Urinary levels of seven phthalate metabolites in the U.S. population from the National Health and Nutrition Examination Survey (NHANES) 1999-2000

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.

Temporal variability of urinary phthalate metabolite levels in men of reproductive age

Phthalates are a family of multifunctional chemicals widely used in personal care and other consumer products. The ubiquitous use of phthalates results in human exposure through multiple sources and routes, including dietary ingestion, dermal absorption, inhalation, and parenteral exposure from medical devices containing phthalates. We explored the temporal variability over 3 months in urinary phthalate metabolite levels among 11 men who collected up to nine urine samples each during this time period. Eight phthalate metabolites were measured by solid-phase extraction-high-performance liquid chromatography-tandem mass spectrometry. Statistical analyses were performed to determine the between- and within-subject variance apportionment, and the sensitivity and specificity of a single urine sample to classify a subject's 3-month average exposure. Five of the eight phthalates were frequently detected. Monoethyl phthalate (MEP) was detected in 100% of samples; monobutyl phthalate, monobenzyl phthalate, mono-2-ethylhexyl phthalate (MEHP), and monomethyl phthalate were detected in > 90% of samples. Although we found both substantial day-to-day and month-to-month variability in each individual's urinary phthalate metabolite levels, a single urine sample was moderately predictive of each subject's exposure over 3 months. The sensitivities ranged from 0.56 to 0.74. Both the degree of between- and within-subject variance and the predictive ability of a single urine sample differed among phthalate metabolites. In particular, a single urine sample was most predictive for MEP and least predictive for MEHP. These results suggest that the most efficient exposure assessment strategy for a particular study may depend on the phthalates of interest.

Diverse developmental toxicity of di-n-butyl phthalate in both sexes of rat offspring after maternal exposure during the period from late gestation through lactation

To evaluate developmental toxicity of di-n-butyl phthalate (DBP) with exposure during the period from late gestation to following lactation, maternal rats were given DBP at dietary concentrations of 0, 20, 200, 2000 and 10,000 ppm from gestational day 15 to postnatal day (PND) 21. At 10,000 ppm, male offspring showed a decreased neonatal anogenital distance and retention of nipples (PND 14), while females showed a slight non-significant delay in the onset of puberty. At PND 21, reduction of testicular spermatocyte development was evident from 20 ppm, as well as mammary gland changes at low incidence in both sexes. At this time point, population changes of pituitary hormone-immunoreactive cells were observed at 10,000 ppm with a similar pattern of increase in the percentages of luteinizing hormone (LH)-positive and decrease in follicle-stimulating hormone (FSH) and prolactin producing cells in both sexes, effects also being evident on FSH from 200 ppm and LH from 2000 ppm in females. During postnatal week (PNW) 8-11, marginal increase of the number of cases with extended diestrus was found at 10,000 ppm. At adult stage necropsy, testicular lesions appeared to be very faint in most cases, but degeneration and atrophy of mammary gland alveoli were observed in males from 20 ppm. Although without clear monotonic dose-dependence, relative pituitary weights were increased with the intermediate doses in males at PNW 11. In females, relative pituitary weights were decreased after 10,000 ppm at PNW 11, and from 200 ppm at PNW 20. The proportion of FSH-positive cells in the pituitaries at PNW 11 was increased in both sexes at 10,000 ppm. Thus, developmental exposure to DBP affected female sexual development involving pituitary function, while in males testicular toxicity was mostly reversible but mammary gland toxicity was persistent at a dose level as low as 20 ppm.

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.

Exposure to di-(2-ethylhexyl) phthalate among premature neonates in a neonatal intensive care unit

OBJECTIVE

Premature neonates who spend time in a neonatal intensive care unit may be at increased risk of adverse health effects from exposure to di-(2-ethylhexyl) phthalate (DEHP) because of their increased risk of high exposure, their small body size, and their physical condition. DEHP, a reproductive toxicant in animals, is a major component in polyvinyl chloride (PVC) plastics, which are frequently used in medical tubing and blood storage bags. DEHP is not covalently bound to PVC, and it may be easily released from the PVC medical devices. The objective of this study was to determine whether premature infants who undergo medical procedures, such as blood transfusions, intravenous therapy, enteral and parenteral nutrition support, and dialysis, are at increased risk of exposure to DEHP than the general population. Because of their smaller size, children and especially premature and small infants may receive a larger dose of DEHP on a milligram per kilogram basis than adults when the same-size medical device is used for all ages.

METHODS

Premature neonates who seemed to have the potential to be on intravenous infusion for >2 weeks and were expected to survive were eligible for enrollment in the study. We assessed exposure to DEHP in 6 premature newborns by measuring in 41 urine samples the levels of 3 DEHP metabolites: mono-(2-ethylhexyl) phthalate (mEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP), and mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP).

RESULTS

mEHHP and mEOHP were detected in all 41 urine samples, and mEHP was detected in 33. Because only 33 of the samples had detectable amounts for all 3 metabolites, statistical analyses were limited to those 33. The levels of all 3 DEHP metabolites varied widely, and the urinary mean and median concentrations of mEOHP and mEHHP were 1 order of magnitude higher than those for mEHP. Furthermore, the geometric mean urinary concentrations of mEOHP (1617 ng/mL), mEHHP (2003 ng/mL), and mEHP (100 ng/mL) in these 6 premature infants who underwent intensive therapeutic interventions were found to be severalfold higher than in the US general population (for mEHP, geometric mean in those 6 years and older was 3.43 ng/mL).

CONCLUSIONS

This study provides the first quantitative evidence confirming that newborns who undergo intensive therapeutic medical interventions are exposed to higher concentrations of DEHP than the general population. Although the overall benefits of medical procedures using PVC devices outweigh the risks associated with exposure to DEHP, more research is needed to determine whether infants and children who undergo intensive therapeutic interventions using DEHP-containing devices are at higher risk for altered health outcomes than infants and children who undergo similar treatments but are not potentially exposed to DEHP.