An in vitro-in silico workflow for predicting renal clearance of PFAS.

Per- and poly-fluoroalkyl substances (PFAS) have a wide range of elimination half-lives (days to years) in humans, thought to be in part due to variation in proximal tubule reabsorption. While human biomonitoring studies provide important data for some PFAS, renal clearance (CLrenal) predictions for hundreds of PFAS in commerce requires experimental studies with in vitro models and physiologically-based in vitro-to-in vivo extrapolation (IVIVE). Options for studying renal proximal tubule pharmacokinetics include cultures of renal proximal tubule epithelial cells (RPTECs) and/or microphysiological systems. This study aimed to compare CLrenal predictions for PFAS using in vitro models of varying complexity (96-well plates, static 24-well Transwells and a fluidic microphysiological model, all using human telomerase reverse transcriptase-immortalized and OAT1-overexpressing RPTECs combined with in silico physiologically-based IVIVE. Three PFAS were tested: one with a long half-life (PFOS) and two with shorter half-lives (PFHxA and PFBS). PFAS were added either individually (5 µM) or as a mixture (2 µM of each substance) for 48 h. Bayesian methods were used to fit concentrations measured in media and cells to a three-compartmental model to obtain the in vitro permeability rates, which were then used as inputs for a physiologically-based IVIVE model to estimate in vivo CLrenal. Our predictions for human CLrenal of PFAS were highly concordant with available values from in vivo human studies. The relative values of CLrenal between slow- and faster-clearance PFAS were most highly concordant between predictions from 2D culture and corresponding in vivo values. However, the predictions from the more complex model (with or without flow) exhibited greater concordance with absolute CLrenal. Overall, we conclude that a combined in vitro-in silico workflow can predict absolute CLrenal values, and effectively distinguish between PFAS with slow and faster clearance, thereby allowing prioritization of PFAS with a greater potential for bioaccumulation in humans.

Endocrine-disrupting compounds and their impact on human placental function: evidence from placenta organ-on-chip studies.

The effects of endocrine-disrupting compounds (EDCs) on the placenta, a critical gestational organ for xenobiotic protection, are well reported; however, models to determine the role of EDCs in placental disruption are limited. An advanced 2nd-trimester human placenta organ-on-chip model (2TPLA-OOC) was developed and validated, with six representative cells of the maternal and the fetal interface interconnected with microchannels. Various EDCs (150 ng mL-1 each of bisphenol A, bisphenol S, and polybrominated diphenyl ethers-47 and -99) were gradually propagated across the chip for 72 hours, and their various effects were determined. Cigarette smoke extract (CSE), an environmental risk factor, was used as a positive control. EDCs produced overall oxidative stress in the placental/decidual cells, induced cell-specific endocrine effects, caused limited (<10%) apoptosis/necrosis in trophoblasts and mesenchymal cells, induced localized inflammation but an overall anti-inflammatory shift, did not change immune cell migration from stroma to decidua, and did not affect placental nutrient transport. Overall, (1) the humanized 2TPLA-OOC recreated the placental organ and generated data distinct from the trophoblast and other cells studied in isolation, and (2) at doses associated with adverse pregnancies, EDCs produced limited and localized insults, and the whole organ compensated for the exposure.

Ten years of using key characteristics of human carcinogens to organize and evaluate mechanistic evidence in IARC Monographs on the identification of carcinogenic hazards to humans: Patterns and associations.

