A historic cohort study of the influence of occupational and non-occupational exposure to asbestos

Context: Asbestos exposure is most widely studied as an occupational phenomenon. However, there is emerging evidence of asbestos-related diseases among non-occupationally exposed individuals. Using Ambler, Pennsylvania (PA), a community with substantial occupational and community exposure to asbestos, we aimed to characterize non-occupational exposure to asbestos and its resultant mortality.

Methods: We used publically available census records to identify individuals living in Ambler, PA in 1930. We extracted names, address, gender, race, occupation and industry. Occupational exposure was defined on the basis of an individual’s occupation and listed industry. Paraoccupational exposure was defined as having the same address as an individual with occupational exposure. We calculated summary statistics of demographic variables, tabulated exposures, and used chi-square tests to describe associations among exposure variables and race/gender. 

Results: 4,524 individuals were identified with a median age of 32 years and an interquartile range of 37. Half were male (50.6%), with individuals being predominantly white (87.6%) and a small Black population (12.4%). Only 9.6% of the population had occupational exposure, whereas approximately one third had paraoccupational exposure (36.2%). A smaller proportion of women had occupational exposure compared to males (2.5% vs. 18.3%, p<0001), although the trend was reversed for paraoccupational exposure (38.9% for females, 33.5% for males, p<0.001) A higher proportion of Blacks had occupational (15.7%) and paraoccupational (57.3%) exposure compared to Whites (9.7% occupational, 33.2% paraoccupational) and the differences were statistically significant for both (p<0.001).

Conclusions: In this large cohort of individuals living near a large asbestos manufacturing plant we found significant paraoccupational exposure to asbestos. Additionally, Blacks had significantly higher occupational and paraoccupational exposure to asbestos. Future efforts will focus on characterizing mortality in the cohort as function of occupational and paraoccupational exposure.