Ionizing radiation and solid cancer mortality among US nuclear facility workers

Abstract

Background The risk of solid cancers from low-level protracted ionizing radiation is not well characterized. Nuclear workers provide valuable information on the effects of ionizing radiation in contemporary exposure scenarios relevant to workers and the public. Methods We evaluated the association between penetrating ionizing radiation exposure and solid cancer mortality among a pooled cohort of nuclear workers in the USA, with extended follow-up to examine cancers with long latencies. This analysis includes 101 363 workers from five nuclear facilities, with 12 069 solid cancer deaths between 1944 and 2016. The association between cumulative equivalent dose measured in sieverts (Sv) and solid cancer subtypes were modelled as the excess relative rate per Sv (ERR Sv–1) using Cox regression. Results For the association between ionizing radiation exposure and all solid cancer mortality we observed an elevated rate (ERR Sv–1=0.19; 95% CI: –0.10, 0.52), which was higher among a contemporary sub-cohort of workers first hired in 1960 or later (ERR Sv–1= 2.23; 95% CI: 1.13, 3.49). Similarly, we observed an elevated rate for lung cancer mortality (ERR Sv–1= 0.65; 95% CI: 0.09, 1.30) that was higher among contemporary hires (ERR Sv–1= 2.90; 95% CI: 1.00, 5.26). Conclusions Although concerns remain about confounding, measurement error and precision, this analysis strengthens the evidence base indicating there are radiogenic risks for several solid cancer types.

Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study

“…Analyses of mortality among French nuclear workers showed a positive association between estimated colon dose and solid cancer mortality (excess relative rate 0.69 (95% confidence interval −0.28 to 1.77) per Gy)58; we note that INWORKS includes a sizable fraction of this cohort. Analyses of mortality among US nuclear workers showed a positive association between cumulative dose and solid cancer mortality (excess relative rate 0.19 (95% confidence interval −0.10 to 0.52) per Gy), which was of larger magnitude among workers first hired after 196059; again, we note the overlap between this cohort and INWORKS. Analyses of cancer incidence among workers in the UK National Registry for Radiation Workers (UK NRRW) showed a positive association between external dose and solid cancer incidence (excess relative rate 0.20 (95% confidence interval −0.00 to 0.43) per Sv), although a linear model seemed to overestimate risk at higher doses, such that a linear-exponential model fitted the data better than a linear model, with the linear component of the model yielding an excess relative rate per Sv of 1.14 (0.30 to 2.36) 60.…”

Extended analysis of solid cancer incidence among nuclear industry workers in the UK 1955–2011: comparison of workers first hired in earlier and later periods

“…Also shown are results for the full cohort and the external exposure only workers sub-cohort separately by period of first hire before and after the beginning of the years 1960, 1965 and 1970. To compare, table 1 also presents the estimates of the linear ERR from the US study [3] for the full cohort and for workers first hired after the beginning of 1960, and also from the INWORKS cohort for workers first hired from the start of years 1958 and 1965, and before 1958 [4]. It is unfortunate that the results were not presented for the pre-1960 hire sub-cohort in the US study and for the pre-1965 hire sub-cohort in the INWORKS.…”

“…Doses from neutrons and intakes of radionuclides are not generally computed in the NRRW or in the US study. Adjusting for neutron monitoring or considering those workers who had potential internal exposures makes interpretation of external radiation (x-ray plus gamma) effects uncertain in the NRRW and the US studies, as well as in the INWORKS [1,3,9,10]. Annual recorded whole-body dose in the NRRW includes x-ray and gamma exposure plus neutrons and tritium, but the information about neutrons and tritium is limited.…”

“…The analysis in both INWORKS and the US study include an adjustment for neutron monitoring status. However, deviations from the linear model were not examined in detail in the US study [3] or in the INWORKS [4], although there was some suggestion of downward curvature in the INWORKS solid cancers dose-response [4].…”

“…Recent analyses of data from nuclear industry workers in the United Kingdom's National Registry for Radiation Workers (NRRW) [1,2] and from nuclear industry workers from five sites in the United States of America [3] have shown raised risks for the grouping of all solid cancers combined following protracted low-dose exposure to low-LET radiation, such as x-rays and gamma radiation. However, the US study found that the risk estimates were significantly greater for those 56% of workers first hired in 1960 or later in comparison with the full cohort of 101 363 workers, for all solid cancers combined and for certain individual site-specific solid cancers, such as lung, colon, and pleural cancer.…”