Scientists discover possible radiation and heart disease link
James Randerson, Science Correspondent, guardian.co.uk, March 04 2008
Scientists studied workers at four UK nuclear sites, including Sellafield, and discovered a potential connection between exposure to radiation and heart disease.
A study of nearly 65,000 nuclear industry workers over more than 60 years has found a possible link between high radiation exposure and heart disease.
The finding was particularly surprising since there is no established biological mechanism that would explain how radiation exposure might cause heart disease. However, the research team stressed that its analysis could not rule out other factors that could explain the link, such as work-related stress or irregular shift patterns.
The team studied 64,818 workers at the Sellafield, Springfields, Chapelcross and Capenhurst nuclear sites. Some of the workers began work in the industry as far back as 1946, and 42,426 were exposed to radiation as part of their job.
When the researchers compared workers occupationally exposed to radiation with those who were not, they did not find any difference in the number of cases of heart disease and stroke. However, when they split the radiation-exposed workers into groups with different levels of exposure (based on readings from radiation-monitoring badges worn by all staff) they did see a disparity.
Those workers who were exposed to the highest levels had a slightly lower life expectancy due to an increased probability of heart disease and strokes. "We see a higher mortality for those workers with the highest level of operation exposure," said Prof Steve Jones of Westlakes Scientific Consulting, the private company hired by British Nuclear Fuels and the Nuclear Decommissioning Authority to carry out the research.
The team stressed that because the analysis was carried out retrospectively, it could not be sure that the findings ruled out other factors that could be responsible for the results. "We can't show whether it's a consequence of that exposure or whether it's due to something else," said Jones.
However, he added that if radiation were the cause, then the workers who have experienced the highest levels of exposure have roughly a 73% chance of surviving until they are 70, compared with a 75% chance if they had received no exposure at all.
The findings will have little relevance for workers joining the industry today, according to the team. "I don't think it's a big issue for nuclear workers at present or in the future because the exposure levels are so low," said the report's co-author Michael Gillies. In the 1960s, workers were exposed to up to a radiation dose of 12 millisieverts per year compared with around one millisievert per year now.
The most highly exposed workers received a radiation dose around five to 10 times less during their entire working lives than survivors of the atomic bomb dropped on Hiroshima in 1945.
In any case, workers in the nuclear industry are generally much healthier than the general population, despite the health risks they may face at work. By comparing their sample with the average for the local population, the team found that the mortality rate of nuclear workers is 20% lower.
The team reported its findings today in the International Journal of Epidemiology.