Use of new approach methodologies (NAMs) to meet regulatory requirements for the assessment of industrial chemicals and pesticides for effects on human health

In vitro to in vivo extrapolation modeling to facilitate the integration of transcriptomics data into genotoxicity assessment

In vitro transcriptomics holds promise for high-throughput, human-relevant data but is not yet integrated into regulatory decision-making due to the lack of standardized approaches. For genotoxicity assessment, transcriptomic biomarkers such as GENOMARK and TGx-DDI facilitate qualitative and quantitative analysis of complex in vitro transcriptomic datasets. However, advancing their use in quantitative testing requires standardized methods for deriving transcriptomic Points of Departure (tPoDs) and linking them to in vivo responses. Herein, we investigated different approaches to calculate tPoDs and applied in vitro to in vivo extrapolation to obtain administered equivalent doses (AEDs). Human HepaRG cells were exposed for 72 h to 10 known in vivo genotoxicants (glycidol, methyl methanesulfonate, nitrosodimethylamine, 4-nitroquinoline-N-oxide, aflatoxin B1, colchicine, cyclophosphamide, mitomycin C, ethyl methanesulfonate, and N-Nitroso-N-ethylurea) from the highest concentration that induces up to 50 % cytotoxicity through a range of lower concentrations. Gene expression data was generated using a customized version of the TempO-Seq® human S1500 + gene panel. The GENOMARK and TGx-DDI biomarkers produced genotoxic calls for all of these reference genotoxicants. Next, we performed benchmark concentration (BMC) modeling to generate both genotoxicity-specific biomarker (tPoDbiomarkers) and generic tPoDs (tPoD S1500+). High-throughput toxicokinetic models estimated the human AEDs for these tPoDs, which were compared with (a) previously reported genotoxicity-specific AEDs from other New Approach Methodologies, and (b) in vivo PoDs from animal studies. We found that the generic AEDs were more conservative than genotoxicity-specific biomarker AEDs. For six of the nine genotoxicants, transcriptomic AEDs were lower than the in vivo PoDs; refined kinetic models may improve predictions. Overall, in vitro transcriptomic data in HepaRG cells provide protective estimates of in vivo genotoxic concentrations, consistent with other in vitro genotoxicity testing systems.

Ethical principles for regulatory risk decision-making

Risk assessors, managers, and decision-makers are responsible for evaluating diverse human, environmental, and animal health risks. Although the critical elements of risk assessment and management are well-described in national and international documents, the ethical issues involved in risk decision-making have received comparatively little attention to date. To address this aspect, this article elaborates fundamental ethical principles designed to support fair, balanced, and equitable risk-based decision-making practices. Experts and global thinkers in risk, health, regulatory, and animal sciences were convened to share their lived experiences in relation to the intersection between risk science and analysis, regulatory science, and public health. Through a participatory and knowledge translation approach, an integrated risk decision-making model, with ethical principles and considerations, was developed and applied using diverse, contemporary risk decision-making and regulatory contexts. The ten principles - autonomy, minimize harm, maintain respect and trust, adaptability, reduce disparities, holistic, fair and just, open and transparent, stakeholder engagement, and One Health lens - demonstrate how public sector values and moral norms (i.e., ethics) are relevant to risk decision-making. We also hope these principles and considerations stimulate further discussion, debate, and an increased awareness of the application of ethics in identifying, assessing, and managing health risks.

Multi-behavioral fingerprints can identify potential modes of action for neuroactive environmental chemicals

There is a lack of confidence in the relevance of zebrafish-based behavior data for chemical risk assessment. We extended an automated Visual and Acoustic Motor Response (VAMR) new approach method (NAM) in 5-day post-fertilization (dpf) zebrafish to include 26, behavior-based endpoints that measure visual-motor responses, visual and acoustic startle responses, habituation learning, and memory retention. A correlation analysis from 5159 control larvae revealed that more complex endpoints for learning- and memory-related behavior yielded unique behavior patterns. To build confidence in the VAMR NAM, we established neuroactivity fingerprints using concentration-response profiles derived from 63 reference chemicals targeting neurotransmission, neurodevelopmental signaling, or toxicologically-relevant pathways. Hierarchical clustering revealed diverse toxicity fingerprints. Compounds that targeted the N-Methyl-D-aspartic acid (NMDA) or gamma-aminobutyric acid type A (GABAA) receptors reduced habituation learning. Pathway modulators targeting peroxisome proliferator-activated receptor delta (PPARδ) or gamma (PPARγ), GABAA, dopamine, ryanodine, aryl hydrocarbon (AhR), or G-protein-coupled receptors or the tyrosine kinase SRC inappropriately accelerated habituation learning. Reference chemicals targeting GABAA, NMDA, dopamine, PPARα, PPARδ, epidermal growth factor, bone morphogenetic protein, AhR, retinoid X, or α2-adreno receptors triggered inappropriate hyperactivity. Exposure to GABAA receptor antagonists elicited paradoxical excitation characterized by dark-phase sedation and increased startle responses while exposure to GABAA/B receptor agonists altered the same endpoints with opposite directionality. Relative to reference chemicals, environmental chemicals known to be GABA receptor antagonists (Lindane, Dieldrine) or agonists (Tetrabromobisphenol A (TBBPA)) elicited predicted behavior fingerprints. When paired with the phenotypically rich VAMR NAM, behavior fingerprints are a powerful approach to identify neuroactive chemicals.

Revisiting the approaches to DNA damage detection in genetic toxicology: insights and regulatory implications

Genetic toxicology is crucial for evaluating the potential risks of chemicals and drugs to human health and the environment. The emergence of high-throughput technologies has transformed this field, providing more efficient, cost-effective, and ethically sound methods for genotoxicity testing. It utilizes advanced screening techniques, including automated in vitro assays and computational models to rapidly assess the genotoxic potential of thousands of compounds simultaneously. This review explores the transformation of traditional in vitro and in vivo methods into computational models for genotoxicity assessment. By leveraging advances in machine learning, artificial intelligence, and high-throughput screening, computational approaches are increasingly replacing conventional methods. Coupling conventional screening with artificial intelligence (AI) and machine learning (ML) models has significantly enhanced their predictive capabilities, enabling the identification of genotoxicity signatures tied to molecular structures and biological pathways. Regulatory agencies increasingly support such methodologies as humane alternatives to traditional animal models, provided they are validated and exhibit strong predictive power. Standardization efforts, including the establishment of common endpoints across testing approaches, are pivotal for enhancing comparability and fostering consensus in toxicological assessments. Initiatives like ToxCast exemplify the successful incorporation of HTS data into regulatory decision-making, demonstrating that well-interpreted in vitro results can align with in vivo outcomes. Innovations in testing methodologies, global data sharing, and real-time monitoring continue to refine the precision and personalization of risk assessments, promising a transformative impact on safety evaluations and regulatory frameworks.

Genotoxicity in Unconventional Mammalian Models of Wild, Urban, and Agricultural Ecosystems: A Systematic Review Under the One Health Approach

Background/Objectives: This systematic review evaluates unconventional mammalian models from wild, agricultural, and urban/domestic ecosystems for genotoxicity assessment under the One Health framework. Non-human primates (NHPs), cattle, and domestic dogs are analyzed as sentinel species due to their distinct environmental niches, unique human interactions, and species-specific traits. In conjunction with this, evidence is presented about the in vitro use of cells of these mammals for the genotoxicological evaluation of different chemical substances, such as veterinary drugs, environmental pollutants, and pesticides. The synthesis focuses on standardized genetic toxicology assays (e.g., chromosomal aberrations, micronucleus, comet assay) aligned with Organization for Economic Cooperation and Development (OECD) guidelines. Methods: A structured search of international literature identified studies employing OECD-compliant genotoxicity assays in NHPs, cattle, dogs, and others not listed in OECD. Data was categorized by species, assay type, chemical class evaluated, environmental context (wild, agricultural, urban), and merits of the papers. Results: NHPs, despite their phylogenetic proximity to humans, show limited genotoxicity data in contrast to biomedical research, which has been constrained by ethical concerns and fieldwork logistics. Cattle emerge as robust models in agricultural settings due to the abundance of studies on the genotoxic capacity of pesticides, veterinary drug, and environmental biomonitoring, with direct implications for food safety. Domestic dogs are recognized as powerful sentinels for human health due to shared exposomes, physiological similarities (e.g., shorter cancer latency), and reduced lifestyle confounders; however, genotoxicity studies in dogs remain sparse compared to chemical exposure monitoring or cancer research. Conclusions: This review advocates for expanded, integrated use of these models to address genotoxic threats across ecosystems, which would benefit both animal and human health. In the application of biomonitoring studies with sentinel animals, a critical gap persists: the frequent lack of integration between xenobiotic quantification in environmental and biological samples, along with genotoxicity biomarkers evaluation in sentinel populations, which hinders comprehensive environmental risk assessment.

