A report from the Agency for Toxic Substances and Disease Registry said that employees, their families and people living close to 28 exfoliation sites may have been exposed to amphibole asbestos from vermiculite mined in Libby between the 1920s and the early 1990s.

Workers were exposed to asbestos through a process called exfoliation, in which vermiculite is heated until it expands. Since the Libby vermiculite contained asbestos, heating released asbestos fibers into the air where they could be inhaled, the report said.

Asbestos has been linked to pulmonary diseases including asbestosis, lung cancer, and mesothelioma and 15 to 30 years can pass from a person's exposure to the time disease develops.

People who believed they may have been exposed to amphibole asbestos are encouraged to discuss this with their healthcare professional, the report said.

In addition, the agency also recommends that exposed persons stop smoking, as smoking combined with asbestos exposure greatly increases the risk of developing lung cancer.

More information is at: www.atsdr.cdc.gov/asbestos/sites/national_map.