Reproductive and developmental toxicity of phthalates

Di-(2-ethylhexyl) Phthalate (DEHP) and Uterine Histological Characteristics

Phthalates have a long industrial history. It is suspected that phthalates and their metabolites have detrimental effects on reproduction and development. They are well-known for their anti-androgenic effects. Several studies have indicated that phthalates and their metabolites are reprotoxic in males and endocrine disruptors. Reproduction and embryogenesis occur in the uterus of female eutherian mammals. A horizontal analytical method is preferred to elucidate the toxic effects of phthalates on human reproduction. Nevertheless, there are vast numbers of known phthalates and not all of their modes of action have been clarified. Di-(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer and has been the subject of numerous toxicological studies. However, few of these have reported on the toxic effects of DEHP, its metabolites, other phthalates, or mixtures on female reproduction. Acute and high doses of DEHP adversely affect uterine histology. Recently, it was disclosed that chronic exposures to low doses of DEHP have endocrine disruption efficacy. DEHP induces various cellular responses including modulation of the expression and regulation of steroid hormone receptors and transcription and paracrine factors. Uteri do not respond uniformly to DEHP exposure. The phenotypic manifestations and effects on fertility in response to DEHP and its metabolites may vary with species, developmental stage, and generation. Hence, DEHP exposure may histological alter the uterus and induce endometriosis, endometriosis, hyperplasia, myoma, and developmental and reproductive toxicity.

Neurological effects of subchronic exposure to dioctyl phthalate (DOP), lead, and arsenic, individual and mixtures, in immature mice

Dioctyl phthalate (DOP) (200, 500, and 1000 mg kg^-1 bw, i.g.), Pb (Ac)₂ (50 mg L^-1, p.o.), and NaAsO₂ (10 mg L^-1, p.o.) were administered individually and as mixtures to weanling male mice for 8 weeks. It was observed that Pb, As, and DOP exposure could significantly inhibit the growth and development of mice. Compared with the Pb, As, and Pb + As groups, the activities of iNOS and TNOS were significantly increased, the levels of AChE and SOD were significantly decreased, and the level of MDA was significantly increased in the Pb + DOP-H, As + DOP-H, and Pb + As + DOP-H groups. The factorial analysis shows that the iNOS, TNOS, and AChE present synergistic effects on Pb, As, and DOP. A significant increase of escape latency and a significant decrease of original platform quadrant stops were observed between Pb + As + DOP-H and Pb + As groups. The factorial analysis shows that there was a synergistic effect on Pb, As, and DOP. Compared with that of the control group, the expression levels of caspase-3 and Bax expression in Pb + As, DOP-H, Pb + DOP-H, As + DOP-H, and Pb + As + DOP-H groups were significantly increased in the hippocampus. The expression levels of Bcl-2 expression decreased significantly and the Bax/Bcl-2 ratio increased significantly. Pathological alterations on the hippocampus were found in exposed groups. This result shows that combined exposure of Pb, As, and DOP could induce neurotoxicity, of which possible mechanism is hippocampal neuronal apoptosis. Graphical abstract This study shows that there were three components with eigenvalues greater than 1, which together explained 89.40% of total variance. The first component (PC1) showed high loadings on B-SOD, L-SOD, B-MDA, L-MDA, K-MDA, iNOS, tNOS, and AChE and accounted for 46.55% of the total variance after Varimax rotation. PC2 accounted for 23.81% of the total variance with high loadings on B-As, L-As, K-As, and K-SOD, whereas PC3 showed high loadings on B-Pb, L-Pb, and K-Pb and accounted for 19.04% of the total variance.

Effect of DEHP on SCFA Production by Anaerobic Fermentation of Waste Activated Sludge

Diethylhexyl phthalate (DEHP) is a common plasticizer in industrial production. Recently, environmental problems caused by microplastics have drawn wide attention. As the microplastics have a large specific surface area, the release rate of the plasticizer from the microplastics to the environment is accelerated. The DEHP in the wastewater enters the wastewater treatment plants (WWTPs) along with the urban pipeline. After DEHP enters the WWTPs, it may affect the anaerobic fermentation with waste activated sludge (WAS) as raw material. So far, there has been no study on the effect of DEHP on anaerobic fermentation of WAS. Our study focused on the impact of exogenous DEHP on WAS anaerobic fermentation, and the results showed that DEHP mainly affects the solubilization stage of sludge anaerobic digestion, but has no significant effect on other stages. It does not affect the total yield and composition of short-chain fatty acids (SCFA). However, DEHP inhibited the solubilization process of WAS anaerobic fermentation, which was mainly manifested by the changes of soluble protein and soluble polysaccharide in the system. The results of the analysis of microbial communities revealed that the addition of DEHP did not change the diversity of microbial communities, but caused a change in the abundance of microbial organisms. DEHP reduced the abundance of acetogen bacteria and increased the abundance of methanogens. This work provides some insights into WAS fermentation systems in the presence of DEHP and helps to gain a better understanding of the potential environmental hazards of microplastics.

A Detailed Review Study on Potential Effects of Microplastics and Additives of Concern on Human Health

The distribution and abundance of microplastics into the world are so extensive that many scientists use them as key indicators of the recent and contemporary period defining a new historical epoch: The Plasticene. However, the implications of microplastics are not yet thoroughly understood. There is considerable complexity involved to understand their impact due to different physical-chemical properties that make microplastics multifaceted stressors. If, on the one hand, microplastics carry toxic chemicals in the ecosystems, thus serving as vectors of transport, they are themselves, on the other hand, a cocktail of hazardous chemicals that are added voluntarily during their production as additives to increase polymer properties and prolong their life. To date, there is a considerable lack of knowledge on the major additives of concern that are used in the plastic industry, on their fate once microplastics dispose into the environment, and on their consequent effects on human health when associated with micro and nanoplastics. The present study emphasizes the most toxic and dangerous chemical substances that are contained in all plastic products to describe the effects and implications of these hazardous chemicals on human health, providing a detailed overview of studies that have investigated their abundance on microplastics. In the present work, we conducted a capillary review of the literature on micro and nanoplastic exposure pathways and their potential risk to human health to summarize current knowledge with the intention of better focus future research in this area and fill knowledge gaps.

Trends and Patterns of Phthalates and Phthalate Alternatives Exposure in Pregnant Women from Mexico City during 2007-2010

Phthalates are associated with several adverse health outcomes, but few studies have evaluated phthalate exposures in Mexican populations, particularly pregnant women. Between 2007 and 2011, 948 pregnant women from Mexico City were recruited as part of the PROGRESS cohort. We quantified 17 metabolites of phthalates and phthalate alternatives in urine samples collected during the second and third trimesters and examined temporal trends of metabolite concentrations, within-person reproducibility, and relations of individual metabolites with sociodemographic, lifestyle, and occupational factors. Concentrations of mono-2-ethyl-5-carboxypentyl terephthalate, a metabolite of the alternative phthalate di-2-ethylhexyl terephthalate, increased monotonically from 2007 to 2010 (31% per year; 95% confidence interval = 23 and 39%). We observed moderate to high correlations among metabolites collected at the same visit, but there was high variability between second and third trimester phthalate metabolite concentrations (intraclass correlation coefficients = 0.17-0.35). In general, higher socioeconomic status was associated with higher phthalate concentrations. Some metabolites were associated with maternal age and education, but no consistent patterns were observed. Women working in the home and those who worked in administration had higher concentrations of several phthalate metabolites relative to students, professionals, and those in customer service. Biomonitoring efforts are warranted to investigate present and future exposure trends and patterns.

Phthalate exposure and prostate cancer in a population-based nested case-control study

BACKGROUND

Phthalic acid esters are established as endocrine disruptors. The study aimed to evaluate the association between urinary phthalate metabolites and prostate cancer occurrence.

METHODS

The study was based on the Taiwan Community-Based Cancer Screening Program, which was set up in 1991-1992 and followed periodically. By 2010, 80 incident prostate cancer cases were identified in the 12,020 men. For each case, 2 controls were randomly selected, matched by age (±3 years), urine collection date (±3 months), and residential township. Frequently used phthalate metabolites from the urine samples were quantified by liquid chromatography/electrospray ionization tandem mass spectrometry. Logistic regression was conducted to assess the association between the exposure levels and prostate cancer occurrence.

RESULTS

Exposure to di (2-ethylhexyl), butyl-benzyl and di-isobutyl phthalates (DEHP, BBzP, DiBP) was positively associated with prostate cancer in men with waist circumference (WC) ≥90 cm but not in the leans. Odds ratio for the DEHP metabolite summary score (upper tertile compared to the rest) and prostate cancer were 7.76 (95% CI = 1.95-30.9) for WC ≥ 90 cm.

