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

Background Whole blood and urinary manganese have been measured in occupati onal and environmental studies for the assessment of exposure. The aim of t his study was to assess the relationship between the airborne concentration s 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 cont rol group of 87 subjects not exposed to Mn. Results Mn exposure levels ranged between 5 and 740 mu g/m(3), with arithme tic and geometric mean and median values being 202.6 97.6 and 150 mu g/m(3) , respectively. Arithmetic and geometric means for Mn in total blood (MnB) were, respectively, 10.3 +/- 3.8 and 9.7 mu g/L in the exposed and 5.9 +/- 1.7 and 5.7 mu g/L in the controls. For urinary Mn (MnU), arithmetic and ge ometric means were, respectively, 4.9 +/- 3.6 and 3.8 mu g/L in the exposed and 1.2 +/- 1.4 and 0.7 mu g/L in the controls. On a group comparison, a s ignificant relationship was found between high and low exposed subgroups, i dentified 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 linea r relationship, a correlation was observed between MnA and MnB (r = 0.34; r (2) = 0.112; P = 0.001), whereas no association was found between MnA and M nU. A significant relationship emerged also between MnB and MnU (r = 0.48, r(2) = 0.23, P < 0.0001). No association was observed between an index of c umulative exposure and the biological indicators of exposure. Conclusion These results confirm that MnB and MnU can discriminate groups o f occupationally exposed workers from groups of nonexposed subjects. MnB is also related to the intensity of external exposure on a linear relationshi p, but given a high variability, it is not suitable for individual biologic al monitoring. Therefore, further research should focus on more accurate bi omarkers of Mn exposure. (C) 2000 Wiley-Liss, Inc.