Background and aims: Biological monitoring plays an important role in occupational exposure assessment. The aim of present study was to assess Manganese-Iron Ratio (MIR) as a potential biomarker for manganese.

Methods: This cross-sectional study was carried out in an automotive parts manufacturing industry in Tehran, Iran. 31 ferroalloy smelters as exposed group (cases) and 30 office workers as unexposed control group were involved in the study. Occupational exposure to manganese was determined based on NIOSH analytical method 7300. Air and blood samples were analyzed using furnace- atomic absorption spectroscopy (GF-AAS). Serum Iron was measured according to Iron- Ferrozine LS. Statistical analysis was performed using SPSS software.

Results: The mean concentration of air Mn for smelter group was 0.008± 0.005 mg/m3. The mean manganese concentration in blood samples of smelter group (17.33± 8.66µg/L) was significantly higher than in the control group (9.37± 8.70µg/L), (P < 0.05). Also, the mean value of MIR in the smelter group was significantly higher than in the control group (P < 0.05). Correlation test showed significant relationship between air manganese and MIR (P < 0.05, r=0.426).

Conclusion: Manganese-Iron Ratio (MIR) can be used as a biomarker to distinguish manganese exposed workers from the unexposed population.