Impacts of Inorganic Arsenic Exposure on Genetic Stability of Human Mesenchymal Stromal Cells

Human mesenchymal stem/stromal cells (hMSCs) can differentiate into mesoderm-type cells, making them suitable candidates for tissue repair therapies. However, their relatively low frequency in adult tissue necessitates ex vivo expansion prior to regenerative medicine applications, and therefore, long-term hMSC genetic stability during expansion should be studied. hMSC applications in regenerative medicine ensure commercial availability of normal karyotype human primary cells for toxicity assessment and hMSCs could serve as alternatives to immortalized human cell models. In this work, we evaluated the potential of hMSCs in toxicity testing using inorganic arsenic (iAs) as a case study. hMSCs were exposed to iAs at different durations to track cellular aging and study long-term genetic stability. iAs exposures (48 h) resulted in micronuclei induction. hMSCs were also exposed to iAs for 6 days to determine if hMSCs would become more susceptible to chromosomal damage following exposure to the model genotoxicant, mitomycin C (MMC). The culture duration and iAs exposure did not alter MMC potency, indicating that the hMSC susceptibility to chromosomal damage remained unchanged. We also used gene expression analysis to investigate the molecular impacts of iAs on hMSCs over the course of short (3 days total) and long (30 days total) experiments. Both iAs exposures activated biomarkers associated with oxidative stress, but not biomarkers for direct DNA damage, providing support for an indirect mode of action for iAs genotoxicity. Overall, this study establishes the utility of hMSCs as a new model for toxicity screening and provides mechanistic information underlying iAs toxicity.

Next Generation Risk Assessment of Acute Neurotoxicity from Organophosphate Exposures Using the In Vitro-In Silico Derived Dietary Comparator Ratio

Organophosphate (OP) pesticides are common environmental contaminants, of which the resulting acetylcholinesterase (AChE) inhibition and concomitant neurotoxic effects following exposure remain a global concern. To evaluate the safety upon acute exposure to OP pesticides, the Dietary Comparator Ratio (DCR) approach was used for the first time for this class of chemicals. Six OPs including chlorpyrifos, diazinon, fenitrothion, methyl parathion, profenofos, and chlorfenvinphos were selected as model compounds. Seventy-four reports of human exposures were collected, and a DCR value at each defined exposure level was calculated with in vitro determined AChE inhibition potency and in silico simulated internal exposures. Results indicate that the DCR outcomes are comparable to the actual knowledge on the presence or absence of in vivo AChE inhibition and adverse effects for the respective exposure scenarios. Of all collected scenarios, only four false positives but no false negatives were obtained. No safety concern on acute neurotoxicity appears to be raised for the evaluated environmental exposure scenarios to OPs. To conclude, the described DCR approach provides an adequate evaluation of the OP-induced adverse outcomes for humans, shedding light on its utility for 3Rs-compliant safety assessment of chemicals with different toxicity mechanisms especially for which in vitro bioassays are available.

Accelerating Animal Replacement: How Universities Can Lead - Results of a One-Day Expert Workshop in Zurich, Switzerland

This report is a result of an interdisciplinary workshop held at the Collegium Helveticum in Zurich, Switzerland in February 2024, in which ideas for accelerating NAMs (New Approach Methodologies) in Swiss universities were shared and discussed. Due to regional differences in university organisation and funding structures, not all recommendations will be transferable to all regions worldwide. All participants were qualified to contribute to the discussion, due to their knowledge and experience of the Three Rs, in particular with regard to their implementation. The workshop participants believed that universities, which play a pioneering role in so many other areas, should also exploit their innovative potential in the field of animal-free research. The workshop uncovered four areas that would need to be addressed in order to achieve a significant change in university science culture and do more justice to the Three Rs, namely: language - innovative framing (pro-replacement framing in official university statements); knowledge transfer - communicating innovative findings in teaching (redirecting curriculum); change of values within science faculties; and structured implementation and well-coordinated planning of the transformation (establishment of a 'transition unit'). Specific strategies for implementing these four areas are outlined. In addition, we discuss why the replacement of animal testing should be an essential goal for universities, why this goal has not yet been achieved, and why concerted efforts toward change are required.

An Approach to Setting Vertebrate Animal-use Benchmarks for Agrochemical and GM Crop Testing to Facilitate Future Animal Reduction Efforts

Agrochemical active ingredients are among the most toxicologically evaluated chemical substances, and genetically modified (GM) crops must be evaluated for safety and nutritional adequacy. Traditionally, these evaluations are conducted in vivo. There are concerted efforts in the agrochemical sector to reduce animal testing, but there is also an emphasis on updating test guidelines and fulfilling new data package requirements, which can both result in increased animal testing. The purpose of this project was to generate benchmarks for the numbers of vertebrate animals used in: a) evaluating agrochemical pesticidal active ingredients for human health hazards; and b) assessing GM crops for safety and nutritional adequacy, based on guideline studies for data package requirements. To achieve this, guideline studies employing vertebrates, as required by regulatory bodies for developing global data packages for new active ingredients and for GM crops, were listed. These listed guideline studies were reviewed, in terms of the study details and the required animal-use, which was determined based on best testing practices. For historical animal-use benchmarking, Corteva's six most recent agrochemical pesticidal active ingredients and four most recent GM crop events were evaluated. Across the six most recently developed active ingredients, an average of approximately 10,000 mammals were used for the testing of each (range: 5500-19,000); across the four most recently developed GM crops, the average number of vertebrates similarly used for each was approximately 1200 (range: 1000-1500). Though regulatory testing requirements are likely to change with time, as new technologies become available, this project has established a theoretical minimum requirement to help drive aspirational animal reduction goals, identified regulatory challenges associated with the reduction of animal-use, and helped to refine Corteva's vertebrate animal-use tracking approaches.

Biological activity of natural 2-quinolinones

While natural products have undeniably played a crucial role in drug discovery, challenges such as limited availability and complex synthesis methods have hindered the identification of lead compounds. At the core of numerous natural and synthetic compounds, each displaying distinct biological behaviours, lies the foundational structure of 2-quinolinone. Compounds with this structural motif exhibit a broad range of effects in different tissues. Furthermore, specific members showcase therapeutic potential for various disorders. Despite the significance of these compounds, the current review literature has not provided a comprehensive overview, underscoring the essential contribution of this article in exploring their biological functions. This study examines the biological activity of selected 2-quinolinone alkaloids across diverse organisms, unveiling their potential as a source of innovative bioactive natural products.

Humanising nanotoxicology: replacement of animal-derived products in the application of integrated approaches to testing and assessment of nanomaterial inhalation hazard

Over the past decade, the development of nanomaterials (NMs) has surged, highlighting their potential benefits across multiple industries. However, concerns regarding human and environmental exposure remain significant. Traditional in vivo models for safety assessments are increasingly viewed as unfeasible and unethical due to the diverse forms and biological effects of NMs. This has prompted the design of Novel Approach Methods (NAMs) to streamline risk assessment and predict human hazards without relying on animal testing. A critical aspect of advancing NAMs is the urgent need to replace animal-derived products in assay protocols. Incorporating human or synthetic alternatives can significantly reduce the ethical burden of animal use while enhancing the relevance of toxicity testing. This study evaluates the impact of removing animal-derived products from standard acellular and in vitro assays recommended in a published Integrated Approaches to Testing and Assessment (IATA) for inhaled NMs. We specifically assessed the effects of replacing fetal bovine serum with human platelet lysate in acellular reactivity tests and in vitro toxicity testing using a panel of well-characterized NMs. Significant differences in acellular NM reactivity and dramatic changes in A549 cell growth rates and responses to NMs were observed under different media conditions. Our findings demonstrate that variations in experimental setup can fundamentally impact NM hazard assessment, influencing the interpretation of results within specific assays and across tiered testing strategies. Further investigation is needed to support a shift toward more ethical toxicity testing that does not rely on animal-derived materials.

