Metabolism of n-butyl benzyl phthalate in the female Wistar rat. Identification of new metabolites

Unraveling the contribution of dietary intake to human phthalate internal exposure

Human exposure to phthalates (PAEs) occurs primarily through diet, but the contribution of dietary exposure to the total internal exposure of PAEs has not been well studied. This work investigated the relationship between dietary exposure and human internal exposure to PAEs. Daily food samples were determined to evaluate the health risk of dietary exposure, and phthalate metabolites (mPAEs) were determined from urine samples of 360 volunteers of Guangzhou to assess their internal exposure. The total mPAEs concentration in the urine samples ranged from 8.43 to 1872 ng/mL, with mono-(2-ethylhexyl) phthalate (MEHP), mono-n-butyl phthalate (MnBP), and mono-isobutyl phthalate (MiBP) being the most predominant mPAEs. The concentration of PAEs in food ranged from n.d-40200 μg/kg, and benzyl butyl phthalate (BBzP), di-n-butyl phthalate (DnBP) and di-(2-ethylhexyl) phthalate (DEHP) were the most prevalent. PAE exposure was significantly associated with age, and children exhibited the highest concentration of mPAEs. Using Monte Carlo simulation to estimate PAE exposure's health risk eliminated uncertainties caused by single-point sampling and provided more reliable statistical results. The hazard quotient (HQ) was used to evaluate PAE exposure health risks. The results showed that 37% of the volunteers had HQ levels higher than 1 based on urinary mPAE concentrations, while 24% of the volunteers had HQ levels greater than 1 because of dietary exposure to PAEs. Dietary intake was the predominant exposure route for PAEs, and accounted for approximately 65% (24% out of 37%) of the cases where HQ levels exceeded 1. The work revealed the correlation between dietary external and internal exposure to PAEs, and further studies are needed to better understand the implications.

Identifying xenobiotic metabolites with in silico prediction tools and LCMS suspect screening analysis

Understanding the metabolic fate of a xenobiotic substance can help inform its potential health risks and allow for the identification of signature metabolites associated with exposure. The need to characterize metabolites of poorly studied or novel substances has shifted exposure studies towards non-targeted analysis (NTA), which often aims to profile many compounds within a sample using high-resolution liquid-chromatography mass-spectrometry (LCMS). Here we evaluate the suitability of suspect screening analysis (SSA) liquid-chromatography mass-spectrometry to inform xenobiotic chemical metabolism. Given a lack of knowledge of true metabolites for most chemicals, predictive tools were used to generate potential metabolites as suspect screening lists to guide the identification of selected xenobiotic substances and their associated metabolites. Thirty-three substances were selected to represent a diverse array of pharmaceutical, agrochemical, and industrial chemicals from Environmental Protection Agency's ToxCast chemical library. The compounds were incubated in a metabolically-active in vitro assay using primary hepatocytes and the resulting supernatant and lysate fractions were analyzed with high-resolution LCMS. Metabolites were simulated for each compound structure using software and then combined to serve as the suspect screening list. The exact masses of the predicted metabolites were then used to select LCMS features for fragmentation via tandem mass spectrometry (MS/MS). Of the starting chemicals, 12 were measured in at least one sample in either positive or negative ion mode and a subset of these were used to develop the analysis workflow. We implemented a screening level workflow for background subtraction and the incorporation of time-varying kinetics into the identification of likely metabolites. We used haloperidol as a case study to perform an in-depth analysis, which resulted in identifying five known metabolites and five molecular features that represent potential novel metabolites, two of which were assigned discrete structures based on in silico predictions. This workflow was applied to five additional test chemicals, and 15 molecular features were selected as either reported metabolites, predicted metabolites, or potential metabolites without a structural assignment. This study demonstrates that in some-but not all-cases, suspect screening analysis methods provide a means to rapidly identify and characterize metabolites of xenobiotic chemicals.

Experimental study on the influence of virtual tourism spatial situation on the tourists' temperature comfort in the context of metaverse

The Metaverse is a new application of the internet and social form which integrates a myriad of new technologies. It can not only create a parallel space that is closely connected to the real world while highly independent, but also bring the immersive experience of virtual scenarios without delay. The virtual tourism space situations that integrate realistic visual, audio, and temperature sensations can restore the real tourism environment to the greatest extent, and improve tourists' perception and satisfaction with the experience. The purpose of this experimental lab study is to examine the effects of the virtual tourism audio-visual conditions and environmental temperature on tourists' thermal sensation and temperature comfort. VR equipment and microclimate simulation technology was applied in a 3 × 2 × 2 experimental design (n = 180), simulating the virtual tourism scenarios. Electrocardiogram devices were also employed to assess participants' physiological indicators. Study results suggest that: (1) Virtual tourism spatial situations (environmental temperature and audio-visual conditions) significantly affect participants' thermal sensation and part of the physiological indicators; (2) Virtual tourism spatial situations (environmental temperature and audio-visual conditions) significantly affect participants' temperature comfort; and (3) Physiological responses (indicators) mediate the effect from tourism spatial situations to temperature comfort. The study mainly contributes to the literature about virtual tourism experience and spatial situations under the concept of the Metaverse, as well as provides theoretical and managerial implications for the development of "immersive" virtual tourism scenarios.

