Even low manganese levels in welding fumes may harm workers

Welders exposed to airborne manganese even at levels below recommended safety standards may develop neurological problems similar to Parkinson's disease, a new study has warned.
Researchers at Washington University in the US said that the more workers are exposed to manganese-containing welding fumes, the faster their signs and symptoms worsen.
Manganese - a key component of important industrial processes such as welding and steelmaking - can cause manganism, a severe neurologic disorder with symptoms similar to Parkinson's disease, including slowness, clumsiness, tremours, mood changes and difficulty walking and speaking.
"We found that chronic exposure to manganese-containing welding fumes is associated with progressive neurological symptoms such as slow movement and difficulty speaking," said Brad A Racette from Washington University.

"The more exposure you have to welding fumes, the more quickly those symptoms progress over time," said Racette.
The risk of manganism drove the Occupational Safety and Health Administration (OSHA) decades ago to set standards limiting the amount of manganese in the air at workplaces.

While the safety standards are widely believed to have eliminated manganism as an occupational hazard, researchers who study the effects of manganese exposure have long suspected that there may still be some health effects at levels much lower than what is allowable per OSHA standards.
"This is the first study that shows clinically relevant health effects that are occurring at estimated exposures that are an order of magnitude lower than the limit," said Racette.

Researchers studied 886 welders at three worksites in the Midwest, two shipyards and a heavy-machinery fabrication shop.
Each welder filled out a job history questionnaire, which researchers used to calculate each participant's exposure by combining the estimated manganese exposure for specific job titles with the amount of time spent in each job.
Participants also underwent at least two standardised clinical evaluations of motor function spaced a year or more apart and using the Unified Parkinson's Disease Rating Scale.
The evaluations were performed by trained neurologists looking for signs of neurological damage such as muscle stiffness, gait instability, reduced facial expressions and slow movement.

A score of six or lower was considered normal on the evaluation scale, and those with scores of 15 or higher were placed in the parkinsonism category.
At their first evaluation, the welders had an average score of 8.8 and 15 per cent of the welders fell into the parkinsonism category.
Moreover, participants' scores increased over time and the welders exposed to the highest levels of manganese showed the biggest changes in their scores, an indication that their neurological problems were worsening faster than those of workers exposed to less manganese.
The study was published in the journal Neurology.