Toxic potential of the plasticizer Di(2-ethylhexyl) phthalate in the context of its disposition and metabolism in primates and man

Comprehensive assessment of the UV-filter 2-ethylhexyl salicylate and its phase I/II metabolites in urine by extended enzymatic hydrolysis and on-line SPE LC-MS/MS

2-ethylhexyl salicylate (EHS) is used as a UV filter in personal-care products, such as sunscreen, to prevent skin damage through UV radiation. The application of EHS-containing products leads to systemic EHS absorption, metabolization and excretion. To measure EHS and its corresponding metabolite levels in urine, a comprehensive analytical procedure based on an extended enzymatic hydrolysis, on-line-SPE, and UPLC-MS/MS was developed. The method covers a large profile of seven metabolites (including isomeric structures) as well as EHS itself in a run time only of 18 min. Easy sample preparation, consisting of a 2-h hydrolysis step, followed by on-line enrichment and purification, add to the efficiency of the method. An update, compared to a previous method for the determination of EHS and metabolites in urine, is that, during hydrolysis, both glucuronide and sulfate conjugates are considered. The method was furthermore applied to urine samples after a real-life exposure scenario to EHS-containing sunscreen. The method is highly sensitive with limits of detection ranging from 6 to 65 ng/L. Moreover, it is characterized by good precision data, accuracy, and robustness to matrix influences. Application of the method to urine samples following dermal exposure to an EHS-containing sunscreen revealed EHS as the main biomarker after dermal exposure, followed by the major biomarkers 5OH-EHS, 5cx-EPS, 4OH-EHS and 5oxo-EHS. The expansion and optimization of this method decisively contributes to the research on the dermal metabolism of EHS and can be applied in exposure studies and for human biomonitoring.

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.

Phthalate contamination in marine mammals off the Norwegian coast

Phthalates are used in plastics, found throughout the marine environment and have the potential to cause adverse health effects. In the present study, we quantified blubber concentrations of 11 phthalates in 16 samples from stranded and/or free-living marine mammals from the Norwegian coast: the killer whale (Orcinus orca), sperm whale (Physeter macrocephalus), long-finned pilot whale (Globicephala melas), white-beaked dolphin (Lagenorhynchus albirostris), harbour porpoise (Phocoena phocoena), and harbour seal (Phoca vitulina). Five compounds were detected across all samples: benzyl butyl phthalate (BBP; in 50 % of samples), bis(2-ethylhexyl) phthalate (DEHP; 33 %), diisononyl phthalate (DiNP; 33 %), diisobutyl phthalate (DiBP; 19 %), and dioctyl phthalate (DOP; 13 %). Overall, the most contaminated individual was the white-beaked dolphin, whilst the lowest concentrations were measured in the killer whale, sperm whale and long-finned pilot whale. We found no phthalates in the neonate killer whale. The present study is important for future monitoring and management of these toxic compounds.

Colonic mechanism of serum NAD+ depletion induced by DEHP during pregnancy

Di (2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer in polyvinyl chloride products such as feed piping, packing bag, and medical consumable. Our previous studies have demonstrated that DEHP exposure reduced the concentration of nicotinamide adenine dinucleotide (NAD⁺) in pregnant mice serum, which cuts off the source of NAD⁺ to placenta and results fetal growth restriction. However, the mechanism of serum NAD⁺ depletion by DEHP remains elusive. This study investigated the intestinal mechanism of NAD⁺ shortage-induced by DEHP in pregnant mice. The transcriptome results implicated that the mRNA level of oxidative response genes Cyp1a1, Gsto2, Trpv1 and Trpv3 were upregulated in colon. These changes induced intestinal inflammation. Transmission Electron Microscopy results displayed that DEHP destroyed the tight junctions and cell polarity of colonic epithelial cells. These dysfunctions diminished the expression of NAD⁺ precursor transporters SLC12A8, SLC5A8, SLC7A5, and the NAD⁺ biosynthetic key enzymes NAMPT, NMNAT1-3, and TDO2 in colonic epithelial cells. Analysis of the gut microbiota showed that DEHP led to the dysbiosis of gut microbiota, reducing the relative abundance of Prevotella copri which possesses the VB3 biosynthetic pathway. Therefore, maternal DEHP exposure during pregnancy decreased the transportation of NAD⁺ precursors from enteric cavity to colonic epithelial cells, and inhibited the synthesis of NAD⁺ in colonic epithelial cells. Meanwhile, DEHP reduced the NAD⁺ precursors provided by gut microbiota. Eventually, serum NAD⁺ content was lowered. Taken together, our findings provide a new insight for understanding the intestinal mechanisms by which DEHP affects serum NAD⁺ levels.

Multiple transcriptomic profiling: potential novel metabolism-related genes predict prepubertal testis damage caused by DEHP exposure

The toxic effect of di(2-ethylhexyl) phthalate (DEHP) on prepubertal testes was examined in this study. We treated 3-week-old male mice with 4.8 mg/kg/day (milligram/kilogram/day) (no observed adverse effect level), 30 mg/kg/day (high exposure dose relative to humans), 100 mg/kg/day (level causing a reproductive system disorder), and 500 mg/kg/day (dose causing a multigenerational reproductive system disorder) of DEHP via gavage. Obvious abnormalities in the testicular organ coefficient, spermatogenic epithelium, and testosterone levels occurred in the 500 mg/kg DEHP group. Ribonucleic acid sequencing (RNA-seq) showed that differentially expressed genes (DEGs) in each group could enrich reproduction and reproductive process terms according to the gene ontology (GO) results, and coenrichment of metabolism pathway was observed by the Reactome pathway analysis. Through the analysis of common genes in the metabolism pathway, we discovered that DEHP exposure at 4.8 to 500 mg/kg or 100 mg/kg caused the same damages to the prepubertal testis. In general, we identified two key transcriptional biomarkers (fatty acid binding protein 3 (Fabp3) and carboxylesterase (Ces) 1d), which provided new insight into the gene regulatory mechanism associated with DEHP exposure and will contribute to the prediction and diagnosis of prepuberty testis injury caused by DEHP.

Toxicology and carcinogenesis studies of di(2-ethylhexyl) phthalate administered in feed to Sprague Dawley (Hsd:Sprague Dawley SD) rats

Di(2-ethylhexyl) phthalate (DEHP) is a member of the phthalate ester chemical class that occurs commonly in the environment and to which humans are widely exposed. Lifetime exposure to DEHP is likely to occur, including during the in utero and early postnatal windows of development. To date, no carcinogenicity assessments of DEHP have used a lifetime exposure paradigm that includes the perinatal period (gestation and lactation). The National Toxicology Program (NTP) tested the hypothesis that exposure during the perinatal period would alter the DEHP carcinogenic response quantitatively (more neoplasms) or qualitatively (different neoplasm types). Two chronic carcinogenicity assessments of DEHP were conducted in which Sprague Dawley (Hsd:Sprague Dawley SD) rats were exposed to dosed feed containing 0, 300, 1,000, 3,000, or 10,000 ppm DEHP for 2 years using different exposure paradigms. In Study 1, groups of 45 F0 time-mated females were provided dosed feed beginning on gestation day (GD) 6 through lactation. On postnatal day (PND) 21, groups of 50 F1 rats per sex continued on the study and were provided dosed feed containing the same DEHP concentration as their respective dam for 2 years. In Study 2, groups of 50 rats per sex, aged 6 to 7 weeks at study start, were provided dosed feed containing DEHP for 2 years. (Abstract Abridged).

