Cumulative Risk from Radiation Confirmed

We all prefer to stay in our “comfort zone” and so when I report findings based on the survivors of the nuclear attack by the US on Japan in 1945, people generally think “Oh, that is not me.” It is easy to assume that the large quick dose from an A-bomb would cause a unique harm. And it does.

However, research done by team lead by Dr David Richardson (UNC School of Public Health) shows that many small radiation exposures over time that add up to a dose equivalent to A-bomb survivor exposures show the same level of risk of cancer from the radiation. The paper, Risk of Cancer from Occupational Exposure to Ionising Radiation: Retrospective Cohort Study of Workers in France, the United Kingdom, and the United States (INWORKS) was published in October 2015 by BMJ (doi: 10.1136/bmj.h5359) and is a new classic in tackling the question of cumulative impact of radiation.

This study answers the question about whether it is “better” to get many smaller radiation exposures, as we do from natural radioactivity in our environment, from medical and dental diagnostics, from treatments, and for a growing number of people, at work. The answer: the total amount of exposure is what matters, not whether it comes all at once, or in bits and pieces.

This study did not look at females. Richardson, et al used a curated dataset composed of workers at nuclear energy sites in Europe and North America. The study group of workers was, by definition, adults. The data now spans more than 30 years and David said in conversation that females are now becoming part of the nuclear workforce. The 2015 paper looks only at males. David expects that in coming years it will become possible to ask questions about male vs females in this dataset.

Some early radiation researchers commonly spoke of risk of cancer from radiation exposure as being cumulative. I recall being a grade school pupil when my mother decided to tell me about Roentgen Equivalent Man (REM) and it was part of common knowledge in the circles she moved in that radiation exposure added up when it came to harm and risk of cancer. She suggested we make a record of all the radiation exposures I had; the visits to the dentist, the time I had a fluoroscope of my kidneys, every time I took a high-altitude flight (where there is less shielding from our atmosphere). Sadly, we did not actually make such list, though now I am somewhat glad not to have such a document. That comfort zone thing. On the other hand, that early conversation left its mark.