Exposure to ambient PM2.5 constituents and semen quality in a retrospective cohort study: Windows of susceptibility and modification by greenness.

BACKGROUND

Access to abundant greenness and avoiding exposure to ambient fine particulate matter (PM2.5) are known to be associated with favorable health outcomes. However, evidence remains limited regarding the windows of susceptibility to exposure to PM2.5 constituents during spermatogenesis in relation to semen quality, as well as the modification role of residual greenness exposure.

OBJECTIVES

This study aimed to explore how greenness modifies the relationship of PM2.5 constituents with semen parameters across different developmental windows of spermatogenesis.

METHODS

We enrolled 6670 men whose partners underwent assisted reproductive technology procedures in Changsha, China. The PM2.5 constituents (nitrate [NO3-], sulfate [SO42-], ammonium [NH4+], organic matter [OM], and black carbon [BC]) exposures were estimated using machine learning models. We employed linear mixed models to estimate the associations of PM2.5 constituents with semen parameters across different windows, and to further explore potential effect modification by greenness.

RESULTS

Exposure to PM2.5 constituents was significantly associated with a decline in semen quality, including reductions in sperm concentration, count, motility, and increased immobilization. Conversely, higher greenness exposure was linked to improved semen quality. Notably, PM2.5 constituents like BC, SO42-, and OM consistently linked to decreased sperm count, with the strongest associations observed during the spermatogenic phase. Additionally, during the entire sperm development cycle, the relationships of PM2.5, BC, SO42-, OM, NO3-, and NH4+ with increased non-progressive motility were more pronounced in participants lived in areas with lower greenness (Pfor interaction < 0.05).

CONCLUSIONS

This study suggests that PM2.5 and its constituents are inversely associated with semen quality across all exposure windows, and this association is more pronounced during the spermatogenic stage. Meanwhile, higher greenness exposure during the entire sperm development cycle may attenuate the inverse associations of PM2.5 constituents on sperm non-progressive motility.