Systematic review and evaluation of mechanistic evidence using the Key Characteristics approach was proposed by the International Agency for Research on Cancer (IARC) in 2012 and used by the IARC Monographs Working Groups since 2015. Key Characteristics are 10 features of agents known to cause cancer in humans. From 2015 to 2022, a total of 19 Monographs (73 agents combined) used Key Characteristics for cancer hazard classification. We hypothesized that a retrospective analysis of applications of the Key Characteristics approach to cancer hazard classification using heterogenous mechanistic data on diverse agents would be informative for systematic reviews in decision-making. We extracted information on the conclusions, data types, and the role mechanistic data played in the cancer hazard classification from each Monograph. Statistical analyses identified patterns in the use of Key Characteristics, as well as trends and correlations among Key Characteristics, data types, and ultimate decisions. Despite gaps in data for many agents and Key Characteristics, several significant results emerged. Mechanistic data from in vivo animal, in vitro animal, and in vitro human studies were most impactful in concluding that an agent could cause cancer via a Key Characteristic. To exclude the involvement of a Key Characteristic, data from large-scale systematic in vitro testing programs such as ToxCast, were most informative. Overall, increased availability of systemized data streams, such as human in vitro data, would provide the basis for more confident and informed conclusions about both positive and negative associations and inform expert judgments on cancer hazard.

Application of Ion Mobility Spectrometry-Mass Spectrometry for Compositional Characterization and Fingerprinting of a Library of Diverse Crude Oil Samples.

Exposure characterization of crude oils, especially in time-sensitive circumstances such as spills and disasters, is a well-known analytical chemistry challenge. Gas chromatography-mass spectrometry is commonly used for "fingerprinting" and origin tracing in oil spills; however, this method is both time-consuming and lacks the resolving power to separate co-eluting compounds. Recent advances in methodologies to analyze petroleum substances using high-resolution analytical techniques have demonstrated both improved resolving power and higher throughput. One such method, ion mobility spectrometry-mass spectrometry (IMS-MS), is especially promising because it is both rapid and high-throughput, with the ability to discern among highly homologous hydrocarbon molecules. Previous applications of IMS-MS to crude oil analyses included a limited number of samples and did not provide detailed characterization of chemical constituents. We analyzed a diverse library of 195 crude oil samples using IMS-MS and applied a computational workflow to assign molecular formulas to individual features. The oils were from 12 groups based on geographical and geological origins: non-US (1 group), US onshore (3), and US Gulf of Mexico offshore (8). We hypothesized that information acquired through IMS-MS data would provide a more confident grouping and yield additional fingerprint information. Chemical composition data from IMS-MS was used for unsupervised hierarchical clustering, as well as machine learning-based supervised analysis to predict geographic and source rock categories for each sample; the latter also yielded several novel prospective biomarkers for fingerprinting of crude oils. We found that IMS-MS data have complementary advantages for fingerprinting and characterization of diverse crude oils and that proposed polycyclic aromatic hydrocarbon biomarkers can be used for rapid exposure characterization. Environ Toxicol Chem 2023;42:2336-2349. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Ten Years of Using Key Characteristics of Human Carcinogens to Organize and Evaluate Mechanistic Evidence in IARC Monographs on the Identification of Carcinogenic Hazards to Humans: Patterns and Associations.

Systematic review and evaluation of the mechanistic evidence only recently been instituted in cancer hazard identification step of decision-making. One example of organizing and evaluating mechanistic evidence is the Key Characteristics approach of the International Agency for Research on Cancer (IARC) Monographs on the Identification of Carcinogenic Hazards to Humans. The Key Characteristics of Human Carcinogens were proposed almost 10 years ago and have been used in every IARC Monograph since 2015. We investigated the patterns and associations in the use of Key Characteristics by the independent expert Working Groups. We examined 19 Monographs (2015-2022) that evaluated 73 agents. We extracted information on the conclusions by each Working Group on the strength of evidence for agent-Key Characteristic combinations, data types that were available for decisions, and the role mechanistic data played in the final cancer hazard classification. We conducted both descriptive and association analyses within and across data types. We found that IARC Working Groups were cautious when evaluating mechanistic evidence: for only ∼13% of the agents was strong evidence assigned for any Key Characteristic. Genotoxicity and cell proliferation were most data-rich, while little evidence was available for DNA repair and immortalization Key Characteristics. Analysis of the associations among Key Characteristics revealed that only chemical's metabolic activation was significantly co-occurring with genotoxicity and cell proliferation/death. Evidence from exposed humans was limited, while mechanistic evidence from rodent studies in vivo was often available. Only genotoxicity and cell proliferation/death were strongly associated with decisions on whether mechanistic data was impactful on the final cancer hazard classification. The practice of using the Key Characteristics approach is now well-established at IARC Monographs and other government agencies and the analyses presented herein will inform the future use of mechanistic evidence in regulatory decision-making.