CONCLUSIONS

DEHP, BBzP, and DiBP exposure were associated with prostate cancer occurrence in abdominally obese men. The main limitation remains the lack of mechanistic experiments and comparable toxicological data.

Phthalates levels in cold-pressed oils marketed in Turkey

Cold-pressed oils are valuable vegetable oils. Phthalates are used as plasticizers and additives in foodstuffs and personal care products. Studies have shown that phthalates have harmful effects on human health. In this study, five phthalates di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), butyl-benzylphthalate (BBP), diisononyl phthalate (DiNP), and diisodecyl phthalate (DiDP) were evaluated in 30 different cold-pressed oils marketed in Turkey. DEHP was widespread in oils and detected in 18 of the 30 samples, ranging from 0.56 to 92.12 mg/kg. DBP was the second determined phthalate and detected in six of 30 oil samples at concentrations from 0.10 to 51.63 mg/kg. The other phthalates, BBP, DiNP, and DiDP were found in 4, 5, and 2 from a total of 30 samples, respectively. BBP and DiNP ranged between 3.88-6.04 and 4.26-80.74, respectively. DiDP was found in 2 samples with 85.02 and 2.69 mg/kg.

Influence of Airborne Particles' Chemical Composition on SVOC Uptake from PVC Flooring-Time-Resolved Analysis with Aerosol Mass Spectrometry

We sampled ammonium sulfate particles and indoor particles of outdoor origin through a small chamber covered with polyvinyl chloride flooring. We measured the uptake of semivolatile organic compounds (SVOCs) by the airborne particles in real time. The particles acquired SVOC mass fractions up to 10%. The phthalate ester (di(2-ethylhexyl)phthalate) (DEHP), a known endocrine disruptor, contributed by approximately half of the sorbed SVOC mass. The indoor particles acquired a higher DEHP fraction than laboratory-generated ammonium sulfate aerosol. We attribute this increased uptake to absorption by organic matter present in the indoor particles. Using a thermodenuder to remove volatile components, predominantly organics, reduced the SVOC uptake. Positive matrix factorization applied to the organic mass spectra suggests that hydrocarbon-like organic aerosol (typically fresh traffic exhaust) sorbs DEHP more efficiently than aged organic aerosol. The SVOC uptake is one of the processes that modify outdoor pollution particles after they penetrate buildings, where the majority of exposure occurs. Particles from indoor sources, typically dominated by organic matter, will undergo such processes as well. Aerosol mass spectrometry improves the time resolution of experimental investigations into these processes and enables experiments with lower, relevant particle concentrations. Additionally, particle size-resolved results are readily obtained.

The plastisphere in marine ecosystem hosts potential specific microbial degraders including Alcanivorax borkumensis as a key player for the low-density polyethylene degradation

Most plastics are released to the environment in landfills and around 32% end up in the sea, inducing large ecological and health impacts. The plastics constitute a physical substrate and potential carbon source for microorganisms. The present study compares the structures of bacterial communities from floating plastics, sediment-associated plastics and sediments from the Mediterranean Sea. The 16S rRNA microbiome profiles of surface and sediment plastic-associated microbial biofilms from the same geographic location differ significantly, with the omnipresence of Bacteroidetes and Gammaproteobacteria. Our research confirmed that plastisphere hosts microbial communities were environmental distinct niche. In parallel, this study used environmental samples to investigate the enrichment of potential plastic-degrading bacteria with Low Density PolyEthylene (LDPE), PolyEthylene Terephthalate (PET) and PolyStyrene (PS) plastics as the sole carbon source. In this context, we showed that the bacterial community composition is clearly plastic nature dependent. Hydrocarbon-degrading bacteria such as Alcanivorax, Marinobacter and Arenibacter genera are enriched with LDPE and PET, implying that these bacteria are potential players in plastic degradation. Finally, our data showed for the first time the ability of Alcanivorax borkumensis to form thick biofilms specifically on LDPE and to degrade this petroleum-based plastic.

Association of exposure to phthalates with cardiometabolic risk factors in children and adolescents: a systematic review and meta-analysis

Recent studies revealed controversial results on the association of exposure to phthalates with cardiometabolic risk factors in children and adolescents. Therefore, this systematic review and meta-analysis was conducted in this regard. At first, we searched English-language papers in Scopus, Web of Science, and PubMed databases, with no restriction of time, till the end of the year 2018. We performed a comprehensive literature search for association between phthalate exposure and cardiometabolic risk factors including obesity, hypertension, hyperglycemia, and dyslipidemia. Among 99 published papers found in scientific databases, 17 cohort, 15 cross-sectional, and three case-control studies were included in the meta-analysis. We observed a significant association between the concentrations of phthalates and their metabolites with body mass index (BMI), BMI z-score, waist circumference (WC), and low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and glucose in serum. In addition, significant association was observed between prenatal phthalate exposure and birth weight. To the best of our knowledge, this is the first meta-analysis of its kind. It shows positive association between phthalate exposure and some cardiometabolic risk factors in children and adolescents. Therefore, prevention of exposure to phthalates and reduction of their use should be underscored in strategies for primordial prevention of cardiovascular diseases. Recent studies revealed controversial results on the association of exposure to phthalates with cardiometabolic risk factors in children and adolescents. Therefore, this systematic review and meta-analysis was conducted in this regard.

The role of ANXA5 in DBP-induced oxidative stress through ERK/Nrf2 pathway

Di-N-butylphthalate (DBP) have given rise to more and more attention due to its unique endocrine toxicity to male reproductive system. Our previous studies have demonstrated antioxidative Nrf2 (nuclear factor erythroid related factor 2) pathway play a vital role in DBP induced oxidative stress injury. ANXA5 (annexin A5), which is highly expressed in testicular Leydig and Sertoli cells, was found upregulated after DBP stimulation. Mouse Leydig and Sertoli cells were exposed to different concentration of DBP for 24 h to examine the ROS (Reactive oxygen species), MDA (Malondialdehyde), SOD (superoxide dismutase) level and ANXA5, Nrf2, NQO1 (NAD(P)H-quinone oxidoreductase 1), HO-1 (heme oxygenase 1) and ERK/P-ERK protein expression by DHE (Dihydroethidium) staining, ELISA (enzyme-linked immunosorbent assay) and Western blot respectively. Firstly, the oxidative stress injury induced by DBP was re-validated. Then, we confirmed the change of Nrf2 pathway and ANXA5 level after DBP exposure to testicular cells. Additionally, overexpressed ANXA5 could activate Nrf2/HO-1/NQO1 antioxidant pathway and significantly attenuate DBP-induced oxidative stress. Ultimately, we demonstrated ANXA5 could increase ERK phosphorylated level and the activated role of ANXA5 on ERK/Nrf2 pathway could be reversed by ERK inhibitor. Overall, this study illuminated that ANXA5 could defend testicle Leydig and Sertoli cells against DBP-induced oxidative stress injury through ERK/Nrf2 pathway.

Modulation of brain serotonin by benzyl butyl phthalate in Fundulus heteroclitus (mummichog)

Endocrine-disrupting chemicals have been known to alter important animal behaviors by modulating serotonin (5-hydroxytryptamine, 5-HT) and dopamine. F. heteroclitus (mummichog) brain serotonin and dopamine levels were quantified by enzyme-linked immunosorbent assay (ELISA) following a 28-day exposure regimen involving daily doses of either 0.1 mg l^-1 benzyl butyl phthalate (BBP) dissolved in acetone or acetone alone (0.1 mg l^-1). No differences in mean brain mass or total protein homogenate were induced by exposure to the acetone vehicle or BBP in acetone. The acetone vehicle had no effect on dopamine, serotonin, or tyrosine hydroxylase levels, but acetone did decrease tryptophan hydroxylase levels (p = 0.011). Exposure to BBP in acetone decreased dopamine (p = 0.024), increased serotonin (p < 0.001), reduced tryptophan hydroxylase as compared to the acetone vehicle alone (p < 0.001), and had no significant effect on tyrosine hydroxylase levels. This study is the first to report modulation of F. heteroclitus brain serotonin and its enzyme tryptophan hydroxylase following sub-lethal exposure to BBP in an acetone vehicle. In addition, modulation of brain dopamine in F. heteroclitus, sans simultaneous modulation of tyrosine hydroxylase, was also observed. These findings support the use of F. heteroclitus for assessing sub-lethal BBP exposure.