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

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

The Alginate Immobilization of Metabolic Enzymes Platform Retrofits an Estrogen Receptor Transactivation Assay With Metabolic Competence

The U.S. EPA Endocrine Disruptor Screening Program utilizes data across the ToxCast/Tox21 high-throughput screening (HTS) programs to evaluate the biological effects of potential endocrine active substances. A potential limitation to the use of in vitro assay data in regulatory decision-making is the lack of coverage for xenobiotic metabolic processes. Both hepatic- and peripheral-tissue metabolism can yield metabolites that exhibit greater activity than the parent compound (bioactivation) or are inactive (bioinactivation) for a given biological target. Interpretation of biological effect data for both putative endocrine active substances, as well as other chemicals, screened in HTS assays may benefit from the addition of xenobiotic metabolic capabilities to decrease the uncertainty in predicting potential hazards to human health. The objective of this study was to develop an approach to retrofit existing HTS assays with hepatic metabolism. The Alginate Immobilization of Metabolic Enzymes (AIME) platform encapsulates hepatic S9 fractions in alginate microspheres attached to 96-well peg lids. Functional characterization across a panel of reference substrates for phase I cytochrome P450 enzymes revealed substrate depletion with expected metabolite accumulation. Performance of the AIME method in the VM7Luc estrogen receptor transactivation assay was evaluated across 15 reference chemicals and 48 test chemicals that yield metabolites previously identified as estrogen receptor active or inactive. The results demonstrate the utility of applying the AIME method for identification of false-positive and false-negative target assay effects, reprioritization of hazard based on metabolism-dependent bioactivity, and enhanced in vivo concordance with the rodent uterotrophic bioassay. Integration of the AIME metabolism method may prove useful for future biochemical and cell-based HTS applications.

Degradation and mineralization of the emerging pharmaceutical pollutant sildenafil by ozone and UV radiation using response surface methodology

Pharmaceuticals and their degradation products which are present in wastewater and superficial waters are becoming an ecological issue. This research investigated the degradation and mineralization of synthetic solutions of the pharmaceutical compound sildenafil citrate (SC) by single ozonation and ozonation jointed with UV radiation (O₃/UV). The effects of initial drug concentration (50-125 mg L^-1), inlet ozone concentration (35-125 g Nm^-3), and UV radiation on SC degradation and decrease of total organic carbon (TOC) were investigated using response surface methodology based on a central composite experimental design. Through the RSM analysis, it was possible to confirm the removal of SC for the entire experimental range. Major intermediates of SC degradation were identified and a degradation pathway was proposed. The kinetics of SC degradation was modeled as a pseudo-first-order reaction with a rate constant ranging between 0.072 and 1.250 min^-1. The SC degradation and TOC removal were strongly enhanced by increasing the concentration of gaseous ozone at the inlet and incorporating UV radiation. The highest TOC removal reached at 60 min was 75%, in the O₃/UV system, with initial SC content of 50 mg L^-1 and inlet ozone concentration of 125 g Nm^-3. The degradation rate of SC was increased 3 to 9 times in the presence of UV radiation. Ozone-based advanced oxidation processes appear as a suitable alternative for treatment of the emerging pollutant SC.

Validation of an automated counting procedure for phthalate-induced testicular multinucleated germ cells

In utero exposure to certain phthalate esters results in testicular toxicity, characterized at the tissue level by induction of multinucleated germ cells (MNGs) in rat, mouse, and human fetal testis. Phthalate exposures also result in a decrease in testicular testosterone in rats. The anti-androgenic effects of phthalates have been more thoroughly quantified than testicular pathology due to the significant time requirement associated with manual counting of MNGs on histological sections. An automated counting method was developed in ImageJ to quantify MNGs in digital images of hematoxylin-stained rat fetal testis tissue sections. Timed pregnant Sprague Dawley rats were exposed by daily oral gavage from gestation day 17 to 21 with one of eight phthalate test compounds or corn oil vehicle. Both the manual counting method and the automated image analysis method identified di-n-butyl phthalate, butyl benzyl phthalate, dipentyl phthalate, and di-(2-ethylhexyl) phthalate as positive for induction of MNGs. Dimethyl phthalate, diethyl phthalate, the brominated phthalate di-(2-ethylhexyl) tetrabromophthalate, and dioctyl terephthalate were negative. The correlation between automated and manual scoring metrics was high (r = 0.923). Results of MNG analysis were consistent with these compounds' anti-androgenic activities, which were confirmed in an ex vivo testosterone production assay. In conclusion, we have developed a reliable image analysis method that can be used to facilitate dose-response studies for the reproducible induction of MNGs by in utero phthalate exposure.

Maternal phthalate exposure promotes allergic airway inflammation over 2 generations through epigenetic modifications

BACKGROUND

Prenatal and early postnatal exposures to environmental factors are considered responsible for the increasing prevalence of allergic diseases. Although there is some evidence for allergy-promoting effects in children because of exposure to plasticizers, such as phthalates, findings of previous studies are inconsistent and lack mechanistic information.

OBJECTIVE

We investigated the effect of maternal phthalate exposure on asthma development in subsequent generations and their underlying mechanisms, including epigenetic alterations.

METHODS

Phthalate metabolites were measured within the prospective mother-child cohort Lifestyle and Environmental Factors and Their Influence on Newborns Allergy Risk (LINA) and correlated with asthma development in the children. A murine transgenerational asthma model was used to identify involved pathways.

