Environmental asbestos and incident mesothelioma California, 1988--1997

Several study designs in this dissertation were used to explore the hypothesis that environmental exposure to naturally-occurring asbestos is associated with an elevated risk of malignant mesothelioma in California.; The descriptive study based on 2949 incident mesothelioma cases diagnosed over the time period 1988–1997 in California found that there were significant variations in county-specific mesothelioma risk; mesothelioma risk was about 5 times higher in men than in women; mesothelioma risk increased with age exponentially in men and linearly in women.; The ecological study at the block group level found that mean age was the most significant predicator for mesothelioma; occupational exposure to asbestos, as indicated by asbestosis mortality, was the second most significant predicator for mesothelioma risk only in urban block groups but not in rural block groups; environmental exposure to asbestos, as indicated by the distance to the nearest asbestos sources, was the third significant predicator for mesothelioma only in men but not in women. The survey among former members of asbestos worker union found higher mesothelioma incidence rates in some rural counties could be partially accounted for by immigration of asbestos workers from urban counties to those rural counties. However, we did not observe selective migration to counties known to have larger deposits of naturally-occurring asbestos.; Our cancer registry-based case-control study found that occupational asbestos exposure was strongly associated with mesothelioma risk; the odds ratios and 95% confidence intervals for low, medium, and high occupational exposures to asbestos were 1.92 (1.61–2.30), 2.85 (2.33–3.49), and 13.96 (9.37–20.79), respectively. There was a significant association between the residential distance from the nearest asbestos sources and mesothelioma risk. The odds ratio was 0.979, (95% confidence interval = 0. 961–0.998) after adjusting by age, sex and occupational exposure. There was evidence of a distance-response relationship between the square root of the nearest distance and mesothelioma risk. However, these results were limited by lack of environmental exposure validation, the representativeness of controls, and missing occupational data in the Registry data.