On-line clean-up by multidimensional liquid chromatography-electrospray ionization tandem mass spectrometry for high throughput quantification of primary and secondary phthalate metabolites in human urine

Plasma phthalate levels in pubertal gynecomastia

OBJECTIVE

Several untoward health effects of phthalates, which are a group of industrial chemicals with many commercial uses including personal-care products and plastic materials, have been defined. The most commonly used, di-(2-ethylhexyl)-phthalate (DEHP), is known to have antiandrogenic or estrogenic effects or both. Mono-(2-ethylhexyl)-phthalate (MEHP) is the main metabolite of DEHP. In this study, we aimed to determine the plasma DEHP and MEHP levels in pubertal gynecomastia cases.

PATIENTS AND METHODS

The study group comprised 40 newly diagnosed pubertal gynecomastia cases who were admitted to Hacettepe University Ihsan Doğramaci Children's Hospital. The control group comprised 21 age-matched children without gynecomastia or other endocrinologic disorder. Plasma DEHP and MEHP levels were measured by using high-performance liquid chromatography. Serum hormone levels were determined in some pubertal gynecomastia cases according to the physician's evaluation.

RESULTS

Plasma DEHP and MEHP levels were found to be statistically significantly higher in the pubertal gynecomastia group compared with the control group (P < .001) (DEHP, 4.66 +/- 1.58 and 3.09 +/- 0.90 microg/mL, respectively [odds ratio: 2.77 (95% confidence interval: 1.48-5.21)]; MEHP, 3.19 +/- 1.41 and 1.37 +/- 0.36 microg/mL [odds ratio: 24.76 (95% confidence interval: 3.5-172.6)]). There was a statistically significant correlation between plasma DEHP and MEHP levels (r: 0.58; P < .001). In the pubertal gynecomastia group, no correlation could be determined between plasma DEHP and MEHP levels and any of the hormone levels.

CONCLUSIONS

DEHP, which has antiandrogenic or estrogenic effects, may be an etiologic factor in pubertal gynecomastia. These results may pioneer larger-scale studies on the etiologic role of DEHP in pubertal gynecomastia.

Urinary di(2-ethylhexyl)phthalate (DEHP)--metabolites and male human markers of reproductive function

INTRODUCTION

Phthalates are suspected to act as endocrine modulators in humans and exert reproductive toxicity. The general population is exposed to phthalates through nutrition, consumer products, medications and medical devices. The aim of the present study is to explore whether internal phthalate exposure represented by metabolites of di(2-ethylhexyl) phthalate (DEHP) can be related to human markers of reproductive function (i.e. semen concentration, motility and morphology).

METHODS

We recruited 349 men who were part of subfertile couples and were referred for fertility work-up between April 2004 and November 2005. Semen analysis was performed according to recommendations of the World Health Organization (WHO). Parameters were dichotomized based on 1999 WHO reference values for sperm concentration (<20million/ml) and motility (<50% sperm with progressive motility), as well as Tygerberg strict criteria for morphology (<4% normal forms). We analyzed internal DEHP exposure in single spot urine samples by determining its secondary metabolites mono(2-ethyl-5-oxo-hexyl)phthalate (5oxo-MEHP), mono(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP) and 5carboxy-mono(2-ethylhexyl)phthalate (5cx-MEPP) next to the monoester metabolite mono(2-ethylhexyl)phthalate (MEHP). Logistic regression was performed for the three semen parameters (concentration, motility, and normal morphology) to estimate their dependence on the sum of the four DEHP metabolites (DEHP-4) under consideration. Adjustment was performed for age, duration of abstinence, and smoking status.

RESULTS

DEHP metabolites of n=349 men (age: median=34ys) were analysed. Median concentrations [microg/l] were MEHP (n=337) 4.35, 5OH-MEHP (n=341) 12.66, 5oxo-MEHP (n=341) 9.02, and 5cx- MEPP (n=292) 14.53. Semen parameters of n=349 men were analysed by logistic regression. Semen concentration (<20mio/ml: 35%) or sperm motility (WHO A+B <50%=20%) were not found to be associated statistically significantly with the sum the DEHP metabolites (DEHP-4).

DISCUSSION

Metabolites of DEHP and other phthalates analyzed in urine are very specific for determining recent internal phthalate exposure. According to our evaluation human reproductive parameters from semen analyses do not show significant associations with concentrations of DEHP metabolites determined in spot urine sampled at the day of andrological examination.

GerES IV: phthalate metabolites and bisphenol A in urine of German children

Urine samples from GerES IV were analysed for concentrations of the metabolites of DEHP (MEHP, 5OH-MEHP, 5oxo-MEHP, 5cx-MEPP, and 2cx-MMHP), DnBP and DiBP (MnBP and MiBP), BBzP (MBzP), DiNP (7OH-MMeOP, 7oxo-MMeOP and 7cx-MMeHP), and bisphenol A (BPA) to assess the exposure of German children on a representative basis. 600 morning urine samples had been randomly chosen from stored 1800 GerES IV samples originating from 3 to 14 year old children living in Germany. All metabolites could be detected in nearly all urine samples (N=599). Descriptive data analysis leads to mean concentrations of 5-OH-MEHP and 5-oxo-MEHP of 48microg/l and 37microg/l, respectively. The mean concentration of 7OH-MMeOP was 11microg/l. MnBP, MiNP, MBzP showed mean levels of 96microg/l, 94microg/l, and 18microg/l, respectively. The concentrations of the phthalate metabolites decreased with increasing age. Compared to German adults all children showed three to five fold higher urine concentrations than adults analysed in the same decade. For some children the levels of the sum of 5OH-MEHP and 5oxo-MEHP in urine were higher than the German human biomonitoring value (HBM I) of 500mcirog/l, which indicates that adverse health effects cannot be excluded for these subjects with sufficient certainty. The mean concentration of BPA in urine was 2.7microg/l. A rough calculation of the daily intakes on the basis of the measured concentrations in urine resulted in daily intakes two orders of magnitude lower than the current EFSA reference dose of 50microg/kgbw/d.

