Improving environmental risk assessments of chemicals: Steps towards evidence-based ecotoxicology

Perfluorooctanesulfonic acid (PFOS) induced cancer related DNA methylation alterations in human breast cells: A whole genome methylome study

DNA methylation plays a pivotal role in cancer. The ubiquitous contaminant perfluorooctanesulfonic acid (PFOS) has been epidemiologically associated with breast cancer, and can induce proliferation and malignant transformation of normal human breast epithelial cells (MCF-10A), but the information about its effect on DNA methylation is sparse. The aim of this study was to characterize the whole-genome methylome effects of PFOS in our breast cell model and compare the findings with previously demonstrated DNA methylation alterations in breast tumor tissues. The DNA methylation profile was assessed at single CpG resolution in MCF-10A cells treated with 1 μM PFOS for 72 h by using Enzymatic Methyl sequencing (EM-seq). We found 12,591 differentially methylated CpG-sites and 13,360 differentially methylated 100 bp tiles in the PFOS exposed breast cells. These differentially methylated regions (DMRs) overlapped with 2406 genes of which 494 were long non-coding RNA and 1841 protein coding genes. We identified 339 affected genes that have been shown to display altered DNA methylation in breast cancer tissue and several other genes related to cancer development. This includes hypermethylation of GACAT3, DELEC1, CASC2, LCIIAR, MUC16, SYNE1 and hypomethylation of TTN and KMT2C. DMRs were also found in estrogen receptor genes (ESR1, ESR2, ESRRG, ESRRB, GREB1) and estrogen responsive genes (GPER1, EEIG1, RERG). The gene ontology analysis revealed pathways related to cancer phenotypes such as cell adhesion and growth. These findings improve the understanding of PFOS's potential role in breast cancer and illustrate the value of whole-genome methylome analysis in uncovering mechanisms of chemical effects, identifying biomarker candidates, and strengthening epidemiological associations, potentially impacting risk assessment.

Incorporating a weight-of-evidence approach into a tiered assessment for chemicals management, with emphasis on program development and applications in developing countries and emerging economies

A flexible approach is described for incorporating a weight-of-evidence (WoE) methodology into a tiered ecological risk assessment (ERA)/management framework for chemicals. The approach is oriented toward informing decisions about chemicals. Communication is regarded as a critical component of the risk assessment process. The paper resulted from insights gained from seven ERA workshops held by SETAC (Society of Environmental Toxicology and Chemistry, www.setac.org) in the Asia-Pacific, African, and Latin American regions. Formal ERA methods are not fully developed or applied in many of these countries and assessments often begin with tables of risk values and test methods from countries where ERA is already implemented. While appropriate and sometimes necessary, workshop participants had questions about the reliability and relevance of using this information for regionally specific ecosystems with different receptors, fate processes, and exposure characteristics. The idea that an assessment of reliability and relevance of available information and the need for additional information was necessary at an early stage of the assessment process was considered. The judgment of reliability and relevance is central to WoE approaches along with the identification of information needs and the integration of such information. The need to engage in WoE considerations early and throughout the assessment process indicates that a tiered approach is appropriate for unifying the evaluation process in a consistent way from early screening-level steps to later more involved evaluations. The approach outlined in this article is complementary to WoE guidance developed by the Organization for Economic Co-operation and Development and many national guidance documents. To link assessments of risk to management decisions, emphasis is given to communications at each tier between the risk assessor (technical side) and the decision-makers (policy and regulatory side). Tools and information sources are suggested for each tier and suggestions are meant to be illustrative and not prescriptive. Integr Environ Assess Manag 2024;00:1-15. © 2024 SETAC.

Mechanism of up-regulated H2O2 BPA-derived production and production of (poly)phenols by two seaweeds of the genus Ulva