A Novel VIII Carboxylesterase with High Hydrolytic Activity Against Ampicillin from a Soil Metagenomic Library

A novel carboxylesterase gene, named dlfae4, was discovered and sequenced from a soil metagenomic library. The dlfae4 gene was composed of 1017 base pairs encoding 338 amino acid residues with a predicted molecular mass of 37.2 kDa. DLFae4 exhibited strong hydrolytic activity towards methyl ferulate under optimum pH and temperature conditions (pH 8.6, 50 °C) and displayed remarkable thermostability, with residual activity as high as 50% after incubation for 3 h at 60 °C. A family VIII esterase DLFae4 was found to contain a typical serine residue within the S-X-X-K motif, which serves as a catalytic nucleophile in class C β-lactamases and family VIII esterases. As a consequence of its high sequence similarity with β-lactamases, DLFae4 exhibited significant hydrolytic activity towards ampicillin. In addition, DLFae4 was found to be the first known member of family VIII carboxylesterases with phthalate-degrading ability. Site-directed mutagenesis studies revealed that Ser11, Lys14, and Tyr121 residues play an essential catalytic role in DLFae4. These new findings, which are of great importance for further in-depth research and engineering development of carboxylesterases, should advance the implementation of biotechnological applications.

Prenatal exposure to phthalates and neurocognitive development in children at two years of age

BACKGROUND

Phthalates are a family of endocrine disruptors with short elimination half-lives in the human body. To date, few epidemiological studies have examined repeated measures of maternal urinary phthalates and the combined effects of prenatal exposure to multiple phthalates on children's neurocognitive development.

OBJECTIVES

We aimed to investigate the association between children's neurocognitive development at 2 years of age and prenatal phthalate exposure, as assessed by repeated measurements during pregnancy, and to further examine the effects of co-exposure to multiple phthalates using cumulative risk assessment.

METHOD

Within a prenatal cohort in Wuhan, China, we measured five high-molecular-weight (HMW) phthalates and three low-molecular-weight (LMW) phthalate metabolites' concentrations in three urine samples collected in the 1st, 2nd, and 3rd trimester of pregnancy from each mother. We assessed neurocognitive development by Bayley Scales of Infant and Toddler Development (BSID) at 2 years of age (n = 476) to obtain the children's mental development index (MDI) and psychomotor development index (PDI).

RESULTS

Higher exposure levels to LMW phthalates compared to HMW phthalates were observed in our population. Ln-transformed averaged concentration of mono-n-butyl phthalate (MnBP), a metabolite of the LMW phthalate di-n-butyl phthalate (DnBP) during pregnancy, was associated with decreased PDI scores in all children (β = -1.90, 95% CI: -3.43, -0.37). Similarly, the averaged sum concentration of ∑dibutyl phthalate (∑DBP) was associated with decreased PDI scores in all children (β = -1.89, 95% CI: -3.63, -0.15). A negative trend of association between exposure to HMW phthalates and PDI scores was observed in girls, while a positive association was found in boys. In cumulative risk assessment analyses, we consistently observed that the hazard quotient of DnBP (the parent compound of MnBP) was inversely associated with PDI scores in all children, whereas the hazard quotient of di-2-ethylhexyl phthalate (DEHP), an HMW phthalate, was positively associated with PDI scores in boys only.

CONCLUSIONS

This study is the first to use repeated measurement of maternal urinary phthalates in all three trimesters to assess prenatal exposure in relation to children's neurodevelopment. Our study suggested a negative association between prenatal exposure to MnBP and children's psychomotor development, and potentially sex-specific associations between HMW phthalates and neurocognitive development among boys and girls. These findings warrant further confirmation.

Association between Phthalate Metabolites and Risk of Endometriosis: A Meta-Analysis

Objective: The association between phthalates and endometriosis risk is inconclusive. This meta-analysis aims to evaluate the association between five different phthalate metabolites and endometriosis, based on current evidence. Methods: The literature included PubMed, WOS (web of science), and EMBASE, published until 3 March 2019. We selected the related literature and evaluated the relationship between phthalates exposure and endometriosis risk. All statistical analyses were conducted with STATA version 12.0. Results: Data from eight studies were used in this review. The results of this analysis showed that mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) exposure was potentially associated with endometriosis (OR = 1.246, 95% CI = 1.003-1.549). We have not found positive results in mono(2-ethylhexyl) phthalate (MEHP), monoethyl phthalate (MEP), monobenzyl phthalate (MBzP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP) analyses (MEHP: OR = 1.089, 95% CI = 0.858-1.383; MEP: OR = 1.073, 95% CI = 0.899-1.282; MBzP: OR = 0.976, 95% CI = 0.810-1.176; MEOHP: OR = 1.282, 95% CI = 0.874-1.881). In subgroup analyses for regions, the associations were significant between MEHHP and endometriosis in Asia (OR = 1.786, 95% CI = 1.005-3.172, I² = 0%), but not in USA (OR = 1.170, 95% CI = 0.949-1.442, I² = 45.6%). Conclusions: Our findings suggested a potential statistical association between MEHHP exposure and endometriosis, particularly, the exposure of MEHHP might be a potential risk for women with endometriosis in Asia. However, positive associations between the other four Phthalate acid esters (PAEs) and endometriosis was not found. Given the weak strength of the results, well-designed cohort studies, with large sample sizes, should be performed in future.

Emission characteristics of diethylhexyl phthalate (DEHP) from building materials determined using a passive flux sampler and micro-chamber

Emission rates of diethylhexyl phthalate (DEHP) from building materials, such as vinyl floorings and wall paper, determined using a passive flux sampler (PFS) were constant over the week-long measurement period. Emission rates for vinyl floorings and wallpaper were linearly correlated to the inverse of diffusion distance, which corresponds to the internal depth of the PFS. Surface-air DEHP concentrations (y0) were estimated as 1.3-2.3 μg/m3 for materials having a boundary layer molecular diffusion rate-limiting step. The partition coefficient (Kmaterial-air) was estimated as 3.3-7.5 × 1010 for these materials. Additionally, emission rates of DEHP from same building materials determined using a micro-chamber were 4.5-6.1 μg/m2/h. Mass transfer coefficients in the micro-chamber (hm) were estimated by comparing the results using the PFS and micro-chamber, and these were 1.1-1.2 × 10-3 and 8.1 × 10-4 m/s for vinyl floorings (smooth surface) and wallpaper (rough surface), respectively. The thickness of boundary layer on the surface of building materials in the micro-chamber were estimated to be 2.5-2.6 and 3.7 mm for vinyl floorings and wallpaper, respectively.

Bis(2-ethylhexyl) phthalate induces DNA strand breaks and gene expression alterations in larval zebrafish Danio rerio

Contamination of the aquatic environment by plastic industrial products and their by-products is remarkable. Because of their physical, chemical, and biological degradation resistance, plasticizers can enter the food chain of living organisms, accumulate in the body and generate toxic effects. Here we determined the potential toxic effects of bis(2-ethylhexyl) phthalate (DEHP) plasticizer to larval (72 h post fertilization) zebrafish ( Danio rerio) by analyzing changes in expression levels of stress-related genes ( p53, rad51, and xrcc5) by the quantitative real-time polymerase chain reaction. Also, possible DNA damage by DEHP in larvae was determined. The concentration of DEHP (0–160 mg/l) that killed 50% of the larval zebrafish within 96 h was 54.02 mg/l. There was a concentration-related increase in DNA damage in cells from larvae exposed (96 h) to DEHP. DNA damage of 31.13% (mean ± standard error of the mean) was observed in larvae at the highest sublethal DEHP concentration (10 mg/l). Some significant differences in the induction of stress-related genes were also observed in larvae exposed to DEHP relative to control ( p < 0.05). The conclusion drawn from this ecotoxicological risk assessment is that, under present use and exposure patterns, DEHP presents a small hazard to zebrafish larvae.

Prenatal toxicity of the environmental pollutants on neuronal and cardiac development derived from embryonic stem cells

Pesticides, antibiotics, and industrial excipients are widely used in agriculture, medicine, and chemical industry, respectively. They often end up in the environment, not only being not easily decomposed but also being accumulated. Moreover, they may cause serious toxic problems such as reproductive and developmental defects, immunological toxicity, and carcinogenesis. Hence, they are called environmental pollutants. It is known that the environmental pollutants easily enter the body through various channels such as respiration, ingestion of food, and skin contact etc. in everyday life. If they enter the mother through the placenta, they can cause the disturbance in embryo development as well as malfunction of organs after birth because early prenatal developmental process is highly sensitive to toxic chemicals and stress. Embryonic stem cells (ESCs) that consist of inner cell mass of blastocyst differentiate into distinct cell lineages via three germ layers such as the ectoderm, mesoderm, and endoderm due to their pluripotency. The differentiation process initiated from ESCs reflects dynamic nature of embryonic development. Therefore, ESCs have been used as a useful tool to investigate early developmental toxicities of a variety of stress. Based on relatively recent scientific results, this review would address toxicity of a few chemical substances that have been widely used as pesticide, antibiotics, and industrial excipient on ESCs based-prenatal developmental process. This review further suggests how they act on the viability of ESCs and/or early stages of cardiac and neuronal development derived from ESCs as well as on expression of pluripotency and/or differentiation markers through diverse mechanisms.

