Semen phthalate metabolites, spermatozoa apoptosis, and DNA damage: a cross-sectional study in China

Phthalate monoesters accumulation in residential indoor dust and influence factors

Phthalate monoesters (mPAEs) possess biological activity that matches or even exceeds that of their parent compounds, phthalate esters (PAEs), negatively impacting humans. Indoor dust is the main carrier of indoor pollutants. In this study, indoor dust samples were collected from 46 households in Changchun City, Jilin Province, in May 2019, and particulate and flocculent fibrous dust was used as the research target to analyze the concentration and compositional characteristics of mPAEs, primary metabolites of five significant PAEs. The influence of factors such as architectural features and living habits in residential areas on exposure to mPAEs was explored. Ten suspected enzyme genes along with two metabolic pathways with the ability to degrade PAEs were screened using PICRUSt2. The results showed that the total concentrations of the five mPAEs in the indoor dust samples were particulate dust (11.49-78.69 μg/g) and flocculent fibrous dust (21.61-72.63 μg/g), respectively. The molar concentration ratio (RC) of mPAEs to corresponding PAEs significantly differed among chemicals, with MMP/DMP and MEP/DEP sporting the highest RC values. Different bacterial types have shown distinct influences against mPAEs and PAEs. Enzyme function and metabolic pathway abundance had a significant effect on the concentration of some mPAEs, mPAEs are most likely derived from microbial degradation of PAEs.

Ameliorative effects of zinc and vitamin E against phthalates-induced reproductive toxicity in male rats

OBJECTIVE

Phthalates (PEs) could cause reproductive harm to males. A mixture of three widely used PEs (MPEs) was used to investigate the ameliorative effects of zinc (Zn) and vitamin E (VE) against male reproductive toxicity.

METHODS

Fifty male SD rats were randomly divided into five groups (n = 10). Rats in MPEs group were orally treated with 160 mg/kg/d MPEs, while rats in MPEs combined Zn and/or VE groups were treated with 160 mg/kg/d MPEs plus 25 mg/kg/d Zn and/or 25 mg/kg/d VE. After intervention for 70 days, it's was measured of male reproductive organs' weight, histopathological observation of sperms and testes, serum hormones, PIWI proteins and steroidogenic proteins.

RESULTS

Compared with control, anogenital distance, testes weight, epididymides weight, and sex hormones were significantly decreased, while the sperm malformation rate was markedly increased in MPEs group (p < .05); the testicular tissues were injured in MPEs group with disordered and decreased spermatids, and arrested spermatogenesis. PIWIL1, PIWIL2, StAR, CYP11A1 and CYP19A1 were down-regulated in MPEs group (p < .05). However, the alterations of these parameters were restored in MPEs combined Zn and/or VE groups (p < .05).

CONCLUSION

Zn and/or VE improved steroid hormone metabolism, and inhibited MPEs' male reproductive toxicity.

Associations between exposure to phthalates and liver function among women undergoing assisted reproductive technology

Phthalates can induce hepatotoxicity in animal studies. We aimed to assess the associations of individual and mixture of urinary phthalate metabolites with serum liver function indicators among 764 women undergoing assisted reproductive technology (ART). In linear models, we observed inverse correlations between urinary mono-benzyl phthalate and serum total protein (TP) as well as globulin (β=-0.27 and -0.23, respectively, P<0.05). Additionally, negative associations were identified between mono-isobutyl phthalate and mono-butyl phthalate (MBP) and aspartate aminotransferase-to-alanine transaminase ratio (AST/ALT) (P<0.05). MBP and the sum of all phthalate metabolites (∑all.phth.m) were positively associated with bilirubin, with β ranging from 0.14 to 0.47. Most phthalate metabolites were also positively related to gamma-glutamyl transferase (GGT) (all P<0.05). In Bayesian kernel machine regression models, phthalate mixture was positively associated with bilirubin and GGT, whereas inversely associated with AST/ALT and TP. Our results suggest that phthalate exposure may impair liver function among women undergoing ART.

Telomere length as a modifier in the relationship between phthalate metabolites exposure and glucose homeostasis

Given the rising concern over the potential impact of environmental factors on metabolic heath, we conducted a cross-sectional analysis among 645 adults aged 20 and older in the National Health and Nutrition Examination Survey (NHANES), examining the association between nine phthalate metabolites (Mono-n-butyl phthalate (MBP), Mono-ethyl phthalate (MEP), Mono-(2-ethyl)-hexyl phthalate (MEHP), Mono-benzyl phthalate (MBzP), Mono-n-methyl phthalate (MnMP), Mono-(3-carboxy propyl) phthalate (MCPP), Mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), Mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), Mono-isobutyl phthalate (MiBP)) and six glucose homeostasis indices (fasting glucose, fasting insulin, hemoglobin A1C (HbA1C), homeostatic model assessment of insulin resistance (HOMA-IR), single Point Insulin Sensitivity Estimator (SPISE), and HOMA-β). Latent Class Analysis identified three phthalate metabolites exposure patterns: high MEP-low MEOHP (n = 282), high MBzP-low MEHHP (n = 214), and high MEHHP, MEOHP (n = 149). The high MBzP-low MEHHP and high MEHHP, MEOHP, versus the high MEP-low MEOHP, exposure groups showed significantly higher levels of fasting insulin (β = 0.126, 95% CI: 0.023-0.228), SPISE (β = 0.091, 95% CI: 0.018-0.164), and HOMA-IR (β = 0.091, 95% CI: 0.018-0.164). In the shorter telomere length group, high MEHHP, MEOHP exposure showed an increase in SPISE levels (β = 0.153, 95% CI: 0.037-0.269), while in the overweight/obese subgroup, high MEHHP, MEOHP exposure was significantly positively associated with HOMA-IR (β = 0.392, 95% CI: 0.150-0.735). Bayesian kernel machine regression analyses showed positive associations between higher combined phthalate exposure and increased glucose homeostasis indices (fasting glucose, HbA1C, fasting insulin, SPISE, and HOMA-IR). The quantile of g-calculation analysis also supported the positive associations with HbA1C, HOMA-IR, and fasting insulin. Our findings indicate that phthalate exposure was positively associated with glucose homeostasis indices, which strengthen the call for proactive measures to reduce phthalate exposure and mitigate potential risks to glucose metabolism.

Long-term exposure to the mixture of phthalates induced male reproductive toxicity in rats and the alleviative effects of quercetin

Phthalates (PEs), such as di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP) could cause reproductive and developmental toxicities, while human beings are increasingly exposed to them at low-doses. Phytochemical quercetin (Que) is a flavonoid that has estrogenic effect, anti-inflammatory and anti-oxidant effects. This study was conducted to assess the alleviative effect of Que. on male reproductive toxicity induced by the mixture of three commonly used PEs (MPEs) at low-dose in rats, and explore the underlying mechanism. Male rats were treated with MPEs (16 mg/kg/day) and/or Que. (50 mg/kg/d) for 91 days. The results showed that MPEs exposure caused male reproductive injuries, such as decreased serum sex hormones levels, abnormal testicular pathological structure, increased abnormal sperm rate and changed expressions of PIWIL1 and PIWIL2. Furthermore, MPEs also changed the expression of steroidogenic proteins in steroid hormone metabolism, including StAR, CYP11A1, CYP17A1, 17β-HSD, CYP19A1. However, the alterations of these parameters were reversed by Que. MPEs caused male reproductive injuries in rats; Que. inhibited MPEs' male reproductive toxicity, which might relate to the improvement of testosterone biosynthesis.

Alleviative effect of quercetin against reproductive toxicity induced by chronic exposure to the mixture of phthalates in male rats

Phthalates (PEs) are widely used plasticizers in polymer products, and humans are increasingly exposed to them. This study was designed to investigate the alleviative effect of phytochemicals quercetin (Que) against male reproductive toxicity caused by the mixture of three commonly used PEs (MPEs), and further to explore the underlying mechanism. Forty-eight male SD rats were randomly and evenly divided into control group, Que group, MPEs group and MPEs+Que group (n = 12); The oral exposure doses of MPEs and Que were 450 mg/kg/d and 50 mg/kg/d, respectively. After 91 days of continuous intervention, compared with control group, the testes weight, epididymis weight, serum sex hormones, and anogenital distance were significantly decreased in MPEs group (P < 0.05); Testicular histopathological observation showed that all seminiferous tubules were atrophy, leydig cells were hyperplasia, spermatogenic cells growth were arrested in MPEs group. Ultrastructural observation of testicular germ cells showed that the edges of the nuclear membranes were indistinct, and the mitochondria were severely damaged with the cristae disrupted, decreased or even disappeared in MPEs group. Immunohistochemistry and Western blot analysis showed that testicular CYP11A1, CYP17A1 and 17β-HSD were up-regulated, while StAR, PIWIL1 and PIWIL2 were down-regulated in MPEs group (P < 0.05); However, the alterations of these parameters were restored in MPEs+Que group. The results indicated MPEs disturbed steroid hormone metabolism, and caused male reproductive injuries; whereas, Que could inhibit MPEs' male reproductive toxicity, which might relate to the restored regulation of steroid hormone metabolism.

