Possible effect of environmental exposure to asbestos on geographical variation in mesothelioma rates.

BACKGROUND

In population-based mesothelioma studies in industrialised countries, the incidence of mesothelioma without any identified asbestos exposure (IAE) is usually higher among women, while male incidence is mainly attributed to IAE. Through a comparison of the spatial distribution of male and female rates, and IAE and no IAE incidence, this study investigated whether mesotheliomas without IAE are in fact induced by non-recognised asbestos exposure, mostly from environmental sources.

METHODS

We calculated mesothelioma mortality (SMR) and incidence (SIR) ratios by district in France, pooling 30 and 10 years of data, respectively. Using correlation coefficients, we compared geographical patterns of male and female mesothelioma ratios, and IAE and no IAE mesothelioma ratios.

RESULTS

The raw numbers of male and female mesothelioma cases were equivalent. Mesothelioma SMR (0.76) and SIR (0.80) geographical correlations between men and women were strongly positive. SIR correlation between occupationally IAE and no IAE cases was also positive (0.69). Correlation between occupationally IAE and no IAE cases was positive among women but not among men.

CONCLUSIONS

Data analyses of mesothelioma mortality and incidence showed that female cases occur in the same geographical areas as male cases. Female mesotheliomas with no IAE occur in the same geographical areas as exposed cases, suggesting asbestos has a major influence on female mesothelioma, likely through environmental exposure.