Kinetics of di(2-ethylhexyl) phthalate (DEHP) and mono(2-ethylhexyl) phthalate in blood and of DEHP metabolites in urine of male volunteers after single ingestion of ring-deuterated DEHP

Maslinic acid supplementation prevents di(2-ethylhexyl) phthalate-induced apoptosis via PRDX6 in peritubular myoid cells of Chinese forest musk deer

Chinese forest musk deer (FMD), an endangered species, have exhibited low reproductive rates even in captivity due to stress conditions. Investigation revealed the presence of di(2-ethylhexyl) phthalate (DEHP), an environmental endocrine disruptor, in the serum and skin of captive FMDs. Feeding FMDs with maslinic acid (MA) has been observed to alleviate the stress response and improve reproductive rates, although the precise molecular mechanisms remain unclear. Therefore, this study aims to investigate the molecular mechanisms underlying the alleviation of DEHP-induced oxidative stress and cell apoptosis in primary peritubular myoid cells (PMCs) through MA intake. Primary PMCs were isolated and exposed to DEHP in vitro. The results demonstrated that DEHP significantly suppressed antioxidant levels and promoted cell apoptosis in primary PMCs. Moreover, interfering with the expression of PRDX6 was found to induce excessive reactive oxygen species (ROS) production and cell apoptosis in primary PMCs. Supplementation with MA significantly upregulated the expression of PRDX6, thereby attenuating DEHP-induced oxidative stress and cell apoptosis in primary PMCs. These findings provide a theoretical foundation for mitigating stress levels and enhancing reproductive capacity of in captive FMDs.

Understanding the Impacts of Presystemic Metabolism on the Human Oral Bioavailability of Chemicals

Animal-free new approach methods promote chemical assessments based on the comparison between in vitro bioactivity and human internal concentrations, which necessitates a dependable knowledge of human oral bioavailability, i.e., the fraction of an orally ingested chemical that escapes from presystemic ("first-pass") metabolic processes and eventually enters systemic circulation. Using a physiologically based toxicokinetic model, we show how human oral bioavailability is impacted by presystemic metabolism within the gut lumen, gut wall, and liver and how this impact differs among chemicals with various permeability and stability properties. Our results highlight the gut lumen as a primary site of presystemic metabolism of certain chemicals, such as di-2-ethylhexyl phthalate (DEHP), for which the gut lumen may even exceed the liver in importance of presystemic metabolism due to these metabolic processes occurring in sequence. For chemicals with low transmembrane permeability and low stability, metabolism within the gut lumen is the most remarkable of the three presystemic metabolic processes. Notably, for chemicals that undergo substantial metabolism within the gut lumen, where the metabolites have high permeability, there is a notable discrepancy between the "theoretical bioavailability" (bioavailability of the unchanged parent compound) and the "apparent bioavailability" in measurement practices (bioavailability inferred from measured metabolites). Our work highlights the importance of considering presystemic metabolism, notably within the gut lumen, in human exposure and toxicokinetic modeling.

Human skin absorption of three phthalates

Population studies reveal widespread exposure to phthalates. Understanding their absorption, distribution, metabolism, and excretion is vital to reduce exposure. However, data on skin absorption remain limited. We thus aim to characterize the skin permeation of three phthalates in a mixture, neat or in emulsion; di(2-ethylhexyl) phthalate (d4-DEHP), dibutyl phthalate (d4-DBP), and diethyl phthalate (d4-DEP), by comparing in vitro human skin (800 µm) permeation (24 hours) results using flow-through diffusion cells with urine results obtained from volunteers exposed to the same mixture applied to a forearm (40 cm2). Metabolites were analyzed in receptor fluids and urine. Phthalates crossed the skin barrier and metabolized into monoesters before elimination. Increased permeation was observed for phthalates in emulsion compared to neat substances, with polyethylene glycol (PEG) in the receptor fluid enhancing emulsion permeation, but not affecting neat substances. In vitro results mirrored in vivo findings: DEP showed rapid permeation (J: ∼2 ug/cm2/h) and urinary excretion peaking at six hours post-application, whereas DBP exhibited slower kinetics (J: ∼0.1 ug/cm2/h), with a urinary peak at 15-17 hours post-application. DEHP had minimal permeation (J: ∼0.0002 ug/cm2/h) with no observable urinary peak. These findings underscore the importance of comprehending phthalate skin absorption for effective exposure mitigation strategies.

Prevalence and clinical implications of heightened plastic chemical exposure in pediatric patients undergoing cardiopulmonary bypass

BACKGROUND

Phthalate chemicals are used to manufacture plastic medical products, including many components of cardiopulmonary bypass (CPB) circuits. We aimed to quantify iatrogenic phthalate exposure in pediatric patients undergoing cardiac surgery and examine the link between phthalate exposure and postoperative outcomes.

STUDY DESIGN AND METHODS

The study included pediatric patients undergoing (n=122) unique cardiac surgeries at Children's National Hospital. For each patient, a single plasma sample was collected preoperatively and two additional samples were collected postoperatively upon return from the operating room and the morning after surgery. Concentrations of di(2-ethylhexyl) phthalate (DEHP) and its metabolites were quantified using ultra high-pressure liquid chromatography coupled to mass spectrometry.

RESULTS

Patients were subdivided into three groups, according to surgical procedure: (1) cardiac surgery not requiring CPB support, (2) cardiac surgery requiring CPB with a crystalloid prime, and (3) cardiac surgery requiring CPB with red blood cells (RBCs) to prime the circuit. Phthalate metabolites were detected in all patients, and postoperative phthalate levels were highest in patients undergoing CPB with an RBC-based prime. Age-matched (<1 year) CPB patients with elevated phthalate exposure were more likely to experience postoperative complications. RBC washing was an effective strategy to reduce phthalate levels in CPB prime.

DISCUSSION

Pediatric cardiac surgery patients are exposed to phthalate chemicals from plastic medical products, and the degree of exposure increases in the context of CPB with an RBC-based prime. Additional studies are warranted to measure the direct effect of phthalates on patient health outcomes and investigate mitigation strategies to reduce exposure.

Di-(2-ethylhexyl) phthalate exposure induces premature testicular senescence by disrupting mitochondrial respiratory chain through STAT5B-mitoSTAT3 in Leydig cell

Di-(2-ethylhexyl) phthalate (DEHP), a prevalent plasticizer, is known to have endocrine-disrupting effects on males and cause reproductive toxicity. There were causal effects of DEHP on testosterone levels in the real world by Mendelian randomization analysis. Exposure to DEHP during the preadult stage might lead to premature testicular senescence, but the mechanisms responsible for this have yet to be determined. In this study, we administered DEHP (300 mg/kg/day) to male C57BL/6 mice from postnatal days 21 to 49. The mice were kept for 6 months without DEHP. RNA sequencing was conducted on testicular tissue at PNM6. The results indicated that DEHP hindered testicular development, lowered serum testosterone levels in male mice, and induced premature testicular senescence. TM3 Leydig cells were exposed to 300 μM of mono(2-ethylhexyl) phthalate (MEHP), the bioactive metabolite of DEHP, for 72 h. The results also found that DEHP/MEHP induced senescence in vivo and in vitro. The mitochondrial respiratory chain was disrupted in Leydig cells. The expression and stability of STAT5B were elevated by MEHP treatment in TM3 cells. Furthermore, p-ERK1/2 was significantly decreased by STAT5B, and mitochondria-STAT3 (p-STAT3 ser727) was significantly decreased due to the decrease of p-ERK1/2. Additionally, the senescence level of TM3 cells was decreased and treated with 5 mM NAC for 1 h after MEHP treatment. In conclusion, these findings provided a novel mechanistic understanding of Leydig cells by disrupting the mitochondrial respiratory chain through STAT5B-mitoSTAT3.