RESULTS

In LINA maternal urinary concentrations of mono-n-butyl phthalate, a metabolite of butyl benzyl phthalate (BBP), were associated with an increased asthma risk in the children. Using a murine transgenerational asthma model, we demonstrate a direct effect of BBP on asthma severity in the offspring with a persistently increased airway inflammation up to the F2 generation. This disease-promoting effect was mediated by BBP-induced global DNA hypermethylation in CD4⁺ T cells of the offspring because treatment with a DNA-demethylating agent alleviated exacerbation of allergic airway inflammation. Thirteen transcriptionally downregulated genes linked to promoter or enhancer hypermethylation were identified. Among these, the GATA-3 repressor zinc finger protein 1 (Zfpm1) emerged as a potential mediator of the enhanced susceptibility for T_H2-driven allergic asthma.

CONCLUSION

These data provide strong evidence that maternal BBP exposure increases the risk for allergic airway inflammation in the offspring by modulating the expression of genes involved in T_H2 differentiation through epigenetic alterations.

Long-term exposure assessment to phthalates: How do nail analyses compare to commonly used measurements in urine

Phthalate esters (PEs) are easily metabolized and commonly excreted via urine within 24h, therefore their bioaccumulation potential is thought to be rather low. In the present study, we developed a sample preparation combined with a new microextraction method to measure seven PE metabolites in nails. The use of whole nails did not result in significantly different levels compared to powdered nails, which makes the method very fast and user friendly. The method was validated using whole nails showing good accuracy, satisfactory precision and low limits of quantification (2-14ng/g). Although method development was the primary aim of the study, the method was also applied to real samples. PEs were measured in nails of 9 individuals collected at 2 distinct time points (15 days apart) and compared to levels in the respective urine samples (daily morning sample for 15 days). Additionally two volunteers have collected two more urine spots (afternoon and evening) per day. Major metabolites in nails were mono (ethyl hexyl) phthalate (MEHP), monoethyl phthalate (MEP) and sum of mono-n-butyl and mono-isobutyl phthalate (Σ(MnBP, MiBP)) while MEP and Σ(MnBP, MiBP) were the major ones identified in urine. In urine, first void morning urine reflected higher total excretion (sum of PEs of 7.0μg/g creatinine) for all individuals than the afternoon/evening voids. Participants also filled a questionnaire regarding their life-style. The use of hand care products and consumption of pre-packed food was associated with di-(2-ethylhexyl) phthalate (DEHP) oxidative metabolites, while the use of medical devices with butylbenzyl phthalate (BBzP) exposure. Although the metabolism (rate) and other factors that influence the transfer of the analytes from blood or other body compartments into nails needs further investigation, nails can be used to assess exposure to PEs. From our knowledge, urine reflects the excretion of PEs on 'daily basis' while nails show less fluctuation and more stable levels.

Benzyl butyl phthalate promotes adipogenesis in 3T3-L1 preadipocytes: A High Content Cellomics and metabolomic analysis

Benzyl butyl phthalate (BBP) has been known to induce developmental and reproductive toxicity. However, its association with dysregulation of adipogenesis has been poorly investigated. The present study aimed to examine the effect of BBP on the adipogenesis, and to elucidate the underlying mechanisms using the 3T3-L1 cells. The capacity of BBP to promote adipogenesis was evaluated by multiple staining approaches combined with a High Content Cellomics analysis. The dynamic changes of adipogenic regulatory genes and proteins were examined, and the metabolite profile was identified using GC/MC based metabolomic analysis. The High Content analysis showed BBP in contrast with Bisphenol A (BPA), a known environmental obesogen, increased lipid droplet accumulation in a similar dose-dependent manner. However, the size of the lipid droplets in BBP-treated cells was significantly larger than those in cells treated with BPA. BBP significantly induced mRNA expression of transcriptional factors C/EBPα and PPARγ, their downstream genes, and numerous adipogenic proteins in a dose and time-dependent manner. Furthermore, GC/MC metabolomic analysis revealed that BBP exposure perturbed the metabolic profiles that are associated with glyceroneogenesis and fatty acid synthesis. Altogether, our current study clearly demonstrates that BBP promoted the differentiation of 3T3-L1 through the activation of the adipogenic pathway and metabolic disturbance.

Sensitive liquid chromatography-tandem mass spectrometry method for the simultaneous determination of benzyl butyl phthalate and its metabolites, monobenzyl phthalate and monobutyl phthalate, in rat plasma, urine, and various tissues collected from a toxicokinetic study

This study describes the development of a sensitive liquid chromatography-electrospray-tandem mass spectrometry method for the simultaneous determination of benzyl butyl phthalate (BBP) and its major metabolites, monobenzyl phthalate (MBzP) and monobutyl phthalate (MBuP), in rat plasma, urine, and 10 different tissues. The method was validated with regard to the specificity, linearity, precision, accuracy, lower limit of quantification (LLOQ), recovery, and stability by using the matrix-matched quality control samples. The assay achieved LLOQ of 1 ng/ml of BBP for plasma and urine, 4 ng/g for kidney and liver, 10 ng/g for fat, and 20 ng/g for all other tissues. For MBzP and MBuP, the assay achieved LLOQ of 5 ng/ml for plasma and urine, 10 ng/g for fat, and 20 ng/g for all other tissues. The disposition of BBP was characterized by a large volume of distribution (71.1-82.9 l/kg) and a high clearance (838.7-871.0 ml/min/kg). It was extensively metabolized to MBzP and MBuP, with their levels consistently exceeding the BBP levels. The distribution of BBP, MBzP, and MBuP to tissues of kidney, liver, stomach, small intestine, large intestine, spleen, brain, testis, thyroid, and fat was determined under steady-state conditions. For BBP, the steady-state tissue-to-plasma partition coefficient (K p) was the highest for fat (25.0) followed by small intestine (2.6), thyroid (2.0), and stomach (1.1). In contrast, for MBzP and MBuP, it was the highest for kidney (2.0 and 4.3, respectively) and liver (4.3 and 2.1, respectively) but was less than unity for all other tissues. The developed assay method and findings of this study may be useful to evaluate the exposure and toxic potential of BBP and its metabolites in risk assessment.

