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Manganese exposure assessment - the use of toenails as a biomarker of exposure in US welders.

Ward EJ; Bainter J; Snyder S; Dydak U; Rosenthal F
Toxicologist 2014 Mar; 138(1):406
Previous studies have shown that high exposure to manganese (Mn) in occupational settings may lead to neurological health effects. Currently, there is no established biomarker for Mn exposure. The objective of this study was to evaluate the hypothesis that toenail Mn concentration is reflective of an individual's Mn exposure from occupational and dietary sources in a population of welders. Toenail clippings of all ten toes were collected from fifteen career welders and nineteen controls. The toenail samples were cleaned and sonicated in Triton X-100 surfactant, digested using microwave acid digestion and analyzed for Mn using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for Mn. Respirable Mn exposure was estimated using a model combining air samples, work histories, and modifying factors such as ventilation and use of personal protective equipment. Dietary Mn and Fe were estimated with a food questionnaire. There was no significant difference between mean Mn concentration in right and left feet (4.89 vs. 4.27 ug/g, p = 0.1856). Toenail Mn levels were higher in welders than in controls (7.14 vs. 3.02 ug/g, p = 0.0003). Toenail Mn was significantly correlated with cumulative exposure to respirable Mn seven to twelve months prior to the toenail clipping date (r2 = 0.31, p = 0.03). When ratio of dietary intake of Mn to Fe, smoking, and age were included as covariates in the statistical model the correlation between respirable Mn exposure and toenail Mn improved (adjusted r2 = 0.56, p = 0.003). With two exceptions, toenail Mn was able to clearly distinguish exposed individuals from controls. The significant correlation of toenail Mn with the cumulative Mn exposure seven to twelve months prior to the toenail being clipped is consistent with the average growth time of toenails. The results suggest that toenail Mn is a valid, reproducible, easy to acquire biomarker of Mn exposure, which is feasible to use in an industrial welder population.
Toxicology; Exposure-levels; Workers; Work-environment; Humans; Men; Women; Environmental-exposure; Manganese-compounds; Biomarkers; Welders; Welding; Models; Air-samples; Ventilation; Personal-protective-equipment; Questionnaires; Food; Neurological-diseases; Neurological-reactions; Nervous-system; Nervous-system-disorders
Publication Date
Document Type
Funding Type
Fiscal Year
Identifying No.
Grant-Number-T03-OH-008615; M032014
Issue of Publication
Source Name
The Toxicologist. Society of Toxicology 53rd Annual Meeting and ToxExpo, March 23-27, 2014, Phonex, Arizona
Performing Organization
Purdue University, West Lafayette, Indiana
Page last reviewed: April 8, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division