National Clothesline

The latest study of drycleaning workers has found no increased risk for a number of cancers that earlier studies suggested could be associated with exposure to perchloroethylene.

The study, sponsored by the Halogenated Solvents Industry Alliance and the Danish Medical Research Council, used data from four Nordic countries where occupational and health records are more detailed than those generally found in the Untied States. The study group included all persons who worked in the laundry and drycleaning industry in Denmark, Finland, Norway and Sweden in 1970. Comparing cancer incidence between laundry workers and drycleaning workers provided two groups of workers of similar socio-economic backgrounds whose principal difference was exposure to perc.

The risks of drycleaning

workers for liver, pancreas, kidney and esophageal cancers were not significantly increased, the study found. There was a “borderline significant excess” of cervical cancer for assistants in drycleaning shops but not among workers directly involved in drycleaning.

The study did find an elevated risk of bladder cancer, which did not increase with length of employment, which is an indication of exposure. In previous studies, the risk of bladder cancer was increased in some drycleaner groups but not in others and did not show up in another study that surveyed aircraft workers who were exposed to perc. “The evidence for an association between exposure to tetrachloroethylene (perc) and bladder cancer is equivocal,” the report said.

The study results will appear in an upcoming issue of the journal Environmental Health Perspectives, which is published by the National Institute of Environmental Health Sciences.

One benefit of the using data from Nordic countries is that much information is available from surveys conducted by government, industry and other sources. Based on 1970 census data, all 46,768 persons who were listed as working in laundry and drycleaner were surveyed. Each person was followed up for death, emigration and incident cancer based on linkage with nationwide populations, death and cancer registers. Those determined to have been exposed to perc were categorized according to length of employment between 1964 and 1979 in the shop where they were working in 1970.

Additional data was available in some of the countries. Norway and Sweden could provide data on smoking and drinking. In Denmark, researchers had historical information on the identity of owners of all drycleaning shops and the characteristics of the machines in use at each of the shops. Information on perchloroethylene exposure was also available through surveys of working conditions at the time.

Drycleaning practices differed between the Nordic countries and the United States in 1970 in ways that make the newest study more specific to perc exposure. In 1970, 85 percent of the industry used perc in Finland, 75 percent in Denmark, and 71 percent in Sweden. At the time in the United States, the industry was about evenly split between perc and petroleum, making if more difficult to tell which cleaning solvent workers was exposed to in the earlier U.S-based studies.

In plants that used perc, there was a difference between Europe and the United States, too. Transfer operations, in which clothes wet with perc were manually moved from the cleaning machine to a dryer, were common in the United States while single-unit dry-to-dry machines were already in use in Europe. Thus, exposure to perc in a Nordic drycleaning plant of the 1970s more closely resembles that of a current U.S. plant where dry-to-dry machines are now the norm.

The study, said HSIA was specifically designed to overcome the limitations of earlier studies.

“The result is a study with a significantly improved ability to detect the potential for increases in cancer incidence resulting from exposure to perc,” said Dr. Paul Dugard, science director for HSIA. HSIA represents manufacturers and users of perc and other chlorinated solvents.

Unlike previous studies of drycleaners that indicated an increased risk of esophageal and cervical cancer of of non-Hodgkins lymphoma, the Nordic study found no increased risk. This, the study said, could be due to chance, different confounders or different exposures. Esophageal cancer is associated with smoking, alcohol consumption, hot drinks and poor nutrition, the study noted. Also, due to the use of transfer systems in the United States, U. S. drycleaners had a higher probability exposure to perc both to the skin through the air.

An excess of cervical cancer found both in U.S. studies and in the Nordic study comes with a twist: it only showed up among support staff in drycleaning shops who were not engaged in the drycleaning process. “Drycleaners had no excess risk of cervical cancer,’ the study said.

“In conclusion, drycleaning work in the Nordic countries, during a period where (perc) was the dominant solvent, was not associated with significantly increased risks of cancer of the gastric cardia, pancreas and kidney primary liver cancer and NHK (non-Hodgkins lymphoma),” according to the study.

Further, the study concluded, “We found an elevated risk of bladder cancer among Nordic drycleaners. The international data together point to an excess of bladder cancer in drycleaners of about 45 percent, but there is no pattern with exposure indices.

“The evidence for an association between exposure to (perc) and risk of bladder cancer is equivocal.”