Kinetics of the degradation of n-butyl benzyl phthalate using O₃/UV, direct photolysis, direct ozonation and UV effects

The aim of this work is to study the degradation kinetics of the endocrine disruptor benzyl butyl phthalate using ozone and UV radiation. The model comprises four parallel subsystems that are identified and isolated: (1) direct photolysis, (2) direct ozonation in the absence of hydroxyl radicals, (3) complete ozonation (direct + indirect oxidation), and (4) ozone + UV. To determine the nature of ozone attacks and the influence of ·OH radicals on O3 activity, two sets of experiments were performed: (i) conventional ozonation and (ii) the same ozonation experiments in the presence of tert-butanol as radical scavenger, where only the reactions involving molecular ozone are present. The explored variables were (i) ozone concentration, (ii) incident radiation rate at the reactor windows, (iii) reaction pH, and (iv) the presence of radical scavengers. Major intermediates of BBP degradation were identified. Degradation kinetics was correctly modeled by a pseudo-second-order kinetic model based on the sum of all the effects occurring during the treatment. The corresponding kinetic constants were obtained, and the relative contributions of each of the considered subsystems were evaluated.

Considerations for estimating daily intake values of nonpersistent environmental endocrine disruptors based on urinary biomonitoring data

Human exposure to chemicals may be estimated by back-calculating urinary concentrations resulting from biomonitoring studies if knowledge of the chemical's toxicokinetic properties is available. In this paper, available toxicokinetic data for back-calculating urinary concentrations into daily intake values for bisphenol A (BPA), phthalates, parabens, and triclosan (TCS) are reviewed and knowledge gaps are identified. Human data is evaluated and presented with relevant animal data. Focus is on the recovery of the administered dose, the route of administration, and differences between humans and animals. Two human toxicokinetic studies are currently used to conclude that an oral dose of BPA is recoverable in urine and that no free BPA is present in plasma in spite of several contradicting biominotoring studies. Urinary recovery of an oral dose of phthalates in humans is complicated to assess due to extensive metabolism. In animals using14C-marked phthalates, near-complete recovery is observed. An oral dose of14C-marked parabens is also almost completely recovered in animals. In both humans and animals, however, two unspecific metabolites are formed, which complicates the back-calculation of parabens in humans. The recovery of both oral and dermal TCS in humans has been studied, but due to background levels of TCS, the back-calculation is difficult to perform. In conclusion, due to limited data, reasonable estimates of daily intake values based on urinary data are often not possible to obtain. Several knowledge gaps are identified and new studies are suggested. The route of administration used in toxicokinetic studies often does not match realistic scenarios.

Determination des metabolites monoester de butylbenzyl-phthalate (bbp) par gcms dans les urines de personnes exposees: analysis of the monoester metabolites of butylbenzyl phthalate by gc-ms in urine of exposed workers

A method of analysis was developed to determine free and glucuronated monobutyl phthalate (BuP) and monobenzyl phthalate (BeP) in urine for the assessment of exposure of man to butylbenzyl phthalate (BBP) in the workplace and in the environment. This method has also been applied in pharmacokinetic studies in experimental animals and the determination in urine of exposed workers. Urine samples are first subjected to enzymatic hydrolysis with ß-glucuronidase to enable the measurement of the total amount of monophthalates excreted. A fraction of the hydrolysate is used for further analysis. Monohexyl phthalate is added as an internal standard and the hydrolysed urine extracted with a n-hexane/ dichloromethane mixture after acidification and saturation with salt. The organic fractions are washed, dehydrated and evaporated. The residue is methylated by means of diazomethane dissolved in diethylether, evaporated and further purified by extraction into n-hexane from an alkaline buffer. The organic fractions are evaporated and the residue redissolved in acetonitrile for analysis by ion trap GC-MS equipped with a 50 m apolar WCOT capillary column. TIC mass chromatograms are recorded from which SIM chromatograms can be derived electronically. The m/z values used are 91, 149, and 163 which provide a sufficient sensitive response and which are specific enough to pick up the methylated monophthalates under investigation. The quantitative limit of detection (LOQ) is 60 μg/L for BuP and BeP when using the Magnum ion Trap detector and 3 μg/L when using the Polaris Q in the splitless mode. The calibration curve in urine is linear from 120 μg/L to 50,000 μg/L with a coefficient of variation of less than 10 % . In case of the Polaris Q linearity started from 10 μg/L. The recovery of the method is monitored by the response signal of the internal standard in the ion chromatogram. In the event of insufficient recovery the analysis is repeated. Variations in recovery are compensated by the internal standard of which the molecular structure is very similar to the ones of the monophthalates under investigation.

