Aggregating Disparate Epidemiological Evidence: Comparing Two Seminal EMF Reviews

Abstract

Two seminal reviews (IARC, 2002; CDHS, 2002) of possible health effects from power-frequency EMFs reached partly different conclusions from similar epidemiological evidence. These differences have an impact on precautionary policy. We examine the statistical aggregation of results from individual disparate studies. Without consistent exposure metrics, the advantage of meta-analysis to estimate magnitude of effect is lost. However, counting positive and statistically significant results yields important information. This is not a substitute for meta-analysis, but a fall-back when meaningful meta-analysis is not available. Representative results from 33 independent adult leukemia studies tabled by IARC yielded 23.5 positives (p approximately 0.01) and 9 significant-positives (p<10(-7)). From 43 representative results from CDHS, there were 32 positive (p<0.001) and 14 significant-positives (p<10(-12)). There were no significant-negative results in either list. Results for adult brain cancer gave a similar, but less clear, message. Childhood leukemia EMF studies have been sufficiently comparable to allow selective pooled analysis, which was important in classifying carcinogenicity. Aggregating all the studies suggests that results for childhood leukemia are not stronger, numerically, than those for adult leukemia. CDHS did not note the number of significant-positives, but noted the meta-analytic summary and the number of positives, forming a view about the strength of these findings. IARC shows no evidence of considering the aggregation of results other than subjectively. It considered individual studies but this led to a tendency to fragment and dismiss evidence that is intrinsically highly significant. We make recommendations for future reviews.

Effect of 2.45 mT sinusoidal 50 Hz magnetic field onSaccharomyces cerevisiaestrains deficient in DNA strand breaks repair

“…The findings of the California Department of Health Services (CDHS) in its 2002 report conclude that EMF can cause some degree of increased risk of childhood leukaemia and adult brain cancer but, in contrast, they also affirm that EMF do not increase the risk of birth defects, breast cancer, heart disease, Alzheimer's disease or depression (Neutra et al 2002). Recently, a comparison between two seminal reviews, from the International Agency for Research of Cancer (IARC) and CDHS, about possible health effects of EMF has been reported reaching partly different conclusions from a similar epidemiological study (O'Carroll and Henshaw 2008). These authors found that there was indeed evidence of association between MF exposure and increased risk of adult leukaemia and adult brain cancer, but the appropriate analysis was not carried out in the IARC Report.…”

Magnetosensory function in rats: Localization using positron emission tomography

“…Electromagnetic fields (EMFs) emanating from man-made electrical devices, such as mobile phones, powerlines, and radar, are ubiquitous in the environment. Associations have been reported between brain cancer and chronic exposure to environmental EMFs (Berg et al, 2006;Villeneuve et al, 2002), but there is no agreement on the scope and extent of the risk to public health (O'Carroll and Henshaw, 2008).…”

Effects of exposure to extremely low frequency magnetic fields on spermatogenesis in adult rats

“…Worldwide concerns about the potential health risks of ELF‐MF have provoked increasing scientific interest and become an issue of great public debate. Many studies have reported an association between ELF‐MF exposure and human health, with emphasis on a variety of clinical diseases, including: brain tumors, colon cancer, breast cancer, acute childhood leukemia, genotoxicity, neurodegenerative diseases, infertility, birth defects, increased risk of miscarriage, and others [Ahlbom et al, ; Kundi et al, ; Garcia et al, ; Kheifets et al, ; O'Carroll and Henshaw, ; Davanipour and Sobel, ; Huss et al, ; Gharagozloo and Aitken, ]. Because of the high sensitivity of male reproductive organs to environmental hazards and the problems of declining sperm quality and infertility, considerable attention has been focused on the potential risk of ELF‐MF to male reproduction.…”