Figure. Increase in Unified Parkinson’s Disease Rating Motor Scale 3 (UPDRS3) score due to welding fume exposure by years as a welder.

UPDRS3 increases with each additional year of work as a welder (mg [Mn]/m³-year exposure) as of the baseline examination. Among workers whose welding fume exposure was consistently as a welder, mg Mn/m³-year exposure is proportional to the number of years worked as a welder. A worker who had been a welder for 20 years prior to the baseline examination, for example, would have had an estimated 2.8 mg Mn/m³-year exposure and would be predicted to have nearly a 7-point increase in UPDRS3 score related to that welding fume exposure. This exposure estimate assumes a Mn concentration of 0.14 mg Mn/m³. CI = confidence interval.