Cancer in children of nuclear industry employees: report on children aged under 25 years from nuclear industry family study.

OBJECTIVE To determine whether children of men and women occupationally exposed to ionising radiation are at increased risk of developing leukaemia or other cancers before their 25th birthday. DESIGN Cohort study of children of nuclear industry employees. SETTING Nuclear establishments operated by the Atomic Energy Authority, Atomic Weapons Establishment, and British Nuclear Fuels. SUBJECTS 39 557 children of male employees and 8883 children of female employees. MAIN OUTCOME MEASURES Cancer incidence in offspring reported by parents. Employment and radiation monitoring data (including annual external dose) supplied by the nuclear authorities. RESULTS 111 cancers were reported, of which 28 were leukaemia. The estimated standardised incidence ratios for children of male and female employees who were born in 1965 or later were 98 (95% confidence interval 73 to 129) and 96 (50 to 168) for all malignancies and 109 (61 to 180) and 95 (20 to 277) for leukaemia. The leukaemia rate in children whose fathers had accumulated a preconceptual dose of >/=100 mSv was 5.8 times that in children conceived before their fathers' employment in the nuclear industry (95% confidence interval 1.3 to 24.8) but this was based on only three exposed cases. Two of these cases were included in the west Cumbrian ("Gardner") case-control study. No significant trends were found between increasing dose and leukaemia. CONCLUSIONS Cancer in young people is rare, and our results are based on small numbers of events. Overall, the findings suggest that the incidence of cancer and leukaemia among children of nuclear industry employees is similar to that in the general population. The possibility that exposure of fathers to relatively high doses of ionising radiation before their child's conception might be related to an increased risk of leukaemia in their offspring could not be disproved, but this result was based on only three cases, two of which have been previously reported. High conceptual doses are rare, and even if the occupational association were causal, the number of leukaemias involved would be small; in this study of over 46 000 children, fewer than three leukaemias could potentially be attributed to such an exposure.