Workplace exposure to electromagnetic fields has been linked to a higher risk of developing the most common form of motor neurone disease, Netherlands research suggests.
Experts noted an association between exposure to extremely low frequency electromagnetic fields and amyotrophic lateral sclerosis.
ALS causes weakness and wasting in the limbs and people only tend to live for two to five years from first experiencing symptoms.
In the new study, Professor Roel Vermeulen, from Utrecht University in the Netherlands, and colleagues, examined data for 58,279 men and 6,573 women aged 55 to 69, who were followed for 17 years.
Some 76 men and 60 women died of ALS during the study.
The research found that high levels of electromagnetic field exposure were largely confined to the men, and depended on their jobs.
Those whose jobs had exposed them to high levels of extremely low frequency electromagnetic fields were more than twice as likely to develop ALS as those who had never been exposed through their work, the study suggested.
Furthermore, those in the top 30 per cent of cumulative exposure (duration multiplied by intensity) were nearly twice as likely to develop the disease.
"Those whose jobs had exposed them to high levels of extremely low-frequency magnetic fields were more than twice as likely to develop ALS as those who had always been exposed to only background levels through their work," Prof Vermeulen said.
These jobs included electric line installers, welders, sewing-machine operators and aircraft pilots.
"These are essentially jobs where workers are placed in close proximity to appliances that use a lot of electricity," Prof Vermeulen said.
"The present study adds evidence to previous studies that have suggested that extremely low frequency electromagnetic fields is related to ALS risk."
Brian Dickie, director of research development at the Motor Neurone Disease Association said while the results suggested high exposure to low frequency magnetic fields is associated with the risk of MND, it was subtle.
"This only becomes apparent when relatively large numbers of people are studied, indicating that any such effect is a very subtle one.
"It does not mean that exposure causes MND.
