Occupation and smoking as risk determinants of lung cancer.

The standardized incidence ratio (SIR) of lung cancer was determined for different occupational groups in Finland. The data on all cases of lung cancer diagnosed in Finland in age groups of 35-69 years in 1971-1975 were supplemented by information on occupation from the 1970 census (Central Statistical Office). The expected numbers of cases were based on the sex, age and occupation-specific numbers of person-years computed in the Central Statistical Office, and sex- and age-specific incidence rates of lung cancer among the economically active population (as defined 1 January 1971). Compared with the risk of the total economically active population, the relative risk of those not active (SIR) was 1.69 for men and 0.86 for women. Lower than expected relative risks were encountered among highly educated and white-collar male workers (religious, legal, pedagogical, medical, technical and administrative work), in sales work, transport service work and among farmers. High SIRs were found in mining and quarrying, forestry, woodworking (joiners), construction, painting and among unskilled workers. Among women the numbers of cases were small and only one significant SIR was obtained; the risk was lower than expected in farming. Data on the smoking habits of males in different main occupational categories in Finland show that variation between different occupational groups in the prevalence of smoking closely corresponds to that in the SIR for lung cancer (R = 0.96).