EMF & CANCER: EPIDEMIOLOGIC EVIDENCE TO DATE Dr Leeka I Kheifets World Health Organization Tel: +41 22 791 49 76, Fax: +41 22 791 4 1 23, Email: kheifetsl@who.int ?? Abstract The results of many years of epidemiologic studies concentrating on the possible health risks (particularly cancer risks) associated with exposure to electric and magnetic fields (EMF) have been equivocal. While some studies suggest that EMF could pose a health risk, the risk estimates are low, and their confidence intervals often include no effect. However, if real, even a small risk of a prevalent exposure could have major public health implications. In June 2001, an expert scientific working group of IARC reviewed studies related to the carcinogenicity of static and ELF electric and magnetic fields. Using the standard IARC classification that weighs human, animal and laboratory evidence, ELF magnetic fields were classified as possibly carcinogenic to humans based on epidemiological studies of childhood leukaemia. Evidence for all other cancers in children and adults, as well as other types of exposures (i.e. static fields and ELF electric fields) was considered not classifiable either due to insufficient or inconsistent scientific information. Although there have been more than 200 epidemiologic studies in this area, many early studies of EMF were too limited in design and scope to do more than generate hypotheses. The number of epidemiologic studies with the methodologic wherewithal to test hypotheses is growing. Among the improvements in this new generation of studies are: a priori specification of hypotheses-- to better distinguish between chance occurrence and real association; examination of specific cancers, which should allow for the identification of agents specific to the etiology of a particular cancer; larger numbers of subjects to improve the precision of risk estimates; improved exposure assessment to reduce misclassification of exposure; and evaluation of a variety of potential confounders to minimize the possibility of a spurious association. Unfortunately, the improvements in study quality have not led to a concomitant improvement in the clarity of our picture of the relationship between EMF and cancer risk. The discussion will include comments on what we have learned and why studying EMF exposure poses unique and substantial difficulties. ?? Introduction Electricity use has grown throughout the industrialized world since the first public power station began operation in London on 12 January 1882. Electricity is generated and usually transmitted as alternating current (ac) in North America at 60 or 60 Hertz (Hz) cycles per second. In the past, exposures to ambient EMF have been thought to be without biologic effects. The first suggestion that exposures might be detrimental to one’ s health arose from Soviet Union studies in the early 1960's (5). Since 1979 when epidemiological studies first raised a concern about exposures to power line frequency magnetic fields and childhood leukaemia, a large number of studies have been conducted to determine if measured ELF exposure can influence cancer development, especially in children. Concern also continues about exposure to radiofrequency (RF) fields from sources used for mobile telecommunications, radars, radio and television broadcast, medical and industrial applications. Much of this concern arises because new technologies are introduced without provision of public information about their nature or discussion of the debate within the scientific community about possible health consequences. In the meantime, mobile phone use has increased dramatically with falling costs. Industry sources suggest that there will be over one billion users worldwide by 2005, far exceeding telephone use via fixed- lines. Of particular concern to WHO is the fact that, if any adverse health effect is established from mobile phone use or use of electricity, it will be a global concern because developing countries are establishing this technology in preference to the more-expensive fixed line systems and the use of electricity is ubiquitous. Thus even a small impact on health could have a major public health consequence. The health effects that have received the most attention are cancer, reproductive effects and neurobehavioral effects. The evidence linking cancer to EMF exposure is discussed below ?? Long-term health effects of ELF ELF fields are known to interact with tissues by inducing electric fields and currents in them. This is the only established mechanism of action of these fields. However, the electric currents induced by ELF fields commonly found in our environment are normally much lower than the strongest electric currents naturally occurring in the body such as those that control the beating of the heart. There is no convincing evidence that exposure to ELF fields below currently accepted international exposure limits causes direct damage to biological molecules, including DNA. Since it seems unlikely that ELF fields