Are low levels of nuclear radiation good for you? Or merely harmless, as many nuclear advocates want you to think? Sadly not, writes Ian Fairlie. A huge new study finds ‘strong evidence’ of a dose-response relationship between cumulative, external, chronic, low-dose, exposures to radiation, and incidence of leukemia.
In 2013, I discussed several epidemiological studies providing good evidence of radiogenic risks at very low exposure levels.
A powerful new study has been published in Lancet Haematology  which adds to this evidence. However the study’s findings are more important than the previous studies, for several reasons.
First, it provides “strong evidence”, as stated by the authors, of a “dose-response relationship between cumulative, external, chronic, low-dose, exposures to radiation and leukaemia”.
Second, it finds radiogenic risks of leukemia among nuclear workers to be more than double the risk found in a previous similar study in 2005. The excess relative risk of leukaemia mortality (excluding workers exposed to neutrons) was 4.19 per Gy.
Third, it confirms risks even at very low doses (mean = 1·1 mGy per year). Unlike the Japanese bomb survivors’ study, it observes risks at low dose rates rather than extrapolating them from high levels.
Fourth, it finds risks do not depend on dose rate thus contradicting the ICRP’s use of a Dose Rate Effectiveness Factor (DREF) which acts to reduce (by half) the ICRP’s published radiation risks.
Fifth, it finds radiogenic leukemia risks decline linearly with dose, contradicting earlier studies suggesting a lower, linear-quadratic relationship for leukemia. It strengthens the Linear No Threshold (LNT) model of radiogenic risks, as it now applies to leukemias as well as solid cancers.
Sixth, the study finds no evidence of a threshold below which no effects are seen (apart from zero dose).
Seventh, the study uses 90% confidence intervals and one-sided p-values. In the past, 95% intervals and two-sided p-values were often incorrectly used which had made it harder to establish statistical significance.
The study’s credentials are pretty impeccable. It’s a huge study of over 300,000 nuclear workers adding up to over 8 million person years, thus ensuring its findings are statistically significant, ie with very low probability of occurring by chance.
Also, it’s an international study by 13 respected scientists from national health institutes in the US, UK, and France, as follows.
- Centers for Disease Control and Prevention, US
- National Institute for Occupational Safety and Health, US
- Department of Health and Human Services, US
- University of North Carolina, US
- Drexel University School of Public Health, US
- Public Health England, UK
- Institut de Radioprotection et de Sûreté Nucléaire, France
- Center for Research in Environmental Epidemiology, Spain
- UN International Agency for Research on Cancer, France
Funding was provided by many institutions, including US Centers for Disease Control and Prevention, US National Institute for Occupational Safety and Health, US Department of Energy, US Department of Health and Human Services, Japanese Ministry of Health Labour and Welfare, French Institut de Radioprotection et de Sûreté Nucléaire, and the UK’s Public Health England.