Exposure estimates of phthalates and DINCH from foods and personal care products in comparison with biomonitoring data in 24-hour urine from the Norwegian EuroMix biomonitoring study

Phthalates are diesters of phthalic acid and have been widely used as plasticizers in polyvinyl chloride (PVC) plastics. Phthalates are also used as excipients in pharmaceuticals and personal care products (PCPs). Phthalates can migrate from the plastic into the air, water and food, and humans can be exposed via multiple pathways such as dermal, oral and inhalation. There is evidence that phthalates can induce reproductive and developmental toxicity not only in experimental animals but also in humans through disruption of estrogenic activity. The aim of this study was to collect concentration data on five phthalates in foods and PCPs from the scientific literature and combine these with food consumption data and PCP use frequency data from the EuroMix biomonitoring (BM) study in order to assess exposure. Probabilistic exposure assessments of phthalates were performed from foods and PCPs. Due to the very limited data available in the literature for DINCH, an exposure assessment was not carried out for this compound. The food groups with the highest contribution to phthalates exposure were: beverages, dairy, bread and meat products. The exposure estimates were compared with the measured phthalate metabolite levels from 24-hour urine samples. Regarding the oral route, measured phthalate exposure was between the lower bound (LB) and medium bound (MB) estimated exposure for all phthalates, except for DEP. The measured exposure from urine correlated with the estimated exposure from food for DEHP and DBP, while for BBP and DEP it correlated with the exposure estimates from PCPs. There were no significant differences between the BM data and the estimated exposure, except for DINP for males (p = 0.01). The LB and MB phthalate exposures estimated from foods and PCPs and the measured exposure from the urine were considerably lower than their respective tolerable daily intake (TDI) values established by the European Food Safety Authority (EFSA) and the World Health Organization (WHO). For the upper bound (UB), the exposure estimates are approximately double the TDI; however, this is regarded as a worst-case estimate and has low correlation with the measured exposure.

Phthalate Exposures in the Neonatal Intensive Care Unit

Background: Di-2-ethylhexyl phthalate (DEHP), a phthalate compound found in medical devices, may cause toxic effects in premature infants. In this study, the objective is to quantify DEHP exposures from various intravenous and respiratory therapy devices, and to use these values to predict typical exposure for an infant in a neonatal unit. Methods: Common IV products used on infants are directed through various types of IV tubing (IVT) and analyzed for DEHP content. DEHP exposure for infants receiving respiratory therapy was determined indirectly through analysis of urine DEHP metabolites. By deriving these values for DEHP we calculated the daily exposure to DEHP from common IV fluids (IVF) and respiratory devices during hospitalization in a neonatal unit. Results: IVF labeled DEHP-positive showed very high concentrations of DEHP, but when passed through IVT, substantial amounts were adsorbed. DEHP was undetectable with all DEHP-negative IVF tests, except when passed through DEHP-positive IVT. The DEHP leached from most respiratory devices was relatively modest, except that detected from bubble CPAP. In 14 very low birthweight infants, the mean DEHP exposure was 182,369 mcg/kg over 81.2 days of the initial hospitalization. Ninety-eight percent of the exposure was from respiratory devices, with bubble CPAP accounting for 95% of the total DEHP exposure in these infants. Conclusions: The DEHP exposure in our neonatal unit can be reduced markedly by avoiding or modifying bubble CPAP equipment and avoiding IV tubing containing DEHP.

Prenatal Phthalates Exposure and Cord Thyroid Hormones: A Birth Cohort Study in Southern Taiwan

BACKGROUND

The regulation of thyroid hormones in the early stages of gestation plays a crucial role in the outcome of a pregnancy. Furthermore, thyroid hormones are fundamental for the fetal development of all organs, including endocrine hormone changes in uterus. Endocrine disrupting chemicals have been shown to have an effect on thyroid hormone homeostasis in newborns, which affects their later development. Few studies have proposed how phthalates could alter thyroid function through several mechanisms and the possible effects on thyroid hormone homeostasis of phthalates on pregnant women. However, the effects of cord blood phthalates and prenatal phthalate exposure on thyroid hormones in newborns remain unclear.

OBJECTIVES

We aim to follow up on our previous established subjects and determine the correlation between phthalate exposure and thyroid hormones in pregnant women and newborns.

MATERIALS AND METHODS

We recruited 61 pregnant women from the Obstetrics and Gynecology Department of a medical hospital in southern Taiwan and followed up. High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was used to analyze urine samples for five phthalate metabolites. Serum levels of thyroid hormones were analyzed using electrochemoluminescence immunoassay (ECLIA) method. We used Spearman and Pearson correlation coefficients to evaluate the correlation between each phthalate metabolites in serum and the thyroid hormone levels in fetus and parturient. Finally, multiple logistic regression was used to explore the relationship between hormones and their corresponding phthalate metabolites in cord blood.

RESULTS

High MBP in cord blood was correlated with negative cord serum TSH in newborns (r = -0.25, p < 0.06). By using multiple linear regression after adjusting for potential confounders (gestational and maternal age), cord serum MBP levels showed a negative association with cord serum TSH (β = 0.217, p < 0.05), cord serum T₄ (β = 1.71, p < 0.05) and cord serum T₄ × TSH (β = 42.8, p < 0.05), respectively.

CONCLUSION

We found that levels of cord serum TSH and T₄ in newborns was significantly negatively associated with cord serum MBP levels after adjusting for significant covariate. The fall in TSH in newborns may potentially be delaying their development.

Pollutants delivered every day: Phthalates in plastic express packaging bags and their leaching potential

The rapid development of the express industry brings not only convenience but also environmental problems such as plastic wastes. In this study, we collected plastic express packaging bags from major express companies in China to investigate phthalates in them. Infrared spectra indicated that all these samples were made from polyethylene but with different carbonyl index (CI) values. Total phthalates (∑Phthalates) concentrations in these samples ranged from 11.16 to 309.70 μg g^-1. Di(2-ethylhexyl) phthalate, di-n-butyl phthalate, and di-isobutyl phthalate were predominant phthalates. The leaching amounts of ∑Phthalates after 48 h ranged from 181.44 to 5320.64 ng g^-1. The leaching amounts of ∑Phthalates significantly positively related to ∑Phthalates concentrations of samples, while the leaching ratios presented opposite trends. Concentrations and leaching amounts of ∑Phthalates and major phthalates were significantly higher in samples from high CI value company group than those from low CI value company group. The results of our study indicate that plastic express packaging bags could be a critical source of phthalates. The involving of recycled plastics during the manufacture of plastic express packaging bags may influence the content and composition of phthalates in them and also increase the releasing risk of phthalates.

