Californians who live close to naturally occurring asbestos source rocks and who are exposed to low levels of the mineral are at increased risk for malignant mesothelioma, a serious cancer of the pleural membrane covering the lungs, according to a new study.
For the research, investigators looked at 2,908 malignant mesothelioma cases reported over a 10-year period. Over 50 percent of the men and 58 percent of the women listed in the California Cancer Registry either had no or low occupational exposure to asbestos.
(Asbestos fibers can cause tumors in the two layers of membrane covering the lung (the pleura) or, with greater exposure, the membranes of the abdomen. Considered a rare cancer, meosothelioma usually takes 30 to 40 years after exposure to develop.)
According to the authors, California has more naturally occurring asbestos source rocks than any other state in the U.S., but their distribution is patchy, with exposed areas separated from unexposed areas.
The authors noted that the odds of being a mesothelioma case were 6.3 percent lower than the odds of being a study control patient with pancreatic cancer for each 6 miles (10 kilometers) they lived from the nearest asbestos source rocks.
Yet people who lived closer to naturally occurring asbestos deposits had a greater chance of developing the disease.
The authors explained that a major strength of the study was the very large number of mesothelioma cases used to assess the potentially weak association between exposure to naturally occurring asbestos and mesothelioma incidence.
The research appears in the second issue for October 2005 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
PREDICTION RULE DEVELOPED TO DETERMINE RISK OF DEATH FROM PULMONARY EMBOLISM