Temporal chemical composition changes in water below a crude oil slick irradiated with natural sunlight.

Photooxidation can alter the environmental fate and effects of spilled oil. To better understand this process, oil slicks were generated on seawater mesocosms and exposed to sunlight for 8 days. The molecular composition of seawater under irradiated and non-irradiated oil slicks was characterized using ion mobility spectrometry-mass spectrometry and polyaromatic hydrocarbons analyses. Biomimetic extraction was performed to quantify neutral and ionized constituents. Results show that seawater underneath irradiated oil showed significantly higher amounts of hydrocarbons with oxygen- and sulfur-containing by-products peaking by day 4-6; however, concentrations of dissolved organic carbon were similar. Biomimetic extraction indicated toxic units in irradiated mesocosms increased, mainly due to ionized components, but remained <1, suggesting limited potential for ecotoxicity. Because the experimental design mimicked important aspects of natural conditions (freshly collected seawater, natural sunlight, and relevant oil thickness and concentrations), this study improves our understanding of the effects of photooxidation during a marine oil spill.

Reanalysis of Trichloroethylene and Tetrachloroethylene Metabolism to Glutathione Conjugates Using Human, Rat, and Mouse Liver in Vitro Models to Improve Precision in Risk Characterization.

BACKGROUND: Both trichloroethylene (TCE) and tetrachloroethylene (PCE) are high-priority chemicals subject to numerous human health risk evaluations by a range of agencies. Metabolism of TCE and PCE determines their ultimate toxicity; important uncertainties exist in quantitative characterization of metabolism to genotoxic moieties through glutathione (GSH) conjugation and species differences therein. OBJECTIVES: This study aimed to address these uncertainties using novel in vitro liver models, interspecies comparison, and a sensitive assay for quantification of GSH conjugates of TCE and PCE, S-(1,2-dichlorovinyl)glutathione (DCVG) and S-(1,2,2-trichlorovinyl) glutathione (TCVG), respectively. METHODS: Liver in vitro models used herein were suspension, 2-D culture, and micropatterned coculture (MPCC) with primary human, rat, and mouse hepatocytes, as well as human induced pluripotent stem cell (iPSC)-derived hepatocytes (iHep). RESULTS: We found that, although efficiency of metabolism varied among models, consistent with known differences in their metabolic capacity, formation rates of DCVG and TCVG generally followed the patterns human≥rat≥mouse, and primary hepatocytes>iHep. Data derived from MPCC were most consistent with estimates from physiologically based pharmacokinetic models calibrated to in vivo data. DISCUSSION: For TCE, the new data provided additional empirical support for inclusion of GSH conjugation-mediated kidney effects as critical for the derivation of noncancer toxicity values. For PCE, the data reduced previous uncertainties regarding the extent of TCVG formation in humans; this information was used to update several candidate kidney-specific noncancer toxicity values. Overall, MPCC-derived data provided physiologically relevant estimates of GSH-mediated metabolism of TCE and PCE to reduce uncertainties in interspecies extrapolation that constrained previous risk evaluations, thereby increasing the precision of risk characterizations of these high-priority toxicants. https://doi.org/10.1289/EHP12006.

Epigenetic alterations induced by genotoxic occupational and environmental human chemical carcinogens: An update of a systematic literature review.

