Male Reproductive Toxicities Of Environmental Exposure To Polycyclic Aromatic Hydrocarbons And Phthalates

BackgroundIn recent years, reproductive health of male has been attracting attention of the people. An increasing number of studies have appeared linking exposure to environmental pollutants and reproductive health. It has been suggested that such environmental exposure may lead to abnormal reproductive outcomes by inducing changes in sperm parameters and/or altering the male genome at the gamete level. Our previous research studies showed that the main pollution chemicals of persistent organic pollutants (POPs) in the water body of the Three Georges reservoir was characterized by phthalates acid esters (PAEs) and polycyclic aromatic hydrocarbons (PAHs). Phthalates acid esters and polycyclic aromatic hydrocarbons have clearly been defied as endocrine disrupting chemicals, but the data from human population studies are very limited.ObjectivesThe present study was designed to study present situation of semen quality and relevant risk factors for young and middle-aged male at Three Gorges reservoir area; to determine whether environmental exposure to PAHs and PAEs contributes to the alteration in semen quality, sperm DNA damage and apoptosis in the general male human population; to provide theoretical basis for prevention of damage to reproductive capacity of male at Three Gorges reservoir area and to provide experiment data and explore a method to evaluate the adverse effect of environmental pollution on human reproductive health.MethodsPart?Study on semen quality of adult male in the area of Chongqing Three Gorges ReservoirA cross-sectional study was performed to evaluate the semen quality of healthy men residing in Chongqing Three Gorges Reservoir area. We selected three districts and three counties which are geographically and demographically representative of the Three Gorges Reservoir Region, including Wushan Yunyang and Wanzhou district and Wushan, Zhongxian and Yunyang County. 200-350 volunteers were selected as subject for study from each of study site. The semen parameters were measured and compared with the World Health Organization (WHO) criteria. A linear regression model was used to examine the determinants of semen quality.Part II Male reproductive toxicities of environmental exposure to polycyclic aromatic hydrocarbonsTotal 232 subjects residing in the Chongqing were recruited for this studies. Semen parameters were determined with the WHO criteria. Annexin V/PI assay and single cell gel electrophoresis (SCGE) were used to assess sperm apoptotic and DNA integrity, respectively. Urinary PAHs metabolites, including 2-hydroxynaphthalene (2-OHNa), 9-hydroxyphenanthrene (9-OHPh), 2-hydroxyfluorene (2-OHFlu) and 1-hydroxypyrene (1-OHP) were evaluated with high-performance liquid chromatography (HPLC) with fluorescence detection (FD). The potential association between exposures to PAH and semen quality, sperm apoptosis, DNA damage and reproductive hormones were evaluated by regression models.Part III Male reproductive toxicities of environmental exposure to phthalatesUrinary PAEs metabolites, including monobutyl phthalate (MBP), monobenzyl phthalate (MBzP), mono-ethyl phthalate (MEP), mono-(2-ethylhexyl) phthalate (MEHP) and phthalate acid (PA) were evaluated with high-performance liquid chromatography tadem mass spectrometry (HPLC-MS). Non-conditional logistic regression models were used to analyze the relationships between the dichotomized semen parameters and categorized (tertiles) PAE metabolite concentrations. The potential association between exposures to PAH and semen quality, sperm apoptosis, DNA damage and reproductive hormones were evaluated by regression models and partial correlation analysis.Results:Part?Study on semen quality of adult male in the area of Chongqing Three Gorges ReservoirThe medians were 2.3 ml for semen volume, 77.8×10~6/mL for semen concentration, 167.7×10~6 for total sperm count, 33% for sperm rapid progressive motility, 52.6% for sperm progressive motility and 28% for normal morphlogy. According to WHO criteria, 61.1% of healthy males had at least one semen parameter below normal threshold values. Season and abstinence duration were found to be significantly associated with semen quality (P<0.001). Age, smoking, alcohol use and BMI had little or no effect on semen parameters. The semen parameters in the study population were markedly different from those reported for the other Chinese, USA and European populations.Part II Male reproductive toxicities of environmental exposure to polycyclic aromatic hydrocarbonsIncreased urinary 2-hydroxynaphthalene levels were associated with increased comet parameters, including the percentage of DNA in the tail (?coefficient=13.26% per log unit 2-hydroxynaphthalene [?g/g creatinine]; 95% confidence interval [CI]: 7.97 to 18.55); tail length (12.25; 95% CI: 0.01 to 24.52) and tail distribution (7.55; 95% CI: 1.28 to 18.83). The urinary level of 1-hydroxypyrene was only associated with increased tail DNA percentages (5.32; 95% CI: 0.47 to 10.17). Additionally, the increased levels of four urinary PAH metabolites were significantly associated with decreased vital Annexin V negative sperm counts. The increased levels of four urinary PAH metabolites were significantly associated with decreased levels of LH and FSH. However, there was no significant association between urinary PAH metabolite levels and human semen parameters, testesterone or free testosterone index.Part III Male reproductive toxicities of environmental exposure to phthalatesFor MBP, MEP, MEHP and PA, no clear pattern of association were observed with any of the semen parameters. There was no significant correlation between urinary PAE metabolite levels and single cell gel electrophoresis parameters or Annexin V/PI assay parameters. However, there was no significant correlation between urinary PAE metabolite levels and testesterone level or free testosterone index. ConclusionsA high proportion of healthy males in Chongqing area of southwest China had abnormal semen parameters values according to WHO criteria. The environmental exposure levels of some PAHs affect human spermatozoa quality and male fertility. Our data indicate that the environmental level of PAE exposure is associated with increased follicle-stimulating hormone(FSH)and luteinizing hormone(LH) level but not with semen quality. Our study indicates that PAHs may disrupt male reproduction by damaging sperm DNA, rather than disrupting semen quality and triggering apoptosis of mature sperm. We speculate that the potential impact of exposure to environmental pollutants on human sperm DNA should be considered. Future large-scale studies should incorporate different markers and different seasons to generate a more accurate and full assessment of the adverse effects of PAH and PAE exposure on male fertility.