Environmentally relevant DEHP exposure during gestational and lactational period inhibits filamin a testicular expression

Toxicological studies have revealed that DEHP exposure during pregnancy may induce developmental disorders, especially in male offspring, leading to morphological and functional alterations in the reproductive system by mechanisms that should be investigated. Thus, the aim of this work was to analyze the testicular toxicity induced by an environmentally relevant DEHP dose during development and its impact on FLNA, a protein that participates in the blood-testis barrier assembly. We used male Wistar rats exposed to DEHP during pregnancy and lactation. The results showed that DEHP exposure during development and lactation increased body weight, decreased gonadal weight and shortened anogenital distance. This phthalate induced morphological changes in the testis, suggestive of hypospermatogenesis. DEHP exposure decreased the number of FLNA positive cells and the expression of FLNA and claudin-1 in prepubertal testes. Furthermore, DEHP inhibited FLNA and claudin-1 protein expression in adult male rats. These results indicated that exposure to DEHP during gestation and lactation perturbed testis development and suggested that FLNA is a target protein of DEHP, possibly contributing to the phthalate-induced damage on BTB.

Distribution of phthalate metabolites, benzophenone-type ultraviolet filters, parabens, triclosan and triclocarban in paired human hair, nail and urine samples

In this study, the distribution of nineteen ingredients of personal care product (PCPs), including seven metabolites of phthalates (mPAEs), five benzophenone-type ultraviolet filters (BPs), and seven antimicrobial agents (AAs), were investigated in paired human hair, nail and urine samples. The median concentrations of ΣmPAEs, ΣBPs and ΣAAs were 135, 2.76 and 179 ng/g in hair, 37.3, 2.95 and 297 ng/g in nails, and 345, 4.03 and 50.1 ng/mL in urine, respectively. Mono-methyl phthalate (49%), 2,4-dihydroxybenzophenone (45%) and triclosan (71%) were the most abundant mPAE, BP and AA in hair samples, respectively, and had similar abundance in nail samples. In contrast, mono-n-butyl phthalate (45%), 4-hydroxy benzophenone (29%) and methyl paraben (54%) were the predominant mPAE, BP and AA in urine samples, respectively. Significant differences in the concentrations of some target compounds were observed between male and female but inconsistent across different matrices. Moreover, most compounds with significant correlations had quite different correlation coefficients in each matrix. No significant correlations were found between hair, nail and urine samples for most of the target analytes. These results suggest these analytes have matrix-specific distribution, and it is necessary to use multiple matrices to comprehensively assess the risk of ingredients of PCPs to human health.

Human metabolism and excretion kinetics of the surfactant 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) after oral and dermal administration

2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant with a wide range of applications. TMDD is considered a high-production chemical and, due to its low biodegradation rate, possesses a potentially high prevalence in the environment. However, despite its widespread use, toxicokinetic data and data on internal exposure to TMDD in the general population are completely lacking. Hence, we developed a human biomonitoring (HBM) method for TMDD. Our approach included a metabolism study with four subjects, who were administered an oral dose of 75 µg TMDD/kg body weight and a dermal dose of 750 µg/kg body weight. Terminal methyl-hydroxylated TMDD (1-OH-TMDD) was previously identified as the main urinary metabolite in our lab. The results of the oral and dermal applications were used to determine the toxicokinetic parameters of 1-OH-TMDD as a biomarker of exposure. Finally, the method was applied to 50 urine samples from non-occupationally exposed volunteers. Results show that TMDD was rapidly metabolized, with an average tmax of 1.7 h and a rapid and almost complete (96%) excretion of 1-OH-TMDD until 12 h after oral dosage. Elimination was bi-phasic, with half-lives of 0.75-1.6 h and 3.4-3.6 h for phases 1 and 2, respectively. The dermal application resulted in a delayed urinary excretion of this metabolite with a tmax of 12 h and complete excretion after about 48 h. The excreted amounts of 1-OH-TMDD represented 18% of the orally administered TMDD dose. The data of the metabolism study demonstrated a fast oral as well as substantial dermal resorption of TMDD. Moreover, the results indicated an effective metabolism of 1-OH-TMDD, which is excreted rapidly and completely via urine. Application of the method to 50 urine samples revealed a quantification rate of 90%, with an average concentration of 0.19 ng/mL (0.97 nmol/g creatinine). With the urinary excretion factor (Fue) derived from the metabolism study, we estimated an average daily intake of 1.65 µg TMDD from environmental and dietary sources. In conclusion, 1-OH-TMDD in urine is a suitable biomarker of exposure to TMDD and can be applied for biomonitoring of the general population.

Phthalates and phthalate metabolites in urine from Tianjin and implications for platelet mitochondrial DNA methylation

Background

Phthalates (PAEs) are important synthetic substances in plastics, attracting much attention due to their potential effects on the cardiovascular system.

Methods

In this study, urine and blood samples from 39 individuals were collected in Tianjin, China. Phthalates and phthalate metabolites (mPAEs) were analyzed using gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-mass spectrometry (HPLC-MS), respectively. The polymerase chain reaction (PCR) products from bisulfite-treated mitochondrial DNA (mtDNA) samples were analyzed using pyrosequencing technology.

Results

The detection frequencies for 9 PAEs varied from 2.56 to 92.31%, and those for 10 mPAEs varied from 30.77 to 100%. The estimated daily intakes (EDIs) and cumulative risk of PAEs were calculated based on the experimental statistics of urinary PAEs and mPAEs. For PAEs, the HIRfD (hazard index corresponding to reference doses) values of 10.26% of participants and the HITDI (hazard index corresponding to tolerable daily intake) values of 30.77% of participants were estimated to exceed 1, suggesting a relatively high exposure risk. The mtDNA methylation levels in the MT-ATP8 and MT-ND5 were observed to be lower than in the MT-ATP6. Mono-ethyl phthalate (MEP) and MT-ATP8 were positively correlated with triglyceride levels (p < 0.05). Based on the association of PAEs, mtDNA methylation, and triglycerides, the mediating role of mtDNA methylation between PAEs and cardiovascular diseases (CVDs) was analyzed in this study, but no mediated effect was observed.

Conclusion

The effects of PAE exposure on cardiovascular diseases (CVDs) should be investigated further.

Toxicoproteomics of Mono(2-ethylhexyl) phthalate and Perfluorooctanesulfonic Acid in Models of Prostatic Diseases

Benign and malignant prostatic diseases are common, costly, and burdensome; moreover, they share fundamental underlying molecular processes. Several ubiquitous contaminants may perturb these processes, possibly via peroxisome proliferator-activated receptor (PPAR) signaling, but the role of environmental exposures─particularly mixtures─in prostatic diseases is undefined. In the present study, nontumorigenic prostate stromal cells and metastatic prostate epithelial cells were exposed to ubiquitous exogenous PPAR ligands under different dosing paradigms, including a mixture, and effects were assessed via mass spectrometry-based global proteomics. In prostate stromal cells, environmentally relevant levels of mono(2-ethylhexyl) phthalate (MEHP), alone and in combination with perfluorooctanesulfonic acid, led to significant changes in proteins involved in key processes underlying prostatic diseases: oxidative stress defense, proteostasis, damage-associated molecular pattern signaling, and innate immune response signaling. A follow-up experiment in metastatic prostate epithelial cells showed that the occupationally relevant levels of MEHP perturbed similar processes, including lipid, cholesterol, steroid, and alcohol metabolism; apoptosis and coagulation regulation; wound response; and aging. This work shows that environmental exposures may contribute to prostatic diseases by perturbing key processes of a proposed adverse outcome pathway, including lipid metabolism, oxidative stress, and inflammation. Future in vivo research will investigate the role of contaminants in prostatic diseases and in preventative agents.

Refinement and calibration of a human PBPK model for the plasticiser, Di-(2-propylheptyl) phthalate (DPHP) using in silico, in vitro and human biomonitoring data

An existing physiologically based pharmacokinetic model for Di-(2-propylheptyl) phthalate (DPHP) was refined to improve the simulations of the venous blood concentrations of the primary monoester metabolite, mono-(2-propylheptyl) phthalate (MPHP). This was considered a significant deficiency that should be addressed because the primary metabolite of other high molecular weight phthalates has been associated with toxicity. The various processes that influence the concentration of DPHP and MPHP in blood were re-evaluated and modified. A few simplifications of the existing model were made, including the removal of enterohepatic recirculation (EHR) of MPHP. However, the primary development was describing the partial binding of MPHP to plasma proteins following uptake of DPHP and metabolism in the gut affording better simulation of the trends observed in the biological monitoring data. Secondly, the relationship between blood concentrations and the urinary excretion of secondary metabolites was explored further because the availability of two data streams provides a better understanding of the kinetics than reliance on just one. Most human studies are conducted with few volunteers and generally with the absence of blood metabolite measurements which would likely imply an incomplete understanding of the kinetics. This has important implications for the "read across" approach proposed as part of the development of New Approach Methods for the replacement of animals in chemical safety assessments. This is where the endpoint of a target chemical is predicted by using data for the same endpoint from another more "data rich" source chemical. Validation of a model parameterized entirely with in vitro and in silico derived parameters and calibrated against several data streams would constitute a data rich source chemical and afford more confidence for future evaluations of other similar chemicals using the read-across approach.