Epigenetic alterations, such as changes in DNA methylation, histones/chromatin structure, nucleosome positioning, and expression of non-coding RNAs, are recognized among key characteristics of carcinogens; they may occur independently or concomitantly with genotoxic effects. While data on genotoxicity are collected through standardized guideline tests, data collected on epigenetic effects is far less uniform. In 2016, we conducted a systematic review of published studies of genotoxic carcinogens that reported epigenetic endpoints to better understand the evidence for epigenetic alterations of human carcinogens, and the potential association with genotoxic endpoints. Since then, the number of studies of epigenetic effects of chemicals has nearly doubled. This review stands as an update on epigenetic alterations induced by occupational and environmental human carcinogens that were previously and recently classified as Group 1 by the International Agency for Research on Cancer. We found that the evidence of epigenetic effects remains uneven across agents. Studies of DNA methylation are most abundant, while reports concerning effects on non-coding RNA have increased over the past 5 years. By contrast, mechanistic toxicology studies of histone modifications and chromatin state alterations remain few. We found that most publications of epigenetic effects of carcinogens were studies in exposed humans or human cells. Studies in rodents represent the second most common species used for epigenetic studies in toxicology, in vivo exposures being the most predominant. Future studies should incorporate dose- and time-dependent study designs and also investigate the persistence of effects following cessation of exposure, considering the dynamic nature of most epigenetic alterations.

Oil Irradiation Experiments Document Changes in Oil Properties, Molecular Composition, and Dispersant Effectiveness Associated with Oil Photo-Oxidation.

While chemical dispersants are a powerful tool for treating spilled oil, their effectiveness can be limited by oil weathering processes such as evaporation and emulsification. It has been suggested that oil photo-oxidation could exacerbate these challenges. To address the role of oil photo-oxidation in dispersant effectiveness, outdoor mesocosm experiments with crude oil on seawater were performed. Changes in bulk oil properties and molecular composition were quantified to characterize oil photo-oxidation over 11 days. To test relative dispersant effectiveness, oil residues were evaluated using the Baffled Flask Test. The results show that oil irradiation led to oxygen incorporation, formation of oxygenated hydrocarbons, and higher oil viscosities. Oil irradiation was associated with decreased dispersant efficacy, with effectiveness falling from 80 to <50% in the Baffled Flask Test after more than 3 days of irradiation. Increasing photo-oxidation-induced viscosity seems to drive the decreasing dispersant effectiveness. Comparing the Baffled Flask Test results with field data from the Deepwater Horizon oil spill showed that laboratory dispersant tests underestimate the dispersion of photo-oxidized oil in the field. Overall, the results suggest that prompt dispersant application (within 2-4 days), as recommended by current oil spill response guidelines, is necessary for effective dispersion of spilled oil.

Characterization of population variability of 1,3-butadiene derived protein adducts in humans and mice.

1,3-butadiene is a known human carcinogen and a chemical to which humans are exposed occupationally and through environmental pollution. Inhalation risk assessment of 1,3-butadiene was completed several decades ago before data on molecular biomarkers of exposure and effect have been reported from both human studies of workers and experimental studies in mice. To improve risk assessment of 1,3-butadiene, the quantitative characterization of uncertainty in estimations of inter-individual variability in cancer-related effects is needed. For this, we ought to take advantage of the availability of the data on 1,3-butadiene hemoglobin adducts, well established biomarkers of the internal dose of the reactive epoxides, from several large-scale human studies and from a study in a Collaborative Cross mouse population. We found that in humans, toxicokinetic uncertainty factor for 99th percentile of the population ranged from 3.27 to 7.9, depending on the hemoglobin adduct. For mice, these values ranged from less than 2 to 7.51, depending on the dose and the adduct. Quantitative estimated from this study can be used to reduce uncertainties in the parameter estimates used in the models to derive the inhalation unit risk, as well as to address possible differences in variability in 1,3-butadiene metabolism that may be dose-related.

Molecular mechanisms of environmental toxin cadmium at the feto-maternal interface investigated using an organ-on-chip (FMi-OOC) model.