Exploring the Occurrence of Organic Contaminants in Human Semen through an Innovative LC-HRMS-Based Methodology Suitable for Target and Nontarget Analysis

Understanding the potential impact of organic contaminants on male fertility is crucial, yet limited studies have examined these chemicals in semen, with most focusing on urine and blood. To address this gap, we developed and validated a robust LC-HRMS methodology for semen analysis, with a focus on polar and semipolar chemicals. Our methodology enables the quantitative (or semiquantitative) analysis of >2000 chemicals being compatible with suspect and nontarget strategies and providing unprecedented insights into the occurrence and potential bioaccumulation of diverse contaminants in this matrix. We comprehensively analyzed exogenous organic chemicals and associated metabolites in ten semen samples from Spanish participants collected in an area with a large presence of the chemical industry included in the LED-FERTYL Spanish study cohort. This investigation revealed the presence of various contaminants in semen, including plastic additives, PFAS, flame retardants, surfactants, and insecticides. Notably, prevalent plastic additives such as phthalic acid esters and bisphenols were identified, indicating potential health risks. Additionally, we uncovered previously understudied chemicals like the tire additive 2-mercaptobenzothiazole and specific organophosphate flame retardants. This study showcases the potential of our methodology as a valuable tool for large-scale cohort studies, providing insights into the association between contaminant exposure and the risk of male fertility impairments.

Phthalate exposure with sperm quality among healthy Chinese male adults: The role of sperm cellular function

Adverse male reproduction caused by phthalate ester (PAE) exposure has been well documented in vivo. However, existing evidence from population studies remains inadequate to demonstrate the impact of PAE exposure on spermatogenesis and underlying mechanisms. Our present study aimed to explore the potential link between PAE exposure and sperm quality and the possible mediation by sperm mitochondrial and telomere in healthy male adults recruited from the Hubei Province Human Sperm Bank, China. Nine PAEs were determined in one pooled urine sample prepared from multiple collections during the spermatogenesis period from the same participant. Sperm telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were determined in sperm samples. The sperm concentration and count per quartile increment in mixture concentrations were -4.10 million/mL (-7.12, -1.08) and -13.52% (-21.62%, -4.59%), respectively. We found one quartile increase in PAE mixture concentrations to be marginally associated with sperm mtDNAcn (β = 0.09, 95% CI: -0.01, 0.19). Mediation analysis showed that sperm mtDNAcn significantly explained 24.6% and 32.5% of the relationships of mono-2-ethylhexyl phthalate (MEHP) with sperm concentration and sperm count (β = -0.44 million/mL, 95% CI: -0.82, -0.08; β = -1.35, 95% CI: -2.54, -0.26, respectively). Our study provided a novel insight into the mixed effect of PAEs on adverse semen quality and the potential mediation role of sperm mtDNAcn.

From oxidative imbalance to compromised standard sperm parameters: Toxicological aspect of phthalate esters on spermatozoa

The exponential rise in global male infertility and subfertility-related issues raises severe concern. One of the major contributors is phthalate esters, typical endocrine disruptors affecting millions of lives. The inevitable exposure to phthalates due to their universal application as plasticizers leaves the human population vulnerable to this silent threat. This review explicitly deals with the spermiotoxic effects of different phthalate esters on in vivo and in vitro models and on surveyed human populations to find the most plausible link between global usage of phthalates and poor sperm health. As the free radicals in spermatozoa are prerequisites for their standard structure and functioning, the precise regulation and phthalate-mediated impairment of pro-oxidant:anti-oxidant balance with subsequent loss of structural and functional integrity have also been critically discussed. Furthermore, we also provided future directives, which, if addressed, will fill the still-existing lacunae in phthalate-mediated male reproductive toxicity research.

Seminal plasma metabolomics analysis of differences in liquid preservation ability of boar sperm

The preservation of semen is pivotal in animal reproduction to ensure successful fertilization and genetic improvement of livestock and poultry. However, investigating the underlying causes of differences in sperm liquid preservation ability and identifying relevant biomarkers remains a challenge. This study utilized liquid chromatography-mass spectrometry (LC-MS) to analyze the metabolite composition of seminal plasma (SP) from two groups with extreme differences in sperm liquid preservation ability. The two groups namely the good liquid preservation ability (GPA) and the poor preservation ability (PPA). The aim was to explore the relationship between metabolite composition in SP and sperm liquid preservation ability, and to identify candidate biomarkers associated with this ability of sperm. The results revealed the identification of 756 metabolites and 70 differentially expressed metabolites (DEM) in the SP from two groups of boar semen with differing liquid preservation abilities at 17 °C. The majority of identified metabolites in the SP belonged to organic acids and derivatives as well as lipids and lipid-like molecules. The DEM in the SP primarily consisted of amino acids, peptides, and analogs. The Kyoto Encyclopedia of Genes and Genomes analysis also demonstrated that the DEM are mainly concentrated in amino acid synthesis and metabolism-related pathways (P < 0.05). Furthermore, eleven key metabolites were identified and six target amino acids were verified, and the results were consistent with the non-targeted metabolic analysis. These findings indicated that amino acids and their associated pathways play a potential role in determining boar sperm quality and liquid preservation ability. D-proline, arginine, L-citrulline, phenylalanine, leucine, DL-proline, DL-serine, and indole may serve as potential biomarkers for early assessment of boar sperm liquid preservation ability. The findings of this study are helpful in understanding the causes and mechanisms of differences in the liquid preservation ability of boar sperm, and provide valuable insights for improving semen quality assessment methods and developing novel extenders or protocols.

Parental Programming of Offspring Health: The Intricate Interplay between Diet, Environment, Reproduction and Development

As adults, our health can be influenced by a range of lifestyle and environmental factors, increasing the risk for developing a series of non-communicable diseases such as type 2 diabetes, heart disease and obesity. Over the past few decades, our understanding of how our adult health can be shaped by events occurring before birth has developed into a well-supported concept, the Developmental Origins of Health and Disease (DOHaD). Supported by epidemiological data and experimental studies, specific mechanisms have been defined linking environmental perturbations, disrupted fetal and neonatal development and adult ill-health. Originally, such studies focused on the significance of poor maternal health during pregnancy. However, the role of the father in directing the development and well-being of his offspring has come into recent focus. Whereas these studies identify the individual role of each parent in shaping the long-term health of their offspring, few studies have explored the combined influences of both parents on offspring well-being. Such understanding is necessary as parental influences on offspring development extend beyond the direct genetic contributions from the sperm and oocyte. This article reviews our current understanding of the parental contribution to offspring health, exploring some of the mechanisms linking parental well-being with gamete quality, embryo development and offspring health.

Associations between phthalate exposure and thyroid function in pregnant women during the first trimester

Phthalates are a class of environmental endocrine disruptors. Previous studies have demonstrated that phthalate exposure can affect thyroid function; however, limited studies have assessed the associations between phthalate exposure and thyroid function, especially thyroid autoimmunity in pregnant women during the first trimester. We recruited participants from a cohort of pregnant women in Beijing, China, and collected urine samples to measure ten phthalate metabolites, serum samples to measure free thyroxine (FT₄), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb) during the first trimester. We included 325 pregnant women without thyroid diseases or dysfunction in this study. Associations between phthalate metabolites and thyroid function parameters were assessed with the Bayesian kernel machine regression (BKMR) model, multiple linear regression model, and restricted cubic spline. In the BKMR model analysis, compared to the 50th percentile, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels when phthalate metabolites were at or below the 40th percentile. Stratifying by body mass index, total urinary phthalate metabolites levels were negatively associated with serum TPOAb levels in normal weight women when phthalate metabolites were at or below the 45th percentile. However, total urinary phthalate metabolites levels were positively associated with serum TPOAb levels in underweight women when phthalate metabolites were at or below the 30th percentile. In restricted cubic spline analysis, L-shaped nonlinear associations of mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), di-(2-ethylhexyl) phthalate (ΣDEHP), and inverted S-shaped nonlinear association of mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) with TPOAb were observed. In conclusion, our findings suggest that phthalate exposure may affect thyroid autoimmunity in underweight pregnant women during early pregnancy, and the potential effects of phthalate exposure on thyroid autoimmunity may be nonlinear.

