmental statutes, such as the following. The Occupational Safety and Health Act limits permissible exposure levels in the workplace. The 1990 Clean Air Act Amendments (CAAA) regulate emissions to the atmosphere. The Resource Conservation and Recovery Act (RCRA) governs disposal of perc as hazardous waste. The Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) establishes liability for groundwater and soil pollution. There are also various state regulations.

The 1990 CAAAs require Maximum Available Control Technology (MACT) to reduce atmospheric emissions. However, the National Emission Standards for Hazardous Air Pollutants (NESHAP), which were promulgated by the U.S. EPA to meet the CAAA, allow certain cleaners to retrofit and maintain older technology such as vented or transfer machines. Therefore, not all cleaners are using the most effective technology to limit emissions (the closed-loop dry-to-dry machines).

The 1984 RCRA Amendments stipulate disposal methods for perc-contaminated waste; compliance costs for a dry cleaner average several thousand dollars per year.

Historically, dry cleaners have legally poured perc-laden wastewater into the sewer. Under CERCLA, dry cleaners are liable for these past disposal practices if they result in contaminated groundwater or soil. Certain state dry cleaning associations are establishing funds to pay for such liability-related claims.

Enforcement of dry cleaning regulations is based on self-reporting, inventory, and record keeping. Due to the fragmented nature of the industry, the small number of regulatory inspectors, and the abundance of facilities, not all dry cleaners are inspected. Wet cleaners are not affected by the above-mentioned regulations because their detergents are nontoxic and biodegradable; a potential regulatory concern for them is their higher volumes of wastewater. Because dry cleaning uses perc, costly regulations are needed to reduce environmental burden and protect human health. Wet cleaning is a pollution-prevention approach to protecting the environment without costly regulations.


Our study emphasized the importance of five criteria: environment, human health, economics, performance, and regulations. The dry cleaning industry has expressed concern about the economic and performance criteria: if wet cleaning cannot meet the base level of performance established by dry cleaning, it will not be acceptable to customers; if it is not economical for small commercial dry cleaners, it will not be adopted voluntarily. These comparisons are difficult to conduct at this point, since wet cleaning technology and practices are still evolving. Most wet cleaners have been operating for less than one year, and they are being compared to an industry with more than 40 years of experience. Until wet cleaning facilities have been operating long enough to collect empirical data on both cost and performance, dry cleaners will continue to maintain a level of skepticism about the practicality of wet cleaning. The following recommendations address these concerns.

Data Collection

Additional data are needed to resolve uncertainties with wet cleaning. To ensure acceptance and accuracy of the results, tests should be performed with input from all involved stakeholders. The following research activities might resolve uncertainties.


Federal and state governments should help wet cleaners experiment with alternative technologies. Incentives such as the following would encourage cleaners to set up alternative cleaning systems, because the financial risk involved would be reduced.


Dry cleaners need to begin looking critically at their garment streams and experimenting with wet cleaning on appropriate items in order to become more familiar with wet cleaning's potential. To facilitate the on-site implementation of wet cleaning, dry cleaners could do the following:

Information Dissemination

An educational campaign can inform the public and dry cleaners about wet cleaning in order to facilitate its adoption. Efforts may include the following elements.
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