NTP Center for the Evaluation of Risks to Human Reproduction: phthalates expert panel report on the reproductive and developmental toxicity of di-isononyl phthalate

Non-Apoptotic Programmed Cell Death in Thyroid Diseases

Thyroid disorders are among the most common endocrinological conditions. As the prevalence of thyroid diseases increases annually, the exploration of thyroid disease mechanisms and the development of treatments are also gradually improving. With the gradual advancement of therapies, non-apoptotic programmed cell death (NAPCD) has immense potential in inflammatory and neoplastic diseases. Autophagy, pyroptosis, ferroptosis, and immunogenic cell death are all classical NAPCD. In this paper, we have compiled the recent mechanistic investigations of thyroid diseases and established the considerable progress by NAPCD in thyroid diseases. Furthermore, we have elucidated the role of various types of NAPCD in different thyroid disorders. This will help us to better understand the pathophysiology of thyroid-related disorders and identify new targets and mechanisms of drug resistance, which may facilitate the development of novel diagnostic and therapeutic strategies for patients with thyroid diseases. Here, we have reviewed the advances in the role of NAPCD in the occurrence, progression, and prognosis of thyroid diseases, and highlighted future research prospects in this area.

Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men

Male reproductive health has declined as indicated by increasing rates of cryptorchidism, i.e., undescended testis, poor semen quality, low serum testosterone level, and testicular cancer. Exposure to endocrine disrupting chemicals (EDCs) has been proposed to have a role in this finding. In utero exposure to antiandrogenic EDCs, particularly at a sensitive period of fetal testicular development, the so-called 'masculinization programming window (MPW)', can disturb testicular development and function. Low androgen effect during the MPW can cause both short- and long-term reproductive disorders. A concurrent exposure to EDCs may also affect testicular function or damage testicular cells. Evidence from animal studies supports the role of endocrine disrupting chemicals in development of male reproductive disorders. However, evidence from epidemiological studies is relatively mixed. In this article, we review the current literature that evaluated relationship between prenatal EDC exposures and anogenital distance, cryptorchidism, and congenital penile abnormality called hypospadias. We review also studies on the association between early life and postnatal EDC exposure and semen quality, hypothalamic-pituitary-gonadal axis hormone levels and testicular cancer.

Influence of in utero di-n-hexyl phthalate and di-cyclohexyl phthalate exposure on the endocrine glands and T3, T4, and TSH hormone levels of male and female rats: Postnatal outcomes

The present study was designed to evaluate the effects of di-n-hexyl phthalate (DHP) and di-cyclohexyl phthalate (DCHP) on endocrine organs in rats. Oil control, 20-, 100-, and 500 mg/kg dose groups were selected and administered to pregnant rats on gestational days 6-19 by oral gavage. The neonatal stages of rats continued until postnatal day 20 and the- juvenile stages of rats continued until postnatal day of 32. The rats were allowed to mature until the neonatal and juvenile stages and there after, they were divided into four groups corresponding to the treatment levels. Body and organ weights were recorded, serum was collected, and thyroid, pancreas, pituitary gland, and adrenal gland were removed. There was a decrease in body weights in the 20- and 500mg/kg DHP and in the 20-mg/kg DCHP dose groups in neonatal male rats. In contrast, for female rats, there was an increase in body weights in the 100-mg/kg DCHP dose group and there was a decrease in body weights in the 500-mg/kg DHP dose group. Body weights were increased at 20 and 500 mg/kg in the DHP-exposed juvenile male rats. Serum thyroid-stimulating hormone (TSH) levels were increased in neonatal male rats, while they were increased in the 100-mg/kg DHP group of neonatal and juvenile female rats. Serum triiodothyronine (T3) levels were increased at the high dose of DHP for neonatal male rats and at the low and high dose levels of DCHP for female rats. Serum thyroxine (T4) levels were increased in neonatal rats for DHP. Also, some histopathological changes were observed in the thyroid, pancreas, adrenal, and pituitary gland. In conclusion, it was shown that DHP and DCHP caused negative effects on T3, T4, and TSH hormone levels.

The Effects of Selected Phenol and Phthalate Derivatives on Steroid Hormone Production by Cultured Porcine Granulosa Cells

We have investigated the effects of several phenols (octylphenol [OP], nonylphenol [NP], tert-octylphenol [tOP]) and phthalates (dioctylphthalate [DOP], diisodecylphthalate [DiDP], diisononylphthalate [DiNP]) on steroid hormone production by porcine ovarian granulosa cells after a 72-hour incubation. These chemicals are widely used as plasticisers and are suspected to possess endocrine disrupting properties. No changes were exhibited in basal progesterone production after treatment with NP or tOP, or with the tested phthalates. However, OP tended to decrease progesterone levels, while DOP and DiDP, at the lowest concentration used (10(-8)M), increased progesterone levels in the culture media. Neither of the tested phenols affected follicle stimulating hormone (FSH)-stimulated progesterone production, except for OP and NP at 10(-4)M, which decreased progesterone levels. The phthalates, tested at higher concentrations, were able to amplify FSH-stimulated progesterone release into the culture medium. An inhibitory action on oestradiol production by porcine granulosa cells was observed after the treatment with both groups of test chemicals. The results obtained in the experiments on primary granulosa cell cultures indicate that ovarian steroidogenesis might be one of the possible sites affected by the endocrine disrupting actions of phenols and phthalates.

DINP aggravates autoimmune thyroid disease through activation of the Akt/mTOR pathway and suppression of autophagy in Wistar rats

Di-isononyl phthalate (DINP) is used as a substitute for traditional phthalates, in a wide range of applications. However, there is growing concern regarding its toxicity. Studies have indicated that DINP is related to thyroid hormone disorder and that phthalates can affect thyroid normal function. In this study, we aim to determine any effects of DINP exposure on autoimmune thyroid disease (AITD), the most common autoimmune disease, and to understand the underlying causal mechanism. AITD model Wistar rats were exposed to 0.15 mg/kg, 1.5 mg/kg or 15 mg/kg DINP. We assessed the thyroid globulin antibody levels, Th1/Th2 balance, histopathological changes and caspase-3 levels in the thyroid. The data show that exposure to DINP does indeed aggravate AITD. To explore the underlying mechanisms, we examined the levels of microtubule-associated protein 1 light chain 3 B (LC3B), Sequestosome 1 (SQSTM1) and the appearance of autophagosomes or autolysosomes to assess autophagy in the thyroid. The results show that DINP can suppress normal autophagy. We found that DINP induced an exacerbation of oxidative stress and the activation of the Akt/mTOR pathway, indicating that oxidative stress and activation of mTOR may play a key role in these processes. Moreover, the activation of mTOR also promoted the expression of IL-17. Importantly, blocking oxidative stress with VE or blocking Akt/mTOR with rapamycin mitigated the exacerbation of AITD and the suppression of normal autophagy. All these results indicate that exposure to DINP, especially high doses of DINP, can aggravate oxidative stress and activate the Akt/mTOR pathway. This exposure then leads to a suppression of normal autophagy and expression of IL-17 in the thyroid, resulting in an eventual exacerbation of AITD.

