Researchers have discovered that welders develop symptoms of parkinsonism — a general term referring to disorders that cause movement problems that resemble those of Parkinson’s disease — because of prolonged exposure to manganese, a chemical element from welding fumes.
The finding was reported in the study “Dose-dependent progression of parkinsonism in manganese-exposed welders,” which was published in the December edition of Neurology.
Its author, Dr. Brad A. Racette, a member of the American Academy of Neurology (AAN) and a researcher at the Washington University School of Medicine in St. Louis, wanted to explore the link between welding and parkinsonism.
“These welders are developing parkinsonian symptoms even though their exposure to manganese is below the current regulatory limits,” Racette said in a press release.
The study included 886 workers from two Midwestern shipyards and a heavy machinery factory. The workers were examined by neurologists at the beginning of the experiment, and 398 were chosen to participate in a follow-up study of 10 years.
Racette and his team measured exposure to manganese using a questionnaire, inquiring about the type of tasks workers had to perform for their jobs and the length of those tasks.
Researchers estimated that the average exposure was at a concentration of 0.14 mg of manganese per cubic meter.
Parkinsonism was found in 15 percent of the participants (135 people), who had scores of at least 15 on a scale from zero to 108. Cumulative manganese exposure also was linked to annual increases in scores on a test that was used to assess movement capacity.
Each additional milligram of manganese added an estimated 0.24 points on the movement scale.
“For example, a worker who had been a welder for 20 years before the first examination had an estimated 2.8 milligrams manganese per cubic meter years exposure and would be predicted to have nearly a seven-point increase on the movement test related to that welding fume exposure,” Racette said.
According to the U.S. Centers for Disease Control and Prevention, “prolonged exposure to high manganese concentrations (greater than 1 mg per cubic meter) in air may lead to a Parkinsonian syndrome known as ‘manganism.'”
Even after adjusting the results to account for other factors that might increase the risk of movement disorders including smoking, consuming alcohol and pesticide exposure — the results remained the same.
Cumulative manganese exposure was mostly connected with slow movements of the arms and hands, stiff arms and legs, speech troubles and reduced facial expression.
Welders who performed flux core arc welding in a confined space were found to have the highest scores, as this welding process generates the highest levels of particulate matter.
Results also were strong in workers examined within five years of their first day of welding work, possibly because those welders with longer work histories had already left their jobs after developing parkinsonism, researchers said.
The effects of other harmful metals in welding fumes, or of exposure to paints or solvents, should also not be ruled out, the team advised, but they were not a study focus.
“This study suggests that we need more stringent workplace monitoring of manganese exposure, greater use of protective equipment and monitoring and systematic assessment of workers to prevent this disabling disease,” Racette said.