Ultra-trace determination of phthalate ester metabolites in seawater, sediments, and biota from an urbanized marine inlet by LC/ESI-MS/MS

This study presents results of an analytical method developed for the quantification of monoalkyl phthalate esters (MPEs) in seawater, sediments, and biota. The method uses accelerated solvent extraction, solid-phase extraction, and liquid chromatography electrospray ionization tandem mass spectrometry (LC/ ESI-MS/MS). Results show the method is robust and can provide trace measurement of several MPE analytes at low parts per trillion levels in water and low parts per billion levels in sediments and biological tissues. Analyte recoveries varied between 70% and 110%. Method detection limits (MDLs) varied between 0.19 and 3.98 ng/L in seawater and between 0.024 and 0.99 ng/g in sediment and biota, which is approximately 10-50 times lower than previously reported MDLs using gas chromatography mass spectrometry. We applied the method to field collected samples of seawater, sediments, and tissues of mussels, crabs, and fish from False Creek an urbanized marine inlet near Vancouver, Canada. The results indicate residues of several MPEs can be found in surface waters, sediments, and organism tissues of this marine system. Monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), and mono-(2-ethylhexyl)-phthalate (MEHP) were frequently detected in all matrices. MnBP generally exhibited the highest concentrations among MPEs analyzed. Detectable concentrations of MPEs varied from 1 to 600 ng/L in seawater, 0.1 to 20 ng/g dry wt in sediments, and 0.1 to 600 ng/g wet wt in biota. Observed concentrations of low molecular weight MPEs in mussels were found to be significantly higher (P < 0.05) than those of corresponding parent DPEs (e.g., MnBP > DBP). Mono-iso-nonyl-phthalate (MoC9) and mono-iso-decyl phthalate (MoC10), which were routinely detected in water and sediments, were not detected in False Creek biota, indicating negligible uptake and/or in vivo bioformation of these high molecular weight MPEs. The ability to measure MPEs in complex environmental samples provided by this LC/ESI-MS/MS method expands the capability for future biomonitoring and risk assessment of phthalate plasticizers.

Phthalates Biomarker Identification and Exposure Estimates in a Population of Pregnant Women

Phthalates are known reproductive and developmental toxicants in experimental animals. However, in humans, there are few data on the exposure of pregnant women that can be used to assess the potential developmental exposure experienced by the fetus. We measured several phthalate metabolites in maternal urine, maternal serum, and cord serum samples collected at the time of delivery from 150 pregnant women from central New Jersey. The urinary concentrations of most metabolites were comparable to or less than among the U.S. general population, except for mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), three metabolites of di(2-ethylhexyl) phthalate (DEHP). The median urinary concentrations of MEHHP (109 mug/l) and MEOHP (95.1 mug/l) were more than 5 times their population-based concentrations, whereas the median urinary concentration of MEHP was more than 20 times higher. High concentration of MEHP may indicate a recent exposure to the parent chemical DEHP in the hospital shortly before the collection of the samples. Calculation of daily intakes using the urinary biomarker data reveals that none of the pregnant women tested had integrated exposures to DEHP greater than the Agency for Toxic Substances and Disease Registry's minimal risk levels (MRLs chronic 60, intermediate 100 mug/kg/day). No abnormal birth outcomes (e .g., birth weight, Apgar Score, and gestational age) were noted in those newborns whose mothers had relatively greater exposure to DEHP during the perinatal period than others in this study. Significantly greater concentrations and detection frequencies in maternal urine than in maternal serum and cord serum suggest that the urinary concentrations of the phthalate metabolites may be more reliable biomarkers of exposure than their concentrations in other biological specimens.

Time- and dose-related effects of di-(2-ethylhexyl) phthalate and its main metabolites on the function of the rat fetal testis in vitro

BACKGROUND

Endocrine-disrupting effects of phthalates are understood primarily from in utero exposures within the fetal rat testis. Nevertheless, their path of action, dose-response character, and cellular target(s) within the fetal testis are not known.

OBJECTIVES

In this study we investigated the effects of di-(2-ethylhexyl) phthalate (DEHP), mono-(2-ethylhexyl) phthalate (MEHP), and several of their metabolites on the development of organo-cultured testes from rat fetus.

METHODS

We removed testes from 14.5-day-old rat fetuses and cultured them for 1-3 days with or without DEHP, MEHP, and the metabolites.

RESULTS

DEHP (10(-5) M) produced a proandrogenic effect after 3 days of culture, whereas MEHP disrupted testis morphology and function. Leydig cells were the first affected by MEHP, with a number of them being inappropriately located within some seminiferous tubules. Additionally, we found a time- and dose-dependent reduction of testosterone. By 48 hr, gonocyte proliferation had decreased, whereas apoptosis increased. Sertoli cell number was unaffected, although some cells appeared vacuolated, and production of anti-Müllerian hormone decreased in a time- and dose-dependent manner. The derived metabolite mono-(2-ethyl-5-hydroxyhexyl) phthalate was the only one to cause deleterious effects to the rat fetal testis in vitro.

CONCLUSION

We hope that this in vitro method will facilitate the study of different phthalate esters and other endocrine disruptors for direct testicular effects.

Determination of total and free mono-n-butyl phthalate in human urine samples after medication of a di-n-butyl phthalate containing capsule

Phthalates like di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) are commonly used as plasticisers, enteric coatings in medications and their metabolites (MnBP respectively MiBP) are suspect of adverse endocrine activities. The aim of this study was to determine kinetical data in humans after the application of a drug containing 3600 microg of DnBP and to quantify main metabolites of DnBP and DiBP with and without glucuronidase treatment. Since commonly glucuronides do not exhibit endocrine activity it is of interest to determine the potentially active metabolite like free MnBP and MiBP for a valid risk assessment. After the application of one capsule containing 3600 microg of DnBP to 17 volunteers 78% (median of 2248 microg of total MnBP) of administered DnBP was found within 24h in urine. After 24h the levels of MnBP in urine were comparable to concentrations before administration showing a fast elimination. In contrast to controls in all urine samples collected within 24h after the administration of the drug free MnBP was observed with a median of 4% of total MnBP. In controls total MnBP and MiBP were found in median concentration of 23 microg/24h and about 50 microg/24h, respectively and therefore environmental exposure to DnBP is only 1% compared to medication. Since an uptake of 3600 microg in only one capsule is already above the tolerable daily intake (TDI) for DnBP of 10 microg/kg b.w. from a preventive health protection DnBP should be replaced in medical drugs.

Lactational exposure to phthalates in Southern Italy

BACKGROUND

Phthalates, reproductive toxicants in animals, are synthetic chemicals with ubiquitous human exposures because of their extensive use, with potential detrimental health effects. Infants are considered to represent a population at increased risk, as they are exposed early in life to several different sources of exposure to phthalates.

OBJECTIVES AND METHODS

Little information exists on phthalate exposure through breast milk from different geographic areas. By means of a LC/LC-MS/MS method we tested the presence of several different phthalate metabolites in breast milk from 62 healthy mothers living in Southern Italy.

RESULTS

The simple monoesters mono-isobutyl phthalate (MiBP) (median 18.8 microg/l) and mono(2-ethylhexyl) phthalate (MEHP) (median 8.4 microg/l) were present in all milk samples, whereas mono-n-butyl phthalate (MnBP) (median 1.5 microg/l) and mono-benzyl phthalate (MBzP) (median <0.3 microg/l) were found in 64.5% and 43.5% of the samples, respectively. Among the oxidative metabolites of DEHP and DiNP only mono(2-ethyl-5-carboxypentyl) phthalate (5cx-MEPP) and monoisononyl phthalate with one hydroxyl group (OH-MiNP) were detectable in one and 13 samples (21%), respectively.