Associations of Urinary Trichloroacetic Acid Concentrations with Spermatozoa Apoptosis and DNA Damage in a Chinese Population

Exposure to trichloroacetic acid (TCAA) has been associated with impaired semen quality; however, its association with spermatozoa apoptosis and DNA damage remains unclear. We, therefore, collected single semen and repeated urine samples from male partners of couples attending a reproductive center, which were measured for spermatozoa apoptosis and DNA damage parameters and TCAA concentrations, respectively. Multivariable linear regression models were used to explore the associations between urinary TCAA concentrations and spermatozoa apoptosis (n = 462) and DNA damage parameters (n = 512). After adjusting for potential confounders, positive dose-response relationships were found between urinary TCAA concentrations and percentage of tail DNA (tail%) and tail-distributed moment (TDM) (both p for trend <0.10). Compared with men in the lowest tertile of urinary TCAA concentrations, men in the highest tertile had a greater tail% and TDM of 6.2% (95% CI: 0.7, 12.2%) and 8.9% (95% CI: -1.9, 20.5%), respectively. Urinary TCAA concentrations were unrelated to spermatozoa apoptosis parameters in a dose-response manner. However, urinary TCAA concentrations were positively associated with the percentage of Annexin V⁺/PI^- spermatozoa (apoptotic cells), when urinary TCAA concentrations were modeled as continuous variables. Our results suggest that exposure to TCAA at concentrations in real-world scenarios may be associated with spermatozoa apoptosis and DNA damage.

The Association of Certain Seminal Phthalate Metabolites on Spermatozoa Apoptosis: An Exploratory Mediation Analysis via Sperm Protamine

Earlier studies have suggested that exposure to phthalates (PAEs) may induce spermatozoa apoptosis. Sperm protamine as a molecular biomarker during spermatozoa apoptotic processes may mediate the association between PAE exposure and spermatozoa apoptosis. This study aimed to explore whether sperm protamine mediates the association of PAE exposure with spermatozoa apoptosis. We determined sperm protamine levels, 8 PAE metabolite concentrations in seminal plasma, and 3 spermatozoa apoptosis parameters among 111 men from an infertility clinic. The associations of PAEs as individual chemicals and mixtures with sperm protamine were determined. The mediating roles of protamine in the associations between PAEs and spermatozoa apoptosis parameters were examined by mediation analysis. After adjusting for confounders, we observed positive correlations between seminal plasma concentrations of mono(2-ethylhexyl) phthalate (MEHP) and sperm protamine-1 and protamine ratio. Estimates comparing highest vs. lowest quartiles of MEHP concentration were 4.65% (95% CI: 1.47%, 7.82%) for protamine-1 and 25.86% (95% CI: 3.05%, 53.73%) for protamine ratio. The quantile g-computation models showed that the adjusted protamine-1 per quartile increase in PAE mixture was 9.42% (95% CI: 1.00, 20.92) with MEHP being the major contributor. Although the joint association between PAE mixture and protamine ratio was negligible, MEHP was still identified as the main contributor. Furthermore, we found that protamine-2 and protamine ratio levels in the highest quartiles exhibited a decrease of 43.45% (95% CI: 60.54%, -19.75%) and an increase of 122.55% (95% CI: 60.00%, 209.57%) in Annexin V⁺/PI^- spermatozoa relative to the lowest quartiles, respectively. Mediation analysis revealed that protamine ratio significantly mediated 55.6% of the association between MEHP and Annexin V⁺/PI^- spermatozoa elevation (5.13%; 95% CI: 0.04%, 10.52%). Our findings provided evidence that human exposure to PAEs was associated with increased protamine levels which may mediate the process of spermatozoa apoptosis.

Urinary and seminal plasma concentrations of phthalate metabolites in relation to spermatogenesis-related miRNA106a among men from an infertility clinic

Studies indicate that phthalates can disrupt spermatogenesis and lead to the reduction of semen quality. However, the underlying mechanisms remain unclear. This study aimed to examine the associations of phthalate exposures as individual chemicals and mixtures with spermatogenesis-related miRNA106a. We detected eight phthalate metabolites in repeated urine samples and a single seminal plasma specimen among 111 men from an infertility clinic in Wuhan, China. Spermatogenesis-related miRNA106a was measured in seminal plasma. We used multivariable linear regression and Bayesian kernel machine regression (BKMR) models to separately evaluate the associations of phthalate metabolites as individual chemicals and mixtures with spermatogenesis-related miRNA106a. Elevated tertiles of urinary mono (2-ethylhexyl) phthalate (MEHP) was associated with decreased miRNA106a (-61.71%; 95%CI: 81.92, -18.93% for the highest vs. lowest tertile; P for trend = 0.01). Similarly, an inverse exposure-response relationship between seminal plasma MEHP concentrations and miRNA106a was also observed (-59.44%; 95%CI: 79.19, -20.95% for the highest vs. lowest tertile; P for trend = 0.01). The BKMR models showed that the mixtures of seminal plasma phthalate metabolites were associated with decreased miRNA106a when the chemical mixtures were ≥35th percentile compared to their medians. Nonlinear associations with miRNA106a were estimated for urinary and seminal plasma MEHP while fixing other phthalate metabolites at their medians. Our findings suggest that mixtures of phthalate metabolites in seminal plasma were negatively associated with spermatogenesis-related miRNA106a, and individual MEHP was the major contributor to the adverse effects.

Phthalate metabolites: Characterization, toxicities, global distribution, and exposure assessment

Phthalates are plasticizers in various products and regarded as endocrine disruptors due to their anti-androgen effects. Environmental occurrence and toxicities of parent phthalates have been widely reported, while the current state of knowledge on their metabolites is rarely summarized. Based on the available literature, the present review mainly aims to 1) characterize the potential metabolites of phthalates (mPAEs) using the pharmacokinetics evidences acquired via animal or human models; 2) examine the molecular and cellular mechanism involved in toxicity for mPAEs; 3) investigate the exposure levels of mPAEs in different human specimens (e.g., urine, blood, seminal fluid, breast milk, amniotic fluid and others) across the globe; 4) discuss the models and related parameters for phthalate exposure assessment. We suggest there is subtle difference in toxic mechanisms for mPAEs compared to their parent phthalates due to their alternative chemical structures. Human monitoring studies performed in Asia, America and Europe have provided the population exposure baseline levels for typical phthalates in different regions. Urine is the preferred matrix than other specimens for phthalate exposure study. Among ten urinary mPAEs, the largest proportions of di-(2-ethylhexyl) phthalate (DEHP) metabolites (40%), monoethyl phthalate (mEP) (43%) and DEHP metabolites/mEP (both 29%) were observed in Asia, America and Europe respectively, and mono-5-carboxy-2-ethypentyl phthalate was the most abundant compounds among DEHP metabolites. Daily intakes of phthalates can be accurately calculated via urinary mPAEs if the proper exposure parameters were determined. Further work should focus on combining epidemiological and biological evidences to establish links between phthalates exposure and biological phenotypes. More accurate molar fractions (F_UE) of the urinary excreted monoester related to the ingested diesters should be collected in epidemiological or pharmacokinetic studies for different population.

Legislation to limit the environmental plastic and microplastic pollution and their influence on human exposure

Plastic pollution is an emerging problem and is a consequence of the post-consumer plastic waste accumulation in the environment coupled to mismanaged waste programmes. Countries are counteracting the continuous growth of plastic litter with different strategies: introducing bans and limits on both plastic items and materials, promoting plastic recycling and recovery strategies and encouraging voluntary clean up actions, as well as raising public awareness. However, the toxicity of plastics to the environment and organisms is not only related to their polymer chains, but also to the fact that plastic materials contain hazardous additives and can adsorb environmental pollutants (i.e. heavy metals and persistent organic contaminants, respectively). The plastic/additives/pollutants combination may be ingested by marine organisms and then enter in the food chain. Therefore, legislation for additives and contaminants is crucial both to reduce environmental pollution and their toxic effects on organisms, which of course includes humans. In this review, the current policies on plastics and related contaminants are described focusing on current laws. Moreover, recommendations for seafood consumption are suggested, since each fish or mollusc eaten may potentially result in plastic particles, additives or contaminants ingestion.

Application of the comet assay for the evaluation of DNA damage in mature sperm

DNA integrity is considered an important parameter of semen quality and is of significant value as a predictor of male fertility. Currently, there are several methods that can assess sperm DNA integrity. One such assay is the comet assay, or single-cell gel electrophoresis, which is a simple, sensitive, reliable, quick and low-cost technique that is used for measuring DNA strand breaks and repair at the level of individual cells. Although the comet assay is usually performed with somatic cells from different organs, the assay has the ability to detect genotoxicity in germ cells at different stages of spermatogenesis. Since the ability of sperm to remove DNA damage differs between the stages, interpretation of the results is dependent on the cells used. In this paper we give an overview on the use and applications of the comet assay on mature sperm and its ability to detect sperm DNA damage in both animals and humans. Overall, it can be concluded that the presence in sperm of significantly damaged DNA, assessed by the comet assay, is related to male infertility and seems to reduce live births. Although there is some evidence that sperm DNA damage also has a long-term impact on offspring's health, this aspect of DNA damage in sperm is understudied and deserves further attention. In summary, the comet assay can be applied as a useful tool to study effects of genotoxic exposures on sperm DNA integrity in animals and humans.

