Associations of ambient air pollutant exposure with seminal plasma MDA, sperm mtDNA copy number, and mtDNA integrity

•Volunteers under worse air condition had higher levels of seminal plasma MDA.•Air pollution especially SO2 exposure might be a risk of sperm oxidative damage.•Oxidative stress-related markers help assess air pollution-induced sperm damage. Current available evidence regarding the detrimental effects of low-level ambient air pollution on conventional semen parameters is inconclusive. In nonreproductive systems, air pollutant exposure has been demonstrated to induce oxidative stress (OS), which is a crucial mechanism that mediates sperm damage and male infertility. Thus, it may be essential to investigate the effects of air pollution on sperm quality in terms of the perspectives of OS and relative molecular damage. We assessed the associations of major air pollutant exposure to oxidative stress-mediated alterations in semen, including seminal plasma malondialdehyde (MDA), sperm mtDNA copy number, and integrity. The present study used data gathered from 516 young men participating in the Male Reproductive Health in Chongqing College student (MARCHS) cohort study during the follow-up stage in 2014 (n = 427 on the old campus, which is located in an urban area and has worse air quality, and n = 89 on the new campus, which is not urban and has better air quality). Data regarding major air pollutant exposure during 0–90, 0–9, 10–14 and 70–90 days before each semen examination (corresponding to the entire and three key periods of sperm development, respectively) were collected. The Mann-Whitney U nonparametric test was employed to compare distributions of major air pollutants and to explore differences in MDA, mtDNA copy number, and mtDNA integrity between the two campuses. A linear regression model was used as multivariable analysis to investigate associations of major air pollutant exposure with these biomarkers of oxidative damage to sperm and to adjust for potential confounders. During all four key periods of sperm development, compared with college students on the new campus, college students on the old campus were exposed to higher levels of PM10, PM2.5, NO2, and CO, and had higher air quality index (AQI) values, indicating that these participants suffered from worse air quality. The levels of seminal plasma MDA in college students on the old campus were higher than those for the new campus (2.0 nmol/ml; 0.7, 3.6 vs. 1.6 nmol/ml; 0.4, 3.4, p