CONCLUSIONS

These findings indicate that exposure to phthalates through breast milk in Southern Italian infants is comparable to that of other countries, thus confirming that human milk may represent an additional potential source of phthalate exposure in a population at increased risk. However, different milk concentrations of MiBP may suggest a different pattern of usage of di-iso-butyl phthalate in Europe, as compared to USA, whereas for the first time, we detected an oxidative DiNP metabolite, whose significance remains unclear.

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

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

Fast determination of urinary S-phenylmercapturic acid (S-PMA) and S-benzylmercapturic acid (S-BMA) by column-switching liquid chromatography-tandem mass spectrometry

Benzene and toluene are important industrial chemicals and ubiquitous environmental pollutants. The urinary mercapturic acids of benzene and toluene, S-phenylmercapturic acid (S-PMA) and S-benzylmercapturic acids (S-BMA) are specific biomarkers for the determination of low-level exposures. We have developed and validated a fast, specific and very sensitive method for the simultaneous determination of S-PMA and S-BMA in human urine using an automated multidimensional LC-MS-MS-method that requires no additional sample preparation. Analytes are stripped from urinary matrix by online extraction on a restricted access material, transferred to the analytical column and subsequently determined by tandem mass spectrometry using isotopically labelled S-PMA as internal standard. The lower limit of quantification (LLOQ) for both analytes was 0.05 microg/L urine and sufficient to quantify the background exposure of the general population. Precision within series and between series for S-PMA and S-BMA ranged from 1.0% to 12.2%, accuracy was 108% and 100%, respectively. We applied the method on spot urine samples of 30 subjects of the general population with no known exposure to benzene or toluene. Median levels (range) for S-PMA and S-BMA in non-smokers (n=15) were 0.14 microg/L (<0.05-0.26 microg/L) and 8.2 (1.6-77.4 microg/L), respectively. In smokers (n=15), median levels for S-PMA and S-BMA were 1.22 microg/L (0.17-5.75 microg/L) and 11.5 microg/L (0.9-51.2 microg/L), respectively. Due to its automation, our method is well suited for application in large environmental studies.

Two-dimensional reverse phase-reverse phase chromatography: A simple and robust platform for sensitive quantitative analysis of peptides by LC/MS. Hardware design

We have revised current two-dimensional RP-RP approaches and developed a new robust 2-D RP-RP platform. This platform was implemented on an Agilent 1100 2-D liquid chromatography system and is based on high pressure switching between two high-resolution RP columns. An independent binary gradient was implemented for each dimension. The powerful combination of dual analytical columns with independent gradient elution achieves high analyte purity, effectively eliminates matrix effects, and maximizes MS sensitivity in Q1 SIM comparable to the sensitivity enhancements of MS/MS-based methods. Implementation of dual simultaneous gradient profiles (overlapped gradients) reduces 2-D method run-time to the scale of 1-D method run-times. This robust and sensitive approach is particularly suitable for hydrophobic peptides and small proteins and can be used as a routine standard technique for enhanced on-line peptide purification coupled with mass spectrometric detection.

Phthalates: Toxicology and exposure

Phthalates are used as plasticizers in PVC plastics. As the phthalate plasticizers are not chemically bound to PVC, they can leach, migrate or evaporate into indoor air and atmosphere, foodstuff, other materials, etc. Consumer products containing phthalates can result in human exposure through direct contact and use, indirectly through leaching into other products, or general environmental contamination. Humans are exposed through ingestion, inhalation, and dermal exposure during their whole lifetime, including intrauterine development. This paper presents an overview on current risk assessments done by expert panels as well as on exposure assessment data, based on ambient and on current human biomonitoring results. Some phthalates are reproductive and developmental toxicants in animals and suspected endocrine disruptors in humans. Exposure assessment via modelling ambient data give hints that the exposure of children to phthalates exceeds that in adults. Current human biomonitoring data prove that the tolerable intake of children is exceeded to a considerable degree, in some instances up to 20-fold. Very high exposures to phthalates can occur via medical treatment, i.e. via use of medical devices containing DEHP or medicaments containing DBP phthalate in their coating. Because of their chemical properties exposure to phthalates does not result in bioaccumulation. However, health concern is raised regarding the developmental and/or reproductive toxicity of phthalates, even in environmental concentrations.

Hershberger assay for antiandrogenic effects of phthalates

The antiandrogenic effects of seven phthalates, di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), di-isononyl phthalate (DINP), di-isodecyl phthalate (DIDP), di-n-heptyl phthalate (DnHP), and mono-2-ethyhexyl phthalate (MEHP), were investigated by Hershberger assay in castrated male SD rats. An androgen agonist, testosterone (0.4 mg/kg/d), was administered for 10 consecutive days by subcutaneous (s.c.) injection as a positive control. Additionally, 20, 100, or 500 mg/kg body weight (bw)/d of 6 phthalates (DEHP, DBP, BBP, DINP, DIDP, or DnHP) or 10, 50, or 250 mg/kg bw/d of MEHP, the primary metabolite of DEHP, were also administered orally in combination with testosterone (0.4 mg/kg/d, s.c.) for 10 consecutive days, respectively. In the testosterone-treated groups, glans penis, seminal vesicles, ventral prostate, and levator ani/bulbocavernosus muscles (LABC) weights were found to be significantly increased. Ventral prostate weights were significantly decreased in animals treated with DEHP or DBP at doses of 20 mg/kg bw/d or above, 500 mg/kg bw/d DIDP, and 250 mg/kg bw/d MEHP. Seminal vesicles weights were also significantly decreased by DEHP at > 100 mg/kg bw/d, DINP at > 20 mg/kg bw/d, DIDP at 500 mg/kg bw/d, or MEHP at 50 or 250 mg/kg bw/d, respectively. In addition, LABC weights were decreased by DEHP at 500 mg/kg bw/d, DINP at 500 mg/kg bw/d, and MEHP at 50 or 100 mg/kg bw/d. These data suggest that some phthalates possess antiandrogenic activity, and that multiple cross-talk between androgen, estrogen, and steroid hormone receptors occurs.