Chronic dietary administration of lower levels of diethyl phthalate induces murine testicular germ cell inflammation and sperm pathologies: Involvement of oxidative stress

The wide occurrence of male infertility is a matter of grave concern. One of the major causes being exposure to endocrine disrupting chemicals (EDCs) many of which are known reproductive toxicants but the molecular mechanisms of action remain much unexplored. Diethyl phthalate (DEP) is ubiquitous in the environment due to its extensive use as plasticizer in myriad consumer products. In the present study, we sought to find out whether chronic DEP exposure affects reproductive function in sexually mature adult male mice. For this, 8-week old Swiss albino mice were treated with DEP (1 mg and 10 mg kg^-1 body weight day^-1) in diet for three months, mirroring the relevant doses of human exposure, and various analyses were carried out in the testicular germ cells and epididymal spermatozoa. We found that altered testicular histoarchitecture was accompanied with disturbed prooxidant: antioxidant balance in the germ cells. Involvement of Nrf2-HO-1 pathway was crucial in this altered cellular redox state. Besides, NFκB mediated inflammatory response was triggered in the germ cells leading to enhanced levels of proinflammatory cytokines. DEP adversely affected sperm count, motility, viability and morphology. Numerous structural anomalies were found in DEP treated mice spermatozoa reflecting decline in sperm function. Our results revealed overactivation of PARP-1 and subsequent cleavage in spermatozoa with induction of apoptosis as a key mechanism in DEP mediated sperm pathology. Given the indiscriminate use of plasticizers and long term low level human exposure, the present study highlights the undesirable male reproductive outcomes following chronic DEP exposure.

Phthalate exposure alters gut microbiota composition and IgM vaccine response in human newborns

Postnatal exposure to di-(2-ethylhexyl) phthalate (DEHP), a common plasticizer, is associated with allergy development in childhood, suggesting that DEHP exposure may dysregulate immune response in infants. We investigated whether DEHP exposure in newborns through medical treatment affected the gut microbiota pattern and vaccine response, which are both related to immune development. In this prospective cohort study from May 1, 2016 through July 31, 2017, newborns with respiratory distress who were given intravenous infusions (IVs) were enrolled as the DEHP group, and newborns who did not receive IVs were enrolled as the control group. We excluded patients with perinatal maternal probiotics, vaginal delivery, antibiotic treatment, and exclusive human milk or formula feeding. Of 118 infants, urinary phthalate metabolite analysis revealed that the calculated DEHP concentrations of the newborns treated with IVs (n = 15) were higher than those in the control group (n = 10) (p = 0.0001). DEHP exposure altered bacterial communities both in composition and diversity, particularly decreases in Rothia sp. and Bifidobacterium longum in the DEHP group. Furthermore, DEHP exposure significantly enhanced anti-HBsAg-IgM responses in the DEHP group (p = 0.013). Early-life DEHP exposure alter gut microbiota of newborns and may change their immune responses in later life.

Couples exposure to phthalates and its influence on in vitro fertilization outcomes

This prospective study examined the associations between the levels of eight urinary phthalate metabolites in 599 couples and in vitro fertilization (IVF) outcomes. We used log-binomial multivariate regression to estimate relative risks (RR) for the association between phthalate concentration and IVF binary outcomes (fertilization rate >50%, biochemical pregnancy, clinical pregnancy and live birth) for each woman after adjusting the model for the concentration in a male partner and each relevant confounders. RR was expressed per unit increase in log-transformed urinary metabolite concentration. The percentage of bis-2-ethylhexyl phthalate (DEHP) metabolites excreted as mono-2-ethylhexyl phthalate (MEHP) was calculated as %MEHP. Urinary MEHP in women was associated with an increased risk of biochemical pregnancy (RR = 1.35; p = 0.04), failed clinical pregnancy (RR = 1.56; p = 0.006) and live birth (RR = 1.54; p = 0.011). An increase in monoethyl phthalate was associated with a high risk of failed clinical pregnancy (RR = 1.25; p = 0.03) and live birth (RR = 1.35; p = 0.006). An increase in %MEHP was associated with an increase in the risk of biochemical pregnancy (RR = 1.55; p = 0.05), failed clinical pregnancy (RR = 1.73; p = 0.02) and live birth (RR = 1.65; p = 0.046). Our results demonstrated that exposure to some phthalates may adversely affect IVF outcomes, particularly when couples' exposure was jointly modeled, emphasizing the importance of a couple-based approach in assessing fertility outcomes. The associations between IVF outcomes and DEHP metabolites were stronger in women whose %MEHP was >75th percentile which may be due to their less efficient metabolism and excretion of DEHP and/or MEHP.

Phytotoxicity, cytotoxicity and genotoxicity evaluation of organic and inorganic pollutants rich tannery wastewater from a Common Effluent Treatment Plant (CETP) in Unnao district, India using Vigna radiata and Allium cepa

The leather industry is a major source of environmental pollution in India. The wastewater generated by leather industries contains very high pollution parameters due to the presence of a complex mixture of organic and inorganic pollutants even after the treatment at a Common Effluent Treatment Plant (CETP) and disturbs the ecological flora and fauna. The nature, characteristics and toxicity of CETP treated wastewater is yet to be fully elucidated. Thus, this study aims to characterize and evaluate the toxicity of CETP treated tannery wastewater collected from the Unnao district of Uttar Pradesh, India. In addition to measuring the physico-chemical parameters, the residual organic pollutants was identified by GC-MS analysis and phytotoxicity, cytotoxicity and genotoxicity of the treated wastewater was evaluated using Vigna radiata L. and Allium cepa L. Results showed that the treated wastewater contained very high pollution parameters (TDS 3850 mg/L, BOD 680 mg/L, COD-1300 mg/L). GC-MS analysis revealed the presence of various types of residual organic pollutants including benzoic acid, 3-[4^,-(T-butyl) Phenyl] furan-2-5-dione, benzeneacetamide, resorcinol, dibutyl phthalate, and benzene-1,2,4-triol. Further, toxicological studies showed the phytotoxic nature of the wastewater as it inhibited seed germination in V. radiata L. and root growth of A. cepa. Genotoxicity was evidenced in the root tip cell of A. cepa where chromosomal aberrations (stickiness, chromosome loss, C-mitosis, and vagrant chromosome) and nuclear abnormalities like micronucleated and binucleated cells were observed. Thus, results suggested that it is not safe to discharge these wastewater into the environment.

Gonad pathology and intersex severity in pelagic (Tilapia zilli) and benthic (Neochanna diversus and Clarias gariepinus) species from a pesticide-impacted agrarian catchment, south-south Nigeria

Pesticides are distributed to different degrees in surface water and sediment, thus, risks of toxicity and adverse impacts to physiology of resident species could be determined by their microhabitat (sub-habitat) associations, either water column or sediment. River Owan receives pesticide input from diffuse sources from adjacent farmlands. Surface water, sediment and fish samples [(Pelagic: Tilapia zilli (n = 92) and benthic: Neochanna diversus (n = 59), Clarias gariepinus (n = 68) were collected within the catchment area across seasons for 18-months (August 2016-January 2018) and measured for pesticide levels. Testicular and Ovarian tissue samples across the three species were also examined for pathological alterations. Individual pesticide concentrations in surface water and sediment exceeded international allowable limits, while concentration of pesticide residues in tissues of benthic species was higher compared to pelagic fish. Histopathological assessment revealed a higher incidence of ovarian disruption including atretic follicles, intersex and disorganization of ovarian structure in benthic (bottom-dwelling) fish (C. gariepinus and N. diversus) compared to pelagic (water-column) fish (T. zilli). Males benthic fish species also recorded more severe anomalies, compared to pelagic fish. The damages and anomalies observed in ovarian and testicular tissue indicate chronic responses to pollutant exposure, and implicates the elevation of pesticide concentrations in surface water and sediment above permissible limits. The higher incidence of anomalies recorded for benthic species compared to pelagic species, indicates greater risks of reproductive disruption and could be associated with the microhabitat preferences (water-column or sediment).

