Superfund Research Program
Parkinsonism and Metal Exposures Among Welders
Project Leader: Harvey Checkoway (University of California-San Diego)
Grant Number: P42ES004696
Funding Period: 2009-2015
This project is a study of parkinsonism (PS) among professional shipyard welders. PS is a relatively common movement disorder characterized by tremor, slow movement, rigidity and postural instability. The primary goal of the project is to determine whether manganese (Mn), the major neurotoxic component of welding fume, is associated with risk and progression of PS.
This project builds on a cohort study initiated by colleagues from Washington University in St. Louis. In the current funding cycle, enrollment and follow up of the welders was completed, effectively reaching the target enrollment of 1000 welders, and completing approximately 1500 neurological exams in total. A neurologist specializing in movement disorders examined these workers for signs of PS. A questionnaire to assess symptoms of PS and detailed work histories was administered at the same time. A comparison group of 59 non-welders has also been examined. Dr. Checkoway and his research team have now estimated cumulative welding exposure overall and weighted by intensity of exposure for all participants.
Previously, the team reported a markedly greater prevalence of PS in the welders compared to the non-welder comparison group (16% vs. 0%) and initial findings regarding progression. Currently, they are conducting analyses on progression in the full dataset. These analyses indicate that the annual rate of change in the Unified Parkinson Disease Rating Scale motor subscore 3 (UPDRS3) is statistically significantly increased in relation to cumulative intensity-weighted welding exposure. In addition, they administered cognitive control function tests to approximately 60 welders; these tests suggest additional health effects of Mn. The research team also continued analyses of data from blood obtained at the time of the respective exams, and several manuscripts have been fully drafted or are under review. These pertain to the use of blood proteins as early markers of preclinical PS (in coordination with the Plasma Biomarkers for Parkinsonism in Welders project), predictors of blood manganese; persistent organic pollutants and PS; and welding exposure, NOS2 methylation and PS. They also presented findings on the latter and on DMT1 methylation at international conferences.