Impacts Of Air Pollution On Semen Quality

BackgroundAccording to the guidelines developed by the American Society for Reproductive Medicine（ASRM）in 2015,couples of childbearing age have normal sexual life,no contraceptive measures,and one year or more of infertility are called infertility.In the1990s,World Health Organization（WHO）data showed that the prevalence of infertility is as high as 10%-15%worldwide.In 2012,the survey results released by the China Population Association showed that infertility patients in China currently exceed 40 million,accounting for 12.5%of the population of childbearing age.Research shows that infertility caused by male factors accounts for 20 to 70%.However,only a few epidemiological studies have investigated the relationship between air pollutant exposure and semen quality,but the results are inconsistent.Due to poor living habits,eating habits,etc.,obese people are also on the rise,and the impact of obesity on the quality of semen has received widespread attention.Under the current trend of decreasing ambient air quality and rising obesity ratio,it is possible to make men’s semen quality decline trend more obvious.More research should be conducted on the relationship between air pollution and semen quality.ObjectiveEvaluate the exposure-response relationship between air pollution and semen quality at different stages of sperm development,and explore the sensitivity of sperm development to air pollutants at different stages;using body fat rate as an indicator of obesity,explore the modification of obesity in air pollution on semen quality.The effect provides a scientific basis for further research on air pollution on reproductive health.MethodsWe selected men who donated sperm from the human sperm bank in Guangdong Province from May 28,2018 to March 31,2019 as the study subjects.The inverse distance weighted interpolation method was used to estimate the personal exposures to CO,SO₂,NO₂,O₃,PM₁₀0 and PM_2.5.5 during the entire period（lag 0-90 days）and key periods（lag 0-9,10-14,70-90 days）of sperm development.Linear mixed models were used to evaluate the exposure-response relationships between air pollutants and semen quality,including sperm concentration,sperm count and sperm motility,after adjusting for other covariates.The regression coefficients and 95%confidence intervals（CIs）associated with each interquartile range（IQR）increase in pollutant exposure concentrations were estimated for each semen quality parameter.Furthermore,to assess the possible modification effects of factors including percent body fat（PBF）on the associations between air pollution and semen quality,we conducted separated analyses for different group:PBF（<25%and≥25%）.The difference betweenβin each group was estimated using Q-statistics for heterogeneity.Sensitivity analysis was carried out on the study subjects that met the WHO semen quality reference standard as a subgroup.ResultsPM₁₀（-0.2466;-0.4443,-0.0489）and PM_2.5（-0.2910;-0.5401,-0.0419）exposures were negatively correlated with sperm count.For the three key exposure periods,NO2,O3,PM10 and PM2.5 exposures during 10-14 lag days were significantly associated with sperm counts.O3 exposures during 0-9,and 10-14 lag days were significantly associated with total motility and progressive motility,respectively.SO2 exposures only during 10-14 lag days were significantly associated with progressive motility.Sensitivity analyses for a subgroup including subjects with normal sperm concentration,count and motility yielded similar results.No significant association was found between all pollutants and sperm concentration（all P>0.05）.Results of PM₁₀0 stratified by PBF showed that the largest reduction（β:-0.5997;P<0.05）in sperm count was observed among the group which PBF is greater than 25%.We did not observe heterogeneity in the associations between reduced each semen quality parameter and the exposures to other pollutants across different groups defined by PBF.ConclusionOur results suggest that ambient air pollutants exposures during sperm development adversely affect the semen quality,especially sperm count and motility,and highlight the potential to improve semen quality by reducing ambient air pollutant exposures during late stage of sperm development.Obese men in areas with severe PM10pollution have a greater decline in sperm count than non-obese men.Men in areas with severe PM10 pollution should pay more attention to their own living habits and eating habits to reduce the obesity rate.