Identification of serum metabolic signatures of environmental-leveled phthalate in the Taiwanese child population using NMR-based metabolomics

Phthalates have become important environmental pollutants due to their high exposure frequency in daily life; thus, phthalates are prevalent in humans. Although several epidemiologic surveys have linked phthalates with several adverse health effects in humans, the molecular events underlying phthalate exposure have not been fully elucidated. The purpose of this study was to reveal associations between phthalate exposure and the serum metabolome in Taiwanese children using a metabolomic approach. A total of 256 Taiwanese children (8-10 years old) from two cohorts were enrolled in this study. Twelve urinary phthalate metabolites were analyzed by high-performance liquid chromatography/tandem mass spectrometry, while a nuclear magnetic resonance-based metabolomic approach was used to record serum metabolic profiles. The associations between metabolic profiles and phthalate levels were assessed by partial least squares analysis coupled with multiple linear regression analysis. Our results revealed that unique phthalate exposures, such as mono-isobutyl phthalate, mono-n-butyl phthalate, and mono (2-ethyl-5-oxohexyl) phthalate, were associated with distinct serum metabolite profiles. These phthalate-mediated metabolite changes may be associated with perturbed energy mechanisms, increased oxidative stress, and lipid metabolism. In conclusion, this study suggests that metabolomics is a valid approach to examine the effects of environmental-level phthalate on the serum metabolome. This study also highlighted potentially important phthalates and their possible effects on children.

Development, testing, parameterisation, and calibration of a human PBK model for the plasticiser, di (2-ethylhexyl) adipate (DEHA) using in silico, in vitro and human biomonitoring data

Introduction: A physiologically based biokinetic model for di (2-ethylhexyl) adipate (DEHA) based on a refined model for di-(2-propylheptyl) phthalate (DPHP) was developed to interpret the metabolism and biokinetics of DEHA following a single oral dosage of 50 mg to two male and two female volunteers. Methods: The model was parameterized using in vitro and in silico methods such as, measured intrinsic hepatic clearance scaled from in vitro to in vivo and algorithmically predicted parameters such as plasma unbound fraction and tissue:blood partition coefficients (PCs). Calibration of the DEHA model was achieved using concentrations of specific downstream metabolites of DEHA excreted in urine. The total fractions of ingested DEHA eliminated as specific metabolites were estimated and were sufficient for interpreting the human biomonitoring data. Results: The specific metabolites of DEHA, mono-2-ethyl-5-hydroxyhexyl adipate (5OH-MEHA), mono-2-ethyl-5-oxohexyl adipate (5oxo-MEHA), mono-5-carboxy-2-ethylpentyl adipate (5cx-MEPA) only accounted for ∼0.45% of the ingested DEHA. Importantly, the measurements of adipic acid, a non-specific metabolite of DEHA, proved to be important in model calibration. Discussion: The very prominent trends in the urinary excretion of the metabolites, 5cx-MEPA and 5OH-MEHA allowed the important absorption mechanisms of DEHA to be modelled. The model should be useful for the study of exposure to DEHA of the general human population.

Development, testing, parameterisation, and calibration of a human PBPK model for the plasticiser, di-(2-ethylhexyl) terephthalate (DEHTP) using in silico, in vitro and human biomonitoring data

A physiologically based pharmacokinetic model for di-(2-ethylhexyl) terephthalate (DEHTP) based on a refined model for di-(2-propylheptyl) phthalate (DPHP) was developed to interpret the metabolism and biokinetics of DEHTP following a single oral dose of 50 mg to three male volunteers. In vitro and in silico methods were used to generate parameters for the model. For example, measured intrinsic hepatic clearance scaled from in vitro to in vivo and plasma unbound fraction and tissue:blood partition coefficients (PCs) were predicted algorithmically. Whereas the development and calibration of the DPHP model was based upon two data streams, blood concentrations of parent chemical and first metabolite and the urinary excretion of metabolites, the model for DEHTP was calibrated against a single data stream, the urinary excretion of metabolites. Despite the model form and structure being identical significant quantitative differences in lymphatic uptake between the models were observed. In contrast to DPHP the fraction of ingested DEHTP entering lymphatic circulation was much greater and of a similar magnitude to that entering the liver with evidence for the dual uptake mechanisms discernible in the urinary excretion data. Further, the absolute amounts absorbed by the study participants, were much higher for DEHTP relative to DPHP. The in silico algorithm for predicting protein binding performed poorly with an error of more than two orders of magnitude. The extent of plasma protein binding has important implications for the persistence of parent chemical in venous blood-inferences on the behaviour of this class of highly lipophilic chemicals, based on calculations of chemical properties, should be made with extreme caution. Attempting read across for this class of highly lipophilic chemicals should be undertaken with caution since basic adjustments to PCs and metabolism parameters would be insufficient, even when the structure of the model itself is appropriate. Therefore, validation of a model parameterized entirely with in vitro and in silico derived parameters would need to be calibrated against several human biomonitoring data streams to constitute a data rich source chemical to afford confidence for future evaluations of other similar chemicals using the read-across approach.

Simultaneous and sensitive determination of the main metabolites of the plasticizer DEHP and its substitutes DEHTP, DINCH and TEHTM in human urine by coupling of on-line SPE, UHPLC and tandem mass spectrometry

With the prominent but toxicologically critical plasticizer di-(2-ethylhexyl) phthalate (DEHP) declining, alternative plasticizers are increasingly used leading to a continuously more diverse exposure situation of humans with multiple plasticizers. Therefore, an on-line SPE-LC-MS/MS method for the simultaneous determination of the most relevant urinary biomarkers of exposure to DEHP and the alternative plasticizers 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), di-(2-ethylhexyl) terephthalate (DEHTP) and tri-(2-ethylhexyl) trimellitate (TEHTM) was developed. The method is characterized by a high sensitivity with limits of detection ranging from 0.006 to 0.047 μg L^-1 combined with an easy and straightforward sample preparation procedure. The wide linear working range of the method enables a reliable determination of analyte background levels in the general population as well as its potential use for monitoring studies investigating elevated plasticizer exposure settings. The method was successfully applied to urine samples from ten volunteers without occupational exposure to plasticizers revealing ubiquitous background exposure levels of the common plasticizers DEHP, DEHTP and DINCH.

Relationship of individual and mixed prenatal phthalate exposure with placental structure and efficiency in the prospective Ma'anshan Birth Cohort Study

BACKGROUND

Few studies have investigated the associations between prenatal phthalate exposure and placental structure and function with inconsistent conclusions.

METHODS

Nested on the Ma'anshan Birth Cohort study, 2723 women provided spot urine samples during the first, second and third trimesters of pregnancy to analyze six phthalate metabolites. The outcomes of interest were placental weight, efficiency (birth weight/placental weight), chorionic disc area and disc eccentricity. The relationships of prenatal exposure to a single phthalate with placental measures were analyzed. The associations between prenatal phthalate mixture exposure and placental measures were also evaluated.

RESULTS

Most phthalate metabolites were significantly associated with placental weight, efficiency and chorionic disc area during the whole gestation and in each trimester of pregnancy, with different directions of relationships. Sensitivity analyses revealed similar findings, indicating the robustness of the statistical results. Furthermore, inverted U-shaped nonlinear relationships of prenatal exposure to some phthalate metabolites with placental weight, efficiency and chorionic plate area were observed. However, quantile g-computation mixture models did not reveal any association between maternal combined exposure to the total phthalate metabolites and placental measures.

CONCLUSIONS

Maternal exposure to most phthalates and their metabolites was associated with placental weight, efficiency and chorionic plate area in both a linear manner and an inverted U-shaped nonlinear manner. However, the mixture of multiple phthalate metabolites was not observed to be associated with any placental measure.

