Occupational exposure to ELF-MF and electric shocks and motor neurone disease

Background Although there are no established environmental or occupational risk factors for Motor Neurone Disease, an association with work in “electrical occupations” has been observed in numerous studies. However, the results of investigations using job-exposure matrices for extremely low frequency EMF and for electric shocks have been equivocal. In a population-based casecontrol study conducted in New Zealand we examined the effect of both electric shocks and ELF-MF. Methods We recruited cases from a voluntary register supplemented by notifications by neurologists. General population controls were selected from the Electoral Roll. A standardised questionnaire was used to obtain demographic and personal data, information on lifestyle factors plus a lifetime occupational history. Odds ratios were estimated for occupation, adjusting for age, gender, ethnicity, SES and smoking using logistic regression. The occupational histories of all participants were linked to jobexposure matrices on ELF-MF exposure and on electric shocks. Results We included 259 cases and 474 controls. There was no association between ELF-MF exposure and MND, with an OR = 1.1 (95% CI: 0.6-2.1) for the high exposure group. For electric shock the risk was elevated (but not statistically significantly) for both the medium OR = 1.3 (0.9-1.9) and high risk OR = 1.3 (0.0-1.9) groups when compared with the reference low risk group. Conclusions We found no strong evidence of elevated risk of MND associated with either ELF-MF or electric shock.