Aberrations of miR-126-3p, miR-181a and sirtuin1 network mediate Di-(2-ethylhexyl) phthalate-induced testicular damage in rats: The protective role of hesperidin

Recently, oxidative stress was implicated in the environmental contaminant Di-(2-ethylhexyl) phthalate (DEHP)-induced testicular toxicity, however the mechanism is unclear. We investigated the role of oxidative stress-responsive microRNAs in DEHP-induced aberrations and the protective effect of the citrus flavonoid, hesperidin (HSP). Male Wistar rats were randomly allocated into four groups as vehicle-treated control, DEHP-alone group (500 mg/kg/day) for 30 days, and HSP (25 or 50 mg/kg) for 60 days; testicular damage was triggered by oral administration of DEHP (500 mg/kg/day) after thirty days of oral administration of HSP (25 or 50 mg/kg). DEHP administration reduced testis weight coefficient, serum testosterone, testicular 3β-hydroxysteroid dehydrogenase and antioxidant enzyme activities, and elevated serum fatty acid-binding protein-9, testicular malondialdehyde, and Bax/Bcl2 ratio. Aberrant testicular miR-126-3p and miR-181a expression was observed, along with decreased expression of sirtuin1 (SIRT1) and its targets; nuclear factor-erythroid 2-related factor2, haeme oxygenase-1, and superoxide dismutase2. HSP administration significantly ameliorated these changes and restored testicular function in a dose-dependent manner. We highlight a novel role of oxidative stress-miR-126/miR-181a-SIRT1 network in mediating DEHP-induced changes which were reversed by the antioxidant HSP.

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.

Excretion of Urinary Metabolites of the Phthalate Esters DEP and DEHP in 16 Volunteers after Inhalation and Dermal Exposure

Phthalate esters are suspected endocrine disruptors that are found in a wide range of applications. The aim of this study was to determine the excretion of urinary metabolites in 16 individuals after inhalation and/or dermal exposure to 100–300 µg/m³ of deuterium-labelled diethyl phthalate (D₄-DEP) and bis(2-ethylhexyl) phthalate (D₄-DEHP). Dermal exposure in this study represents a case with clean clothing acting as a barrier. After inhalation, D₄-DEP and D₄-DEHP metabolites were excreted rapidly, though inter-individual variation was high. D₄-DEP excretion peaked 3.3 h (T½ of 2.1 h) after combined inhalation and dermal exposure, with total excreted metabolite levels ranging from 0.055 to 2.351 nmol/nmol/m³ (nmol of urinary metabolites per phthalates air concentration in (nmol/m³)). After dermal exposure to D₄-DEP, metabolite excretion peaked 4.6 h (T½ of 2.7 h) after exposure, with excreted metabolite levels in between 0.017 and 0.223 nmol/nmol/m³. After combined inhalation and dermal exposure to D₄-DEHP, the excretion of all five analysed metabolites peaked after 4.7 h on average (T½ of 4.8 h), and metabolite levels ranged from 0.072 to 1.105 nmol/nmol/m³ between participants. No dermal uptake of particle phase D₄-DEHP was observed. In conclusion, the average excreted levels of metabolites after combined inhalation and dermal exposure to D₄-DEP was three times higher than after combined exposure to D₄-DEHP; and nine times higher than after dermal exposure of D₄-DEP. This study was made possible due to the use of novel approaches, i.e., the use of labelled phthalate esters to avoid the background concentration, and innovative technique of phthalate generation, both in the particle and the gas phase.

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.

Comparative study of hydrolytic metabolism of dimethyl phthalate, dibutyl phthalate and di(2-ethylhexyl) phthalate by microsomes of various rat tissues

Phthalates are used in food packaging, and are transferred to foods as contaminants. In this study, we examined the hydrolytic metabolism of dimethyl phthalate (DMP), dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) by rat tissue microsomes. We found that carboxylesterase and lipase contribute differently to these activities. When DMP, DBP and DEHP were incubated with rat liver microsomes, DBP was most effectively hydrolyzed to the phthalate monoester, followed by DMP, and the activity toward DEHP was marginal. In contrast, small-intestinal microsomes exhibited relatively higher activity toward long-side-chain phthalates. Pancreatic microsomes showed high activity toward DEHP and DBP. Liver microsomal hydrolase activity toward DMP was markedly inhibited by bis(4-nitrophenyl)phosphate, and could be extracted with Triton X-100. The activity toward DBP and DEHP was partly inhibited by carboxylesterase inhibitor, and was partly solubilized with Triton X-100. Ces1e, Ces1d and Ces1f expressed in COS cells exhibited the highest hydrolase activity toward DBP, showing a similar pattern to that of liver microsomes. Ces1e showed activity towards DMP and DEHP. Pancreatic lipase also hydrolyzed DBP and DEHP. Thus, carboxylesterase and lipase contribute differently to phthalate hydrolysis: short-side-chain phthalates are mainly hydrolyzed by carboxylesterase and long-side-chain phthalates are mainly hydrolyzed by lipase.

Are nails a valuable non-invasive alternative for estimating human exposure to phthalate esters?

Most human biomonitoring studies conducted in the past year for assessing the human exposure to phthalate esters (PEs) employed measurements of PE metabolites in urine. Although urine is recognized as a valuable non-invasive matrix, it has also limitations regarding the short time window for exposure. Therefore, in this pilot feasibility study we aimed to assess the human exposure to seven PE metabolites (including mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monoethyl phthalate (MEP) and mono-benzyl phthalate (MBzP)) using human nails. Paired nails and urine samples from the same individuals were used for comparison. Median levels of specific PE metabolites measured in nails and in spot urine of twenty Belgian individuals ranged from <LOQ_m to 146ng/g and from 0.2 to 6.7ng/mL (creatinine adjusted), respectively. The major PE metabolites found in nails were MEHP (average 146ng/g), sum (MnBP, MiBP) (average 212ng/g) and MEP (average 205ng/g). Significant correlations were achieved between different metabolites in nails and urine, i.e., MEHP levels in nails correlate well with sum (MnBP, MiBP) (r=0.73, p <0.01) and with MBzP (r=0.52, p <0.05) levels in urine. Moderate correlations were observed between 5-OH-MEHP and sum (MnBP, MiBP) (r=0.62, p <0.01) as well as with MEP (r=0.56, p <0.05) in both matrices. However, no significant correlation was observed for the same metabolite measured in both matrices. Based on participant questionnaires and after performing multivariate statistics, the relevant parameters of exposure positively associated with PE metabolites in nails were the use of hand care products, weight of the individuals and sport activity hours. Based on the detected levels and aforementioned predictors, nails seem a valuable non-invasive matrix for estimating human long-term exposure to DEP, DBnP and/or DIBP and DEHP.