Crosstalk between unfolded protein response and Nrf2-mediated antioxidant defense in Di-(2-ethylhexyl) phthalate-induced renal injury in quail (Coturnix japonica)

The widely used Di-(2-ethylhexyl) phthalate (DEHP) has been reported to exhibit ubiquitous environmental and global health hazards. The bioaccumulation and environmental persistence of DEHP can cause serious health hazards in wildlife animals and human. However, DEHP-induced nephrotoxicity in bird is remained unknown. Thus, this study explored the related mechanism of DEHP nephrotoxicity in quail. For this purpose, quail were exposed with DEHP at doses of 0, 250, 500, and 1000 mg/kg body weight daily by gavage administration for 45 days. The results showed that DEHP exposure induced renal injury, oxidative stress, and endoplasmic reticulum (ER) degeneration. Low level DEHP (250 mg/kg) exposure inhibited Nrf2 signaling pathway and induced renal injury via oxidative stress and suppressed the unfolded protein response (UPR) signaling pathway and induced ER stress in the kidney. But surprisingly, high level DEHP (500 mg/kg and 1000 mg/kg) exposure activated Nrf2 and UPR signaling pathways and protected kidney, but they still couldn't resist the toxicity of DEHP. Our study demonstrated that DEHP-induced nephrotoxicity in quail was associated with activating Nrf2-mediated antioxidant defense response and UPR signaling pathway.

Exposure Marker Discovery of Phthalates Using Mass Spectrometry

Phthalates are chemicals widely used in industry and the consequences on human health caused by exposure to these agents are of significant interest currently. The urinary metabolites of phthalates can be measured and used as exposure markers for the assessment of the actual internal contamination of phthalates coming from different sources and absorbed by various ways. The purpose of this paper is to review the markers for exposure and risk assessment of phthalates such as di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-butyl phthalate (DBP), benzylbutyl phthalate (BBP), di-(2-ethylhexyl)phthalate (DEHP), di-(2-propylheptyl)phthalate (DPHP), di-iso-nonyl phthalate (DINP), di-n-octyl phthalate (DnOP) and di-iso-decyl phthalate (DIDP), and introduction of the analytical approach of three metabolomics data processing approaches that can be used for chemical exposure marker discovery in urine with high-resolution mass spectrometry (HRMS) data.

Occurrence, spatial distribution, historical trend and ecological risk of phthalate esters in the Jiulong River, Southeast China

The occurrence and spatial distribution of phthalate esters (PAEs) in the Jiulong River of southeast China were investigated in water and sediment samples collected from 35 stations along the river in Mar. 2014. The historical trend of the past 26years was reconstructed with a sediment core collected in Dec. 2012 via a ²¹⁰Pb dating technique. The potential ecological risk of PAEs was assessed using the risk quotient (RQ) method. Of the 16 PAE congeners analyzed, only 6 PAEs, including dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), di-n-butyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DINP), were identified and quantified; the remaining 10 PAEs were below their respective limits of quantification (LOQs) for the analytical methods used here. The cumulative concentration of 6 PAEs (∑₆PAEs) found in the samples spanned a range of 3.48-17.7μg/L in water and 0.046-1.65mg/kg in sediment. The most abundant PAEs in the water-phase were DEHP and DIBP, together accounting for 84.9% of ∑₆PAEs in the North River, 82.8% of ∑₆PAEs in the West River and 91.6% of ∑₆PAEs in the estuary. DEHP and DINP were the richest congeners in the sediment-phase, with proportions of 84.9% in the North River, 81.0% in the West River and 65.4% in the estuary. The spatial distribution of ∑₆PAEs in water and sediment phases showed that the riverside environment had influence on the distribution pattern. The reconstruction profile of the PAE congeners and the ∑₆PAEs vs the depth of the sediment core indicated that PAEs became increasingly present pollutants around 2006 in the Jiulong River. The results of the potential ecological risk assessment of the RQ method revealed that DIBP and DEHP posed a high risk because of their relatively higher concentrations, while DBP and DINP posed a medium risk to the aquatic system. The baseline data of PAEs in this river will be benefits to the regulatory attention and future strategies of the pollutants control along the river network.

Cognitive deficits and anxiety induced by diisononyl phthalate in mice and the neuroprotective effects of melatonin

Diisononyl phthalate (DINP) is a plasticizer that is frequently used as a substitute for other plasticizers whose use is prohibited in certain products. In vivo studies on the neurotoxicity of DINP are however, limited. This work aims to investigate whether DINP causes neurobehavioral changes in mice and to provide useful advice on preventing the occurrence of these adverse effects. Behavioral analysis showed that oral administration of 20 or 200 mg/kg/day DINP led to mouse cognitive deficits and anxiety. Brain histopathological observations, immunohistochemistry assays (cysteine-aspartic acid protease 3 [caspase-3], glial fibrillary acidic protein [GFAP]), oxidative stress assessments (reactive oxygen species [ROS], glutathione [GSH], superoxide dismutase [SOD] activities, 8-hydroxy-2-deoxyguanosine [8-OH-dG] and DNA-protein crosslinks [DPC]), and assessment of inflammation (tumor necrosis factor alpha [TNF-а] and interleukin-1 beta [IL-1β]) of mouse brains showed that there were histopathological alterations in the brain and increased levels of oxidative stress, and inflammation for these same groups. However, some of these effects were blocked by administration of melatonin (50 mg/kg/day). Down-regulation of oxidative stress was proposed to explain the neuroprotective effects of melatonin. The data suggests that DINP could cause cognitive deficits and anxiety in mice, and that melatonin could be used to avoid these adverse effects.

Serum phthalate levels and time to pregnancy in couples from Greenland, Poland and Ukraine

Phthalates are ubiquitous industrial chemicals that have been associated with altered reproductive function in rodents. Several human studies have reported an inverse association between male testosterone and phthalate levels. Our aim was to investigate time to pregnancy (TTP) according to serum levels of diethylhexyl phthalate (DEHP) and diisononyl phthalate (DiNP) metabolites in both partners. In 2002-2004 we enrolled 938 pregnant women and 401 male spouses from Greenland, Poland and Ukraine. Six oxidized metabolites of DEHP and DiNP were summarized for each of the two parent compounds to provide proxies of the internal exposure. We used Cox discrete-time models to estimate fecundability ratios (FR) and 95% confidence intervals (95% CIs) for men and women according to their proxy-DEHP or -DiNP serum levels adjusted for a fixed set of covariates.

The FR was slightly elevated among women with high levels of DEHP (FR=1.14, 95% CI 1.00;1.30) suggesting a shorter TTP in these women. The FR was unrelated to DiNP in women, whereas the results for men were inconsistent pointing in opposite directions. First-time pregnant women from Greenland with high serum DiNP levels had a longer TTP. This study spanning large contrast in environmental exposure does not indicate adverse effects of phthalates on couple fecundity. The shorter TTP in women with high levels of DEHP metabolites is unexplained and needs further investigation.

The potential use of diisononyl phthalate metabolites hair as biomarkers to assess long-term exposure demonstrated by a rat model

Diisononyl phthalate (DINP) is a widely used industrial plasticizer. People come into contact with this chemical by using plastic products made with it. Human health can be adversely affected by long-term DINP exposure. However, because the body rapidly excretes DINP metabolites, the use of single-point urine analysis to assess long-term exposure may produce inconsistent results in epidemiologic studies. Hair analysis has a useful place in biomonitoring, particularly in estimating long-term or historical exposure for some chemicals. Several studies have reported using hair analysis to assess the concentrations of heavy metals, drugs and organic pollutants in humans. As a biomarker, DINP metabolites were measured in rat hair in animal experiments to evaluated long-term exposure to DINP. In addition, we evaluated the correlation between the levels of DINP metabolites in hair and in urine. The levels of DINP metabolites in rat hair were significantly higher in the exposure group, relative to the control group (p<0.05). DINP metabolites had a positive correlation with increasing administered dose. Significant positive correlations for MINP, MOINP and MHINP were found between hair and urine (r=0.86, r=0.79 and r=0.74, respectively, p<0.05). Several metabolites in urine showed earlier saturation than in hair. In this report, we detected eight metabolites in hair and demonstrate that hair analysis has potential applications in the assessment of long-term exposure to DINP.