Human labor is associated with feto-maternal-derived signals that coordinate to initiate delivery. Exposure to environmental chemicals can prematurely trigger labor-initiating signals at the feto-maternal interface (FMi: decidua, amniochorion), leading to spontaneous preterm birth (PTB). Testing the association between environmental chemical exposure and PTB is difficult due to many limitations in vivo or in vitro. Physiological organ-on-chips (OOCs) are potential alternatives for studying mechanisms leading to PTB. The presented study tested the effect of maternal exposure to cadmium (Cd), an environmental toxin, using the FMi-OOC that incorporates maternal decidua cells and three different fetal cells (chorion, amnion mesenchymal, and amnion epithelial cells). Cd transport through the FMi and its impact on cell cycle, cell death, and inflammation were analyzed. Cd treatment resulted in significant cell death and a pro-inflammatory environment in the maternal decidua, but had minimal effect on the fetal chorion cells, and no effect in the fetal amnion cells compared to controls. The maternal response, but lack of fetal response, indicates that Cd-mediated adverse effects originate from maternal pathophysiology rather than fetal-derived triggers of preterm labor. This study demonstrates that the FMi-OOC can indeed predict the response of FMi upon exposure to chemicals, opening the possibility for using OOC models for environmental toxin screens.

Intra- and Inter-Species Variability in Urinary N7-(1-Hydroxy-3-buten-2-yl)guanine Adducts Following Inhalation Exposure to 1,3-Butadiene.

1,3-Butadiene is a known carcinogen primarily targeting lymphoid tissues, lung, and liver. Cytochrome P450 activates butadiene to epoxides which form covalent DNA adducts that are thought to be a key mechanistic event in cancer. Previous studies suggested that inter-species, -tissue, and -individual susceptibility to adverse health effects of butadiene exposure may be due to differences in metabolism and other mechanisms. In this study, we aimed to examine the extent of inter-individual and inter-species variability in the urinary N7-(1-hydroxy-3-buten-2-yl)guanine (EB-GII) DNA adduct, a well-known biomarker of exposure to butadiene. For a population variability study in mice, we used the collaborative cross model. Female and male mice from five strains were exposed to filtered air or butadiene (590 ppm, 6 h/day, 5 days/week for 2 weeks) by inhalation. Urine samples were collected, and the metabolic activation of butadiene by DNA-reactive species was quantified as urinary EB-GII adducts. We quantified the degree of EB-GII variation across mouse strains and sexes; then, we compared this variation with the data from rats (exposed to 62.5 or 200 ppm butadiene) and humans (0.004-2.2 ppm butadiene). We show that sex and strain are significant contributors to the variability in urinary EB-GII levels in mice. In addition, we find that the degree of variability in urinary EB-GII in collaborative cross mice, when expressed as an uncertainty factor for the inter-individual variability (UFH), is relatively modest (≤threefold) possibly due to metabolic saturation. By contrast, the variability in urinary EB-GII (adjusted for exposure) observed in humans, while larger than the default value of 10-fold, is largely consistent with UFH estimates for other chemicals based on human data for non-cancer endpoints. Overall, these data demonstrate that urinary EB-GII levels, particularly from human studies, may be useful for quantitative characterization of human variability in cancer risks to butadiene.

Quantitative NanoLC/NSI+-HRMS Method for 1,3-Butadiene Induced bis-N7-guanine DNA-DNA Cross-Links in Urine.

