Mortality among Fukushima nuclear emergency workers, 2012-2021

The 2011 Fukushima Daiichi Nuclear Power Plant accident involved approximately 20 000 emergency workers. Given the scale and nature of the accident, concerns have been raised regarding the long-term health of the emergency workers. This study presents the first 10 year overview of mortality among these workers.

We analysed the mortality data for 19 358 male emergency workers (mean age in 2012: 45.5 years; SD: 11.3) from 2012 to 2021. Mortality data were monitored through linkage to national vital statistics, including the dates and causes of death. Standardised mortality ratios (SMRs) with 95% confidence intervals (CIs) were calculated using the general male population in Japan as a reference, standardised by calendar year and attained age (5 year age groups).

During 190 700 person-years of follow-up, 708 deaths were identified. The overall SMR was 0.86 (95% CI 0.80 to 0.93). SMRs for all solid cancers and radiation-associated solid cancers and leukaemia were below 1.0 during 2012-2014, approached 1.0 during 2015-2017 and exceeded 1.0 during 2018-2021, suggesting marginal excess mortality (both P values for trend <0.05). In contrast, the increasing trends were less evident for neoplasms excluding radiation-associated solid cancers and leukaemia. No elevated SMR for suicide was observed.

The overall mortality among Fukushima emergency workers was lower than expected based on general population rates, likely reflecting the healthy-worker effect. However, marginal elevations in SMRs for all solid cancers and for radiation-associated solid cancers and leukaemia emerged during later follow-up, highlighting the importance of continued health monitoring in this population.