The association was evident among men who had been exposed to jobs with relataively higher ELF-MF levels like - welders, line installers and aircraft pilots - essentialy those working in close proximity to electricity.
Amyotrophic lateral sclerosis (ALS) is a neurological disease, characterised by progressive degeneration of the motor nerve cells in the brain and spinal cord. There is currently no cure, and those affected usually die within a few years of diagnosis.
The study authors relied on data from the Netherlands Cohort Study. This has been looking at diet and cancer and has involved more than 58,000 men and more than 62,000 women, who were all aged between 55 and 69 when they were first entered the study in 1986.
Participants who had died of motor neurone disease (76 men and 60 women) were compared with around 4000 men and women who had been randomly selected for the purposes of the study. Their detailed employment histories were converted into workplace exposure to solvents, pesticides, metals, extremely low frequency magnetic fields and electric shocks, using job exposure matrices.
High levels of electromagnetic field exposure were largely confined to the men, and depended on job type. These ranged from 2-25% among the men; among the women, the equivalent figure was 0-2%. Participants’ neurological health was then tracked for an average of 17 years to see if any of them succumbed to ALS. During this time, 76 men and 60 women died of ALS. Occupational exposure to extremely low frequency electromagnetic fields was associated with a heightened risk of developing ALS among the men.
Those whose jobs had exposed them to high levels of extremely low electromagnetic fields were more than twice as likely to develop ALS as those who had never been exposed through their work.
Prof Paul Pharoah of the University of Cambridge, said: “The study of health risks associated with exposure to things in the environment like chemicals and is important. A large number of exposures were evaluated. Of these only occupational exposure to extremely low frequency magnetic fields was “significantly” associated with risk of ALS in men, but not women.