The effects of bisphenol A, benzyl butyl phthalate, and di(2-ethylhexyl) phthalate on estrogen receptor alpha in estrogen receptor-positive cells under hypoxia

Endocrine-disrupting chemicals (EDCs) are widely used in various consumer goods. Consequently, humans are constantly exposed to EDCs, which is associated with a variety of endocrine-related diseases. In this study, we demonstrated the effects of bisphenol A (BPA), benzyl butyl phthalate (BBP), and di(2-ethylhexyl) phthalate (DEHP) on estrogen receptor alpha (ERα) expression under normoxia and hypoxia. First, we confirmed the effects of EDCs on ER activity using OECD Test Guideline 455. Compared to the 100% activity induced by 1 nM 17-β-estradiol (positive control), BPA and BBP exhibited 50% ERα activation at concentrations of 1.31 μM and 4.8 μM, respectively. In contrast, and consistent with previous reports, DEHP did not activate ERα. ERα is activated and degraded by hypoxia in breast cancer cells. BPA, BBP, and DEHP enhanced ERα-mediated transcriptional activity under hypoxia. All three EDCs decreased ERα protein levels under hypoxia in MCF-7 cells. The transcriptional activity of hypoxia-inducible factor-1 was decreased and secretion of vascular endothelial growth factor (VEGF) was increased by BPA and BBP under hypoxia in MCF-7 cells, but not by DEHP. All three EDCs decreased the ERα protein expression level in Ishikawa human endometrial adenocarcinoma cells, and DEHP caused a weak decrease in VEGF secretion under hypoxia. These results demonstrate down-regulation of ERα by EDCs may influence the pathological state associated with hypoxia.

Di-(2-Ethylhexyl) Phthalate as a Chemical Indicator for Phthalic Acid Esters: An Investigation into Phthalic Acid Esters in Cultivated Fields and E-Waste Dismantling Sites

Phthalic acid esters (PAEs) represent an ongoing pollution problem and have attracted extensive attention due to their ubiquitous presence in the environment. We investigated the distribution of 6 PAEs (benzyl butyl phthalate [BBP], dibutyl phthalate [DBP], di-(2-ethylhexyl) phthalate [DEHP], diethyl phthalate [DEP], dimethyl phthalate [DMP], and di-n-octyl phthalate [DnOP]) in cultivated soils, including vegetable fields and paddy fields, as well as the soils of E-waste dismantling sites. We also explored the relationship between the particle size of soils and the distribution of PAEs, put forward a novel method to forecast the occurrence and fate of PAEs in soils with DEHP used as a chemical indicator, and made a preliminary assessment of the potential ecological risks of the 6 target compounds in soils. The results showed that the detection rate of target PAEs was 100%, and that the concentrations of ∑₆ PAEs ranged from 1.2 to 7.3 mg/kg in vegetable fields, 1.2 to 1.5 mg/kg in paddy fields, and 11.8 to 17.9 mg/kg in E-waste dismantling sites. In addition, DEHP exhibited the maximum concentrations (0.480-15.34 mg/kg) in all soil samples. The results also showed that in the wake of decreasing particle size, increasing soil organic carbon would enhance the sorption of PAEs in soils. Moreover, the correlation formula of DEHP successfully predicted the concentrations of other PAEs and ∑ ₆ PAEs in soils, suggesting that DEHP could be a dependable chemical indicator for forecasting the environmental occurrence of PAEs in soils. Based on the residual levels in the trial sites and limited toxicity data, high risks to soil organisms are expected for DBP, DEP, and DEHP, and low-medium risks for BBP, DnOP, and DMP. Environ Toxicol Chem 2019;00:1-11. © 2019 SETAC.

The extent and predictors of phthalate exposure among couples undergoing in vitro fertilization treatment

Phthalates are chemicals used as plasticizers and solvents in many consumer products but are suspected of disrupting the endocrine system and are known for their reproductive/developmental health risks. This study examined the extent and predictors of phthalate exposure among 599 couples undergoing in vitro fertilization. A questionnaire was administered to obtain sociodemographic, health, and lifestyle data, and two spot urine samples were collected from the couples to analyze eight phthalate metabolites, cotinine (COT) as a smoking index, and creatinine to adjust for urine dilution. Seven phthalate metabolites were detected in > 94% of the urine samples, and monobenzyl phthalate (MBzP) was found in 24% of the women and 26% of their male partners. Median phthalate levels were highest for monoethyl phthalate (MEP), at 333.26 μg/l in women and 290 μg/l in male partners, and lowest for MBzP, at 1.17 μg/l in women and 1.14 μg/l in male partners. Correlation coefficients of ≥ 0.4 between the women and their male partners for the eight urinary phthalate metabolites may indicate a shared source of exposure. A multivariate regression model was used to assess the association between predictors and each urinary phthalate metabolite. Several potential predictors for the variations in specific urinary phthalate metabolites were identified, including the body mass index, age, socioeconomic status, and regional distribution for both women and their male partners but with slightly different patterns. Women with a history of breastfeeding, using bottled water for cooking and storing food in plastic bags had lower MEP (8.7%), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) (9.2%), and both mono-iso-butyl phthalate and MECPP (8.2 and 8.1%). A history of contraceptive use was associated with an increase in MECPP (8.7%), mono-(2-ethyl-5-hydroxyhexyl) phthalate (11.4%), mono-(2-ethyl-5-oxohexyl) phthalate (7.6%), and the molar sum of bis (2-ethylhexyl) phthalate metabolites (8.9%). Urinary COT levels were associated with an increase of 10-16% in all urinary metabolites in women but of only 10.5% in mono-(2-ethylhexyl) phthalate in male partners. More than 95% of the couples reported the use of cosmetics, perfumes, and personal-care products, but we were not able to find associations with urinary phthalate metabolites, perhaps due to their short half-lives. MEP levels associated with the use of household cleaning products were 11.2% higher in male partners. Our levels were generally higher than those reported elsewhere, perhaps due to different lifestyles, cultural practices, dietary habits, use of personal-care products, and governmental legislation.

Exposure and ecological risk of phthalate esters in the Taihu Lake basin, China

The environmental spatial distribution and exposure risk of 6 phthalate esters (PAEs) including dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl benzyl phthalate (BBP), di-n-octyl phthalate (DnOP), bis(2-ethylhexyl) phthalate (DEHP), and dibutyl phthalate (DBP), in surface water and sediment of Taihu Lake basin, China, were investigated at 65 sites. The exposure concentrations of 6 PAEs (∑6PAEs) detected in the samples spanned a range of 0.740-13.0 μg/L in surface water and 5.15-20.9 mg/kg in sediment. DBP and DEHP were the predominant compounds in surface water, with mean concentrations of 1.59 μg/L and 1.29 μg/L, respectively. DnOP was the predominant compound in sediment with mean concentration of 7.41 mg/kg. Ecological risk assessment was conducted by the hazard quotient method in which the predicted no effect concentration (PNEC) was derived from the species sensitivity distribution (SSD) curve. The results showed that DEHP in water phase posed a higher environmental risk than the other PAEs, while the DEP in sediment posed a high risk to the aquatic system. The study contributed to better understanding the presence of PAEs in Taihu Lake basin and provided valuable information for managing and controlling PAEs pollution.

A Review of Biomonitoring of Phthalate Exposures

Phthalates (diesters of phthalic acid) are widely used as plasticizers and additives in many consumer products. Laboratory animal studies have reported the endocrine-disrupting and reproductive effects of phthalates, and human exposure to this class of chemicals is a concern. Several phthalates have been recognized as substances of high concern. Human exposure to phthalates occurs mainly via dietary sources, dermal absorption, and air inhalation. Phthalates are excreted as conjugated monoesters in urine, and some phthalates, such as di-2-ethylhexyl phthalate (DEHP), undergo secondary metabolism, including oxidative transformation, prior to urinary excretion. The occurrence of phthalates and their metabolites in urine, serum, breast milk, and semen has been widely reported. Urine has been the preferred matrix in human biomonitoring studies, and concentrations on the order of several tens to hundreds of nanograms per milliliter have been reported for several phthalate metabolites. Metabolites of diethyl phthalate (DEP), dibutyl- (DBP) and diisobutyl- (DiBP) phthalates, and DEHP were the most abundant compounds measured in urine. Temporal trends in phthalate exposures varied among countries. In the United States (US), DEHP exposure has declined since 2005, whereas DiNP exposure has increased. In China, DEHP exposure has increased since 2000. For many phthalates, exposures in children are higher than those in adults. Human epidemiological studies have shown a significant association between phthalate exposures and adverse reproductive outcomes in women and men, type II diabetes and insulin resistance, overweight/obesity, allergy, and asthma. This review compiles biomonitoring studies of phthalates and exposure doses to assess health risks from phthalate exposures in populations across the globe.

