National Clothesline

The latest study of drycleaning workers exposed to perchloroethylene is complete and ready for publication and peer review, the Halogenated Solvents Industry Alliance announced last month.

HSIA, which sponsored the study, said that although the results can’t be released until after the research paper has been peer reviewed, “they do not appear to raise concern regarding perchloroethylene exposure.”

The manuscript should be submitted for publication before the end of the year and will likely be published in a peer reviewed journal in 2005.

The study was designed to determine if workers exposed to perc have an increased risk of cancer. Although similar epidemiological studies have been conducted in the past, HSIA believes this one will provide better data because it focuses on a large population of workers whose exposure histories are better known.

The study identified more than 7,000 drycleaning workers from the 1970 censuses in Denmark, Norway, Sweden and Finland. The census data provided 30 years of medical follow-up and reduced the potential for exposure to other cleaning solvents used prior to that time, HSIA said.

“The size of the population is expected to be large enough to produce a study with reasonably powerful detection capability for even the least common tumor types being studied,” HSIA said. “Incidence of the various cancers among the drycleaning workers was compared to an age- and gender-matched population of laundry workers.”

One benefit of using data from the Nordic countries is that much information is available from surveys conducted by government, industry and other sources due to governments’ deeper involvement in health care and work place issues in those countries. Information on relative perchloroethylene exposures could be obtained based on surveys of working conditions by health inspectors, trade associations, trade unions and academics, and on data concerning the introduction of new equipment types and regulatory changes.

In Denmark, for example, researchers were able to find historical information on the identity of owners of all drycleaning shops and the characteristics of the machines in use at each of the shops.

Also of benefit is the fact that the perc was more widely used in those nations 30 years ago than in the United States. For example, the U.S. industry was about evenly split between perc and petroleum in 1970, while 85 percent of the industry was using perc in Finland, 75 percent in Denmark, and 71 percent in Sweden.

The study also benefited from interviews with the individuals or their next of kin to help fill gaps in the information available from other sources and to allow collection of data on potential confounding factors. The ability to identify lifestyle and other potential factors was a limited of previous studies. Cigarette smoking, for example, is an established risk factor for cancer of the bladder, esophagus, kidney, and pancreas. Alcohol consumption has been associated with both esophageal and liver cancer.

The study looks at the incidence of seven cancer types, including cancer of the bladder, cervix, esophagus, kidney, liver and pancreas, as well as non-Hodgkin’s lymphoma. Incidence of the various cancers among the drycleaning workers will be compared to an age- and gender-matched population of laundry workers.

“The research team of five prominent European epidemiologists was able to collect an unprecedented amount of information on the health and lifestyle of the workers, as well as a significant amount of exposure information,” HSIA said.

HSIA represents companies that manufacture, distribute, and use perc, methylene chloride, trichloroethylene and other halogenated compounds.