Echinacea is commonly used as a dietary supplement owing to its putative anti-inflammatory, antiviral, and antibacterial activities. Unfortunately, determining risk posed to human health is challenging. A novel combination of chemical and biological characterization was employed for selection of a representative extract sample used for in vivo investigation of the immunomodulatory properties of Echinacea (E.) purpurea. In vitro cytokine profiling showed the extract could stimulate pro-inflammatory cytokine production in the absence of detectable endotoxin. An in-depth in vivo evaluation of the immune response following a 28-day oral exposure to the selected E. purpurea extract was conducted in adult Harlan Sprague Dawley (HSD) female rats at doses up to 2000 mg/kg/day. There was no evidence that E. purpurea caused overt toxicity or effects on humoral immunity. However, cell-mediated immunity was increased but only at low doses and with no evidence of a dose-response. In addition, E. purpurea treatment enhanced natural killer cell activity and the relative percentage of macrophages/monocytes in the spleen of rats from the highest treatment group. These results suggest that E. purpurea may have immunomodulatory properties that support antiviral and antibacterial activity but may also foster an immunostimulatory environment that could exacerbate some immune-mediated conditions.

Xylenes are ubiquitous in the environment due to their widespread use in a variety of products and industries, including cleaning agents, paint thinners, printing, and plastic production, demonstrating the potential for exposure in humans. Because of limited data on xylenes, we are investigating the toxicity of xylenes, mixed in a specific isomeric ratio, in rodent models. The goal of this study was to develop and validate a method to quantitate individual xylene isomers (p-, m-, and o-xylene) in rodent blood in support of toxicity studies. The method used internal standard calibration with isotopically labeled analytes for an analysis by headspace gas chromatography-mass spectrometry following removal of moisture with anhydrous calcium chloride to allow separation of individual isomers. In male Sprague Dawley rat blood, the method was linear (r ≥ 0.99) over the range of 5 - 1500 ng/mL, accurate (mean relative error (RE) ≤ 15.3%), and precise (relative standard deviation (RSD) ≤ 10.8%). Low limits of detection were achieved, at 1.0, 2.3, and 1.0 ng/mL for p-, m-, and o-xylene, respectively. The method was evaluated in male and female Hsd:Sprague Dawley® SD® rat blood and male and female B6C3F1/N mouse blood, the strains used in toxicology studies, with RE ≤ ±13.5% and RSD ≤ 10.6%. All isomers were stable for at least 62 days in blood when stored frozen. The results presented here demonstrate this method can accurately and precisely quantitate p-, m-, and o-xylene in a single analytical run in rat and mice blood samples following exposure to individual xylene isomers. The method could be easily adapted to other biological matrices, including human matrices.

The ability of polycyclic aromatic compounds (PACs), most notably benzo(a) pyrene [B(a)P], to suppress antibody responses in experimental animals is well documented. Very little information, however, is available on the immunotoxicity of related PACs despite their widespread presence in the environment. Additionally, there are several weaknesses in existing immunotoxicity databases for PACs in experimental animals, limiting their applicability in quantitative risk assessment. Careful characterization of strong positive and clear negative PACs is needed in order to lay the foundation for generating robust immunotoxicity data for structurally diverse PACs that have not yet been evaluated. In the current study, adult B6C3F1/N female mice were treated daily for 28 consecutive days by oral administration of B(a)P to provide dose levels ranging between 2 and 150 mg/kg bodyweight/day. In addition, phenanthrene and pyrene, non-carcinogenic PACs, were tested at dose ranges between 12.5 and 800 mg/kg bodyweight/day and 3.1 and 200 mg/kg bodyweight/day, respectively. Immune assessments following PAC exposure included organ weights and immunopathology, hematology, quantification of immune cell types in the spleen, and T-dependent antibody response (TDAR) to sheep red blood cells (SRBC). Benzo(a)pyrene exposure resulted in significant decreases in lymphoid organ weights, immune cell populations in the spleen and TDAR. The most sensitive indicator for immunotoxicity from B(a)P treatment was suppression of antibody responses, where an ∼75% decrease occurred at a dose level of 9 mg/kg bodyweight/day and ∼32% decrease at the lowest tested dose of 2 mg/kg bodyweight/day. Antibody suppression was associated with significant immune cell loss in the spleen; however, it was clear that the suppression of the TDAR was more sensitive than cell loss indicating that cell function impairments were involved. Phenanthrene treatment also resulted in suppression of the antibody response but only at dose levels ≥50 mg/kg bodyweight/day without significant effects on other parameters, while pyrene showed no significant immune effects. Suppression of the TDAR to SRBC immunization was the most sensitive immune endpoint being 33 times more sensitive than changes in liver weight, a commonly used outcome for risk assessment for PACs. Benzo(a)pyrene was the most potent PAC regarding suppression of humoral immunity whereas pyrene did not affect the immune responses tested. These studies lay the foundation for evaluating diverse PACs with a range of immunotoxicological potencies.

