INTRODUCTION: The association between exposure to extremely low-frequency electric and magnetic fields (ELF) and childhood leukemia has led to the classification of magnetic fields by the International Agency for Research on Cancer as a "possible human carcinogen." This association is regarded as the critical effect in risk assessment. Creating effective policy in light of widespread exposure and the undisputed value of safe, reliable, and economic electricity to society is difficult and requires estimates of the potential public health impact and associated uncertainties.
OBJECTIVES: Although a causal relationship between magnetic fields and childhood leukemia has not been established, we present estimates of the possible pubic health impact using attributable fractions to provide a potentially useful input into policy analysis under different scenarios.
METHODS: Using ELF exposure distributions from various countries and dose-response functions from two pooled analyses, we calculate country-specific and worldwide estimates of attributable fractions (AFs) and attributable cases.
RESULTS: Even given a wide range of assumptions, we find that the AF remains < 10%, with point estimates ranging from < 1% to about 4%. For small countries with low exposure, the number of attributable cases is less than one extra case per year. Worldwide the range is from 100 to 2,400 cases possibly attributable to ELF exposure.
CONCLUSION: The fraction of childhood leukemia cases possibly attributable to ELF exposure across the globe appears to be small. There remain, however, a number of uncertainties in these AF estimates, particularly in the exposure distributions.
KEY WORDS: attributable fraction, ELF, extremely low-frequency electromagnetic fields, health impact, health policy. Environ Health Perspect 114:1532-1537 (2006). doi:10.1289/ehp.8977 available via http://dx.doi.org/ [Online 22 June 2006]
There has been considerable scientific research to understand the potential link between residential and occupational exposures to power-frequency electric and magnetic fields (ELF) and the occurrence of cancer and other diseases. The "limited" association between childhood leukemia and ELF found in epidemiologic studies (evidence from epidemiologic studies is a major force in driving ELF risk assessments), along with "inadequate" animal data, has led to the classification of magnetic fields by the International Agency for Research on Cancer (IARC) as a "possible human carcinogen" (IARC 2002). Because childhood leukemia is the outcome for which the scientific evidence is strongest, it can be regarded as the critical effect in risk assessment and risk evaluation.
The combination of the association of childhood leukemia with low-level, chronic exposures on the one hand and the widespread exposures to ELF on the other have made it both necessary and difficult to develop consistent public health policies on ELF exposure. The need for such policies results from the undisputed value of safe, reliable, and economic electricity to society to maintain all the benefits that this provides. Creating effective policy in light of these critical considerations requires an estimate of the potential public health impact and associated uncertainties.
The attributable fraction (AF) can be used to inform policies on ELF exposure. The AF, based on an established exposure-disease relationship, is the proportion of the caseload (of disease) that is attributable to the exposure, assuming there is a causal relationship. Hence, the AF can be used to estimate the degree of incidence reduction that would be expected if the observed association were real and if exposure were reduced. In this article we begin with a description of what is known about ELF exposure distributions in various countries. Then, we calculate country-specific and worldwide estimates of AF and …