Comparison of the exposure assessment of di(2-ethylhexyl) phthalate between the PBPK model-based reverse dosimetry and scenario-based analysis: A Korean general population study

Di (2-ethylhexyl) phthalate (DEHP), classified as a reproductive toxicant, is a ubiquitous pollutant in foodstuffs, dust, and commercial products. In this study, to provide a useful cross-check on the accuracy of the exposure assessment, the estimated daily intake of DEHP was compared using reverse dosimetry with a physiologically-based pharmacokinetic (PBPK) model and a scenario-based probabilistic estimation model for six subpopulations in Korea. For reverse dosimetry analysis, the concentrations of urinary DEHP metabolites, namely mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl)phthalate (MEOHP), from three human biomonitoring program datasets were used. For the scenario-based model, we evaluated the various exposure sources of DEHP, including diet, air, indoor dust, soil, and personal care products (PCPs), and also determined its levels based on the literature review and measurements of indoor dust. The DEHP exposure doses using both exposure assessment approaches were similar in all cases, except for the 95th percentile exposure doses in toddlers (1-2 years) and young children (3-6 years). The PBPK-reverse dosimetry estimated daily intakes at the 95th percentile ranged between 22.53 and 29.90 μg/kg/day for toddlers and young children. These exceeded the reference dose (RfD) of 20 μg/kg bw/day of the US Environmental Protection Agency (EPA) based on the increased relative liver weight. Although, food was considered the primary source of DEHP, contributing to a total exposure of 50.8-75.1%, the effect of exposure to indoor dust should not be overlooked. The occurrence of high levels of DEHP in indoor dust collected from Korean homes suggests the use of a wide variety of consumer products containing DEHP. Furthermore, more attention should be paid to the high exposure levels of DEHP, especially in young children. Therefore, it is necessary to perform continuous monitoring of the indoor dust, consumer products, and the body burden of children.

Toxicokinetics of mono-(2-ethylhexyl) phthalate with low-dose exposure applying fluorescence tracing technique

Di(2-ethylhexyl) phthalate (DEHP) belongs to environmental endocrine disrupting chemicals (EEDCs) and can be rapidly hydrolyzed into the ultimate toxicant mono-2-ethylhexyl phthalate (MEHP). In this study, we used 5-aminofluorescein modified MEHP (MEHP-AF) as a fluorescence tracer to explore the toxicokinetics, including toxicokinetic parameters, absorption and transport across the intestinal mucosal barrier, distribution and pathological changes of organs. While the dose was as lower than 10 mg/kg by intragastric administration, the toxicokinetic parameters obtained by fluorescence microplate method were similar to those with the literatures by chromatography. MEHP-AF can be rapidly absorbed through the intestinal mucosal barrier in rats. In situ organ distribution in mice showed that MEHP-AF was mainly concentrated in the liver, kidney and testis. Our results suggested that the fluorescence tracing technique had the advantages with easy processing, less time-consuming, higher sensitivity for the quantitative determination, In addition, this technology also avoids the interference of exogenous or endogenous DEHP and MEHP in the experimental system. It also can be utilized to the visualization detection of MEHP in situ localization in the absorption organ and the toxic target organ. The results show that this may be a more feasible MEHP toxicological research method.

Associations of prenatal phthalate exposure with neurobehavioral outcomes in 4.5- and 7.5-month-old infants

Phthalates are ubiquitous endocrine-disrupting chemicals, and research indicates that prenatal exposure to some phthalates may affect neurodevelopment. In a prospective birth cohort study, five first-morning urine samples collected across pregnancy were pooled and the following phthalate biomarkers assessed: sum of di-(2-ethylhexyl) phthalate metabolites (ΣDEHP), sum of diisononyl phthalate metabolites (ΣDINP), sum of dibutyl phthalate metabolites (ΣDBP), sum of anti-androgenic metabolites (ΣAA), monoethyl phthalate (MEP), and sum of all phthalate metabolites (ΣAll). The Ages & Stages Questionnaires® (ASQ), a standardized parent-reported, age-adapted screening tool, measured communication, personal-social, problem solving, and motor domains in infants at 4.5 and 7.5 months (n = 123). Adjusting for maternal age, annual household income, gestational age at birth, infant age at assessment, and sex, repeated-measures generalized linear regression models were used to examine associations between prenatal phthalate urine biomarker concentrations and domain scores (assuming a Poisson distribution). Beta estimates were exponentiated back to the domain scale for ease of interpretation. Mothers were mostly white and college-educated, and most reported an annual household income of ≥$60,000. Associations of phthalate concentrations with ASQ outcomes are presented as follows: (1) anti-androgenic phthalate metabolites (ΣDEHP, ΣDINP, ΣDBP, and ΣAA), (2) MEP, which is not anti-androgenic, and (3) ΣAll. Overall, anti-androgenic phthalates were associated with higher (i.e., better) scores. However, there were exceptions, including the finding that a one-unit increase in ΣDBP was associated with a 12% increase in problem solving scores in 4.5-month-old females (β = 1.12; 95% CI: 0.99, 1.28; p = 0.067) but a 85% decrease for 7.5-month-old females (β = 0.54; 95% CI: 0.3, 0.99; p = 0.047). In contrast, MEP was associated with poorer scores on several outcomes. Sex- and timepoint-specific estimates demonstrated a one-unit increase in MEP was associated with: a 52% decrease in personal-social scores in 7.5-month-old males (β = 0.66; 95% CI: 0.46, 0.95; p = 0.02), a 39% decrease in fine motor scores in 7.5-month-old males (β = 0.72; 95% CI: 0.52, 0.98; p = 0.035), and a 6% decrease in fine motor scores in 4.5-month-old females (β = 0.94; 95% CI: 0.88, 0.99; p = 0.03). A one-unit increase in ΣAll was associated with a 4% increase in personal-social scores in 4.5-month-old males (β = 1.04; 95% CI: 0.99, 1.1; p = 0.08) but a 17% decrease in 7.5-month-old males (β = 0.85; 95% CI: 0.73, 0.99; p = 0.03). These data suggest age- and sex-specific associations of prenatal phthalates with infant neurobehavior. The current findings should be confirmed by longitudinal studies with larger sample sizes.

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.

An integrated exposure and pharmacokinetic modeling framework for assessing population-scale risks of phthalates and their substitutes

To effectively incorporate in vitro-in silico-based methods into the regulation of consumer product safety, a quantitative connection between product phthalate concentrations and in vitro bioactivity data must be established for the general population. We developed, evaluated, and demonstrated a modeling framework that integrates exposure and pharmacokinetic models to convert product phthalate concentrations into population-scale risks for phthalates and their substitutes. A probabilistic exposure model was developed to generate the distribution of multi-route exposures based on product phthalate concentrations, chemical properties, and human activities. Pharmacokinetic models were developed to simulate population toxicokinetics using Bayesian analysis via the Markov chain Monte Carlo method. Both exposure and pharmacokinetic models demonstrated good predictive capability when compared with worldwide studies. The distributions of exposures and pharmacokinetics were integrated to predict the population distributions of internal dosimetry. The predicted distributions showed reasonable agreement with the U.S. biomonitoring surveys of urinary metabolites. The "source-to-outcome" local sensitivity analysis revealed that food contact materials had the greatest impact on body burden for di(2-ethylhexyl) adipate (DEHA), di-2-ethylhexyl phthalate (DEHP), di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH), and di(2-propylheptyl) phthalate (DPHP), whereas the body burden of diethyl phthalate (DEP) was most sensitive to the concentration in personal care products. The upper bounds of predicted plasma concentrations showed no overlap with ToxCast in vitro bioactivity values. Compared with the in vitro-to-in vivo extrapolation (IVIVE) approach, the integrated modeling framework has significant advantages in mapping product phthalate concentrations to multi-route risks, and thus is of great significance for regulatory use with a relatively low input requirement. Further integration with new approach methodologies will facilitate these in vitro-in silico-based risk assessments for a broad range of products containing an equally broad range of chemicals.

