Manganese exposure among smelting workers: blood manganese–iron ratio as a novel tool for manganese exposure assessment

Abstract

Unexposed control subjects (n = 106), power distributing and office workers (n = 122), and manganese (Mn)-exposed ferroalloy smelter workers (n = 95) were recruited to the control, low and high groups, respectively. Mn concentrations in saliva, plasma, erythrocytes, urine and hair were significantly higher in both exposure groups than in the controls. The Fe concentration in plasma and erythrocytes, however, was significantly lower in Mn-exposed workers than in controls. The airborne Mn levels were significantly associated with Mn/Fe ratio (MIR) of erythrocytes (eMIR) (r = 0.77, p < 0.01) and plasma (pMIR) (r = 0.70, p < 0.01). The results suggest that the MIR may serve as a useful biomarker to distinguish Mn-exposed workers from the unexposed, control population.

Keywords::

• Manganese
• iron
• exposure assessment
• Mn-Fe ratio
• biomarker
• saliva
• erythrocyte
• smelter

Acknowledgements

The authors are indebted to Dr Bruce Craig and Ms Lei Shu, Department of Statistics at Purdue University for their assistance in designing statistic approaches, analyzing data and interpreting results presented in this work. This study was partly supported by U.S. Department of Defense Contract no. USAMRMC W81XWH-05-1-0239 (W.Z., M.A.), the U.S. NIH/National Institute of Environmental Health Sciences Grant no. ES-08164 (W.Z.), and by the National Natural Science Foundation of China Grant no. 30760209 (F.Q.Y., W.Z.). Dallas Cowan was partially supported by Training Grant No. T01 OH 008615 from the U.S. CDC/National Institute for Occupational Safety and Health. The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the NIHEHS, NIOSH and DoD.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.