Cognitive Impairment of Welders and Non-Welding Factory Workers Compared to Non-Factory Controls: Manganese Is Not the Full Story

Details

• Personal Author:
  Harold, R. ; Mizimakoski, C. ; Aguiar, L. ; Islas, D. ; Lee, C. ; Park, J. ; Foti, D. ; Dydak, U.
• Description:
  Background and Purpose: Welders are occupationally exposed to manganese (Mn) via welding fumes. At high levels of exposure to Mn-such as in individuals working in Mn alloy plants, welding in enclosed spaces and living near open-air Mn storage- there are well-documented neurological consequences, including deficits in verbal learning, memory, and fine motor skills. However, most studies to date have compared individuals exposed to Mn to groups which are not well matched demographically (for example, comparing factory workers to university employees). The current study sought to directly investigate how welders exposed to Mn performed on tests of neuropsychological function relative to a well-matched group of factory workers employed at the same factory but who do not weld, as well as to a university control group Methods: 34 Welders (3 females; mean age=40.44+/-11.16) and 24 non-welding factory-worker controls e.g. assembly workers (8 females; mean age=42.96+/-12.19) were recruited from a nearby truck manufacturer; 10 non-factory worker controls were recruited from the university community (5 females; mean age=43.09+/-10.36). Cumulative exposure to Mn was modeled using each participant's work history and personal air sampling inside the welding hood over one work shift. Participants completed a comprehensive neuropsychological battery and a life-history questionnaire in conjunction with personalized air sampling in order to estimate their lifetime exposure to Mn. Groups were compared using one-way Analysis of Variance (ANOVA) and controlled for multiple comparisons using Tukey's Honestly Significant Difference (HSD) test. Results: There was a significant difference in lifetime exposure to Mn between groups (F2,65=5.619, p=0.006, eta=0.147), and this was driven by welder's significantly greater lifetime exposure to Mn (mean= 1.145 (mg/ m³)*yr) relative to factory controls (mean=0.124 (mg/m³)*yr; p=0.015) and to university controls (mean=0.001 (mg/m³)*yr; p=0.035). Participants were age and sex frequency matched between the welder and non-welder factory workers, but the university control group had a significantly higher percentage of females than the other two groups. With regard to neuropsychological functioning, groups exhibited significant differences in performance on a test of processing speed (NIH toolbox pattern comparison: F2,60=3.561, p=0.035, eta2=0.106), episodic memory (NIH toolbox picture sequence memory: F2,60=15.119, p<0.001, eta=0.335), nonverbal reasoning (PMAT: F2,65=6.607, p=0.002, eta=0.169), verbal fluency (Animal naming: F2,65=4.282, p=0.018, eta2=0.116), verbal acquisition (HVLT total recall: F2,64=6.850, p=.002, eta2=0.176), verbal learning (HVLT delayed recall: F2,64=3.491, p=0.036, eta2=0.098), fine motor dexterity (Grooved Pegboard dominant hand: F2,61=3.758, p=0.029, eta2=0.110; non-dominant hand: F2,62=5.380, p=0.007, eta2=0.148), and paranoid ideation (BSI: F2,65=3.310, p=0.043, eta2=0.092). These differences were in all cases driven by worse performance or worse symptoms among welders relative to university controls, but there were no observed differences between the welders and the well-matched factory worker control group. Conclusions: The welders in this study demonstrated significant deficits in several neuropsychological domains (processing speed, episodic memory, nonverbal reasoning, verbal fluency, verbal acquisition, verbal learning, fine motor dexterity, and symptoms of paranoid ideation) relative to controls recruited from the university community. The non-welding factory-worker controls exhibited no difference in these domains relative to the welders. This suggests the observed deficits in functioning are likely due to factors other than Mn neurotoxicity, such as shift work, exposure to non-Mn particulate matter, socio-economic status, etc. Limitations of this study are the small sample size of the university control group, which was not originally designed to serve as the control group. Furthermore, sex differences will need to be investigated in the future. The results of this study are of particular interest given the extant literature that has largely interpreted neuropsychological differences between welders or other metal workers and controls recruited from white-collar environments as being directly attributable to Mn exposure. Description provided by NIOSH
• Subjects:
  • Cognition
  • Manganese
  • Nervous System
  • Nervous System Diseases
  • Occupational Health
  • Safety
  • Welders
• Keywords:
  • Manganese; Welders; Welding fumes; Cognitive function; Neurotoxic effects; Neurotoxicology
• Source:
  Toxicologist 2025 Mar; 204(S1):363
• ISSN:
  1096-6080
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Chicago Region OSHA ; Indiana
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  2 pdf pages
• Volume:
  204
• NIOSHTIC Number:
  nn:20071596
• CAS Registry Number:
  • Manganese (CAS RN 7439-96-5)
• Federal Fiscal Year:
  2025
• Performing Organization:
  Purdue University, West Lafayette, Indiana
• Peer Reviewed:
  False
• Start Date:
  20010701
• End Date:
  20270630
• Download URL:
  https://stacks.cdc.gov/view/cdc/259371/cdc_259371_DS1.pdf
• File Type:
  [PDF - 260.17 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:92af826413477fc3ca83ca17208a8c25e6db6b9a14ec98308a7c16448067e269a5c091cdec814e7c84bc042adc14143e11f7d268cadf3cde48de78f3d34fbe18