Association between residential greenness exposure and semen quality: A retrospective study in China.

Background: The association between greenness exposure and semen quality and the underlying mechanism are unclear.

Objectives: To assess the association between greenness exposure and semen quality and whether the association is mediated by air pollutant exposure.

Methods: We collected data from 10,273 men in Zhejiang, China, whose wives received assisted reproductive technology from 2015 to 2021. The mean exposure concentrations of air pollutants and greenness indices (normalized difference vegetation index (NDVI) and the soil-adjusted vegetation index (SAVI)) in the 300 m, 400 m, 800 m, and 1000 m buffer zones were assessed from 0-90 days prior to semen testing on the basis of the patient's residential address. A multivariate linear mixed-effects model was used to evaluate the associations, and mediation analysis was used to investigate the influences of air pollutant exposure and body mass index (BMI) on the associations.

Results: The average (standard deviation) age of the participants was 33.1 (5.2) years. After adjusting for confounders, progressive motility was positively associated with the NDVI (β (95 % CI): 1.744 (0.834, 2.655)) and SAVI (β (95 % CI): 1.484 (0.591, 2.377)). Furthermore, we found that NO and CO exposure significantly mediated part of the association between greenness exposure and progressive motility. Similar results are observed in the sensitivity analysis.

Conclusions: Our results suggest that greater greenness exposure is associated with higher semen quality and can be partially mediated by lower NO and CO exposure levels.