We present an assay which employs enzyme digestion and solid phase extraction followed by liquid chromatography–tandem mass spectrometry to simultaneously quantify 16 hydroxylated polycyclic aromatic ...hydrocarbons (OHPAHs) in 3-ml samples of urine. The analytes consisted of 2-, 3-, and 4-ring OHPAHs, namely, 1- and 2-hydroxynaphthalene (1- and 2-OHNAP), 2-hydroxyfluorine (2-OHFLU), 1-, 2-, 3-, 4-, and 9-hydroxyphenanthrene (1-, 2-, 3-, 4-, and 9-OHPHE), 1-hydroxypyrene (1-OHPYR), 1- and 2-hydroxybenzo(
a)anthracene (1- and 2-OHBAA), 3- and 6-hydroxychrysene (3- and 6-OHCHR) and 3-, 7-, and 9-hydroxybenzo(
a)pyrene (3-, 7-, and 9-OHBAP). The method was validated using urine samples from steel workers and control subjects. The coefficients of variation of the method for the particular analytes were between 7% and 27% and the limits of quantitation were between 0.002 and 0.010
μg/l urine. The 2- and 3-ring OHPAHs were easily quantified in all subjects. However, 1-OHPYR was the only representative of the 4- and 5-ring metabolites that could be quantified. Pairwise correlations showed that all OHPAHs were highly correlated with each other (0.553
≤
r
≤
0.910) and with 1-OHPYR (0.614
≤
r
≤
0.910), the metabolite most widely accepted as a short-term biomarker of exposure to PAHs. The analyte, 2-OHNAP exhibited the lowest pairwise correlations with the other OHPAHs (0.542
≤
r
≤
0.628), presumably due to confounding by smoking. Metabolites of phenanthrene, an abundant PAH and the smallest to possess a bay region, are promising OHPAHs for characterizing both exposures to PAHs and the various metabolic pathways.
Ginkgo biloba
extract (GbE) is a dietary supplement derived from an ethanolic extract of
Ginkgo biloba
leaves. Unfinished bulk GbE is used to make finished products that are sold as dietary ...supplements. The variable, complex composition of GbE makes it difficult to obtain consistent toxicological assessments of potential risk. The National Toxicology Program (NTP) observed hepatotoxicity in its rodent studies of a commercially available, unfinished GbE product, but the application of these results to the broader GbE supplement market is unclear. Here, we use a combination of non-targeted and targeted chromatographic and spectrophotometric methods to obtain profiles of 24 commercially available finished GbE products and unfinished standardized and unstandardized extracts with and without hydrolysis, then used principal component analysis to group unfinished products according to their similarity to each other and to National Institute of Standards and Technology (NIST) standard reference materials (SRM), and the finished products. Unfinished products were grouped into those that were characteristic and uncharacteristic of standardized GbE. Our work demonstrates that different analytical approaches produced similar classifications of characteristic and uncharacteristic products in unhydrolyzed samples, but the distinctions largely disappeared once the samples were hydrolyzed. Using our approach, the NTP GbE was most similar to two unfinished GbE products classified as characteristic, finished products, and the NIST GbE SRM. We propose that a simple analysis for the presence, absence, or amounts of compounds unique to GbE in unhydrolyzed samples could be sufficient to determine a sample’s authenticity.
Graphical abstract
Benzene is known to have toxic effects on the blood and bone marrow, but its impact at levels below the U.S. occupational standard of 1 part per million (ppm) remains uncertain. In a study of 250 ...workers exposed to benzene, white blood cell and platelet counts were significantly lower than in 140 controls, even for exposure below 1 ppm in air. Progenitor cell colony formation significantly declined with increasing benzene exposure and was more sensitive to the effects of benzene than was the number of mature blood cells. Two genetic variants in key metabolizing enzymes, myeloperoxidase and NAD(P)H:quinone oxidoreductase, influenced susceptibility to benzene hematotoxicity. Thus, hematotoxicity from exposure to benzene occurred at air levels of 1 ppm or less and may be particularly evident among genetically susceptible subpopulations.
Tris(chloropropyl) phosphate (TCPP) is an organophosphorus flame retardant and plasticizer used in manufacturing and multiple consumer products. Commercial TCPP is a ubiquitous environmental ...contaminant and TCPP or its metabolites have been detected in human plasma and urine. In response to the demonstrated widespread human exposure and lack of toxicity data, the Division of the National Toxicology Program is investigating the chronic toxicity of TCPP following perinatal exposure in HSD:Sprague Dawley®SD® (HSD) rats (up to 20,000 ppm) and adult exposure in B6C3F1/N mice (females, up to 10,000 ppm; males up to 5000 ppm) to TCPP via feed. Systemic exposure and bioaccumulation were assessed by measuring plasma concentrations of tris(1-chloro-2-propyl)phosphate (TCIPP), the most abundant TCPP isomer. TCIPP concentrations in TCPP-exposed rats and mice ranged from 3.43 to 1180 ng/mL and increased with exposure concentration at all time points. No sex differences were observed in rats, but male mice had higher TCIPP concentrations than females. TCIPP did not bioaccumulate in rats or mice over the course of the study. Low TCIPP concentrations were seen in some control rats and mice that were attributed to background TCPP present during sample collection, preparation and/or analysis. Bis(2-chloroisopropyl) 1-carboxyethyl phosphate (BCPCP), a TCPP metabolite, was quantified in plasma from control and selected exposed animals. Results showed increases in BCPCP concentration that were proportional to exposure concentration in rats and mice at concentrations much higher than TCIPP, indicating that BCPCP might be a more suitable biomarker of TCPP exposure.
