Study provides more precise estimates of cancer risks associated with prolonged low level radiation exposure

More precise estimates of cancer risks associated with prolonged, low level exposure to ionising radiation among nuclear industry workers are published by The BMJ today. The results suggest a linear increase in the relative rate of cancer with increasing radiation exposure and strengthen the scientific basis for current radiation protection standards.

Ionising radiation is an established cause of cancer, but information on radiation risk has come mainly from studies of people exposed to acute, high doses of ionising radiation, such as Japanese atomic bomb survivors.

Research into associations between exposure to moderate or low dose radiation and risk of cancer began in the 1950s but estimates remain uncertain.

So an international team of researchers, including Elisabeth Cardis, head of radiation program of the Center for Research in Environmental Epidemiology (CREAL), an ISGlobal Allied center, set out to investigate whether exposure to prolonged low doses of ionising radiation are associated with an increased risk of cancer.

The study involved 308,297 nuclear industry workers from France, the United Kingdom, and the United States. The workers, most of whom were men, were monitored for external radiation exposure, and were followed-up for an average of 27 years.

Risk estimates were then calculated for deaths from all cancers excluding leukemia. Factors such as age, duration of employment, and socioeconomic status were taken into account.

The estimated rate of mortality from all cancers excluding leukaemia increased with cumulative dose by 48% per gray (Gy). Similar associations were seen within each country.

Based on these estimates, the researchers suggest that about 209 of the 19,064 observed deaths due to cancer other than leukaemia were excess deaths associated with external radiation exposure.

“This study provides evidence of a linear increase in the excess relative rate of cancer mortality with increasing exposure to ionising radiation at the low dose rates typically encountered in the nuclear industries in France, the UK, and the USA,” remarks David Richardson, Associate Professor at the Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, first author of this study.

“The risk per unit dose was similar to estimates derived from studies of Japanese atomic bomb survivors, strengthening the epidemiological evidence that even low dose, low dose-rate exposures can cause a small increase in the risk of cancer”, explains Cardis. And she adds “These findings have important implications for radiation protection not only of nuclear industry workers but also of the general population and patients”.

The findings help strengthen the foundation for radiation protection standards. This study adds to a growing body of evidence suggesting associations between exposure to moderate or low dose radiation and risk of cancer.

Reference:

David B Richardson, 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 2015; 351:h5359

Picture:

Nuclear plant of Trillo, Guadalajara (Spain). Source: Sonsaz / Wikipedia. CC.