title: Increased risk of parkinsonism associated with welding exposure.
abstract: OBJECTIVE
  Manganese (Mn), an established neurotoxicant, is a common component of welding fume. The neurological phenotype associated with welding exposures has not been well described. Prior epidemiologic evidence linking occupational welding to parkinsonism is mixed, and remains controversial.
  
  
  METHODS
  This was a cross-sectional and nested case-control study to investigate the prevalence and phenotype of parkinsonism among 811 shipyard and fabrication welders recruited from trade unions. Two reference groups included 59 non-welder trade workers and 118 newly diagnosed, untreated idiopathic PD patients. Study subjects were examined by a movement disorders specialist using the Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3). Parkinsonism cases were defined as welders with UPDRS3 score ≥15. Normal was defined as UPDRS3<6. Exposure was classified as intensity adjusted, cumulative years of welding. Adjusted prevalence ratios for parkinsonism were calculated in relation to quartiles of welding years.
  
  
  RESULTS
  The overall prevalence estimate of parkinsonism was 15.6% in welding exposed workers compared to 0% in the reference group. Among welders, we observed a U-shaped dose-response relation between weighted welding exposure-years and parkinsonism. UPDRS3 scores for most domains were similar between welders and newly diagnosed idiopathic Parkinson disease (PD) patients, except for greater frequency of rest tremor and asymmetry in PD patients.
  
  
  CONCLUSIONS
  This work-site based study among welders demonstrates a high prevalence of parkinsonism compared to nonwelding-exposed workers and a clinical phenotype that overlaps substantially with PD.
authors.affiliation: Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA. racetteb@neuro.wustl.edu
authors.forename: Brad A
authors.initials: BA
authors.lastname: Racette
authors.forename: Susan R
authors.initials: SR
authors.lastname: Criswell
authors.forename: Jessica I
authors.initials: JI
authors.lastname: Lundin
authors.forename: Angela
authors.initials: A
authors.lastname: Hobson
authors.forename: Noah
authors.initials: N
authors.lastname: Seixas
authors.forename: Paul T
authors.initials: PT
authors.lastname: Kotzbauer
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Evanoff
authors.forename: Joel S
authors.initials: JS
authors.lastname: Perlmutter
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Lianne
authors.initials: L
authors.lastname: Sheppard
authors.forename: Harvey
authors.initials: H
authors.lastname: Checkoway
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000139:chemically induced* / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D020734:Parkinsonian Disorders / Q000453:epidemiology* / Q000503:physiopathology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014896:Welding