Derivation of aquatic life criteria for four phthalate esters and their ecological risk assessment in Liao River

As a critical family of endocrine disruptors, phthalate esters (PAEs) attracted considerable attentions due to increasingly detected worldwide. Aquatic life criteria (ALC) for PAEs are crucial for their accurate ecological risk assessment (ERA) and have seldom been derived before. Given this concern, the purpose of the present study is to optimize the ALCs of four priority PAEs to estimate their ecological risks in Liao River. Reproductive endpoint was found to be more sensitive than other endpoints. Thus, reproduction related toxicity data were screened to derive ALCs applying species sensitivity distribution (SSD) method. ALCs of DEHP, DBP, BBP and DEP were calculated to be 0.04, 0.62, 4.71 and 41.9 μg L^-1, which indicated decreased toxicity in sequence. Then, the derived ALCs of the four PAEs were applied to estimate their ecological risks in Liao River. A total of 27 sampling sites were selected to detect and analyze the exposure concentrations of PAEs. ERA using the hazard quotient (HQ) method was conducted. The results demonstrated that DEHP exhibited higher risks at 92.6% of sampling sites, and risks posed by DBP were moderate at 63.0% sampling sites. However, risks posed by BBP were low at 70.4% of sampling sites, and there were no risks posed by DEP at 96.3% of sampling sites. The results of probabilistic ecological risk assessment (PERA) indicated that probabilities of exceeding effects thresholds on 5% of species were 60.41%, 0%, 0.12%, 14.28% for DEHP, DEP, BBP and DBP, respectively. The work provides useful information to protect aquatic species in Liao River.

Di-(2-ethylhexyl) phthalate induced an increase in blood pressure via activation of ACE and inhibition of the bradykinin-NO pathway

Epidemiological studies and animal experiments have suggested that exposure to Di-(2-ethylhexyl) phthalate (DEHP) is strongly associated with an increase in blood pressure. However, the mechanisms that result in the detrimental effects of DEHP exposure on blood pressure are unclear. In our study, mice were orally exposed to DEHP dosages of 0.1, 1, 10 mg/kg/day for 6 weeks. The results showed that DEHP could induce a significant increase in systolic blood pressure (SBP) and heart rate, and a significant thickening of the ventricular wall. To explore the underlying mechanism, we measured the level of: angiotensin converting enzyme (ACE); bradykinin B2 receptor (BK2R); endothelial nitric oxide synthase (eNOS); bradykinin and Ca²⁺ in cardiac cytoplasm as well as in serum nitric oxide (NO). The results suggested that DEHP could induce an increase in ACE levels, and a decrease in bradykinin levels. Moreover, BK2R, Ca²⁺, eNOS and NO decreased when mice were exposed to 10 mg/kg/day DEHP. Interestingly, 5 mg/kg/day angiotensin converting enzyme inhibitor (ACEI) treatment inhibited the increase in blood pressure, and inhibited the decrease in the levels of BK2R, Ca²⁺, eNOS, and NO, that were induced by DEHP exposure. Our results suggest that DEHP might increase blood pressure by activating ACE expression, and inhibiting the bradykinin-NO pathway.

Transcriptome profiling and pathway analysis of the effects of mono-(2-ethylhexyl) phthalate in mouse Sertoli cells

Phthalates are confirmed to have toxic effects on the reproductive system and are likely to have further damaging actions in humans. The present study explored the molecular mechanisms of the toxic effect of mono-(2-ethylhexyl) phthalate (MEHP) on mouse Sertoli cells. Cell apoptosis and proliferation assays were used to assess the effects of MEHP on the TM4 Sertoli cell line derived from mouse testes. TM4 cells were treated with two doses of MEHP or left untreated as a control group, followed by RNA extraction and analysis using high-throughput transcriptome sequencing technology. The gene expression profile obtained was then subjected to a bioinformatics analysis to explore the molecular mechanisms of reproductive toxicity. The results revealed that 528 and 269 genes were upregulated in the high- and low-dose MEHP groups of cells compared with the control group, while 148 and 173 genes were downregulated. Gene ontology (GO) analysis indicated that the differently expressed genes were associated with the GO term 'extracellular region' of the cellular component domain in the high and low MEHP groups. Compared with the control group, eight common pathway changes were identified in the high- and low-dose MEHP groups, including 'terpenoid backbone biosynthesis'. Reverse transcription-quantitative polymerase chain reaction analysis was used to validation, and hermetic effects were observed for certain genes. These results provide an important basis and experimental data for further research into the mechanisms of phthalate-induced toxicity.

Effect of the TYK-2/STAT-3 pathway on lipid accumulation induced by mono-2-ethylhexyl phthalate

BACKGROUND

Mono-2-ethylhexyl phthalate (MEHP), an important metabolite of di (2-ethylhexyl) phthalate (DEHP), can induce lipid metabolic disorder. Previous studies have shown that MEHP promotes 3T3-L1 cell differentiation; however, the underlying mechanism is unclear. The present study was performed to investigate the effect of the TYK-2/STAT-3 pathway on lipid accumulation induced by MEHP.

METHODS

A 3T3-L1 precursor adipocyte differentiation model was exposed to MEHP. 3-Isobutyl-1-methylxanthine (IBMX), dexamethasone (DEX), and insulin were used to establish the 3T3-L1 precursor adipocyte differentiation model. Then the model cells were exposed to MEHP for 8 d. The lipid droplet formation in 3T3-L1 cells was determined with Oil-Red-O staining, and isopropyl alcohol was used to extract the lipid droplets for quantification. Flow cytometry was used to detect the intracellular reactive oxygen species (ROS) and mitochondrial membrane potential. Quantitative real-time polymerase chain reaction (qPCR) was used to detect mRNA expression, and western blotting was used to detect the expression of proteins encoded by TYK-2/STAT-3 pathway genes and adipogenesis-related genes.

RESULTS

MEHP treatment, compared with the control treatment, significantly promoted the differentiation of 3T3-L1 cells and increased the expression of STAT-3 mRNA and protein and P-STAT3 protein in the cells. In addition, MEHP down-regulated the phosphorylation of STAT-3 in mitochondria. MEHP was found to influence the mitochondrial membrane potential and intracellular ROS levels.

CONCLUSION

MEHP may affect adipocyte differentiation and lead to lipid accumulation through the TYK-2/STAT-3 pathway.

Assessing effects of germline exposure to environmental toxicants by high-throughput screening in C. elegans

Chemicals that are highly prevalent in our environment, such as phthalates and pesticides, have been linked to problems associated with reproductive health. However, rapid assessment of their impact on reproductive health and understanding how they cause such deleterious effects, remain challenging due to their fast-growing numbers and the limitations of various current toxicity assessment model systems. Here, we performed a high-throughput screen in C. elegans to identify chemicals inducing aneuploidy as a result of impaired germline function. We screened 46 chemicals that are widely present in our environment, but for which effects in the germline remain poorly understood. These included pesticides, phthalates, and chemicals used in hydraulic fracturing and crude oil processing. Of the 46 chemicals tested, 41% exhibited levels of aneuploidy higher than those detected for bisphenol A (BPA), an endocrine disruptor shown to affect meiosis, at concentrations correlating well with mammalian reproductive endpoints. We further examined three candidates eliciting aneuploidy: dibutyl phthalate (DBP), a likely endocrine disruptor and frequently used plasticizer, and the pesticides 2-(thiocyanomethylthio) benzothiazole (TCMTB) and permethrin. Exposure to these chemicals resulted in increased embryonic lethality, elevated DNA double-strand break (DSB) formation, activation of p53/CEP-1-dependent germ cell apoptosis, chromosomal abnormalities in oocytes at diakinesis, impaired chromosome segregation during early embryogenesis, and germline-specific alterations in gene expression. This study indicates that this high-throughput screening system is highly reliable for the identification of environmental chemicals inducing aneuploidy, and provides new insights into the impact of exposure to three widely used chemicals on meiosis and germline function.

The ever-increasing number of new chemicals introduced into our environment poses a significant problem for risk assessment. In addition, assessing the direct impact of toxicants on human meiosis remains challenging. We successfully utilized a high-throughput platform in the nematode C. elegans, a genetically tractable model organism which shares a high degree of gene conservation with humans, to identify chemicals that affect the germline leading to aneuploidy. We assessed chemicals that are highly prevalent in the environment in worms carrying a fluorescent reporter construct allowing for the identification of X chromosome nondisjunction combined with a mutation increasing cuticle permeability for analysis of low doses of exposure. Follow up analysis of three chemicals: DBP, permethrin and TCMTB, further validated the use of this strategy. Exposure to these chemicals resulted in elevated levels of DNA double-strand breaks, activation of a DNA damage checkpoint, chromosome morphology defects in late meiotic prophase I as well as impaired early embryogenesis and germline-specific changes in gene expression. Our results support the use of this high-throughput screening system to identify environmental chemicals inducing aneuploidy, and provide new insights into the effects of exposure to DBP, permethrin, and TCMTB on meiosis and germline function.

Placental weight in relation to maternal and paternal preconception and prenatal urinary phthalate metabolite concentrations among subfertile couples

INTRODUCTION

Phthalates are known reproductive toxicants that reduce placental and fetal weight in experimental animal studies. Although phthalate exposure has been associated with reduced birth weight in humans, there is limited epidemiologic evidence on whether the placenta is also affected.