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of anthropogenic chemicals, and their widespread use in manufacturing and commerce has led to introduction of these chemicals into the environment. Owing to the lack of traditional toxicology data on the majority of PFAS, novel testing methods that provide supporting information to inform human health impacts in a relatively short time frame will be increasingly important. The US Environmental Protection Agency's (EPA) Transcriptomic Assessment Process (ETAP) was recently implemented by the Agency as an efficient and cost-effective method to begin assessing potential human health impacts of chemicals that lack traditional toxicity testing data. The method involves short-term oral dosing in male and female adult rats over a five-day interval, followed by transcriptomic dose-response assessment in twelve tissues to determine a point of departure. The ETAP point of departure identifies the dose at which there are no coordinated transcriptional changes that would indicate a potential toxicity of concern. However, this approach does not explore any specific association with hazard or mechanism. Reported here are ETAP results for three PFAS chemicals: 3:3 fluorotelomer carboxylic acid (3:3 FTCA), 7:3 fluorotelomer alcohol (7:3 FTOH), and perfluorohexanesulfonamide (PFHxSA). The transcriptomic points of departure associated with the tested chemicals, as assessed via ETAP and allometrically scaled to human equivalent doses, were 0.00235 (3:3 FTCA), 0.0152 (7:3 FTOH), and 0.00358 (PFHxSA) mg/kg-day.

The US Environmental Protection Agency (US EPA) and other regulatory agencies routinely assess whether certain chemical exposures might result in harmful health effects. Traditional human health assessments rely upon expert judgment of dose-effect linkages observed in animal toxicology or human studies. Because both collection of toxicology data and synthesis of information might take multiple years to complete, there are relatively few available assessments for decision-making. Identifying methods that yield significant time and resource efficiencies to the process will have scalable public health benefits. To address the need, US EPA developed the database-calibrated assessment process (DCAP) to generate oral, non-cancer human health toxicity values that builds on previously published approaches and guidance. The approach uses the US EPA Toxicity Values Database (ToxValDB) that contains dose-response summary values (DRSVs) from in vivo toxicity studies. The DRSVs are converted to an oral, chronic, human equivalent dose using a series of standard conversion factors. A point-of-departure (POD) is then calculated across a distribution of studies for a given chemical using a calibration percentile that is benchmarked to critical effect PODs from published human health assessments. Traditional and process-specific uncertainties are incorporated to derive a calibrated toxicity value (CTV), defined as an estimate of a daily oral dose to the human population that is likely to be without appreciable risk of adverse non-cancer health effects over a lifetime. This review presents the rationale and methods for the approach, resulting in reporting of 1001 CTVs for chemicals that currently lack a human health assessment.

