Continuous exposure to low-dose radiation creates a cancer risk that should be minimised, according to a study published today.
The new study has provided a direct estimate of the link between low dose exposure to radiation and the risk of death from solid cancers.
Ionising radiation is now an established cause of cancer, but current safety standards are based on studies of people exposed to acute, high doses.
Associate Professor David Richardson of the University of North Carolina, USA, and colleagues looked at workers exposed to radiation at low dose rates typically encountered in nuclear industries.
They used figures on exposure to ionising radiation from 308,297 workers in the nuclear industry in the UK, France and the US. Details were linked to death registries. Of 66,632 known deaths by the end of follow-up, 17,957 (27%) were due to solid cancers.
Analysis pointed to a "linear increase in the rate of cancer with increasing radiation exposure".
In The BMJ, the authors report that the average cumulative dose was 20.9 mGy. The mortality rate from all cancers, excluding leukaemia, rose by 48% per Gy, with a ten year delay.
Similar associations were seen in each country, they add.
Dr Richardson said last night: "For all cancers considered together, the risk increased linearly with external radiation dose.
"Restricting the analyses to workers exposed to low doses resulted in similar estimates of risk per unit dose, indicating that the risk estimates are applicable to workers who received a wide range of occupational exposures and that the risk per unit dose is similar over the whole dose range."
He explains that the previously-observed link between solid cancer mortality and ionising radiation after acute exposure "is also valid in situations of low protracted exposures found in the workplace".
"This information emphasises the need for continued efforts to reduce ionising radiation exposure to levels that are as low as are reasonably achievable," he concludes.
Richardson, D. B. et al. Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS). BMJ 21 October 2015 doi:10.1136/bmj.h5 [abstract]
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