The present study provides information on the effects of BPA on ROS production-related phenomena in the chlorophytes Ulva rigida and U. intestinalis, and on the mechanism they establish against BPA toxicity, at environmentally relevant concentrations (0.1-3 μg L-1). Up-regulated H2O2 generation seems to be a key factor causing oxidative damage. Interspecific differences, in terms of the mechanism and the temporal response to BPA toxicity were observed. BPA effects on U. rigida were more intense and appeared earlier (on 1D at 0.1 μg L-1) compared to U. intestinalis and mostly after 7D (LOEC: 0.3 μg L-1, Terminal time, Tt: 7D). In U. rigida, on 1-5D, the 'mosaic' type effect patterns ('models' 3A/3B) with 'unaffected' and 'affected' areas (dark content, positive H2DCF-DA staining signal/H2O2 production and chlorophyll autofluorescence signal loss) indicated a time-dependent manner. After 7D, only U. rigida cells with dark content formed aggregates, showing positive H2O2 production ('model' 4) or in some cells oxidative damages triggering retrograde signaling in the neighboring 'unaffected' areas ('model' 5). H2O2 overproduction (CTCF ratio) in U. rigida, on 1D at the lowest concentration and after 7D at 0.3-1/3 μg L-1, respectively, seems to stimulate (poly)phenolic production, in a dose- and time-dependent manner. U. intestinalis did not display severe BPA impact (i.e., 'models' 4, 5) at any exposures, although at a later time indicated a lower LOEC (0.1 μg L-1, Tt: 9D) than that in U. rigida. In U. intestinalis, H2O2 production does not appear to stimulate high (poly)phenolic amounts.

Drivers of divergent assessments of bisphenol-A hazards to semen quality by various European agencies, regulators and scientists

The downward revision of the bisphenol A (BPA) Health-based Guidance Value (HBGV) by the European Food Safety Authority (EFSA) has led to disagreements with other regulatory agencies, among them the German Federal Institute for Risk Assessment (BfR). The BfR has recently published an alternative Tolerable Daily Intake (TDI), 1000-times higher than the EFSA HBGV of 0.2 ng/kg/d. While the EFSA value is defined in relation to immunotoxicity, the BfR alternative TDI is based on declines in sperm counts resulting from exposures in adulthood. Earlier, we had used semen quality deteriorations to estimate a BPA Reference Dose (RfD) of 3 ng/kg/d for use in mixture risk assessments of male reproductive health. We derived this estimate from animal studies of gestational BPA exposures which both EFSA and BfR viewed as irrelevant for human hazard characterisations. Here, we identify factors that drive these diverging views. We find that the fragmented, endpoint-oriented study evaluation system used by EFSA and BfR, with its emphasis on data that can support dose-response analyses, has obscured the overall BPA effect pattern relevant to male reproductive effects. This has led to a disregard for the effects of gestational BPA exposures. We also identify problems with the study evaluation schemes used by EFSA and BfR which leads to the omission of entire streams of evidence from consideration. The main driver of the diverging views of EFSA and BfR is the refusal by BfR to accept immunotoxic effects as the basis for establishing an HBGV. We find that switching from immunotoxicity to declines in semen quality as the basis for deriving a BPA TDI by deterministic or probabilistic approaches produces values in the range of 2.4-6.6 ng/kg/d, closer to the present EFSA HBGV of 0.2 ng/kg/d than the BfR TDI of 200 ng/kg/d. The proposed alternative BfR value is the result of value judgements which erred on the side of disregarding evidence that could have supported a lower TDI. The choices made in terms of selecting key studies and methods for dose-response analyses produced a TDI that comes close to doses shown to produce effects on semen quality in animal studies and in human studies of adult BPA exposures.

Recommendations to reduce the streetlight effect and gray areas limiting the knowledge of the effects of plant protection products on biodiversity

Preserving biodiversity against the adverse effects of plant protection products (PPPs) is a major environmental and societal issue. However, despite intensive investigation into the ecotoxicological effects of PPPs, the knowledge produced remains fragmented given the sheer diversity of PPPs. This is due, at least in part, to a strong streetlight effect in the field of ecotoxicology. Indeed, while some PPPs have been investigated in numerous ecotoxicological studies, there are many for which the scientific literature still has little or no information on their ecotoxicological risks and effects. The PPPs under the streetlight include a large variety of legacy substances and a more limited number of more recent or currently-in-use substances, such as the herbicide glyphosate and the neonicotinoid insecticides. Furthermore, many of the most recent PPPs (including those used in biocontrol) and PPP transformation products (TPs) resulting from abiotic and/or biotic degradation are rarely addressed in the international literature in the field of ecotoxicology. Here, based on a recent collective scientific assessment of the effects of PPPs on biodiversity and ecosystem services in the French and European contexts, this article sets out to illustrate the limitations and biases caused by the streetlight effect and numbers of gray areas, and issue recommendations on how to overcome them.