Key attributes of health and environmental risk decision-making: A scoping review

Government agencies, international institutions, and independent experts have published approaches for the assessment and management of health and environmental risks. This includes evidence-based strategies and publications supporting risk decision-making frameworks reflecting contemporary practices, the overarching context, and governance structures for addressing known and emerging risk issues. This scoping review surveys the literature, over the last five decades, to identify key attributes of health and environmental risk decision-making and how these inherent characteristics are related to the overarching regulatory decision-making context. The findings provide insights on how these publications accounted for the circumstances and triggers at that time. This includes incorporating factors reflecting advances in science and technology, a better understanding of underlying values (e.g., societal), and an expansion in the scope and complexity required for conducting different evaluations relevant to health and environmental risks. Consequently, the evolution from linear to more expanded and holistic decision-making frameworks incorporates foundational elements, such as the well-established steps for assessing risks, while adding aspects reflecting transformative changes and paradigm shifts (e.g., the use of non-animal testing strategies for evaluating human safety). Our analysis also resulted in the generation of a consolidated listing of ten attributes: trigger/issue, regulatory context, regulatory factors, core values, risk decision-making principles, cross-cutting attributes, design (scope and steps), structure, decision-making pathway, and evidence-knowledge requirements for risk decision-making. A better understanding of this evolution in risk decision-making and the listing of key attributes will be used in future work aimed at developing considerations for next generation decision-making approaches for health and environmental risks.

Evaluating the toxicity of sea-dumped conventional and chemical munition degradation products to fish and human cells using a combination of cell viability assays

The disposal of munitions in marine coastal areas after World Wars I and II has raised significant concerns about environmental contamination and human health risks. This study investigates the acute cytotoxicity of munition-related chemicals commonly detected near marine dumpsites, focusing on degradation products of explosives and related compounds (E&RC) and degradation products of chemical warfare agents and related compounds (CWA&RC). The research examines three CWA&RC (1,4-oxathiane, 1,4-dithiane, thiodiglycol) and four E&RC (2,4,6-trinitrotoluene, tetryl, 1,3-dinitrobenzene, picric acid) using the RTgill-W1 cell line (rainbow trout gill cells) as a proxy for fish toxicity and human cell lines (Caco2 and HepG2) to model potential human exposure via contaminated seafood. The results indicate low acute cytotoxicity of CWA&RC, while E&RC exhibit significantly higher toxicity. Notably, the EC10 and EC50 values for tetryl and 1,3-DNB in RTgill-W1 align with concentrations detected near North American dumpsites, reflecting environmentally relevant conditions. The study also reveals inter-species and inter-organ variability in toxicity mechanisms, identifying potential adverse outcome pathways such as AOP 220. These findings highlight the need for further research into chronic exposure scenarios at environmentally realistic concentrations and contribute crucial data to understanding the risks posed by the degradation products of these chemicals to aquatic life and human health.

Enhancing toxicity prediction for natural products in herbal medicine and dietary supplements: Integrating (Q)STR models and in vitro assays

New approach methods (NAMs) are required to predict human toxicity effectively, particularly due to limitations in conducting in vivo studies. While NAMs have been established for various industries, such as cosmetics, pesticides, and drugs, their applications in natural products (NPs) are lacking. NPs' complexity (multiple ingredients and structural differences from synthetic compounds) complicates NAM development. In this study, we devised NAMs for NPs using (quantitative) structure-toxicity relationship (Q)STR models and in vitro assays. Validation involved testing each method with single compounds isolated from NPs. A linear regression model was developed for (Q)STR prediction (R2 on test set: 0.52), with an applicability domain analysis demonstrating its reliability across NPs. This model was applied to predict the LD50 range of species, aiding in the development of herbal medicine and dietary supplements. In vitro screening employed three reporter cell lines (AP-1, P53, and Nrf2), with Tox scores derived by integrating in silico and in vitro data. Nimbolide exhibited the highest Tox score, with experimental studies corroborating the accuracy and reliability of the predictions made via Tox score analysis. The findings of the study align well with the purpose, as the suggested NAMs, utilizing (Q)STR models and in vitro assays, provide a Tox score to efficiently prioritize NPs for herbal medicine and dietary supplements.

Quantifying the effect of human interindividual kinetic differences on the relative potency value for riddelliine N-oxide at low dose levels by a new approach methodology

Pyrrolizidine alkaloid N-oxides (PA-N-oxides) are predominant in plants and herbal foods, and are converted to pyrrolizidine alkaloids (PAs) upon consumption, leading to toxicity. The effect of interindividual kinetic differences on the relative potency values of PA-N-oxides compared to their PAs (REPPANO to PA) was studied, with riddelliine N-oxide (RIDO) and riddelliine (RID) as model compounds. In vitro kinetic data measured in incubations with 30 fecal and 25 liver S9 donor samples showed high variation across individuals, where the interindividual variability was captured with Bayesian multilevel regression. The distributions of influential PBK model parameters were used as input for physiologically based kinetic (PBK) modeling combined with Monte Carlo (MC) simulations to calculate the probability distribution of REPRIDO to RID values. At low dose levels, interindividual differences were shown to be a factor that influences the REPRIDO to RID value while neither dose nor endpoint used plays a role. The distribution of the REPRIDO to RID value ranged from 0.71 to 0.97 (95th percentile) with a mean value of 0.87. The approach described enables determination of interindividual REPPANO to PA values at low dose levels, which are not accessible in in vivo experiments quantifying the REPPANO to PAvalue.

Progress in toxicogenomics to protect human health

Toxicogenomics measures molecular features, such as transcripts, proteins, metabolites and epigenomic modifications, to understand and predict the toxicological effects of environmental and pharmaceutical exposures. Transcriptomics has become an integral tool in contemporary toxicology research owing to innovations in gene expression profiling that can provide mechanistic and quantitative information at scale. These data can be used to predict toxicological hazards through the use of transcriptomic biomarkers, network inference analyses, pattern-matching approaches and artificial intelligence. Furthermore, emerging approaches, such as high-throughput dose-response modelling, can leverage toxicogenomic data for human health protection even in the absence of predicting specific hazards. Finally, single-cell transcriptomics and multi-omics provide detailed insights into toxicological mechanisms. Here, we review the progress since the inception of toxicogenomics in applying transcriptomics towards toxicology testing and highlight advances that are transforming risk assessment.

Leveraging new approach methodologies: ecotoxicological modelling of endocrine disrupting chemicals to Danio rerio through machine learning and toxicity studies

New approach methodologies (NAMs) offer information tailored to the intended application while reducing the use of animals. NAMs aim to develop quantitative structure-activity relationship (QSAR) and quantitive-Read-Across structure-activity relationship (q-RASAR) models to predict and categorize the acute toxicity of known and unknown endocrine-disrupting chemicals (EDCs) against zebrafish. EDCs are a diverse group of toxic substances that disrupt the endocrine system of humans and animals. The q-RASAR model was constructed and verified using validation metrics (R2 = 0.886 and Q2 = 0.814) which found to be more reliable model compare to QSAR model. The substructure fingerprint was well-fitted for the classification model and it was validated using 10-fold average accuracy (Q = 86.88%), specificity (Sp = 88.89%), Matthew's correlation curve (MCC = 0.621) and receiver operating characteristics (ROC = 0.828). The dataset of unknown substances revealed that phenolphthalein (Php) exhibited a significant level of toxicity based on q-RASAR model. The docking and simulation study indicated that the computationally derived important features successfully bound to the target zebrafish sex hormone binding globulin (zfSHBG). The experimental LC50 value of 0.790 mg L-1 was very close to the predicted value of 0.763 mg L-1, which provides high confidence to the developed model.

New approach methodologies in human health risk assessment across European regulatory frameworks: Status quo, barriers and drivers for regulatory acceptance and use

The traditional approaches to chemical risk assessment for human health are continuously challenged by their limitations, such as validity concerns, societal pressure to use animal-free methods, and resource constraints. New Approach Methodologies (NAMs) are considered a promising avenue toward modernisation of chemical risk assessment practices but their implementation in practice has been slow. This article aims to investigate the perspectives of human health risk assessors on the status quo, barriers and drivers of the acceptance and use of NAMs across different regulatory frameworks. A mixed method design was applied: qualitative interviews (N = 19) and an online survey with human health risk assessors from industry, regulatory agencies/institutions and academia (N = 222). The results show heterogeneity in familiarity and use of specific NAMs (e.g., QSARs as well-known and used vs. -omics approaches that are seldom used), the risk assessors' background (e.g., industry vs. regulatory agencies and institutions vs. academia) and the application context (e.g., screening/prioritisation vs. hazard identification/characterisation). The identified barriers and drivers offer pointers for the future integration and acceptance of NAMs in regulatory risk assessment. For instance, guidance documents can facilitate the use of NAMs, showcasing successful examples that increase trust in the methods and thus, the risk assessors' confidence in using these methods. Among other things, the article highlights the importance of considering human health risk assessors' needs and prerequisites to foster bottom-up coordinated efforts and to ensure the success of top-down legal and institutional change to incorporate NAMs in regulatory risk assessment.

