The 2022 world health organization reevaluation of human and mammalian toxic equivalency factors for polychlorinated dioxins, dibenzofurans and biphenyls.

In October 2022, the World Health Organization (WHO) convened an expert panel in Lisbon, Portugal in which the 2005 WHO TEFs for chlorinated dioxin-like compounds were reevaluated. In contrast to earlier panels that employed expert judgement and consensus-based assignment of TEF values, the present effort employed an update to the 2006 REP database, a consensus-based weighting scheme, a Bayesian dose response modeling and meta-analysis to derive "Best-Estimate" TEFs. The updated database contains almost double the number of datasets from the earlier version and includes metadata that informs the weighting scheme. The Bayesian analysis of this dataset results in an unbiased quantitative assessment of the congener-specific potencies with uncertainty estimates. The "Best-Estimate" TEF derived from the model was used to assign 2022 WHO-TEFs for almost all congeners and these values were not rounded to half-logs as was done previously. The exception was for the mono-ortho PCBs, for which the panel agreed to retain their 2005 WHO-TEFs due to limited and heterogenous data available for these compounds. Applying these new TEFs to a limited set of dioxin-like chemical concentrations measured in human milk and seafood indicates that the total toxic equivalents will tend to be lower than when using the 2005 TEFs.

Non-targeted chemical analysis of consumer botanical products labeled as blue cohosh (Caulophyllum thalictroides), goldenseal (Hydrastis canadensis), or yohimbe bark (Pausinystalia yohimbe) by NMR and MS.

Consumers have unprecedented access to botanical dietary supplements through online retailers, making it difficult to ensure product quality and authenticity. Therefore, methods to survey and compare chemical compositions across botanical products are needed. Nuclear magnetic resonance (NMR) spectroscopy and non-targeted mass spectrometry (MS) were used to chemically analyze commercial products labeled as containing one of three botanicals: blue cohosh, goldenseal, and yohimbe bark. Aqueous and organic phase extracts were prepared and analyzed in tandem with NMR followed by MS. We processed the non-targeted data using multivariate statistics to analyze the compositional similarity across extracts. In each case, there were several product outliers that were identified using principal component analysis (PCA). Evaluation of select known constituents proved useful to contextualize PCA subgroups, which in some cases supported or refuted product authenticity. The NMR and MS data reached similar conclusions independently but were also complementary.

Systematic evidence mapping informs a class-based approach to assessing personal care products and pubertal timing.

BACKGROUND: Personal care products (PCPs) contain many different compounds and are a source of exposure to endocrine disrupting chemicals (EDCs), including phthalates and phenols. Early-life exposure to EDCs commonly found in PCPs has been linked to earlier onset of puberty. OBJECTIVE: To characterize the human and animal evidence on the association between puberty-related outcomes and exposure to PCPs and their chemical constituents and, if there is sufficient evidence, identify groups of chemicals and outcomes to support a systematic review for a class-based hazard or risk assessment. METHODS: We followed the OHAT systematic review framework to characterize the human and animal evidence on the association between puberty-related health outcomes and exposure to PCPs and their chemical constituents. RESULTS: Ninety-eight human and 299 animal studies that evaluated a total of 96 different chemicals were identified and mapped by key concepts including chemical class, data stream, and puberty-related health outcome. Among these studies, phthalates and phenols were the most well-studied chemical classes. Most of the phthalate and phenol studies examined secondary sex characteristics and changes in estradiol and testosterone levels. Studies evaluating PCP use and other chemical classes (e.g., parabens) had less data. CONCLUSIONS: This systematic evidence map identified and mapped the published research evaluating the association between exposure to PCPs and their chemical constituents and puberty-related health outcomes. The resulting interactive visualization allows researchers to make evidence-based decisions on the available research by enabling them to search, sort, and filter the literature base of puberty-related studies by key concepts. This map can be used by researchers and regulators to prioritize and target future research and funding to reduce uncertainties and address data gaps. It also provides information to inform a class-based hazard or risk assessment on the association between phthalate and phenol exposures and puberty-related health outcomes.

Wrangling Whole Mixtures Risk Assessment: Recent Advances in Determining Sufficient Similarity.

Human health risk assessments for complex mixtures can address real-world exposures and protect public health. While risk assessors typically prefer whole mixture approaches over component-based approaches, data from the precise exposure of interest are often unavailable and surrogate data from a sufficiently similar mixture(s) are required. This review describes recent advances in determining sufficient similarity of whole, complex mixtures spanning the comparison of chemical features, bioactivity profiles, and statistical evaluation to determine "thresholds of similarity". Case studies, including water disinfection byproducts, botanical ingredients, and wildfire emissions, are used to highlight tools and methods. Limitations to application of sufficient similarity in risk-based decision making are reviewed and recommendations presented for developing best practice guidelines.

