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Exposure-response relationship and risk assessment for cognitive deficits in early welding-induced manganism.

Authors
Park-RM; Bowler-RM; Roels-HA
Source
J Occup Environ Med 2009 Oct; 51(10):1125-1136
NIOSHTIC No.
20036029
Abstract
Objective: The exposure-response relationship for manganese (Mn)-induced adverse nervous system effects is not well described. Symptoms and neuropsychological deficits associated with early manganism, were previously reported for welders constructing bridge piers during 2003 to 2004. A reanalysis using improved exposure, work history information, and diverse exposure metrics is presented here. Methods: Ten neuropsychological performance measures were examined, including working memory index (WMI), verbal intelligence quotient, design fluency, Stroop color word test, Rey-Osterrieth Complex Figure, and Auditory Consonant Trigram tests. AN blood levels and air sampling data in the form of both personal and area samples were available. The exposure metrics used were cumulative exposure to Mn, body burden assuming simple first-order kinetics for Mn elimination, and cumulative burden (effective dose). Benchmark doses were calculated. Results. Burden with a half-life of about 150 days was the best predictor of blood Mn. WMI performance declined by 3.6 (normal = 100, SD = 15),for each 1.0 mg/m(3) X mo exposure (P = 0.02, one toiled). A I the group mean exposure metric (burden; half-life = 275 days), WMI performance was at the lowest 17th percentile of normal, and at the maximum observed metric, performance was at the lowest 2.5 percentiles. Four other outcomes also exhibited statistically significant associations (verbal intelligence quotient, verbal comprehension index, design fluency, Stroop color word test); no dose-rate effect was observed for three of the five outcomes. Conclusions: A risk assessment performed for the five stronger effects, choosing various percentiles of normal performance to represent impairment, identified benchmark doses for a 2-year exposure leading to 5% excess impairment prevalence in the range of 0.03 to 0.15 mg/m3, or 30 to 150 g/m3, total Mn in air, levels that are far below those permitted by current occupational standards. More than one-third of workers would be impaired after working 2 years at 0.2 mg/m3 Mn (the current threshold limit value).
Keywords
Biochemistry; Biological-effects; Biological-factors; Biological-systems; Blood-sampling; Blood-tests; Chemical-hypersensitivity; Chemical-reactions; Construction-workers; Exposure-assessment; Exposure-levels; Exposure-methods; Health-hazards; Neurophysiological-effects; Occupational-exposure; Occupational-hazards; Occupational-health; Psychological-effects; Psychological-reactions; Psychological-testing; Risk-factors; Statistical-analysis; Welders; Worker-health; Work-operations; Work-performance; Workplace-studies; Work-practices
Contact
Robert M. Park, MSc, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Education and Information Division, MS C-15, 4676 Columbia Parkway, Cincinnati, OH 45226
CODEN
JOEMFM
CAS No.
7439-95-4
Publication Date
20091001
Document Type
Journal Article
Email Address
rhp9@cdc.gov
Fiscal Year
2010
NTIS Accession No.
NTIS Price
Issue of Publication
10
ISSN
1076-2752
NIOSH Division
EID
Priority Area
Construction
Source Name
Journal of Occupational and Environmental Medicine
State
OH; CA
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