By David Douglas
NEW YORK (Reuters Health) Jul 31 - People born near ophiolites, geological formations often containing asbestos, may have a higher risk for mesothelioma and pleural plaques, a new study shows.
Ophiolites are sections of the earth's oceanic crust and upper mantle that have been thrust up and exposed on land. Naturally occurring asbestos in such formations may pose a significant health risk when human activities or weathering cause fibers to be released in rocks or soils, Dr. Mehmet Bayram and colleagues wrote in a July 17th online paper in Chest.
"Although the main cause of mesothelioma is occupational asbestos exposure, environmental asbestos exposure is an important factor all over the world including Mediterranean countries, California and other sites," said Dr. Bayram, of Bezmialem Vakif University, Istanbul, Turkey, in an email to Reuters Health.
Five of the paper's seven authors are from Turkey - four from the province of Sivas -- and they say they see many patients with pleural plaques and malignant mesothelioma but no known industrial asbestos exposure.
The current report concentrates on 100 patients with malignant mesothelioma and 133 with plural plaques, plus a control group of 161 patients with prostate cancer and 139 with breast cancer. All were born in Sivas, an area with ophiolite formations.
Those with mesothelioma and those with plaques were born significantly nearer to ophiolites than those with prostate or breast cancer. This amounted to a median distance of 4.5 km for men and 0 km (being born within an ophiolite area) for women. In both sets of controls, the median distance was 20 km.
Compared to controls, for each 5 km of proximity to ophiolites at birth, men had a significantly increased risk of having mesothelioma or plaques (odds ratio, 1.6). The corresponding odds ratio for women was 2.0.
The researchers call for prospective studies to look for more links between ophiolites and asbestos-related conditions. In the meantime, Dr. Bayram added, "The current study will help to develop public health strategies to reduce exposure to asbestos from environmental sources including ophiolites which are widely distributed all over the world."
Reuters Health Information © 2012