Mineral deposit: asbestos linked to lupus, arthritis.

A new study of residents from Libby, Mont., the town where more than 1,500 people have fallen ill from asbestos-contaminated mines, links asbestos exposure with three autoimmune diseases, including rheumatoid arthritis.

Previous research found high rates of asbestos-related lung diseases, including the rare cancer mesothelioma, among miners in Libby. The town's mines once supplied the United States with most of its vermiculite, a mineral used for insulation and gardening. But that vermiculite was contaminated with asbestos also found in the ground there. Residents of Libby who didn't work in the mines, and workers across the country who processed Libby's vermiculite, also had a high incidence of lung diseases (SN: 7/12/03, p. 21).

The new research links asbestos exposure with rheumatoid arthritis, lupus, and scleroderma. "We're talking about a whole different class of diseases," says study author Curtis Noonan of the University of Montana in Missoula. In these diseases, a person's immune system attacks body tissues.

Former Libby miners older than age 65 were three times as likely as other Libby residents to have rheumatoid arthritis and were twice as likely to have any of the three diseases, the study shows. Former miners younger than 65 showed no increased risk, which suggests that prolonged exposure to asbestos increases the chance of illness, Noonan says.

The team reached this conclusion by reexamining a survey given to 7,000 former and current Libby residents in 2000 and by analyzing a follow-up questionnaire sent to people who had reported having at least one of the three autoimmune diseases. In the 2000 survey, 6.7 percent of participants reported having at least one of the diseases. Noonan says that past studies have shown that less than 1 percent of people elsewhere typically have those illnesses.

The new work also found that Libby residents exposed to asbestos in the military had an elevated risk for having at least one of the three diseases, the researchers report in an upcoming Environmental Health Perspectives.

"This might have implications for folks exposed to asbestos not like the type we've seen in Libby," says coauthor Theodore Larson of the federal Agency for Toxic Substances and Disease Registry in Atlanta.

Given the unusually high asbestos exposure faced by Libby residents, these findings "still need to be confirmed in other studies," says public health statistician Laurel Beckett of the University of California, Davis. Noonan and Larson agree.

Meanwhile, a separate investigation into the health effects of asbestos, released last week by the Institute of Medicine in Washington, D.C., found evidence that the mineral causes laryngeal cancer and might be associated with pharyngeal, gastric, and colorectal cancers.