Ambient air pollution during developmental windows of spermatogenesis and semen quality among an infertility treatment seeking population

Prior studies have observed impacts of air pollution on semen quality, but timing of exposure during developmental windows of spermatogenesis and impacts of low-to-moderate air pollution is less well understood. We examined the relation between air pollution and semen quality in the Folic Acid and Zinc Supplementation Trial (2013-2018), which enrolled male partners of couples seeking infertility treatment in the Salt Lake City, Utah region (n = 2015). Semen quality parameters were assessed at baseline, 2-, 4-, and 6-months follow-up. Measures of daily air pollutants at each participant's residence were abstracted from Community Multiscale Air Quality models (fine particulate matter: PM_2.5, sulfur dioxide, nitrogen dioxide, and ozone: O₃), linked to participants' residential addresses, and averaged across the 74-day spermatogenesis window prior to the sample collection date for each study visit, and across four developmental windows of spermatogenesis (mitosis, meiosis I-II, spermiogenesis, and spermiation). Generalized linear mixed models considered four repeated semen sample measures per participant and adjusted for co-pollutants, age, season, and income. In multi-pollutant models, O₃ during early-to-mid spermatogenesis (meiosis I+II and spermiogenesis) was related to lower percent normal morphology (% difference -6.73, 95 % CI -9.82, -3.54 and % difference -3.83, 95 % CI -7.51, 0.00, respectively). Additionally, PM_2.5 and O₃ during late spermatogenesis (spermiation) were associated with lower count and concentration, and PM_2.5 with lower progressive motility. These findings suggest that exposure to low-to-moderate levels of air pollution may negatively impact semen quality and indicate that exposure to O₃ during meiosis and spermiogenesis may particularly affect normal sperm morphological development.