Associations between serum phthalates and biomarkers of reproductive function in 589 adult men

Phthalates which are widely used, are ubiquitous in the environment and in some human tissues. It is generally accepted that phthalates exert their toxic action by inhibiting Leydig cell synthesis of testosterone, but in vitro studies have also shown anti-androgenic effects at the receptor level. Some cross-sectional studies have shown inverse associations between urinary levels of phthalates and reproductive hormones, but results are conflicting and the evidence base is limited. The aim of this study was to investigate if levels of di-2-ethylhexyl phthalate (DEHP) and diisononyl phthalate (DiNP) metabolites in serum are associated with serum concentrations of male reproductive hormones and semen quality. A secondary aim was to investigate metabolic pathways of DEHP and DiNP on semen quality and reproductive hormones. A cross-sectional sample of 589 spouses of pregnant women from Greenland, Poland and Ukraine were enrolled between 2002 and 2004. The men gave semen and blood samples and were interviewed. Six phthalate metabolites of DEHP and DiNP were measured by liquid chromatography tandem mass spectrometry in serum. The metabolites were summed according to their molar weight. We observed significant inverse associations between serum levels of the metabolites, the proxies and serum testosterone. Negative associations were also discovered between some metabolites and sex hormone-binding globulin, semen volume and total sperm count. Findings are compatible with a weak anti-androgenic action of DEHP metabolites, but less so for DiNP metabolites. Metabolic pathways differed significantly between the three study sites, but without major effect on semen quality or reproductive hormones.

Associations of phthalate concentrations in floor dust and multi-surface dust with the interior materials in Japanese dwellings

Phthalates are widely used as plasticizers in numerous products. However, there has been some concern about the various effects they may have on human health. Thus, household phthalate levels are an important public health issue. While many studies have assessed phthalate levels in house dust, the association of these levels with building characteristics has scarcely been examined. The present study investigated phthalate levels in house dust samples collected from the living areas of homes, and examined associations between these phthalate levels and the interior materials. Dust was collected from two portions of the living area: floor dust from the entire floor surface, and multi-surface dust from objects more than 35 cm above the floor. The levels of seven phthalates were measured using gas chromatography/mass spectrometry in selective ion monitoring mode. Phthalate levels were higher in multi-surface dust than in floor dust. Among floor dust samples, those from dwellings with compressed wooden flooring had significantly higher levels of di-iso-butyl phthalate compared to those with other floor materials, while polyvinyl chloride (PVC) flooring was associated with higher di-2-ethylhexyl phthalate (DEHP) levels. Among multi-surface dust samples, higher levels of DEHP and di-iso-nonyl phthalate (DINP) were found in samples from homes with PVC wallpaper than without. The number of PVC interior materials was significantly positively correlated with the levels of DEHP and DINP in multi-surface dust. The phthalate levels in multi-surface dust were associated with the interior surface materials, and those in floor dust were directly related to the flooring materials. Our findings show that when using house dust as an exposure assessment, it is very important to note where the samples were collected from. The present report provides useful information about the association between phthalates and dust inside dwellings, which will assist with establishing public health provisions.

Pharmacokinetics of di-isononyl phthalate in freely moving rats by UPLC-MS/MS

Di-isononyl phthalate (DINP) is a general-purpose plasticizer for polyvinyl chloride. However, this industrial chemical plasticizer used as a clouding agent has recently contaminated food and beverages that had been inspected by Taiwan Food and Drug Administration. This study develops a sensitive and specific method combining ultra-performance liquid chromatography with electrospray ionization tandem mass spectrometry (UPLC-MS/MS) to investigate the pharmacokinetics of DINP in freely moving rats. Multiple reaction monitoring (MRM) was used to monitor the transition of the protonated molecule m/z of 419 [M+H](+) to the product ion 149 for DINP. The analyte was analyzed by UPLC-MS/MS with C18 column (100×2.1mm, 1.7 μm) which was equilibrated and eluted with an isocratic mixture of acetonitrile-ammonium acetate water solution (90:10, v/v) at a flow rate of 0.3 mL/min. Linear calibration curves were obtained for DINP concentration ranges of 0.05-2.5 μg/mL in plasma and feces. The feces were homogenized mechanically using 50% acetonitrile as the medium. The pharmacokinetic curve demonstrates that the disposition of DINP in rat plasma was fitted well by the two-compartment model after DINP administration (10 mg/kg, i.v.). The elimination half-life of DINP was 364±146 min and 150±58 min for intravenous (10 mg/kg) and oral (100 mg/kg) administration, respectively. The pharmacokinetic data indicate that the oral bioavailability of DINP in freely moving rats was about 1.19%. The total DINP excretion up to 48 h was 13.64±3.99% in feces.

Phthalate levels in nursery schools and related factors

Phthalate esters, which are known endocrine disruptors, are ubiquitously present throughout indoor environments. Leaching from building materials may be a major source of phthalate esters. In this study, we evaluated phthalate ester concentrations in dust samples from 64 classrooms located in 50 nursery schools and explored the critical factors affecting phthalate concentrations, especially with regard to building materials. Dust was sampled by a modified vacuuming method, and building materials were assessed using a portable X-ray fluorescence (XRF) analyzer to determine whether they contained polyvinyl chloride. Di-n-butyl phthalate (DBP), di(2-ethylhexyl) phthalate (DEHP), and di-isononyl phthalate (DINP) were the most frequently detected phthalates. Of these, DEHP was the most abundant phthalate, with a geometric mean of 3170 μg/g dust, and concentrations were significantly correlated with the area of polyvinyl chloride (PVC)-verified flooring. DINP, which has not been well-reported in other studies, was the second-most abundant phthalate, with a geometric mean of 688 μg/g dust, and showed a critical relationship with the number of children in the institution and the agency operating the nursery school. This is the first study to verify the sources of phthalates with an XRF analyzer and to evaluate the relationship between phthalate concentrations and PVC-verified materials.

Hydrolysis of di-n-butyl phthalate, butylbenzyl phthalate and di(2-ethylhexyl) phthalate in human liver microsomes

Diester phthalates are industrial chemicals used primarily as plasticizers to import flexibility to polyvinylchloride plastics. In this study, we examined the hydrolysis of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) in human liver microsomes. These diester phthalates were hydrolyzed to monoester phthalates (mono-n-butyl phthalate (MBP) from DBP, mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP) from BBzP, and mono(2-ethylhexyl) phthalate (MEHP)) by human liver microsomes. DBP, BBzP and DEHP hydrolysis showed sigmoidal kinetics in V-[S] plots, and the Hill coefficient (n) ranged 1.37-1.96. The S(50), V(max) and CL(max) values for DBP hydrolysis to MBP were 99.7 μM, 17.2nmolmin(-1)mg(-1) protein and 85.6 μL min(-1)mg(-1) protein, respectively. In BBzP hydrolysis, the values of S(50) (71.7 μM), V(max) (13.0nmolmin(-1)mg(-1) protein) and CL(max) (91.3 μL min(-1)mg(-1) protein) for MBzP formation were comparable to those of DBP hydrolysis. Although the S(50) value for MBP formation was comparable to that of MBzP formation, the V(max) and CL(max) values were markedly lower (<3%) than those for MBzP formation. The S(50), V(max) and CL(max) values for DEHP hydrolysis were 8.40 μM, 0.43 nmol min(-1)mg(-1) protein and 27.5 μL min(-1)mg(-1) protein, respectively. The S(50) value was about 10% of DBP and BBzP hydrolysis, and the V(max) value was also markedly lower (<3%) than those for DBP hydrolysis and MBzP formation for BBzP hydrolysis. The ranking order of CL(max) values for monoester phthalate formation in DBP, BBzP and DEHP hydrolysis was BBzP to MBzP≥DBP to MBP>DEHP to MEHP>BBzP to MBP. These findings suggest that the hydrolysis activities of diester phthalates by human liver microsomes depend on the chemical structure, and that the metabolism profile may relate to diester phthalate toxicities, such as hormone disruption and reproductive effects.

