Nuclear workers exposed to relatively high levels of radiation over long periods of service before the 1980s may be at increased risk of circulatory disease, according to a new study.
The research, conducted by Westlakes Scientific Consulting and published this week in the International Journal of Epidemiology, focused on 65,000 individuals employed between 1946 and 2002 at sites operated by British Nuclear Fuels plc and its predecessors.
Professor Steve Jones, corresponding author of the study, said the findings are important but must be interpreted with caution: ‘What we have shown is an association between relatively high levels of occupational exposure to radiation and mortality from circulatory system disease. However, we have not been able to take account of all the other possible causes of circulatory system disease. 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.’
‘We also found an overall ‘healthy worker’ effect – that is, workers had lower mortality rates than the local general population, and the overall mortality of occupationally exposed workers was no different from workers who were not exposed at all. Overall, socioeconomic status had a greater influence on mortality rate of the cohort than did radiation exposure status.’
The team at Westlakes analysed the relationship between non-cancer mortality rates and cumulative radiation exposure (measured by dosimeter badges worn by the workers). They found evidence for an association between mortality from non-cancer causes of death, particularly circulatory system disease, and external exposure to ionising radiation. Workers with the highest levels of occupational exposure – which occurred before the 1980s – had an increased risk of dying from circulatory disease compared to those with the lowest levels of exposure. Currently, average occupational exposures at the sites studied are comparable to, or less than, exposures from natural background radiation.
Michael Gillies, a statistician from the study team, explained that further research is necessary to determine whether radiation exposure is directly responsible for the increases in circulatory disease observed: ‘Other factors associated, for example, with diet, exercise, socioeconomic status, shift working and stress, may be responsible. Many studies associate these factors with an increased risk of circulatory disease, and this is clearly something that requires more detailed investigation.’