Association of Mesothelioma Deaths With Cumulated Neighborhood Exposures Due to a Large-Scale Asbestos Cement Plant in Amagasaki City, Japan: A Nested Case-control Study

Background: Although a causal relationship between mesothelioma and asbestos exposure is well known, few studies have shown a relationship to non-occupational exposure, including neighborhood exposure, most likely because of the large effect size of occupational exposure. The aim of this study was to quantify the risk of malignant mesothelioma death associated with neighborhood asbestos exposure due to a large-scale asbestos-cement (AC) plant in Amagasaki, Japan, by properly adjusting for occupational exposure. Methods: We conducted a nested case-control study in which a fixed population of 143,929 residents who had been living in Amagasaki City between 1975 and 2002 were followed from 2002 to 2015. All 133 cases and 403 matched controls were interviewed about their occupational, domestic, household, and neighborhood asbestos exposures. Odds ratios (ORs) for mesothelioma death associated with neighborhood exposure were estimated by a conditional logistic-regression model that adjusted for other asbestos exposures. We adopted cumulative indices that considered residence-specific asbestos (crocidolite) concentrations and durations during the potential exposure period of 1957-1975 to evaluate individual neighborhood exposures.Results: There was an increasing, dose-dependent risk of mesothelioma death associated with neighborhood exposure, demonstrated by ORs in the highest quintile category that were 21.4 (95% CI: 5.8 - 79.2) for all, 23.7 (95% CI: 3.8 -147.2) for males, and 26.0 (95% CI: 2.8 - 237.5) for females, compared to the lowest quintile, respectively. These results clearly demonstrated no substantial differences between males and females in relation to the magnitude of risk from neighborhood exposure.Conclusions: By adjusting for occupational and other asbestos exposures, a dose-dependent relationship was demonstrated between mesothelioma death and neighborhood asbestos exposure from a large-scale AC plant. Our findings suggest that the risk of mesothelioma death associated with neighborhood exposure persists and will not be diminished for many years, even though it has been decades since the AC plant closed.