Living with perc

4 May 2002

Perc's under pressure - from regulators, environmental groups and suppliers of more recently developed drycleaning substances. Just how dangerous a chemical is it, asks Glenn Tomkins, and can it be used safely?

It's fair to say that the most commonly used drycleaning solvent - perc - has had a bad press. Reading the USA's National Institute of Environmental Health Sciences's assessment of the substance, one commentator likened it to a description of chemical warfare!

"Short-term exposure to perc can cause adverse health effects on the nervous system that range from dizziness, fatigue, headaches and sweating to incoordination and unconsciousness," the warning stated. "Contact with perc in its liquid or vapour form can irritate the skin, eyes, nose and throat. Long-term exposure to perc can cause liver and kidney damage. Workers repeatedly exposed to large amounts of perc in the air have experienced memory loss and confusion." It is not a pleasant picture.

Then last year, timed to coincide with the Clean '01 exhibition in New Orleans, Greenpeace put the boot in. It's "Out of Fashion" report said that drycleaning customers, workers and the general public were routinely exposed to perc, which it said was a cancer-causing solvent. The report cited a USA National Institute for Occupational Safety and Health study that linked the solvent to 266 workers' cancer deaths in New York, Chicago, Detroit, and San Francisco.

The USA-based International Fabricare Institute was livid. Chief executive officer Bill Fisher fumed: "Greenpeace is an organisation that can do good, but [it] is stuck in its '60 and '70s mode where it sensationalises and misrepresents everything, rather than working to solve the problem." Mr Fisher also said the report was inaccurate, flawed, ignored the many environmental achievements of drycleaners and failed to acknowledge doubts over the reliability of the NIOSH study.

Political game

Greenpeace's timing, however, was more than mischievous. There was a political motivation too. The USA Government at the time was debating whether to give valuable tax credits to drycleaners that bought "green" equipment. Greenpeace wanted these credits applied to new wetcleaning and liquid carbon dioxide machines, while the industry, in the shape of perc manufacturer and supplier Dow Chemical, fought back arguing that the benefits should be extended to include "all advanced equipment technologies", such as its own closed loop system for perc.

Perc - also known as perchloroethylene, PCE and tetrachloroethylene - is what Americans would call a hot potato. The participants, like Dow Chemical and Greenpeace, are high profile and have potentially much to lose. That's not to say, of course, drycleaners would be unaffected if perc's supply was suddenly curtailed. The environmental and health issues are the among the biggest affecting us all. Yet the dangers and hazards associated with perc are, for many, unclear. With so much at stake, it's not surprising the facts become blurred or obscured.

Cutting through the mist

Perc has been used by the drycleaning industry for more than 60 years. In the 1960s its use started to grow as it replaced other solvents, which were generally petroleum-based and therefore flammable. The first regulations affecting drycleaners in the USA were aimed at reducing the risk of fire - a problem perc circumvented. In recent years the quantities of perc consumed have declined as drycleaners have improved the efficiency of their plants and practices and as alternatives to perc have gained some market share.

The reasons for the success of perc are:

• it can be safely stored, handled, and used by observing safety precautions

• it is non-flammable and non-explosive

• it is possible to reclaim a significant amount of the solvent for reuse

• it is an effective cleaning substance.

Perc does not contribute to low-level smog, ozone depletion or the global "Greenhouse effect". It is moderately toxic, "falling into the same classification as many everyday compounds, such as household ammonia and bleach, petrol, antifreeze and nail polish remover," according to IFI. Those using perc should avoid:

• inhalation of excessive amounts of vapour

• prolonged or repeated contact of the liquid with the skin

• swallowing the liquid, or splashing it into the eyes.

In other words, so long as you don't drink it and you exercise common sense when using it, perc's safe. Or is it? The big question, of course, is: does perc cause cancer in humans?

Does it cause cancer?

The USA's Environmental Protection Agency classifies perc as an animal carcinogen, which it has been shown to be, but classifies it between possible and probable human carcinogens. The initial claims that perc might be a human carcinogen were based upon animal tests. A 1977 study conducted by the USA-based National Cancer Institute indicated that perc could induce liver cancer in mice, but not in rats. A 1985 study on rats and mice of both sexes conducted by the USA National Toxicology Program also concluded that there was "clear evidence" that perc could cause cancer in rodents. However, while positive results in animal tests can provide some indication of a compound's potential for giving cancer to humans, the tests are not conclusive.

