The Environmental Protection Agency is preparing to launch an expedited review of methylene chloride, a chemical used widely in paint removers, aerosol sprays and decaffeinated coffee, because of new evidence that it can cause cancer in laboratory animals.
EPA officials said the decision is based on recent studies by the National Toxicology Program that showed the chemical induced cancerous liver and lung tumors in mice and noncancerous tumors in rats.
Industry officials disputed the significance of the tests, noting that earlier studies had found little or no cancer-causing effect from methylene chloride. At least 240,000 tons of methylene chloride are sold in the United States each year, according to industry figures. More than half of it is used in paint removers and aerosol products, including spray paint, hair spray and insecticides.
The chemical also is used in food processing, mostly to remove caffeine from coffee beans and resins from some spices.
The action, expected to be announced next week, is being taken under a rarely used provision of the Toxic Substances Control Act that requires the EPA to make a regulatory decision within 180 days. At the end of that time, the EPA will have to propose new controls on methylene chloride or issue a finding that it does not pose a significant cancer risk to humans. Consumers are exposed to methylene chloride in dozens of products, from paint removers and antiperspirants to air fresheners, but the EPA said its accelerated review will not deal with those applications because the agency does not have good information on typical exposure levels.
Instead, the review will concentrate on occupational exposures and on methylene chloride in the air, where it frequently ends up when it is vented from industrial plants that use the substance to strip paint or remove grease and oil.
"Clearly, there's a worker-exposure issue," said John A. Moore, head of the EPA's toxic substances division, who said the agency's "conservative" risk assessments estimate a cancer risk as high as one in 100 for some workers.
"I don't believe that literally," he said, "but it's sufficient to suggest a potential risk."
Industry representatives said they intended to "cooperate as much as possible" with the EPA, but they discounted the new federal studies as "inconclusive."
"We're doing a couple of other studies to try to understand the mouse performance," said Charles Beck of Diamond Shamrock Chemical Co., a leading supplier of methylene chloride. "There is considerable scientific concern about that being a relevant animal to assess cancer risk to humans."
But Beck and other industry representatives said that the study underscores the need for caution in handling such household products as paint strippers and spray paints. While decaffeinated coffee contains minute residues of the chemical, homeowners who use a common nonflammable paint stripper -- which can contain up to 80 percent methylene chloride -- in a closed room can be exposed to short-term levels as high as 800 parts per million (ppm), industry tests show.
"That's pretty high," Beck said. He said the commonly accepted industry safety standard is 100 ppm averaged over an eight-hour day, even though the Occupational Safety and Health Administration permits up to 500 ppm. Beck said the industry believed its standard has "plenty of a safety factor based on what we know now."