Young TPI: empowering animal-free science among the next- generation of scientists

Strategies emphasizing animal-free innovation are imperative for the contemporary and future scientific research. They not only address important ethical concerns, but also should directly improve research accuracy and reliability through redirecting scientific inquiry toward more reliable and translatable methodologies. Promotion and encouragement for use of animal-free innovations among the next-generation of scientists, alongside knowledge acquisition and training in the increased capabilities of novel technologies, are fundamental for advancing science and the welfare of animals used for scientific purposes. The Dutch government has promoted initiatives such as Transitie Proefdiervrije Innovatie (TPI) to make the public aware of the current situation. However, the transition towards animal-free innovations will span over more than two generations. In this context, Young TPI emerged as the-first-of-its-kind network comprising young professionals and students dedicated to revolutionizing scientific practices by catalyzing the shift towards animal-free research. Grounded on three pillars - collaboration, awareness-raising, and networking - Young TPI has evolved into a premier youth network in the Netherlands. Boasting over 270 members spanning Dutch 49 institutions, including biotechnology startups and pharmaceutical companies and universities, Young TPI harnesses the diverse expertise of its members to propel a sustainable, future-proof transition and to promote a continuous dialogue with a wide range of stakeholders. This manuscript describes the conception, establishment, and progress of Young TPI from its start to present, detailing its strategy for communication, activities, and funding mechanisms, and ongoing endeavors to enlist new members and forge strategic alliances in pursuit of its mission.

Trends and Challenges of the Modern Pathology Laboratory for Biopharmaceutical Research Excellence

Pathology, a fundamental discipline that bridges basic scientific discovery to the clinic, is integral to successful drug development. Intrinsically multimodal and multidimensional, anatomic pathology continues to be empowered by advancements in molecular and digital technologies enabling the spatial tissue detection of biomolecules such as genes, transcripts, and proteins. Over the past two decades, breakthroughs in spatial molecular biology technologies and advancements in automation and digitization of laboratory processes have enabled the implementation of higher throughput assays and the generation of extensive molecular data sets from tissue sections in biopharmaceutical research and development research units. It is our goal to provide readers with some rationale, advice, and ideas to help establish a modern molecular pathology laboratory to meet the emerging needs of biopharmaceutical research. This manuscript provides (1) a high-level overview of the current state and future vision for excellence in research pathology practice and (2) shared perspectives on how to optimally leverage the expertise of discovery, toxicologic, and translational pathologists to provide effective spatial, molecular, and digital pathology data to support modern drug discovery. It captures insights from the experiences, challenges, and solutions from pathology laboratories of various biopharmaceutical organizations, including their approaches to troubleshooting and adopting new technologies.

Transcriptomic characterization of 2D and 3D human induced pluripotent stem cell-based in vitro models as New Approach Methodologies for developmental neurotoxicity testing

The safety and developmental neurotoxicity (DNT) potential of chemicals remain critically understudied due to limitations of current in vivo testing guidelines, which are low throughput, resource-intensive, and hindered by species differences that limit their relevance to human health. To address these issues, robust New Approach Methodologies (NAMs) using deeply characterized cell models are essential. This study presents the comprehensive transcriptomic characterization of two advanced human-induced pluripotent stem cell (hiPSC)-derived models: a 2D adherent and a 3D neurosphere model of human neural progenitor cells (hiNPCs) differentiated up to 21 days. Using high-throughput RNA sequencing, we compared gene expression profiles of 2D and 3D models at three developmental stages (3, 14, and 21 days of differentiation). Both models exhibit maturation towards post-mitotic neurons, with the 3D model maturing faster and showing a higher prevalence of GABAergic neurons, while the 2D model is enriched with glutamatergic neurons. Both models demonstrate broad applicability domains, including excitatory and inhibitory neurons, astrocytes, and key endocrine and especially the understudied cholinergic receptors. Comparison with human fetal brain samples confirms their physiological relevance. This study provides novel in-depth applicability insights into the temporal and dimensional aspects of hiPSC-derived neural models for DNT testing. The complementary use of these two models is highlighted: the 2D model excels in synaptogenesis assessment, while the 3D model is particularly suited for neural network formation as observed as well in previous functional studies with these models. This research marks a significant advancement in developing human-relevant, high-throughput DNT assays for regulatory purposes.

Effect of the barrier function of stratum corneum and viable epidermis and dermis on the skin concentration of topically applied chemicals

Three-dimensional cultured skin (3D skin) models have been utilized for in vitro skin permeation tests to evaluate the skin permeation rate and local effects (efficacy and toxicity) of applied chemicals, particularly from the perspective of the 3Rs (reduction, replacement, refinement) approach. The steady-state concentration of applied chemicals at different depths in the viable epidermis and dermis (VED) is affected by their skin permeation parameters, such as permeability coefficient (Kp) and partition coefficient (K) from the donor solution to the skin of the chemicals. In the present study, the steady-state concentration of chemicals in the VED of EpiDerm 606X (EpiDerm) as representative of a 3D skin model were compared with hairless rat skin. The VED concentrations of chemicals in EpiDerm were higher than those in hairless rat skin when a model hydrophilic compound, antipyrine, and a model lipophilic compound, flurbiprofen, were applied, suggesting that the barrier functions of the VED against the whole skin were higher in EpiDerm than in hairless rat skin. When an ester compound, ethyl nicotinate, was applied, the VED concentration of nicotinic acid, a metabolite of ethyl nicotinate, was lower in EpiDerm than in hairless rat skin. These differences in the VED concentrations of applied chemicals might be related to false-positives and -negatives of topical effects evaluated with 3D skin models. It is important to pay particular attention to differences in VED concentration in 3D skin models and real skin when evaluating local efficacy and toxicity using 3D skin models.

Development of an iPSC-derived immunocompetent skin model for identification of skin sensitizing substances

The development of immunocompetent skin models marks a significant advancement in in vitro methods for detecting skin sensitizers while adhering to the 3R principles, which aim to reduce, refine, and replace animal testing. This study introduces for the first time an advanced immunocompetent skin model constructed entirely from induced pluripotent stem cell (iPSC)-derived cell types, including fibroblasts (iPSC-FB), keratinocytes (iPSC-KC), and fully integrated dendritic cells (iPSC-DC). To evaluate the skin model's capacity, the model was treated topically with a range of well-characterized skin sensitizers varying in potency. The results indicate that the iPSC-derived immunocompetent skin model successfully replicates the physiological responses of human skin, offering a robust and reliable alternative to animal models for skin sensitization testing, allowing detection of extreme and even weak sensitizers. By addressing critical aspects of immune activation and cytokine signaling, this model provides an ethical, comprehensive tool for regulatory toxicology and dermatological research.

Fifteen day repeat air: liquid Interface air-only exposures can cause respiratory epithelium injury in MucilAir™ nasal respiratory epithelial cells that parallels chemically induced cytotoxicity

New Approach Methodologies (NAMs) are being widely used to reduce, refine, and replace, animal use in studying toxicology. For respiratory toxicology, this includes in silico and in vitro alternatives using air:liquid interface (ALI) exposures to replace traditional in vivo inhalation studies. In previous studies using 1,3-dichloropropene (1,3-DCP), a 5-day 4 h repeat exposures of MucilAir™ nasal cell culture models caused, dose-dependent cytotoxicity, depletion of GSH, changes in differential gene expression and histopathological transitions in cellular morphology from pseudostratified columnar epithelium to squamous epithelium. In this report we attempted to extend these studies using 15-day 1,3-DCP 4 h exposures to using MucilAir™ nasal cultures as outlined by an US EPA recent task order (US EPA 2023). For the 15-day repeat exposure, there were severe histopathologic changes in the MucilAir™ nasal mock-treatment (air-only) VITROCELL® chamber controls compared to incubator controls preventing any further analysis. The histopathological transitions in cellular morphology from pseudostratified columnar epithelium to squamous epithelium observed in the air only control in this study and previously with 1,3-DCP in MucilAir™ nasal cultures is also a hallmark of chemically induced cytotoxic responses in vivo in the respiratory tract. Histopathology assessments of 3D respiratory tract models used in ALI exposures can provide the linkage between in vitro to in vivo outcomes as part of the validation efforts of ALI use in regulatory toxicology. This report indicates that importance of histopathological assessments of incubator and mock-treatment (air-only) controls from each ALI exposure experiment along with exposed cell based model.

