HYPOTHESIS - THE RISK OF CHILDHOOD LEUKEMIA IS RELATED TO COMBINATIONS OF POWER-FREQUENCY AND STATIC MAGNETIC-FIELDS

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-freq uency (ELF) magnetic fields. Laboratory data from calcium efflux and d iatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of t he static field magnitude with a bandwidth of 9.1 mu T that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and chil dhood leukemia using data from a case-control study in Los Angeles Cou nty. ELF and static magnetic fields were measured in the bedrooms of 1 24 cases determined from a tumor registry and 99 controls drawn from f riends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicte d bands of biological activity centered at 38.0 mu T and 50.6 mu T. Al though no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of l eukemia risk with measured ELF fields was found for subjects within th ese static field bands (P for trend = 0.041). The odds ratio (PR) was 3.3 [95% confidence interval (CI) = 0.4-30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 mu T (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 mu T). When the 60 Hz magneti c fields were assessed according to the Wertheimer-Leeper code for wir ing configurations, leukemia risks were again greater with the hypothe sized exposure conditions (OR = 9.2 for very high current configuratio ns within the static field bands; 95% CI = 1.3-64.6). Although the ris k estimates are based on limited magnetic field measurements for a sma ll number of subjects, these findings suggest that the risk of childho od leukemia may be related to the combined effects of the static and E LF magnetic fields. Further tests of the hypothesis are proposed. (C) 1995 Wiley-Liss, Inc.