Individuals who have prolonged exposure to low-dose ionising radiation have a higher risk of death from cancer than previously thought, a new study suggests.
The researchers, who tracked and analysed deaths among 309,932 workers in the nuclear industry in the UK, France, and the US (INWORKS), say their findings should inform current rules on workplace protection from low-dose radiation.
Estimates of the effects of radiation on the risk of dying from cancer have been based mainly on studies of survivors of atomic bombs dropped on Japan at the end of the Second World War.
It is these estimates that are used to set the level of protection required for workers who are regularly exposed to lower doses of radiation in the nuclear industry and sectors such as healthcare.
However, data from the International Nuclear Workers Study (INWORKS) suggest that risk estimates may underestimate the cancer risks from exposure to lower doses of ionising radiation over a long time in the workplace.
To analyse this, the team, from the USA, UK, France and Spain, tracked and analysed deaths of the 309,932 workers in the nuclear industry between 1944 to 2016. The researchers included experts from the UK Health Security Agency and were led by Professor David Richardson, of the University of California, Irvine, USA.
During the monitoring period, 103,553 workers died, 28,089 of whom had solid cancers and the team estimated the risk of death from solid cancers based on workers exposure to radiation 10 years previously.
They estimated this risk increased by 52% for every unit of radiation (Gray; Gy) workers had absorbed. A dose of one Gray is equivalent to a unit of one Joule of energy deposited in a kilogramme of a substance.
When the analysis was narrowed to workers who had been exposed to the lowest cumulative doses of radiation (0-100 mGy), this approximately doubled the risk of death from solid cancers per unit Gy absorbed.
The team also restricted the analysis to workers hired in more recent years, when estimates of occupational external penetrating radiation dose were more accurate, and also found an increased risk of death from solid cancer per unit Gy absorbed.
They add that excluding deaths from cancers of the lung and lung cavity had little effect on the strength of the association.
The researchers acknowledge some limitations to their findings but say: “People often assume that low dose rate exposures pose less carcinogenic hazard than the high dose rate exposures experienced by the Japanese atomic bomb survivors. Our study does not find evidence of reduced risk per unit dose for solid cancer among workers typically exposed to radiation at low dose rates.”
They say they hope organisations such as the International Commission on Radiological Protection will use the findings to update their recommendations for radiological protection.
Richardson DB, Leuraud K, Laurier D et al. Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study. BMJ 17 August 2023; doi: 10.1136/bmj-2022-074520
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