Valifenalate-induced non-adverse thyroid changes via adaptive induction of uridine 5'-diphospho-glucuronosyltransferase (UGT) in the liver of dogs and rats but not humans

Some rat and dog toxicology studies with the fungicide valifenalate showed minimal, non-adverse thyroid changes, mostly above the maximum tolerated dose, and concomitantly with liver effects. This publication describes their mode of action (MOA), combining in vivo and new approach methodologies (NAMs), in a weight of evidence approach. Data demonstrate a MOA of liver enzyme induction via nuclear receptor CAR/PXR activation, increased thyroxine (T4) metabolism and elevated thyroid stimulating hormone (TSH) level, leading to thyroid follicular cell hypertrophy and increased thyroid weight. Non-human relevance of the MOA was demonstrated in in vitro cross species assays in rat, dog and human hepatocytes. Increased gene expression and activity of cytochrome P450s (CYPs) and uridine 5'-diphospho-glucuronosyltransferases (UGTs) were observed in rat and dog hepatocytes exposed to valifenalate, with increased T4 clearance and/or T4 glucuronidation/T4-UGT activity. Therefore, a causal relationship between increased liver enzyme induction and thyroid effects in dogs and rats is concluded. Rat hepatocytes were most sensitive, while valifenalate did not increase T4-UGT activity above 2-fold of vehicle control or T4 glucuronidation and T4 clearance in human hepatocytes. Consequently, valifenalate exposure in humans is unlikely to lead to decreased T4 levels, and subsequent thyroid and developmental neurotoxicity effects. Alternative human-relevant thyroid MOAs were excluded, i.e. inhibition of deiodinases (DIO), thyroperoxidase (TPO) or the sodium iodide symporter (NIS). Due to known species differences in thyroid homeostasis between humans and laboratory animals and, importantly, based on the presented data, this liver enzyme mediated MOA is considered not relevant for human hazard assessment.

The Critical Role of Commercial Analytical Reference Standards in the Control of Chemical Risks: The Case of PFAS and Ways Forward

BACKGROUND

Various countries have instituted risk governance measures to control and minimize the risks of chemicals at the national and international levels. Activities typically include risk assessment based on a) hazard and exposure assessments; b) setting limits on the production, use, and emissions of chemicals; c) enforcement of regulations; and d) monitoring the effectiveness of the measures taken. These steps largely depend on chemical analysis and access to pure chemical reference standards. However, except for specific highly regulated categories of chemicals, such reference standards often are not commercially available. This raises a critical question: Given the widespread lack of reference standards, is the current approach to governing chemicals adequate to protect humans and the environment from harm? If not, what measures could be taken to improve the situation?

OBJECTIVE

We outline how current chemical risk governance is hampered by the widespread lack of reference standards to produce the required scientific evidence. We also provide a list of recommendations for controlling chemical risks in the absence of reference standards.

DISCUSSION

We use per- and polyfluoroalkyl substances (PFASs), specifically the chemical C6O4 [perfluoro ([5-methoxy-1,3-dioxolan-4-yl]oxy) acetic acid], to illustrate how companies that produce chemicals can prevent access to reference standards. We argue that the very limited availability of reference standards undermines the ability of scientists to produce independent scientific evidence needed for chemical risk governance and, thereby, prevents society from protecting people and the environment against chemical pollution and its harms. Possible ways to improve the situation include a) guaranteeing access to chemical reference standards by creating a reference standards repository, b) redefining the level of confidence sufficient for regulatory action, c) providing alternative options for chemical identification and quantification when reference standards are not available, and d) considering, when no reference standards are available, regulation of chemicals by class rather than individually. https://doi.org/10.1289/EHP12331.

A web-based histology atlas for the freshwater sentinel species Daphnia magna

Daphnia are keystone species of freshwater habitats used as model organisms in ecology and evolutionary biology. Their small size, wide geographic distribution, and sensitivity to chemicals make them useful as environmental sentinels in regulatory toxicology and chemical risk assessment. Biomolecular (-omic) assessments of responses to chemical toxicity, which reveal detailed molecular signatures, become more powerful when correlated with other phenotypic outcomes (such as behavioral, physiological, or histopathological) for comparative validation and regulatory relevance. However, the lack of histopathology or tissue phenotype characterization of this species presently limits our ability to assess cellular mechanisms of toxicity. Here, we address the central concept that interpreting aberrant tissue phenotypes requires a basic understanding of species normal microanatomy. We introduce the female and male DaphniaHistology Reference Atlas (DaHRA) for the baseline knowledge of Daphnia magna microanatomy. We also include developmental stages of female D. magna in the atlas. This interactive web-based resource of adult D. magna features overlaid vectorized demarcation of anatomical structures whose labels comply with an anatomical ontology created for this atlas. We demonstrate the potential utility of DaHRA for toxicological investigations by presenting aberrant phenotypes of acetaminophen-exposed D. magna. We envision DaHRA to facilitate the future integration of molecular and phenotypic data from the scientific community as we seek to understand how genes, chemicals, and environment interactions determine organismal phenotype.

A critical review on the toxicological and epidemiological evidence integration for assessing human health risks to environmental chemical exposures

Toxicology and epidemiology are the two traditional public health scientific disciplines which can contribute to investigate harmful health effects of exposure to toxic substances. Several frameworks for integrating different lines of evidence were proposed since 2011, evolving based of the emergence of new methodologies and approaches. Through the comparison of various theoretical frameworks for evidence integration, we examined similarities, differences, strengths, and weaknesses to provide insights into potential directions for future research. We identified several key challenges of the integration approach to be applied to risk assessment. More specifically, collaboration within a multidisciplinary team of scientists, toxicologists, epidemiologists, and risk assessors, is strongly recommended to be aligned with key regulatory objectives and promote a harmonized approach. Moreover, literature search transparency and systematicity have to be ensured by following validated guidelines, developing parallel protocols for collecting epidemiological and toxicological evidence from various sources, including human, animal, and new approach methodologies (NAMs). Also, the adoption of tailored quality assessment tools is essential to grade the certainty in evidence. Lastly, we recommend the use of the Adverse Outcome Pathway framework to provide a structured understanding of toxicity mechanisms and allow the integration of human, animal, and NAMs data within a single framework.

Capturing Differential Quality of Experimental Evidence in a Predictive Quantum-Mechanical Model for Respiratory Sensitization

Asthma is of concern in occupational toxicology with significant public-health and economic costs. In the absence of benchmark in vivo and in vitro tests, the use of mechanistically sound in silico models is critical to inform hazard and to protect workers from exposure to potentially harmful substances. We recently reported on the computer-aided discovery and REdesign (CADRE) model for respiratory sensitization, which relies on a tiered structure of expert rules, molecular simulations, quantum-mechanics calculations and advanced statistics to accurately identify respiratory sensitizers from first principles. Here, we present an update to this model based on two years of testing in the pharmaceutical space, where we captured the heterogeneity of the underlying experimental evidence in two predictive tiers, thus allowing the practitioner to select an outcome based on their expert assessment of the data reliability and relevance. This user-based tuning of predictive models is critical for end points that lack consensus on what constitutes satisfactory evidence to support a decision in the handling of chemicals for occupational safety.

Towards characterization of cell culture conditions for reliable proteomic analysis: in vitro studies on A549, differentiated THP-1, and NR8383 cell lines

Proteomic investigations result in high dimensional datasets, but integration or comparison of different studies is hampered by high variances due to different experimental setups. In addition, cell culture conditions can have a huge impact on the outcome. This study systematically investigates the impact of experimental parameters on the proteomic profiles of commonly used cell lines-A549, differentiated THP-1 macrophage-like cells, and NR8383-for toxicity studies. The work focuses on analyzing the influence at the proteome level of cell culture setup involving different vessels, cell passage numbers, and post-differentiation harvesting time, aiming to improve the reliability of proteomic analyses for hazard assessment. Mass-spectrometry-based proteomics was utilized for accurate protein quantification by means of a label-free approach. Our results showed that significant proteome variations occur when cells are cultivated under different setups. Further analysis of these variations revealed their association to specific cellular pathways related to protein misfolding, oxidative stress, and proteasome activity. Conversely, the influence of cell passage numbers on the proteome is minor, suggesting a reliable range for conducting reproducible biological replicates. Notable, substantial proteome alterations occur over-time post-differentiation of dTHP-1 cells, particularly impacting pathways crucial for macrophage function. This finding is key for the interpretation of experimental results. These results highlight the need for standardized culture conditions in proteomic-based evaluations of treatment effects to ensure reliable results, a prerequisite for achieving regulatory acceptance of proteomics data.

