Chronic bronchitis and bronchial asthma: the impact of chronic occupational radiation exposure on incidence and mortality of Mayak nuclear workers

The information about the radiation risk of non-cancer respiratory diseases is inconsistent and mainly corresponds to mortality. Previously, the cohort of workers employed at the first Russian nuclear facility Mayak Production Association who were occupationally exposed to gamma rays (externally) and to alpha-active plutonium aerosols (internally) over prolonged periods demonstrated an increased risk of chronic bronchitis (CB) incidence. Within this retrospective cohort study, we performed analyses of incidence of and mortality from CB and bronchial asthma (BA) using improved estimates of radiation doses provided by the 'Mayak Worker Dosimetry System (MWDS)-2013'. The cohort included 22 377 individuals hired in 1948-1982, and its follow-up was extended by 10 years (to the end of 2018). The excess relative risk of CB incidence per unit of accumulated lung-absorbed radiation dose (ERR/Gy) and the 95% confidence interval (95% CI) were: with the 0 year lag, ERR/Gy was 0.07 (95% CI -0.01, 0.17) for gamma exposure and 0.36 (95% CI 0.13, 0.68) for alpha exposure; with the 10 year lag, ERR/Gy was 0.15 (95% CI 0.04, 0.30) for gamma exposure and 0.54 (95% CI 0.19, 1.03) for alpha exposure. No strong evidence was found indicating that gamma and alpha exposure considerably impacted the risk of mortality from CB. The study confirmed the significant positive linear association of the CB incidence risk with gamma and alpha radiation doses from occupational chronic external and internal exposure. However, the estimates of ERR/Gy of alpha particles from internal exposure appeared to be almost three times lower than those based on the MWDS-2008 doses. The observed inconsistency requires further clarification. As for BA in Mayak workers, no association was demonstrated in the incidence and mortality risks with occupational gamma and alpha radiation exposure.