The impact of exposure to different ambient air pollutants on sperm quality: A retrospective cohort study.

Evidence suggests that poor semen quality is a cause of infertility, and exposure to air pollutants has been linked to its decline. To investigate this association, we conducted a retrospective cohort study of 5503 individuals in Guangdong, China, analyzing the relationship between ambient air pollution and semen quality across key stages of spermatogenesis. We estimated daily exposures to predominant contaminants, including PM10, PM2.5, NO2, SO2, CO, and O3. These analyses were concentrated on three critical periods of sperm development: 0-9, 10-14, and 70-90 days before ejaculation, to analyze the impact of individual and combined exposure to air pollutions on semen quality metrics. The study revealed that air pollutants, notably CO, NO2, and O3, adversely affect semen quality across sperm development stages. During period 1, exposure to these pollutants was associated with a reduction in semen volume (-1.49 %), concentration (-4.69 %), count (-6.11 %), total motility (-2.40 %), and progressive motility (-1.90 %). Similar trends were observed for P2 and P3, linked to PM10, PM2.5, CO, SO2, NO2, and O3. The results indicated that O3 was a key contributor to the decline in semen quality during sensitive developmental periods. Our study indicated that ambient air O3 exposure had a major impact on the poor semen quality, which highlighted the importance of reducing O3 for male reproductive health.