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Workplace Exposures and Biomarkers of Parkinsonism in Welders

The etiology of Parkinson's disease is unknown although previous research has implicated environmental factors in most cases. We have previously shown that welding, an occupation performed by over 500,000 workers in the United States, may increase the risk of parkinsonism. These studies require confirmation in a rigorously designed study. The purpose of this grant is to determine whether occupational welding exposure is associated with clinical and brain imaging measures of parkinsonism. For this study we will recruit and screen 600 welders from the International Brotherhood of Boilermakers for parkinsonism. We will measure blood manganese levels to study recent exposure to welding fumes. We will also perform brain MRI and PET scans in a sub-group of these welders as a pilot project. Demonstrating a definitive relationship between welding and parkinsonism will have substantial public health impact since the majority of these cases should be preventable through worksite modifications.

Final Outcome

We found that in one area of the brain, PET scans indicated that welders had an average 11.7 percent reduction in a marker of the chemical dopamine compared to people who did not weld. Dopamine helps nerve cells communicate and is decreased in specific brain regions in people with Parkinson’s disease. The welders’ motor skills test scores also showed mild movement difficulties that were not as extensive as those found in the early Parkinson’s disease patients. Although the same area of the brain was affected as in Parkinson’s disease, the pattern of effects within this area was reversed. Parkinson's disease normally has the greatest impact on the rear of a structure known as the putamen. In the welders, the largest drop in the marker for dopamine occurred in a structure behind the putamen known as the caudate.

Presentations & Publications

  1. Hobson A, Seixas N, Sterling D, Racette BA. Estimation of particulate mass and manganese exposure levels among welders. Ann Occup Hyg, 2011;55(1):113-25.
  2. Criswell SR, Perlmutter JS, Videen TO, Moerlein SM, Flores HP, Birke AM, Racette BA. Reduced Uptake of [18F]FDOPA PET in ASymptoms & Side Effects Welders with Occupational Manganese Exposure. Neurology 2011; 6(15):1296-301.
  3. Hobson AJ, Sterling DA, Emo B, Evanoff BA, Sterling CS, Good L, Seixas N, Checkoway H, Racette BA. Validity and Reliability of an Occupational Exposure Questionnaire for Parkinsonism in Welders. J Occup Environ Hyg 2009;6(6):324-331.



  • Brad A. Racette, MD

    St. Louis, MO United States

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