Di-n-butylphthalate and butylbenzylphthalate - urinary metabolite levels and estimated daily intakes: pilot study for the German Environmental Survey on children

We analysed urine samples from the 2001/2002 pilot study of the German Environmental Survey on Children (GerES IV) for the concentrations of the di-n-butylphthalate (DnBP) metabolite mono-n-butylphthalate (MnBP) and the butlybenzylphthalate (BBzP) metabolite mono-benzyl-phthalate (MBzP). The study population consisted of 239 children (106 boys, 133 girls) aged between 2 and 14 years (median 8.5 years). We applied two calculation models to estimate the daily intake for the two parent phthalates from metabolite excretion. One was based on the creatinine-related metabolite concentrations; the other was based on the volume-related metabolite concentrations. Median urinary metabolite concentrations were 174 microg/l (136 microg/g creatinine) for MnBP and 19.7 microg/l (15.3 microg/g creatinine) for MBzP. Such levels have been determined in German children before. Compared to the USA, German median MnBP levels were about 3-10 times higher, whereas MBzP levels were in the same range. Median daily intakes calculated with the creatinine-based model were 4.07 (range: 0.66-76.4; 95th percentile: 14.9) microg/kg body weight (bw)/day for DnBP and 0.42 (range: 0.06-13.9; 95th percentile: 2.57) microg/kg bw/day for BBzP. Daily intakes calculated with the volume-based model were approximately two times higher with a median of 7.61 (range: 0.91-110; 95th percentile: 30.5) microg/kg bw/day for DnBP and a median of 0.77 (range: 0.05-31.3; 95th percentile: 4.48) microg/kg bw/day for BBzP. Using the creatinine model, 28 (11.7%) of the 239 children exceeded the TDI for DnBP of 10 microg/kg bw/day defined by the European Union. Employing the volume model, 89 (37.2%) children exceeded the TDI. For BBzP, no preventive limit values (TDI or RfD) were exceeded. For both phthalates and independent of the model, we found increasing daily intakes with decreasing age. Between 25% (creatinine model) and 50% (volume model) of the 2-4-year old children had daily intakes for DnBP above the TDI.

Metabolism of phthalates in humans

Phthalates are synthetic compounds widely used as plasticisers, solvents and additives in many consumer products. Several animal studies have shown that some phthalates possess endocrine disrupting effects. Some of the effects of phthalates seen in rats are due to testosterone lowering effects on the foetal testis and they are similar to those seen in humans with testicular dysgenesis syndrome. Therefore, exposure of the human foetus and infants to phthalates via maternal exposure is a matter of concern. The metabolic pathways of phthalate metabolites excreted in human urine are partly known for some phthalates, but our knowledge about metabolic distribution in the body and other biological fluids, including breast milk, is limited. Compared to urine, human breast milk contains relatively more of the hydrophobic phthalates, such as di-n-butyl phthalate and the longer-branched, di(2-ethylhexyl) phthalate (DEHP) and di-iso-nonyl phthalate (DiNP); and their monoester metabolites. Urine, however, contains relatively more of the secondary metabolites of DEHP and DiNP, as well as the monoester phthalates of the more short-branched phthalates. This differential distribution is of special concern as, in particular, the hydrophobic phthalates and their metabolites are shown to have adverse effects following in utero and lactational exposures in animal studies.

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

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

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).

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

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

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.

Integrating biomonitoring exposure data into the risk assessment process: phthalates [diethyl phthalate and di(2-ethylhexyl) phthalate] as a case study

The probability of nonoccupational exposure to phthalates is high given their use in a vast range of consumables, including personal care products (e.g., perfumes, lotions, cosmetics), paints, industrial plastics, and certain medical devices and pharmaceuticals. Phthalates are of high interest because of their potential for human exposure and because animal toxicity studies suggest that some phthalates affect male reproductive development apparently via inhibition of androgen biosynthesis. In humans, phthalates are rapidly metabolized to their monoesters, which can be further transformed to oxidative products, conjugated, and eliminated. Phthalate metabolites have been used as biomarkers of exposure. Using urinary phthalate metabolite concentrations allows accurate assessments of human exposure because these concentrations represent an integrative measure of exposure to phthalates from multiple sources and routes. However, the health significance of this exposure is unknown. To link biomarker measurements to exposure, internal dose, or health outcome, additional information (e.g., toxicokinetics, inter- and intraindividual differences) is needed. We present a case study using diethyl phthalate and di(2-ethylhexyl) phthalate as examples to illustrate scientific approaches and their limitations, identify data gaps, and outline research needs for using biomonitoring data in the context of human health risk assessment, with an emphasis on exposure and dose. Although the vast and growing literature on phthalates research could not be covered comprehensively in this article, we made every attempt to include the most relevant publications as of the end of 2005.

Automated on-line liquid chromatography–photodiode array–mass spectrometry method with dilution line for the determination of bisphenol A and 4-octylphenol in serum

A novel on-line liquid chromatography-photodiode array detection-mass spectrometry (LC-DAD-MS) system was established with restricted-access media (RAM) pre-column and dilution line combined with a column-switching valve. The serum samples were injected directly onto pre-column under diluted condition by dilution line. After elution of proteins in the serum, the analytes were backflushed onto an ODS analytical column using a six-port column-switching device. The influence of the composition of the mobile phase, for instance, organic modifer, ionic strength, pH, dilution times and the rotation time of the switching valve have been investigated using bisphenol A (BPA) and 4-octyphenol (4-OP) as analytes. The evaluations for peak responses and sensitivity were conducted by MS, and proteins were removed by RAM-column with DAD monitoring at 280 nm. The peak shape was improved by adding a dilution line, especially in the case of large volume injection (LVI), which increased the sensitivity of the analysis. The selective and sensitive quantification of BPA and 4-OP in serum sample could be finished within 25 min. The method had linearity in the range 0.1-500 ng/mL with a limit of quantification for BPA and 4-OP of 0.1 and 0.5 ng/mL, respectively. The recoveries were in the range of 80-101% with less than 9.0% RSDs. This on-line LC-MS method demonstrates potential application to evaluating the exposure and risk of BPA and 4-OP in human.