1,3-Butadiene (BD) is a common environmental and industrial chemical widely used in plastic and rubber manufacturing and also present in cigarette smoke and automobile exhaust. BD is classified as a known human carcinogen based on evidence of carcinogenicity in laboratory animals treated with BD by inhalation and epidemiological studies revealing an increased risk of leukemia and lymphohematopoietic cancers in workers occupationally exposed to BD. Upon exposure via inhalation, BD is bioactivated to several toxic epoxides including 3,4-epoxy-1-butene (EB), 3,4-epoxy-1,2-butanediol (EBD), and 1,2,3,4-diepoxybutane (DEB); these are conjugated with glutathione and excreted as 2-(N-acetyl-L-cystein-S-yl)-1-hydroxybut-3-ene/1-(N-acetyl-L-cystein-S-yl)-2-hydroxybut-3-ene (MHBMA), 4-(N-acetyl-L-cystein-S-yl)-1,2-dihydroxybutane (DHBMA), and 1,4-bis-(N-acetyl-L-cystein-S-yl)butane-2,3-diol (bis-BDMA). Exposure to DEB generates monoalkylated DNA adducts, DNA-DNA crosslinks, and DNA-protein crosslinks, which can cause base substitutions, genomic rearrangements, and large genomic deletions. In this study, we developed a quantitative nanoLC/NSI+-HRMS methodology for 1,4-bis-(gua-7-yl)-2,3-butanediol (bis-N7G-BD) adducts in urine (LOD: 0.1 fmol/mL urine, LOQ: 1.0 fmol/mL urine). This novel method was used to quantify bis-N7G-BD in urine of mice treated with 590 ± 150 ppm BD for 2 weeks (6 h/day, 5 days/week). Bis-N7G-BD was detected in urine of male and female BD-exposed mice (574.6 ± 206.0 and 571.1 ± 163.4 pg/mg of creatinine, respectively). In addition, major urinary metabolites of BD, bis-BDMA, MHBMA and DHBMA, were measured in the same samples. Urinary bis-N7G-BD adduct levels correlated with DEB-derived metabolite bis-BDMA (r = 0.80, Pearson correlation), but not with the EB-derived DNA adducts (EB-GII) or EB-derived metabolites MHBMA and DHBMA (r = 0.24, r = 0.14, r = 0.18, respectively, Pearson correlations). Urinary bis-N7G-BD could be employed as a novel non-invasive biomarker of exposure to BD and bioactivation to its most mutagenic metabolite, DEB. This method will be useful for future studies of 1,3-butadiene exposure and metabolism.

The DEN and CCl4 -Induced Mouse Model of Fibrosis and Inflammation-Associated Hepatocellular Carcinoma.

Human hepatocellular carcinoma (HCC) develops most often as a complication of fibrosis or cirrhosis. Although most human studies of HCC provide crucial insights into the molecular signatures of HCC, they seldom address its etiology. Mouse models provide essential tools for investigating the pathogenesis of HCC, but the majority of rodent cancer models do not feature liver fibrosis. Detailed here is a protocol for an experimental mouse model of HCC that arises in association with advanced liver fibrosis. The disease model is induced by a single injection of N-nitrosodiethylamine (DEN) at 2 weeks of age followed by repeated administration of carbon tetrachloride (CCl4 ) from 8 weeks of age for up to 14 consecutive weeks. A dramatic potentiation of liver tumor incidence is observed following administration of DEN and CCl4 , with 100% of mice developing liver tumors at 5 months of age. This model has been employed for studying the molecular mechanisms of fibrogenesis and HCC development, as well as for cancer hazard/chemotherapy testing of drug candidates. © 2021 Wiley Periodicals LLC. Basic Protocol: The DEN and CCl4 -induced mouse model of fibrosis and inflammation-associated hepatocellular carcinoma.

Quantitative In Vitro-to-In Vivo Extrapolation for Mixtures: A Case Study of Superfund Priority List Pesticides.

In vitro cell-based toxicity testing methods generate large amounts of data informative for risk-based evaluations. To allow extrapolation of the quantitative outputs from cell-based tests to the equivalent exposure levels in humans, reverse toxicokinetic modeling is used to conduct in vitro-to-in vivo extrapolation (IVIVE) from in vitro effective concentrations to in vivo oral dose equivalents. IVIVE modeling approaches for individual chemicals are well-established; however, the potential implications of chemical-to-chemical interactions in mixture settings on IVIVE remain largely unexplored. We hypothesized that chemical coexposures could modulate both protein binding efficiency and hepatocyte clearance of the chemicals in a mixture, which would in turn affect the quantitative IVIVE toxicokinetic parameters. To test this hypothesis, we used 20 pesticides from the Agency for Toxic Substances and Disease Registry Substance Priority List, both individually and as equimolar mixtures, and investigated the concentration-dependent effects of chemical interactions on in vitro toxicokinetic parameters. Plasma protein binding efficiency was determined by using ultracentrifugation, and hepatocyte clearance was estimated in suspensions of cryopreserved primary human hepatocytes. We found that for single chemicals, the protein binding efficiencies were similar at different test concentrations. In a mixture, however, both protein binding efficiency and hepatocyte clearance were affected. When IVIVE was conducted using mixture-derived toxicokinetic data, more conservative estimates of activity-to-exposure ratios were produced as compared with using data from single chemical experiments. Because humans are exposed to mixtures of chemicals, this study is significant as it demonstrates the importance of incorporating mixture-derived parameters into IVIVE for in vitro bioactivity data in order to accurately prioritize risks and facilitate science-based decision-making.

