Twenty-one of 31 dust samples collected from brake-repair garages in Baltimore, Boston, Chicago, Denver, Richmond, Seattle and Washington, D.C., contained chrysotile, a form of asbestos. The concentration of chrysotile ranged from 2.26 percent to 63.8 percent.

The Environmental Protection Agency requires its workers to wear protective suits and full-face respirators when they enter any area where asbestos contamination is 1 percent or higher.

"If the measurements are valid, that's a very concentrated source of asbestos in the dust," said Aaron Sussell, an industrial hygienist with the National Institute of Occupational Safety and Health in Cincinnati. The most common way people are exposed to asbestos is inhalation, and asbestos-related disease often occurs 15 to 40 years after exposure. Asbestos has been used for a century to line brakes because the heavy woven fiber is one of the best insulation materials known. Asbestos-lined brakes are sold in stores as replacement parts for many older cars and are installed on some new car models.

The EPA, the Occupational Safety and Health Administration and the U.S. Public Health Service issued warnings to high schools and vocational-technical schools in 1986 and 1987 that asbestos in brakes causes cancer, said Steven Johnson, EPA's deputy assistant administrator for the Office of Prevention, Pesticides and Toxic Substances.

But since the early 1990s, the government has stopped paying for federal research programs to find ways to control asbestos exposure among autoworkers.

State agencies, OSHA and the EPA told the newspaper there is no indication auto workers are still being harmed by asbestos, but they conceded they hadn't checked.

"We don't know how many cars that pull into service stations to have their brakes relined have old asbestos linings. We don't know whether these workers are being exposed. We just don't know," said Peter Infante, OSHA's director of the Office of Standards Review.

The National Highway Traffic Safety Administration asks brake manufacturers to certify that their brakes meet certain performance standards, but does not require brake manufacturers to list the ingredients in their brakes.

"That's not something we have jurisdiction over," NHTSA spokesman Tim Hurd said. "We don't test for asbestos in car brakes. It's not covered by any of our safety standards."

The EPA banned asbestos products in 1989, but the Canadian and U.S. asbestos industry sued two years later and got the ban thrown out.

The Post-Intelligencer reported that the makers of 38 car and light-truck models said the brakes on those models no longer contained asbestos. General Motors Corp. said asbestos was still being used in its Chevy Cavalier and the Pontiac Sunbird and Sunfire models.

DaimlerChrysler AG refused to say whether Chrysler and other models use asbestos-lined brakes "for competitive reasons," the newspaper reported.