Exposure to Asbestos-Containing Rock Can Cause Mesothelioma

By Megan Rauscher

NEW YORK OCT 26, 2005 (Reuters Health) - Living in close proximity to naturally occurring asbestos found in rock significantly increases the risk of malignant mesothelioma, an asbestos-related cancer, a study by California researchers shows.

"The importance of this study is that it provides scientific data that mesothelioma occurs from naturally occurring asbestos in California, and by inference in the United States," Dr. Marc B. Schenker from UC-Davis told Reuters Health. "This indicates that public health officials need to shift their focus to addressing this issue and not continuing to debate whether it is an issue at all," he added.

In the October 15th issue of the American Journal of Respiratory and Critical Care Medicine, Dr. Schenker and colleagues point out that California has more naturally occurring asbestos source rocks than any other state in the US, but their distribution is "patchy, with exposed areas separated from unexposed areas."

The researchers matched 2908 Californians who developed malignant mesothelioma over a 10-year period to 2908 "control" Californians with pancreatic cancer.

Logistic regression analysis from a subset of 1133 mesothelioma cases and 890 controls showed that the odds of mesothelioma decreased roughly 6.3% for every 10 kilometers (6 miles) farther they lived from the nearest asbestos source rocks.

"People who lived closer to an asbestos source had a greater chance of having mesothelioma, and the chance decreased steadily as the distance increased," Dr. Schenker and colleagues report.

"These findings were adjusted for occupational exposure to asbestos, age at initial diagnosis, and sex," the authors note.

The study, they conclude, shows an independent and dose-response association between residential proximity to naturally occurring asbestos and mesothelioma risk.

Co-authors of a related editorial call the data important and convincing. Drs. Marcel Goldberg and Daniele Luce from INSERM, Saint Maurice, France, say "additional work is now necessary for an accurate assessment of the levels of cumulative exposure that people experience in areas where an excess risk of pleural mesothelioma was observed."

SOURCE:

• Am J Respir Crit Care Med 2005;172:939,1019-1025.