Key Characteristics of Human Hepatotoxicants as a Basis for Identification and Characterization of the Causes of Liver Toxicity.

Hazard identification regarding adverse effects on the liver is a critical step in safety evaluations of drugs and other chemicals. Current testing paradigms for hepatotoxicity rely heavily on preclinical studies in animals and human data (epidemiology and clinical trials). Mechanistic understanding of the molecular and cellular pathways that may cause or exacerbate hepatotoxicity is well advanced and holds promise for identification of hepatotoxicants. One of the challenges in translating mechanistic evidence into robust decisions about potential hepatotoxicity is the lack of a systematic approach to integrate these data to help identify liver toxicity hazards. Recently, marked improvements were achieved in the practice of hazard identification of carcinogens, female and male reproductive toxicants, and endocrine disrupting chemicals using the key characteristics approach. Here, we describe the methods by which key characteristics of human hepatotoxicants were identified and provide examples for how they could be used to systematically identify, organize, and use mechanistic data when identifying hepatotoxicants.

Spatial and temporal distribution of surface water contaminants in the Houston Ship Channel after the Intercontinental Terminal Company Fire.

BACKGROUND: The fire at the Intercontinental Terminals Company (ITC, Deer Park, La Porte, TX, USA) from March 17 to 20, 2019 resulted in substantial releases of chemical contaminants to the environment, including the surface waters of the Houston Ship Channel. OBJECTIVE: To characterize spatial and temporal trends, as well as potential human health risks, from these releases. METHODS: Out of 433 substances with available data, seven were selected for analysis: benzene, toluene, ethylbenzene, xylenes, oil and grease, suspended solids, and total petroleum hydrocarbons. Spatial and temporal concentration trends were characterized, and hazard quotients and cancer risks were calculated to estimate the potential for human health impacts from these contaminants. RESULTS: Temporal analysis showed presence of these chemical contaminants in water immediately after the event; their concentrations dissipated substantially within 4 weeks. The spatial distribution of contaminants indicated the highest concentrations in the waterways within about 1 km of the ITC. The greatest potential human health risks stemmed from presence of benzene. SIGNIFICANCE: A short-term but substantial spike in the concentrations of a number of hazardous contaminants occurred near the incident, with concentrations returning to apparent baseline levels within 1 month likely due to a combination of volatization, dilution and degradation.

Diminished Hepatocarcinogenesis by a Potent, High-Affinity Human PPARα Agonist in PPARA-Humanized Mice.

Ppara-null and PPARA-humanized mice are refractory to hepatocarcinogenesis caused by the peroxisome proliferator-activated receptor-α (PPARα) agonist Wy-14,643. However, the duration of these earlier studies was limited to approximately 1 year of treatment, and the ligand used has a higher affinity for the mouse PPARα compared to the human PPARα. Thus, the present study examined the effect of long-term administration of a potent, high-affinity human PPARα agonist (GW7647) on hepatocarcinogenesis in wild-type, Ppara-null, or PPARA-humanized mice. In wild-type mice, GW7647 caused hepatic expression of known PPARα target genes, hepatomegaly, hepatic MYC expression, hepatic cytotoxicity, and a high incidence of hepatocarcinogenesis. By contrast, these effects were essentially absent in Ppara-null mice or diminished in PPARA-humanized mice, although hepatocarcinogenesis was observed in both genotypes. Enhanced fatty change (steatosis) was also observed in both Ppara-null and PPARA-humanized mice independent of GW7647. PPARA-humanized mice administered GW7647 also exhibited increased necrosis after 5 weeks of treatment. Results from these studies demonstrate that the mouse PPARα is required for hepatocarcinogenesis induced by GW7647 administered throughout adulthood. Results also indicate that a species difference exists between rodents and human PPARα in the response to ligand activation of PPARα. The hepatocarcinogenesis observed in control and treated Ppara-null mice is likely mediated in part by increased hepatic fatty change, whereas the hepatocarcinogenesis observed in PPARA-humanized mice may also be due to enhanced fatty change and cytotoxicity that could be influenced by the minimal activity of the human PPARα in this mouse line on downstream mouse PPARα target genes. The Ppara-null and PPARA-humanized mouse models are valuable tools for examining the mechanisms of PPARα-induced hepatocarcinogenesis, but the background level of liver cancer must be controlled for in the design and interpretation of studies that use these mice.

