Childhood leukaemia and exposure to electric and magnetic fields

grantor: University of TorontoA population-based case control study was conducted in southern Ontario to assess the relationship between paediatric leukaemia and a number of environmental factors, of which exposure to electric and magnetic fields (EMF) was of primary interest. Children diagnosed with leukaemia during the period 1985-1993 who were less than 15 of age at the time of diagnosis were ascertained from the records of the Hospital for Sick Children (Toronto). Controls were randomly selected from a data base created using teledirect marketing lists applicable to the defined study catchment area and were individually matched to the cases on year of birth and sex. A total of 201 cases and 406 controls were identified. Information relating to demographic and potential risk factors for leukaemia was collected through detailed personal interviews. For current and previous residences occupied by the child within the catchment area during the defined period of inquiry, point-in-time measurements of magnetic fields both inside and outside the home were made. Residences were categorized according to three different wire code classifications. If the residence in which the child was living at the time of interview was relevant to the period of inquiry, the child wore a personal monitor for approximately 48 hours. The findings reported in this thesis are based on the subset of 338 children (108 cases and 230 controls) with EMF measurements derived from personal monitoring. The child's residence accounted for almost 80% of the total average exposure for most children. There was evidence of an association between exposure to magnetic fields measured by monitoring the child's usual activities at home and increased risk of developing leukaemia. The risk was more pronounced for children who were diagnosed at less than six years of age and those children with acute lymphoblastic leukaemia. After adjustment for potential confounders, residential magnetic field exposures of 0.18[mu]T or more were associated with an odds ratio of 4.79 (95% confidence interval 1.66-13.88). When magnetic field exposures in the home were corrected for power consumption, the resulting odds ratios for all exposure levels above the referent (exposures of 0.04[mu]T or greater) were significantly elevated. Point-in-time measurements of magnetic fields within the child's residence (child's bedroom and two other rooms frequently occupied by the child) were associated with elevated but non-significant odds ratios. No relationship was observed with electric fields as measured by personal monitoring nor with wire configuration.Ph.D