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Risks from low-level ionizing radiation are small compared to smoking, obesity and air pollution, researchers say.



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Oxford Martin restatement finds that health risks from radiation exposure are extensively studied and small relative to risks from modern lifestyles.

Human populations have always been exposed to ionizing radiation, and more so in modern life due to its use in medicine, industry and the military.   Whilst the risks to human health from medium- and high-level radiation are relatively well-understood, the risks at lower levels are debated.  Mixed messages about the safety of low doses of radiation from different sources create confusion for the public and for policy makers.  

Now a team of experts led by Professor Angela McLean, Professor of Mathematical Biology at Oxford University and Co-Director at the Oxford Martin Programme on Collective Responsibility for Infectious Disease, has compiled the evidence on health risks from low-level ionizing radiation, in order to better inform policy decisions and show where crucial gaps in knowledge lie. 

Published today in the Proceedings of the Royal Society, the restatement clarifies the scientific evidence available from a variety of sources, and ranks them as to how much they enjoy consensus support from the scientific community.  

Professor McLean said: “We know a great deal about the health risks from radiation thanks to exceptionally careful studies of groups of people exposed to different levels from nuclear bombs or accidents, medical exposure of patients, naturally occurring sources (such as radon), and workers in the nuclear industry and medicine. From these studies, it is clear that moderate and high doses of radiation increase the risk of developing some types of cancer.” 

To illustrate the size of this increase in risk, if 100 individuals were each briefly exposed to 100 mSv (millisievert is the measure of radiation dose), then, on average over a lifetime, one of them would be expected to develop a radiation-induced cancer, whereas 42 of them would be expected to develop cancer from other causes.   To put 100 mSv in context, the low dose from a CT scan of the whole spine is 10 mSv, while the average dose from natural background radiation in the UK is 2.3 mSv each year.

“Despite the depth of our knowledge, there are still many unknowns.” said Professor McLean.  “Even the best designed epidemiological study finds it hard to distinguish between no extra risk and a small additional risk at low levels of exposure and we have to make some important assumptions here, particularly for the purposes of radiation protection.  For example, no human study has conclusively shown an increase in hereditary disease in the children of irradiated parents, but radiation protection calculations assume some risk is present because of evidence from large animal experiments.”

“There is also a great deal of work being undertaken to investigate the biological basis of the damage from radiation to DNA and cells, but it is still not clear precisely the steps by which a dose of radiation might lead to cancer, sometimes decades later”.

The authors conclude by pointing out that the overall risk to human health from low-level radiation exposure is small, particularly when compared with the risks posed by modern life such as obesity, smoking and air pollution.

The full paper, “A restatement of the natural science evidence base concerning the health effects of low-level ionizing radiation” can be downloaded at www.oxfordmartin.ox.ac.uk/policy/restatements/.

Oxford Martin Restatements review the natural science evidence base underlying areas of current policy concern and controversy. Written in policy neutral terms and designed to be read by an informed but not technically specialist audience, restatements are produced by a writing team reflecting the breadth of opinion on the topic in the science community and involve wide consultation with interested stakeholders. The final version of the restatement is peer-reviewed prior to publication.