The influence of lead exposure on male semen parameters: A systematic review and meta-analysis

Lead (Pb) is a metal with a widespread diffusion in the environment. Pb tends to accumulate in the human body and, as a consequence, semen alterations can be present in exposed workers or general population. The aim of the present study is to evaluate the effect on semen parameters among healthy men exposed to environmental or occupational Pb. A systematic literature search was performed on November 12th, 2022, through MEDLINE via PubMed, Scopus, and Embase. Observational studies comparing semen parameters in men exposed to Pb and those not exposed were included. Sperm parameters were pooled using the Cochran-Mantel-Haenszel Method with a random effect model. The weighted mean difference (WMD) was used as a summary measure. Statistical significance was set at p-value 0.05. Ten papers were included. Pb exposure was associated with a significant reduction in semen volume (WMD -0.76 ml.95% CI -1.47, -0.05, p = 0.04), sperm concentration (WMD -0.63 ×10⁶/ml 95% CI -1.15, -0.12, p = 0.02), total sperm count (WMD -1.94 ×10⁶ 95% CI -3. 77, -0.11, p = 0.04), sperm vitality (WMD -2.18% 95% CI -3.92, -0.45, p = 0.01), and total sperm motility (WMD -1.31% 95% CI -2.33, -0.30, p = 0.01). No difference was found in sperm normal morphology, progressive motility, and seminal viscosity. This review demonstrated the negative effect of Pb exposure on most of semen parameters. Given the diffuse exposure to this metal of the general population, public health concerns should be considered and exposed workers should be assessed to evaluate their semen.