Reversibility of Neuroimaging Markers Influenced by Lifetime Occupational Manganese Exposure

Details

• Personal Author:
  Azizi E ; Dydak U ; Edmondson DA ; Ma RE ; Snyder S ; Ward E ; Wells EM ; Yeh C-L ; Zauber SE
• Description:
  Manganese (Mn) is a neurotoxicant that many workers are exposed to daily. There is limited knowledge about how changes in exposure levels impact measures in magnetic resonance imaging (MRI). We hypothesized that changes in Mn exposure would be reflected by changes in the MRI relaxation rate R1 and thalamic y-aminobutyric acid (GABAThal). As part of a prospective cohort study, 17 welders were recruited and imaged on 2 separate occasions approximately 2 years apart. MRI relaxometry was used to assess changes of Mn accumulation in the brain. Additionally, GABA was measured using magnetic resonance spectroscopy in the thalamic and striatal regions of the brain. Air Mn exposure ([Mn]Air) and cumulative exposure indexes of Mn (Mn-CEI) for the past 3 months (Mn-CEI3M), past year (Mn-CEI12M), and lifetime (Mn-CEILife) were calculated using personal air sampling and a comprehensive work history, whereas toenails were collected for analysis of internal Mn body burden. Finally, welders' motor function was examined using the Unified Parkinson's Disease Rating Scale (UPDRS). Median exposure decreased for all exposure measures between the first and second scan. deltaGABAThal was significantly correlated with delta Mn-CEI3M (p = 0.66, adjusted p = .02), delta Mn-CEI12M (p = 0.70, adjusted p = .006), and delta [Mn]Air (p = 0.77, adjusted p = .002). deltaGABAThal significantly decreased linearly with deltaMn-CEI3M (quantile regression, beta = 15.22, p = .02) as well as delta[Mn]Air (beta = 1.27, p = .04). Finally, Mn-CEILife interacted with delta[Mn]Air in the substantia nigra where higher Mn-CEILife lessened the deltaR1 per delta[Mn]Air (F-test, p = .005). Although R1 and GABA changed with Mn exposure, UPDRS was unaffected. In conclusion, our study shows that effects from changes in Mn exposure are reflected in thalamic GABA levels and brain Mn levels, as measured by R1, in most brain regions. [Description provided by NIOSH]
• Subjects:
  Cohort Studies Manganese Nervous System Occupational Exposure Occupational Health Safety Welding
• Keywords:
  Author Keywords: Manganese Brain Function Cohort Studies GABA Magnetic Resonance Imaging MRI Neurotoxic Agents Neurotoxic Effects Neurotoxicology Occupational Exposure Occupational Exposure To Manganese R1 Welders Welding

  More +
• ISSN:
  1096-6080
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Indiana ; Louisiana ; Minnesota ; OSHA Region 5 ; OSHA Region 6
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  181-190
• Volume:
  172
• Issue:
  1
• NIOSHTIC Number:
  nn:20059359
• Citation:
  Toxicol Sci 2019 Nov; 172(1):181-190
• Contact Point Address:
  David A. Edmondson, School of Health Sciences, Purdue University, West Lafayette, Indiana 47907
• Email:
  udydak@purdue.edu
• CAS Registry Number:
  Manganese (CAS RN 7439-96-5)
• Federal Fiscal Year:
  2020
• Performing Organization:
  Purdue University, West Lafayette, Indiana
• Peer Reviewed:
  True
• Start Date:
  20010701
• Source Full Name:
  Toxicological Sciences
• End Date:
  20270630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:b48421ebfb805eaeefe318161933d01d299d8486d0efeb6d3418b32dd2e21d2558efd37136fa399cb43ec8e8394a138a74f594939a62b6692166dbacce48d26b
• Download URL:
  https://stacks.cdc.gov/view/cdc/223619/cdc_223619_DS1.pdf
• File Type:
  [PDF - 617.94 KB ]