Occupational exposure studies have also failed to link any cancer risk with occupational perc exposure. Numerous studies have been conducted, but none have conclusively shown any increased risk of cancer caused by perc among those working with it in the drycleaning industry.

Based on the available data, the International Agency for Research on Cancer considers perc to be "probably carcinogenic to humans" (Group 2A). It is considered "reasonably anticipated" to be a human carcinogen by the USA National Toxicology Program. According to the American Conference of Governmental Industrial Hygienists. But available animal and human evidence suggests that perc "is not likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure". In the USA, the Environmental Protection Agency's Science Advisory Board has stated that perc "is an example of a chemical for which there is no compelling evidence of human cancer risk".

Research will continue to take place. Earlier this year the solvents industry started a study of drycleaning workers in four Nordic countries to determine whether workers exposed to perc have an increased risk of cancer. The Halogenated Solvents Industry Alliance says the study intends to produce results that take into account lifestyle factors, such as alcohol and tobacco use, that have been eliminated in earlier studies.

What this means is we don't know whether perc causes cancer in humans. It may and it may not. There have also been suggestions that it can affect the viability of unborn children, but these too are unsubstantiated by research. Greenpeace and other environmental groups oppose drycleaners' use of perc and want it reclassified it as a probable human carcinogen. It's a view with which many have sympathy.

The industry's response has been pragmatic. The IFI says that while it "believes that the best available scientific information indicates that perc is unlikely to be a human carcinogen, the fabricare industry recognises that in situations like this no one can be absolutely certain of non-carcinogenicity". The institute continues: "Our industry is committed to using perc as safely and efficiently as possible, while actively exploring new cleaning technologies."

Using perc safely

Used perc is regulated as a hazardous waste around the world. Storage, transportation, and disposal of waste material, including spent cartridge filters and old equipment, must be conducted in accordance with health, safety and environmental regulations.

Specifics of regulations in various countries vary, but the principles are broadly the same. Drycleaners have a duty to:

• identify their waste as hazardous if it is so

• restrict the amount of hazardous waste stored on their premises

• ensure delivery of hazardous waste to a facility that is authorised to handle it.

In addition, drycleaners should have adequate alarms, fire extinguishers and decontamination and spill control equipment. They should make appropriate arrangements with local emergency services and ensure everyone working on the premises is aware of the safety procedures.

Equally, drycleaners need to be aware of the legal requirements for wastewater that contains concentrations, albeit low, of perc. The amount of perc in the wastewater can be minimised by using a properly sized and properly functioning water separator, which may be connected to condensers, carbon adsorbers, cartridge stripping cabinets, stills and "muck cookers" in drycleaning operations. The amount of wastewater generated by drycleaning facilities depends on the equipment used. It is typically about 50gallons a year, say industry estimates.

Another regulatory trend concerns soil and groundwater contamination. Some states in the USA have imposed regulations on perc drycleaning operations to prevent the release of perc and perc-containing wastes to the surrounding soil and groundwater. Regulations have included requirements for the installation of spill containment structures around drycleaning equipment and storage areas, sealing of floor drains in containment areas, application of floor sealants and the use of closed, direct-coupled systems for the delivery of solvent.

Perc suppliers can be extremely helpful when it comes to satisfying the legal requirements and implementing suitably safe practices. For example, Dow Chemical has a closed-loop delivery system for its Dowper solvent (see panel) and Ineos Chlor can advise on technologies for minimising emissions and reducing consumption of its Perklone solvent.

Consumers' concerns

Greenpeace and other groups have gained publicity by suggesting that perc remaining in clothes after cleaning could be harmful. Similarly, there have been concerns over perc contamination of apartments and buildings close to drycleaners' premises. At one stage Greenpeace claimed that drycleaned clothing "placed in a closed car next to a bag of groceries has contaminated food in less than one hour".

This is undoubtedly emotive rhetoric. While trace levels of perc may remain in clothes after the drycleaning process, there is no evidence to show this is dangerous. Obviously, residual solvent levels can and should be minimised by conducting drycleaning and finishing operations according to equipment manufacturers' specifications.

The industry's view is that if dry-cleaners employ good practices and use well-maintained, up-to-date equipment, there is no reason why perc cannot be safely used.

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