The G protein-coupled cannabinoid-1 (CB1) receptor of mammalian brain: inhibition by phthalate esters in vitro

This research examines the in vitro interaction of phthalate diesters and monoesters with the G protein-coupled cannabinoid 1 (CB(1)) receptor, a presynaptic complex involved in the regulation of synaptic activity in mammalian brain. The diesters, n-butylbenzylphthalate (nBBP), di-n-hexylphthalate (DnHP), di-n-butylphthalate (DnBP), di-2-ethylhexylphthalate (DEHP), di-isooctylphthalate (DiOP) and di-n-octylphthalate (DnOP) inhibited the specific binding of the CB(1) receptor agonist [(3)H]CP-55940 to mouse whole brain membranes at micromolar concentrations (IC(50)s: nBBP 27.4 μM; DnHP 33.9 μM; DnBP 45.9 μM; DEHP 47.4 μM; DiOP 55.4 μM; DnOP 75.2 μM). DnHP, DnBP and nBBP achieved full (or close to full) blockade of [(3)H]CP-55940 binding, whereas DEHP, DiOP and DnOP produced partial (55-70%) inhibition. Binding experiments with phenylmethane-sulfonylfluoride (PMSF) indicated that the ester linkages of nBBP and DnBP remain intact during assay. The monoesters mono-2-ethylhexylphthalate (M2EHP) and mono-isohexylphthalate (MiHP) failed to reach IC(50) at 150 μM and mono-n-butylphthalate (MnBP) was inactive. Inhibitory potencies in the [(3)H]CP-55940 binding assay were positively correlated with inhibition of CB(1) receptor agonist-stimulated binding of [(35)S]GTPγS to the G protein, demonstrating that phthalates cause functional impairment of this complex. DnBP, nBBP and DEHP also inhibited binding of [(3)H]SR141716A, whereas inhibition with MiHP was comparatively weak and MnBP had no effect. Equilibrium binding experiments with [(3)H]SR141716A showed that phthalates reduce the B(max) of radioligand without changing its K(d). DnBP and nBBP also rapidly enhanced the dissociation of [(3)H]SR141716A. Our data are consistent with an allosteric mechanism for inhibition, with phthalates acting as relatively low affinity antagonists of CB(1) receptors and cannabinoid agonist-dependent activation of the G-protein. Further studies are warranted, since some phthalate esters may have potential to modify CB(1) receptor-dependent behavioral and physiological outcomes in the whole animal.

Occupational exposure to diisononyl phthalate (DiNP) in polyvinyl chloride processing operations

PURPOSE

Diisononyl phthalate (DiNP) is primarily used as a plasticizer in polyvinyl chloride (PVC) materials. While information is available on general population exposure to DiNP, occupational exposure data are lacking. We present DiNP metabolite urinary concentrations in PVC processing workers, estimate DiNP daily intake for these workers, and compare worker estimates to other populations.

METHODS

We assessed DiNP exposure in participants from two companies that manufactured PVC materials, a PVC film manufacturer (n = 25) and a PVC custom compounder (n = 12). A mid-shift and end-shift urine sample was collected from each participant and analyzed for the DiNP metabolite mono(carboxy-isooctyl) phthalate (MCiOP). Mixed models were used to assess the effect on MCiOP concentrations of a worker being assigned to (1) a task using DiNP and (2) a shift where DiNP was used. A simple pharmacokinetic model was used to estimate DiNP daily intake from the MCiOP concentrations.

RESULTS

Creatinine-adjusted MCiOP urinary concentrations ranged from 0.42-80 μg/g in PVC film and from 1.11-13.4 μg/g in PVC compounding. PVC film participants who worked on a task using DiNP (n = 7) had the highest MCiOP geometric mean (GM) end-shift concentration (25.2 μg/g), followed by participants who worked on a shift where DiNP was used (n = 11) (17.7 μg/g) as compared to participants with no task (2.92 μg/g) or shift (2.08 μg/g) exposure to DiNP. The GM end-shift MCiOP concentration in PVC compounding participants (4.80 μg/g) was comparable to PVC film participants with no task or shift exposure to DiNP. Because no PVC compounding participants were assigned to tasks using DINP on the day sampled, DiNP exposure in this company may be underestimated. The highest DiNP intake estimate was 26 μg/kg/day.

CONCLUSION

Occupational exposure to DiNP associated with PVC film manufacturing tasks were substantially higher (sixfold to tenfold) than adult general population exposures; however, all daily intake estimates were less than 25% of current United States or European acceptable or tolerable daily intake estimates. Further characterization of DiNP occupational exposures in other industries is recommended.

Phthalates in toys available in Indian market

Twenty four children's toys and child care articles available in the local market of India were analyzed for eight phthalates as children toys are plasticized with phthalates. All toy samples showed the presence of one or more phthalates including di-(2-ethylhexyl) phthalate (96% of the samples), di-iso-nonyl phthalate and di-iso-decyl phthalate (42% of the samples) at a concentration ranging from 0.1% to 16.2%. Soft toys contain higher levels of phthalates as compared to hard toys as primary function of phthalates is softening of hard plastic materiel.

Assessing exposure to phthalates - the human biomonitoring approach

Some phthalates are developmental and reproductive toxicants in animals. Exposure to phthalates is considered to be potentially harmful to human health as well. Based on a comprehensive literature research, we present an overview of the sources of human phthalate exposure and results of exposure assessments with special focus on human biomonitoring data. Among the general population, there is widespread exposure to a number of phthalates. Foodstuff is the major source of phthalate exposure, particularly for the long-chain phthalates such as di(2-ethylhexyl) phthalate. For short-chain phthalates such as di-n-butyl-phthalate, additional pathways are of relevance. In general, children are exposed to higher phthalate doses than adults. Especially, high exposures can occur through some medications or medical devices. By comparing exposure data with existing limit values, one can also assess the risks associated with exposure to phthalates. Within the general population, some individuals exceed tolerable daily intake values for one or more phthalates. In high exposure groups, (intensive medical care, medications) tolerable daily intake transgressions can be substantial. Recent findings from animal studies suggest that a cumulative risk assessment for phthalates is warranted, and a cumulative exposure assessment to phthalates via human biomonitoring is a major step into this direction.

Selecting adequate exposure biomarkers of diisononyl and diisodecyl phthalates: data from the 2005-2006 National Health and Nutrition Examination Survey

BACKGROUND

High-molecular-weight phthalates, such as diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP), are used primarily as polyvinyl chloride plasticizers.