Improving the rigor and utility of botanical toxicity studies: Recommended resources.

Interest in botanicals, particularly as dietary supplement ingredients, is growing steadily. This growth, and the marketing of new ingredients and combination products as botanical dietary supplements, underscores the public health need for a better understanding of potential toxicities associated with use of these products. This article and accompanying template outline the resources to collect literature and relevant information to support the design of botanical toxicity studies. These resources provide critical information related to botanical identification, characterization, pre-clinical and clinical data, including adverse effects and interactions with pharmaceuticals. Toxicologists using these resources should collaborate with pharmacognosists and/or analytical chemists to enhance knowledge of the botanical material being tested. Overall, this guide and resource list is meant to help locate relevant information that can be leveraged to inform on decisions related to toxicity testing of botanicals, including the design of higher quality toxicological studies.

Immunotoxicity of N-butylbenzenesulfonamide: impacts on immune function in adult mice and developmentally exposed rats.

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).

Do Storage Conditions Affect Collected Cookstove Emission Samples? Implications for Field Studies.

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.

A geospatial modeling approach to quantifying the risk of exposure to environmental chemical mixtures via a common molecular target.

In the real world, individuals are exposed to chemicals from sources that vary over space and time. However, traditional risk assessments based on in vivo animal studies typically use a chemical-by-chemical approach and apical disease endpoints. New approach methodologies (NAMs) in toxicology, such as in vitro high-throughput (HTS) assays generated in Tox21 and ToxCast, can more readily provide mechanistic chemical hazard information for chemicals with no existing data than in vivo methods. In this paper, we establish a workflow to assess the joint action of 41 modeled ambient chemical exposures in the air from the USA-wide National Air Toxics Assessment by integrating human exposures with hazard data from curated HTS (cHTS) assays to identify counties where exposure to the local chemical mixture may perturb a common biological target. We exemplify this proof-of-concept using CYP1A1 mRNA up-regulation. We first estimate internal exposure and then convert the inhaled concentration to a steady state plasma concentration using physiologically based toxicokinetic modeling parameterized with county-specific information on ages and body weights. We then use the estimated blood plasma concentration and the concentration-response curve from the in vitro cHTS assay to determine the chemical-specific effects of the mixture components. Three mixture modeling methods were used to estimate the joint effect from exposure to the chemical mixture on the activity levels, which were geospatially mapped. Finally, a Monte Carlo uncertainty analysis was performed to quantify the influence of each parameter on the combined effects. This workflow demonstrates how NAMs can be used to predict early-stage biological perturbations that can lead to adverse health outcomes that result from exposure to chemical mixtures. As a result, this work will advance mixture risk assessment and other early events in the effects of chemicals.

Plant vs. Kidney: Evaluating Nephrotoxicity of Botanicals with the Latest Toxicological Tools.

Botanicals can cause nephrotoxicity via numerous mechanisms, including disrupting renal blood flow, damaging compartments along the nephron, and obstructing urinary flow. While uncommon, there are various reports of botanical-induced nephrotoxicity in the literature, such as from aristolochia (Aristolochia spp.) and rhubarb (Rheum spp.). However, at present, it is a challenge to assess the toxic potential of botanicals because their chemical composition is variable due to factors such as growing conditions and extraction techniques. Therefore, selecting a single representative sample for an in vivo study is difficult. Given the increasing use of botanicals as dietary supplements and herbal medicine, new approach methodologies (NAMs) are needed to evaluate the potential for renal toxicity to ensure public safety. Such approaches include in vitro models that use layers of physiological complexity to emulate the in vivo microenvironment, enhance the functional viability and differentiation of cell cultures, and improve sensitivity to nephrotoxic insults. Furthermore, computational tools such as physiologically based pharmacokinetic (PBPK) modeling can add confidence to these tools by simulating absorption, distribution, metabolism, and excretion. The development and implementation of NAMs for renal toxicity testing will allow specific mechanistic data to be generated, leading to a better understanding of the nephrotoxic potential of botanicals.

Development of the InTelligence And Machine LEarning (TAME) Toolkit for Introductory Data Science, Chemical-Biological Analyses, Predictive Modeling, and Database Mining for Environmental Health Research.

