THE SEX-RATIO OF CHILDREN IN RELATION TO PATERNAL PRECONCEPTIONAL RADIATION-DOSE - A STUDY IN CUMBRIA, NORTHERN ENGLAND

Study objective - To investigate whether the occupational exposure to external ionising radiation of men employed at the Sellafield nuclear installation, West Cumbria, affects the sex of the children they subse quently father. Design - A retrospective cohort study using logistic r egression to analyse the sex ratio, in particular in relation to pater nal preconceptional irradiation.Setting and participants - The 260 060 singleton births between 1950 and 1989 to mothers resident in Cumbria , north west England. Results - The sex ratio among children of men em ployed at any time at Sellafield was 1.094 (95% CI: 1.060, 1.128), sig nificantly higher than that among other Cumbrian children, 1.055 (95% CI: 1.046, 1.063). There was an increased sex ratio of 1.396 (95% CI: 1.127, 1.729) in the 345 children whose fathers were estimated from an nual dose summaries to have received more than 10 mSv of external radi ation in the 90 days preceding conception, but no significant linear t rend between sex ratio and 90 day paternal preconceptional dose was fo und. There was no significant association between sex ratio and the ex ternal dose accumulated before the 90 day period preceding conception. Conclusions - Men employed at Sellafield fathered a greater proportio n of boys than would be expected for a Cumbrian population, which may be partly explained by their younger age distribution. A greater effec t was observed in the fathers with recorded doses exceeding 10 mSv in the 90 days before conception. While this may reflect a true statistic al association, it is also possible that it may be a chance finding du e to imprecision in the dose estimates and consequent misclassificatio n.