Frameworks for screening and risk management of chemicals and advanced materials: A critical review

Despite the evolution over the last half century of regulatory programs and frameworks developed for the evaluation of safety and management of risks associated with chemicals and materials, new and emerging contaminant issues continue to be identified. These recurring issues suggest a need for review and reflection on current approaches and strategies for ensuring the safety of chemicals and materials. Twelve existing frameworks relating to the evaluation and management of chemical or material risk were reviewed to identify potential process improvements for facilitating early identification of potentially problematic substances and better inform risk management strategies (e.g., prohibition, restricted use, or selection of safer alternatives). The frameworks were selected to represent a broad spectrum of regional, national, and international authorities and purposes, including preproduction evaluation of new substances, classification and hazard communication, identification of persistent pollutants, and identification of safer alternatives. Elements common to the frameworks were identified, as well as features unique to select frameworks. A comparative evaluation was performed, and potential new strategies and approaches were identified to inform process improvement recommendations. These recommendations include requiring validated analytical procedures to enable measurement in environmental media, improved data transparency and accessibility, flexibility to incorporate advances into the state of the practice (e.g., new approach methodologies and high-throughput assessment tools), and incorporation of monitoring and adaptive management strategies to enable more timely intervention. Process improvement recommendations are discussed and summarized in a conceptual risk management framework. Integr Environ Assess Manag 2023;19:1192-1206. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Transcriptional Responses as Biomarkers of General Toxicity: A Systematic Review and Meta-analysis on Metal-Exposed Bivalves

Through a systematic review and a series of meta-analyses, we evaluated the general responsiveness of putative transcriptional biomarkers of general toxicity and chemical stress. We targeted metal exposures performed on bivalves under controlled laboratory conditions and selected six transcripts associated with general toxicity for evaluation: catalase, glutathione-S-transferase, heat shock proteins 70 and 90, metallothionein, and superoxide dismutase. Transcriptional responses (n = 396) were extracted from published scientific articles (k = 22) and converted to log response ratios (lnRRs). By estimating toxic units, we normalized different metal exposures to a common scale, as a proxy of concentration. Using Bayesian hierarchical random effect models, we then tested the effects of metal exposure on lnRR, both for metal exposure in general and in meta-regressions using toxic unit and exposure time as independent variables. Corresponding analyses were also repeated with transcript and tissue as additional moderators. Observed patterns were similar for general and for transcript- and tissue-specific responses. The expected overall response to arbitrary metal exposure was an lnRR of 0.50, corresponding to a 65% increase relative to a nonexposed control. However, when accounting for publication bias, the estimated "true" response showed no such effect. Furthermore, expected response magnitude increased slightly with exposure time, but there was little support for general monotonic concentration dependence with regard to toxic unit. Altogether, the present study reveals potential limitations that need consideration prior to applying the selected transcripts as biomarkers in environmental risk assessment. Environ Toxicol Chem 2023;42:628-641. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Renewing and improving the environmental risk assessment of chemicals

The processes underpinning the environmental risk assessment (ERA) of chemicals have not changed appreciably in the last 30 years. It is unclear how successful these processes are in protecting the environment from any adverse effects of chemicals. To ascertain if the current methodology can be improved, and if so, how, we invited experts to suggest how the current ERA process could be improved. They were not asked to select from a list of suggestions. The 36 experts made 109 suggestions for improvement, which could be grouped into 33 categories. The category that received the most support, from 12 experts, was to utilise a broader range of scientific information, including all up-to-date information, in ERAs. The second most popular category, supported by 10 experts, was the suggestion to regulate mixtures of chemicals; the current regulatory process involves chemical-by-chemical assessment. Two quite radical proposals were suggested. One was to replace the regulator with artificial intelligence. The other was to establish a new competent authority that would appoint groups of experts, each including representatives of the range of stakeholders, to decide which studies were required, commission those studies, then conduct the ERA based on the results of those studies. These two radical proposals, which the authors support strongly, are not necessarily mutually exclusive. We conclude that the present ERA process could be improved to better protect the environment from the myriad of chemicals in use.

Enhancing Scientific Support for the Stockholm Convention's Implementation: An Analysis of Policy Needs for Scientific Evidence

The Stockholm Convention is key to addressing the global threats of persistent organic pollutants (POPs) to humanity and the environment. It has been successful in identifying new POPs, but its national implementation remains challenging, particularly by low- and middle-income Parties. Concerted action is needed to assist Parties in implementing the Convention's obligations. This analysis aims to identify and recommend research and scientific support needed for timely implementation of the Convention. We aim this analysis at scientists and experts from a variety of natural and social sciences and from all sectors (academia, civil society, industry, and government institutions), as well as research funding agencies. Further, we provide practical guidance to scientists and experts to promote the visibility and accessibility of their work for the Convention's implementation, followed by recommendations for sustaining scientific support to the Convention. This study is the first of a series on analyzing policy needs for scientific evidence under global governance on chemicals and waste.