OBJECTIVES

We assessed exposure to DINP and DIDP in a representative sample of persons ≥ 6 years of age in the U.S. general population from the 2005-2006 National Health and Nutrition Examination Survey (NHANES).

METHODS

We analyzed 2,548 urine samples by using online solid-phase extraction coupled to isotope dilution high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

We detected monocarboxyisooctyl phthalate (MCOP), a metabolite of DINP, and monocarboxyisononyl phthalate (MCNP), a metabolite of DIDP, in 95.2% and 89.9% of the samples, respectively. We detected monoisononyl phthalate (MNP), a minor metabolite of DINP, much less frequently (12.9%) and at concentration ranges (> 0.8 µg/L-148.1 µg/L) much lower than MCOP (> 0.7 µg/L- 4,961 µg/L). Adjusted geometric mean concentrations of MCOP and MCNP were significantly higher (p < 0.01) among children than among adolescents and adults.

CONCLUSIONS

The general U.S. population, including children, was exposed to DINP and DIDP. In previous NHANES cycles, the occurrence of human exposure to DINP by using MNP as the sole urinary biomarker has been underestimated, thus illustrating the importance of selecting the most adequate biomarkers for exposure assessment.

Plastics and health risks

By 2010, the worldwide annual production of plastics will surpass 300 million tons. Plastics are indispensable materials in modern society, and many products manufactured from plastics are a boon to public health (e.g., disposable syringes, intravenous bags). However, plastics also pose health risks. Of principal concern are endocrine-disrupting properties, as triggered for example by bisphenol A and di-(2-ethylhexyl) phthalate (DEHP). Opinions on the safety of plastics vary widely, and despite more than five decades of research, scientific consensus on product safety is still elusive. This literature review summarizes information from more than 120 peer-reviewed publications on health effects of plastics and plasticizers in lab animals and humans. It examines problematic exposures of susceptible populations and also briefly summarizes adverse environmental impacts from plastic pollution. Ongoing efforts to steer human society toward resource conservation and sustainable consumption are discussed, including the concept of the 5 Rs--i.e., reduce, reuse, recycle, rethink, restrain--for minimizing pre- and postnatal exposures to potentially harmful components of plastics.

Effects of diisononyl phthalate on atopic dermatitis in vivo and immunologic responses in vitro

BACKGROUND

Diisononyl phthalate (DINP), a principal plasticizer in many polyvinyl chloride products, has been shown to have an adjuvant effect on immunoglobulin (Ig) production in mice. However, the effects of DINP on allergic diseases have not been fully elucidated.

OBJECTIVES

In the present study we investigated the effects of DINP on atopic dermatitis (AD)-like skin lesions induced by Dermatophagoides pteronyssinus (Dp) in atopic-prone NC/Nga mice.

METHODS

Mice were injected intradermally with Dp on their ears and were exposed to DINP (0, 0.15, 1.5, 15, or 150 mg/kg/day) intraperitoneally. We evaluated clinical scores, ear thickening, histologic findings, protein expression of cytokines/chemokines in the ear, and serum levels of Ig and histamine. Furthermore, we investigated the effects of DINP on bone-marrow-derived dendritic cells (BMDCs) or splenocytes in vitro. After exposure to DINP (0-100 microM), cells were evaluated for phenotype and function.

RESULTS

DINP aggravated AD-like skin lesions related to Dp. The aggravation was consistent with eosinophilic inflammation, mast cell degranulation, and thymic stromal lymphopoietin (TSLP) expression in the ear. DINP enhanced the expression of cell surface activation markers on BMDCs and their production of TARC/CCL17 (thymus- and activation-regulated chemokine) and MDC/CCL22 (macrophage-derived chemokine), as well as their capacity to stimulate Dp-specific T-cell proliferation. DINP also enhanced interleukin-4 production and Dp-stimulated proliferation of splenocytes.

CONCLUSIONS

DINP can aggravate AD-like skin lesions related to Dp. The mechanisms of the aggravation might be mediated, at least partly, through the TSLP-related activation of dendritic cells and by direct or indirect activation of the immune cells.

Phthalate risks, phthalate regulation, and public health: a review

As a result of concerns about the toxicity of phthalates to humans, several expert panels were convened toward the end of the 1990s to evaluate the implications of the scientific evidence for the risks of phthalates to humans of all ages. These panels concluded that the risks were low although they had concerns about specific applications of some phthalates, e.g., in medical devices. These groups identified data gaps and recommended additional studies on exposure and toxicity be conducted. In light of the additional data, reevaluations of the risks of phthalates were conducted. While these assessments were being undertaken, U.S. state governments and European authorities proposed and promulgated regulations to limit the use of certain phthalates, i.e., di-n-octyl phthalate (DnOP), di-isodecyl phthalate (DIDP), di-isononyl phthalate (DINP), butylbenzyl phthalate (BBP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP), especially in consumer products to which children are exposed. Very recently, similar regulations were promulgated in the United States under the Consumer Product Safety Improvement Act of 2008. This article summarizes recent evaluations of the risks of these phthalates, and addresses the public health implications of the regulations that were enacted. The analysis considers biomonitoring studies and epidemiological research in addition to laboratory animal evidence. Analysis of all of the available data leads to the conclusion that the risks are low, even lower than originally thought, and that there is no convincing evidence of adverse effects on humans. Since the scientific evidence strongly suggests that risks to humans are low, phthalate regulations that have been enacted are unlikely to lead to any marked improvement in public health.

Biodegradation of a phthalate plasticizer, di-isononyl phthalate (DINP), by Sphingobium chungbukense

In this study, di-isononyl phthalate (DINP) was efficiently degraded by Sphingobium chungbukense KCTC 2955. The optimal conditions for DINP (100 mg L(-1)) degradation by S. chungbukense in a mineral salts medium were found to be pH 7.0, 30 degrees C, and stirring at 200 rpm. The maximum specific rate of DINP degradation was found to be concentration dependent, with a maximum of 4.12 mg DINP L(-1) h(-1). DINP was transformed rapidly by S. chungbukense, with the formation of monoisononyl phthalate (MIP) and phthalic acid, which subsequently degraded further. These results highlight the potential of this bacterium for removing DINP-contaminated waste in the environment.

Chronic toxicity of diethyl phthalate-A three generation lactational and gestational exposure study on male Wistar rats

Diethyl phthalate (DEP) is widely used in the perfume industry as a vehicle for fragrances and in personal care products making human exposure of DEP significant to adults as well as neonatals, as confirmed by levels recorded in blood as well as breast milk samples of human populations in some parts of the world. Therefore, a study was undertaken to understand the toxic effect of DEP over three generations in male Wistar rats. Healthy male and female albino rats of Wistar strain weighing 75-100g (6-7 weeks old) were randomly assigned to two groups of six each. Group I (Control) male and female rats were fed on normal diet and water ad libitum. Group II (DEP) male and female rats were given DEP dissolved in corn oil mixed with the diet at 50mg/kg of the diet/day. Hundred days after the treatment, females were mated with males for 10 days. Exposure to DEP was continued throughout mating, gestation until termination at weaning, which was 150 days of total treatment period of the parental generation. The F1 and F2 generation pups were then segregated on the basis of their sex and six male and female pups of both generations were allowed to grow till they were 75-100g in weight. The treatment was then carried out similar to the parental generation but with reduced dose of 25mg/kg of the diet/day for F1 generation and 10mg/kg of the diet/day for F2 generation. Hundred days after the treatment, females were mated with males for 10 days. Exposure to DEP was continued throughout mating, gestation (21 days) until termination at weaning (21 days), which was 150 days of total treatment period of the F1 and F2 generation. Liver and serum ALT, AST and triglycerides were significantly increased over the three generations, which was much more significant in the F2 generation DEP treated group. The serum cholesterol and liver glutathione and glutathione reductase showed a significant decrease over the three generations, which was much more significant in the F2 generation DEP treated group as compared to the parental and F1 generation DEP treated rats. Histology of the liver showed remarkably enhanced fatty degeneration in the F2 generation DEP treated rats as compared to parental and F1 generation DEP treated rats. Vacuolations were much more significant in the F1 generation DEP treated rats as compared to the controls and F2 generation DEP treated rats. It can be concluded from this study, that continuous exposure through food, gestation and lactation over three generation's inspite of dose reduction of DEP leads to an enhanced toxic effect in the latter generations.