High-throughput transcriptomics toxicity assessment of eleven data-poor bisphenol A alternatives

Bisphenol A (BPA), a widely used chemical in the production of plastics and epoxy resins, has garnered significant attention due to its association with adverse health effects, particularly its endocrine-disrupting properties. Regulatory measures aimed at reducing human exposure to BPA have led to a proliferation of alternative chemicals used in various consumer and industrial products. While these alternatives serve to reduce BPA exposure, concerns have arisen regarding their safety and potential toxicity as regrettable substitutes. Previous efforts have demonstrated that in vitro high-throughput transcriptomics (HTTr) studies can be used to assess the endocrine-disrupting potential of BPA alternatives, and this strategy produces transcriptomic points-of-departure (tPODs) that are protective of human health when compared to the PODs from traditional rodent studies. In this study, we used in vitro HTTr to assess the potential for toxicity of eleven data-poor legacy chemicals sharing structural similarities to BPA. Human breast cancer MCF-7 cells were exposed to BPA and 11 alternatives at concentrations ranging from 0.1 to 25 μM to assess toxicity. Analysis of global transcriptomic changes and a previously characterized estrogen receptor alpha (ERα) transcriptomic biomarker signature revealed that 9 of 11 chemicals altered gene expression relative to controls. One of the chemicals (2,4'-Bisphenol A) activated the ERα biomarker at the same concentration as BPA (i.e., 4,4'-BPA) but was deemed to be more potent as it induced global transcriptomic changes at lower concentrations. These results address data gaps in support of ongoing screening assessments to identify BPA alternatives with hazard potential and help to identify potential candidates that may serve as safer alternatives.

Chemical-Specific T Cell Tests Aim to Bridge a Gap in Skin Sensitization Evaluation

T cell activation is the final key event (KE4) in the adverse outcome pathway (AOP) of skin sensitization. However, validated new approach methodologies (NAMs) for evaluating this step are missing. Accordingly, chemicals that activate an unusually high frequency of T cells, as does the most prevalent metal allergen nickel, are not yet identified in a regulatory context. T cell reactivity to chemical sensitizers might be especially relevant in real-life scenarios, where skin injury, co-exposure to irritants in chemical mixtures, or infections may trigger the heterologous innate immune stimulation necessary to induce adaptive T cell responses. Additionally, cross-reactivity, which underlies cross-allergies, can only be assessed by T cell tests. To date, several experimental T cell tests are available that use primary naïve and memory CD4+ and CD8+ T cells from human blood. These include priming and lymphocyte proliferation tests and, most recently, activation-induced marker (AIM) assays. All approaches are challenged by chemical-mediated toxicity, inefficient or unknown generation of T cell epitopes, and a low throughput. Here, we summarize solutions and strategies to confirm in vitro T cell signals. Broader application and standardization are necessary to possibly define chemical applicability domains and to strengthen the role of T cell tests in regulatory risk assessment.

Mechanism-based toxicity screening of organophosphate flame retardants using Tox21 assays and molecular docking analysis

As brominated flame retardants are phased out and regulations on their use become stricter, concerns over organophosphate flame retardants (OPFRs) have increased due to their high production. In response, this study aimed to screen the potential toxicity of emerging OPFRs using in vitro Tox21 assays and in silico molecular docking analysis. For 48 OPFRs collected from the literature, we investigated their bioactivity with human nuclear receptors using Tox21 data, focusing on pathways related to endocrine disruption (ERs, AR), stress response (GR), energy homeostasis (PPARs, FXR), and detoxification (PXR, CAR). For OPFRs not tested in Tox21 assays, molecular docking simulations were performed to predict binding potential. Results showed that CAR/PXR and FXR had relatively high reactivity with diverse OPFRs, indicating potential molecular initiating events (MIEs). Among the 48 OPFRs, 28 interacted with one or more receptors, suggesting they may act as potential stressors of adverse outcome pathways (AOPs) leading to various human diseases. Aryl- and halogenated-OPFRs displayed higher bioactivity compared to alkyl-OPFRs. Additionally, as the logKow value and carbon number of OPFRs increased, their interaction with nuclear receptors also increased. These structure- and physicochemistry-dependent bioactivities provide insights for designing safer OPFRs to avoid regrettable substitutions. Of these prioritized OPFRs, 13 showed low oral points-of-departure (POD) values under 100 mg/kg/day. In contrast, the other 15 OPFRs lacked sufficient data or exhibited less severe toxicity, despite being predicted to be of high concern in our analysis. Since several OPFRs are commonly used in consumer products that can lead to daily human exposure, we suggest that these OPFRs have the potential to reveal undisclosed effects and should therefore undergo further assessment.

Building knowledge of NAMs through risk science

The 12th World Congress on Alternatives and Animal Use in the Life Sciences provided a platform for mobilizing and exchanging knowledge on the advancements in science and technology. It also provided an opportunity for experts to discuss how to accelerate the adoption of new strategies and tools. One of these recommendations advocated the need to bridge the gap between the next generation of scientists who have yet to learn about 'New Approach Methodologies' (NAMs) and the current generation of thought leaders who have pioneered the development and validation of these non-animal approaches to toxicological risk assessment. Consequently, a mini-course, held at Canada's University of Ottawa, was developed for students, aged 13-16 years, interested in learning about risk science and how NAMs can be used to inform human health risk assessment. This course also served as a platform for creating a virtual training roadmap, provided in this paper, thereby bringing this knowledge to a broader audience of learners who are establishing their careers in the field of risk science.

The new paradigm in animal testing - "3Rs alternatives"

Regulatory studies have revolutionised over time. Today, the focus has shifted from animal toxicity testing to non-animal for regulatory safety testing. This move is in line with the international 3Rs (Replacement, Reduction, and Refinement) principle and has also changed the regulator's perspective. The 3R principle has stimulated changes in policy, regulations, and new approaches to safety assessment in drug development in many countries. The 3Rs approach has led to the discovery and application of new technologies and more human-relevant in vitro approaches that minimise the use of animals including non-human primates, in research and improve animal welfare. In 2016, the European Medicines Agency published the Guidelines on the principles of regulatory acceptance of 3Rs testing approaches, followed by a conceptual paper in 2023 to align with current 3R standards. Additionally, the United States Food and Drug Administration passed new legislation in 2023 that no longer requires all new human drugs to be tested on animals, which will change the current testing paradigm. This review paper provides the adoption of the 3Rs and the current regulatory perspective regarding their implementation.

Occurrence of emerging contaminants in three river basins impacted by wastewater treatment plant effluents: Spatio-seasonal patterns and environmental risk assessment

The concern on the fate and distribution of contaminants of emerging concern (CECs) is a burning topic due to their widespread occurrence and potential harmful effects. Particularly, antibiotics have received great attention due to their implications in antimicrobial resistance occurrence. The impact of wastewater treatment plants (WWTP) is remarkable, being one of the main pathways for the introduction of CECs into aquatic systems. The combination of novel analytical methodologies and risk assessment strategies is a promising tool to find out environmentally relevant compounds posing major concerns in freshwater ecosystems impacted by those wastewater effluents. Within this context, a multi-target approach was applied in three Spanish river basins affected by different WWTP treated effluents for spatio-temporal monitoring of their chemical status. Solid phase extraction followed by ultra-high-performance liquid chromatography were used for the quantification of a large panel of compounds (n = 270), including pharmaceuticals and other consumer products, pesticides and industrial chemicals. To this end, water samples were collected in four sampling campaigns at three locations in each basin: (i) upstream from the WWTPs; (ii) WWTP effluent discharge points (effluent outfall); and (iii) downstream from the WWTPs (500 m downriver from the effluent outfall). Likewise, 24-h composite effluent samples from each of the WWTPs were provided in all sampling periods. First the occurrence and distribution of these compounds were assessed. Diverse seasonal trends were observed depending on the group of emerging compounds, though COVID-19 outbreak affected variations of certain pharmaceuticals. Detection frequencies and concentrations in effluents generally exceeded those in river samples and concentrations measured upstream WWTPs were generally low or non-quantifiable. Finally, risks associated with maximum contamination levels were evaluated using two different approaches to account for antibiotic resistance selection as well. From all studied compounds, 89 evidenced environmental risk on at least one occasion in this study.

Organoid intelligence for developmental neurotoxicity testing

The increasing prevalence of neurodevelopmental disorders has highlighted the need for improved testing methods to determine developmental neurotoxicity (DNT) hazard for thousands of chemicals. This paper proposes the integration of organoid intelligence (OI); leveraging brain organoids to study neuroplasticity in vitro, into the DNT testing paradigm. OI brings a new approach to measure the impacts of xenobiotics on plasticity mechanisms - a critical biological process that is not adequately covered in current DNT in vitro assays. Finally, the integration of artificial intelligence (AI) techniques will further facilitate the analysis of complex brain organoid data to study these plasticity mechanisms.

