Manganese Exposure Estimation and its Association with Blood Manganese
Eisen, Michelle E M
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Despite evidence of adverse health effects resulting from exposure to welding fume and in particular to manganese (Mn), biomarkers of exposure are poorly understood and have not been thoroughly evaluated in a longitudinal design. This study evaluates the relationship between well-characterized inhaled Mn exposure and whole blood Mn concentrations. A cohort of 34 apprentice welders was observed for three academic quarters during which subjects were exposed to welding fume. Personal airborne exposures to Mn and total particulate mass were measured five times each quarter and blood samples were taken twice on four days in each quarter for each subject. Individual characteristics with the potential to influence the relationship between air and biomarker concentrations, including type of welding and respirator use, were assessed in all subjects via questionnaire. Using these data, a mixed effects predictive model was developed to quantitatively estimate air Mn exposures on non-sampling days, allowing for both fixed and random effects. Air exposure results demonstrated that different welding types were significantly associated with air Mn exposure. The relationship between air exposure levels and predicted exposures were correlated to whole blood Mn levels using robust linear regression. No significant association was found between air exposure and blood Mn when compared across day. A statistically significant association was found between estimated quarterly air Mn exposure and cross-quarter blood Mn. This positive relationship indicated a loose association between increasing exposure and increasing difference in blood Mn levels. However, the overall results of this study indicate that blood Mn does not seem to be an effective short-term biomarker of exposure as analyzed. More data and a different time structure for analysis could lead towards a better understanding of blood Mn's association with air Mn exposure.
- Environmental health