Accelerating the pace of ecotoxicological assessment using artificial intelligence

Species Sensitivity Distribution (SSD) is a key metric for understanding the potential ecotoxicological impacts of chemicals. However, SSDs have been developed to estimate for only handful of chemicals due to the scarcity of experimental toxicity data. Here we present a novel approach to expand the chemical coverage of SSDs using Artificial Neural Network (ANN). We collected over 2000 experimental toxicity data in Lethal Concentration 50 (LC50) for 8 aquatic species and trained an ANN model for each of the 8 aquatic species based on molecular structure. The R2 values of resulting ANN models range from 0.54 to 0.75 (median R2 = 0.69). We applied the predicted LC50 values to fit SSD curves using bootstrapping method, generating SSDs for 8424 chemicals in the ToX21 database. The dataset is expected to serve as a screening-level reference SSD database for understanding potential ecotoxicological impacts of chemicals.

Investigating endocrine-disrupting properties of chemicals in fish and amphibians: Opportunities to apply the 3Rs

Many regulations are beginning to explicitly require investigation of a chemical's endocrine-disrupting properties as a part of the safety assessment process for substances already on or about to be placed on the market. Different jurisdictions are applying distinct approaches. However, all share a common theme requiring testing for endocrine activity and adverse effects, typically involving in vitro and in vivo assays on selected endocrine pathways. For ecotoxicological evaluation, in vivo assays can be performed across various animal species, including mammals, amphibians, and fish. Results indicating activity (i.e., that a test substance may interact with the endocrine system) from in vivo screens usually trigger further higher-tier in vivo assays. Higher-tier assays provide data on adverse effects on relevant endpoints over more extensive parts of the organism's life cycle. Both in vivo screening and higher-tier assays are animal- and resource-intensive and can be technically challenging to conduct. Testing large numbers of chemicals will inevitably result in the use of large numbers of animals, contradicting stipulations set out within many regulatory frameworks that animal studies be conducted as a last resort. Improved strategies are urgently required. In February 2020, the UK's National Centre for the 3Rs and the Health and Environmental Sciences Institute hosted a workshop ("Investigating Endocrine Disrupting Properties in Fish and Amphibians: Opportunities to Apply the 3Rs"). Over 50 delegates attended from North America and Europe, across academia, laboratories, and consultancies, regulatory agencies, and industry. Challenges and opportunities in applying refinement and reduction approaches within the current animal test guidelines were discussed, and utilization of replacement and/or new approach methodologies, including in silico, in vitro, and embryo models, was explored. Efforts and activities needed to enable application of 3Rs approaches in practice were also identified. This article provides an overview of the workshop discussions and sets priority areas for follow-up. Integr Environ Assess Manag 2022;18:442-458. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Environmental concentrations of Roundup in combination with chlorpromazine or heating causes biochemical disturbances in the bivalve mollusc Unio tumidus

Bivalve molluscs represent the most recognized bioindicators of freshwater pollution. However, their ability to indicate specific xenobiotics in complex exposures is unclear. In this study, we aimed to track the particular effects of the pesticide Roundup (Rnd) and the antipsychotic drug chlorpromazine (Cpz) on the mussel Unio tumidus at the simpler environmentally relevant models. We treated the mussels by Rnd (17 μg L-1), Cpz (18 μg L-1), the mixture of Rnd and Cpz at 18 °C (RndCpz), and Rnd at 25 °C (RndT) and examined their digestive glands after 14 days of exposure. We analyzed total antioxidant capacity, glutathione (GSH&GSSG) and protein carbonyls levels, total and Zn-related concentrations of metallothioneins (MT and Zn-MT, respectively), the activities of CYP450-related EROD, glutathione S-transferase, cholinesterase, caspase-3, citrate synthase (CS), lysosomal membrane integrity (NRR), and Zn level in the tissue. Shared responses were indicated as the increase of the antioxidant, Zn-MT, and EROD levels, whereas the changes of Zn concentration, NRR, and caspase-3 activity were most diverse compared to control. According to discriminant analysis, complex exposures abolished the individual response traits and intensified the harmful effects that caused a decrease in the Zn level in the RndCpz- and RndT-groups and the loss of lysosomal integrity in the RndT-group. We concluded that multi-marker expertise with the application of integrated indices had benefits when evaluating the effects of complex exposures.

