IARC Classification of Static and Extremely Low Frequency Electric andMagnetic Fields (Volume 80 of the IARC Monographs Series)

Abstract

A working group of 21 scientific experts from 10 countries met in Lyonfrom 18-26 June 2001 to evaluate possible carcinogenic hazards to humanbeings from exposures to static and extremely low frequency (ELF)electric and magnetic fields. This volume is the first in a plannedseries of two volumes of IARC Monographs on various kinds ofnon-ionising radiation in the frequency range below that of visiblelight. ELF magnetic field exposures result from proximity to electric powertransmission lines, household wiring and electric appliances, and are inaddition to the exposure that results from the Earth's magnetic field.Magnetic fields are measured in units of microtesla; the Earth's staticmagnetic field varies from 25 microtesla at the equator to 65 microteslaat the poles. Since the first report, suggesting an association between residentialelectric and magnetic fields and childhood cancer, notably leukaemia,was published in 1979, dozens of studies have examined this association.Overall, for the vast majority of children who are exposed toresidential ELF magnetic fields less than 0.4 microtesla, there islittle evidence of any increased risk for leukaemia. There is noevidence that electric fields are associated with childhood leukaemia,and there is no consistent relationship between childhood brain tumoursor other childhood solid tumours and residential ELF electric andmagnetic fields. However, pooled analyses of data from a number ofwell-conducted studies show a fairly consistent statistical associationbetween childhood leukaemia and power-frequency residential magneticfield strengths above 0.4 microtesla, with an approximately two-foldincrease in risk. This is unlikely to be due to chance, but may beaffected by selection bias. Therefore this association between childhoodleukemia and high residential magnetic field strengths was judged limited evidence for excess cancer risk in exposed humans. There is no consistent evidence that residential or occupationalexposures of adults are related to excess risks of cancer at any site,although in one Swedish study combined residential and occupationalexposures were associated with a significantly increased risk for allleukaemia subtypes except chronic lymphocytic leukaemia. Evidence forexcess cancer risks of all other kinds, in children and in adults, as aresult of exposure to ELF electric and magnetic fields was considered inadequate. Numerous studies to investigate carcinogenicity of magnetic fields havebeen conducted in experimental animals. These have included long-termbioassays of exposures to magnetic fields alone, and exposures of ratsand mice to magnetic fields in combination with known carcinogens.Bioassays of magnetic fields alone generally were negative, although onestudy that was conducted in both mice and rats of both sexes showednon-exposure related increases in thyroid C-cell tumours in male ratsonly. Multistage carcinogenesis studies showed no consistent enhancementof chemically initiated mammary tumours in rats or of skin tumours inmice. Magnetic fields had no effects on the incidence of chemicallyinitiated liver tumours in rats or of leukaemia/lymphoma in mice orrats. Overall, evidence for carcinogenicity of ELF magnetic fields inexperimental animals was judged inadequate. No data oncarcinogenicity to animals of static magnetic fields, or of static orELF electric fields, were available to the working group. Although many hypotheses have been put forward to explain possiblecarcinogenic effects of ELF electric or magnetic fields, no scientificexplanation for carcinogenicity of these fields has been established. Overall, extremely low frequency magnetic fields were evaluated as possibly carcinogenic to humans (Group 2B), based on the statisticalassociation of higher level residential ELF magnetic fields andincreased risk for childhood leukaemia. Static magnetic fields andstatic and extremely low frequency electric fields could not beclassified as to carcinogenicity to humans (Group 3).