To investigate a possible common environmental exposure that may partially explain the observed decrease in human semen quality, we correlated seminal plasma and blood cadmium levels with sperm concentration and sperm motility. We studied three separate human populations: group 1, infertility patients (Long Island, NY, USA); group 2, artificial insemination donors (AID) (Rochester, NY, USA); and group 3, general population volunteers (Rochester, NY, USA). Information about confounding factors was collected by questionnaire. Seminal plasma cadmium did not correlate with blood cadmium (Spearman correlation, n = 91, r = -0.092, P = 0.386, NS). Both blood and seminal plasma cadmium were significantly higher among infertility patients than the other subjects studied (for example, median seminal plasma cadmium was 0.282 μg/L in infertility patients versus 0.091 μg/L in AID and 0.092 μg/L in general population volunteers; Kruskal-Wallis test, P < 0.001). The percentage of motile sperm and sperm concentration correlated inversely with seminal plasma cadmium among the infertility patients (r = -0.201, P < 0.036 and r = -0.189, P < 0.05, respectively), but not in the other two groups. Age (among infertility patients) was the only positive confounder correlating with seminal plasma cadmium. To validate our human findings in an animal model, we chronically exposed adolescent male Wistar rats to low-moderate cadmium in drinking water. Though otherwise healthy, the rats exhibited decreases in epididymal sperm count and sperm motility associated with cadmium dose and time of exposure. Our human and rat study results are consistent with the hypothesis that environmental cadmium exposures may contribute significantly to reduced human male sperm concentration and sperm motility.

Cadmium, a metal ion inducer of apoptosis, may contribute to this form of male infertility. Apoptosis may deplete the sperm concentration among men with varicocele and infertility. Pre-operative measurements of apoptosis and cadmium content may predict the outcome of varicocele repair.

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Multiple sperm parameters are affected as lead levels rise. Increased lead levels may contribute to the production of unexplained male infertility.

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