{"paper_id":"1a7fb5ce-2df0-4cc2-8bf8-1a1b1b2b6d1c","body_text":"Air pollution has a detrimental effect on health ( Pothirat  et al. , 2019 ). There are various pollutants in\nthe air including PM10, PM2.5, nitrogen dioxide, and ozone ( Pothirat  et al. , 2019 ). Ambient PM2.5\n(particulate matter smaller or equal to 2.5 micrometer; PM 2.5) is associated with\nrespiratory problems and cardiovascular disease ( Pothirat  et al. , 2019 ;  Nakharutai  et al. , 2022 ). Exposure to ambient PM2.5 and\nnitrogen dioxide has the highest impact on all-cause mortality in northern Thailand\n( Pinichka  et al .\n2017 ).\nPM2.5 inhalation directly affects alveolar cells, increases oxidative stress and\ncauses pulmonary injury ( Saffari  et\nal. , 2014 ;  Snow  et\nal. , 2014 ;  Liu  et\nal. , 2020 ). It also relates to systemic inflammation ( Chin, 2015 ). Furthermore, PM2.5 exposure causes\ntesticular injury and germ cell apoptosis in rats ( Liu  et al. , 2017 ).\nStudies regarding air pollution affecting sperm quality encompasses various reports\nthat ranged from both high to low impact. The various constituents of air\npollutants; amount and duration of exposure, might explain this contradiction ( Hansen  et al ., 2010 ;  Wu  et al ., 2017 ;  Wu  et al ., 2021 ;  Lao  et al ., 2018 ;  Nobles  et al ., 2018 ;  Chansuebsri  et al ., 2022 ).\nStrong correlations of PM2.5 exposure, 2-3 months before the time of semen analysis,\ngave hits that such exposure could play a role in the detrimental effect on\nspermatogenesis ( Hammoud  et al. ,\n2010 ;  Wu  et al. ,\n2017 ).\nChiang Mai is a northern province of Thailand, located in a basin-like terrain\nsurrounded by mountains. People in the rural area mostly work in agriculture. The\ndry season is the smoky haze pollution period in Chiang Mai ( Thepnuan  et al. , 2020 ). During this highly\nintense smoky period, the source of PM2.5 is a mixture of burning biomass, traffic\nexhaust fumes and transboundary pollution ( Thepnuan\n et al. , 2020 ;  Chansuebsri  et al. , 2022 ).\nThere are few reports about male fertility being affected by seasonal PM2.5 from the\nagricultural process. Therefore, the aim of this study was to explore the effect of\nambient PM2.5 on male fertility.\n\nData were collected from the medical records of men living in northern Thailand who\nunderwent semen analysis at the Infertile Clinic, Chiang Mai University between\nJanuary 2017 and December 2021. The data included demographics, sperm parameters and\noutcome of fertility treatment.\nThe semen analysis was carried out using an HTM IVOS II computer assisted semen\nanalysis (CASA; Hamilton Throne Biosciences, Beverly, MA), equipped with Clinical\nHuman Motility II Software to determine: sperm concentration, progressive motility\nand morphology.\nMonthly data of Chiang Mai ambient PM2.5 concentration, between January 2017 and\nDecember 2021, were collected from the Thai Pollution Control Department. Both the\nmean and maximum value of ambient PM2.5 were reported during the study period. A\nlevel of ambient PM2.5 over 50 µg/m 3  was considered unhealthy.\nThis study was approved by the Ethical Committee of the Faculty of Medicine, Chiang\nMai University with the exemption of the informed consent (OBG-2564-08563).\nIn order to compare the difference between two groups of data, the t-test was applied\nfor continuous data, with normal distribution. Otherwise, the non-parametric test\nwas used. The comparison between various groups of continuous data was carried out\nby the ANOVA test. The difference of categorical datasets was determined by the\nChi-squared test. The relationship between ambient PM2.5 concentration and sperm\nparameters were analyzed by Pearson’s correlation coefficients. Univariable and\nmultivariable logistic regression was conducted to identify the potential factors\nassociated with the chemical pregnancy rate.