Increases in botanical use, encompassing herbal medicines and dietary supplements, have underlined a critical need for an advancement in safety assessment methodologies. However, botanicals present unique challenges for safety assessment due to their complex and variable composition arising from diverse growing conditions, processing methods, and plant varieties. Historically, botanicals have been largely evaluated based on their history of use information, based primarily on traditional use or dietary history. However, this presumption lacks comprehensive toxicological evaluation, demanding innovative and consistent assessment strategies. To address these challenges, the Botanical Safety Consortium (BSC) was formed as an international, cross-sector forum of experts to identify fit-for purpose assays that can be used to evaluate botanical safety. This global effort aims to assess botanical safety assessment methodologies, merging traditional knowledge with modern in vitro and in silico assays. The ultimate goal is to champion the development of toxicity tools for botanicals. This manuscript highlights: 1) BSC's strategy for botanical selection, sourcing, and preparation of extracts to be used in in vitro assays, and 2) the approach utilized to characterize botanical extracts, using green tea and Asian ginseng as examples, to build confidence for use in biological assays.

N-butylbenzenesulfonamide (NBBS) is a high-production volume plasticizer that is an emerging contaminant of concern for environmental and human health. To understand the risks and health effects of exposure to NBBS, studies were conducted in adult-exposed mice and developmentally exposed rats to evaluate the potential for NBBS to modulate the immune system. Beginning between 8 and 9 weeks of age, dosed feed containing NBBS at concentrations of 0, 313, 625, 1250, 2500, and 5000 ppm was continuously provided to B6C3F1/N female mice for 28 days. Dosed feed was also continuously provided to time-mated Harlan Sprague Dawley (Sprague Dawley SD) rats at concentrations of 0-, 250-, 500-, and 1000-ppm NBBS from gestation day 6 to postnatal day 28 and in F1 rats until 11-14 weeks of age. Functional assessments of innate, humoral, and cell-mediated immunity were conducted in adult female mice and F1 rats following exposure to NBBS. In female mice, NBBS treatment suppressed the antibody-forming cell (AFC) response to SRBC with small increases in T-cell responses and natural killer (NK)-cell activity. In developmentally exposed rats, NBBS treatment-related immune effects were sex dependent. A positive trend in NK-cell activity occurred in male F1 rats while a negative trend occurred in female F1 rats. The AFC response to SRBC was decreased in female F1 rats but not in male F1 rats. These data provide evidence that oral exposure to NBBS has the potential to produce immunomodulatory effects on both innate and adaptive immune responses, and these effects appear to have some dependence on species, sex, and period of exposure (developmental vs adult).

Glyphosate, the most heavily used herbicide world-wide, is applied to plants in complex formulations that promote absorption. The National Toxicology Program reported in 1992 that glyphosate, administered to rats and mice at doses up to 50,000 ppm in feed for 13 weeks, showed little evidence of toxicity, and no induction of micronuclei was observed in the mice in this study. Subsequently, mechanistic studies of glyphosate and glyphosate-based formulations (GBFs) that have focused on DNA damage and oxidative stress suggest that glyphosate may have genotoxic potential. However, few of these studies directly compared glyphosate to GBFs, or effects among GBFs. To address these data gaps, we tested glyphosate, glyphosate isopropylamine (IPA), and (aminomethyl)phosphonic acid (AMPA, a microbial metabolite of glyphosate), 9 high-use agricultural GBFs, 4 residential-use GBFs, and additional herbicides (metolachlor, mesotrione, and diquat dibromide) present in some of the GBFs in bacterial mutagenicity tests, and in human TK6 cells using a micronucleus assay and a multiplexed DNA damage assay. Our results showed no genotoxicity or notable cytotoxicity for glyphosate or AMPA at concentrations up to 10 mM, while all GBFs and herbicides other than glyphosate were cytotoxic, and some showed genotoxic activity. An in vitro to in vivo extrapolation of results for glyphosate suggests that it is of low toxicological concern for humans. In conclusion, these results demonstrate a lack of genotoxicity for glyphosate, consistent with observations in the NTP in vivo study, and suggest that toxicity associated with GBFs may be related to other components of these formulations.