Inverse association of certain seminal phthalate metabolites with semen quality may be mediated by androgen synthesis: A cross-sectional study from the South China

BACKGROUND

Several in vitro and in vivo studies have demonstrated the effects of phthalates on androgen synthesis, and the adverse outcomes of phthalate exposure on male reproductive function have been reported. However, the direct relationship among these three factors remains unknown.

OBJECTIVE

To explore the potential roles of steroids involved in androgen synthesis in the association between phthalate exposure and semen quality.

METHODS

Eighteen phthalate metabolites (mPAEs) and nine steroids were analyzed in semen samples of 403 male participants aged 18-54 years from a hospital in Shenzhen, China. The associations across phthalate metabolites, steroids, and eleven semen quality parameters were evaluated by multivariate linear regression and logistical regression models. The potential contributions of steroids to the associations between phthalate metabolites and semen quality outcomes were explored by mediation effect analysis.

RESULTS

In this cross-sectional study, mono-n-butyl phthalate (MnBP) was inversely associated with nine continuous semen quality parameters in a dose-dependent manner (all p for trend < 0.05). Positive associations were observed between MnBP tertiles and androstenedione (ADD) and pregnenolone (PGL), of which only ADD was significantly associated with sperm quality (i.e., motility, p < 0.05). The estimated average mediated effects of seminal ADD on the associations between MnBP and lower sperm motility parameters (i.e., total motility, TR; progressive motility, PR; curvi-linear velocity, VCL) were 6.4-11.9% (all p < 0.05). The potential mediated effects of ADD on the increasing risks of TR (9.8%) and PR (8.5%) abnormalities induced by MnBP exposure were also observed in logistical regression analysis.

CONCLUSION

Our results indicated that androgen synthesis in reproductive system may be potentially affected by phthalate exposure, thereby resulting in reduced sperm motility in adult men. Further studies are needed to understand the actual roles and underlying mechanism of action of androstenedione on these associations.

The effects of endocrine disruptors on the male germline: an intergenerational health risk

Environmental pollution is becoming one of the major concerns of society. Among the emerging contaminants, endocrine-disrupting chemicals (EDCs), a large group of toxicants, have been the subject of many scientific studies. Besides the capacity of these compounds to interfere with the endocrine system, they have also been reported to exert both genotoxic and epigenotoxic effects. Given that spermatogenesis is a coordinated process that requires the involvement of several steroid hormones and that entails deep changes in the chromatin, such as DNA compaction and epigenetic remodelling, it could be affected by male exposure to EDCs. A great deal of evidence highlights that these compounds have detrimental effects on male reproductive health, including alterations to sperm motility, sexual function, and gonad development. This review focuses on the consequences of paternal exposure to such chemicals for future generations, which still remain poorly known. Historically, spermatozoa have long been considered as mere vectors delivering the paternal haploid genome to the oocyte. Only recently have they been understood to harbour genetic and epigenetic information that plays a remarkable role during offspring early development and long-term health. This review examines the different modes of action by which the spermatozoa represent a key target for EDCs, and analyses the consequences of environmentally induced changes in sperm genetic and epigenetic information for subsequent generations.

Genotoxic risk assessment and mechanism of DNA damage induced by phthalates and their metabolites in human peripheral blood mononuclear cells

The human genome is persistently exposed to damage caused by xenobiotics, therefore the assessment of genotoxicity of substances having a direct contact with humans is of importance. Phthalates are commonly used in industrial applications. Widespread exposure to phthalates has been evidenced by their presence in human body fluids. We have assessed the genotoxic potential of selected phthalates and mechanism of their action in human peripheral blood mononuclear cells (PBMCs). Studied cells were incubated with di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP) and their metabolites: mono-n-butylphthalate (MBP), mono-benzylphthalate (MBzP) in the concentrations range of 0.1-10 µg/mL for 24 h. Analyzed compounds induced DNA single and double strand-breaks (DBP and BBP ≥ 0.5 µg/mL, MBP and MBzP ≥ 1 µg/mL) and more strongly oxidized purines than pyrimidines. None of the compounds examined was capable of creating adducts with DNA. All studied phthalates caused an increase of total ROS level, while hydroxyl radical was generated mostly by DBP and BBP. PBMCs exposed to DBP and BBP could not completely repair DNA strand-breaks during 120 min of postincubation, in opposite to damage caused by their metabolites, MBP and MBzP. We have concluded that parent phthalates: DBP and BBP caused more pronounced DNA damage compared to their metabolites.

Effects of the environmental endocrine disruptors di-2-ethylhexyl phthalate and mono-2-ethylhexyl phthalate on human sperm function in vitro

Di-2-ethylhexyl phthalate (DEHP), a plastic-derived, endocrine-disrupting chemical, has been shown to exhibit male reproductive toxicity. However, its effects on human mature spermatozoa are largely unknown. In this study we investigated the invitro effects of DEHP and mono-2-ethylhexyl phthalate (MEHP; the main metabolite of DEHP) on sperm function and the mechanisms involved. Human spermatozoa were exposed to phthalates invitro at the doses that cover the concentrations detected in human semen: 20nM-8 μM DEHP, 1nM-20 μM MEHP or a mixture of 20nM-8 μM DEHP and 1nM-20 μM MEHP. DEHP and MEHP, alone or in combination, had no effect on the viability, membrane integrity, motility, homeostasis of reactive oxygen species or mitochondrial activity of human spermatozoa. Interestingly, 1nM-20 μM MEHP and combinations of 20nM-8 μM DEHP and 1nM-20 μM MEHP enhanced penetration ability, hyperactivation and the spontaneous acrosome reaction of human spermatozoa, and increased intracellular free Ca2+ concentrations ([Ca2+]i) and tyrosine phosphorylation, two key signalling pathways that regulate sperm function. The findings of this study suggest that invitro exposure to MEHP metabolised from DEHP affects human sperm function by inducing increases in sperm [Ca2+]i and tyrosine phosphorylation, which adds to our understanding of the effects of DEHP on male reproduction.

Selective capturing and fluorescence “turn on” detection of dibutyl phthalate using a molecular imprinted nanocomposite

Fluorescence-based selective detection of dibutyl phthalate is achieved via a paper-strip-based approach.

Maternal preconception phthalate metabolite concentrations in follicular fluid and neonatal birth weight conceived by women undergoing in vitro fertilization

Exposure to phthalates during gestation has been associated with decreased birth weight among offspring. However, the associations between preconception phthalate metabolites in follicular fluid (FF) and offspring birth weight among women undergoing in vitro fertilization (IVF) remain largely unknown. Here, we explored the associations between preconception phthalate metabolite concentrations in FF and the birth weights of singletons and twins among women undergoing IVF. We recruited 147 female participants who gave birth to 90 singletons and 57 twin infants at the Reproductive Medicine Center, Tongji Hospital, Wuhan, between November and December 2016. Each participant was asked to complete a questionnaire at the time of recruitment and provide a FF sample on the day of oocyte retrieval. The FF concentrations of eight phthalate metabolites were determined using high-performance liquid chromatography and tandem mass spectrometry. Birth outcomes were abstracted from medical records. The associations between phthalate metabolites in FF and birth weights of the singleton and twin groups were evaluated using generalized linear models (GLMs). We found that birth weight in the twin group had negative dose-response associations with maternal preconception monobenzyl phthalate (MBzP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) in FF (both P for trends < 0.05) and that birth weight in the singleton group had positive dose-response associations with monoethyl phthalate (MEP) and mono(2-ethyl-5 hydroxyhexyl) phthalate (MEHHP) in FF (both P for trends < 0.05). These associations persisted when we modeled as continuous variables. In addition, we observed male-specific association between decreased twin birth weight and MEOHP and MBzP and a female-specific associations between increased singleton birth weight and MEP, MEHHP and the sum of di(2-ethylhexyl) phthalate (∑DEHP) (all P for interactions < 0.05). Preconception phthalate metabolites in maternal FF may affect the birth weights of both singleton and twin newborns.