OBJECTIVE

To assess whether maternal and paternal preconception and prenatal urinary phthalate metabolite concentrations are associated with placental weight, and the birth weight: placental weight (BW:PW) ratio among singletons conceived by subfertile couples.

METHODS

The present analysis included 132 mothers and 68 fathers, and their corresponding 132 singletons recruited in an academic hospital fertility center in Boston, Massachusetts. Urinary concentrations of eleven phthalate metabolites were measured and averaged in multiple paternal (n = 196) and maternal (n = 596) preconception, and maternal prenatal (n = 328) samples. Placental weight and birth weight (grams) were abstracted from delivery records, and the BW:PW was calculated. We estimated the association of natural log-phthalate metabolite concentrations across windows of exposure with placental weight and the BW:PW ratio using multivariable linear regression models, adjusting for a priori covariates.

RESULTS

In adjusted models, each log-unit increase in paternal urinary concentrations of the sum of di-(2-ethylhexyl) phthalate (ΣDEHP) metabolites was associated with a 24 g (95% CI: -48, -1) decrease in placental weight. We also observed a significant negative association between maternal preconception monoethyl phthalate (MEP) metabolite concentrations and the BW:PW ratio (β = -0.26; 95%CI: -0.49, -0.04). Additionally, each log-unit increase in prenatal MEP metabolite concentrations was associated with a 24 g (95% CI: -41, -7) decrease in placental weight.

CONCLUSIONS

Our results suggest that certain paternal and maternal urinary phthalate metabolites may affect placental weight and the BW:PW ratio. However, given the small sample size within a subfertile cohort and the novelty of these findings, more studies are needed to confirm the present results.

The Role of Peroxisome Proliferator–Activated Receptor Gamma (PPARγ) in Mono(2-ethylhexyl) Phthalate (MEHP)-Mediated Cytotrophoblast Differentiation

BACKGROUND

Phthalates are environmental contaminants commonly used as plasticizers in polyvinyl chloride (PVC) products. Recently, exposure to phthalates has been associated with preterm birth, low birth weight, and pregnancy loss. There is limited information about the possible mechanisms linking maternal phthalate exposure and placental development, but one such mechanism may be mediated by peroxisome proliferator–activated receptor γ (PPARγ). PPARγ belongs to the nuclear receptor superfamily that regulates, in a ligand-dependent manner, the transcription of target genes. Studies of PPARγ-deficient mice have demonstrated its essential role in lipid metabolism and placental development. In the human placenta, PPARγ is expressed in the villous cytotrophoblast (VCT) and is activated during its differentiation into syncytiotrophoblast.

OBJECTIVES

The goal of this study was to investigate the action of mono(2-ethylhexyl) phthalate (MEHP) on PPARγ activity during in vitro differentiation of VCTs.

METHODS

We combined immunofluorescence, PPARγ activity/hCG assays, western blotting, and lipidomics analyses to characterize the impacts of physiologically relevant concentrations of MEHP (0.1, 1, and 10 μM) on cultured VCTs isolated from human term placentas.

RESULTS

Doses of 0.1 and 1 μM MEHP showed significantly lower PPARγ activity and less VCT differentiation in comparison with controls, whereas, surprisingly, a 10 μM dose had the opposite effect. MEHP exposure inhibited hCG production and significantly altered lipid composition. In addition, MEHP had significant effects on the mitogen-activated protein kinase (MAPK) pathway.

CONCLUSIONS

This study suggests that MEHP has a U-shaped dose–response effect on trophoblast differentiation that is mediated by the PPARγ pathway and acts as an endocrine disruptor in the human placenta. https://doi.org/10.1289/EHP3730.

Soil ecotoxicity study of DEHP with respect to multiple soil species

Di (2-ethylhexyl) phthalate or DEHP is classified as an endocrine-disrupting chemical. It is used as a plasticizer and pesticide additive. Moreover, it has a half-life of about 150-300 days. Thus, it is present in the soil environment and soil risk assessments for DEHP are needed. However, a number of studies have focused on the effects of DEHP in a single soil species. In this study, we conducted acute and chronic toxicity testing for DEHP using varied soil species, including plants, earthworms, soil algae, Collembola, and soil nematodes. In the plant toxicity test, no effect was observed at very high concentration except at some endpoints, and no effect was observed in the earthworm toxicity test. However, there were adverse effects on soil algae, Collembola, and nematodes. Notably, in the Collembola assays, the survival of adults decreased significantly at very high concentrations, whereas reproduction was hindered at low concentrations. Similar inhibition of reproduction was noted in the soil nematode assay. This suggests that DEHP has a greater influence on fertility than survival in the adult test species. However, besides hindered reproduction, no effect was observed on soil species at environmentally relevant concentrations.

Embracing microbes in exposure science

Although defined more broadly, exposure science has mainly focused on exposures to environmental chemicals and related stressors, such as airborne particulate matter. There is an opportunity for exposure science to contribute more substantially to improving public health by devoting more attention to microorganisms as key stressors and agents in exposure. The discovery that pathogenic microbes cause disease in humans precipitated a revolution in public health science and disease prevention. With a continued global urgency to address spread of pathogenic microbes, contributions of microorganisms to both infectious and noninfectious processes merit more attention from the exposure science community. Today, discoveries of the importance of the human microbiome as a determinant of health and disease are precipitating a second revolution. Emerging knowledge creates a major opportunity to expand the scope of exposure science to incorporate the human microbiome as a target and modulator of exposure. A study committee of the National Academies of Sciences, Engineering, and Medicine has defined a research strategy to address health risks that pertain to the interaction of environmental chemicals with the human microbiome. Some aspects of this strategy pose important challenges and opportunities for the exposure science community.

Risk assessment of endocrine disrupting phthalates and hormonal alterations in children and adolescents

Risk assessment and hormone evaluation were carried out for di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP), endocrine disrupting chemicals (EDCs), in 302 Korean children (n = 223) and adolescents (n = 79) (< age 19). Urinary and serum concentrations of DEHP, MEHP (mono(2-ethylhexyl) phthalate), DBP, MBP (monobutyl phthalate), and PA (phthalic acid, a common final metabolite of phthalates) were detected in children and adolescents. Daily exposure levels were estimated to be 16.45 ± 36.50 μg/kg b.w./day for DEHP, which is one-third of the tolerable daily intake (TDI) value (50 μg/kg b.w./day), but 14 out of 302 participants had a hazard index (HI = intake/TDI) value >1. The mean daily exposure level of DBP was 1.23 ± 1.45 μg/kg b.w./day, which is one-eighth of the TDI value (10 μg/kg b.w./day), but 1 out of 302 participants had a HI value > 1. Positive correlations were observed between serum DBP or MEHP, and serum estradiol (E2) and/or luteinizing hormone (LH) in prepubescent children. In addition, serum MBP levels were found to be negatively correlated with serum triiodothyronine (T3) or thyroxine (T4) in male participants, and serum DEHP levels with serum thyroid stimulating hormone (TSH) in female adolescents. Low-density lipoprotein (LDL) levels were positively correlated with serum PA levels in children and adolescents. DEHP, DBP or its metabolites may be associated with altered hormone levels in children and adolescents. Data suggest that exposure levels of DEHP and DBP in Korean children need to be reduced to levels below TDI to protect them from EDC-mediated toxicities. Abbreviations: DBP: dibutyl phthalate; DEHP: di(2-ethylhexyl) phthalate; E2: estradiol; EDC: endocrine disrupting chemical; EFSA: European Food Safety Authority; FSH: follicle stimulating hormone; HDL: high density lipoprotein; HI: hazard index; LDL: low density lipoprotein; LH: luteinizing hormone; MEHP: mono(2-ethylhexyl) phthalate; MBP: monobutyl phthalate; PA: phthalic acid; PPAR: peroxisome proliferator-activated receptor gamma; PVC: polyvinyl chloride; T3: triiodothyronine; T4: thyroxine; TDI: tolerable daily intake; TG: triglyceride; TSH: thyroid stimulating hormone; UPLC/MS/MS: Ultra Performance Liquid Chromatography/Tandem Mass Spectrometry; WWF: World Wildlife Fund.

