ST. LOUIS (AP) – A new study by Washington University in St. Louis researchers has found that current safety standards to protect welders from harmful fumes may be inadequate.

Dr. Brad A. Racette, senior author of the study, tells the St. Louis Post-Dispatch the research showed that the more exposure one had to airborne manganese, the greater the progression of parkinsonism, a neurological condition that causes tremors, muscle stiffness and other movement abnormalities.

The study examined nearly 900 welders at two shipyards and one heavy-machinery fabrication shop in the Midwest.

A spokesman from the Occupational Safety and Health Administration, the federal agency responsible for workplace safety, said in an email that its current thresholds don’t protect welders and that employers should ensure that workplace manganese exposure levels are well below the federal standard.