Phthalate exposure and semen quality in infertile male population from Tianjin, China: Associations and potential mediation by reproductive hormones

Global decline in male fertility and their associations with ubiquitous exposure of phthalates (PAEs) have raised public concerns. However, the current epidemiological data are limited and controversial. Hence, we investigated possible associations between PAE exposure and male infertility. Eleven phthalate metabolites (mPAEs) were determined in urine and serum samples collected from eighty-eight males diagnosed with infertility from Tianjin, China. The median serum levels of mPAE were n.d. -3.63 ng/mL, which were 1-2 orders of magnitude lower than the urinary levels of n.d. -192 ng/mL. Negative associations were identified between urinary follicle-stimulating hormone (FSH) and MiBP and serum MCMHP, as well as testosterone (T) and luteinizing hormone (LH) and the molar concentrations of ∑mPAE, while positive association was found between T and the serum molar concentrations of ∑mDEHP. Positive associations were found between the molar concentrations of serum ∑mPAE and sperm concentration, sperm motility rate, and progressive motility, between mono (2-ethyl-5-carboxypentyl) phthalate (MECPP) and semen volume and total sperm number, and between MCMHP and progressive motility, while negative association was found between mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) and progressive motility. Moreover, FSH was found to mediate the association between serum concentrations of MCMHP and progressive motility (mediation ratio = 41.6%), and LH to mediate the associations between serum concentrations of ∑mPAE and sperm concentration (mediation ratio = 45.7%) and sperm motility rate (mediation ratio = 29.0%). These results also suggested that serum levels of mPAE are a good predictor for male infertility. Further efforts need to be made on toxicological studies to systematically elaborate the internal mechanisms.

Paternal programming of offspring health

In recent years, a new focus of the Developmental Origins of Health and Disease hypothesis has emerged examining the potential role that paternal health may play in embryo development, fetal growth and long-term offspring health. While the association between male health and sperm quality has been studied in detail, our understanding of the long-term paternal effects on offspring health remains limited. As with studies aimed at understanding maternal programming, animal models are an essential tool with which to define the underlying mechanisms linking paternal health to post-fertilisation development and offspring well-being. Here, new insights into the genetic and epigenetic nature of the sperm, as well as the role seminal plasma plays in modulating the maternal reproductive environment, are demonstrating the significant role a father's wellbeing at the time of conception has for programming the health of his offspring. In this article we will outline the current understanding of the impact of male health on semen quality, reproductive fitness and post-fertilisation offspring development and explore the mechanisms underlying the paternal programming of offspring health.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the simultaneous determination of phthalates and bisphenol a in serum, urine and follicular fluid

Phthalates and bisphenol A interfere with the synthesis, secretion, transport, binding, metabolism, and excretion of endogenous hormones and, for this reason, are classified as endocrine disruptors. We are here presenting an analytical method for the simultaneous detection of six phthalates metabolites and bisphenol A in different biological fluids (urine, serum and follifular fluid) by liquid chromatography coupled to tandem mass spectrometry. The quantification was carried out in negative electrospray ionization mode using selected reaction monitoring as acquisition mode. Different extraction protocols, using either solid phase or liquid/liquid extraction, were comparatively evaluated to optimize the sample preparation procedure. Solid-phase extraction was chosen as it ensured the best recovery and overall sensitivity. The method was successfully validated: recovery varying in the range 71 ± 2%-107 ± 6% depending on the target analyte and the matrix considered, intra-assay and inter-assay precision ≤ 12% for follicular fluid, ≤11% for serum and ≤ 10% for urine and accuracy ≤ 115% for follicular fluid, ≤113% for serum ≤ 115% for urine , linearity with R2 > 0.99, with the exception of MEP (recovery 64 ± 8%, intra-assay precision ≤ 20%, inter-assay precision ≤ 16% for follicular fluid). The actual applicability of the method developed and validated in this study was assessed by the analysis of real samples, including 10 specimens of follicular fluid, serum and urine samples, that showed the presence of phthalates metabolites and Bisphenol A, and confirming that the newly developed method can be applied in the routine clinical laboratory for the identification and quantitation of these endocrine-disrupting chemicals.

Effect of different glycerol concentrations on phosphatidylserine translocation and mitochondrial membrane potential in chilled boar spermatozoa

Boar spermatozoa are extremely sensitive to low temperatures and the cryopreservation causes dramatic changes in sperm survivability, but it is not clear which part of the cryopreservation process affects the most. The aim of this work was to assess early events of apoptotic changes as damage indicators in boar sperm cooled to 5 °C and exposed to different glycerol (GLY) concentrations. For this purpose, progressive sperm motility (CASA), plasmatic and acrosome membranes integrity (CFDA/PI; phase contrast), plasma membrane functionality (HOS), phosphatidylserine translocation (Annexin-V/FITC) and reduction of mitochondrial membrane potential (Ψm) (JC-10) were carried out at 37 °C, 17 °C and 5 °C in eight boar sperm pools. Afterwards, three aliquots were diluted in different freezing extenders (control: 0% GLY; A: 2% GLY and B: 3% GLY); sperm quality and early apoptotic changes were assessed. Motility was negatively affected during cooling to 5 °C. Furthermore, plasma membrane functionality was the most affected by cooling. The number of necrotic cells was higher at 5 °C. However, no differences were observed in phosphatidylserine translocation. The extender with 3% GLY at 5 °C presented better Ψm than 0 and 2% GLY. Based on this analysis, boar sperm cooling to 5 °C does not modify the rate of early apoptotic changes, although alterations in the Ѱm were evident.

Endocrine Disruptors in Water and Their Effects on the Reproductive System

Anthropogenic contaminants in water can impose risks to reproductive health. Most of these compounds are known to be endocrine disrupting chemicals (EDCs). EDCs can impact the endocrine system and subsequently impair the development and fertility of non-human animals and humans. The source of chemical contamination in water is diverse, originating from byproducts formed during water disinfection processes, release from industry and livestock activity, or therapeutic drugs released into sewage. This review discusses the occurrence of EDCs in water such as disinfection byproducts, fluorinated compounds, bisphenol A, phthalates, pesticides, and estrogens, and it outlines their adverse reproductive effects in non-human animals and humans.

Mediation of association between polycyclic aromatic hydrocarbon exposure and semen quality by spermatogenesis-related microRNAs: A pilot study in an infertility clinic

Spermatogenesis-related microRNAs (miRNAs) are vulnerable to polycyclic aromatic hydrocarbons (PAHs). Changes in spermatogenesis-related miRNAs may be biological intermedia in mechanisms linking PAHs and semen quality. This study aimed to investigate whether spermatogenesis-related microRNAs mediate the associations between PAHs and semen quality. We measured 10 monohydroxylated PAHs (OH-PAHs) in repeated urine samples and three candidate spermatogenesis-related miRNAs (miRNA106a, miRNA21, and miRNA34c) in seminal plasma from men attending an infertility clinic (n = 111). Mediation analysis was applied to determine the mediating role of spermatogenesis-related miRNAs in the association of PAH exposure with semen quality. Urinary 2-OHFlu and 2-OHPh were related to reduced seminal plasma miRNA34c (p for trend = 0.05 and 0.03, respectively). Urinary 9-OHPh was related to reduced seminal plasma miR106a (p for trend = 0.02), which in turn, was positively associated with sperm concentration, sperm count, sperm total motility, and progressive motility (all p for trends<0.05). Up to 43.8% of the eff ;ect of urinary 9-OHPh on decreased sperm concentration was mediated by seminal plasma miR106a. Our results suggested that certain PAH exposure was associated with reduced spermatogenesis-related miRNAs and such alterations might be an intermediate mechanism by which PAHs exert its adverse effects on semen quality.

The associations of urinary phthalate metabolites with the intermediate and pregnancy outcomes of women receiving IVF/ICSI treatments: A prospective single-center study

BACKGROUND

Phthalate exposure was reported to induce defects in ovarian function, and further influence embryo development and pregnancy outcomes. However, the data about the associations of phthalates with intermediate and pregnancy outcomes of in vitro fertilization (IVF) cycles are scarce in the Chinese population.

METHODS

A total of 663 women receiving IVF/intracytoplasmic sperm injection (ICSI) treatments in our center were enrolled in this analysis. They provided one urine sample on the day of oocyte retrieval. We measured urinary concentrations of eight phthalate metabolites. Generalized linear models were used to analyze the associations of urinary phthalate metabolites with ovarian response, fertilization, early embryo development, and pregnancy outcomes.