Determination of secondary, oxidised di-iso-nonylphthalate (DINP) metabolites in human urine representative for the exposure to commercial DINP plasticizers

Di-iso-nonylphthalate (DINP) is the major plasticizer for polyvinylchloride (PVC) polymers. Two DINP products are currently produced: DINP 1 and DINP 2. We analyzed the isononyl alcohol mixtures (INA) used for the synthesis of these two DINP plasticizer products and thus identified 4-methyloctanol-1 as one of the major constituents of the alkyl side chains of DINP 1 (8.7%) and DINP 2 (20.7%). Based on this isomer, we postulated the major DINP metabolites renally excreted by humans: mono-(4-methyl-7-hydroxy-octyl)phthalate (7OH-MMeOP), mono-(4-methyl-7-oxo-octyl)phthalate (7oxo-MMeOP) and mono-(4-methyl-7-carboxy-heptyl)phthalate (7carboxy-MMeHP). We present a fast and reliable on-line clean-up HPLC method for the simultaneous determination of these three DINP metabolites in human urine. We used ESI-tandem mass spectrometry for detection and isotope dilution for quantification (limit of quantification 0.5microg/l). Via these three oxidised DINP isomer standards, we quantified the excretion of all oxidised DINP isomers with hydroxy (OH-MINP), oxo (oxo-MINP) and carboxy (carboxy-MINP) functional groups. With this approach, we can for the first time reliably quantify the internal burden of the general population to DINP. Mean urinary metabolite concentrations in random samples from the general German population (n=25) were 14.9microg/l OH-MINP, 8.9microg/l oxo-MINP and 16.4microg/l carboxy-MINP. Metabolites strongly correlated with each other over all samples analyzed (R>0.99, p<0.0001).

Di-iso-nonylphthalate (DINP) metabolites in human urine after a single oral dose of deuterium-labelled DINP

Di-iso-nonylphthalate (DINP), a complex mixture of predominantly nine-carbon branched chain dialkyl phthalate isomers, has replaced di-(2-ethylhexyl)phthalate (DEHP) as the major plasticiser for polyvinylchloride (PVC) polymers. Similar to DEHP, DINP is a developmental and reproductive toxicant in rodents. This study for the first time describes human metabolism and elimination of DINP in a male volunteer after we applied a single oral DINP dose of 1.27 mg/kg body-weight. To avoid interference by omnipresent background exposure we used deuterium-labelled DINP. We investigated the urinary excretion of the simple monoester mono-iso-nonylphthalate (MINP) and oxidised isomers with hydroxy (OH-MINP), oxo (oxo-MINP) and carboxy (carboxy-MINP) functional groups. We used isomeric MINP and three specific oxidised isomer standards for quantification: mono-(4-methyl-7-hydroxy-octyl)phthalate (7OH-MMeOP), mono-(4-methyl-7-oxo-octyl)phthalate (7oxo-MMeOP) and mono-(4-methyl-7-carboxyheptyl)phthalate (7carboxy-MMeHP). These specific DINP metabolites are currently the only synthetic DINP metabolite standards available. Within 48 h we recovered 43.6% of the applied dose in urine as the above DINP metabolites, 20.2% as OH-MINP, 10.7% as carboxy-MINP, 10.6% as oxo-MINP and only 2.2% as MINP. Other oxidised DINP metabolites not determined in this study probably increase the share of the DINP dose excreted via urine. Elimination followed a multi-phase pattern, elimination half-lives in the second phase (beginning 24h post-dose) can only roughly be estimated to be 12h for the OH- and oxo-MINP-metabolites and 18 h for carboxy-MINP metabolites. After 24h, the carboxy-MINP metabolites replaced the OH-MINP metabolites as the major urinary metabolites. All oxidised DINP metabolites are suitable parameters for biomonitoring human DINP exposure.

Oxidative metabolites of diisononyl phthalate as biomarkers for human exposure assessment

Diisononyl phthalate (DINP) is a complex mixture of predominantly nine-carbon branched-chain dialkyl phthalate isomers. Similar to di(2-ethylhexyl) phthalate, a widely used phthalate, DINP causes antiandrogenic effects on developing rodent male fetuses. Traditionally, assessment of human exposure to DINP has been done using monoisononyl phthalate (MINP) , the hydrolytic metabolite of DINP, as a biomarker. However, MINP is only a minor urinary metabolite of DINP. Oxidative metabolites, including mono(carboxyisooctyl) phthalate (MCIOP) , mono(oxoisononyl) phthalate (MOINP) , and mono(hydroxyisononyl) phthalate (MHINP) are the major urinary metabolites in DINP-dosed rats. The urinary concentrations of MINP, MCIOP, MOINP, and MHINP were measured in 129 adult anonymous human volunteers with no known exposure to DINP. Although MINP was not present at detectable levels in any of the samples analyzed, MCIOP, MHINP, and MOINP were detected in 97, 100, and 87% of the urine samples at geometric mean levels equal to 8.6, 11.4, and 1.2 ng/mL, respectively. The concentrations of all three oxidative metabolites were highly correlated with each other (p<0.0001), which confirms a common precursor. MCIOP was excreted predominantly as a free species, whereas MOINP was excreted mostly in its glucuronidated form. The percentage of MHINP excreted either glucuronidated or in its free form was similar. The significantly higher frequency of detection and urinary concentrations of oxidative metabolites than of MINP suggest that these oxidative metabolites are better biomarkers of exposure assessment of DINP than is MINP. Therefore, we concluded that the prevalence of human exposure to DINP is underestimated by using MINP as the sole DINP urinary biomarker.