Hidden Toxicity in Neonatal Intensive Care Units: Phthalate Exposure in Very Low Birth Weight Infants

OBJECTIVE

To determine exposure to endocrine-disrupting phthalates in preterm infants in neonatal intensive care units (NICU).

METHODS

Urine samples (n=151) from 36 preterm infants (<32 weeks of gestation and/or <1500 g of birth weight) were collected on the first 3 days of admission to the NICU and biweekly thereafter. Diethylhexyl phthalate contents of indwelling medical devices used in various procedures and the concentrations of phthalate metabolites in the urine samples were analyzed. The relationships between urinary excretion, exposure intensity, postnatal age and birth weight were examined.

RESULTS

The mean gestational age and mean birth weight of the study infants were 28.9±1.5 weeks and 1024±262 g, respectively. Diethylhexyl phthalate was detected in umbilical catheters, endotracheal tubes, nasogastric tubes, and nasal cannula. Monoethylhydroxyhexyl phthalate (MEHHP) was the most frequently detected metabolite (81.4%); its concentration increased during the first 4 weeks and then started to decrease but never disappeared. Patients who did not need indwelling catheters (except nasogastric tubes) after 2 weeks were classified as group 1 and those who continued to have indwelling catheters as group 2. Although not of statistical significance, MEHHP levels decreased in group 1 but continued to stay high in group 2 (in the 4th week, group 1: 65.9 ng/mL and group 2: 255.3 ng/mL). Levels of MEHHP in the first urinary samples were significantly higher in infants with a birth weight <1000 g (<1000 g: 63.2±93.8 ng/mL, ≥1000 g: 10.9±22.9 ng/mL, p=0.001).

CONCLUSION

Phthalate metabolites were detected even in the first urine samples of very low birth weight newborns. Phthalate levels were higher in the first weeks of intensive invasive procedures and in preterm infants with a birth weight less than 1000 g. MEHHP was the most frequently detected metabolite and could be a suitable biomarker for the detection of phthalate exposure in preterm infants.

Ultrasound assisted extraction combined with dispersive liquid-liquid microextraction (US-DLLME)-a fast new approach to measure phthalate metabolites in nails

A new, fast, and environmentally friendly method based on ultrasound assisted extraction combined with dispersive liquid-liquid microextraction (US-DLLME) was developed and optimized for assessing the levels of seven phthalate metabolites (including the mono(ethyl hexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (5-OH-MEHP), mono(2-ethyl-5-oxohexyl) phthalate (5-oxo-MEHP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), monoethyl phthalate (MEP), and mono-benzyl phthalate (MBzP)) in human nails by UPLC-MS/MS. The optimization of the US-DLLME method was performed using a Taguchi combinatorial design (L9 array). Several parameters such as extraction solvent, solvent volume, extraction time, acid, acid concentration, and vortex time were studied. The optimal extraction conditions achieved were 180 μL of trichloroethylene (extraction solvent), 2 mL trifluoroacetic acid in methanol (2 M), 2 h extraction and 3 min vortex time. The optimized method had a good precision (6-17 %). The accuracy ranged from 79 to 108 % and the limit of method quantification (LOQm) was below 14 ng/g for all compounds. The developed US-DLLME method was applied to determine the target metabolites in 10 Belgian individuals. Levels of the analytes measured in nails ranged between <12 and 7982 ng/g. The MEHP, MBP isomers, and MEP were the major metabolites and detected in every sample. Miniaturization (low volumes of organic solvents used), low costs, speed, and simplicity are the main advantages of this US-DLLME based method. Graphical Abstract Extraction and phase separation of the US-DLLME procedure.

Hepatic and intestinal glucuronidation of mono(2-ethylhexyl) phthalate, an active metabolite of di(2-ethylhexyl) phthalate, in humans, dogs, rats, and mice: an in vitro analysis using microsomal fractions

Mono(2-ethylhexyl) phthalate (MEHP) is an active metabolite of di(2-ethylhexyl) phthalate (DEHP) and has endocrine-disrupting effects. MEHP is metabolized into glucuronide by UDP-glucuronosyltransferase (UGT) enzymes in mammals. In the present study, the hepatic and intestinal glucuronidation of MEHP in humans, dogs, rats, and mice was examined in an in vitro system using microsomal fractions. The kinetics of MEHP glucuronidation by liver microsomes followed the Michaelis-Menten model for humans and dogs, and the biphasic model for rats and mice. The K m and V max values of human liver microsomes were 110 µM and 5.8 nmol/min/mg protein, respectively. The kinetics of intestinal microsomes followed the biphasic model for humans, dogs, and mice, and the Michaelis-Menten model for rats. The K m and V max values of human intestinal microsomes were 5.6 µM and 0.40 nmol/min/mg protein, respectively, for the high-affinity phase, and 430 µM and 0.70 nmol/min/mg protein, respectively, for the low-affinity phase. The relative levels of V max estimated by Eadie-Hofstee plots were dogs (2.0) > mice (1.4) > rats (1.0) ≈ humans (1.0) for liver microsomes, and mice (8.5) > dogs (4.1) > rats (3.1) > humans (1.0) for intestinal microsomes. The percentages of the V max values of intestinal microsomes to liver microsomes were mice (120 %) > rats (57 %) > dogs (39 %) > humans (19 %). These results suggest that the metabolic abilities of UGT enzymes expressed in the liver and intestine toward MEHP markedly differed among species, and imply that these species differences are strongly associated with the toxicity of DEHP.

Could exposure to phthalates speed up or delay pubertal onset and development? A 1.5-year follow-up of a school-based population

PURPOSE

Phthalates may interfere with the timing of pubertal development in adolescence and existing studies have shown inconsistent results. This study aims to assess the associations of pubertal onset and progression with urinary concentrations of phthalate metabolites in school-aged boys and girls.

METHODS

Using isotope-dilution liquid chromatography tandem mass spectrometry, we analyzed 6 phthalate metabolites in urine samples of 430 children (222 boys and 208 girls) aged 9.7 ± 2.2 years (age range 6.1 to 13.8 years) at baseline and 18 months of follow-up. The associations of exposures to phthalates with pubertal development such as the testis, breast and pubic hair were evaluated using ordered logistic regression models, adjusting for baseline development stage, current chronological age, current body fat composition, and parental education.

RESULTS

Urinary mono-n-butyl phthalate (MnBP) was associated with a 39% increase in the odds of presenting lower pubic hair development stages in boys, and mono (2-ethylhexyl) phthalate (MEHP) (p < 0.10), mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) were associated with 54%-65% increase in the odds of presenting higher breast development stages in girls (p < 0.05), while MEHHP and MEOHP were also associated with a 70% increase in the odds of menarche onset (p < 0.05). After adjusting for potential confounding variables, the associations of girls' pubertal onset with MnBP, MMP, MEP and MEHP were significant. The odds of girls' breast onset were 4 to 10 times higher in high MnBP, MMP, MEP or MEHP exposure group than in low exposure group.