Comparison of the short term toxicity of phthalate diesters and monoesters in sprague-dawley male rats

This study was carried out to investigate the short term toxicity of nine phthalate diesters including di-2 (ethylhexyl) phthalate (DEHP) , di (n-butyl) phthalate (DBP) , di-n-octyl phthalate (DnOP) , diethyl phthalate (DEP) , butylbenzyl phthalate (BBP) , dimethyl phthalate (DMP) , di-isodecyl phthalate (DIDP) , diundecyl phthalate (DUP) , and di-isononyl phthalate (DINP) and five phthalate monoesters including mono- (2-ethylhexyl) phthalate (MEHP) , monobutyl phthalate (MBuP) , monobenzyl phthalate (MBeP) , monoethyl phthalate (MEP) , monomethyl phthalate (MMP) and phthalic acid (PA) in Sprague-Dawley male rats. Animals were administered 250 mg/kg/day (monoesters and PA) or 500 mg/kg/day (diesters) of phthalate for two weeks. All animals were examined for body and organ weights, blood hematology, serum biochemistry, and urine analysis. The body weight gain was significantly lower in rats treated with BBP, DBP, DINP, MEHP, MBuP, and PA than that of control. Liver weights were significantly increased in the DEHP,DBP, DnOP, DIDP, and MEHP groups as compared to the control group. Testes weights were significantly decreased only in the DEHP-, DnOP-, and DIDP-treated groups as compared to the control. Significant differences in hematological changes were not observed in any treatment groups. Significant increases in blood glucose levels were observed in the DEHP, MEHP, and MBeP groups. Aspartate aminotransferase (AST) levels were significantly increased in the DBP, DUP, DINP, MBuP, and MBeP groups, whereas alanine aminotransferase (ALT) levels were significantly increased only in the DEHP and MEHP groups. Serum ALP levels were significantly higher in phthalate diester (500 mg/kg/day) -treated rats as compared to control. However, the total cholesterol level was significantly reduced in the DEHP- and DIDP-treated groups, whereas serum triglyceride (TG) levels were higher in the DINP-, MEHP-, and MBuP-treated groups. These results suggest that short term toxicity of phthalate monoesters produces adverse effects as similar to phthalate diesters in Sprague-Dawley rats.

Impact of benzyl butyl phthalate on shoaling behavior in Fundulus heteroclitus (mummichog) populations

Fundulus heteroclitus preference for association with familiar conspecifics of similar body length was impacted by benzyl butyl phthalate (BBP); this was found to be a statically significant result with a p < 0.0001. When presented with equally sized shoals consisting of either large or small fish, the majority of unexposed (84%) and acetone exposed control (82%) fish selected the shoal of large fish. A small number of control fish chose either the shoal of small fish (6% and 10%) or the neutral zone (10% and 8%) where they were clear morphological outliers. Fish exposed to 0.1 mg/L BBP exposure daily for four weeks selected the shoal of small fish more often than unexposed or acetone controls (7.5- and 4.5-fold respectively). They also remained in the neutral zone and displayed agitation at levels more than twice that of control. Agitation and shoal choice disruption are quantifiable behavioral responses that support the use of F. heteroclitus as a model for detecting sub-lethal BBP exposure.

Identification of potential biomarkers of exposure to di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH), an alternative for phthalate plasticizers

Di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH) is used as an alternative for some phthalate plasticizers. In rats, DINCH mostly eliminates in feces as cyclohexane-1,2-dicarboxylic acid (CHDA), mono isononyl ester (MINCH) or in urine as CHDA. However, CHDA is not a specific biomarker of DINCH and measuring MINCH in feces is impractical. To identify additional potential biomarkers, we administered DINCH (500 mg/kg body weight) in a single subcutaneous (SC) or oral dose to four adult female Sprague-Dawley rats. We collected 24-h urine samples before dosing (to be used as controls) and 24-h and 48-h after dosing, and serum at necropsy after 48 h. We positively identified and accurately quantified CHDA and cyclohexane-1,2-dicarboxylic [corrected] acid, mono hydroxyisononyl ester (MHNCH) using authentic standards. Moreover, we tentatively identified MINCH and 12 oxidative metabolites, including 4 cyclohexane ring oxidation products, based on their mass spectrometric-fragmentation patterns. CHDA and MHNCH levels were higher in the urine collected 24 h after oral than SC administration. By contrast, 48-h after dosing, CHDA urinary levels were similar regardless of the exposure route. We detected all but two of the urine metabolites also in serum. Levels of CHDA and MHNCH in serum were lower than in the two post-dose urine collections. Our results suggest that several urinary oxidative metabolites, specifically CHDA, mono oxoisononyl ester and MHNCH may be used as specific biomarkers of DINCH exposure in humans.

Urinary and serum metabolites of di-n-pentyl phthalate in rats

Di-n-pentyl phthalate (DPP) is used mainly as a plasticizer in nitrocellulose. At high doses, DPP acts as a potent testicular toxicant in rats. We administered a single oral dose of 500 mg kg(-1)bw of DPP to adult female Sprague-Dawley rats (N=9) and collected 24-h urine samples 1d before and 24- and 48-h after DPP was administered to tentatively identify DPP metabolites that could be used as exposure biomarkers. At necropsy, 48 h after dosing, we also collected serum. The metabolites were extracted from urine or serum, resolved with high performance liquid chromatography, and detected by mass spectrometry. Two DPP metabolites, phthalic acid (PA) and mono(3-carboxypropyl) phthalate (MCPP), were identified by using authentic standards, whereas mono-n-pentyl phthalate (MPP), mono(4-oxopentyl) phthalate (MOPP), mono(4-hydroxypentyl) phthalate (MHPP), mono(4-carboxybutyl) phthalate (MCBP), mono(2-carboxyethyl) phthalate (MCEP), and mono-n-pentenyl phthalate (MPeP) were identified based on their full scan mass spectrometric fragmentation pattern. The ω-1 oxidation product, MHPP, was the predominant urinary metabolite of DPP. The median urinary concentrations (μg mL(-1)) of the metabolites in the first 24h urine collection after DPP administration were 993 (MHPP), 168 (MCBP), 0.2 (MCEP), 222 (MPP), 47 (MOPP), 26 (PA), 16 (MPeP), and 9 (MCPP); the concentrations of metabolites in the second 24 h urine collection after DPP administration were significantly lower than in the first collection. We identified some urinary metabolic products in the serum, but at much lower levels than in urine. Because of the similarities in metabolism of phthalates between rats and humans, based on our results and the fact that MHPP can only be formed from the metabolism of DPP, MHPP would be the most adequate DPP exposure biomarker for human exposure assessment. Nonetheless, based on the urinary levels of MHPP, our preliminary data suggest that human exposure to DPP in the United States is rather limited.

