Objectives 

To test the « Gardner hypothesis » that childhood leukaemia and non-Hodgkin lymphoma can be caused by fathers'exposure to ionising radiation before the conception of the child, and, more generally, to investigate whether such radiation exposure of either parent is a cause of childhood cancer.

Design 

Case-control study.

Setting 

Great Britain.

Subjects 

35 949 children diagnosed as having cancer, together with matched controls.

Main outcome measures 

Parental employment as radiation worker as defined by inclusion in the National Registry for Radiation Workers and being monitored for external radiation before conception of child ; cumulative dose of external ionising radiation for various periods of employment before conception ; dose during pregnancy.

Results 

After cases studied by Gardner and colleagues were excluded, fathers of children with leukaemia or non-Hodgkin lymphoma were significantly more likely than fathers of controls to have been radiation workers (relative risk 1.77,95% confidence interval 1.05 to 3.03) but there was no dose-response relation for any of the exposure periods studied ; indeed, the association was greatest for those with doses below the level of detection.

No increased risk was found for fathers with a lifetime preconception dose of 100 mSv or more, or with a dose in the 6 months before conception of 10 mSv or more.

There was no increased risk for the group of other childhood cancers. (...)