Childhood cancer and paternal exposure to ionizing radiation: preliminary findings from the Oxford Survey of Childhood Cancers.

Paternal occupational data already collected as part of the Oxford Survey of Childhood Cancers have been reviewed. Information on occupations during or before the relevant pregnancy was sought for 15,279 children dying from cancer in England, Wales, and Scotland in the period 1953-81, and for an equal number of matched controls. Estimates were made for paternal exposure to human-made external ionizing radiation in the six months before conception of the survey child--as judged from job histories and dates of birth. Assessments were also made for potential exposure to unsealed sources of radionuclides. Of the eight fathers placed in the highest dose group (> or = 10 mSv, external radiation), four were cases and four were controls. For the second dose group (5-9 mSv), the corresponding numbers were eight and four, and for the lowest exposed group (1-4 mSv), they were 55 and 42. There were 27 case fathers with potential exposure to radionuclides and only 10 control fathers. The independent effects of the two radiation variables were assessed by means of multiple logistic regression. Relative risks for estimated doses of external radiation were close to unity, but for radionuclide exposure the relative risk was 2.87 (95% CI = 1.15-7.13). These preliminary findings suggest that paternal exposure to radionuclides is a more likely risk factor for childhood cancer than exposure to external radiation.