Ozone exposure and semen quality in low-income men with unhealthy behaviours in Foshan, China: a case-control study.

Abstract

To assess the association between ambient ozone (O₃) exposure and semen quality among men with unhealthy behaviours and low income. 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. The evaluated the association between O₃ 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. O₃ 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, O₃ exposure during the 0-90-days period showed a significant positive association with abnormal sperm concentration. A non-linear relationship between O₃ exposure and sperm concentration was also observed. Notably, O₃ 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. This study found that O₃ 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.