Research in environmental health is becoming increasingly reliant upon data science and computational methods that can more efficiently extract information from complex datasets. Data science and computational methods can be leveraged to better identify relationships between exposures to stressors in the environment and human disease outcomes, representing critical information needed to protect and improve global public health. Still, there remains a critical gap surrounding the training of researchers on these in silico methods. We aimed to address this gap by developing the inTelligence And Machine lEarning (TAME) Toolkit, promoting trainee-driven data generation, management, and analysis methods to "TAME" data in environmental health studies. Training modules were developed to provide applications-driven examples of data organization and analysis methods that can be used to address environmental health questions. Target audiences for these modules include students, post-baccalaureate and post-doctorate trainees, and professionals that are interested in expanding their skillset to include recent advances in data analysis methods relevant to environmental health, toxicology, exposure science, epidemiology, and bioinformatics/cheminformatics. Modules were developed by study coauthors using annotated script and were organized into three chapters within a GitHub Bookdown site. The first chapter of modules focuses on introductory data science, which includes the following topics: setting up R/RStudio and coding in the R environment; data organization basics; finding and visualizing data trends; high-dimensional data visualizations; and Findability, Accessibility, Interoperability, and Reusability (FAIR) data management practices. The second chapter of modules incorporates chemical-biological analyses and predictive modeling, spanning the following methods: dose-response modeling; machine learning and predictive modeling; mixtures analyses; -omics analyses; toxicokinetic modeling; and read-across toxicity predictions. The last chapter of modules was organized to provide examples on environmental health database mining and integration, including chemical exposure, health outcome, and environmental justice indicators. Training modules and associated data are publicly available online (https://uncsrp.github.io/Data-Analysis-Training-Modules/). Together, this resource provides unique opportunities to obtain introductory-level training on current data analysis methods applicable to 21st century science and environmental health.

Mixture Math: Deciding What to Add in a Cumulative Risk Assessment.

Component-based approaches for cumulative risk assessment provide an important tool for informing public health policy. While current quantitative cumulative risk assessments focus narrowly on pesticides that share a mechanism of action, growing scientific evidence supports expansion of their application to encompass stressors that target a common disease. Case studies have demonstrated dose additive effects of chemicals with different mechanisms of action on liver steatosis, craniofacial malformations, and male reproductive tract developmental disruption. Evidence also suggests that nonchemical stressors such as noise or psychosocial stress can modify effects of chemicals. Focused research attention is required before nonchemical stressors can routinely be included in quantitative cumulative risk assessments.

The common indoor air pollutant α-pinene is metabolised to a genotoxic metabolite α-pinene oxide.

α-Pinene caused a concentration-responsive increase in bladder hyperplasia and decrease in sperm counts in rodents following inhalation exposure. Additionally, it formed a prospective reactive metabolite, α-pinene oxide.To provide human relevant context for data generated in animal models and explore potential mechanism, we undertook studies to investigate the metabolism of α-pinene to α-pinene oxide and mutagenicity of α-pinene and α-pinene oxide.α-Pinene oxide was formed in rat and human microsomes and hepatocytes with some species differences. Based on area under the concentration versus time curves, the formation of α-pinene oxide was up to 4-fold higher in rats than in humans.While rat microsomes cleared α-pinene oxide faster than human microsomes, the clearance of α-pinene oxide in hepatocytes was similar between species.α-Pinene was not mutagenic with or without induced rat liver S9 in Salmonella typhimurium or Escherichia coli when tested up to 10 000 µg/plate while α-pinene oxide was mutagenic at ≥25 µg/plate.α-Pinene was metabolised to α-pinene oxide under the conditions of the bacterial mutation assay although the concentration was approximately 3-fold lower than the lowest α-pinene oxide concentration that was positive in the assay, potentially explaining the lack of mutagenicity observed with α-pinene.

The Botanical Safety Consortium: A public-private partnership to enhance the botanical safety toolkit.

Botanical dietary supplement use is widespread and growing, therefore, ensuring the safety of botanical products is a public health priority. This commentary describes the mission and objectives of the Botanical Safety Consortium (BSC) - a public-private partnership aimed at enhancing the toolkit for conducting the safety evaluation of botanicals. This partnership is the result of a Memorandum of Understanding between the US FDA, the National Institute of Environmental Health Sciences, and the Health and Environmental Sciences Institute. The BSC serves as a global forum for scientists from government, academia, consumer health groups, industry, and non-profit organizations to work collaboratively on adapting and integrating new approach methodologies (NAMs) into routine botanical safety assessments. The objectives of the BSC are to: 1) engage with a group of global stakeholders to leverage scientific safety approaches; 2) establish appropriate levels of chemical characterization for botanicals as complex mixtures; 3) identify pragmatic, fit-for-purpose NAMs to evaluate botanical safety; 4) evaluate the application of these tools via comparison to the currently available safety information on selected botanicals; 5) and integrate these tools into a framework that can facilitate the evaluation of botanicals. Initially, the BSC is focused on oral exposure from dietary supplements, but this scope could be expanded in future phases of work. This commentary provides an overview of the structure, goals, and strategies of this initiative and insights regarding our first objectives, namely the selection and prioritization of botanicals based on putative toxicological properties.

