BACKGROUND: The Life Span Study of Japanese atomic bomb survivors estimated greater risks of radiation-associated lung cancer among females than males, with direct implications for occupational radiation safety policy. To evaluate replicability of these findings in radiation workers, we assessed sex-specific radiation-associated risks of lung cancer mortality in a large cohort of U.S. radiologic technologists. METHODS: Using data from four questionnaires (1983-2013), we reconstructed lifetime smoking history for 83,715 female and 26,650 male technologists. We estimated individual lung occupational radiation doses using badge dose and questionnaire data. We used Poisson regression to investigate joint radiation-smoking effects on sex-averaged and sex-specific lung cancer mortality risk. RESULTS: For 1243 female and 607 male technologists who died from lung cancer, median cumulative lung dose was 16.2mGy (non-cases: 7.7mGy) and 24.5mGy (non-cases: 10.1mGy), respectively. Excess risk of lung cancer increased with increasing radiation dose. However, smoking modified this effect: the radiation effect at 100mGy increased until 16 cigarettes/day, after which it declined. Excess relative risk (ERR) per 100mGy was greater among males (never smoking additive ERR = 1.98
95%CI = 0.34, 6.25) than females (never smoking additive ERR = 0.40
95%CI=-0.02, 1.21)
sex-differences persisted up to ∼40 cigarettes/day. CONCLUSIONS: Our results indicated radiation-associated risks of lung cancer mortality were stronger in males than females, in contrast to the Life Span Study. However, both studies found radiation-associated risks were highest in workers with light-to-moderate smoking intensity. Altogether, these findings reinforce the importance of rigorous radiation protection measures for all radiation workers, regardless of sex, alongside interventions to support smoking cessation.