Ambient Air Pollution and Semen Quality in China: A Nationwide Case-Control Study of 27,014 Males with Biomarker-Confirmed Semen Pathology

Amidst China's rapid industrialization and deteriorating air quality, emerging evidence suggests a parallel decline in male reproductive health. However, large-scale assessments of pollution-semen quality associations remain scarce. This nationwide multicenter study investigated these relationships among 27,014 Chinese men using high-resolution satellite-derived exposure estimates (PM_2.5, PM₁₀, NO₂, O₃, CO, and SO₂) and generalized linear mixed models (GLMM), adjusting for key demographic confounders. A case-control study involving 5256 cases and 21758 controls used the exposure values of air pollutants 90 days prior to sperm collection for epidemiological exposure analysis reactions to obtain the association between sperm quality and air pollution. This study demonstrates significant associations between increased exposure to regional air pollutants and the risk of substandard semen quality in China. Key findings reveal NO₂'s potential reproductive toxicity, showing a 79.7% increased risk of semen volume abnormalities per 11.34 µg/m³ exposure (OR = 1.797, 95% CI: 1.402-2.302). Susceptibility disparities emerged, with 16.4-fold greater PM_2.5 sensitivity in obese individuals (OR = 1.121 vs. 1.007) and 133% higher PM₁₀ risk in urban residents (OR = 1.342 vs. 1.006). Strikingly, SO₂ exposure at 15% of the WHO 24 h average guideline (6.16 µg/m³) was associated with a 3.8% increase in abnormalities, indicating the challenge of the current safety thresholds. These findings highlight the need for policy reforms, including (1) incorporating reproductive health endpoints into air quality standards, (2) implementing antioxidant interventions for high-risk groups, and (3) strengthening traffic emission controls in urban planning. This study underscores the need for comprehensive strategies to mitigate the impact of air pollution on male reproductive health.