Development, Testing, Parameterisation and Calibration of a Human PBPK Model for the Plasticiser, Di-(2-propylheptyl) Phthalate (DPHP) Using in Silico, in vitro and Human Biomonitoring Data

A physiologically based pharmacokinetic model for Di-(2-propylheptyl) phthalate (DPHP) was developed to interpret the biokinetics in humans after single oral doses. The model was parameterized with in vitro and in silico derived parameters and uncertainty and sensitivity analysis was used during the model development process to assess structure, biological plausibility and behaviour prior to simulation and analysis of human biological monitoring data. To provide possible explanations for some of the counter-intuitive behaviour of the biological monitoring data the model included a simple lymphatic uptake process for DPHP and enterohepatic recirculation (EHR) for DPHP and the mono ester metabolite mono-(2-propylheptyl) phthalate (MPHP). The model was used to simultaneously simulate the concentration-time profiles of blood DPHP, MPHP and the urinary excretion of two metabolites, mono-(2-propyl-6-hydroxyheptyl) phthalate (OH-MPHP) and mono-(2-propyl-6-carboxyhexyl) phthalate (cx-MPHP). The availability of blood and urine measurements permitted a more robust qualitative and quantitative investigation of the importance of EHR and lymphatic uptake. Satisfactory prediction of blood DPHP and urinary metabolites was obtained whereas blood MPHP was less satisfactory. However, the delayed peak of DPHP concentration relative to MPHP in blood and second order metabolites in urine could be explained as a result of three processes: 1) DPHP entering the systemic circulation from the lymph, 2) rapid and very high protein binding and 3) the efficiency of the liver in removing DPHP absorbed via the hepatic route. The use of sensitivity analysis is considered important in the evaluation of uncertainty around in vitro and in silico derived parameters. By quantifying their impact on model output sufficient confidence in the use of a model should be afforded. This approach could expand the use of PBPK models since parameterization with in silico techniques allows for rapid model development. This in turn could assist in reducing the use of animals in toxicological evaluations by enhancing the utility of “read across” techniques.

Concentrations of Seven Phthalate Monoesters in Infants and Toddlers Quantified in Urine Extracted from Diapers

Carrying out exposure studies on children who are not toilet trained is challenging because of the difficulty of urine sampling. In this study, we optimized a protocol for urine collection from disposable diapers for the analysis of phthalate metabolites. The exposure of Swiss children (n = 113) between 6 months and 3 years of life to seven phthalates was assessed by gas chromatography-mass spectrometry measurements. The study showed limited exposures to phthalates, with only 22% of the samples containing some of the metabolites investigated. The three most frequently detected metabolites were monoethyl phthalate, mono-cyclohexyl phthalate, and mono-benzyl phthalate. We also detected mono-n-octyl phthalate and mono(3,5,5-trimethylhexyl) phthalate, which have rarely been observed in urine from infants and toddlers; therefore, di-n-octyl phthalate and bis(3,5,5-trimethylhexyl) phthalate can be considered as potentially new emerging phthalates. This study presents an initial snapshot of the Swiss children's exposure to phthalates and provides a promising approach for further phthalate biomonitoring studies on young children using disposable diapers as urine sampling technique.

Using quantitative modeling tools to assess pharmacokinetic bias in epidemiological studies showing associations between biomarkers and health outcomes at low exposures

Biomarkers of exposure can be measured at lower and lower levels due to advances in analytical chemistry. Using these sensitive methods, some epidemiology studies report associations between biomarkers and health outcomes at biomarker levels much below those associated with effects in animal studies. While some of these low exposure associations may arise from increased sensitivity of humans compared with animals or from species-specific responses, toxicology studies with drugs, commodity chemicals and consumer products have not generally indicated significantly greater sensitivity of humans compared with test animals for most health outcomes. In some cases, these associations may be indicative of pharmacokinetic (PK) bias, i.e., a situation where a confounding factor or the health outcome itself alters pharmacokinetic processes affecting biomarker levels. Quantitative assessment of PK bias combines PK modeling and statistical methods describing outcomes across large numbers of individuals in simulated populations. Here, we first provide background on the types of PK models that can be used for assessing biomarker levels in human population and then outline a process for considering PK bias in studies intended to assess associations between biomarkers and health outcomes at low levels of exposure. After providing this background, we work through published examples where these PK methods have been applied with several chemicals/chemical classes - polychlorinated biphenyls (PCBs), perfluoroalkyl substances (PFAS), polybrominated biphenyl ethers (PBDE) and phthalates - to assess the possibility of PK bias. Studies of the health effects of low levels of exposure will be improved by developing some confidence that PK bias did not play significant roles in the observed associations.

MEHP interferes with mitochondrial functions and homeostasis in skeletal muscle cells

Di (2-ethylhexyl) phthalate (DEHP) is a plasticizer frequently leached out from polyvinyl chloride (PVC) products and is quickly metabolized to its monoester equivalent mono(2-ethylhexyl) phthalate (MEHP) once enters organisms. Exposure to DEHP/MEHP through food chain intake has been shown to modified metabolism but its effect on the development of metabolic myopathy of skeletal muscle (SKM) has not been revealed so far. Here, we found that MEHP repressed myogenic terminal differentiation of proliferating myoblasts (PMB) and confluent myoblasts (CMB) but had weak effect on this process once it had been initiated. The transition of mitochondria (MITO) morphology from high efficient filamentary network to low efficient vesicles was triggered by MEHP, implying its negative effects on MITO functions. The impaired MITO functions was further demonstrated by reduced MITO DNA (mtDNA) level and SDH enzyme activity as well as highly increased reactive oxygen species (ROS) in cells after MEHP treatment. The expression of metabolic genes, including PDK4, CPT1b, UCP2, and HO1, was highly increased by MEHP and the promoters of PDK4 and CPT1b were also activated by MEHP. Additionally, the stability of some subunits in the oxidative phosphorylation system (OXPHOS) complexes was found to be reduced by MEHP, implying defective oxidative metabolism in MITO and which was confirmed by repressed palmitic acid oxidation in MEHP-treated cells. Besides, MEHP also blocked insulin-induced glucose uptake. Taken together, our results suggest that MEHP is inhibitory to myogenesis and is harmful to MITO functions in SKM, so its exposure should be avoided or limited.

Food emulsifier polysorbate 80 promotes the intestinal absorption of mono-2-ethylhexyl phthalate by disturbing intestinal barrier

Di-2-ethylhexyl phosphate (DEHP) and its main toxic metabolite mono-2-ethylhexyl phthalate (MEHP) are the typical endocrine disrupting chemicals (EDCs) and widely affect human health. Our previous research reported that synthetic nonionic dietary emulsifier polysorbate 80 (P80, E433) had the promotional effect on the oral absorption of DEHP in rats. The aim of this study was to explore its mechanism of promoting oral absorption, focusing on the mucus barrier and mucosal barrier of the small intestine. A small molecule fluorescent probe 5-aminofluorescein-MEHP (MEHP-AF) was used as a tracker of MEHP in vivo and in vitro. First of all, we verified that P80 promoted the bioavailability of MEHP-AF in the long-term and low-dose exposure of MEHP-AF with P80 as a result of increasing the intestinal absorption of MEHP-AF. Afterwards, experimental results from Western blot, qPCR, immunohistochemistry, and immunofluorescence showed that P80 decreased the expression of proteins (mucus protein mucin-2, tight junction proteins claudin-1 and occludin) related to mucus barrier and mucosal barrier in the intestine, changed the integrity of intestinal epithelial cell, and increased the permeability of intestinal epithelial mucosa. These results indicated that P80 promoted the oral absorption of MEHP-AF by altering the intestinal mucus barrier and mucosal barrier. These findings are of great importance for assessing the safety risks of some food emulsifiers and clarifying the absorption mechanism of chemical pollutants in food, especially for EDCs.