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•Tris(chloropropyl)phosphate (TCPP) has widespread environmental exposure.•We measured plasma levels of TCPP following chronic feed exposure in rodents.•The most abundant isomer of TCPP (TCIPP) increased with exposure with no accumulation.•Bis(2-chloroisopropyl)1-carboxyethyl phosphate (BCPCP) levels were higher than TCIPP.•Metabolite BCPCP may be a more suitable biomarker for TCPP exposure.
Thallium is a heavy metal that is known to induce a broad spectrum of adverse health effects in humans including alopecia, neurotoxicity, and mortality following high dose acute poisoning events. ...Widespread human exposure to thallium may occur via consumption of contaminated drinking water; limited toxicity data are available to evaluate the corresponding public health risk. To address this data gap, the Division of Translational Toxicology conducted short-term toxicity studies of a monovalent thallium salt, thallium (I) sulfate. Thallium (I) sulfate was administered via dosed drinking water to time-mated Sprague Dawley (Hsd:Sprague Dawley® SD®) rats (F0 dams) and their offspring (F1) from gestation day (GD) 6 until up to postnatal day (PND) 28 at concentrations of 0, 3.13, 6.25, 12.5, 25, or 50 mg/L, and adult male and female B6C3F1/N mice for up to 2 weeks at concentrations of 0, 6.25, 12.5, 25, 50, or 100 mg/L. Rat dams in the 50 mg/L exposure group were removed during gestation, and dams and offspring in the 25 mg/L exposure group were removed on or before PND 0 due to overt toxicity. Exposure to thallium (I) sulfate at concentrations ≤ 12.5 mg/L did not impact F0 dam body weights, maintenance of pregnancy, littering parameters, or F1 survival (PND 4–28). However, in F1 pups, exposure to 12.5 mg/L thallium (I) sulfate resulted in decreased body weight gains relative to control rats and onset of whole-body alopecia. Measurement of thallium concentrations in dam plasma, amniotic fluid, fetuses (GD 18), and pup plasma (PND 4) indicated marked maternal transfer of thallium to offspring during gestation and lactation. Mice exposed to 100 mg/L thallium (I) sulfate were removed early due to overt toxicity, and mice exposed to ≥ 25 mg/L exhibited exposure concentration-related decreases in body weight. Lowest-observed-effect levels of 12.5 mg/L (rats) and 25 mg/L (mice) were determined based on the increased incidence of clinical signs of alopecia in F1 rat pups and significantly decreased body weights for both rats and mice.
•Exposure to thallium (I) sulfate results in decreased body weight in rats and mice.•Thallium (I) sulfate exposure induces whole-body alopecia in rats, but not mice.•Identified LOELs were 12.5 mg/L (rats) and 25 mg/L (mice).•These data will aid in evaluating the potential health risk of thallium (I) sulfate.
We used natural spline (NS) models to investigate nonlinear relationships between levels of benzene metabolites (E,E-muconic acid, S-phenylmercapturic acid, phenol, hydroquinone, and catechol) and ...benzene exposure among 386 exposed and control workers in Tianjin, China. After adjusting for background levels (estimated from the 60 control subjects with the lowest benzene exposures), expected mean trends of all metabolite levels increased with benzene air concentrations from 0.03 to 88.9 ppm. Molar fractions for phenol, hydroquinone, and E,E-muconic acid changed continuously with increasing air concentrations, suggesting that competing CYP-mediated metabolic pathways favored E,E-muconic acid and hydroquinone below 20 ppm and favored phenol above 20 ppm. Mean trends of dose-specific levels (micromol/L/ppm benzene) of E,E-muconic acid, phenol, hydroquinone, and catechol all decreased with increasing benzene exposure, with an overall 9-fold reduction of total metabolites. Surprisingly, about 90% of the reductions in dose-specific levels occurred below about 3 ppm for each major metabolite. Using generalized linear models with NS-smoothing functions (GLM + NS models), we detected significant effects upon metabolite levels of gender, age, and smoking status. Metabolite levels were about 20% higher in females and decreased between 1% and 2% per year of life. In addition, levels of hydroquinone and catechol were greater in smoking subjects. Overall, our results indicate that benzene metabolism is highly nonlinear with increasing benzene exposure above 0.03 ppm, and that current human toxicokinetic models do not accurately predict benzene metabolism below 3 ppm. Our results also suggest that GLM + NS models are ideal for evaluating nonlinear relationships between environmental exposures and levels of human biomarkers.
Although the toxicity of benzene has been linked to its metabolism, the dose-related production of metabolites is not well understood in humans, particularly at low levels of exposure. We ...investigated unmetabolized benzene in urine (UBz) and all major urinary metabolites phenol (PH), E,E-muconic acid (MA), hydroquinone (HQ) and catechol (CA) as well as the minor metabolite, S-phenylmercapturic acid (SPMA), in 250 benzene-exposed workers and 139 control workers in Tianjin, China. Median levels of benzene exposure were ∼1.2 p.p.m. for exposed workers (interquartile range: 0.53–3.34 p.p.m.) and 0.004 p.p.m. for control workers (interquartile range: 0.002–0.007 p.p.m.). (Exposures of control workers to benzene were predicted from levels of benzene in their urine.) Metabolite production was investigated among groups of 30 workers aggregated by their benzene exposures. We found that the urine concentration of each metabolite was consistently elevated when the group's median benzene exposure was at or above the following air concentrations: 0.2 p.p.m. for MA and SPMA, 0.5 p.p.m. for PH and HQ, and 2 p.p.m. for CA. Dose-related production of the four major metabolites and total metabolites (μmol/l/p.p.m. benzene) declined between 2.5 and 26-fold as group median benzene exposures increased between 0.027 and 15.4 p.p.m. Reductions in metabolite production were most pronounced for CA and PH <1 p.p.m., indicating that metabolism favored production of the toxic metabolites, HQ and MA, at low exposures.
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