UK study links radiation dose and circulatory disease

Wednesday, 5 March 2008

A study of UK nuclear industry workers has found that exposure to relatively high occupational levels of radiation over long periods of time may be linked to increased risk of circulatory disease, although radiation exposure itself may not be directly responsible for the increase.

The study of 65,000 people employed between 1946 and 2002 at sites operated by British Nuclear Fuels and its predecessors was carried out by Westlakes Scientific Consulting, and the peer-reviewed findings published in the International Journal of Epidemiology. Corresponding author Steve Jones described the findings as important but to be interpreted with caution. Although the study had shown an association between relatively high levels of occupational exposure and mortality from circulatory system disease, it had not been able to take all the other possible causes of circulatory system disease into account. He added, "The possible biological mechanisms that might explain a link with radiation are tentative at best, and so the results of our analysis are not consistent with any simple causal interpretation."

The study also found an overall "healthy worker" effect, whereby workers had lower mortality rates than the local general population. According to Professor Jones, socioeconomic status had a greater overall influence on mortality rate than did radiation risk.

Workers with the highest levels of occupational exposure, which occurred before the 1980s, were found to have an increased risk of dying from circulatory disease compared to the workers with the lowest levels of exposure, although the increase in risk was very slight. Even the most highly exposed workers would have an estimated 73% chance of surviving to and beyond the age of 70; compared to 75% for the general population. Currently, radiation exposures at the sites studied are comparable to or less than that from natural background radiation.

Other factors?

Although acute exposure to very high levels of radiation in a short time – for example in atomic bomb survivors – has been biologically linked to circulatory disease, the report's authors point out that there is no convincing evidence for a link between circulatory disease and occupational radiation doses which are much lower and take place over a long timescale. Factors such as diet, exercise, socioeconomic status, shift working and stress, rather than a direct biological effect from radiation exposure, could be responsible for the observed circulatory increases, say the researchers. Said Michael Gillies of the research team, "Many studies associate these factors with an increased risk of circulatory disease, and this is something that clearly requires more detailed investigation."

The study was originally commissioned by BNFL and funded by British Nuclear Fuels and the Nuclear Decommissioning Authority.

 

[see: International Journal of Epidemiology report on study].