CONCLUSIONS

Our findings suggest subtle effects of phthalate metabolites associated with pubertal onset and progression. MnBP exposure may be associated with delayed pubic hair development in boys, while MnBP, MMP, MEP, and MEHP exposures may be associated with breast onset, and MEHP metabolites associated with speedup in breast development progression and earlier menarche onset in girls.

The adverse cardiac effects of Di(2-ethylhexyl)phthalate and Bisphenol A

The ubiquitous nature of plastics has raised concerns pertaining to continuous exposure to plastic polymers and human health risks. Of particular concern is the use of endocrine-disrupting chemicals in plastic production, including di(2-ethylhexyl)phthalate (DEHP) and bisphenol A (BPA). Widespread and continuous exposure to DEHP and BPA occurs through dietary intake, inhalation, dermal and intravenous exposure via consumer products and medical devices. This article reviews the literature examining the relationship between DEHP and BPA exposure and cardiac toxicity. In vitro and in vivo experimental reports are outlined, as well as epidemiological studies which examine the association between these chemicals and cardiovascular outcomes. Gaps in our current knowledge are also discussed, along with future investigative endeavors that may help resolve whether DEHP and/or BPA exposure has a negative impact on cardiovascular physiology.

Association of Exposure to Di-2-Ethylhexylphthalate Replacements With Increased Insulin Resistance in Adolescents From NHANES 2009-2012

CONTEXT

Di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP) are environmental chemicals increasingly used to replace di-2-ethylhexylphthalate (DEHP) and commonly found in processed foods. Phthalate exposures, in particular DEHP, have been associated with insulin resistance in adolescents, but there are no data regarding the two substitutes, DINP and DIDP.

OBJECTIVE

This study aimed to examine associations of DINP, DIDP, and DEHP with insulin resistance outcomes.

DESIGN, SETTING, AND PARTICIPANTS

This was a cross-sectional analysis of 2009-2012 National Health and Nutrition Examination Surveys (NHANES) composed of 356 fasting 12-19-year-olds.

MAIN OUTCOME MEASURES

Insulin resistance as a categorical outcome expressed as homeostatic model assessment of insulin resistance (HOMA-IR), using a cut point of 4.39 to define insulin resistance. We also examined continuous HOMA-IR as an outcome in secondary analyses.

RESULTS

Controlling for demographic and behavioral factors, diet, age, body mass index, and urinary creatinine, for each log increase in DINP metabolite, a 0.08 (P = .001) increase in HOMA-IR was identified. Compared with the first tertile of DINP (23.4% adjusted prevalence), the third tertile was associated with a 34.4% prevalence (95% confidence interval [CI], 27.3-41.6%; P = .033) of insulin resistance. Similarly, compared with the first tertile of DEHP (20.5% adjusted prevalence), the third tertile had 37.7% prevalence (95% CI 29.8-45.6%; P = .003).

CONCLUSIONS

Urinary DINP concentrations were associated with increased insulin resistance in this cross-sectional study of adolescents. The previously identified association of DEHP with insulin resistance was also confirmed. Further, longitudinal studies are needed to confirm these associations, with the possibility to assess opportunities for intervention.

Di-(2-ethylhexyl) phthalate metabolites in urine show age-related changes and associations with adiposity and parameters of insulin sensitivity in childhood

OBJECTIVES

Phthalates might be implicated with obesity and insulin sensitivity. We evaluated the levels of primary and secondary metabolites of Di-(2-ethylhexyl) phthalate (DEHP) in urine in obese and normal-weight subjects both before and during puberty, and investigated their relationships with auxological parameters and indexes of insulin sensitivity.

DESIGN AND METHODS

DEHP metabolites (MEHP, 6-OH-MEHP, 5-oxo-MEHP, 5-OH-MEHP, and 5-CX-MEHP), were measured in urine by RP-HPLC-ESI-MS. Traditional statistical analysis and a data mining analysis using the Auto-CM analysis were able to offer an insight into the complex biological connections between the studied variables.

RESULTS

The data showed changes in DEHP metabolites in urine related with obesity, puberty, and presence of insulin resistance. Changes in urine metabolites were related with age, height and weight, waist circumference and waist to height ratio, thus to fat distribution. In addition, clear relationships in both obese and normal-weight subjects were detected among MEHP, its products of oxidation and measurements of insulin sensitivity.

CONCLUSION

It remains to be elucidated whether exposure to phthalates per se is actually the risk factor or if the ability of the body to metabolize phthalates is actually the key point. Further studies that span from conception to elderly subjects besides further understanding of DEHP metabolism are warranted to clarify these aspects.

Metabolism of di (2-ethylhexyl) phthalate (DEHP): comparative study in juvenile and fetal marmosets and rats

We compared the metabolic profile of di (2-ethylhexyl) phthalate (DEHP) in juveniles and fetus between rats and marmosets. STUDY-I: (14)C-DEHP (100 and 2,500 mg/kg) was singly administered to juvenile and adult marmosets by gavage. C(max) of the radioactivity in juvenile marmosets was 6.45 and 31 µg eq./g, respectively. The radioactivity excreted mainly into feces; however, at least 10% of the radioactivity was absorbed even at 2,500 mg/kg. No abnormal accumulation was observed in the male reproductive organs. STUDY-II: (14)C-DEHP (100 mg/kg) was singly administered to juveniles of rat and marmoset. The plasma radioactivity in marmosets was about 5% to 9% of that in rats. Free forms of mono-2-ethylhexyl phthalate (MEHP) and its oxidized metabolites such as oxo-, OH-, and COOH-MEHP were detected as the main compositions in rat plasma. In marmosets, free form of MEHP was also detected as a major composition, but not for oxidized MEHP metabolites. In rats, oxidized MEHP metabolites were excreted into urine as unconjugated forms. MEHP and its oxidized metabolites were also detected in marmoset urine; however, they were mostly glucuronized. No specific accumulation of the radioactivity was noted in the testes of either species; however, the radioactivity concentration in the marmoset testes was much lower than that in rats. STUDY-III: (14)C-DEHP (100 mg/kg) was singly administered to dams on gestation day 130 for marmosets and day 20 for rats. In either species, no specific accumulation of radioactivity was noted in the testis of fetuses from the dams treated with (14)C-DEHP; however, the radioactivity in the rat testis was about 20-times higher than that in the marmoset. Major metabolite components in rat whole fetal tissue were free forms of MEHP, OH-MEHP, and oxo-MEHP. Free form of MEHP was also detected as only a peak in the marmoset fetal tissue.

PPARalpha- and DEHP-Induced Cancers

Di(2-ethylhexyl)phthalate (DEHP) is a widely used plasticizer and a potentially nongenotoxic carcinogen. Its mechanism had been earlier proposed based on peroxisome proliferator-activated receptor α (PPARα) because metabolites of DEHP are agonists. However, recent evidence also suggests the involvement of non-PPARα multiple pathway in DEHP-induced carcinogenesis. Since there are differences in the function and constitutive expression of PPARα among rodents and humans, species differences are also thought to exist in the carcinogenesis. However, species differences were also seen in the lipase activity involved in the first step of the DEHP metabolism, which should be considered in DEHP-induced carcinogenesis. Taken together, it is very difficult to extrapolate the results from rodents to humans in the case of DEHP carcinogenicity. However, PPARα-null mice or mice with human PPARα gene have been developed, which may lend support to make such a difficult extrapolation. Overall, further mechanical study on DEHP-induced carcinogenicity is warranted using these mice.