Coral Ecotoxicological Data Evaluation for the Environmental Safety Assessment of Ultraviolet Filters

There is growing interest in the environmental safety of ultraviolet (UV) filters found in cosmetic and personal care products (CPCPs). The CPCP industry is assessing appropriate environmental risk assessment (ERA) methods to conduct robust environmental safety assessments for these ingredients. Relevant and reliable data are needed for ERA, particularly when the assessment is supporting regulatory decision-making. In the present study, we apply a data evaluation approach to incorporate nonstandard toxicity data into the ERA process through an expanded range of reliability scores over commonly used approaches (e.g., Klimisch scores). The method employs an upfront screening followed by a data quality assessment based largely on the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) approach. The method was applied in a coral case study in which UV filter toxicity data was evaluated to identify data points potentially suitable for higher tier and/or regulatory ERA. This is an optimal case study because there are no standard coral toxicity test methods, and UV filter bans are being enacted based on findings reported in the current peer-reviewed data set. Eight studies comprising nine assays were identified; four of the assays did not pass the initial screening assessment. None of the remaining five assays received a high enough reliability score (R_n ) to be considered of decision-making quality (i.e., R1 or R2). Four assays were suitable for a preliminary ERA (i.e., R3 or R4), and one assay was not reliable (i.e., R6). These results highlight a need for higher quality coral toxicity studies, potentially through the development of standard test protocols, to generate reliable toxicity endpoints. These data can then be used for ERA to inform environmental protection and sustainability decision-making. Environ Toxicol Chem 2021;40:3441-3464. © 2021 Personal Care Products Council. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Open Science in regulatory environmental risk assessment

A possible way to alleviate the public skepticism toward regulatory science is to increase transparency by making all data and value judgments used in regulatory decision making accessible for public interpretation, ideally early on in the process, and following the concepts of Open Science. This paper discusses the opportunities and challenges in strengthening Open Science initiatives in regulatory environmental risk assessment (ERA). In this discussion paper, we argue that the benefits associated with Open Science in regulatory ERA far outweigh its perceived risks. All stakeholders involved in regulatory ERA (e.g., governmental regulatory authorities, private sector, academia, and nongovernmental organizations), as well as professional organizations like the Society of Environmental Toxicology and Chemistry, can play a key role in supporting the Open Science initiative, by promoting the use of recommended reporting criteria for reliability and relevance of data and tools used in ERA, and by developing a communication strategy for both professionals and nonprofessionals to transparently explain the socioeconomic value judgments and scientific principles underlying regulatory ERA. Integr Environ Assess Manag 2021;17:1229-1242. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

A Method to Screen for Consistency of Effect in Laboratory Toxicity Tests: A Case Study with Anurans and the Herbicide Atrazine

This paper presents a semiquantitative method to help ecotoxicologists evaluate the consistency of data within the available peer-reviewed literature. In this case study, we queried whether there is consistent evidence of direct toxicity in Anurans exposed to atrazine at concentrations ≤ 100 μg/L under laboratory conditions. Atrazine was selected because of the relatively large repository of Anuran toxicity data. To accomplish this, we interrogated available data found in recent quantitative weight-of-evidence risk assessments for atrazine with a series of yes or no questions developed a priori. The questions examined consistency of reported effects within and between studies, within and between species, and across a wide range of endpoints categories (e.g., survivorship, growth and development, reproduction). The analysis found no compelling evidence of a consistent direct effect in Anurans around growth and development, reproduction, or survivorship at concentrations of up to at least 100 μg/L atrazine in laboratory studies. Further work is needed to refine the approach, including accounting for the magnitude of the reported effects. However, we recommend that ecotoxicologists employ some method of formal consistency of effects assessment method routinely before performing toxicity tests, in the contextualizing of new data, and in reviews of contaminants.

