American Journal of Respiratory and Critical Care Medicine. 2005, doi:10.1164/rccm.200412-1731OC. [Link]

Xue-lei Pan1, Howard W Day2, Wei Wang3, Laurel A Beckett1, and Marc B Schenker1*

1 Department of Public Health Sciences, University of California at Davis, Davis, CA, USA, 2 Department of Geology, University of California at Davis, Davis, CA, USA, 3 Department of Biostatistics, Harvard School of Public Health, Boston, MA, USA


Rationale: Little is known about environmental exposure to low levels of naturally occurring asbestos (NOA) and malignant mesothelioma (MM) risk.

Objectives: To conduct a cancer registry based case-control study of residential proximity to NOA with MM in California. Methods: Incident MM cases (n=2908) aged 35+ years diagnosed between 1988 and 1997 were selected from the California Cancer Registry (CCR) and frequency-matched to pancreatic cancer controls (n=2908) by 5-year age group and sex. Controls were selected by stratified random sampling from 28,123 incident pancreatic cancers in the same time period. We located 93.7% of subjects at the house or street level at initial diagnosis. Individual occupational exposure to asbestos was derived from the longest held occupation, available for 74% of MM cases and 63% of pancreatic cancers. Occupational exposure to asbestos was determined by a priori classification and confirmed by association with mesothelioma.

Main Results: The adjusted odds ratios and 95% confidence intervals (CIs) for low, medium, and high probabilities of occupational exposures to asbestos were 1.71 (1.32-2.21), 2.51 (1.91-3.30), and 14.94 (8.37- 26.67), respectively. Logistic regression analysis from a subset of 1133 mesothelioma cases and 890 pancreatic cancer controls showed that the odds of mesothelioma decreased approximately 6.3% for every 10 kilometer farther from the nearest asbestos source, an odds ratio of 0.937 (95% CI=0.895-0.982), adjusted for age, sex, and occupational exposure to asbestos.

Conclusions: These data support the hypothesis that residential proximity to NOA is significantly associated with increased risk of MM in California.