Occupational exposure and lung cancer risk.

The importance of occupation held longest as a risk factor for lung cancer was examined in a prospective study in Norway of 11,995 men, among whom 125 cases occurred in a follow-up from 1966 through 1978. Based on information about occupation held longest, the respondents were classified into 3 groups according to suspected exposure to respiratory carcinogens at the workplace. After stratification for age, place of residence and cigarette smoking, we found a highly significant relative risk of 2.6 for those judged to have experienced definite exposure versus the group with no workplace exposure. The apparent risk-enhancing effect of occupational exposure was observed for all histologic subtypes. Stratification including a socioeconomic factor score led to a moderate reduction in the relative risk estimate. High risk estimates still obtained, however, for a limited number of occupations, the highest for workers in the mining and quarrying industries. Although the interpretation of the observed effect associated with a crude index of occupational exposure may be difficult, our results suggest that between 13 and 27% of the lung cancer cases observed among Norwegian men in the relevant time period can be attributed to harmful work-place exposure.