Human metabolism and urinary excretion kinetics of di-n-butyl adipate (DnBA) after oral and dermal administration in three volunteers

Di-n-butyl adipate (DnBA) is used as a plasticizer and in various consumer products (e.g. personal care products) replacing, in part, the endocrine disruptor di-n-butyl phthalate (DnBP). We provide quantitative in vivo data on human DnBA metabolism and excretion after oral dose (105-185 μg/kg bw) and dermal application to three volunteers each as a tool for exposure and risk assessment. Complete and consecutive urine samples were collected for two (oral) and four days (dermal), respectively, and analyzed for the metabolites mono-n-butyl adipate (MnBA), 3- and tentative 4-hydroxy-mono-n-butyl adipate (3OH-MnBA, 4OH-MnBA), and 3-carboxy-mono-n-propyl adipate (3cx-MnPrA), as well as the hydrolysis product adipic acid (AA) using stable isotope dilution quantification. Metabolites were excreted within 24 h after oral dose with one or two concentration maxima at 0.8-3.0 h (n = 3) and 4.8-6.3 h (n = 2). AA was the major but unspecific metabolite with urinary excretion fractions (F_UEs) of 14-26 %. Mean F_UEs (range) of 3cx-MnPrA, MnBA, 3OH-MnBA, and tentative 4OH-MnBA were low, but consistent between volunteers (0.47 % (0.35-0.63 %), 0.079 % (0.065-0.091 %), 0.012 % (0.006-0.016 %), and 0.005 % (0.002-0.009 %), respectively). MnBA and 3OH-MnBA seem to be suitable, specific exposure biomarkers for DnBA, whereas 3cx-MnPrA and 4OH-MnBA seem to originate also from other, unknown sources not related to DnBA. Compared to the oral study, metabolite excretion in the dermal study was delayed and MnBA excretion was somewhat higher compared to the oxidized metabolites. Based on urinary concentrations and the above excretion fractions, calculated uptakes in the dermal study did not exceed the adipate ester ADI of 5 mg/(kg bw*day).

Development of a physiologically based pharmacokinetic model of diisononyl phthalate (DiNP) in pregnant rat and human

A physiologically based pharmacokinetic (PBPK) model for di-isononyl phthalate (DiNP) was developed by adapting the existing models for di(2-ethylhexyl) phthalate (DEHP) and di-butylphthalate (DBP). Both pregnant rat and human time-course plasma and urine data were used to address the hydrolysis of DiNP in intestinal tract, plasma, and liver as well as hepatic oxidative metabolism and conjugation of the monoester and primary oxidative metabolites. Data in both rats and humans were available to inform the uptake and disposition of mono-isononyl phthalate (MiNP) as well as the three primary oxidative metabolites including hydroxy (7-OH)-, oxo (7-OXO)-, and carboxy (7-COX)-monoisononyl phthalate in plasma and urine. The DiNP model was reliable over a wide range of exposure levels in the pregnant rat as well as the two low exposure levels in humans including capturing the nonlinear behavior in the pregnant rat after repeated 750 mg/kg/day dosing. The presented DiNP PBPK model in pregnant rat and human, based upon an extensive kinetic dataset in both species, may provide a basis for assessing human equivalent exposures based upon either rodent or in vitro points of departure.

Identifying Plant-Based Natural Medicine against Oxidative Stress and Neurodegenerative Disorders

Free radicals and oxidative stress are among the most studied factors leading to the imbalance in mental health. With no exception, free radicals also damage neuronal cells, leading to various degenerative diseases. With existing modern medications, around 80% of the world population relies on herbal medicine for various ailments. Phytochemicals in plants have a wide range of pharmacological properties, the major being their ability to scavenge free radicals. Plant polyphenols are among the major class of antioxidants identified in plants. This antioxidative property of plant compounds and their ability to downgrade the process of oxidative stress can be used to treat neurodegenerative diseases. However, selecting plants and their active compounds is a crucial step in framing the mechanism of action underlying their therapeutic potential.

A framework for assessing the impact of chemical exposures on neurodevelopment in ECHO: Opportunities and challenges

The Environmental influences on Child Health Outcomes (ECHO) Program is a research initiative funded by the National Institutes of Health that capitalizes on existing cohort studies to investigate the impact of early life environmental factors on child health and development from infancy through adolescence. In the initial stage of the program, extant data from 70 existing cohort studies are being uploaded to a database that will be publicly available to researchers. This new database will represent an unprecedented opportunity for researchers to combine data across existing cohorts to address associations between prenatal chemical exposures and child neurodevelopment. Data elements collected by ECHO cohorts were determined via a series of surveys administered by the ECHO Data Analysis Center. The most common chemical classes quantified in multiple cohorts include organophosphate pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, environmental phenols (including bisphenol A), phthalates, and metals. For each of these chemicals, at least four ECHO cohorts also collected behavioral data during infancy/early childhood using the Child Behavior Checklist. For these chemicals and this neurodevelopmental assessment (as an example), existing data from multiple ECHO cohorts could be pooled to address research questions requiring larger sample sizes than previously available. In addition to summarizing the data that will be available, the article also describes some of the challenges inherent in combining existing data across cohorts, as well as the gaps that could be filled by the additional data collection in the ECHO Program going forward.

Transient Multimedia Model for Investigating the Influence of Indoor Human Activities on Exposure to SVOCs

Empirical evidence suggests that human occupants indoors, through their presence and activities, can influence the dynamics of semivolatile organic compounds (SVOCs). To better understand these dynamics, a transient multimedia human exposure model was developed (Activity-Based Indoor Chemical Assessment Model (ABICAM)). This model parametrizes mass-balance equations as functions of time-dependent human activities. As a case study, ABICAM simulated exposures of an archetypal adult and toddler over 24 h to diethyl phthalate (DEP), butyl benzyl phthalate (BBzP), and di-2-ethylhexyl phthalate (DEHP) that span a wide range of gas-particle partitioning tendencies. Under baseline (no activities beyond respiration), the toddler's time-average internal doses were three to four times higher than the adult's, due to differences in physical human attributes (e.g., inhalation rate). When time-dependent activities were considered, interindividual (e.g., adult vs toddler) variability was accentuated by up to a factor of 3 for BBzP. Activities with the greatest influence on time-average internal dose were showering (-71% for BBzP), cooking (+27% for DEHP), and sleeping (-26% for DEHP). Overall, the results support the hypotheses that (1) transient indoor activities can give rise to intraindividual variability in estimated internal doses of SVOCs, and (2) interindividual variability in such exposure can result from differences in activity patterns and physical human attributes, according to a compound's physical-chemical properties.

Biomonitoring of occupational exposure to phthalates: A systematic review

INTRODUCTION

Phthalates, a group of ubiquitous industrial chemicals, have been widely used in occupational settings, mainly as plasticizers in a variety of applications. Occupational exposure to different phthalates has been studied in several occupational settings using human biomonitoring (HBM).

AIM

To provide a comprehensive review of the available literature on occupational exposure to phthalates assessed using HBM and to determine future data needs on the topic as part of the HBM4EU project.

METHODS

A systematic search was carried out in the databases of Pubmed, Scopus, and Web of Science for articles published between 2000 and September 4, 2019 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 22 studies on the occupational HBM of phthalates was considered suitable for review.

RESULTS AND DISCUSSION

Among the reviewed studies, 19 (86%) focused on DEHP, an old phthalate that is now subject to authorization and planned to be restricted in the EU. Concentrations of MEHHP, one of its metabolites, varied up to 13-fold between studies and across sectors when comparing extreme geometric means, ranging from 11.6 (similar to the general populations) to 151 μg/g creatinine. Only 2 studies focused on newer phthalates such as DiNP and DPHP. Concerning the geographical distribution, 10 studies were performed in Europe (including 6 in Slovakia), 8 in Asia, and 4 in North America, but this distribution is not a good reflection of phthalate production and usage levels worldwide. Most HBM studies were performed in the context of PVC product manufacturing. Future studies should focus on: i) a more uniform approach to sampling timing to facilitate comparisons between studies; ii) newer phthalates; and iii) old phthalates in waste management or recycling.

CONCLUSION

Our findings highlight the lack of recent occupational HBM studies on both old and new phthalate exposure in European countries and the need for a harmonized approach. Considering the important policy actions taken in Europe regarding phthalates, it seems relevant to evaluate the impact of these actions on exposure levels and health risks for workers.

Use of stored serum in the study of time trends and geographical differences in exposure of pregnant women to phthalates

BACKGROUND

Exposure to some phthalate diesters has been associated with adverse reproductive health outcomes in both rodents and humans indicative of anti-androgenic effects. Exposure during sensitive periods of development, such as prenatally, is of particular concern.

OBJECTIVES

We wished to investigate whether phthalate metabolites measured in maternal serum samples from historical birth cohorts can be used to assess prenatal exposure. Further, we aimed to study temporal and geographical trends in phthalate exposure across three different birth cohorts.