\nAll statistical tests were performed with the statistical package for social science\n(SPSS, USA version 22.0). A  p -value of less than 0.05 was\nconsidered statistically significant.\n\nDuring the study period, there was a high level of PM2.5 in a particular period of\neach year. There was a difference of ambient PM2.5 concentration in these five years\n(2017 to 2021). The mean ambient PM2.5 was highest in 2019 and lowest in 2017. The\nmaximum ambient PM2.5 was highest in 2019 and lowest in 2020, as shown in  Table 1a .\nAverage of mean and maximum ambient PM2.5 concentration between 2017 and\n2021.\np <0.001 both mean and maximum value.\nAccording to the difference in levels of ambient PM2.5 in individual years, the data\nwas broken down into two groups. Group 1 had the data from 2017, 2018 and 2020 and\nGroup 2 the years with higher ambient PM2.5, which were 2019 and 2021 ( Table 1b ).\nComparison of ambient PM2.5 concentration between Group 1 (2017, 2018 and\n2020) and 2 (2019 and 2021).\nThe participants comprised 1,109 men attending the Infertile Clinic for semen\nanalysis during the 5-year study period (2017 to 2021). The majority of them were\nreported as healthy and were involved in fertility management. The mean age was 34.6\nyears and the mean body mass index was 25.2 kg/m 2 . The demographic data\nof men undergoing semen analysis in Groups 1 and 2 were not statistically\nsignificant, as shown in  Table 2 .\nCharacteristics of the study subjects in Group 1 (2017, 2018 and 2020) and 2\n(2019 and 2021).\nData on homogenous sperm parameters were available during the study period, while\nPM2.5 values had seasonal variation, as shown in  Figures 1 - 4 .\nFigure 1 Ambient PM2.5 in each month and pool data of sperm concentration.\nAmbient PM2.5 in each month and pool data of sperm concentration.\nFigure 4 Ambient PM2.5 in each month and pool data of normal sperm morphology\npercentage.\nAmbient PM2.5 in each month and pool data of normal sperm morphology\npercentage.\nOverall data revealed weak positive correlation of the progressive sperm motility\npercentage and normal morphology at the time of PM2.5 exposure, as shown in  Table 3 .\nCorrelation of monthly mean ambient PM2.5 (µg/m 3 )\nconcentration between 2017 and 2022 and sperm parameters in different\nperiods of exposure.\nSubgroup analysis of the correlation between ambient PM2.5 and sperm parameters in\nyears with better climate revealed weak positive correlation of progressive motile\nsperm percentage following 1 month of PM2.5 exposure and 2 months of normal\nmorphologic sperm percentage (r=0.08,  p =0.05 and r=0.1,\n p =0.02), as shown in  Table\n4 . However, there was a negative correlation between each sperm parameter\nand level of PM2.5, especially following 3 months exposure before semen analysis in\nthe year with worse climate (r=-0.12,  p =0.01, r=-0.11,\n p =0.003, r=-0.15,  p =0.004), as shown in  Table 5 .\nCorrelation of monthly mean ambient PM2.5 (µg/m 3 )\nconcentration between 2017, 2018 and 2020 and sperm parameters in different\nperiods of exposure (Group 1; n=678).\nCorrelation of monthly mean ambient PM 2.5 (µg/m 3 )\nconcentration between 2019 and 2021 and sperm parameters in different\nperiods of exposure (Group 2; n=431).\nEighty-six men underwent fertility treatment within 1 month after semen analysis. The\nunivariable analysis among these men revealed that PM2.5 exposure did not affect the\nchance of conception. The infertility treatment was the only factor affecting\nchemical pregnancy rate, as shown in  Table\n6 .\nAssociated factors of conception among men who received fertility treatment\nwithin 1 month after semen analysis (n=86).