Nuclear study finds link to heart disease

Wednesday, March 5, 2008

By Clive Cookson, Science Editor

A big study of nuclear workers has suggested an unexpectedly strong link between radiation exposure and heart disease.

The study, published yesterday, analysed health records and radiation doses for 65,000 people employed at four nuclear sites - Sellafield, Capenhurst and Springfields, in north-west England, and Chaplecross in south-west Scotland - between 1946 and 2005.

Scientists from Westlakes Consulting, a non-profit research organisation in Cumbria, found a strong statistical association between increasing radiation and diseases of the heart and circulation, stronger than the better known link between occupational exposure and cancer. The probability of the association being coincidental was less than one in a thousand, said Steve Jones, the project leader. But he urged caution in interpreting the results, which are published online by the International Journal of Epidemiology.

Prof Jones said: "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."

Michael Gillies, a Westlakes statistician, said further research would be necessary to determine whether radiation exposure directly caused the circulatory disease in nuclear workers or whether other factors associated, for example, with diet, exercise, socio-economic status, shift working and stress, might have been responsible. The study design might not have been able to control fully for unexpected variations in such factors.

Even if the relationship between occupational radiation exposure and cardiovascular disease is genuine, the effect on average life expectancy is quite small. Prof Jones said that for someone who worked in the nuclear industry during its first three decades, when permitted radiation doses were much higher than today, it would cut the chance of living beyond the age of 70 from about 75 per cent to 73 per cent. The number of premature deaths from cardiovascular disease caused by radiation might be four or five per year.

Workers at the sites have lower average mortality than the local population as a whole. Prospect, the trade union, said the study "raised more questions than it answered" and called for further research.

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