RESULTS

Among all the phthalate metabolites, mono-n-butyl phthalate (MBP) had the highest urinary concentration with a median level of 101.51 μg/g creatinine (Cr). MBP concentration was inversely associated with normal fertilization odds (overall P-trend < 0.01). There was a significant correlation of monoethyl phthalate (MEP) with decreased odds of normal fertilization in medium-concentration group compared to low-concentration group (overall P-trend = 0.02). No significant associations of metabolite concentrations with the odds of good-quality embryos on day 3 or blastocyst formation were found. Monomethyl phthalate (MMP) and MEP in medium-concentration group reduced 22.4% (95% CI: 0.64-0.94, overall P-trend = 0.04) and 21.9% (95% CI: 0.64-0.95, overall P-trend = 0.05) of the odds to gain good-quality blastocyst compared to low-concentration group. The eight phthalate metabolites were not correlated to clinical pregnancy rate, live birth rate, or early miscarriage rate. There was no significant association of di (2-ethylhexyl) phthalate (DEHP) metabolites observed with any clinical outcomes in the total population. After excluding male infertility, mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) in medium-concentration group turned to be associated with a higher number of retrieved oocytes (overall P-trend = 0.04), whereas mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) in medium-concentration group was associated with a lower odds of normal fertilization compared to low-concentration group (overall P-trend = 0.02).

CONCLUSIONS

Urinary MBP concentration was much higher compared to other phthalate metabolites in this cohort of Chinese IVF/ICSI women, and also higher than it was reported by studies in other countries. MBP showed adverse impacts on fertilization. MMP and MEP could affect blastocyst quality, but not embryo quality on day 3. DEHP metabolites didn't show consistent reproductive toxicities as demonstrated in previous studies.

Urinary levels of phthalate metabolites and their association with lifestyle behaviors in Chinese adolescents and young adults

BACKGROUND

Adolescence and young adulthood are critical periods of human growth and development. Phthalates are environmental endocrine disruptors, and their health hazards in adolescents and young adults cannot be ignored. This study was undertaken to assess phthalate exposure and determine the associations between lifestyle behaviors and phthalate metabolite levels in Chinese adolescents and young adults.

METHODS

Four hundred and seventy-eight adolescents and young adults aged 16-20 years were included in this study. The levels of mono-ethyl phthalate (MEP), mono-butyl phthalate (MBP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) and mono-(2-carboxmethyl)-hexyl phthalate (MCMHP) in the subjects' urine were measured by high-performance liquid chromatography-tandem mass spectrometry. The estimated daily intake (EDI) and hazard index (HI) of phthalates were calculated based on urinary metabolite levels. Relevant information on the subjects was collected via questionnaires. The associations between phthalate metabolite levels and lifestyle behaviors were examined using the independent-sample t-test, Mann-Whitney test and multiple linear regression.

RESULTS

In this study, the detection rates of all seven metabolites were >98%. The highest median metabolite concentration was MBP, which was 43.00 μg/L (33.11 μg/g creatinine). The highest median EDI was for di-(2-ethylhexyl) phthalate (DEHP), which was 2.40 μg/kg-bw/day (volume-based) and 1.51 μg/kg-bw/day (creatinine-based). 2.7% (volume-based) and 1.0% (creatinine-based) of the subjects showed excessive HI_TDI (HI of the tolerable daily intake) values, which indicated the cumulative risk of anti-androgenic effects. Furthermore, factors significantly associated with phthalate metabolite levels included the use of plastic food packages (DEHP metabolites), physical exercise (MEOHP), the frequency of fast food consumption (MBP), and the frequency of skin care cosmetics and color cosmetics use (MEP).

CONCLUSION

Our results suggest that Chinese adolescents and young adults are widely exposed to phthalates and their metabolite levels are influenced by lifestyle behaviors.

Contribution of phthalates and phthalate monoesters from drinking water to daily intakes for the general population

Although phthalates (PAEs) are ubiquitous in drinking water, and phthalate monoesters (MPAEs) have been recognized as the bioactive metabolites of PAEs, little information is available regarding the occurrence of MPAEs in drinking water and the contributions of PAEs and MPAEs to human exposure. In this study, the concentrations of PAEs and MPAEs in 146 samples of drinking water collected from 24 cities throughout China were determined. The mean concentrations of dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and di-2-ethylhexyl phthalate (DEHP) were 14.31 ± 26.28, 5.905 ± 11.57, 103.8 ± 310.5, 595.9 ± 1794, and 178.2 ± 422.0 ng/L, respectively. Monomethyl phthalate (MMP), monoethyl phthalate (MEP), monoisobutyl phthalate (MiBP), mono-n-butyl phthalate (MnBP), and mono-2-ethylhexyl phthalate (MEHP) were detected in drinking water for the first time, at mean concentrations of 12.1 ± 18.0, 2.4 ± 5.8, 11.3 ± 37.2, 36.3 ± 103, and 9.9 ± 18.0 ng/L, respectively. The geometric mean concentrations of MMP, MEP, MiBP, MnBP, and MEHP in urine samples collected from 1040 participants from 16 cities were 10.1, 19.3, 29.6, 47.3, and 3.63 μg/g creatinine, respectively. The concentrations of PAEs and MPAEs in drinking water and daily intakes (DIs) of PAEs from nine cities where drinking water and urine samples were simultaneously collected were used to estimate the contributions from drinking water. The percentages of DMP, DEP, DiBP, DnBP, and DEHP from drinking water accounted for DIs of 0.60%, 0.049%, 1.26%, 2.76%, and 0.56%, respectively. The percentages of MMP, MEP, MiBP, MnBP and MEHP via intake of drinking water accounted for urinary concentrations of 0.86%, 0.032%, 0.14%, 0.089%, and 0.045%, respectively.

Phthalates in residential and agricultural soils from an electronic waste-polluted region in South China: distribution, compositional profile and sources

Electronic waste (e-waste) recycling has proven to be a significant source of phthalate (PAE) contamination in the environment. A detailed investigation was conducted to understand the concentration, distribution, profile and possible source of PAEs in residential and agricultural soils from Guiyu, Shantou, China, the largest e-waste processing and recycling areas in the world. Sixteen PAEs were analysed in 46 surface soil samples from three different sampling areas in terms of individual and total concentrations, together with pH and soil organic matter. High concentrations of the total PAEs were found in residential area A (more than 20,000 ng g^-1), revealing a clear urban pulse, whereas in residential area B and agricultural areas, concentrations were lower than 10,000 ng g^-1. The dominant PAEs were bis (2-nbutoxyethyl) phthalate, bis (4-methyl-2-pentyl) phthalate and dicyclohexyl phthalate. These PAEs were high-molecular weight PAEs (alkyl chains ≥ 6 carbons) and mainly derived from polyvinyl chloride commonly used in electrical and electronic equipment, indicating a distinctive composition in relation to the e-waste area. Three individual and the total PAEs exhibited significant positive correlations with pH. Principal component analysis indicated that PAEs were mainly distributed in three groups according to the alkyl chain length and potential source. This study showed that the informal e-waste recycling has already introduced PAEs into surrounding areas as a pollutant which should draw more attention and regulatory control.

Phthalate exposure and male reproductive outcomes: A systematic review of the human epidemiological evidence

OBJECTIVE

We performed a systematic review of the epidemiology literature to identify the male reproductive effects associated with phthalate exposure.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

Six phthalates were included in the review: di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP). The initial literature search (of PubMed, Web of Science, and Toxline) included all studies of male reproductive effects in humans, and outcomes were selected for full systematic review based on data availability.

STUDY EVALUATION AND SYNTHESIS METHODS

For each outcome, studies were evaluated using criteria defined a priori for risk of bias and sensitivity by two reviewers using a domain-based approach. Evidence was synthesized by outcome and phthalate and strength of evidence was summarized using a structured framework.

RESULTS

The primary outcomes reviewed here are (number of included/excluded studies in parentheses): anogenital distance (6/1), semen parameters (15/9), time to pregnancy (3/5), testosterone (13/8), timing of pubertal development (5/15), and hypospadias/cryptorchidism (4/10). Looking at the overall hazard, there was robust evidence of an association between DEHP and DBP exposure and male reproductive outcomes; this was based primarily on studies of anogenital distance, semen parameters, and testosterone for DEHP and semen parameters and time to pregnancy for DBP. There was moderate evidence of an association between DINP and BBP exposure and male reproductive outcomes based on testosterone and semen parameters for DINP and semen parameters and time to pregnancy for BBP. DIBP and DEP were considered to have slight evidence of an association. For DIBP, the less conclusive evidence was attributed to a more limited literature base (i.e., fewer studies) and lower exposure levels in the population, decreasing the ability to observe an effect. For DEP, the findings were consistent with experimental animal data that suggest DEP does not haves as strong an anti-androgenic effect as other phthalates.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Overall, despite some inconsistencies across phthalates in the specific outcomes associated with exposure, these results support that phthalate exposure at levels seen in human populations may have male reproductive effects, particularly DEHP and DBP. The relative strength of the evidence reflects differing levels of toxicity as well as differences in the range of exposures studied and the number of available studies. The views expressed are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Preconception seminal plasma concentrations of endocrine disrupting chemicals in relation to semen quality parameters among male partners planning for pregnancy

BACKGROUND

Some non-persistent endocrine disruptors (EDCs) are adversely associated with semen quality and few studies have measured those EDCs in seminal plasma.

