Blood Manganese as an Exposure Biomarker: State of the Evidence

Abstract

Despite evidence of adverse health effects resulting from exposure to manganese (Mn), biomarkers of exposure are poorly understood. To enhance understanding, mean blood Mn (MnB) and mean air Mn (MnA) were extracted from 63 exposure groups in 24 published papers, and the relationship was modeled using segmented regression. On a log/log scale, a positive association between MnA and MnB was observed among studies reporting MnA concentrations above about 10 μg/m³, although interpretation is limited by largely cross-sectional data, study design variability, and differences in exposure monitoring methods. Based on the results of the segmented regression, we hypothesize that below the concentration of about 10 μg/m³, Mn in the body is dominated by dietary Mn, and additional inhaled Mn only causes negligible changes in Mn levels unless the inhaled amount is substantial. However, stronger study designs are required to account for temporal characteristics of the MnA to MnB relationships that reflect the underlying physiology and toxicokinetics of Mn uptake and distribution. Thus, we present an inception cohort study design we have conducted among apprentice welders, and the analytical strengths this study design offers. To determine if blood could be a useful biomarker for Mn to be utilized by industrial hygienists in general industry requires additional time-specific analyses, which our inception cohort study design will allow.

Keywords:

• Biomarkers of exposure
• exposure assessment
• manganese
• occupational health
• welding

ACKNOWLEDGMENTS

The authors thank the welders and staff at Renton Technical College, Renton, Wash., without whom this study would not have been possible. The authors acknowledge the University of Washington Environmental Health Laboratory for analysis of biological and air samples and Michelle Eisen for help with data collection and analysis. Research reported in this publication was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health under award number R01ES017809. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.