Inhalation and Dermal Uptake of Particle and Gas-Phase Phthalates-A Human Exposure Study

Phthalates are ubiquitous in indoor environments, which raises concern about their endocrine-disrupting properties. However, studies of human uptake from airborne exposure are limited. We studied the inhalation uptake and dermal uptake by air-to-skin transfer with clean clothing as a barrier of two deuterium-labeled airborne phthalates: particle-phase D₄-DEHP (di(2-ethylhexyl)phthalate) and gas-phase D₄-DEP (diethyl phthalate). Sixteen participants, wearing trousers and long-sleeved shirts, were under controlled conditions exposed to airborne phthalates in four exposure scenarios: dermal uptake alone and combined inhalation + dermal uptake of both phthalates. The results showed an average uptake of D₄-DEHP by inhalation of 0.0014 ± 0.00088 (μg kg^-1 bw)/(μg m^-3)/h. No dermal uptake of D₄-DEHP was observed during the 3 h exposure with clean clothing. The deposited dose of D₄-DEHP accounted for 26% of the total inhaled D₄-DEHP mass. For D₄-DEP, the average uptake by inhalation + dermal was 0.0067 ± 0.0045 and 0.00073 ± 0.00051 (μg kg^-1 bw)/(μg m^-3)/h for dermal uptake. Urinary excretion factors of metabolites after inhalation were estimated to 0.69 for D₄-DEHP and 0.50 for D₄-DEP. Under the described settings, the main uptake of both phthalates was through inhalation. The results demonstrate the differences in uptake of gas and particles and highlight the importance of considering the deposited dose in particle uptake studies.

Temporal Trends in Exposures to Six Phthalates from Biomonitoring Data: Implications for Cumulative Risk

Phthalates are used in a wide range of consumer goods, resulting in exposures to specific phthalates that vary over time in accordance with changes in product use and how phthalates are utilized. We investigated trends in estimates of daily intake dose and several cumulative risk metrics, including the Hazard Quotient (HQ), Hazard Index (HI), and Maximum Cumulative Ratio (MCR) for six phthalates from 2005 to 2014 using metabolite biomonitoring data collected from spot urine samples under the National Health and Nutrition Examination Survey (NHANES). Over this period, there was a 2.2-fold decrease in the mean HI (0.34 to 0.15) and a 7.2-fold decrease in the percentage of participants with an HI > 1 (5.7% to 0.8%), indicating an overall decrease in combined exposure to these phthalates. Children (aged 6-11 years) had higher mean HI values than either adolescents (aged 12-19 years) or adults (aged 20+ years) during this period. MCR values were generally low and inversely correlated with HI. This indicated that a single phthalate usually drove the hazards for highly exposed individuals. However, the average value of MCR increased 1.2-fold (1.7-2.1) over this period indicating an increasing need to consider exposures to multiple phthalates in this group.

Mechanistic toxicity of DEHP at environmentally relevant concentrations (ERCs) and ecological risk assessment in the Three Gorges Reservoir Area, China

Di-(2-ethylhexyl) phthalate (DEHP) associated in vitro/vivo toxicity at current environmentally relevant concentration (ERC) with attendant ecological risks in the Three Gorges Reservoir Area (TGRA) is still elusive. Responding to this challenge, a novel integrated study based on analytical and biological assays was designed to elucidate the underlying mechanisms for toxicity of DEHP and its ecological risks at ERC. In this study, GC-MS analysis showed that the highest environmental concentration of DEHP in the TGRA surface water was nearly double that of WHO and USEPA standards. Both distribution and ecological risk decreased from the upper to middle and lower reaches of the TGRA. In vitro toxicity was assessed by cell viability and DNA damage assays: DEHP exposure at ERCs (100-800 μg/L) caused significant reduction in cell viability and elevated DNA damage. Further, DEHP exposure above 400 μg/L resulted in enhanced migration behavior of cancer cells. For in vivo toxicity assessment, short term acute exposure (7 d, 400 μg/L) apparently activated the PI3K-AKT-mTOR pathway, and chronic low-level exposure (3 months, 10-33 μg/L) suppressed the hypothalamus pituitary thyroid (HPT) axis pathway in zebrafish. In addition, acute low-level exposure (5 d, 33-400 μg/L) to DEHP increased aryl hydrocarbon receptor (AhR) activity in Tg(cyp1a:gfp) zebrafish in a concentration-dependent manner. In short, DEHP at ERC has extended potential to induce diverse in vitro and in vivo toxicity at concentrations that also cause impairment of biochemical function in aquatic species of the TGRA.

Endocrine disruptor responses in African sharptooth catfish (Clarias gariepinus) exposed to di-(2-ethylhexyl)-phthalate

In the present study, we have investigated the endocrine disruptive effects of waterborne di-(2-ethylhexyl) phthalate (DEHP: 0 (control), 10, 100, 200 and 400 μg/L) on juvenile Clarias gariepinus by analyzing transcript patterns for hepatic vitellogenin (vtg), estrogen receptor-α (er-α), aromatase (cyp19a1b) and peroxisome proliferator activated receptor-α (ppar-α) using quantitative real-time PCR after 3, 7 and 14 days exposure period. In addition, we analyzed CYP19 and PPAR protein levels using enzyme-linked immunosorbent assay (ELISA), while cellular testosterone (T) and 17β-estradiol (E2) levels were measured using enzyme immune assay (EIA). Tissue burden of DEHP was measured in the liver using gas chromatography-mass spectroscopy (GC-MS). We observed apparent concentration- and time-dependent increases of vtg, er-α, cyp19a1b transcripts, E2 and T levels after exposure to DEHP. A biphasic pattern of effect was observed for ppar-α, showing a concentration-dependent increase that peaked at 100 μg/L and thereafter, an apparent concentration-dependent decrease at 200 and 400 μg/L at all exposure days. Given that the post-differentiation changes of gonads in C. gariepinus corresponded with the 14-day sampling period, we separated the analyzed data into sexes after histological examination of the gonads, showing that females responded stronger, compared to males, to DEHP exposure at all exposure concentrations. Oocyte atresia, intersex (ovotestis) and karyoplasmic clumping were observed in females while male fish showed distortion and degeneration of seminiferous tubules and condensation of tubular cells in the 400 μg/L exposure group after 14 days. Corresponding canonical analysis (CCA) of all analyzed variables revealed a positive relationship between analyzed biological variables with increasing DEHP concentrations. Overall, molecular, biochemical and physiological responses presented in the present study indicate that exposure of C. gariepinus to waterborne DEHP produced endocrine disruptive responses with potential consequences for overt reproduction, development, physiology and general health of fish populations inhabiting phthalate contaminated aquatic environments. These responses represent valuable and effective biomarkers of exposure and effects, that can be adopted for screening the presence of EDCs in Nigeria and other developing countries.

Hydrolysis of di(2-ethylhexyl) phthalate in humans, monkeys, dogs, rats, and mice: An in vitro analysis using liver and intestinal microsomes

Di(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer that is rapidly metabolized to mono(2-ethylhexyl) phthalate (MEHP), an active metabolite, in mammals. In the present study, the hydrolysis of DEHP by the liver and intestinal microsomes of humans, monkeys, dogs, rats, and mice was examined. The kinetics of liver microsomes fit the Michaelis-Menten model for humans, monkeys, and rats, and the Hill model for dogs and mice. K_m or S₅₀ values were similar among species, whereas V_max exhibited species differences of approximately 9-fold. CL_int or CL_max values were in the order of mice > dogs > monkeys ≥ rats > humans. Hydrolytic activity towards DEHP was not detected in the intestinal microsomes of humans or dogs. The kinetics of monkeys, rats, and mice followed the Hill model. In comparisons of the liver microsomes of each species, S₅₀ values were similar, while V_max and CL_max values (mice > rats > monkeys) were considerably lower (approximately 5-25%). These results suggest that hydrolytic activity towards DEHP in the liver and intestines markedly differ among humans and non-rodent and rodent experimental animals, and imply that species differences are closely associated with the toxicity of DEHP.

Occupational exposure assessment of phthalate esters in indoor and outdoor microenvironments

Phthalate esters (PAEs) are widely used as plasticizers in consumer products. PAEs are a group of environmental hormone which disrupts human and animals' endocrine systems. Different occupational groups are exposed to various levels of PAEs. In the present study, four typical occupational groups were chosen, including doctors, college teachers, college students, and drivers who worked in public traffic system. In order to understand the exposure levels to PAEs via inhalation, air samples were collected from multiple microenvironments including indoor and outdoor in Hangzhou to measure the gas and particle concentrations of six PAEs, together with time spent in different microenvironments of these four groups. A comprehensive PAEs exposure model was built to estimate the daily PAEs exposure through inhalation, oral and dermal pathways. The Monte Carlo simulation results show that doctors were exposed to the highest level of PAEs, and consequently had the highest health risk among these four occupational groups. In contrast, college students had the lowest health risk. By setting the exposure level of staying in residences as the baseline, doctors and drivers were two occupations exposed to high PAEs health risk. Di-(2-ethylhexyl) phthalate (DEHP) was the largest contributor among the six phthalates, posing moderate health risk (10^-5-10^-6) to every occupation. For traffic microenvironments alone, the total exposure levels for different transportation modes were in the descending order of busses, cars, cabs, tubes, motor bikes, and walking.