\n\nAir pollution is an important global issue. The extent of the problem is reported\ndifferently by countries, periods, years and various aspects of volatile toxins and\na variety of particular matter ( Wu  et\nal. , 2017 ;  Qi  et\nal. , 2020 ;  Franzin  et\nal. , 2021 ;  Chansuebsri\n et al. , 2022 ;  Kahraman & Sivri, 2022 ;  Pereira\nBarboza  et al. , 2023 )\nAir pollution affects health by both direct inhalation and indirect pathways. The\nindirect effect from air pollution on male fertility is seen clearly in rat studies\n( Liu  et al. , 2017 ;  Liu  et al ., 2019 ). The\npathogenesis would be systemic inflammation and oxidative stress ( Chin, 2015 ;  Liu\n et al. , 2017 ;  Liu\n et al ., 2019 ).However, there is still no clear\nexplanation among human data.\nThe effect of ambient PM2.5 on sperm quality in this study is quite moderate. PM2.5\nexposure for 2-3 months before semen analysis affects sperm quality more than\nexposure on time. It seems that PM2.5 affects the spermatogenesis process, which\ntakes 70-90 days ( Hammoud  et al. ,\n2010 ;  Wu  et al. ,\n2017 ). Moderate results are similar to those in studies when ambient\nPM2.5 was not extremely high ( Hansen  et\nal ., 2010 ;  Lao  et\nal ., 2018 ;  Nobles  et\nal ., 2018 ). The constituents of air pollution could be\nanother important factor. The PM2.5 caused by industrial and traffic fumes contains\nmore toxin and might have more detrimental effect on health and sperm quality ( Hammoud  et al. , 2010 ;  Wu  et al. , 2017 ;  Wu  et al ., 2021 ;  Chansuebsri  et al. , 2022 ). The\nseasonal smoke haze from burning might be less harmful in that cell and tissue\ninjury could have more time to self-repair.\nA year with better climate and low level of ambient PM2.5, had a weak positive\ncorrelation between sperm quality and level of ambient PM2.5. This is contrary to\nthe hypothesis of adverse effect on health from PM2.5. The result of weak positive\ncorrelation also was found in other studies ( Hansen\n et al. , 2010 ;  Lao\n et al. , 2018 ), where the level of ambient PM2.5 was\nnot extremely high. It was hypothesized that the compensatory process might occur\nbefore the worst outcome, when chronic exposure or higher levels of PM2.5 appeared\n( Lao  et al. , 2018 ).\nFurther studies are necessary to confirm this hypothesis.\nThe outcome of fertility treatment among this small subgroup, within 1 month after\nsemen analysis, revealed that the level of PM2.5 exposure did not impact the chance\nof conception. Nevertheless, a larger sample size is needed to conclude this\nhypothesis. The different types and levels of air pollution might have different\neffects on fertility outcome.\nAir pollution has various aspects of volatile toxins and varied particular matter\n( Wu  et al. , 2017 ;  Chansuebsri  et al. , 2022 ). This\nstudy explored only PM2.5, and no other aspects of air pollution. Other confounding\nfactors affecting sperm quality could be temperature and humidity, which were not\nincluded in this study. The subjects in this study were rather homogenous in\ndemography, which might not answer similar questions in other groups of the\npopulation. This study did not have data on the protection and habits among\nindividuals regarding air pollution, such as outdoor activity, air filtering or\nfiltered masks ( Allen & Barn, 2020 ).\nFurther study on oxidative stress and DNA fragmentation would fill the knowledge gap\nbetween air pollution and sperm quality.\nIn conclusion, exposure to a high levels of PM2.5 affects sperm quality negatively in\nChiang Mai males. More studies are needed to explain the pathogenesis of PM2.5\naffecting spermatogenesis.","source_license":"CC-BY-4.0","license_restricted":false}