Objective To identify the biomarkers of early occupational manganese exposure by analyzing the alterations of saliva concentrations of manganese and urine concentrations of homovanillic acid among welders exposed to different levels of manganese.
Methods Welders (n=234) from 24 manganese enterprises in Qingpu District were selected as the exposure group. Samples of air manganese were collected by personal long-time sampling techniques. Further subgrouping was conducted according to the air manganese levels, workers were assigned to the low concentration group (TWA<0.15 mg/m3, n=113) and the high concentration group (TWA≥ 0.15 mg/m3, n=121), and those without manganese exposure history were selected as the control group (n=135). Saliva manganese and urine homovanillic acid of each group were measured.
Results The average saliva manganese concentration of the exposure group was (7.65& #177;5.57) μg/L, higher than that of the control group (P < 0.01). The average saliva manganese concentration of the high concentration group was (13.38& #177;15.36) μg/L, higher than that of the low concentration group (P < 0.01). The average saliva manganese concentration of those exposed to manganese for more than 5 years in the high concentration group was (16.94& #177;19.81) μg/L, which was higher than those exposed to manganese for less than 5 years in this group (P < 0.05). The average urine concentration of homovanillic acid of the exposure group was (6.79& #177;1.01) μg/L, higher than that of the control group (P < 0.01). The average urine concentration of homovanillic acid of the high concentration group was (7.58& #177;0.92) μg/L, higher than that of the low concentration group (P < 0.01).
Conclusion Saliva manganese could be a potential biomarker of occupational manganese exposure. Urine homovanillic could be a potential effect biomarker of occupational manganese exposure, and its concentration is increased in early exposure stage.
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