Association between Extremely Low-Frequency Electromagnetic Fields Occupations and Amyotrophic Lateral Sclerosis: A Meta-Analysis

Abstract

ObjectivesTo estimate the relationship between exposure to extremely low-frequency electromagnetic fields (ELF-EMF) and the risk of amyotrophic lateral sclerosis (ALS) by a meta-analysis.MethodsThrough searching PubMed databases (or manual searching) up to April 2012 using the following keywords: “occupational exposure”, “electromagnetic fields” and “amyotrophic lateral sclerosis” or “motor neuron disease”, seventeen studies were identified as eligible for this meta-analysis. The associations between ELF-EMF exposure and the ALS risk were estimated based on study design (case-control or cohort study), and ELF-EMF exposure level assessment (job title or job-exposure matrix). The heterogeneity across the studies was tested, as was publication bias.ResultsOccupational exposure to ELF-EMF was significantly associated with increased risk of ALS in pooled studies (RR = 1.29, 95%CI = 1.02–1.62), and case-control studies (OR = 1.39, 95%CI = 1.05–1.84), but not cohort studies (RR = 1.16, 95% CI = 0.80–1.69). In sub-analyses, similar significant associations were found when the exposure level was defined by the job title, but not the job-exposure matrix. In addition, significant associations between occupational exposure to ELF-EMF and increased risk of ALS were found in studies of subjects who were clinically diagnosed but not those based on the death certificate. Moderate heterogeneity was observed in all analyses.ConclusionsOur data suggest a slight but significant ALS risk increase among those with job titles related to relatively high levels of ELF-EMF exposure. Since the magnitude of estimated RR was relatively small, we cannot deny the possibility of potential biases at work. Electrical shocks or other unidentified variables associated with electrical occupations, rather than magnetic-field exposure, may be responsible for the observed associations with ALS.

Risk agents related to work and amyotrophic lateral sclerosis: An occupational medicine focus

“…Exposure to electromagnetic fields has been studied in epidemiological [62][63][64][65][66], observational [67] and laboratory works [68]. A recent meta-analysis suggests a slightly but significantly increased risk of ALS among workers exposed to an extremely low frequency electromagnetic field (ELF-EMF), but does not deny the possibility of bias in the data analysis [69]. However, in the case of electromagnetic fields, there are many problems: at present, no apparent correlation between the exposure assessment and the observed associations is possible.…”

The effects of extremely low frequency magnetic fields on mutation induction in mice

“…Additionally, two meta-analysis studies have analysed the previously reported associations of occupational magnetic field exposure with amyotrophic lateral sclerosis. Zhou et al (2012) reported significant increases in risk of ALS due to ELF-MF exposure based on 9 case-control studies (RR = 1.39) but not in 8 cohort studies (RR = 1.16, CI: 0.80-1.69). Similar findings are illustrated in the meta-analysis from Vergara et al (2013), who analysed 12 case-control studies reporting a significant increased risk of 1.38 for ALS, but again a weak associated risk of 1.14 from 9 cohort studies.…”

Amyotrophic lateral sclerosis and environmental factors

“…ELF-EMFs have frequencies ranging from 3 Hz to 3,000 Hz. Electricians, electrical and electronic equipment repairers, train drivers, telephone installers or repairers and machinists are constantly exposed to them (Zhou et al, 2012). Håkansson et al (2003) assessed the impact of ELFEMFs in a cohort of Swedish engineering industry workers and highlighted an increased risk of Alzheimer's disease (relative risk, RR 0.4; 95% CI 1.4-11.7) and of ALS (RR 2.2; 95% CI 1.0-4.7).…”

“…Similar results were reported by Huss et al (2014), comparing ALS mortality in 2000-2008 and job exposure to ELF-EMFs and electric shocks in the Swiss National Cohort. In 2012 an interesting meta-analysis of seventeen studies (Zhou et al, 2012) found an increased risk of ALS in pooled studies (RR 1.29, 95% CI 1.02-1.62), and in case-control studies, with an odds ratio (OR) of 1.39 (95% CI 1.05-1.84), but not in cohort studies, in which the RR was 1.16 (95% CI 0.80-1.69). The authors affirmed that the RR value was not high enough to exclude the possibility of biases.…”