A Comparative Analysis of Perc Dry Cleaning
and an Alternative Wet Cleaning Process
Executive Summary
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.
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.
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.
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.
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.
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.
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last revised: August 18, 1998.