Removal of the endocrine disrupter butyl benzyl phthalate from the environment

Butyl benzyl phthalate (BBP), an aryl alkyl ester of 1,2-benzene dicarboxylic acid, is extensively used in vinyl tiles and as a plasticizer in PVC in many commonly used products. BBP, which readily leaches from these products, is one of the most important environmental contaminants, and the increased awareness of its adverse effects on human health has led to a dramatic increase in research aimed at removing BBP from the environment via bioremediation. This review highlights recent progress in the degradation of BBP by pure and mixed bacterial cultures, fungi, and in sludge, sediment, and wastewater. Sonochemical degradation, a unique abiotic remediation technique, and photocatalytic degradation are also discussed. The degradation pathways for BBP are described, and future research directions are considered.

Comparative toxicological evaluation of phthalate diesters and metabolites in Sprague-Dawley male rats for risk assessment

In order to comparatively assess the systemic toxicity and sperm parameters, nine phthalate diesters, including di(2-ethylhexyl) phthalate (DEHP), di(n-butyl) phthalate (DBP), di-n-octyl phthalate (DnOP), diethyl phthalate (DEP), butylbenzyl phthalate (BBP), dimethyl phthalate (DMP), di-isodecyl phthalate (DIDP), diundecyl phthalate (DUP), and di-isononyl phthalate (DINP), and five phthalate monoesters, including mono(2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MBuP), monobenzyl phthalate (MBeP), monoethyl phthalate (MEP), monomethyl phthalate (MMP), and phthalic acid (PA) were administered orally to Sprague-Dawley male rats at 250 (phthalate monoesters and PA) or 500 mg/kg body weight (bw)/d (phthalate diesters) for 4 wk. Liver weights were significantly increased in g roups treated with DEHP, DBP, BBP, DIDP, DINP, MEHP, and MBuP compared to the control. Testes weights were significantly reduced only in DEHP, DBP, and MEHP-treated groups compared to the control. Significant decreases in red blood cell (RBC) and hematocrit (Ht) levels were observed in DEHP-treated rats, whereas significant increases in mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and platelet (PLT) levels were found in the DEHP-treated group. Hemoglobin (Hb) level was reduced only in the DMP group. Similar to effects on testis and epididymal weights, DEHP and MEHP significantly reduced sperm numbers and motility. In particular, DnOP, DBP, BBP, MEP, MBuP, DUP, DINP, and MBeP significantly lowered the sperm counts and sperm motility of epididymal sperm, detected by a change in the sperm motion parameters. The strongest to the weakest adverse effects for sperm motility were as follows: DEHP > DBP > DnOP > DUP > DIDP > BBP among diesters and MBuP > MEP > MEHP among monoesters, respectively. These results suggest that the adverse effects of phthalate esters (PEs) on sperm parameters in male rats are greater with phthalate diesters than monoesters, which may be useful for the risk assessment of phthalates.

Cross validation and ruggedness testing of analytical methods used for the quantification of urinary phthalate metabolites

Since the publication of our first analytical method in 2000 to detect and quantify phthalate metabolites in human urine, we have modified the method several times to improve performance, reduce the volume of matrix and solvents used, and to increase the number of analytes in one analytical run. We performed cross method validation and ruggedness testing after each modification to ensure that the analytical method adopted is robust and produces accurate and reproducible data when compared to the previously used method. Here, we present the results from the evaluation of the ruggedness of our analytical approach under variable experimental conditions, using the current analytical method. Minor deviations of the standard experimental conditions, i.e., pH, incubation time, amount of deconjugation enzyme, and incubation temperature, had no effect on final analyte concentrations. Furthermore, we validated the method to ensure accuracy at concentrations beyond the highest calibration standard. The concentrations obtained by using a lower volume of urine agreed well with original levels, suggesting broad linear calibration range as well as complete hydrolysis of the glucuronide conjugates with the standard amount of beta-glucuronidase used for deglucuronidation; also, the time of incubation (90 min) was adequate regardless of the amount of glucuronide present. We also summarize the precision of concentration data acquired by the five different analytical approaches we have used since 2000. The correlation plots of concentration data for each analyte obtained from split sample analysis, using three of these approaches, produced linear curves (R(2)>0.98) with slopes and intercepts that were not statistically different (p>0.05) from 1 and 0, respectively. These results suggest that the data are reproducible and accurate, regardless of the analytical method used. Furthermore, analysis of quality control urine samples made over the years confirmed the stability of the phthalate metabolites in urine at -70 degrees C for several years and the consistency of the analytical measurements obtained by using various methodological approaches over time.

