Washington, March 10 : A study involving a large number of workers employed in the UK nuclear industry, conducted to see whether occupational or medical exposure to ionising radiation may increase death rate from diseases other than cancer, suggests that socio-economic status of workers has a greater influence on mortality than the quantum of radiation exposure.
The researchers involved 64,937 individuals employed at the study sites between 1946 and 2002, and followed them up to 2005.
Radiation exposures, as measured by personal dosimeters ('film badges'), were available for 42,426 individuals classified as 'radiation workers'.
Poisson regression models were used to investigate the relationship between excess mortality rates and cumulative radiation exposure, using both relative and additive risk models.
Based on their observations, the authors of the study wrote that the cohort showed a pronounced 'healthy worker' effect.
They said that overall, workers' socio-economic status, as indicated by their employment status, had a greater influence on mortality than radiation exposure.
For male radiation workers, there was an apparent dose response for mortality from circulatory system disease. However, the researchers also found evidence for inhomogeneity in the apparent dose response, when they separately examined four categories of employment and radiation exposure status.
The authors concluded that they had found evidence for an association between mortality from non-cancer causes of death, particularly circulatory system disease, and external exposure to ionising radiation in the cohort.
They, however, said that the tentative nature of biological mechanisms that might explain such an effect at low chronic doses, and the above inhomogeneities in apparent dose-response, suggested that the results of their analysis were inconsistent with any simple causal interpretation.
The authors said that further research was needed to explain the inhomogeneities, and on the possible role of factors associated with socio-economic status and shift working, before any further conclusions could be drawn.