A case-control study of childhood leukemia in Southern Ontario, Canada, and exposure to magnetic fields in residences

Abstract

A population-based case-control study was conducted in Ontario, Canada, to assess the relation between the risk of childhood leukemia and residential exposure to magnetic fields. Participating subjects consisted of 201 cases, diagnosed at 0 to 14 years of age during 1985-1993, ascertained from the records at the Hospital for Sick Children (Toronto), and 406 individually matched controls. Where possible, point-in-time measurements of magnetic fields were made in all residences occupied by subjects during the period of inquiry in the defined catchment area. Three different classification schemes of wire code were assigned to each residence. Detailed information was collected by interviewer-administered questionnaires, which enabled risk estimates to be adjusted for socio-economic characteristics, medical history of parent(s) and child and environmental exposures. Inconsistent elevations in risk were associated with time-weighted averages of magnetic fields both inside and outside the home for subjects having residential point-in-time measurements that represented at least 70% of their etiological period. These risks increased in magnitude when analysis was restricted to children under 6 years of age at diagnosis or to those with acute lymphoblastic leukemia. For children younger than 6 years at diagnosis, outside perimeter measurements of the residence, H0.15 T, were associated with increased leukemia risk (OR ‫؍‬ 3.45, 95% CI ‫؍‬ 1.14-10.45). Evaluation of different exposure times for point-in-time magnetic field measurements and wire configuration suggested that exposures earliest in the etiological period were associated with greater risks for children diagnosed at a younger age (OR ‫؍‬ 2.50, 95% CI ‫؍‬ 1.14-5.49). Our findings did not support an association between leukemia and proximity to power lines with high current configuration. Int. J. Cancer 82:161-170, 1999. Wiley-Liss, Inc.The known causes of leukemia in children are relatively few, and their contribution to the current incidence of this malignancy is thought to be small. Although rare, leukemia is the most common cancer in children and is regarded by some as increasing in incidence (Schmidt, 1998;Desch and Bleyer, 1994). Within the last 2 decades, the role of electric and magnetic field (EMF) exposure has increasingly become a part of the body of research examining the etiology of this childhood cancer. The first suggestion that EMFs from power lines might cause cancer in children was made by Wertheimer and Leeper (1979). Extensive research since then has not resolved the question of whether EMFs increase the risk of cancer. While not all studies have shown increased risk estimates, there has been some consistency of positive findings relating to studies of children, specifically those with leukemia, and EMF exposure as defined by wiring of high current configuration. Wire configuration is an indirect measure of personal exposure; therefore, the extent to which it is an accurate index of exposure, particularly long-term exposure, remains unknown. Mo...

Multiple-Bias Modelling for Analysis of Observational Data

“…Two other recent studies were excluded. Green et al (1999) presented only analyses based on quartile categories, resulting in upper cut points of only 1.3–1.5 mG. This study was excluded because the use of such low cut points strongly influenced estimates from earlier studies (Greenland, Sheppard, Kaune, Poole and Kelsh, 2000); it did, however, report positive associations on contrasting the top and bottom quartiles.…”

Review of the epidemiologic literature on EMF and Health.

“…Initial studies characterized field levels using short-term, or "spot," measurements taken immediately outside (23) or within residences (12), the latter obtained in the child's and parents' bedrooms. Subsequently, 24-hr measurements were obtained in rooms in which subjects spent a substantial proportion of time, based on interview data (9,15,19,21,(33)(34)(35)(36)(37). Such measurements are made after diagnosis, but unlike measurements based only on power lines, these inhome measurements reflect all sources of magnetic fields in the residence (38).…”

“…In residential studies assessing exposure using spot and/or 24-hr or longer area magnetic field measurements, increases in leukemia, ranging from 1.3-to 1.5-fold elevated, were reported for children with average magnetic field exposures ≥0. (34,79), and an odds ratio of 1.1 (95% CI = 0.31-4.06) was linked with point-in-time measurements ≥0.13 µT taken in the child's bedroom in a study in southern Ontario, Canada (based on 21 cases) ( Table 1) (36). The latest study is from Germany and showed a relative risk of 1.6 (0.7-3.7) for 0.2 µT and 3.2 (1.3-7.8) for nighttime exposure (80).…”

Magnetic Field of Electrical Radiant Heating System

“…According to [3], increased risk starts at level several hundred times lower than the reference level. Studies reported in [4] indicate that increased risk starts as low as 0.4 µT or even lower. According to [5], [6], the average level of magnetic flux density ranges from 0.025 μT to 0.07 μT at homes and typically is ten times higher at workplaces.…”