Di(2-ethylhexyl)phthalate (DEHP): human metabolism and internal exposure-- an update and latest results

Di(2-ethylhexyl)phthalate (DEHP) is a reproductive and developmental toxicant in animals and a suspected endocrine modulator in humans. There is widespread exposure to DEHP in the general population. Patients can be additionally exposed through DEHP-containing medical devices. Toxicokinetic and metabolic knowledge on DEHP in humans is vital not only for the toxicological evaluation of DEHP but also for exposure assessments based on human biomonitoring data. Secondary oxidized DEHP metabolites like mono-(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP), mono-(2-ethyl-5-carboxypentyl)phthalate (5cx-MEPP) and mono-[2-(carboxymethyl)hexyl]phthalate (2cx-MMHP) are most valuable biomarkers of DEHP exposure. They represent the major share of DEHP metabolites excreted in urine (about 70% for these four oxidized metabolites vs. about 6% for MEHP); they are immune to external contamination and possibly the ultimate developmental toxicants. Long half-times of elimination make 5cx-MEPP and 2cx-MMHP excellent parameters to measure the time-weighted body burden to DEHP. 5OH-MEHP and 5oxo-MEHP more reflect the short-term exposure. We calculated the daily DEHP intake for the general population (n = 85) and for children (n = 254). Children were significantly higher exposed to DEHP than adults. Exposures at the 95th percentile (21 and 25 microg/kg/day, respectively) scooped out limit values like the Reference Dose (RfD, 20 microg/kg/day) and the Tolerable Daily Intake (TDI, 20-48 microg/kg/day) to a considerable degree. Up to 20-fold oversteppings for some children give cause for concern. We also detected significant DEHP exposures for voluntary platelet donors (n = 12, 38 microg/kg/apheresis, dual-needle technique). Premature neonates (n = 45) were exposed to DEHP up to 100 times above the limit values depending on the intensity of medical care (median: 42 microg/kg/day; 95th percentile: 1,780 microg/kg/day).

Development of restricted-access media supports and their application to the direct analysis of biological fluid samples via high-performance liquid chromatography

A quick overview of published methods for analyzing compounds in complex biological samples reveals that the most difficult step is the clean-up or extraction of a required compound from the matrix. The strategy required to analyze exogenous compounds in biological fluids depends greatly upon the nature of the compound and upon the biomatrix. Coupled-column separation using restricted-access media as the first dimension in order to exclude macromolecules and retain micromolecules has been successfully used for a number of biological fluids. This paper presents the history of the development of restricted-access media supports and of their application to the direct injection of biological fluid samples in high-performance liquid chromatography.

Urinary oxidative metabolites of di(2-ethylhexyl) phthalate in humans

Di(2-ethylhexyl) phthalate (DEHP) is added to polyvinyl chloride (PVC) plastics used widely in medical devices and toys to impart flexibility and durability. DEHP produces reproductive and development toxicities in rodents. Initial metabolism of DEHP in animals and humans results in mono(2-ethylhexyl) phthalate (MEHP), which subsequently metabolizes to a wide range of oxidative metabolites before being excreted in urine and feces. We investigated the metabolism of DEHP in humans by identifying urinary oxidative metabolites of DEHP from individuals with urinary MEHP concentrations about 100 times higher than the median concentration in the general US population. In addition to the previously identified DEHP metabolites MEHP, mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), and mono(2-carboxymethylhexyl) phthalate (MCMHP), we also identified for the first time in humans three additional oxidative metabolites, mono(2-ethyl-3-carboxypropyl) phthalate (MECPrP), mono(2-ethyl-4-carboxybutyl) phthalate (MECBP), and mono(2-(1-oxoethyl)hexyl) phthalate (MOEHP) based on their chromatographic behavior and mass spectrometric fragmentation patterns. We also tentatively identified metabolites with two functional groups in the side alkyl chain as isomers of mono(2-hydroxyethyl-4-carboxybutyl) phthalate (MHECBP), mono(2-ethyl-4-oxo-5-carboxypentyl) phthalate (MEOCPP), and mono(2-ethyl-4-hydroxy-5-carboxypentyl) phthalate (MEHCPP). We report the presence of urinary DEHP metabolites in humans that have fewer than eight carbons in the alkyl chain. These metabolites were previously identified in rodents. Although quantitative information is not available, our findings suggest that, despite potential differences among species, the oxidative metabolism of DEHP in humans and rodents results in similar urinary metabolic products.

Mono-(3-carboxypropyl) phthalate, a metabolite of di-n-octyl phthalate

Di-n-octyl phthalate (DnOP) is found as a component of mixed C6-C10 linear-chain phthalates used as plasticizers in various polyvinyl chloride applications, including flooring and carpet tiles. Following exposure and absorption, DnOP is metabolized to its hydrolytic monoester, mono-n-octyl phthalate (MnOP), and other oxidative products. The urinary levels of one of these oxidative metabolites, mono-(3-carboxypropyl) phthalate (MCPP), were about 560-fold higher than MnOP in Sprague-Dawley rats dosed with DnOP by gavage. Furthermore, MCPP was also found in the urine of rats dosed with di-isooctyl phthalate (DiOP), di-isononyl phthalate (DiNP), di-isodecyl phthalate (DiDP), di-(2-ethylhexyl) phthalate, and di-n-butyl phthalate (DBP), although at concentrations considerably lower than in rats given similar concentrations of DnOP. The comparatively much higher urinary concentrations of MCPP than of the hydrolytic monoesters of the high-molecular-weight phthalates DiOP, DiNP, and DiDP in the exposed rats suggest that these monoesters may be poor biomarkers of exposure to their precursor phthalates and may explain the relatively low frequency of detection of these monoester metabolites in human populations. MCPP and MnOP were also measured in 267 human urine samples. The frequent detection and higher urinary concentrations of MCPP than MnOP suggest that exposure to DnOP might be higher than previously thought based on the measurements of MnOP alone. However, because MCPP is also a minor metabolite of DBP and other phthalates in rats, and the metabolism of phthalates in rodents and humans may differ, additional data on the absorption, distribution, metabolism, and elimination of MCPP are needed to completely understand the extent of human exposure to DnOP from the urinary concentrations of MCPP.

Ion/molecule reactions in a miniature RIT mass spectrometer

Ion/molecule reactions were explored in a newly developed miniature mass spectrometer fitted with a rectilinear ion trap (RIT) mass analyzer. The tandem mass spectrometry performance of this instrument is demonstrated using collision induced dissociation (CID) and ion/molecule reactions. The latter includes Eberlin transacetalization reactions and electrophilic additions. Selective detection of the chemical warfare simulant dimethyl methyl phosphonate (DMMP) was achieved through selective Eberlin reactions of its characteristic phosphonium fragment ion CH3OP(+)(O)CH3 (m/z 93), with 1,4-dioxane or 1,3-dioxolane. Efficient adduct formation as a result of electrophilic attack by the phosphonium ion on various nucleophilic reagents, including 1,1,3,3-tetramethyl urea, methanesulfonic acid methyl ester, dimethyl sulfoxide and methyl salicylate, was also observed using the RIT device. The product ions of these reactions were analyzed using CID and the characteristic fragmentation patterns of the ionic addition products were recorded using multiple-stage experiments in the miniature RIT instrument. This study clearly demonstrates that a small, home-built, miniature RIT mass spectrometer can be used to perform analytically useful ion/molecule reactions and also that instruments like this have the potential to provide a portable platform for in situ detection of organophosphorus esters and related compounds with high specificity using tandem mass spectrometry.