OBJECTIVE

To find an association between EDCs in seminal plasma and semen quality parameters.

METHODS

Five chemical classes of non-persistent EDCs were quantified in seminal plasma from 339 male partners who participated in a prospective pregnancy study. Bisphenols, benzophenone UV-filters, antimicrobials and phthalate diesters and their monoester metabolites were measured using high performance liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. Semen samples underwent next day analysis using a standardized protocol for the quantification of 35 endpoints. Linear mixed-effects models of EDCs that were log transformed and rescaled by their standard deviations or dichotomized at the 75th percentile for each exposure and outcomes with covariate adjustment were performed. EDCs in seminal plasma were also assessed relative to clinical reference values of semen quality endpoints using logistic regression or generalized estimating equations.

RESULTS

The most consistent findings supporting adverse associations between seminal EDCs and semen quality were observed for some phthalate metabolites. For example, seminal plasma mono-ethyl, mono-n-butyl, mono-2-isobutyl and mono-benzyl phthalate concentrations were associated with decreased odds of having semen volume above clinical reference values (mEP: aOR=0.46; 95%CI= 0.32, 0.66; mBP: aOR=0.40; 95%CI= 0.28, 0.57; miBP: aOR=0.39; 95%CI= 0.27, 0.56), and mBzP: aOR= 0.34; 95%CI= 0.24, 0.49).

CONCLUSIONS

Environmentally relevant concentrations of specific phthalates in seminal plasma were associated with diminished semen volume, sperm motility, viability, and morphological alterations in sperm heads such that semen volume and sperm viability fall below reference values.

Disruption of ergosterol and tryptophan biosynthesis, as well as cell wall integrity pathway and the intracellular pH homeostasis, lead to mono-(2-ethylhexyl)-phthalate toxicity in budding yeast

Endocrine disrupting chemicals (EDCs) are substances in the environment, food, and consumer products that interfere with hormone homeostasis, metabolism or reproduction in humans and animals. One such EDC, the plasticizer di-(2-ethylhexyl)-phthalate (DEHP), exerts its function through its principal bioactive metabolite, mono-(2-ethylhexyl)-phthalate (MEHP). To fully understand the effects of MEHP on cellular processes and metabolism as well as to assess the impact of genetic alteration on the susceptibility to MEHP-induced toxicity, we screened MEHP-sensitive mutations on a genome-scale in the eukaryotic model organism Saccharomyces cerevisiae. We identified a total of 96 chemical-genetic interactions between MEHP and gene mutations in this study. In response to MEHP treatment, most of these gene mutants accumulated higher intracellular MEHP content, which correlated with their MEHP sensitivity. Twenty-seven of these genes are involved in the metabolism, twenty-two of them play roles in protein sorting, and ten of them regulate ion homeostasis. Functional categorization of these genes indicated that the biosynthetic pathways of both ergosterol and tryptophan, as well as cell wall integrity and the intracellular pH homeostasis, were involved in the protective response of yeast cells to the MEHP toxicity. Our study demonstrated that a collection of yeast gene deletion mutants is useful for a functional toxicogenomic analysis of EDCs, which could provide important clues to the effects of EDCs on higher eukaryotic organisms.

Thyroid function, phthalate exposure and semen quality: Exploring associations and mediation effects in reproductive-aged men

BACKGROUND

A normal thyroid physiology is crucial for the maintenance of male reproductive health. Changes in thyroid hormones may represent an intermediate biological mechanism linking phthalate exposure and potential adverse health effects on male reproduction.

OBJECTIVE

To investigate the mediating role of thyroid function on the association between phthalate exposure and semen quality.

METHOD

Serum thyroid hormones, semen quality and repeated measures of urinary phthalate metabolites were determined among 509 reproductive-aged men in Wuhan, China. Cross-sectional associations between urinary phthalate metabolites, serum thyroid hormones and semen quality were explored using multivariable linear regressions. A mediation analysis was conducted to explore the role of thyroid function on the association of phthalate exposure with semen quality.

RESULTS

Significant dose-dependent relationships were found across quartiles of monoethyl phthalate (MEP) with decreasing serum free thyroxine (FT4), which, in turn, was negatively associated with percentage of normal morphology (p for trend = 0.04). Also, we found that the proportions of di-(2-ethylhexyl)-phthalate metabolites excreted as mono-(2-ethylhexyl) phthalate (%MEHP) were negatively associated with serum thyroid-stimulating hormone (TSH) (all p for trends <0.05), which, in turn, was positively associated with progressive and total sperm motility (p for trends = 0.04 and 0.03, respectively). The mediation analysis indicated that higher urinary MEP was significantly associated with a decreasing percentage of normal morphology after controlling for thyroid hormones, and 17% of the association was mediated by serum FT4.

CONCLUSIONS

Higher urinary MEP and %MEHP were associated with decreasing serum thyroid hormones, which in turn were associated with altered semen quality. Mediation analysis indicated that serum FT4 was a possible mediator of the association between urinary MEP and proportion of normal sperm morphology.

Simultaneous determination of primary and secondary phthalate monoesters in the Taihu Lake: Exploration of sources

While phthalates monoesters have been recognized as the bioactive metabolites of phthalates, the knowledge on their environmental occurrence and sources is limited. In this study, monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-iso-butyl phthalate (MiBP), mono-n-butyl phthalate (MnBP), and mono-2-ethylhexyl phthalate (MEHP) were frequently detected in water samples from the Taihu Lake in China using an improved SPE-LC-MS-MS method. The mean concentrations for MMP, MEP, MiBP, MnBP, and MEHP were 51.7 ± 25.2, 6.0 ± 4.8, 19.6 ± 14.6, 42.2 ± 64.7, and 33.0 ± 37.4 ng/L, respectively, while those of their corresponding parent chemicals, DMP, DEP, DiBP, and DnBP and DEHP, were 36.54 ± 43.22, 42.64 ± 66.66, 246.8 ± 311.1, 524.7 ± 586.9, and 208.1 ± 223.5 ng/L, respectively. Three secondary monoesters of DEHP, mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono (2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono (2-ethyl-5-carboxypentyl) phthalate (MECPP) were for the first time detected with mean concentration of 1.27 ± 1.33, 1.33 ± 1.54, and 0.73 ± 0.79 ng/L, respectively. The percentage of the sum concentration of MEOHP, MEHHP, and MECPP relative to total concentration of DEHP metabolites was 5.3-12.4%. DEHP was identified to be biodegraded into secondary phthalate monoesters in water from the Taihu Lake, but their contribution to the total concentration of DEHP metabolites was 1.2-3.6%, lower than those in the Taihu Lake. Primary and secondary DEHP monoesters were also detected in influents and effluents of two sewage treatment plants adjacent to the Taihu Lake, the percentages of secondary DEHP monoesters in influents were 5.8% and 11.3%, similar with those in the Taihu Lake. Taken together with their relatively high concentrations in influents, the discharging of domestic wastewater may be an important contributor to the occurrence of phthalate monoesters in the Taihu Lake.

Preconception urinary phthalate concentrations and sperm DNA methylation profiles among men undergoing IVF treatment: a cross-sectional study

STUDY QUESTION

Are preconception phthalate and phthalate replacements associated with sperm differentially methylated regions (DMRs) among men undergoing IVF?

SUMMARY ANSWER

Ten phthalate metabolites were associated with 131 sperm DMRs that were enriched in genes related to growth and development, cell movement and cytoskeleton structure.

WHAT IS KNOWN ALREADY

Several phthalate compounds and their metabolites are known endocrine disrupting compounds and are pervasive environmental contaminants. Rodent studies report that prenatal phthalate exposures induce sperm DMRs, but the influence of preconception phthalate exposure on sperm DNA methylation in humans is unknown.

STUDY DESIGN, SIZE, DURATION

An exploratory cross-sectional study with 48 male participants from the Sperm Environmental Epigenetics and Development Study (SEEDS).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The first 48 couples provided a spot urine sample on the same day as semen sample procurement. Sperm DNA methylation was assessed with the HumanMethylation 450 K array. Seventeen urinary phthalate and 1,2-Cyclohexane dicarboxylic acid diisononyl ester (DINCH) metabolite concentrations were measured from spot urine samples. The A-clust algorithm was employed to identify co-regulated regions. DMRs associated with urinary metabolite concentrations were identified via linear models, corrected for false discovery rate (FDR).