Chronic toxicity of diethyl phthalate in male Wistar rats—A dose–response study

Diethyl phthalate (DEP) is widely used in personal care products, plastics and medical devices at various concentrations, but its information is limited on its toxicity associated with exposure at high as well as low doses for a prolonged period. Therefore, a study was undertaken to understand the dose-response toxic effect of DEP in male Wistar rats. Control rats were fed on normal diet and water ad libitum. Rats were given DEP dissolved individually in corn oil mixed with the diet at 10, 25 and 50 mg/kg of the diet/day, which is equal to 0.57, 1.425 and 2.85 mg/kg body wt/day. After 5 months of treatment animals were sacrificed, enzymes and other biochemical parameters in the serum and liver were assessed. Liver weight to body weight ratio showed a significant increase only in 10 ppm DEP treated rats. A significant increase was observed in the serum ACP, LDH, ALT enzyme levels of 10 mg/kg treated rats as compared to control, 25 and 50 mg/kg treated rats. Other biochemical parameters like glycogen, total cholesterol, total triglycerides and lipid peroxidation were also increased in the liver of all the three treated groups. In the 10 and 50 mg/kg diet/day treated rats, there was a significant decrease in liver total GSH as compared to controls and 25 mg/kg treated rats. Histology of liver showed severe vacuolations, fatty degeneration and loss of hepatic architecture in the 10mg/kg treated rats, whereas in the 25 and 50 mg/kg treated rats only loss of hepatic architecture and granular deposits in the hepatocytes was predominant. Histology of liver by electron micrographs showed a significant dose-dependent proliferation of mitochondria in the hepatocytes, while the 10mg/kg treated rats showed increased number of peroxisomes in the hepatocytes. It is evident from this study that treatment with higher concentrations of DEP results in mitochondrial proliferation as well as accumulation of glycogen, cholesterol and triglycerides within the liver, but exposure to lower concentrations for longer periods results in increase in peroxisome numbers leading to severe hepatocellular changes which can be confirmed by significantly increased liver weights, elevated enzyme levels in the serum and liver and impaired metabolism of glycogen, cholesterol and triglyceride as well as altered liver histology.

What are the sources of exposure to eight frequently used phthalic acid esters in Europeans?

Phthalic acid esters (phthalates) are used as plasticizers in numerous consumer products, commodities, and building materials. Consequently, phthalates are found in human residential and occupational environments in high concentrations, both in air and in dust. Phthalates are also ubiquitous food and environmental contaminants. An increasing number of studies sampling human urine reveal the ubiquitous phthalate exposure of consumers in industrialized countries. At the same time, recent toxicological studies have demonstrated the potential of the most important phthalates to disturb the human hormonal system and human sexual development and reproduction. Additionally, phthalates are suspected to trigger asthma and dermal diseases in children. To find the important sources of phthalates in Europeans, a scenario-based approach is applied here. Scenarios representing realistic exposure situations are generated to calculate the age-specific range in daily consumer exposure to eight phthalates. The scenarios demonstrate that exposure of infant and adult consumers is caused by different sources in many cases. Infant consumers experience significantly higher daily exposure to phthalates in relation to their body weight than older consumers. The use of consumer products and different indoor sources dominate the exposure to dimethyl, diethyl, benzylbutyl, diisononyl, and diisodecyl phthalates, whereas food has a major influence on the exposure to diisobutyl, dibutyl, and di-2-ethylhexyl phthalates. The scenario-based approach chosen in the present study provides a link between the knowledge on emission sources of phthalates and the concentrations of phthalate metabolites found in human urine.

Urinary biomarkers of di-isononyl phthalate in rats

Commercial di-isononyl phthalate (DiNP) is a mixture of various branched-chain dialkyl phthalates mainly containing nine-carbon alkyl isomers. At high doses in rodents, DiNP is a carcinogen, and a developmental toxicant. After exposure, the diester isomers are de-esterified to form hydrolytic monoesters, monoisononyl phthalates (MiNP), which subsequently metabolize to form oxidative metabolites. These metabolites can be excreted in urine or feces. The urinary excretion of DiNP metabolites was monitored in adult female Sprague-Dawley rats after oral administration of a single dose (300 mg/kg) of commercial DiNP. The metabolites were extracted from urine, resolved with high performance liquid chromatography, analyzed by mass spectrometry, and tentatively identified based on their chromatographic separation and mass spectrometric fragmentation pattern. Because DiNP is an isomeric mixture, its metabolites were also isomeric mixtures that eluted from the HPLC column with close retention times. Mono(carboxy-isooctyl)phthalate (MCiOP) was identified as the major metabolite of DiNP; in addition, mono(hydroxy-isononyl)phthalate (MHiNP) and mono(oxo-isononyl)phthalate (MOiNP) were present. Furthermore, metabolites of di-isooctyl phthalate (DiOP) and di-isodecyl phthalate (DiDP) were also detected. Excretion toxicokinetics of the DiNP metabolites in urine followed a biphasic pattern with initial rapid decay in concentration. Despite potential differences in the metabolism of DiNP among species, MCiOP, MHiNP and MOiNP were detected in humans with no known exposure to DiNP at levels significantly higher than MiNP suggesting that these oxidative metabolites may be better urinary biomarkers of human exposure to DiNP than is MiNP.

An assessment of the potential developmental and reproductive toxicity of di-isoheptyl phthalate in rodents

Di-isoheptyl phthalate (DIHP) is a branched, phthalate ester with seven carbon alkyl side chains. Since structurally similar phthalates have been shown to produce developmental and/or reproductive effects in rodents, the potential for DIHP to produce developmental and reproductive toxicity was assessed. In a developmental toxicity study, female rats were given DIHP by oral gavage on gestational days 6-20. There were significant reductions in uterine weight, increased resorptions and reduced fetal weight in the high dose (750 mg/kg) group. Fetal examination revealed malformations and variations of both the skeletal system and the viscera including ectopic testes. The intermediate dose, 300 mg/(kg/day), was a no effect level in this study. In a two-generation reproductive toxicity study, DIHP was given in the diet at 1000, 4500 and 8000 ppm. In the 8000 ppm group of the first (F1) generation, anogenital distance was reduced, time to balanopreputial separation was increased, there was a significant increase in thoracic nipples and testicular abnormalities, and weights of testes and accessory reproductive organs were significantly reduced. Testicular sperm counts and daily sperm production were significantly reduced. Fertility was also significantly reduced in the 8000 ppm group. In the second (F2) generation offspring, anogenital distance was significantly reduced and there was evidence of reduced weight gain during lactation in both the 4500 and 8000 ppm groups. The overall no effect level (NOEL) in the reproductive toxicity study was in the range of 64-168 mg/(kg/day) (gestation-lactation periods). By comparison, estimated average human exposures in the general population are <1 microg/(kg/day).

Human exposure to phthalates via consumer products

Phthalate exposures in the general population and in subpopulations are ubiquitous and widely variable. Many consumer products contain specific members of this family of chemicals, including building materials, household furnishings, clothing, cosmetics, pharmaceuticals, nutritional supplements, medical devices, dentures, children's toys, glow sticks, modelling clay, food packaging, automobiles, lubricants, waxes, cleaning materials and insecticides. Consumer products containing phthalates can result in human exposures through direct contact and use, indirectly through leaching into other products, or general environmental contamination. Historically, the diet has been considered the major source of phthalate exposure in the general population, but all sources, pathways, and their relative contributions to human exposures are not well understood. Medical devices containing di-(2-ethylhexyl) phthalate are a source of significant exposure in a susceptible subpopulation of individuals. Cosmetics, personal care products, pharmaceuticals, nutritional supplements, herbal remedies and insecticides, may result in significant but poorly quantified human exposures to dibutyl phthalate, diethyl phthalate, or dimethyl phthalate. Oven baking of polymer clays may cause short-term, high-level inhalation exposures to higher molecular weight phthalates.

Human breast milk contamination with phthalates and alterations of endogenous reproductive hormones in infants three months of age

Phthalates adversely affect the male reproductive system in animals. We investigated whether phthalate monoester contamination of human breast milk had any influence on the postnatal surge of reproductive hormones in newborn boys as a sign of testicular dysgenesis.