Di(2-ethylhexyl)phthalate (DEHP) exposure of voluntary plasma and platelet donors

Each year thousands of healthy volunteers undergo apheresis procedures to donate blood components and safe lives. However, many disposables used in apheresis contain di(2-ethylhexyl)phthalate (DEHP). This way, donors are exposed to DEHP, which is a reproductive and developmental toxicant in animals and a suspected endocrine modulator in humans. We quantified the DEHP exposure of six plasma donors, six discontinuous-flow platelet donors and six continuous-flow platelet donors by determining three specific metabolites in urine (5OH-MEHP: mono(2-ethyl-5-hydroxyhexyl)phthalate; 5oxo-MEHP: mono(2-ethyl-5-oxo-hexyl)phthalate and MEHP: mono(2-ethylhexyl)phthalate). We found maximum concentrations in urine samples after the discontinuous-flow plateletpheresis procedure with 826 microg/l for 5OH-MEHP, 774 microg/l for 5oxo-MEHP and 266 microg/l for MEHP (mean of the six volunteers). Metabolite excretions were found to be significantly (p<0.0001) higher for both plateletpheresis techniques compared to plasmapheresis and controls. Continuous-flow plateletpheresis led to significantly higher (p<0.0001) excretions than discontinuous-flow plateletpheresis. Mean absolute DEHP exposures were 1.2 mg for discontinuous- and 2.1 mg for continuous-flow plateletpheresis. Exposure for plasmapheresis (0.37 mg) was in the range of the controls (0.41 mg). Mean DEHP doses for both plateletpheresis techniques (18.1 and 32.3 microg/kg/day) were close to or exceeded the reference dose (RfD) of the US EPA and tolerable daily intake (TDI) value of the EU on the day of the apheresis. Therefore, margins of safety might be insufficient to protect especially young men and women in their reproductive age from effects on reproductivity. At present, discontinuous-flow devices should be preferred to avert conceivable health risks from plateletpheresis donors. Strategies to avoid DEHP exposure of donors during apheresis need to be developed.

Human monitoring of phthalates and risk assessment

Some phthalates, such as di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP), and their metabolites are suspected of producing teratogenic and endocrino-disrupting effects. In this study, urinary levels of phthalates (DEHP, DBP, diethyl phthalate (DEP), butylbenzyl phthalate BBP), and monoethylhexyl phthalate (MEHP, a major metabolite of DEHP) were measured by high performance liquid chromatography (HPLC) in human populations (women [hospital visitors], n = 150, and children, n = 150). Daily exposure level of DEHP in children was estimated to be 12.4 microg/kg body weight/d (male 9.9 microg/kg body weight/d, female 17.8 microg/kg body weight/d), but, in women was estimated to be 41.7 microg/kg body weight/d, which exceeded the tolerable daily intake (TDI, 37 microg/kg body weight/day) level established by the European Union (EU) Scientific Committee for Toxicity, Ecotoxicity, and the Environment (SCTEE) based on reproductive toxicity. Based on these data, hazard indices (HIs) were calculated to be 1.12 (41.7/37 TDI) for women and 0.33 (12.4/37 TDI) for children, respectively. These data suggest that Koreans (women and children) were exposed to significant levels of phthalates, which should be reduced to as low a level as technologically feasible to protect Koreans from the exposure to toxic phthalates.

Intravenous exposure to di(2-ethylhexyl)phthalate (DEHP): metabolites of DEHP in urine after a voluntary platelet donation

In this study we investigated human metabolism and excretion of DEHP after intravenous exposure. For this purpose we determined the five major DEHP metabolites in urine samples of a volunteer before and after a platelet donation (dual-needle technique). Plateletpheresis procedures are known to cause a significant DEHP exposure. We observed a sharp increase in urinary DEHP metabolite concentrations after the procedure. Maximum concentrations of 5OH-MEHP, 5oxo-MEHP, 5cx-MEPP and MEHP observed 4 h after the procedure were 822, 729, 577 and 388 microg/l respectively. 2cx-MMHP was excreted at highest concentrations after 8 h (201 microg/l). Due to longer elimination half-times, 5cx-MEPP and 2cx-MMHP were the major metabolites excreted in urine 24 h after the exposure. The 24-h-cumulative excretion of 363 microg 5cx-MEPP, 353 microg 5OH-MEHP, 309 microg 5oxo-MEHP, 178 microg MEHP and 133 microg 2cx-MMHP indicates an absolute exposure of our volunteer of about 2.6 mg DEHP. Related to the body weight this equals a dose of 31.6 microg/kg body weight/day. This indicates that current risk or preventive limit values for DEHP such as the RfD of the US EPA (20 microg/kg/day) and the TDI of the European Union (20-48 microg/kg/day) can be exceeded on the day of the plateletpheresis. The amount of the dose excreted in urine, distribution of the metabolites in urine and all other elimination characteristics after intravenous DEHP exposure are comparable to oral exposure. There are no indications that toxicokinetic behaviour and the toxicity of DEHP are fundamentally different after the two routes of exposure. Therefore, toxicological endpoints observed for DEHP after oral application should also be considered relevant for medical procedures causing intravenous DEHP exposure, like apheresis procedures. Especially women in their reproductive age need to be protected from DEHP exposures exceeding the above mentioned preventive limit values.

Exposure of nursery school children and their parents and teachers to di-n-butylphthalate and butylbenzylphthalate

OBJECTIVES

Some phthalates, among them di-n-butylphthalate (DnBP) and butylbenzylphthalate (BBzP), are known reproductive and developmental toxicants in animals and suspected endocrine disruptors in humans. Children are probably the most susceptible to these effects. To obtain an estimate of internal exposure to DnBP and BBzP we compared the excretion of their metabolites in the urine of nursery school children with that of their teachers and parents.

METHODS

We measured the urinary mono-ester metabolites of DnBP, mono-n-butylphthalate (MnBP), and BBzP, monobenzylphthalate (MBzP), in first-morning voids of 36 children (median age 4.7 years) and 19 adults (37.4 years).

RESULTS

In all samples both metabolites were detected. Urinary MnBP concentrations (in microgrammes per litre) of the children and adults were 139 and 91.8 (median), respectively. MBzP concentrations were 22.1 microg/l and 12.7 microg/l (median), respectively. Concentrations in microgrammes per gramme creatinine for MnBP were 161 for the children and 91.8 for the adults (median). The maximum concentration found for children (2249 microg/g) was approximately 15-times higher than that for adults (149 microg/g). This maximum value for children was attributed to medication that contained DnBP. If this child was excluded, the maximum concentration was 517 microg/g. MBzP concentrations for children and adults were 37.0 microg/g and 9.8 microg/g (median), respectively. The maximum concentration found for children (193 microg/g) was approximately seven-times higher than that for adults (26.7 microg/g). Creatinine-adjusted concentrations were significantly higher for children for both MBzP and MnBP (P<0.0001). MnBP and MBzP exposures were found to correlate statistically significantly within the children's cohort (r=0.723, P<0.001). Within the children's cohort we found elevated MnBP exposure to be caused by augmented use of skin-care products (P<0.05).

