Cadmium, Lead, and Other Metals in Relation to Semen Quality: Human Evidence for Molybdenum as a Male Reproductive Toxicant

Abstract

BackgroundEvidence on human semen quality as it relates to exposure to various metals, both essential (e.g., zinc, copper) and nonessential (e.g., cadmium, lead), is inconsistent. Most studies to date used small sample sizes and were unable to account for important covariates.ObjectivesOur goal in this study was to assess relationships between exposure to multiple metals at environmental levels and human semen-quality parameters.MethodsWe measured semen quality and metals in blood (arsenic, Cd, chromium, Cu, Pb, manganese, mercury, molybdenum, selenium, and Zn) among 219 men recruited through two infertility clinics. We used multiple statistical approaches to assess relationships between metals and semen quality while accounting for important covariates and various metals.ResultsAmong a number of notable findings, the associations involving Mo were the most consistent over the various statistical approaches. We found dose-dependent trends between Mo and declined sperm concentration and normal morphology, even when considering potential confounders and other metals. For example, adjusted odds ratios (ORs) for below-reference semen-quality parameters in the low, medium, and high Mo groups were 1.0 (reference), 1.4 [95% confidence interval (CI), 0.5–3.7], and 3.5 (95% CI, 1.1–11) for sperm concentration and 1.0 (reference), 0.8 (95% CI, 0.3–1.9), and 2.6 (95% CI, 1.0–7.0) for morphology. We also found preliminary evidence for interactions between Mo and low Cu or Zn. In stratified analyses, the adjusted ORs in the high Mo/low Cu group were 14.4 (1.6, 132) and 13.7 (1.6, 114) for below-reference sperm concentration and morphology, respectively.ConclusionsOur findings represent the first human evidence for an inverse association between Mo and semen quality. These relationships are consistent with animal data, but additional human and mechanistic studies are needed.

Reproductive Toxicity of Metals in Men

“…Median total mercury in blood of 1.10 μg L -1 has not been associated with parameters of semen quality or endocrine function (109,123). An increased risk of subfertility was found to be associated with increasing levels of mercury in hair (124) ) in Swedish fi shermen did not affect sperm concentration, count, motility, chromatin integrity, or the proportion of Y-chromosome bearing sperm (125).…”

“…Moreover, blood lead level <150 µg L -1 has been associated with higher serum levels of testosterone and oestradiol, and lower serum levels of prolactin (66). In men with median blood lead of 15 µg L -1 , an inverse association with serum prolactin and thyroid stimulating hormone (107) was found, but there was no association between blood lead levels and sperm concentration, motility or morphology (109). A Mexican study in men showed a signifi cant association between lower semen quality and lead in spermatozoa or seminal fl uid, but not with blood lead (106).…”

“…A Mexican study in men showed a signifi cant association between lower semen quality and lead in spermatozoa or seminal fl uid, but not with blood lead (106). All of these studies have been adjusted for the infl uence of age and current smoking (66,(105)(106)(107)(108)(109), and for other metals (66,105,(107)(108)(109). Other studies (110)(111)(112)(113)(114) have not found any association between low-level lead exposure and semen quality or endocrine function in men.…”

“…After adjusting for potential confounders, these effects included reduced testis size and higher serum levels of the follicle stimulating hormone, testosterone, and oestradiol (105). In men with median blood cadmium level of 0.20 µg L -1 , a positive association between blood cadmium and inhibin B levels in a model adjusted for age, BMI, and current smoking or for other metals (119) was found, but there were no effects on semen parameters (109). Urinary cadmium showed no significant association with serum testosterone, follicle stimulating hormone, and luteinizing hormone levels after adjusting for potential confounders (67).…”

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND PHENOLIC- AND CATECHOL-DEGRADING Enterobacter sp. STRAIN SAW-2

“…An elevated level of molybdenum in r uminants causes a disease known as hypercuprosis (Ward 1978). Recent data showed that molybdenum is toxic to spermatogenesis and embryogenesis in animals, including catfish and mice (Meeker et al 2008;Bi et al 2013;Zhai et al 2013;Zhang et al 2013). Toxic effect of molybdenum to these animals warrants removal of molybdenum from the environment.…”