Review date
September 2023
Article publication date
August 2023
Summary
This multinational cohort study investigated the effect of long term low dose and low dose rate exposure to ionising radiation on cancer risk for workers included in an update to The International Nuclear Workers Study (INWORKS). INWORKS includes data from cohorts of nuclear workers with personal dosimeters in France, the UK, and the US. Overall, the study included 309 932 workers. The study found the excess relative risk of mortality due to solid cancer with cumulative dose to be 0.52 (90% confidence interval 0.27 to 0.77) per gray (Gy). Smoking and asbestos exposure were investigated as confounders by excluding deaths from lung cancer and pleural cancer, and it was determined that they did not have a substantial effect. The results of this study show an increase in the relative rate of cancer mortality with increasing exposure to ionising radiation. The study notes that the estimated excess relative risk is even greater than estimates currently informing radiation protection.
Link to
Published in
BMJ
ARPANSA commentary
The study reports evidence of an increase in the excess relative risk of solid cancer mortality with increasing cumulative exposure to ionising radiation at low dose rates. This is consistent with the current approach to radiation protection where a linear association between cumulative low dose ionising radiation and solid cancer is assumed, primarily informed by studies of atomic bombing survivor cohorts (WHO). The reported findings are also consistent with the majority of epidemiological studies investigating low dose exposure and cancer mortality (Rühm et al., 2022 and Hauptmann et al., 2020).
The INWORKS study does not have individual level data on some potentially important confounding factors, such as smoking and asbestos. The impact of these factors could only be indirectly assessed by excluding related cancers from the study. Lack of individual level data means the impact of these factors could not be measured empirically.
A cohort study (Sokolnikov et al., 2015) of workers employed at Mayak facilities for plutonium production, which has been influential in impacting estimates of excess relative risk in literature reviews due to its size and high magnitude doses, estimated an excess relative risk three to four times lower than the INWORKS study.
ARPANSA aims to ensure the highest standard of protection against the harmful effects of radiation to people and the environment, which is outlined in relevant Codes and Safety Guides. The requirements in Australia for the protection of both occupationally exposed people and members of the public for planned exposure situations are outlined in the Code for Radiation Protection in Planned Exposure Situations (2020), RPS C-1 (Rev.1). The annual exposure limits to ionising radiation, across all Australian jurisdictions, is 1 milliseiverts (mSv) for the public and 20 mSv for the occupationally exposed.
