Childhood leukaemia and exposure to ELF-FM fields: using epidemiological studies in guiding standard setting

Evidence for harmful effects of ELF-EM fields below current standards, comes chiefly from epidemiological studies of childhood leukaemia and magnetic fields in the home. The pooled analyses of many of their data led the International Agency for Research on Cancer (IARC) to classify ELF-EM fields as 'possibly carcinogenic to humans', the next level up from 'unclassifiable'. This classification is based on 'limited' evidence in humans and 'less than sufficient' evidence of carcinogenicity in experimental animals. The main rationale for the indecisive classification was the lack of a plausible mechanism of action, but there are many examples from the past where epidemiological evidence has preceded evidence of mechanisms. Since the IARC report, there have been some more large epidemiological studies that have produced results consistent with those from the pooled analyses. Combining results from these more recent studies into a combined estimate, still gave an estimated relative risk of 1.7 (95% C11.3-2.2) for exposure above 0.3 .T. More rigorous studies such as TransExpo are planned, but there still does not appear to be any new convincing evidence as to possible mechanisms for the increased risks. Assignment of causality between EMF and childhood leukaemia is still therefore not possible. Because of the consistency of the epidemiological findings, regulators must monitor new evidence as it arises and can only adopt a 'precautionary' approach in setting limits.