CONCLUSION

We have shown that the internal exposure to MnBP and MBzP in children is approximately two- to four-times higher than in adults. Correlation of internal MnBP with MBzP exposure points to common sources of exposure for both phthalates. DnBP exposure seems, at least in part, to be connected with the use of body/skin care products and certain medications.

New metabolites of di(2-ethylhexyl)phthalate (DEHP) in human urine and serum after single oral doses of deuterium-labelled DEHP

The metabolism of di(2-ethylhexyl)phthalate (DEHP) in humans was studied after three doses of 0.35 mg (4.7 microg/kg), 2.15 mg (28.7 microg/kg) and 48.5 mg (650 microg/kg) of D4-ring-labelled DEHP were administered orally to a male volunteer. Two new metabolites, mono(2-ethyl-5-carboxypentyl)phthalate (5cx-MEPP) and mono[2-(carboxymethyl)hexyl]phthalate (2cx-MMHP) were monitored for 44 h in urine and for 8 h in serum for the high-dose case, in addition to the three metabolites previously analysed: mono(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP) and mono(2-ethylhexyl)phthalate (MEHP). For the medium- and low-dose cases, 24 h urine samples were analysed. Up to 12 h after the dose, 5OH-MEHP was the major urinary metabolite, after 12 h it was 5cx-MEPP, and after 24 h it was 2cx-MMHP. The elimination half-lives of 5cx-MEHP and 2cx-MMHP were between 15 and 24 h. After 24 h 67.0% (range: 65.8-70.5%) of the DEHP dose was excreted in urine, comprising 5OH-MEHP (23.3%), 5cx-MEPP (18.5%), 5oxo-MEHP (15.0%), MEHP (5.9%) and 2cx-MMHP (4.2%). An additional 3.8% of the DEHP dose was excreted on the second day, comprising 2cx-MMHP (1.6%), 5cx-MEPP (1.2%), 5OH-MEHP (0.6%) and 5oxo-MEHP (0.4%). In total about 75% of the administered DEHP dose was excreted in urine after two days. Therefore, in contrast to previous studies, most of the orally administered DEHP is systemically absorbed and excreted in urine. No dose dependency in metabolism and excretion was observed. The secondary metabolites of DEHP are superior biomonitoring markers compared to any other parameters, such as MEHP in urine or blood. 5OH-MEHP and 5oxo-MEHP in urine reflect short-term and 5cx-MEHP and 2cx-MMHP long-term exposure. All secondary metabolites are unsusceptible to contamination. Furthermore, there are strong hints that the secondary oxidised DEHP metabolites-not DEHP or MEHP-are the ultimate developmental toxicants.

DEHP metabolites in urine of children and DEHP in house dust

Urine samples from the 2001/2002 pilot study for the German Environmental Survey on children (GerES IV) were analysed for concentrations of the primary DEHP metabolite MEHP (mono(2-ethylhexyl)phthalate) and two secondary DEHP metabolites SOH-MEHP (2-ethyl-5-hydroxy-hexylphthalate) and 5oxo-MEHP (2-ethyl-5-oxo-hexylphthalate). Urine samples had been taken from 254 children aged 3 to 14. In addition, DEHP was analysed in house dust samples. These samples had been collected with vacuum cleaners in the homes of the children. The geometric mean (GM) was 7.9 microg/l for MEHP in urine, and the GMs for the secondary metabolites 5OH-MEHP and 5oxo-MEHP were 52.1 microg/l and 39.9 microg/l. 5OH-MEHP and 5oxo-MEHP concentrations were highly correlated (r = 0.98). The correlations of 5OH-MEHP and 5oxo-MEHP with MEHP were also high (r = 0.72 and r = 0.70). The concentrations of 5OH-MEHP and 5oxo-MEHP were 8.0-fold and 6.2-fold higher than the concentrations of MEHP. The ratios 5OH-MEHP/Soxo-MEHP and 5oxo-MEHP/MEHP decreased with increasing age. Boys showed higher concentrations than girls for all three metabolites of DEHP in urine. Children aged 13-14 had the lowest mean concentrations of the secondary metabolites in urine. The house dust analyses revealed DEHP contamination of all samples. The GM was 508 mg/kg dust. No correlation could be observed between the levels of any of the urinary DEHP metabolites and those of DEHP in house dust.

Biological monitoring of the five major metabolites of di-(2-ethylhexyl)phthalate (DEHP) in human urine using column-switching liquid chromatography–tandem mass spectrometry

We present a fast and reliable on-line clean-up HPLC-method for the simultaneous determination of the five major urinary metabolites of di-(2-ethylhexyl)phthalate (DEHP) namely mono-(2-ethyl-5-carboxypentyl)phthalate (5carboxy-MEPP), mono-[2-(carboxymethyl)hexyl]phthalate (2carboxy-MMHP), mono-(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono-(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP) and mono-(2-ethylhexyl)phthalate (MEHP). These metabolites represent about 70% of an oral DEHP dose. We for the first time succeeded to reliably quantify 5carboxy-MEPP and to identify 2carboxy-MMHP as major metabolites in native urines of the general population. The analytical procedure consists of an enzymatic hydrolysis, on-line extraction of the analytes from urinary matrix by a restricted access material column (RAM), back-flush transfer onto the analytical column (betasil phenylhexyl), detection by ESI-tandem mass spectrometry and quantification by isotope dilution (limit of detection (LOD) 0.25 microg/l). Median concentrations of a small collective taken from the general population (n=19) were 85.5 microg/l (5carboxy-MEPP), 47.5 microg/l (5OH-MEHP), 39.7 microg/l (5oxo-MEHP), 9.8 microg/l (MEHP) and about 37 microg/l (2carboxy-MMHP). The presented method can provide insights into the actual internal burden of the general population and certain risk groups. It will help to further explore the human metabolism of DEHP-an occupational and environmental toxicant of great concern.