METHODS

We compared phthalate metabolite levels in maternal serum samples from an Australian (1989-91) and a Danish (1997-2001) birth cohort with levels in serum and urine samples from a recent Danish birth cohort (2012-14). Samples were analysed for 32 phthalate metabolites from 15 phthalate diesters by isotope-diluted liquid chromatography-tandem mass spectrometry (LC-MS/MS). Correlations between metabolites were tested by Spearman rank correlation test, and differences between the cohorts were tested by Mann-Whitney U test.

RESULTS

Overall, we observed large variations in serum phthalate metabolite levels between individuals. Secondary metabolites of di-(2-ethyl-hexyl) phthalate (DEHP) and di-iso-nonyl phthalate (DiNP) in serum were weakly to moderately and positively correlated to the levels measured in urine, and secondary metabolites of DEHP were also moderately to strongly and significantly correlated in serum. Correlations with mono-(2-ethyl-hexyl) phthalate (MEHP) and mono-iso-nonyl phthalate (MiNP), the two primary metabolites of DEHP and DiNP, were inconsistent, and we found indications of sample contamination. We observed some significant differences in phthalate metabolite levels between the three cohorts with generally higher levels in the older birth cohorts.

CONCLUSION

Based on comparison across two older birth cohorts and a recent cohort, our results support the concept that historical biobanked serum samples may be used for assessment of prenatal exposure to phthalates when using serum levels of the monoesters of the low-molecular weight (LMW) phthalates and the secondary metabolites of the high-molecular weight (HMW) phthalates. Serum phthalate measurements are, however, not suitable for human biomonitoring and should only be used to exploit historical samples from cohorts, where urine samples were not collected. Our findings suggest that phthalate exposure may have decreased over time from the early 1990s to the 2010s.

Could phthalates exposure contribute to the development of metabolic syndrome and liver disease in humans?

In the study, 305 patients of both genders were enrolled and divided into three groups: obese (BMI > 30 kg/m²), patients who were diagnosed type 2 diabetes mellitus (T2DM), and control, normal weight healthy volunteers. At least one of ten different phthalate metabolites was determined in the urine samples of 49.84% all enrolled participants. In the obese subgroup, the sum of all urinary phthalate metabolites was positively associated with TG levels (p = 0.031) together with derived TC/HDL and TG/HDL ratios (p = 0.023 and 0.015), respectively. Urinary MEP concentration was positively correlated with the HOMA-IR in T2DM subgroup (p = 0.016) while in the control subgroup, log₁₀MEP levels were negatively correlated with total cholesterol (p = 0.0051), and LDL serum levels (p = 0.0015), respectively. Also, in the control subgroup, positive linear correlations between urinary log₁₀MEP levels and TyG and TYG-BMI values (p = 0.028 and p = 0.027), respectively, were determined. Urinary MEHP levels were associated with glucose serum levels (p = 0.02) in T2DM subgroup, while in the control HDL values were negatively associated with log₁₀MEHP (p = 0.0035). Healthy volunteers exposed to phthalates had elevated AST levels in comparison to non-exposed ones (p = 0.023). In control subgroup, ALT and AST values were increased (p = 0.02 and p = 0.01, respectively) in MEP exposed while GGT levels were enhanced (p = 0.017) in MEHP exposed in comparison with non-exposed. Combined phthalates influence on glucose and lipid metabolism may increase the possibility for NAFLD and insulin resistance development among exposed individuals.

Sources of clinically significant neonatal intensive care unit phthalate exposure

In the United States each year, more than 300,000 infants are admitted to neonatal intensive care units (NICU) where they are exposed to a chemical-intensive hospital environment during a developmentally vulnerable period. Although multiple studies have demonstrated elevated phthalate biomarkers in NICU patients, specific sources of NICU-based phthalate exposure have not been identified.In this study, premature newborns with birth weight <1500 g were recruited to participate in a prospective environmental health cohort during the NICU hospitalization. Exposure to specific NICU equipment was recorded daily during the NICU hospitalization. One hundred forty-nine urine specimens from 71 infants were analyzed for phthalate metabolites using high-performance liquid chromatography/tandem mass spectrometry.In initial analyses, exposure to medical equipment was directly related to phthalate levels, with DEHP biomarkers 95-132% higher for infants exposed to specific medical equipment types compared to those without that equipment exposure (p < 0.001-0.023). This association was mirrored for clinically relevant phthalate mixtures whether composed of DEHP metabolites or not (p = 0.002-0.007). In models accounting for concurrent equipment use, exposure to respiratory support was associated with DEHP biomarkers 50-136% higher in exposed compared to unexposed infants (p = 0.007-0.036). Phthalate mixtures clinically relevant to neurobehavioral development were significantly associated with non-invasive respiratory support (p = 0.008-0.026). Feeding supplies and intravenous lines were not significantly associated with clinically important phthalate mixtures.Respiratory support equipment may be a significant and clinically relevant NICU source of phthalate exposure. Although manufacturers have altered feeding and intravenous supplies to reduce DEHP exposure, other sources of exposure to common and clinically impactful phthalates persist in the NICU.

Development, Testing, Parameterization, and Calibration of a Human Physiologically Based Pharmacokinetic Model for the Plasticizer, Hexamoll® Diisononyl-Cyclohexane-1, 2-Dicarboxylate Using In Silico, In Vitro, and Human Biomonitoring Data

A physiologically based pharmacokinetic model for Hexamoll^® diisononyl-cyclohexane-1, 2-dicarboxylate was developed to interpret the biokinetics in humans after single oral doses. The model was parameterized with in vitro and in silico derived parameters and uncertainty and sensitivity analysis was used during the model development process to assess structure, biological plausibility and behavior prior to simulation and analysis of human biological monitoring data. The model provided good simulations of the urinary excretion (Curine) of two metabolites; cyclohexane-1,2-dicarboxylic acid mono hydroxyisononyl ester (OH-MINCH) and cyclohexane-1, 2-dicarboxylic acid mono carboxyisononyl ester (cx-MINCH) from the biotransformation of mono-isononyl-cyclohexane-1, 2-dicarboxylate (MINCH), the monoester metabolite of di-isononyl-cyclohexane-1,2-dicarboxylate. However, good simulations could be obtained, with and without, a lymphatic compartment. Selection of an appropriate model structure was informed by sensitivity analysis which could identify and quantify the contribution to variability in Curine by parameters, such as, the fraction of oral dose that directly entered the lymphatic compartment and therefore by-passed the liver and the fraction of MINCH bio-transformed to cx-MINCH and OH-MINCH. By constraining these parameters within biologically plausible limits the presence of a lymphatic compartment was deemed an important component of model structure. Furthermore, the use of sensitivity analysis is important in the evaluation of uncertainty around in silico derived parameters. By quantifying their impact on model output sufficient confidence in the use of a model should be afforded. This type of approach could expand the use of physiologically based pharmacokinetic models since parameterization with in silico techniques allows for rapid model development. This in turn could assist in reducing the use of animals in toxicological evaluations by enhancing the utility of “read across” techniques.

Bioavailability of phthalate and DINCH® plasticizers, after oral administration of dust to piglets

For decades, phthalates have been widely used as plasticizers in a large number of consumer products, leading to a complex exposure to humans via ingestion, inhalation or dermal uptake. Children may have a higher unintended dust intake per day compared to adults. Therefore, dust intake of children could pose a relevant exposure and subsequently a potential health risk. The aim of this study was to determine the relative bioavailability of certain phthalates, such as di(2-ethylhexyl) phthalate (DEHP), di-isononyl phthalate (DINP) and the non-phthalate plasticizer diisononyl 1,2-cyclohexanedicarboxylic acid (DINCH^®, Hexamoll^®), after ingestion of dust. Seven 5-week-old male piglets were fed five different dust samples collected from daycare centers. Overall, 0.43 g to 0.83 g of dust sieved to 63 μm were administered orally. The piglets' urine was collected over a period of 38 h. The excreted metabolites were quantified using an LC-MS/MS method. The mean uptake rates of the applied doses for DEHP, DINP, and DINCH^® were 43% ± 11%, 47% ± 26%, and 9% ± 3.5%, respectively. The metabolites of DEHP and DINP showed maximum concentrations in urine after three to five hours, whereas the metabolites of DINCH^®, reached maximum concentrations 24 h post-dose. The oral bioavailability of the investigated plasticizers was higher compared to the bioaccessibility reported from in vitro digestion tests. Furthermore, the bioavailability of DEHP did not vary substantially between the dust samples, whereas a dose-dependent saturation process for DINP was observed. In addition to other intake pathways, dust could be a source of plasticizers in children using the recent intake rates for dust ingestion.

