Ambient manganese exposure is negatively associated with human sperm motility and concentration

BACKGROUND: Occupational and experimental animal studies indicate that exposure to high levels of manganese impairs male fertility, but the effects of ambient manganese in humans are not known. METHODS: We measured blood levels of manganese and selenium in 200 infertility clinic clients in a cross-sectional study. Correlations between metals and semen variables were determined, adjusting for other risk factors. Outcomes were low motility (<50% motile), low concentration (<20 million/mL), or low morphology (<4% normal). We also investigated dose-response relationships between quartiles of manganese exposure and sperm parameters. RESULTS: High manganese level was associated with increased risk of low sperm motility (odds ratio = 5.4; 95% confidence interval = 1.6-17.6) and low sperm concentration (2.4; 1.2-4.9). We saw a U-shaped dose-response pattern between quartiles of manganese exposure and all 3 sperm parameters. CONCLUSION: Ambient exposure to manganese levels is associated with a reduction in sperm motility and concentration. No adverse effects were seen for high selenium.