Automated solid phase extraction and quantitative analysis of human milk for 13 phthalate metabolites

While the demonstrated benefits associated with breastfeeding are well recognized, breast milk is one possible route of exposure to environmental chemicals, including phthalates, by breastfeeding infants. Because of the potential health impact of phthalates to nursing children, determining whether phthalates are present in breast milk is important. We developed a sensitive method for measuring 13 phthalate metabolites in breast milk using automated solid phase extraction (SPE) coupled to isotope dilution-high-performance liquid chromatography (HPLC)-negative ion electrospray ionization-tandem mass spectrometry. We used D(4)-phthalate diesters to unequivocally establish the presence in human breast milk of enzymes capable of hydrolyzing the ubiquitous phthalate diesters to their respective monoesters. The analytical method involves acid-denaturation of the enzymes after collection of the milk to avoid hydrolysis of contaminant phthalate diesters introduced during sampling, storage, and analysis. The method shows good reproducibility (average coefficient of variations range between 4 and 27%) and accuracy (spiked recoveries are approximately 100%). The detection limits are in the low ng/ml range in 1ml of breast milk. We detected several phthalate metabolites in pooled human breast milk samples, suggesting that phthalates can be incorporated into breast milk and transferred to the nursing child.

Analysis of human urine for fifteen phthalate metabolites using automated solid-phase extraction

We improved our previous analytical method to measure phthalate metabolites in urine as biomarkers for phthalate exposure by automating the solid-phase extraction (SPE) procedure and expanding the analytical capability to quantify four additional metabolites: phthalic acid, mono-3-carboxypropyl phthalate, mono-isobutyl phthalate (miBP), and monomethyl isophthalate. The method, which involves automated SPE followed by isotope dilution-high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS), allows for the quantitative measurement of 15 phthalate metabolites in urine with detection limits in the low ng/ml range. SPE automation allowed for the unattended sequential extraction of up to 100 samples at a time, and resulted in an increased sample throughput, lower solvent use, and better reproducibility than the manual SPE. Furthermore, the modified method permitted for the first time, the separation and quantification of mono-n-butyl phthalate (mBP) and its structural isomer miBP. The method was validated on spiked pooled urine samples and on pooled urine samples from persons with no known exposure to phthalates.

Internal exposure of nursery-school children and their parents and teachers to di(2-ethylhexyl)phthalate (DEHP)

Di(2-ethylhexyl)phthalate (DEHP) is the main plasticizer for polyvinyl chloride (PVC) products. It has become widely spread in our environment and among people. DEHP is suspected to be responsible for endocrine-disruptor-like effects in mankind. Children are probably most susceptible to these endocrine effects. In this study we determined the internal exposure of nursery school children (aged 2-6 years) to DEHP and compared it to their parents' and teachers' exposure. The DEHP-metabolites mono(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP), mono(2-ethyl-5-oxo-hexyl)phthalate (5oxo-MEHP) and mono(2-ethylhexyl)phthalate (MEHP) were determined in first morning urine. The sum of the three DEHP metabolites in children's and in adults' urine was 90.0 and 59.1 micrograms/l respectively (median values; p = 0.074). Concentrations of the secondary metabolites 5OH-MEHP (median: 49.6 vs. 32.1 micrograms/l; p = 0.038) and 5oxo-MEHP (median: 33.8 vs. 19.6 micrograms/l; p = 0.015) were significantly higher in children than in adults. MEHP concentrations were low both in adults and children (median: 6.6 micrograms/l vs. 9.0 micrograms/l). Creatinine adjusted values should more accurately reflect the dose taken up with respect to body weight when comparing children with adults. Total creatinine adjusted DEHP metabolites in urine were significantly higher in children than in adults (median values: 98.8 vs. 50.9 micrograms/g creatinine; p < 0.0001). This also applied to the concentrations of both secondary metabolites 5OH-MEHP (55.8 vs. 28.1 micrograms/g creatinine; p < 0.0001) and 5oxo-MEHP (38.3 vs. 17.2 micrograms/g creatinine; p < 0.0001). Creatinine corrected concentrations for the monoester MEHP in children and adults were very similar (8.7 vs. 8.6 micrograms/g creatinine; p = 0.908). Based on the sum of the three determined metabolites we estimated the DEHP dose (in microgram/kg body-weight) taken up by children to be about twice as high as the dose taken up by adults. Routes of the ubiquitous exposure to DEHP remain indistinct. In children's urine the mean relative ratios of MEHP to 5OH-MEHP to 5oxo-MEHP were 1 to 7.1 to 4.9, in adults they were 1 to 3.4 to 2.1. This might indicate an enhanced oxidative metabolism in children. To date no information on the biological activity and toxicity of oxidative metabolites of DEHP is available. Since these are the major metabolites of DEHP toxicological data on these metabolites is urgently needed.

Internal exposure of the general population to DEHP and other phthalates--determination of secondary and primary phthalate monoester metabolites in urine

A number of phthalates and their metabolites are suspected of having teratogenic and endocrine disrupting effects. Especially the developmental and reproductive effects of di(2-ethylhexyl)phthalate (DEHP) are under scrutiny. In this study we determined the concentrations of the secondary, chain oxidized monoester metabolites of DEHP, mono(2-ethyl-5-hydroxyhexyl)phthalate (5OH-MEHP) and mono(2-ethyl-5-oxo-hexyl)phthalate (5oxo-MEHP) in urine samples from the general population. The utilization of the secondary metabolites minimized any risk of contamination by the ubiquitously present phthalate parent compounds. Included in the method were also the simple monoester metabolites of DEHP, dioctylphthalate (DOP), di-n-butylphthalate (DnBuP), butylbenzylphthalate (BBzP) and diethylphthalate (DEP). Automated sample preparation was performed applying a column switching liquid chromatography system enabling online extraction of the urine on a restricted access material (RAM) and separation on a reversed phase analytical column. Detection was performed by negative ESI-tandem mass spectrometry in multiple reaction monitoring mode and quantification by isotope dilution. The excretion of DEHP and the other phthalates was studied by analyzing first morning urine samples from 53 women and 32 men aged 7-64 years (median: 34.2 years) living in northern Bavaria (Germany) who were not occupationally exposed to phthalates. Phthalate metabolites, secondary and primary ones, were detected in all specimens. Concentrations were found to vary strongly from phthalate to phthalate and subject to subject with differences spanning more than three orders of magnitude. Median concentrations for excretion of DEHP metabolites were 46.8 microg/L for 5OH-MEHP (range 0.5-818 microg/L), 36.5 microg/L for 5oxo-MEHP (range 0.5-544 microg/L), and 10.3 microg/L for MEHP (range:<0.5 (limit of quantification, LOQ) to 177 microg/L). A strong correlation was found between the excretion of 5OH-MEHP and 5oxo-MEHP with a correlation coefficient of r=0.991, indicating close metabolic proximity of those two parameters but also the absence of any contaminating interference. Median concentrations for the other monoester metabolites were for mono-n-butylphthalate (MnBuP) 181 microg/L, for monobenzylphthalate (MBzP) 21.0 microg/L, for monoethylphthalate (MEP) 90.2 microg/L and for mono-n-octylphthalate (MOP)<1.0 microg/L (LOQ). These results will help to perform health risk assessments for the phthalate exposure of the general population.