Abstract Cookstove emissions are a significant source of indoor air pollution in developing countries and rural communities world-wide. Considering that many research sites for evaluating cookstove emissions and interventions are remote and require potentially lengthy periods of particulate matter (PM) filter sample storage in sub-optimal conditions (e.g., lack of cold storage), an important question is whether samples collected in the field are stable over time. To investigate this, red oak was burned in a natural-draft stove, and fine PM (PM2.5) was collected on polytetrafluoroethylene filters. Filters were stored at either ambient temperature or more optimal conditions (−20 °C or −80 °C) for up to 3 months and extracted. The effects of storage temperature and length on stability were evaluated for measurements of extractable organic matter (EOM), PM2.5, and polycyclic aromatic compound (PAC) levels in the filter extracts. A parallel, controlled laboratory condition was also evaluated to further explore sources of variability. In general, PM2.5 and EOM in both simulated field and laboratory samples were similar regardless of the storage condition or duration. The extracts were also analyzed by gas chromatography to quantify 22 PACs and determine similarities and/or differences between the conditions. PAC levels were a more sensitive stability measure in differentiating between storage conditions. The findings suggest that measurements are relatively consistent across storage duration/temperatures for filter samples with relatively low EOM levels. This study aims to inform protocols and filter storage procedures for exposure and intervention research conducted in low- and middle-income countries where studies may be budget- and infrastructure-limited.

Black cohosh (BC; Actaea racemosa L.), a top‐selling botanical dietary supplement, is marketed to women primarily to ameliorate a variety of gynecological symptoms. Due to widespread usage, limited safety information, and sporadic reports of hepatotoxicity, the Division of the National Toxicology Program (DNTP) initially evaluated BC extract in female rats and mice. Following administration of up to 1000 mg/kg/day BC extract by gavage for 90 days, dose‐related increases in micronucleated peripheral blood erythrocytes were observed, along with a nonregenerative macrocytic anemia resembling megaloblastic anemia in humans. Because both micronuclei and megaloblastic anemia may signal disruption of folate metabolism, and inadequate folate levels in early pregnancy can adversely affect neurodevelopment, the DNTP conducted a pilot cross‐sectional study comparing erythrocyte micronucleus frequencies, folate and B12 levels, and a variety of hematological and clinical chemistry parameters between women who used BC and BC‐naïve women. Twenty‐three women were enrolled in the BC‐exposed group and 28 in the BC‐naïve group. Use of any brand of BC‐only supplement for at least 3 months was required for inclusion in the BC‐exposed group. Supplements were analyzed for chemical composition to allow cross‐product comparisons. All participants were healthy, with no known exposures (e.g., x‐rays, certain medications) that could influence study endpoints. Findings revealed no increased micronucleus frequencies and no hematological abnormalities in women who used BC supplements. Although reassuring, a larger, prospective study with fewer confounders (e.g., BC product diversity and duration of use) providing greater power to detect subtle effects would increase confidence in these findings.

Tris(4-chlorophenyl)methane (TCPMe) is a byproduct of dichlorodiphenyltrichloroethane synthesis. TCPMe and its metabolite tris(4-chlorophenyl)methanol (TCPMOH) are environmentally prevalent and have been detected in wildlife and humans. Due to inadequate data addressing its toxicity, the National Toxicology Program (NTP) is testing TCPMe in Hsd:Sprague Dawley SD (HSD) rats following perinatal exposure. In support of the toxicology studies, a gas chromatography - mass spectrometry (GC-MS) method was validated to simultaneously quantitate TCPMe and TCPMOH in male Sprague Dawley rat plasma (primary matrix) over calibration standard ranges of 2-200 ng/mL and 1-100 ng/mL, respectively. The method was linear (r(2) >= 0.9975), accurate (relative error (RE) <= +/- 12.8 (TCPMe) and +/- 14.5% (TCPMOH), and precise (relative standard deviation (RSD) <= 7.6 (TCPMe) and 3.8% (TCPMOH)). The limits of quantitation were 2 and 1 ng/mL and the limits of detection were 0.73 and 0.07 ng/mL for TCPMe and TCPMOH, respectively. Samples, as high as 2000 ng/mL for TCPMe (RSD <= 3.9, RE <= +/- 1.0) and 1000 ng/mL for TCPMOH (RSD <= 1.0, RE <= +/- 2.9), were successfully diluted with plasma into the validated concentration range. The method was selective and both TCPMe and TCPMOH were quantified in all secondary matrices (HSD male and female plasma, gestation day (GD)18 plasma, amniotic fluid, and fetus, postnatal day (PND)4 dam and pup plasma) using a primary matrix curve (RE <= +/- 14.4% and 11.5; RSD <= 7.6 and 11.8%, respectively). These results demonstrate that the method is suitable for simultaneous quantitation of TCPMe and TCPMOH in rodent plasma and fetuses for the evaluation of gestational and lactational transfer following perinatal exposure of TCPMe in NTP studies.

