Introduction Lung cancer is the most frequent cancer, with smoking and radon as the two leading causes. Occupational exposures are another important risk factor, with an estimated population attributable fraction up to 15%.

Objectives This study aimed at assessing the effect of occupational exposures on lung cancer mortality in Switzerland after adjustment for non-occupational lung carcinogens.

Methods We used negative binomial regression to analyse data of 4,351,383 Swiss residents with available occupation, and assess its effect on lung cancer mortality between 1990 and 2014, accounting for socio-demographic factors, smoking probabilities (by age, geographical region, civil status, educational level, nationality, and occupation) and measured environmental exposure to radon.

Results Male machine operators and workers in mining, stone working and building materials manufacturing showed the highest risk with a relative risk (RR) of 2.42 (95%-IC: 2.05–2.87) and 2.08 (95%-IC: 1.50–2.89) compared to health occupations, respectively. In women, two of the largest risks were identified in electronics, watchmaking, vehicle construction and toolmaking (RR : 2.33 (95%-IC: 1.75–3.10)) and transport and traffic occupations (RR : 2.23 (95%-IC: 1.75–2.83)). Smoking RRs were 1.33 (95%-IC: 1.27–1.38) in males and 1.37 (95%-IC: 1.26–1.48) in females, while radon related RRs were not statically significant. Adjusting for socio-demographic factors, the RRs by occupation decreased by 16% and 4% on average in men and women, and by 4% and 6% when adjusting for smoking, but remained statistically significant.

Conclusions The results suggest the presence of occupational exposures to lung carcinogens in addition to non-occupational factors. Longer follow-up and analysis by histological types of lung cancer are needed to improve the estimates of occupational lung cancer.