DESIGN

We obtained biologic samples from a prospective Danish-Finnish cohort study on cryptorchidism from 1997 to 2001. We analyzed individual breast milk samples collected as additive aliquots 1-3 months postnatally (n = 130; 62 cryptorchid/68 healthy boys) for phthalate monoesters [mono-methyl phthalate (mMP), mono-ethyl phthalate (mEP), mono-n-butyl phthalate (mBP), mono-benzyl phthalate (mBzP), mono-2-ethylhexyl phthalate (mEHP), mono-isononyl phthalate (miNP)]. We analyzed serum samples (obtained in 74% of all boys) for gonadotropins, sex-hormone binding globulin (SHBG), testosterone, and inhibin B.

RESULTS

All phthalate monoesters were found in breast milk with large variations [medians (minimum-maximum)]: mMP 0.10 (< 0.01-5.53 microg/L), mEP 0.95 (0.07-41.4 microg/L), mBP 9.6 (0.6-10,900 microg/L), mBzP 1.2 (0.2-26 microg/L), mEHP 11 (1.5-1,410 microg/L), miNP 95 (27-469 microg/L). Finnish breast milk had higher concentrations of mBP, mBzP, mEHP, and Danish breast milk had higher values for miNP (p = 0.0001-0.056). No association was found between phthalate monoester levels and cryptorchidism. However, mEP and mBP showed positive correlations with SHBG (r = 0.323, p = 0.002 and r = 0.272, p = 0.01, respectively); mMP, mEP, and mBP with LH:free testosterone ratio (r = 0.21-0.323, p = 0.002-0.044) and miNP with luteinizing hormone (r = 0.243, p = 0.019). mBP was negatively correlated with free testosterone (r = -0.22, p = 0.033). Other phthalate monoesters showed similar but nonsignificant tendencies.

CONCLUSIONS

Our data on reproductive hormone profiles and phthalate exposures in newborn boys are in accordance with rodent data and suggest that human Leydig cell development and function may also be vulnerable to perinatal exposure to some phthalates. Our findings are also in line with other recent human data showing incomplete virilization in infant boys exposed to phthalates prenatally.

Disruption of reproductive development in male rat offspring following in utero exposure to phthalate esters

Certain Phthalate esters have been shown to produce reproductive toxicity in male rodents with an age dependent sensitivity in effects with foetal animals being more sensitive than neonates which are in turn more sensitive than pubertal and adult animals. While the testicular effects of phthalates in rats have been known for more than 30 years, recent attention has been focused on the ability of these agents to produce effects on reproductive development in male offspring after in utero exposure. These esters and in particular di-butyl, di-(2-ethylhexyl) and butyl benzyl phthalates have been shown to produce a syndrome of reproductive abnormalities characterized by malformations of the epididymis, vas deferens, seminal vesicles, prostate, external genitalia (hypospadias), cryptorchidism and testicular injury together with permanent changes (feminization) in the retention of nipples/areolae (sexually dimorphic structures in rodents) and demasculinization of the growth of the perineum resulting in a reduced anogenital distance (AGD). Critical to the induction of these effects is a marked reduction in foetal testicular testosterone production at the critical window for the development of the reproductive tract normally under androgen control. A second Leydig cell product, insl3, is also significantly down regulated and is likely responsible for the cryptorchidism commonly seen in these phthalate-treated animals. The testosterone decrease is mediated by changes in gene expression of a number of enzymes and transport proteins involved in normal testosterone biosynthesis and transport in the foetal Leydig cell. Alterations in the foetal seminiferous cords are also noted after in utero phthalate treatment with the induction of multinucleate gonocytes that contribute to lowered spermatocyte numbers in postnatal animals. The phthalate syndrome of effects on reproductive development has parallels with the reported human testicular dysgenesis syndrome, although no cause and effect relationship exists after exposure of humans to phthalate esters. However humans are exposed to and produce the critical phthalate metabolites that have been detected in blood of the general population, in children and also human amniotic fluid.

Risk assessment of oral exposure to diisononyl phthalate from children's products

Dialkyl phthalates are plasticizers used in household products made from polyvinyl chloride (PVC). Diisononyl phthalate (DINP) is the principal phthalate in soft plastic toys. Because DINP is not tightly bound to PVC, it may be released when children mouth PVC products. The potential chronic health risks of phthalate exposure to infants have been under scrutiny by regulatory agencies in Europe, Canada, Japan, and the U.S. This report describes a risk assessment of DINP exposure from children's products, by the U.S. Consumer Product Safety Commission (CPSC) staff. This report includes the findings of a CPSC Chronic Hazard Advisory Panel (CHAP) which: (1) concluded that DINP is unlikely to present a human cancer hazard and (2) recommended an acceptable daily intake (ADI) level of 120 microg/kg-d, based on spongiosis hepatis in rats. The risk assessment incorporates new measurements of DINP migration rates from 24 toys and a new observational study of children's mouthing activities, with a detailed characterization of the objects mouthed. Probabilistic methods were used to estimate exposure. Mouthing behavior and, thus, exposure depend on the child's age. Approximately 42% of tested soft plastic toys contained DINP. Estimated DINP exposures for soft plastic toys were greatest among children 12-23 months old. The mean exposure for this age group was 0.08 (95% confidence interval 0.04-0.14) microg/kg-d, with a 99th percentile of 2.4 (1.3-3.2) microg/kg-d. The authors conclude that oral exposure to DINP from mouthing soft plastic toys is not likely to present a health hazard to children. The opinions expressed by the authors have not been reviewed or approved by, and do not necessarily reflect the views of, the U.S. Consumer Product Safety Commission. Because this material was prepared by the authors in their official capacity, it is in the public domain and may be freely copied or reprinted.

Differential Effects of Phthalates on the Testis and the Liver1

Phthalates have been shown to elicit contrasting effects on the testis and the liver, causing testicular degeneration and promoting abnormal hepatocyte proliferation and carcinogenesis. In the present study, we compared the effects of phthalates on testicular and liver cells to better understand the mechanisms by which phthalates cause testicular degeneration. In vivo treatment of rats with di-(2-ethylhexyl) phthalate (DEHP) caused a threefold increase of germ cell apoptosis in the testis, whereas apoptosis was not changed significantly in livers from the same animals. Western blot analyses revealed that peroxisome proliferator-activated receptor (PPAR) alpha is equally abundant in the liver and the testis, whereas PPAR gamma and retinoic acid receptor (RAR) alpha are expressed more in the testis. To determine whether the principal metabolite of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), or a strong peroxisome proliferator, 4-chloro-6(2,3-xylindino)-2-pyrimidinylthioacetic acid (Wy-14,643), have a differential effect in Sertoli and liver cells by altering the function of RAR alpha and PPARs, their nuclear trafficking patterns were compared in Sertoli and liver cells after treatment. Both MEHP and Wy-14,643 increased the nuclear localization of PPAR alpha and PPAR gamma in Sertoli cells, but they decreased the nuclear localization of RAR alpha, as previously shown. Both PPAR alpha and PPAR gamma were in the nucleus and cytoplasm of liver cells, but RAR alpha was predominant in the cytoplasm, regardless of the treatment. At the molecular level, MEHP and Wy-14,643 reduced the amount of phosphorylated mitogen-activated protein kinase (activated MAPK) in Sertoli cells. In comparison, both MEHP and Wy-14,643 increased phosphorylated MAPK in liver cells. These results suggest that phthalates may cause contrasting effects on the testis and the liver by differential activation of the MAPK pathway, RAR alpha, PPAR alpha, and PPAR gamma in these organs.