Black cohosh (Actaea racemosa L.) is a botanical supplement marketed to women of all ages. Due to paucity of data to assess the safe use, the National Toxicology Program (NTP) is evaluating the toxicity of black cohosh. The use of an authentic, quality material is imperative to generate robust data. Because botanical materials are complex mixtures with variable composition, the selection of a material is challenging. We describe selection and phytochemical characterization of an unformulated black cohosh root extract (i.e., an extract that serves as source material for a formulated product) to be used in the NTP assessments. A material was selected using a combination of non-targeted and targeted chemical analyses, including confirmation of authenticity, absence of contaminants and adulterants, and similarity to a popular black cohosh product used by consumers. Thirty-nine constituents covering three major classes, triterpene glycosides, phenolic acids, and alkaloids were identified. Among constituents quantified, triterpene glycosides made up approximately 4.7% (w/w) with total constituents quantified making up 5.8% (w/w) of the extract. Non-targeted chemical analysis followed by chemometric analysis of various materials sold as black cohosh, and reference materials for black cohosh and other Actaea species further confirmed the suitability of the selected extract for use.

Black cohosh (BC; Actaea racemosa L.), a top-selling botanical dietary supplement, is marketed to women primarily to ameliorate a variety of gynecological symptoms. Due to widespread usage, limited safety information, and sporadic reports of hepatotoxicity, the Division of the National Toxicology Program (DNTP) initially evaluated BC extract in female rats and mice. Following administration of up to 1000 mg/kg/day BC extract by gavage for 90 days, dose-related increases in micronucleated peripheral blood erythrocytes were observed, along with a nonregenerative macrocytic anemia resembling megaloblastic anemia in humans. Because both micronuclei and megaloblastic anemia may signal disruption of folate metabolism, and inadequate folate levels in early pregnancy can adversely affect neurodevelopment, the DNTP conducted a pilot cross-sectional study comparing erythrocyte micronucleus frequencies, folate and B12 levels, and a variety of hematological and clinical chemistry parameters between women who used BC and BC-naïve women. Twenty-three women were enrolled in the BC-exposed group and 28 in the BC-naïve group. Use of any brand of BC-only supplement for at least 3 months was required for inclusion in the BC-exposed group. Supplements were analyzed for chemical composition to allow cross-product comparisons. All participants were healthy, with no known exposures (e.g., x-rays, certain medications) that could influence study endpoints. Findings revealed no increased micronucleus frequencies and no hematological abnormalities in women who used BC supplements. Although reassuring, a larger, prospective study with fewer confounders (e.g., BC product diversity and duration of use) providing greater power to detect subtle effects would increase confidence in these findings.