Biological monitoring of exposure to di(2-ethylhexyl) phthalate in six French factories: a field study

OBJECTIVE

The aim of this study was to assess, by biological monitoring, workers' exposure to di(2-ethylhexyl) phthalate (DEHP) in the flexible-PVC industry in France to provide additional occupational exposure data, which are particularly scarce.

METHOD

Over 5 days of pre-and post-shift sampling, three urinary metabolites of DEHP, mono (2-ethylhexyl) phthalate (MEHP), mono (5-carboxy-2-ethylpentyl) phthalate (5cx-MEPP) and 2-ethylhexanoic acid (2-EHA) were quantified in 62 workers and 29 controls from six factories. Analyses were performed by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) after on-line extraction.

RESULTS

Median concentrations of the pre- and post-shift urinary samples in the exposed workers were 12.6 and 28.7 μg/l for MEHP, 38.6 and 84.4 μg/l for 5cx-MEPP and 20.4 and 70.6 μg/l for 2-EHA, respectively. In the controls, the corresponding values were 4.8 and 4.7 μg/l for MEHP, 15.1 and 12.4 μg/l for 5cx-MEPP and 21.8 and 20.5 μg/l for 2-EHA, respectively. There was a significant increase (Mann-Whitney U-test, P < 0.05) of post-shift excretion in the exposed workers versus the unexposed controls and in the post-shift versus pre-shift concentrations only in the exposed workers. Values of 250 and 500 μg/l (100 and 280 μ/g creatinine) for MEHP and 5cx-MEPP, respectively, are proposed as guidance values.

CONCLUSION

There is clear evidence of occupational exposure of workers in these factories. The guideline values proposed should prevent high exposures in the soft PVC industry, particularly in factories where DEHP compounds or plastisols are employed. An epidemiological survey is needed to complete the DEHP risk assessment.

What additional factors beyond state-of-the-art analytical methods are needed for optimal generation and interpretation of biomonitoring data?

BACKGROUND

The routine use of biomonitoring (i.e., measurement of environmental chemicals, their metabolites, or specific reaction products in human biological specimens) to assess internal exposure (i.e., body burden) has gained importance in exposure assessment.

OBJECTIVES

Selection and validation of biomarkers of exposure are critical factors in interpreting biomonitoring data. Moreover, the strong relation between quality of the analytical methods used for biomonitoring and quality of the resulting data is well understood. However, the relevance of collecting, storing, processing, and transporting the samples to the laboratory to the overall biomonitoring process has received limited attention, especially for organic chemicals.

DISCUSSION

We present examples to illustrate potential sources of unintended contamination of the biological specimen during collection or processing procedures. The examples also highlight the importance of ensuring that the biological specimen analyzed both represents the sample collected for biomonitoring purposes and reflects the exposure of interest.

CONCLUSIONS

Besides using high-quality analytical methods and good laboratory practices for biomonitoring, evaluation of the collection and handling of biological samples should be emphasized, because these procedures can affect the samples integrity and representativeness. Biomonitoring programs would be strengthened with the inclusion of field blanks.

Urinary phthalate metabolites in relation to preterm birth in Mexico city

BACKGROUND

Rates of preterm birth have been rising over the past several decades. Factors contributing to this trend remain largely unclear, and exposure to environmental contaminants may play a role.

OBJECTIVE

We investigated the relationship between phthalate exposure and preterm birth.

METHODS

Within a large Mexican birth cohort study, we compared third-trimester urinary phthalate metabolite concentrations in 30 women who delivered preterm (< 37 weeks of gestation) with those of 30 controls (> or = 37 weeks of gestation).

RESULTS

Concentrations of most of the metabolites were similar to those reported among U.S. females, although in the present study mono-n-butyl phthalate (MBP) concentrations were higher and monobenzyl phthalate (MBzP) concentrations lower. In a crude comparison before correcting for urinary dilution, geometric mean urinary concentrations were higher for the phthalate metabolites MBP, MBzP, mono(3-carboxylpropyl) phthalate, and four metabolites of di(2-ethyl-hexyl) phthalate among women who subsequently delivered preterm. These differences remained, but were somewhat lessened, after correction by specific gravity or creatinine. In multivariate logistic regression analysis adjusted for potential confounders, elevated odds of having phthalate metabolite concentrations above the median level were found.

CONCLUSIONS

We found that phthalate exposure is prevalent among this group of pregnant women in Mexico and that some phthalates may be associated with preterm birth.

Use of di(2-ethylhexyl)phthalate-containing infusion systems increases the risk for cholestasis

INTRODUCTION

Most polyvinylchloride infusion systems are plasticized with up to 60% of di(2-ethylhexyl)phthalate (DEHP). DEHP is easily extracted from the tubing by total parenteral nutrition (TPN) solutions and has been shown to have toxic effects on various organ systems including the liver in animals and humans. A role was postulated for DEHP in the development of hepatobiliary dysfunction in premature and newborn infants receiving parenteral nutrition, and the incidence of cholestasis was investigated after changing from polyvinylchloride infusion systems to polyvinylchloride-free infusion systems.

MATERIALS AND METHODS

Two 3-year periods from 1998 to 2004 were investigated retrospectively before and after changing from polyvinylchloride to polyvinylchloride-free infusion systems in our department. This resulted in 1 group of 30 patients treated with polyvinylchloride lines and a second group of 46 patients treated with polyvinylchloride-free lines. The 2 groups were examined for the incidence of cholestasis and other possible contributing factors. Statistics were performed by using SAS software (SAS Institute, Cary, NC).

RESULTS

After changing infusion systems, the incidence of cholestasis dropped from 50% to 13%. Using DEHP-plasticized polyvinylchloride infusion systems for TPN increased the risk for cholestasis by a factor of 5.6. The use of polyvinylchloride lines correlated strongly with the development of TPN-associated cholestasis (P = .0004).

CONCLUSIONS

Using DEHP-containing polyvinylchloride infusions systems contributes to the development of cholestasis. Therefore, the use of DEHP-free infusion systems for TPN is recommended, especially in premature and newborn infants.

