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. Conclusion 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.

Objectives Manganese exposure leads to diffuse cerebral metal deposition with the highest concentration in the globus pallidus associated with increased T1-weighted MRI signal. T1 signal intensity in extra-pallidal basal ganglia (caudate and putamen) has not been studied in occupationally exposed workers. Diffusion weighted imaging is a non-invasive measure of neuronal damage and may provide a quantification of neurotoxicity associated with welding and manganese exposure. This study investigated extra-pallidal T1 basal ganglia signal intensity as a marker of manganese exposure and basal ganglia diffusion weighted imaging abnormalities as a potential marker of neurotoxicity. Methods A 3T MR case:control imaging study was performed on 18 welders and 18 age- and gender-matched controls. Basal ganglia regions of interest were identified for each subject. T1-weighted intensity indices and apparent diffusion coefficients were generated for each region. Results All regional indices were higher in welders than controls (p≤0.05). Combined basal ganglia (ρ=0.610), caudate (ρ=0.645), anterior (ρ=0.595) and posterior putamen (ρ=0.511) indices were more correlated with exposure than pallidal (ρ=0.484) index. Welder apparent diffusion coefficient values were lower than controls for globus pallidus (p=0.03) and anterior putamen (p=0.004). Conclusions Welders demonstrated elevated T1 indices throughout the basal ganglia. Combined basal ganglia, caudate and putamen indices were more correlated with exposure than pallidal index suggesting more inclusive basal ganglia sampling results in better exposure markers. Elevated indices were associated with diffusion weighted abnormalities in the pallidum and anterior putamen suggesting neurotoxicity in these regions.

Background Previous studies suggest that welders frequently display parkinsonian signs, such as bradykinesia and tremor. Demonstrating that these parkinsonian findings are associated with reductions in quality of life (QoL) or health status could have important repercussions for worker safety and performance. Methods Subjects included 394 active workers exposed to welding fumes and evaluated for parkinsonism by movement disorders experts in a worksite-based epidemiology study. Subjects were diagnosed with parkinsonism if the Unified Parkinson Disease Rating Scale motor subsection part 3 (UPDRS3) score was >15. All subjects completed a Parkinson’s disease (PD) symptom questionnaire and the PDQ39, a widely used QoL and health status measure for PD. Results Total PDQ39 score and all subscores were greater in welders with parkinsonism than welders without parkinsonism, with the most significant differences observed for mobility, emotional well-being, and activities of daily living (ADL’s). The PDQ39 scores for welding exposed workers with parkinsonism were similar to scores seen in a group of early PD patients. Conclusion Parkinsonism in active, welding exposed workers is associated with reductions in health status and QoL affecting a broad range of categories and within the range seen in early PD.

This model may be improved with more detailed exposure determinants; however, the relatively large amount of variance explained by the final model along with the positive generalizability results of the cross-validation increases the confidence that the estimates derived from this model can be used for estimating welder exposures in absence of individual measurement data.