Elucidation of n-butyl benzyl phthalate biodegradation using high-performance liquid chromatography and gas chromatography–mass spectrometry

n-Butyl benzyl phthalate (BBP) is an endocrine-disrupting chemical. A bacterium species capable of using BBP as the sole source of carbon and energy was isolated from mangrove sediment. Effects of BBP concentration, pH, temperature, and salinity on BBP biodegradation were studied. The optimum pH, temperature, and salinity for the BBP biodegradation were 7.0, 37 degrees C, and 15 g L(-1), respectively. BBP was completely degraded within 6 days under optimum conditions, and the biodegradation of BBP could be fitted to a first-order kinetic model. The major metabolites of BBP biodegradation were identified as mono-butyl phthalate, mono-benzyl phthalate, phthalic acid, and benzoic acid by using high-performance liquid chromatography and gas chromatography-mass spectrometry. A preliminary metabolic pathway was proposed for the biodegradation of BBP.

Determination of phthalates in water using fiber introduction mass spectrometry

Fiber introduction mass spectrometry (FIMS)-a direct coupling of SPME and MS-using selective ion monitoring (SIM) was used to detect and quantify dimethylphthalate (DMP), diethylphthalate (DEP) and dipropylphthalate (DPP) in mineral water. In FIMS, a chromatographic silicone septum is the only barrier between ambient and the high-vacuum mass spectrometer, permitting direct introduction of the SPME fiber into the ionization region of the equipment. After their thermal desorption and ionization and dissociation, the extracted phthalates are detected and quantitated by MS. Three types of SPME fibers were screened for best analyte sorption/desorption behaviors: 100 microm polydimethylsiloxane (PDMS), 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) and 65 microm Carbowax/divinylbenzene (CW/DVB). The PDMS/DVB and CW/DVB fibers were then evaluated for precision, and quantitative figures of merit were assessed for extractions using the PDMS/DVB fiber, which displayed the best overall performance. FIMS with the PDMS/DVB fiber allows simple extraction and MS detection and quantitation of DMP in water with good linearity and precision, and at concentrations as low as 3.6 microg L(-1). The LD and LQ of FIMS are below the maximum phthalate concentration allowed by the USEPA for drinking water (6 microg L(-1)).

Postexposure effects of DDE and butylbenzylphthalate on feeding behavior in threespine stickleback

In a laboratory experiment we documented effects of sublethal concentrations of p,p'-2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE) and butylbenzylphthalate (BBP) on feeding behavior in threespine stickleback Gasterosteus aculeatus. The fish were exposed for 31 days to either BBP (10 or 100 microg/L) or DDE (5 or 50 microg/L) or to a mixture of BBP and DDE in the corresponding concentrations. Five weeks after exposure termination, we showed that fish that had been exposed to the higher concentrations of DDE and/or BBP initiated feeding more often than control fish. The latency time to feeding (ranging from 0.25 to 5.0 min) differed between control fish and fish exposed to mixtures of DDE and BBP. This experiment shows that feeding behavior may be used as a suitable behavioral variable in the detection of effects of pollutants even long time after the termination of exposure.

Decreased anogenital distance and increased incidence of undescended testes in fetuses of rats given monobenzyl phthalate, a major metabolite of butyl benzyl phthalate

The objective of this study was to determine the adverse effects of monobenzyl phthalate (MBeP), a major metabolite of butyl benzyl phthalate (BBP), on the development of the reproductive system, and to assess the role of MBeP in the antiandrogenic effects of BBP. Pregnant rats were given MBeP by gavage at 167, 250, or 375 mg/kg on days 15-17 of pregnancy. Fetuses were examined on day 21 of pregnancy. Maternal body weight gain and food consumption were significantly decreased at 167 mg/kg and higher. Fetal weight was significantly decreased at 375 mg/kg. A significant increase in the incidence of undescended testes and decrease in the anogenital distance (AGD) and ratio of AGD to the cube root of body weight was found in male fetuses at 250 mg/kg and higher. The AGD and ratio of AGD to the cube root of body weight of female fetuses in the MBeP-treated groups were comparable to those in the control group. The present data indicate that MBeP produces adverse effects on the development of the reproductive system in male offspring and suggest that MBeP may be responsible for the antiandrogenic effects of BBP.

Antiandrogenic effects of dibutyl phthalate and its metabolite, monobutyl phthalate, in rats

Developmental toxicity following administration of dibutyl phthalate (DBP) and its major metabolite, monobutyl phthalate (MBuP), by gavage was determined in Wistar rats. DBP on days 0-8 of pregnancy induced an increase in the incidence of preimplantation loss at 1250 mg/kg and higher and postimplantation loss at 750 mg/kg and higher. MBuP on days 0-8 of pregnancy produced an increase in the incidence of pre- and postimplantation loss at 1000 mg/kg. DBP on days 7-15 of pregnancy caused an increase in the incidence of fetuses with malformations at 750 mg/kg. MBuP on days 7-15 of pregnancy produced an increased incidence of fetuses with malformations at 500 mg/kg and higher. DBP on days 15-17 of pregnancy resulted in a decrease in the anogenital distance (AGD) of male fetuses and increase in the incidence of fetuses with undescended testes at 500 mg/kg and higher. MBuP on days 15-17 of pregnancy caused a decreased male AGD and increased incidence of fetuses with undescended testes at 250 mg/kg and higher. No effect of DBP and MBuP on the AGD was found in female offspring. The spectrum of fetal malformations, dependence of gestational days of treatment on the manifestation of teratogenicity, and alterations in development of the male reproductive system observed after administration of DBP were in good agreement with those observed after administration of MBuP. These findings suggest that MBuP may be responsible for the induction of developmental toxic effects of DBP. The doses that produced a decrease in the AGD and undescended testes in male offspring were lower than those producing maternal toxicity, fetal malformations after administration during major organogenesis, and embryonic loss. The male reproductive system may be more susceptible than other organ systems to DBP and MBuP toxicity after maternal exposure.