Objective Ethyltoluenes are isolated during crude oil refinement for use in gasoline and commercial products and are ubiquitous in the environment. However, minimal toxicity data are available. Previously, we identified 2-ethyltoluene (2-ET) as the most potent isomer via nose-only inhalation exposure in rodents. Here, we expanded the hazard characterization of 2-ET in two rodent models using whole-body inhalation exposure and evaluated the role of prenatal exposure. Methods Time-mated Hsd:Sprague Dawley(R) SD(R) rats were exposed to 0, 150, 300, 600, 900, or 1200 ppm 2-ET via inhalation starting on gestation day 6 until parturition. Rat offspring (n = 8/exposure/sex) were exposed to the same concentrations as the respective dams for 2 weeks after weaning. Adult male and female B6C3F1/N mice (n = 5/exposure/sex) were exposed to the same concentrations for 2 weeks. Results and Discussion Exposure to >= 600 ppm 2-ET produced acute toxicity in rats and mice characterized by large decreases in survival, body weight, adverse clinical observations, and diffuse nasal olfactory epithelium degeneration (rats) or necrosis (mice). Due to the early removal of groups >= 600 ppm, most endpoint evaluations focused on lower exposure groups. In 150 and 300 ppm exposure groups, reproductive performance and littering were not significantly changed and body weights in exposed rats and mice were 9-18% lower than controls. Atrophy of the olfactory epithelium and nerves was observed in all animals exposed to 150 and 300 ppm. These lesions were more severe in mice than in rats. Conclusion Nasal lesions were observed in all animals after whole-body exposure up to 600 ppm 2-ET for 2 weeks. Future studies should focus on 2-ET metabolism and distribution to better understand species differences and refine hazard characterization of this understudied environmental contaminant.

Garcinia cambogia extract (GCE) is a popular botanical supplement used in weight loss products. Hydroxycitric acid (HCA) is the principal component in GCE. Due to lack of adequate toxicity data to assess the safe use of GCE, the National Toxicology Program is testing GCE in Hsd:Sprague Dawley® SD® rats following perinatal exposure and in adult B6C3F1/N mice. We report a validated method utilizing sample clean up with ultrafiltration followed by liquid chromatography-tandem mass spectrometry analysis to quantify HCA in rat plasma over the concentration range of 20 to 800 ng/mL. The method was linear (r2 ≥ 0.99) with the limits of quantitation (LOQ) and detection (LOD) of 20.0 and 3.9 ng/mL plasma, respectively. The accuracy (determined as relative error, RE) and precision (determined as relative standard deviation, RSD) using Quality Control standards analyzed over multiple days were ≤ ± 7.5% and ≤ 9.5%, respectively. The method can be applied to quantify HCA in study matrices (RE ≤ ± 23.0%; RSD ≤ 6.0) except gestational day (GD)18 fetus. The method was partially validated in GD18 fetal homogenate over the concentration range 60-3000 ng/g (r2 ≥ 0.99, RE ≤ ± 11.9%, and RSD ≤ 5.5%; LOQ 60.0 ng/g; LOD 7.77 ng/g). The standards as high as 20,000 ng/mL (plasma) and 502,000 ng/g (fetus) can successfully be quantified after diluting into the validated range (RE ≤ ± 2.6%; RSD ≤ 5.2%). These data demonstrate that the method is suitable to quantify HCA in rodent matrices and can be adapted to other biological matrices.

