Paternal Exposure to Ionizing Radiation in Ontario Uranium Miners and Risk of Congenital Anomaly in Offspring: A Record-Linkage Case-Control Study Principal investigator(s): Loraine Marrett (Cancer Care Ontario) Co-investigator(s): John McLaughlin (Samuel Lunenfeld Research Institute); Douglas Chambers (SENES Consultants Ltd.) Sponsoring Institution: Cancer Care Ontario Objective To determine if pre-conceptional exposure to ionizing radiation as a uranium miner increases the risk of congenital anomalies in offspring. Method A population-based matched case-control study was employed. Cases: Ontario infants with congenital anomalies from the Canadian Congenital Anomalies Surveillance System, 1979-1986. Controls: normal live born infants selected from Ontario Birth Certificates over the same period (case-control file [CCF]). The CCF was linked to uranium miners in the Mining Master File (MMF) or the National Dose Registry (NDR), 1952-1986, to identify cases and controls whose fathers were miners prior to their conception. Results There were 28,992 uranium miners in the combined MMF-NDR file, and 42,446 case-control pairs. Linkage of CCF and MMF-NDR produced 449 links. Overall, there was no increased risk of having a child with a congenital anomaly if the father was a uranium miner or exposed to radon before the conception. There was no increased risk of having any specific anomaly or any category of anomaly according to ICD-9 categorical or hierarchical etiological groupings. Risk has not yet been examined in relation to dose of gamma radiation exposure, or in relation to radiation exposure during specific windows of time pre-conception. Conclusions Preliminary results suggest that the children of Ontario uranium miners do not have increased risk of having congenital anomalies. For more information: loraine.marrett@utoronto.ca