Using the Key Characteristics of Carcinogens to Develop Research on Chemical Mixtures and Cancer.

BACKGROUND: People are exposed to numerous chemicals throughout their lifetimes. Many of these chemicals display one or more of the key characteristics of carcinogens or interact with processes described in the hallmarks of cancer. Therefore, evaluating the effects of chemical mixtures on cancer development is an important pursuit. Challenges involved in designing research studies to evaluate the joint action of chemicals on cancer risk include the time taken to perform the experiments because of the long latency and choosing an appropriate experimental design. OBJECTIVES: The objectives of this work are to present the case for developing a research program on mixtures of environmental chemicals and cancer risk and describe recommended approaches. METHODS: A working group comprising the coauthors focused attention on the design of mixtures studies to inform cancer risk assessment as part of a larger effort to refine the key characteristics of carcinogens and explore their application. Working group members reviewed the key characteristics of carcinogens, hallmarks of cancer, and mixtures research for other disease end points. The group discussed options for developing tractable projects to evaluate the joint effects of environmental chemicals on cancer development. RESULTS AND DISCUSSION: Three approaches for developing a research program to evaluate the effects of mixtures on cancer development were proposed: a chemical screening approach, a transgenic model-based approach, and a disease-centered approach. Advantages and disadvantages of each are discussed. https://doi.org/10.1289/EHP8525.

Toxicokinetic evaluation of the common indoor air pollutant, α-pinene, and its potential reactive metabolite, α-pinene oxide, following inhalation exposure in rodents.

The toxicokinetic behavior of α-pinene and its potential reactive metabolite, α-pinene oxide, was investigated following whole body inhalation exposure to 50 and 100 ppm α-pinene in rats and mice for 6 h per day for 7d. In both species and sexes, the maximum blood concentration (Cmax) increased more than proportionally while the increase in area under the concentration time curve (AUC) was proportional to the exposure concentration. When normalized to the calculated dose (D), both Cmax/D (male rats, 12.2-54.5; female rats, 17.4-74.1; male mice, 7.41-14.2; female mice, 6.59-13.0 (ng/mL)/(mg/kg)) and AUC/D (male rats, 28.9-31.1; female rats, 55.8-56.8; male mice, 18.1-19.4; female mice, 19.2-22.5 (h*ng/mL)/(mg/kg)) in rats were higher than in mice and in female rats were higher than in male rats; no sex difference was observed in mice. α-Pinene was eliminated from blood with half-lives between 12.2 and 17.4 h in rats and 6.18-19.4 h in mice. At the low dose, the ratio of α-pinene oxide to α-pinene, based on Cmax and AUC, respectively, was 0.200-0.237 and 0.279-0.615 in rats and 0.060-0.086 and 0.036-0.011 in mice demonstrating lower formation of the oxide in mice than in rats. At the high dose, the ratio decreased considerably in both species pointing to saturation of pathways leading to the formation of α-pinene oxide. α-Pinene and the oxide were quantified in the mammary glands of rats and mice with tissue to blood ratios of ≥23 demonstrating retention of these analytes in mammary glands. The findings of epoxide formation and species- and sex-differences in systemic exposure may be important in providing context and relating animal findings to human exposures.

In Silico Approaches In Carcinogenicity Hazard Assessment: Current Status and Future Needs.

Historically, identifying carcinogens has relied primarily on tumor studies in rodents, which require enormous resources in both money and time. In silico models have been developed for predicting rodent carcinogens but have not yet found general regulatory acceptance, in part due to the lack of a generally accepted protocol for performing such an assessment as well as limitations in predictive performance and scope. There remains a need for additional, improved in silico carcinogenicity models, especially ones that are more human-relevant, for use in research and regulatory decision-making. As part of an international effort to develop in silico toxicological protocols, a consortium of toxicologists, computational scientists, and regulatory scientists across several industries and governmental agencies evaluated the extent to which in silico models exist for each of the recently defined 10 key characteristics (KCs) of carcinogens. This position paper summarizes the current status of in silico tools for the assessment of each KC and identifies the data gaps that need to be addressed before a comprehensive in silico carcinogenicity protocol can be developed for regulatory use.

Harnessing In Silico, In Vitro, and In Vivo Data to Understand the Toxicity Landscape of Polycyclic Aromatic Compounds (PACs).

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.