Chronic exposure to air pollution and semen quality in an Asian population

BACKGROUND AND AIM: Evidence concerning the association between air pollution and semen quality is sparse, and findings in previous studies remain inconsistent. This study aims to investigate the associations between exposure to ambient air pollution and semen quality in Asia. METHODS: A cross-sectional study was conducted among 7,658 male participants (aged ≥15 years) who participated in a standard medical examination program in Taiwan and Hong Kong between 2000 and 2018. The 2-year average concentration of PM₂.₅, NO₂, and O₃ was estimated at each participant’s address using satellite-based spatial-temporal models. Semen quality was assessed according to the WHO 1999 guidelines, including sperm concentration, total motility, progressive motility, and morphology. Generalized linear mixed models were used to examine the association between air pollution and sperm quality, with a region-level random intercept used in all models to control within-region clustering effects. RESULTS: Every 10 ug/m³ increase in NO₂ was associated with a decrease of -1.72% [95% confidence interval (CI): -2.68% to -0.75%] in sperm concentration. However, each 10 ug/m³ increase in PM₂.₅ and O₃ was associated with an increase of 3.13% (95%CI: 0.76% to 5.55%] and 2.88% (95%CI: 0.75% to 5.05%) in sperm concentration, respectively. In addition, each 10 ug/m³ increase in PM₂.₅ was associated with a lower percentage of normal sperm morphology, with a coefficient of -1.54 (95%CI: -2.41 to -0.68). There were no consistent associations between air pollution and other semen parameters. CONCLUSIONS: We found that exposure to ambient NO₂ was associated with a lower level of sperm concentration and exposure to ambient PM₂.₅ was associated with a lower level of normal sperm morphology. Further studies are warranted to validate our findings. KEYWORDS: Air pollution, ozone, male infertility, semen quality