Polycyclic aromatic compounds (PACs) are compounds with a minimum of two six-atom aromatic fused rings. PACs arise from incomplete combustion or thermal decomposition of organic matter and are ubiquitous in the environment. Within PACs, carcinogenicity is generally regarded to be the most important public health concern. However, toxicity in other systems (reproductive and developmental toxicity, immunotoxicity) has also been reported. Despite the large number of PACs identified in the environment, research attention to understand exposure and health effects of PACs has focused on a relatively limited subset, namely polycyclic aromatic hydrocarbons (PAHs), the PACs with only carbon and hydrogen atoms. To triage the rest of the vast number of PACs for more resource-intensive testing, we developed a data-driven approach to contextualize hazard characterization of PACs, by leveraging the available data from various data streams (in silico toxicity, in vitro activity, structural fingerprints, and in vivo data availability). The PACs were clustered on the basis of their in silico toxicity profiles containing predictions from 8 different categories (carcinogenicity, cardiotoxicity, developmental toxicity, genotoxicity, hepatotoxicity, neurotoxicity, reproductive toxicity, and urinary toxicity). We found that PACs with the same parent structure (e.g., fluorene) could have diverse in silico toxicity profiles. In contrast, PACs with similar substituted groups (e.g., alkylated-PAHs) or heterocyclics (e.g., N-PACs) with varying ring sizes could have similar in silico toxicity profiles, suggesting that these groups are better candidates for toxicity read-across analysis. The clusters/regions associated with certain in silico toxicity, in vitro activity, and structural fingerprints were identified. We found that genotoxicity/carcinogenicity (in silico toxicity) and xenobiotic homeostasis and stress response (in vitro activity), respectively, dominate the toxicity/activity variation seen in the PACs. The "hot spots" with enriched toxicity/activity in conjunction with availability of in vivo carcinogenicity data revealed regions of either data-poor (hydroxylated-PAHs) or data-rich (unsubstituted, parent PAHs) PACs. These regions offer potential targets for prioritization of further in vivo assessment and for chemical read-across efforts. The analysis results are searchable through an interactive web application (https://ntp.niehs.nih.gov/go/pacs_tableau), allowing for alternative hypothesis generation.

Phenolic benzotriazoles are ultraviolet-light absorbers used in a variety of industrial and consumer applications. We investigated the toxicokinetic behaviour of 9 compounds, covering unsubstituted, monosubstituted, disubstituted, and trisubstituted compounds, following a single gavage (30 and 300 mg/kg) and intravenous (IV) (2.25 mg/kg) administration in male rats. Following IV administration, no distinct pattern in plasma elimination was observed for the compounds with half-lives ranging from 15.4-84.8 h. Systemic exposure parameters, maximum concentration (C-max) and area under the concentration time curve (AUC), generally increased with the degree of substitution. Following gavage administration, C-max and AUC of unsubstituted compound were lower compared to the substituted compounds. C-max and AUC increased <= 7-fold with a 10-fold increase in the dose except for the AUC of the unsubstituted compound where the increase was 30-fold. Plasma elimination half-lives for the class ranged from 1.57 to 192 h with the exception of 30 mg/kg drometrizole. Oral bioavailability was low with similar to 6% estimated for unsubstituted compound and 12.8-23% for others at 30 mg/kg dose. Bioavailability was lower following administration of the higher dose. Taken collectively, these data point to low oral absorption of phenolic benzotriazoles. The absorption decreased with increasing dose. Substituted compounds may be less metabolized compared to the unsubstituted.

Human exposure to pentabromodiphenyl ether (PBDE) mixture (DE-71) and its PBDE-47 congener can occur both in utero and during lactation. Here, we tested the hypothesis that PBDE-induced neonatal hepatic transcriptomic alterations in Wistar Han rat pups can inform on potential toxicity and carcinogenicity after longer term PBDE exposures. Wistar Han rat dams were exposed to either DE-71 or PBDE-47 daily from gestation day (GD 6) through postnatal day 4 (PND 4). Total plasma thyroxine (T4) was decreased in PND 4 pups. In liver, transcripts for CYPs and conjugation enzymes, Nrf2, and ABC transporters were upregulated. In general, the hepatic transcriptomic alterations after exposure to DE-71 or PBDE-47 were similar and provided early indicators of oxidative stress and metabolic alterations, key characteristics of toxicity processes. The transcriptional benchmark dose lower confidence limits of the most sensitive biological processes were lower for PBDE-47 than for the PBDE mixture. Neonatal rat liver transcriptomic data provide early indicators on molecular pathway alterations that may lead to toxicity and/or carcinogenicity if the exposures continue for longer durations. These early toxicogenomic indicators may be used to help prioritize chemicals for a more complete toxicity and cancer risk evaluation.