Species Differences between Mouse and Human PPARα in Modulating the Hepatocarcinogenic Effects of Perinatal Exposure to a High-Affinity Human PPARα Agonist in Mice.

Evidence suggests that species differences exist between rodents and humans in their biological responses to ligand activation of PPARα. Moreover, neonatal/postnatal rodents may be more sensitive to the effects of activating PPARα. Thus, the present studies examined the effects of chronic ligand activation of PPARα initiated during early neonatal development and continued into adulthood on hepatocarcinogenesis in mice. Wild-type, Ppara-null, or PPARA-humanized mice were administered a potent, high-affinity human PPARα agonist GW7647, and cohorts of mice were examined over time. Activation of PPARα with GW7647 increased expression of known PPARα target genes in liver and was associated with hepatomegaly, increased hepatic cytotoxicity and necrosis, increased expression of hepatic MYC, and a high incidence of hepatocarcinogenesis in wild-type mice. These effects did not occur or were largely diminished in Ppara-null and PPARA-humanized mice, although background levels of hepatocarcinogenesis were also noted in both Ppara-null and PPARA-humanized mice. More fatty change (steatosis) was also observed in both Ppara-null and PPARA-humanized mice independent of GW7647 administration. Results from these studies indicate that the mouse PPARα is required to mediate hepatocarcinogenesis induced by GW7647 in mice and that activation of the human PPARα with GW7647 in PPARA-humanized mice are diminished compared with wild-type mice. Ppara-null and PPARA-humanized mice are valuable tools for examining species differences in the mechanisms of PPARα-induced hepatocarcinogenesis, but background levels of liver cancer observed in aged Ppara-null and PPARA-humanized mice must be considered when interpreting results from studies that use these models. These results also demonstrate that early life exposure to a potent human PPARα agonist does not enhance sensitivity to hepatocarcinogenesis.

Environmental impacts of Hurricane Florence flooding in eastern North Carolina: temporal analysis of contaminant distribution and potential human health risks.

BACKGROUND: Hurricane Florence made landfall in North Carolina in September 2018 causing extensive flooding. Several potential point sources of hazardous substances and Superfund sites sustained water damage and contaminants may have been released into the environment. OBJECTIVE: This study conducted temporal analysis of contaminant distribution and potential human health risks from Hurricane Florence-associated flooding. METHODS: Soil samples were collected from 12 sites across four counties in North Carolina in September 2018, January and May 2019. Chemical analyses were performed for organics by gas chromatography-mass spectrometry. Metals were analyzed using inductively coupled plasma mass spectrometry. Hazard index and cancer risk were calculated using EPA Regional Screening Level Soil Screening Levels for residential soils. RESULTS: PAH and metals detected downstream from the coal ash storage pond that leaked were detected and were indicative of a pyrogenic source of contamination. PAH at these sites were of human health concern because cancer risk values exceeded 1 × 10-6 threshold. Other contaminants measured across sampling sites, or corresponding hazard index and cancer risk, did not exhibit spatial or temporal differences or were of concern. SIGNIFICANCE: This work shows the importance of rapid exposure assessment following natural disasters. It also establishes baseline levels of contaminants for future comparisons.