Abstract
OBJECTIVE: To assess the association between ambient ozone (O(3)) exposure and semen quality among men with unhealthy behaviours and low income. DESIGN AND SETTING: A case-control study was conducted from February 2024 to January 2025, in which male participants aged 18-45 years were recruited from Foshan, and following propensity score matching, a total of 820 participants were included in the final analysis. METHODS: The evaluated the association between O(3) exposure during the 70-90 days, 10-14 days, 0-9 days and 0-90 days prior to semen collection and semen quality using stepwise conditional logistic regression analyses, and restricted cubic splines were incorporated into the models. RESULTS: O(3) exposure during the 70-90 days and 0-90 days preceding semen sample collection was significantly associated with an increased risk of low semen quality, with ORs of 1.020 (95% CI 1.003 to 1.039) and 1.056 (95% CI 1.008 to 1.108), respectively. Additionally, O(3) exposure during the 0-90-days period showed a significant positive association with abnormal sperm concentration. A non-linear relationship between O(3) exposure and sperm concentration was also observed. Notably, O(3) exposure during the 0-9 days before semen collection was inversely associated with the risk of low semen quality. Subgroup analyses across age, lifestyle factors and socioeconomic strata revealed no significant effect modifications. CONCLUSION: This study found that O(3) exposure during the 70-90 days and 0-90 days before sampling was associated with reduced semen quality in men with unhealthy behaviours and low income.