Are current biomarkers suitable for the assessment of manganese exposure in individual workers?

Background Whole blood and urinary manganese have been measured in occupational and environmental studies for the assessment of exposure. The aim of this study was to assess the relationship between the airborne concentrations of manganese and these biological indicators. Methods Environmental and biological monitoring was performed in a group of 94 employees in a ferroalloy production, who were exposed to manganese (Mn) oxides (MnO2 and Mn3O4). The results were compared with those from a control group of 87 subjects not exposed to Mn. Results Mn exposure levels ranged between 5 and 740 μg/m3, with arithmetic and geometric mean and median values being 202.6, 97.6, and 150 μg/m3, respectively. Arithmetic and geometric means for Mn in total blood (MnB) were, respectively, 10.3±3.8 and 9.7 μg/L in the exposed and 5.9±1.7 and 5.7 μg/L in the controls. For urinary Mn (MnU), arithmetic and geometric means were, respectively, 4.9±3.6 and 3.8 μg/L in the exposed and 1.2±1.4 and 0.7 μg/L in the controls. On a group comparison, a significant relationship was found between high and low exposed subgroups, identified according to Mn atmospheric concentrations (MnA), for both MnB (F value=38.0, P > 0.0001) and MnU (F value=36.1, P > 0.0001). On a linear relationship, a correlation was observed between MnA and MnB (r=0.34; r2=0.112; P=0.001), whereas no association was found between MnA and MnU. A significant relationship emerged also between MnB and MnU (r=0.48, r2=0.23, P