New approach methodologies (NAMs) for the in vitro assessment of cleaning products for respiratory irritation: workshop report

The use of in vitro new approach methodologies (NAMs) to assess respiratory irritation depends on several factors, including the specifics of exposure methods and cell/tissue-based test systems. This topic was examined in the context of human health risk assessment for cleaning products at a 1-day public workshop held on 2 March 2023, organized by the American Cleaning Institute® (ACI). The goals of this workshop were to (1) review in vitro NAMs for evaluation of respiratory irritation, (2) examine different perspectives on current challenges and suggested solutions, and (3) publish a manuscript of the proceedings. Targeted sessions focused on exposure methods, in vitro cell/tissue test systems, and application to human health risk assessment. The importance of characterization of assays and development of reporting standards was noted throughout the workshop. The exposure methods session emphasized that the appropriate exposure system design depends on the purpose of the assessment. This is particularly important given the many dosimetry and technical considerations affecting relevance and translation of results to human exposure scenarios. Discussion in the in vitro cell/tissue test systems session focused on the wide variety of cell systems with varying suitability for evaluating key mechanistic steps, such as molecular initiating events (MIEs) and key events (KEs) likely present in any putative respiratory irritation adverse outcome pathway (AOP). This suggests the opportunity to further develop guidance around in vitro cell/tissue test system endpoint selection, assay design, characterization and validation, and analytics that provide information about a given assay's utility. The session on applications for human health protection emphasized using mechanistic understanding to inform the choice of test systems and integration of NAMs-derived data with other data sources (e.g., physicochemical properties, exposure information, and existing in vivo data) as the basis for in vitro to in vivo extrapolation. In addition, this group noted a need to develop procedures to align NAMs-based points of departure (PODs) and uncertainty factor selection with current human health risk assessment methods, together with consideration of elements unique to in vitro data. Current approaches are described and priorities for future characterization of in vitro NAMs to assess respiratory irritation are noted.

Inhalation Toxicity Screening of Consumer Products Chemicals using OECD Test Guideline Data-based Machine Learning Models

This study aimed to screen the inhalation toxicity of chemicals found in consumer products such as air fresheners, fragrances, and anti-fogging agents submitted to K-REACH using machine learning models. We manually curated inhalation toxicity data based on OECD test guideline 403 (Acute inhalation), 412 (Sub-acute inhalation), and 413 (Sub-chronic inhalation) for 1709 chemicals from the OECD eChemPortal database. Machine learning models were trained using ten algorithms, along with four molecular fingerprints (MACCS, Morgan, Topo, RDKit) and molecular descriptors, achieving F1 scores ranging from 51 % to 91 % in test dataset. Leveraging the high-performing models, we conducted a virtual screening of chemicals, initially applying them to data-rich chemicals generally used in occupational settings to determine the prediction uncertainty. Results showed high sensitivity (75 %) but low specificity (23 %), suggesting that our models can contribute to conservative screening of chemicals. Subsequently, we applied the models to consumer product chemicals, identifying 79 as of high concern. Most of the prioritized chemicals lacked GHS classifications related to inhalation toxicity, even though they were predicted to be used in many consumer products. This study highlights a potential regulatory blind spot concerning the inhalation risk of consumer product chemicals while also indicating the potential of artificial intelligence (AI) models to aid in prioritizing chemicals at the screening level.

Aerosol exposure at air-liquid-interface (AE-ALI) in vitro toxicity system characterisation: Particle deposition and the importance of air control responses

Experimental systems allowing aerosol exposure (AE) of cell cultures at the air-liquid-interface (ALI) are increasingly being used to assess the toxicity of inhaled contaminants as they are more biomimetic than standard methods using submerged cultures, however, they require detailed characterisation before use. An AE-ALI system combining aerosol generation with a CULTEX® exposure chamber was characterised with respect to particle deposition and the cellular effects of filtered air (typical control) exposures. The effect of system parameters (electrostatic precipitator voltage, air flowrate to cells and insert size) on deposition efficiency and spatial distribution were investigated using ICP-MS and laser ablation ICP-MS, for an aerosol of CeO2 nanoparticles. Deposition varied with conditions, but appropriate choice of operating parameters produced broadly uniform deposition at suitable levels. The impact of air exposure duration on alveolar cells (A549) and primary small airway epithelial cells (SAECs) was explored with respect to LDH release and expression of selected genes. Results indicated that air exposures could have a significant impact on cells (e.g., cytotoxicity and expression of genes, including CXCL1, HMOX1, and SPP1) at relatively short durations (from 10 mins) and that SAECs were more sensitive. These findings indicate that detailed system characterisation is essential to ensure meaningful results.

Intuitive toxicology in the 21st century-Bridging the perspectives of the public and risk assessors in Europe

Three decades ago, several articles on the subjectivity in chemical risk judgments (i.e., labeled "intuitive toxicology") measured the divide between the public and toxicologists with different backgrounds regarding the validity of predicting health effects based on in vivo studies. Similar divides with impacts on societal discourse and chemical risk assessment practices might exist concerning alternative toxicity testing methods (i.e., in vitro and in silico). However, studies to date have focused either on the public's views of in vivo or stem cell testing or on experts' views of in vivo testing and potential alternatives (i.e., toxicologists and medical students), which do not allow for a direct investigation of potential divides. To fill this knowledge gap, we conducted two online surveys, involving members of the German-speaking public in Switzerland and European human health risk assessors, respectively. This article presents the results of these two surveys regarding the divide in the public's and risk assessors' perspectives on risk assessment based on in vivo, in vitro, and in silico testing. Particularly, the survey with the risk assessors highlights that, beyond scientific and regulatory barriers, alternatives to in vivo testing may encounter individual hurdles, such as higher uncertainty associated with them. Understanding and addressing these hurdles will be crucial to facilitate the integration of new approach methodologies into chemical risk assessment practices as well as a successful transition toward next-generation risk assessment, bringing us closer to a fit-for-purpose and more efficient regulatory landscape.

A High-Throughput Method for Quantifying Drosophila Fecundity

The fruit fly, Drosophila melanogaster, is an experimentally tractable model system that has recently emerged as a powerful "new approach methodology" (NAM) for chemical safety testing. As oogenesis is well conserved at the molecular and cellular level, measurements of Drosophila fecundity can be useful for identifying chemicals that affect reproductive health across species. However, standard Drosophila fecundity assays have been difficult to perform in a high-throughput manner because experimental factors such as the physiological state of the flies and environmental cues must be carefully controlled to achieve consistent results. In addition, exposing flies to a large number of different experimental conditions (such as chemical additives in the diet) and manually counting the number of eggs laid to determine the impact on fecundity is time-consuming. We have overcome these challenges by combining a new multiwell fly culture strategy with a novel 3D-printed fly transfer device to rapidly and accurately transfer flies from one plate to another, the RoboCam, a low-cost, custom-built robotic camera to capture images of the wells automatically, and an image segmentation pipeline to automatically identify and quantify eggs. We show that this method is compatible with robust and consistent egg laying throughout the assay period and demonstrate that the automated pipeline for quantifying fecundity is very accurate (r2 = 0.98 for the correlation between the automated egg counts and the ground truth). In addition, we show that this method can be used to efficiently detect the effects on fecundity induced by dietary exposure to chemicals. Taken together, this strategy substantially increases the efficiency and reproducibility of high-throughput egg-laying assays that require exposing flies to multiple different media conditions.

Seminar: Functional Exposomics and Mechanisms of Toxicity-Insights from Model Systems and NAMs

BACKGROUND

Significant progress has been made over the past decade in measuring the chemical components of the exposome, providing transformative population-scale frameworks in probing the etiologic link between environmental factors and disease phenotypes. While the analytical technologies continue to evolve with reams of data being generated, there is an opportunity to complement exposome-wide association studies (ExWAS) with functional analyses to advance etiologic search at organismal, cellular, and molecular levels.

OBJECTIVES

Exposomics is a transdisciplinary field aimed at enabling discovery-based analysis of the nongenetic factors that contribute to disease, including numerous environmental chemical stressors. While advances in exposure assessment are enhancing population-based discovery of exposome-wide effects and chemical exposure agents, functional screening and elucidation of biological effects of exposures represent the next logical step toward precision environmental health and medicine. In this work, we focus on the use, strategies, and prospects of alternative approaches and model systems to enhance the current human exposomics framework in biomarker search and causal understanding, spanning from bench-based nonmammalian organisms and cell culture to computational new approach methods (NAMs).

