A comparison of the risks of leukaemia in the offspring of the Sellafield workforce born in Seascale and those born elsewhere in West Cumbria with the risks in the offspring of the Ontario and Scottish workforces and the Japanese bomb survivors

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Abstract
The cases of childhood leukaemia found among children of the Sellafield (West Cumbria), Ontario and Scottish radiation workers and in the offspring of the Japanese bomb survivors are analysed using linear and exponential forms of a relative risk model with total preconception external radiation dose estimates. In particular, the risks among children of the Sellafield workforce born in Seascale and among those born elsewhere in West Cumbria are compared with the risks derived from the other datasets. There is a highly significant inconsistency between the raised paternal preconception exposure excess relative risk coefficients for leukaemia in those children of the Sellafield workforce born in Seascale and the coefficients for children born elsewhere in West Cumbria, those for the offspring of the Ontario or Scottish workforces as well as those for the offspring of the Japanese bomb survivors. These incompatibilities are independent of the models used. In contrast to this, the leukaemia excess relative risk coefficients for paternal preconception exposure of those children of the Sellafield workforce born elsewhere in West Cumbria are not significantly elevated and do not differ significantly from those observed in the Japanese, Ontario and Scottish datasets. The possibility that some risk factor effectively confined to Seascale might be interacting synergistically with paternal preconception radiation exposure to account for the extraordinary discrepancy (by more than two orders of magnitude) between the leukaemia risks in the Seascale-born children and those born elsewhere in West Cumbria is examined. It is shown that such an interaction would imply implausibly high supra-multiplicativity. The association between leukaemia and paternal preconception dose reported by Gardner and colleagues (1990a) is most likely to have been a chance finding, with a possible small involvement of confounding in Seascale.