Low exposure to asbestos-like mineral from Montana vermiculite may up lung di...( CINCINNATIWorkers exposed to low lev...)

CINCINNATIWorkers exposed to low levels of an asbestos-like mineral from Montana more than two decades ago are at an increased risk for lung disease today, according to research from the University of Cincinnati (UC).

Vermiculite is a mineral with a flaky, fluffy-looking structure. Previous studies revealed that the vermiculite ore mined in Libby, Mont., contained increased levels of an asbestos-like mineral fiber that can become airborne and inhaled when used in manufacturing.

In a 25-year follow-up study of workers at a plant which stopped using Libby vermiculite in 1980, current chest X-rays revealed that 20 percent of workers who experienced low cumulative exposure to these fibers had changes in the lining around their lungs. In the group with the highest exposure, changes on chest X-rays were noted in 54 percent of workers.

James Lockey, MD, senior research investigator, says the study indicates that this particular asbestos-like mineral contained in the Libby vermiculite ore can cause chest X-ray changes at previously unrecognized lower exposure levels.

Workers with low-level exposures to Libby vermiculite ore may not have obvious health effects right away, but the past exposure is something of which their physicians should be aware, says Lockey, a UC professor of pulmonary and environmental health.

Once inhaled, these fibers are very persistent and stay in the lung for a long time, he explains. They lodge in the lung tissue and the tissue that lines the chest wall and cause inflammation, which can lead to chronic lung problems and diseases.

His team reports its findings in the March 15, 2008, issue of American Journal of Respiratory and Critical Care.

Records show that until the Montana mine was closed in 1990, it provided up to 80 percent of the worlds vermiculite supplywhich was widely used in both commercial and residential applications, including home insulation, packing materials,
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