Butyl benzyl phthalate affects shoaling behavior and bottom-dwelling behavior in threespine stickleback

In this laboratory experiment, the effects on fish behavior caused by butyl benzyl phthalate (BBP) were of interest. We showed that shoaling behavior and bottom-dwelling behavior in threespine stickleback, Gasterosteus aculeatus, were altered as a result of exposure to 0.1 mg/L BBP. Threespine sticklebacks, collected from a freshwater population in central Norway, were exposed to BBP for 26 days. BBP was administered daily through the water. We found that exposed fish aggregated more into one single shoal than control fish. Further, the exposed fish spent more time at the bottom of the test aquarium than the control fish. From these results we conclude that the behavior traits aggregation and bottom-dwelling activity may be suitable and sensitive in detecting effects of BBP in threespine stickleback.

Effects on development of the reproductive system in male offspring of rats given butyl benzyl phthalate during late pregnancy

The objective of this study was to determine the effects of maternal exposure to butyl benzyl phthalate (BBP) on the development of the reproductive system in male offspring. Pregnant rats were given BBP by gastric intubation at 250, 500, or 1000 mg/kg on days 15 to 17 of pregnancy. A significant decrease in maternal body weight gain and food consumption was found in rats given BBP at 500 and 1000 mg/kg. A significant decrease in the number of live fetuses per litter was found at 1000 mg/kg. The weights of male and female fetuses were significantly decreased in the groups given BBP at 1000 mg/kg. A significant increase in the incidence of fetuses with undescended testes was found at 500 and 1000 mg/kg. A significant decrease in the anogenital distance (AGD) of male fetuses was observed at 500 and 1000 mg/kg. The AGD/cube root of body weight ratio in male fetuses was also significantly reduced at 500 mg/kg and higher. The AGD and AGD/cube root of body weight ratio of female fetuses in the BBP-treated groups were comparable to those in the control group. It was concluded that BBP on days 15 to 17 of pregnancy produced adverse effects on the development of the reproductive system in male offspring.

Estrogenic activity and metabolism of n-butyl benzyl phthalate in vitro: identification of the active molecule(s)

Some phthalates are suspected to disrupt the endocrine system, especially by mimicking estrogens. N-butyl benzyl phthalate (BBP) has estrogenic effects in vitro but not in vivo. The aim of this study was to identify the active molecule(s) (parent compound and/or metabolite(s)) involved in the estrogenic activities of BBP. The estrogenic effects of BBP and its in vivo metabolites were assessed using the following tests: E-Screen, ER binding, and PR induction tests on the human breast cancer cell line MCF-7 (ER(+)). BBP, the parent compound, was a partial agonist. It stimulated MCF-7 proliferation in the E-Screen assay and increased cytosolic progesterone receptors (PR) levels in a concentration-dependent manner. No BBP metabolites were active except hippuric acid (HA), which had a weak effect at very high concentrations. BBP and HA stimulatory effects on MCF-7 proliferation were antagonized by tamoxifen. However, no competition was observed between BBP or HA and 17beta-estradiol for binding to the estrogen receptor (ER). BBP metabolism by MCF-7 cells was also investigated. After a 48-h incubation, only 10% of the initial BBP remained in the culture medium, demonstrating that BBP was extensively metabolized by the MCF-7 cells. The radioactivity recovered in the medium was represented by: mono-n-butyl phthalate (MBuP, 25%) and mono-n-benzyl phthalate (MBeP, 48%), phthalic acid (6%), and benzoic acid (3%). Since none of these metabolites had estrogenic activities, this study demonstrates that the parent compound was the active molecule involved in the in vitro estrogenic effects of BBP.

Effect of butyl benzyl phthalate on reproduction and zinc metabolism

Butyl benzyl phthalate (BBP) has been shown to be teratogenic. One mechanism contributing to the teratogenicity of several developmental toxicants, is chemical-induced changes in maternal zinc (Zn) metabolism which result in an increased synthesis of maternal liver metallothionein (Mt), and a subsequent reduction in Zn delivery to the conceptus. We investigated the effects of maternal BBP exposure on maternal-fetal Zn metabolism in Wistar rats. In study I, dams were gavaged with BBP (0,250,1000,1500 or 2000 mg/kg) on gestation days (GD) 11 through 13, and killed on GD 20. Maternal toxicity was evident in the three highest dose groups. Embryo/fetal death and small pup weights and lengths were noted in the 2000 mg BBP/kg group. Fetuses in the 1500 and 2000 mg/kg groups were characterized by poor skeletal ossification, and a high frequency of cleft palate. Rib anomalies were observed in the three highest dose groups. Maternal liver Mt concentrations were only slightly elevated in the 1500 and 2000 mg/kg groups. In study II, dams treated as above, were gavaged with 65Zn and killed 18 h later. While the 2000 mg/kg group had high percentages of 65Zn in some maternal tissues, sequestration of 65Zn in maternal liver was not evident. Thus, BBP is not a strong inducer of Mt, and the teratogenicity of BBP does not appear to be due to alterations in maternal and/or embryonic Zn metabolism.