Associations of air pollution with semen quality and male infertility: A large-scale multicenter study in China

Air pollutants have been linked to adverse effects on male reproductive health. However, large-scale multicenter studies on the association of air pollutants with male infertility and semen quality remain scarce. Here, we retrospectively collected data from 25,682 men at three reproductive centers in eastern China from 2015 to 2022 to investigate the relationships between air pollution exposure, semen quality and male infertility risk at different stages of sperm development, and whether semen quality mediates the relationship between air pollutants and male infertility risk. The exposure levels of PM_2.5, PM₁₀, SO₂, NO₂, O₃, and CO during the entire period of sperm development for the study participants were 27.60 (IQR 21.40 -36.00) μg/m³, 47.70 (IQR 38.41 -59.56) μg/m³, 9.00 (IQR 7.64 -11.54) μg/m³, 29.60 (IQR 20.87 -39.24) μg/m³, 97.70 (IQR 83.15 -111.15) μg/m³, 0.80 (IQR 0.68 -0.88) mg/m³, respectively. During the sperm development period, higher levels of PM_2.5, PM₁₀, SO₂, NO₂ and CO exposure were associated with lower progressive motility and normal morphology, while associated with higher male infertility risk (all P < 0.05). These associations were also observed at different critical periods of sperm development, with effect sizes greater at spermatogenesis stage I and II (all P < 0.05). In addition, our results suggested that progressive motility and normal morphology statistically significantly mediated the association of air pollution exposure with male infertility risk (all P < 0.05). Our findings suggest an association between ambient air pollution and decreased semen quality as well as elevated male infertility risk, which appears to be partially mediated by reduced sperm motility and morphology.