DISCUSSION

We visit the definition of the functional exposome and exposomics and discuss a need to leverage alternative models as opposed to mammalian animals for delineating exposome-wide health effects. Under the "three Rs" principle of reduction, replacement, and refinement, model systems such as roundworms, fruit flies, zebrafish, and induced pluripotent stem cells (iPSCs) are advantageous over mammals (e.g., rodents or higher vertebrates). These models are cost-effective, and cell-specific genetic manipulations in these models are easier and faster, compared to mammalian models. Meanwhile, in silico NAMs enhance hazard identification and risk assessment in humans by bridging the translational gaps between toxicology data and etiologic inference, as represented by in vitro to in vivo extrapolation (IVIVE) and integrated approaches to testing and assessment (IATA) under the adverse outcome pathway (AOP) framework. Together, these alternatives offer a strong toolbox to support functional exposomics to study toxicity and causal mediators underpinning exposure-disease links. https://doi.org/10.1289/EHP13120.

Advances on carbon nanomaterials and their applications in medical diagnosis and drug delivery

Carbon nanomaterials are indispensable due to their unique properties of high electrical conductivity, mechanical strength and thermal stability, which makes them important nanomaterials in biomedical applications and waste management. Limitations of conventional nanomaterials, such as limited surface area, difficulty in fine tuning electrical or thermal properties and poor dispersibility, calls for the development of advanced nanomaterials to overcome such limitations. Commonly, carbon nanomaterials were synthesized by chemical vapor deposition (CVD), laser ablation or arc discharge methods. The advancement in these techniques yielded monodispersed carbon nanotubes (CNTs) and allows p-type and n-type doping to enhance its electrical and catalytic activities. The functionalized CNTs showed exceptional mechanical, electrical and thermal conductivity (3500-5000 W/mK) properties. On the other hand, carbon quantum dots (CQDs) exhibit strong photoluminescence properties with high quantum yield. Carbon nanohorns are another fascinating type of nanomaterial that exhibit a unique structure with high surface area and excellent adsorption properties. These carbon nanomaterials could improve waste management by adsorbing pollutants from water and soil, enabling precise environmental monitoring, while enhancing wastewater treatment and drug delivery systems. Herein, we have discussed the potentials of all these carbon nanomaterials in the context of innovative waste management solutions, fostering cleaner environments and healthier ecosystems for diverse biomedical applications such as biosensing, drug delivery, and environmental monitoring.

Evaluating non-monotonic dose-response relationships in ecotoxicological risk assessment: A case study based on a systematic review of data on fluoxetine

The environmental presence of pharmaceuticals, including the antidepressant fluoxetine, has become a subject of concern. Numerous studies have revealed effects of fluoxetine at environmental concentrations. Some of these studies have reported non-monotonic dose-response curves (NMDRs), leading to discussion because of the inconsistent detection of subtle effects and lack of mechanistic understanding. Nevertheless, investigating NMDRs in risk assessment is important, because neglecting them could underestimate potential risks of chemicals at low levels of exposure. Identification and quantification of NMDRs in risk assessment remains challenging, particularly given the prevalence of single outliers and the lack of sound statistical analyses. In response, the European Food Safety Authority (Beausoleil et al., 2016) presented a framework delineating six checkpoints for the evaluation of NMDR datasets, offering a systematic method for their assessment. The present study applies this framework to the case study of fluoxetine, aiming to assess the weight-of-evidence for the reported NMDR relationships. Through a systematic literature search, 53 datasets were selected for analysis against the six checkpoints. The results reveal that while a minority of these datasets meet all checkpoints, a significant proportion (27%) fulfilled at least five. Notably, many studies did not meet checkpoint 3, which requires NMDRs to be based on more than a single outlier. Overall, the current study points out a number of studies with considerable evidence supporting the presence of NMDRs for fluoxetine, while the majority of studies lacks strong evidence. The suggested framework proved useful for analysing NMDRs in ecotoxicological studies, but it is still imperative to develop further understanding of their biological plausibility.

Complexin vitromodels positioned for impact to drug testing in pharma: a review

Recent years have seen the creation and popularization of various complexin vitromodels (CIVMs), such as organoids and organs-on-chip, as a technology with the potential to reduce animal usage in pharma while also enhancing our ability to create safe and efficacious drugs for patients. Public awareness of CIVMs has increased, in part, due to the recent passage of the FDA Modernization Act 2.0. This visibility is expected to spur deeper investment in and adoption of such models. Thus, end-users and model developers alike require a framework to both understand the readiness of current models to enter the drug development process, and to assess upcoming models for the same. This review presents such a framework for model selection based on comparative -omics data (which we term model-omics), and metrics for qualification of specific test assays that a model may support that we term context-of-use (COU) assays. We surveyed existing healthy tissue models and assays for ten drug development-critical organs of the body, and provide evaluations of readiness and suggestions for improving model-omics and COU assays for each. In whole, this review comes from a pharma perspective, and seeks to provide an evaluation of where CIVMs are poised for maximum impact in the drug development process, and a roadmap for realizing that potential.

Quantum-Mechanics Calculations Elucidate Skin-Sensitizing Pharmaceutical Compounds

Skin sensitization is a critical end point in occupational toxicology that necessitates the use of fast, accurate, and affordable models to aid in establishing handling guidance for worker protection. While many in silico models have been developed, the scarcity of reliable data for active pharmaceutical ingredients (APIs) and their intermediates (together regarded as pharmaceutical compounds) brings into question the reliability of these tools, which are largely constructed using publicly available nonspecialty chemicals. Here, we present the quantum-mechanical (QM) Computer-Aided Discovery and REdesign (CADRE) model, which was developed with the bioactive and structurally complex chemical space in mind by relying on the fundamentals of chemical interactions in key events (versus structural attributes of training-set data). Validated in this study on 345 APIs and intermediates, CADRE achieved 95% accuracy, sensitivity, and specificity and a combined 79% accuracy in assigning potency categories compared to the mouse local lymph node assay data. We show how historical outcomes from CADRE testing in the pharmaceutical space, generated over the past 10 years on ca. 2500 chemicals, can be used to probe the relationships between sensitization mechanisms (or the underlying chemical classes) and the probability of eliciting a sensitization response in mice of a given potency. We believe this information to be of value to both practitioners, who can use it to quickly screen and triage their data sets, as well as to model developers to fine-tune their structure-based tools. Lastly, we leverage our experimentally validated subset of APIs and intermediates to show the importance of dermal permeability on the sensitization potential and potency. We demonstrate that common physicochemical properties used to assess permeation, such as the octanol-water partition coefficient and molecular weight, are poor proxies for the more accurate energy-pair distributions that can be computed from mixed QM and classical simulations using model representations of the stratum corneum.

Evaluation of THP-1 and Jurkat Cell Lines Coculture for the In Vitro Assessment of the Effects of Immunosuppressive Substances

The strong appeal to reduce animal testing calls for the development and validation of in vitro, in chemico and in silico models that would replace the need for in vivo testing and ex vivo materials. A category that requires such new approach methods is the assessment of immunosuppression that can be induced by chemicals including environmental pollutants. To assess the immunosuppressive action on monocytes and lymphocytes, we mimicked the whole-blood cytokine-release assay by preparing an in vitro coculture of THP-1 and Jurkat cell lines. We optimised its activation and investigated the effects of known immunosuppressive drugs with different mechanisms of action on the release of proinflammatory cytokines. Decreased secretion of IL-8 was achieved by several immunosuppressive mechanisms and was therefore selected as an appropriate marker of immunosuppression. A set of environmentally occurring bisphenols, BPA, BPAP, BPP, BPZ, BPE, TCBPA and BPS-MAE, were then applied to the model and BPP and BPZ were found to act as potent immunosuppressants at micromolar concentrations.

Relevance and feasibility of principles for health and environmental risk decision-making

Globally, national regulatory authorities are both responsible and accountable for health and environmental decisions related to diverse products and risk decision contexts. These authorities provided regulatory oversight and expedited market authorizations of vaccines and other therapeutic products during the COVID-19 pandemic. Regulatory decisions regarding such products and situations depend upon well-established risk assessment and management steps. The underlying processes supporting such decisions were outlined in frameworks describing the complex interactions between factors including risk assessment and management steps as well as principles which help guide risk decision-making. In 2022, experts in risk science proposed a set of 10 guiding principles, further examining the intersection and utility of these principles using 10 diverse risk contexts, and inviting a broader discourse on the application of these principles in risk decision-making. To add to this information, Canadian regulatory practitioners responsible for evaluating health and environmental risks and establishing policies convened at a Health Canada workshop on Principles for Risk Decision-Making. This review reports the results derived from this interactive engagement and provides a first pragmatic analysis of the relevance, importance, and feasibility of such principles for health and environmental risk decision-making within the Canadian regulatory context.