Objectives The aim of this study was to investigate selected hormones and immunologic markers in manganese alloy production workers with current and long-term manganese exposure.

Methods One hundred randomly selected male workers exposed to manganese were compared with 100 male referents (matched for age) from similar process industries in a cross-sectional design.

Results The geometric mean of the exposed workers` urinary manganese concentration was 0.9 (range 0.1-126.3) nmol/mmol creatinine (Cr) versus 0.4 (range 0.1-13.1) nmol/mmol Cr for the referents. The mean duration of exposure to manganese was 20.0 (range 2.1-41.0) years. The geometric mean of the prolactin serum concentration was higher in the exposed subjects than in the referents (229 versus 197 mIE/l, P=0.06). Serum prolactin was associated with current exposure to "soluble inhalable manganese", duration of exposure, and smoking habits. The subjects with the longest duration of exposure to manganese or the highest current exposure to "soluble inhalable manganese" had a statistically significantly higher serum prolactin concentration than the referents. The smokers had a lower serum prolactin concentration than the nonsmokers. The concentrations of the measured immunologic markers were similar in the groups.

Conclusions The study indicates that manganese exposure can increase the serum prolactin concentration. Both duration and current level of exposure are related to the slight increase, which also appears to be modified by current smoking habits. The serum prolactin concentrations were generally within the reference limits of the laboratory and thus not suitable as an exposure marker at these exposure levels.

Key terms endocrine; immunologic marker; manganese; manganese alloy production worker; prolactin; smoking habit; soluble inhalable manganese