title: Variance components of short-term biomarkers of manganese exposure in an inception cohort of welding trainees.
abstract: Various biomarkers of exposure have been explored as a way to quantitatively estimate an internal dose of manganese (Mn) exposure, but given the tight regulation of Mn in the body, inter-individual variability in baseline Mn levels, and variability in timing between exposure and uptake into various biological tissues, identification of a valuable and useful biomarker for Mn exposure has been elusive. Thus, a mixed model estimating variance components using restricted maximum likelihood was used to assess the within- and between-subject variance components in whole blood, plasma, and urine (MnB, MnP, and MnU, respectively) in a group of nine newly-exposed apprentice welders, on whom baseline and subsequent longitudinal samples were taken over a three month period. In MnB, the majority of variance was found to be between subjects (94%), while in MnP and MnU the majority of variance was found to be within subjects (79% and 99%, respectively), even when controlling for timing of sample. While blood seemed to exhibit a homeostatic control of Mn, plasma and urine, with the majority of the variance within subjects, did not. Results presented here demonstrate the importance of repeat measure or longitudinal study designs when assessing biomarkers of Mn, and the spurious associations that could result from cross-sectional analyses.
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA. Electronic address: bakermg@uw.edu.
authors.forename: Marissa G
authors.initials: MG
authors.lastname: Baker
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Simpson
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA; Department of Biostatistics, University of Washington, 1705 NE Pacific St., Seattle, WA 98195, USA.
authors.forename: Lianne
authors.initials: L
authors.lastname: Sheppard
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA; Department of Health Services, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA.
authors.forename: Bert
authors.initials: B
authors.lastname: Stover
authors.affiliation: Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire SK17 9JN, UK.
authors.forename: Jackie
authors.initials: J
authors.lastname: Morton
authors.affiliation: Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire SK17 9JN, UK.
authors.forename: John
authors.initials: J
authors.lastname: Cocker
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, 1959 Pacific St., Seattle, WA 98195, USA.
authors.forename: Noah
authors.initials: N
authors.lastname: Seixas
mesh_terms: D000395:Air Pollutants, Occupational / Q000097:blood* / Q000652:urine*; D015415:Biomarkers / Q000097:blood / Q000652:urine; D015331:Cohort Studies; D003710:Demography; D006801:Humans; D057230:Limit of Detection; D008345:Manganese / Q000097:blood* / Q000652:urine*; D016273:Occupational Exposure / Q000032:analysis*; D013997:Time Factors; D014896:Welding; D055815:Young Adult
chemical_list: D000395:Air Pollutants, Occupational; D015415:Biomarkers; D008345:Manganese
keywords: Biomarkers of exposure; Manganese; Variability; Welders