Urinary metabolites of di(2-ethylhexyl) phthalate are associated with decreased steroid hormone levels in adult men

Experimental animal studies have demonstrated that exposure to some phthalates may be associated with altered endocrine function and adverse effects on male reproductive development and function, but human studies are limited. In the present study, urine and serum samples were collected from 425 men recruited through a US infertility clinic. Urinary concentrations of mono(2-ethylhexyl) phthalate (MEHP), the hydrolytic metabolite of di(2-ethylhexyl) phthalate (DEHP), and other phthalate monoester metabolites were measured, along with serum levels of testosterone, estradiol, sex hormone-binding globulin (SHBG), follicle-stimulating hormone, luteinizing hormone, inhibin B, and prolactin. Two oxidized urinary metabolites of DEHP were also measured in urine from 221 of the men. In multiple regression models adjusted for potential confounders, MEHP was inversely associated with testosterone, estradiol, and free androgen index (FAI). An interquartile range increase in MEHP was associated with 3.7% (95% confidence interval [CI], -6.8% to -0.5%) and 6.8% (95% CI, -11.2% to -2.4%) declines in testosterone and estradiol, respectively, relative to the population median hormone levels. There was limited evidence for effect modification of the inverse association between MEHP and FAI by the proportion of DEHP metabolites in the urine measured as MEHP (MEHP%), which is considered a phenotypic marker of less efficient metabolism of DEHP to its oxidized metabolites. Finally, the ratio of testosterone to estradiol was positively associated with MEHP (P = .07) and MEHP% (P = .007), suggesting potential relationships with aromatase suppression. In conclusion, these results suggest that urinary metabolites of DEHP are inversely associated with circulating steroid hormone levels in adult men. However, additional research is needed to confirm these findings.

Urinary metabolite concentrations of organophosphorous pesticides, bisphenol A, and phthalates among pregnant women in Rotterdam, the Netherlands: the Generation R study

Concern about potential health impacts of low-level exposures to organophosphorus (OP) pesticides, bisphenol A (BPA), and phthalates among the general population is increasing. We measured levels of six dialkyl phosphate (DAP) metabolites of OP pesticides, a chlorpyrifos-specific metabolite (3,5,6-trichloro-2-pyridinol, TCPy), BPA, and 14 phthalate metabolites in urine samples of 100 pregnant women from the Generation R study, the Netherlands. The unadjusted and creatinine-adjusted concentrations were reported, and compared to National Health and Nutrition Examination Survey and other studies. In general, these metabolites were detectable in the urine of the women from the Generation R study and compared with other groups, they had relatively high-level exposures to OP pesticides and several phthalates but similar exposure to BPA. The median concentrations of total dimethyl (DM) metabolites was 264.0 n mol/g creatinine (Cr) and of total DAP was 316.0 n mol/g Cr. The median concentration of mono-ethyl phthalate (MEP) was 222.0 microg/g Cr; the median concentrations of mono-isobutyl phthalate (MiBP) and mono-n-butyl phthalate (MnBP) were above 50 microg/g Cr. The median concentrations of the three secondary metabolites of di-2-ethylhexyl phthalate (DEHP) were greater than 20 microg/g Cr. The data indicate that the Generation R study population provides a wide distribution of selected environmental exposures. Reasons for the relatively high levels and possible health effects need investigation.

A pilot study associating urinary concentrations of phthalate metabolites and semen quality

Phthalates are ubiquitous industrial chemicals that are reported to adversely affect human reproductive outcomes. Divergent effects on semen quality have been reported in a limited number of studies. To assess the possible contribution of regional differences in phthalate exposure to these results, we wished to determine if ambient phthalate exposure of men from the Great Lakes region was associated with human sperm parameters. Male partners (N=45) of subfertile couples presenting to a Michigan infertility clinic were recruited. Urinary concentrations of several phthalate metabolites were measured in these men. Semen parameters, measured according to the World Health Organization [WHO 1999] protocols, were divided into those at or above WHO cutoffs for motility (50% motile), concentration (20 million/mL) and morphology (4% normal) and those below. Phthalate metabolite concentrations were divided into those concentrations above the median and those at or below the median. Specific gravity was used as a covariate in the regression models to adjust for urine dilution. Low sperm concentration was significantly associated with above median concentrations of monoethyl phthalate (MEP) (OR=6.5, 95% CI: 1.0-43.6) and low morphology with above median concentrations of mono-3-carboxypropyl phthalate (OR=7.6, 95% CI: 1.7-33.3). Increased odds for low concentration and above median concentrations of metabolites of di(2-ethylhexyl) phthalate (DEHP) (OR=5.4, 95% CI: 0.9-30.8) and low morphology and above median concentrations of MEP (OR=3.4, 95% CI: 0.9-13.8) were also found. A significant trend was observed for tertiles of MEP and low sperm concentration (p=0.05). Results suggest that ambient phthalate metabolite concentrations may adversely affect human semen quality.

Di(2-ethylhexyl) phthalate metabolites may alter thyroid hormone levels in men

BACKGROUND

Phthalates are used extensively in many personal-care and consumer products, resulting in widespread nonoccupational human exposure through multiple routes and media. A limited number of animal studies suggest that exposure to phthalates may be associated with altered thyroid function, but human data are lacking.

METHODS

Concurrent samples of urine and blood were collected from 408 men. We measured urinary concentrations of mono(2-ethylhexyl) phthalate (MEHP), the hydrolytic metabolite of di(2-ethylhexyl) phthalate (DEHP), and other phthalate monoester metabolites, along with serum levels of free thyroxine (T(4)), total triiodothyronine (T(3)), and thyroid-stimulating hormone (TSH). Oxidative metabolites of DEHP were measured in urine from only 208 of the men.

RESULTS

We found an inverse association between MEHP urinary concentrations and free T(4) and T(3) serum levels, although the relationships did not appear to be linear when MEHP concentrations were categorized by quintiles. There was evidence of a plateau at the fourth quintile, which was associated with a 0.11 ng/dL decrease in free T(4) [95% confidence interval (CI), -0.18 to -0.03] and a 0.05 ng/mL decrease in T(3) (95% CI, -0.10 to 0.01) compared with the first (lowest) MEHP quintile. The inverse relationship between MEHP and free T(4) remained when we adjusted for oxidative metabolite concentrations; this simultaneously demonstrated a suggestive positive association with free T(4).

CONCLUSIONS

Urinary MEHP concentrations may be associated with altered free T(4) and/or total T(3) levels in adult men, but additional study is needed to confirm the observed findings. Future studies must also consider oxidative DEHP metabolites relative to MEHP as a potential marker of metabolic susceptibility to DEHP exposure.