MAIN RESULTS AND ROLE OF CHANCE

Adjusting for age, BMI, and current smoking, 131 DMRs were associated with at least one urinary metabolite. Most sperm DMRs were associated with anti-androgenic metabolites, including mono(2-ethylhexyl) phthalate (MEHP, n = 83), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP, n = 16), mono-n-butyl phthalate (MBP, n = 22) and cyclohexane-1,2-dicarboxylic acid-monocarboxy isooctyl (MCOCH, n = 7). The DMRs were enriched in lincRNAs as well as in regions near coding regions. Functional analyses of DMRs revealed enrichment of genes related to growth and development as well as cellular function and maintenance. Finally, 13% of sperm DMRs were inversely associated with high quality blastocyst-stage embryos after IVF.

LIMITATIONS, REASONS FOR CAUTION

Our modest sample size only included 48 males and additional larger studies are necessary to confirm our observed results. Non-differential misclassification of exposure is also a concern given the single spot urine collection.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first study to report that preconception urinary phthalate metabolite concentrations are associated with sperm DNA methylation in humans. These results suggest that paternal adult environmental conditions may influence epigenetic reprogramming during spermatogenesis, and in turn, influence early-life development.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grant K22-ES023085 from the National Institute of Environmental Health Sciences. The authors declare no competing interests.

Phthalate exposure and high blood pressure in adults: a cross-sectional study in China

Widespread phthalate exposure has been recently documented and is hypothesized to increase blood pressure (BP) in humans. However, current studies have provided inconclusive evidence for an association between phthalate exposure and BP. Human epidemiologic studies on the topic remain lacking. Therefore, this study aims to examine the association between serum phthalate concentrations and BP in a Chinese population. We measured several parameters of BP (systolic BP, diastolic BP, total cholesterol, and triglyceride) and the concentrations of 16 phthalates (dimethyl phthalate (DMP), diethyl phthalate, diisobutyl phthalate, dibutyl phthalate (DBP), bis (2-methoxyethyl) phthalate, bis (4-methyl-2-pentyl) phthalate, bis (2-ethoxyethyl) phthalate, diamyl phthalate, dihexyl phthalate, benzyl butyl phthalate, bis (2-nbutoxyethyl) phthalate (DBEP), dicyclohexyl phthalate, bis (2-ethyl hexyl) phthalate (DEHP), diisononyl phthalate, diphenyl phthalate, and di-n-octyl phthalate) in the serum of 474 adults recruited from a primary health care clinic. The relationship between serum phthalate concentrations and BP parameters was assessed with multivariate linear regressions. DBP was the most ubiquitous and dominant contaminant in the study population. The systolic BP of subjects in the median-exposure DEHP group significantly increased by 2.96 mmHg (p < 0.05) relative to that of subjects in the low-exposure group. Significant positive dose-related associations of DMP and DBEP with the levels of total cholesterol in serum (p for trend < 0.05) were also found. These associations persisted even when considering exposure to multiple phthalates. Our results suggested that phthalate exposure might increase BP in adults. However, our findings warrant further studies in a larger and more general population.

Association between use of phthalate-containing medication and semen quality among men in couples referred for assisted reproduction

STUDY QUESTION

Does phthalate exposure from prescription drugs affect semen quality?

SUMMARY ANSWER

Exposure to phthalate-containing drugs is associated with poor semen quality.

WHAT IS KNOWN ALREADY

Phthalates and their metabolites have been shown to disrupt the hormone signalling in animal studies. One study has shown associations between medicinal phthalate exposure and poor semen quality, suggesting similar effects in humans.

STUDY DESIGN, SIZE, DURATION

We included 18 515 males with poor semen quality (cases) and 31 063 males with normal semen quality (controls) registered in the Danish IVF Registry from 2006 to 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Exposure to phthalate-containing drugs was assessed from the Danish Register of Medicinal Product Statistics. Outcome measures were obtained at the first contact with the fertility clinic, and categorized according to the International Classification of Diseases (ICD-10). The association between current use of phthalate-containing medications <90 days prior to semen sampling and reduced semen quality was analysed using unconditional logistic regression, adjusting for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 57 cases and 72 controls redeemed at least one prescription for a drug containing ortho-phthalates in the 90 days before their first semen sample, yielding an adjusted odds ratio (OR) of 1.30 (95% CI: 0.91-1.85) for poor semen quality when compared to males exposed to phthalate-free generic drugs. Similarly, 81 cases and 78 controls exposed to a drug containing polymers had increased odds of poor semen quality (OR = 1.71, 95% CI: 1.24-2.35). Current exposure to polymer containing products from alimentary tract and metabolism drugs was associated with the highest OR of 2.80 (95% CI: 1.63-4.84). Comparing males exposed to drugs containing ortho-phthalates or polymers with males unexposed to prescription drugs, we found adjusted ORs of 1.32 (95% CI: 0.93-1.87) and 1.73 (95% CI: 1.26-2.36), respectively. We saw no clear relationship between degree of exposure and odds of poor semen quality.

LIMITATIONS, REASONS FOR CAUTION

The reliance on ICD-10 based register data restricted our ability to relate phthalate exposure to detailed semen parameters. Furthermore, due to imperfections in the registry, we could only include the first semen sample and could not follow semen quality over time.

WIDER IMPLICATIONS OF THE FINDINGS

Our results support the likely negative effect of phthalate exposure from medicinal drugs on semen quality. As exposures from medicinal products are readily avoidable, our findings may be of relevance to regulatory authorities.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Odense University Hospital, Denmark (Grant number A1003). None of the authors declare conflict of interest.

Predictors and correlations of phthalate metabolite concentrations in urine and seminal plasma among reproductive-aged men

BACKGROUND

Certain phthalates are suspected to be endocrine disruptors that are adversely associated with male reproductive health. However, the predictors and correlations of phthalate metabolite concentrations in urine and seminal plasma among reproductive-aged men have not been thoroughly studied.

OBJECTIVE

To investigate the predictors and correlations of phthalate metabolite concentrations in urine and seminal plasma among adult Chinese males.

METHOD

We measured mono-n-butyl phthalate (MBP), monobenzyl phthalate (MBzP), monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-octyl phthalate (MOP), mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) concentrations in seminal plasma and repeated spot-urine samples from 687 men who visited a reproductive center. Mixed-effect models were used to examine the associations of sociodemographic, lifestyle and medical factors with urinary metabolite concentrations. Linear regression models were used to identify predictors of metabolite concentrations in seminal plasma and correlations between metabolite concentrations in spot urine samples and seminal plasma.

RESULTS

Measurements taken from spot urine samples poorly predicted same-day seminal plasma concentrations (all R²<0.10). Inverse associations were observed between education level and urinary MBP and MEOHP and between household income and urinary MMP; receiving intravenous infusion therapy was associated with increased urinary MBP, MEHHP and MEOHP, use of facial cleanser/cream was associated with increased MEP, and smoking was associated with increased MEHP. The predictors of metabolite concentrations in seminal plasma differed from those in urine, except for the association of intravenous infusion therapy with MBP. BMI was associated with increased seminal plasma MBP, MEHP and MEOHP, smoking was associated with increased MEP, and contact with plastics was associated with increased MEOHP.

CONCLUSIONS

Phthalate metabolite concentrations in adult men varied in accordance with sociodemographic variables, lifestyle factors and intravenous therapy. Measures of metabolite levels in urine may not directly reflect the exposure status of the male reproductive system.

Effect modification by apoptosis-related gene polymorphisms on the associations of phthalate exposure with spermatozoa apoptosis and semen quality

BACKGROUND

Human studies indicate that phthalate exposure is associated with adverse male reproductive health, and this association may be modified by genetic polymorphisms.

OBJECTIVES

We investigated whether apoptosis-related gene polymorphisms modified the associations of phthalate exposure with spermatozoa apoptosis and semen quality.

METHODS

In this Chinese population who sought for semen examination in an infertility clinic, we measured 8 phthalate metabolites in two urine samples to assess the individual's exposure levels. Apoptosis-related gene (Fas, FasL, and caspase3) polymorphisms were performed by real-time PCR. Spermatozoa apoptosis and semen quality parameters were evaluated by Annexin V/PI assay and computer-aided semen analysis, respectively.

RESULTS

We found that Fas rs2234767, FasL rs763110, and caspase3 rs12108497 gene polymorphisms significantly modified the associations between urinary phthalate metabolites and spermatozoa apoptosis. For example, urinary monobutyl phthalate (MBP) associated with an increased percentage of Annexin V⁺/PI^- spermatozoa of 25.11% (95% CI: 4.08%, 50.53%) were only observed among men with CT/TT genotype of FasL rs763110. In addition, we found that caspase3 rs12108497 gene polymorphisms significantly modified the associations of urinary mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) with decreased sperm concentration and sperm count (both p-values for interactions = 0.02).

CONCLUSION

Our results provided the first evidence that apoptosis-related gene polymorphisms might contribute to the effects of phthalate exposure on male reproductive health.