Plasticizer Interaction With the Heart: Chemicals Used in Plastic Medical Devices Can Interfere With Cardiac Electrophysiology

BACKGROUND

Phthalates are used as plasticizers in the manufacturing of flexible, plastic medical products. Patients can be subjected to high phthalate exposure through contact with plastic medical devices. We aimed to investigate the cardiac safety and biocompatibility of mono-2-ethylhexyl phthalate (MEHP), a phthalate with documented exposure in intensive care patients.

METHODS

Optical mapping of transmembrane voltage and pacing studies were performed on isolated, Langendorff-perfused rat hearts to assess cardiac electrophysiology after MEHP exposure compared with controls. MEHP dose was chosen based on reported blood concentrations after an exchange transfusion procedure.

RESULTS

Thirty-minute exposure to MEHP increased the atrioventricular node (147 versus 107 ms) and ventricular (117 versus 77.5 ms) effective refractory periods, compared with controls. Optical mapping revealed prolonged action potential duration at slower pacing cycle lengths, akin to reverse use dependence. The plateau phase of the action potential duration restitution curve steepened and became monophasic in MEHP-exposed hearts (0.18 versus 0.06 slope). Action potential duration lengthening occurred during late-phase repolarization resulting in triangulation (70.3 versus 56.6 ms). MEHP exposure also slowed epicardial conduction velocity (35 versus 60 cm/s), which may be partly explained by inhibition of Na_v1.5 (874 and 231 µmol/L half-maximal inhibitory concentration, fast and late sodium current).

CONCLUSIONS

This study highlights the impact of acute MEHP exposure, using a clinically relevant dose, on cardiac electrophysiology in the intact heart. Heightened clinical exposure to plasticized medical products may have cardiac safety implications-given that action potential triangulation and electrical restitution modifications are a risk factor for early after depolarizations and cardiac arrhythmias.

Di(2-ethylhexyl) phthalate (DEHP) increases proliferation of epithelial breast cancer cells through progesterone receptor dysregulation

The di(2-ethylhexyl) phthalate (DEHP) is a plasticizer incorporated to plastic matrices of widely used consumer products. However, it is gradually released from these products, resulting in a chronic exposure for humans. Although DEHP, similar to other members of the phthalates family, is generally considered as an endocrine disruptor, the mechanisms implicated in its toxicity are yet poorly understood. Our objective was to determine the effects of an exposure to DEHP and to one of its major metabolite, the mono(2-ethylhexyl) phthalate (MEHP) on markers involved in breast carcinogenesis. T-47D cells were exposed to environmentally relevant and higher doses of DEHP and MEHP (0.1-10 000 nM) for 4 days. Our results showed that an exposure to 10 000 nM of DEHP and 0.1 nM of MEHP significantly increased the proliferation of T-47D cells, without inducing apoptosis. In addition, a significant increase in the protein levels of the isoform A of the progesterone receptor (PR) and of nuclear levels of PR were observed in T-47D cells exposed to 10 000 nM of DEHP. Importantly, the increased proliferation and nuclear levels of PR were totally and partially inhibited, respectively, by Mifepristone, a PR antagonist. These results suggest that an exposure to DEHP or MEHP increase cell proliferation by activating PR signaling, which could potentially increase the risks to develop breast cancer. The mechanism of activation of the progesterone pathway by DEHP and the long-term consequences of this activation remained to be elucidated.

Aqueous extract of Eruca Sativa protects human spermatozoa from mitochondrial failure due to bisphenol A exposure

Medicinal plants are suggested to counteract health disorders from chemical pollutants. Here we explored the possible ameliorative effect of Eruca sativa aqueous extract (ESAE) on in vitro acute functional disturbance induced by Bisphenol A (BPA), a disruptor model in human spermatozoa. Phytochemical screening, high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) analysis and 2,2'-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid]/α,α-diphenyl-β-picrylhydrazyl (ABTS/DPPH) tests disclosed antioxidant properties of ESAE, ascribed to polyphenols and flavonoids. The toxicological impact of BPA on sperm viability and motility was detected for concentration greater than 10 μM but co-incubation with ESAE recovered sperm function at low concentration (15.62 μg/ml). BPA reduced mitochondrial membrane potential (ΔΨm), with no impact on plasma membrane potential (ΔΨp). At low doses, ESAE recovered ΔΨm but higher doses were associated with impairment of both ΔΨm and ΔΨp. ESAE protects towards in vitro BPA-mediated toxicity and its possible use as complementary treatment for male reproductive disorders is critically discussed.

Excretion of Di-2-ethylhexyl phthalate (DEHP) metabolites in urine is related to body mass index because of higher energy intake in the overweight and obese

A higher body mass index (BMI) has been positively associated with the rate of excretion of di-2-ethylhexyl phthalate (DEHP) metabolites in urine in data from the National Health and Nutrition Examination Survey (NHANES), suggesting an association between DEHP exposure and BMI. The association, however, may be due to the association between body mass maintenance and higher energy intake, with higher energy intake being accompanied by a higher intake of DEHP. To examine this hypothesis, we ran a Monte Carlo simulation with a DEHP physiologically-based pharmacokinetic (PBPK) model for adult humans. A realistic exposure sub-model was used, which included the relation of body weight to energy intake and of energy intake to DEHP intake. The model simulation output, when compared with urinary metabolite data from NHANES, supported good model validity. The distribution of BMI in the simulated population closely resembled that in the NHANES population. This indicated that the simulated subjects and DEHP exposure model were closely aligned with the NHANES population of interest. In the simulated population, the ordinary least squares regression coefficient for log(BMI) as a function of log(DEHP nmol/min) was 0.048 (SE 0.001), as compared with the reported value of 0.019 (SE 0.005). In other words, given our model structure, the higher energy intake in the overweight and obese, and the concomitant higher DEHP exposure, describes the reported relationship between BMI and DEHP.

Neonatal intensive care unit phthalate exposure and preterm infant neurobehavioral performance

Every year in the United States, more than 300,000 infants are admitted to neonatal intensive care units (NICU) where they are exposed to a chemical-intensive hospital environment during a developmentally vulnerable period. The neurodevelopmental impact of environmental exposure to phthalates during the NICU stay is unknown. As phthalate exposure during the third trimester developmental window has been implicated in neurobehavioral deficits in term-born children that are strikingly similar to a phenotype of neurobehavioral morbidity common among children born premature, the role of early-life phthalate exposure on the neurodevelopmental trajectory of premature infants may be clinically important. In this study, premature newborns with birth weight <1500g were recruited to participate in a prospective environmental health cohort study, NICU-HEALTH (Hospital Exposures and Long-Term Health), part of the DINE (Developmental Impact of NICU Exposures) cohort of the ECHO (Environmental influences on Child Health Outcomes) program. Seventy-six percent of eligible infants enrolled in the study. Sixty-four of 81 infants survived and are included in this analysis. 164 urine specimens were analyzed for phthalate metabolites using high-performance liquid chromatography/tandem mass spectrometry. The NICU Network Neurobehavioral Scale (NNNS) was performed prior to NICU discharge. Linear and weighted quantile sum regression quantified associations between phthalate biomarkers and NNNS performance, and between phthalate biomarkers and intensity of medical intervention. The sum of di(2-ethylhexyl) phthalate metabolites (∑DEHP) was associated with improved performance on the Attention and Regulation scales. Specific mixtures of phthalate biomarkers were also associated with improved NNNS performance. More intense medical intervention was associated with higher ∑DEHP exposure. NICU-based exposure to phthalates mixtures was associated with improved attention and social response. This suggests that the impact of phthalate exposure on neurodevelopment may follow a non-linear trajectory, perhaps accelerating the development of certain neural networks. The long-term neurodevelopmental impact of NICU-based phthalate exposure needs to be evaluated.