Internal phthalate exposure over the last two decades--a retrospective human biomonitoring study

In a retrospective human biomonitoring study we analyzed 24h urine samples taken from the German Environmental Specimen Bank for Human Tissues (ESBHum), which were collected from 634 subjects (predominantly students, age range 20-29 years, 326 females, 308 males) in 9 years between 1988 and 2003 (each n >or= 60), for the concentrations of primary and/or secondary metabolites of di-n-butyl phthalate (DnBP), di-iso-butyl phthalate (DiBP), butylbenzyl phthalate (BBzP), di(2-ethylhexyl) phthalate (DEHP) and di-iso-nonyl phthalate (DiNP). Based on the urinary metabolite excretion we estimated daily intakes of the parent phthalates and investigated the chronological course of the phthalate exposure. In over 98% of the urine samples metabolites of all five phthalates were detectable indicating a ubiquitous exposure of the German population to all five phthalates throughout the last 20 years. The median daily intakes in the subsets between 1988 and 1993 were quite constant for DnBP (approx. 7 microg/kg bw/d) and DEHP (approx. 4 microg/kg bw/d). However, from 1996 the median levels of both phthalates decreased continuously until 2003 (DnBP 1.9 microg/kg bw/d; DEHP 2.4 microg/kg bw/d). By contrast, the daily intake values for DiBP were slightly increasing over the whole time frame investigated (median 1988: 1.1 microg/kg bw/d; median 2003: 1.4 microg/kg bw/d), approximating the levels for DnBP and DEHP. For BBzP we observed slightly decreasing values, even though the medians as of 1998 levelled off at around 0.2 microg/kg bw/d. Regarding daily DiNP exposure we found continuously increasing values, with the lowest median being 0.20 microg/kg bw/d for the subset of 1988 and the highest median for 2003 being twice as high. The trends observed in phthalate exposure may be associated with a change in production and usage pattern. Female subjects exhibited significantly higher daily intakes for the dibutyl phthalates (DnBP p=0.013; DiBP p=0.004). Compared to data from US National Health and Nutrition Examination Surveys (NHANES) exposure levels of the dibutyl phthalates were generally higher in our German study population, while levels of BBzP were somewhat lower. Overall, for a considerable 14% of the subjects we observed daily DnBP intakes above the tolerable daily intake (TDI) value deduced by the European Food Safety Authority (EFSA) (10 microg/kg bw/d). However, the frequency of exceedance decreased during the years and was beneath 2% in the 2003 subset. Even though transgressions of the exposure limit values of the EFSA and the US Environmental Protection Agency (US EPA) occurred only in a relatively small share of the subjects, one has to take into account the cumulative exposure to all phthalates investigated and possible dose-additive endocrine effects of these phthalates.

Altered semen quality in relation to urinary concentrations of phthalate monoester and oxidative metabolites

BACKGROUND

Phthalates are multifunctional chemicals used in a variety of consumer, medical, and personal care products. Previously, we reported dose-response associations of decreased semen quality with urinary concentrations of monobutyl phthalate (MBP) and monobenzyl (MBzP) phthalate, which are metabolites of dibutyl phthalate and butylbenzyl phthalate, respectively. The present study extends our work in a larger sample of men and includes measurements of di(2-ethylhexyl) phthalate (DEHP) oxidative metabolites.

METHODS

Between January 2000 and May 2004, we recruited 463 male partners of subfertile couples who presented for semen analysis to the Massachusetts General Hospital. Semen parameters were dichotomized based on World Health Organization reference values for sperm concentration (<20 million/mL) and motility (<50% motile) and the Tygerberg Kruger Strict criteria for morphology (<4% normal). The comparison group was men with all 3 semen parameters above the reference values. In a single spot urine sample from each man, phthalate metabolites were measured using solid-phase extraction coupled to high-performance liquid chromatography isotope-dilution tandem mass spectrometry.

RESULTS

There were dose-response relationships of MBP with low sperm concentration (odds ratio per quartile adjusted for age, abstinence time, and smoking status = 1.00, 3.1, 2.5, 3.3; P for trend = 0.04) and motility (1.0, 1.5, 1.5, 1.8; P for trend = 0.04). There was suggestive evidence of an association between the highest MBzP quartile and low sperm concentration (1.00, 1.1, 1.1, 1.9; P for trend = 0.13). There were no relationships of monoethyl phthalate, monomethyl phthalate, and the DEHP metabolites with these semen parameters.

CONCLUSION

The present study confirms previous results on the relationship of altered semen quality with exposure to MBP at general population levels. We did not find associations between semen parameters and 3 DEHP metabolites.

Daily intake of di(2-ethylhexyl)phthalate (DEHP) by German children -- A comparison of two estimation models based on urinary DEHP metabolite levels

Di(2-ethylhexyl)phthalate (DEHP) is a general-purpose plasticizer for polyvinyl chloride (PVC) and has become a ubiquitous environmental contaminant. It is suspected to be an endocrine disrupting/modulating substance in humans. Children are of special concern due to their developmental state. In our study we estimated the daily DEHP intake of 239 children aged 2-14 years by extrapolating from their urinary levels of the DEHP metabolites mono-(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP) and mono-(2-ethylhexyl)phthalate (MEHP). We applied two calculation models based upon the volume and the creatinine-related urinary metabolite concentrations. Applying the volume- or the creatinine-based calculation model we determined a median daily DEHP intake of 7.8 or 4.3 microg/kgbody weight (bw)/day and a 95th percentile of 25.2 or 15.2 microg/kgbw/day. Three children (1%) exceeded the value of the tolerable daily intake (TDI) of the European Food Safety Authority of 50 microg/kgbw/day, while 7.5% or 3% (depending on the calculation model) exceeded the reference dose (RfD) of 20 microg/kgbw/day of the US Environmental Protection Agency. In general, DEHP exposure was decreasing with increasing age and boys had higher exposures than girls. Our findings suggest that the majority of the children in the general population is exposed to quantities of DEHP below the TDI and the RfD. However, many children scoop out the preventive limit values to a considerable degree and in individual cases we observed substantial transgressions. Younger children seem to be more severely burdened, which may be due to a higher food consumption related to their bw, mouthing behaviour and/or playing near the ground.

DNA damage in human sperm is related to urinary levels of phthalate monoester and oxidative metabolites

BACKGROUND

The ubiquitous use of phthalate esters in plastics, personal care products and food packaging materials results in widespread general population exposure. In this report, we extend our preliminary study on the relationship between urinary concentrations of phthalate metabolites and sperm DNA damage among a larger sample of men and include measurements of mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), two oxidative metabolites of di-(2-ethylhexyl) phthalate (DEHP).

METHODS

Among 379 men from an infertility clinic, urinary concentrations of phthalate metabolites were measured using isotope-dilution high-performance liquid chromatography-tandem mass spectrometry. Sperm DNA damage measurements, assessed with the neutral comet assay, included comet extent (CE), percentage of DNA in tail (Tail%) and tail distributed moment (TDM).

RESULTS

Monoethyl phthalate (MEP), a metabolite of diethyl phthalate, was associated with increased DNA damage, confirming our previous findings. Mono-(2-ethylhexyl) phthalate (MEHP), a metabolite of DEHP, was associated with DNA damage after adjustment for the oxidative DEHP metabolites. After adjustment for MEHHP, for an interquartile range increase in urinary MEHP, CE increased 17.3% [95% confidence interval (CI) = 8.7-25.7%], TDM increased 14.3% (95% CI = 6.8-21.7%) and Tail% increased 17.5% (95% CI = 3.5-31.5%).

CONCLUSIONS

Sperm DNA damage was associated with MEP and with MEHP after adjusting for DEHP oxidative metabolites, which may serve as phenotypic markers of DEHP metabolism to 'less toxic' metabolites. The urinary levels of phthalate metabolites among these men were similar to those reported for the US general population, suggesting that exposure to some phthalates may affect the population distribution of sperm DNA damage.