Issues, challenges, directives, and limitations concerning the improvement of environmental risk assessment of pharmaceutically active compounds

Nowadays, when tons of different chemicals including pharmaceutically active compounds (PhACs) are known to be released into the environment, applying adequate risk assessment relating to the protection of the ecosystem is very important. A broad body of scientific papers expresses a growing demand for improvement of the method(s) for ecological/environmental risk assessment (ERA). Although certain issues about ERA often emerge in the community, most of them cannot be considered as real problems and its methodology was developed keeping several limitations in mind. Nevertheless, the current approaches can be improved in order to better serve the intended purposes. For example, there is a lack of an integrated, manageable ecotoxicological database. It is not uncommon for basic, but extremely important, influencing factors such as time of exposure, interactions between different compounds, and characteristics of different habitats to be ignored. Discussing under the basic regulatory framework used in the EU, this correspondence paper deals with these and other examples to present the current features of ERA, identify gaps in process and application, and propose possible improvements/directives.

Evaluation of the spatiotemporal effects of bisphenol A on the leaves of the seagrass Cymodocea nodosa

The organic pollutant bisphenol A (BPA) causes adverse effects on aquatic biota. The present study explored the toxicity mechanism of environmentally occurring BPA concentrations (0.03-3 μg L^-1) on the seagrass Cymodocea nodosa intermediate leaf photosynthetic machinery. A "mosaic" type BPA effect pattern was observed, with "unaffected" and "affected"" leaf areas. In negatively affected leaf areas cells had a dark appearance and lost their chlorophyll auto-fluorescence, while hydrogen peroxide (H₂O₂) content increased time-dependently. In the "unaffected" leaf areas, cells exhibited increased phenolic compound production. At 1 μg L^-1 of BPA exposure, there was no effect on the fraction of open reaction centers (q_P) compared to control and also no significant effect on the quantum yield of non-regulated non-photochemical energy loss in PSII (Φ_ΝΟ). However, a 3 μg L^-1 BPA application resulted in a significant Φ_ΝΟ increase, even from the first exposure day. Ultrastructural observations revealed electronically dense damaged thylakoids in the plastids, while effects on Golgi dictyosomes and the endoplasmic reticulum were also observed at 3 μg L^-1 BPA. The up-regulated H₂O₂ BPA-derived production seems to be a key factor causing both oxidative damages but probably also triggering retrograde signalling, conferring tolerance to BPA in the "unaffected" leaf areas.

Pharmacology-informed prediction of the risk posed to fish by mixtures of non-steroidal anti-inflammatory drugs (NSAIDs) in the environment

The presence of non-steroidal anti-inflammatory drugs (NSAIDs) in the aquatic environment has raised concern that chronic exposure to these compounds may cause adverse effects in wild fish populations. This potential scenario has led some stakeholders to advocate a stricter regulation of NSAIDs, especially diclofenac. Considering their global clinical importance for the management of pain and inflammation, any regulation that may affect patient access to NSAIDs will have considerable implications for public health. The current environmental risk assessment of NSAIDs is driven by the results of a limited number of standard toxicity tests and does not take into account mechanistic and pharmacological considerations. Here we present a pharmacology-informed framework that enables the prediction of the risk posed to fish by 25 different NSAIDs and their dynamic mixtures. Using network pharmacology approaches, we demonstrated that these 25 NSAIDs display a significant mechanistic promiscuity that could enhance the risk of target-mediated mixture effects near environmentally relevant concentrations. Integrating NSAIDs pharmacokinetic and pharmacodynamic features, we provide highly specific predictions of the adverse phenotypes associated with exposure to NSAIDs, and we developed a visual multi-scale model to guide the interpretation of the toxicological relevance of any given set of NSAIDs exposure data. Our analysis demonstrated a non-negligible risk posed to fish by NSAID mixtures in situations of high drug use and low dilution of waste-water treatment plant effluents. We anticipate that this predictive framework will support the future regulatory environmental risk assessment of NSAIDs and increase the effectiveness of ecopharmacovigilance strategies. Moreover, it can facilitate the prediction of the toxicological risk posed by mixtures via the implementation of mechanistic considerations and could be readily extended to other classes of chemicals.

Key Opportunities to Replace, Reduce, and Refine Regulatory Fish Acute Toxicity Tests

Fish acute toxicity tests are conducted as part of regulatory hazard identification and risk-assessment packages for industrial chemicals and plant protection products. The aim of these tests is to determine the concentration which would be lethal to 50% of the animals treated. These tests are therefore associated with suffering in the test animals, and Organisation for Economic Co-operation and Development test guideline 203 (fish, acute toxicity) studies are the most widely conducted regulatory vertebrate ecotoxicology tests for prospective chemical safety assessment. There is great scope to apply the 3Rs principles-the reduction, refinement, and replacement of animals-in this area of testing. An expert ecotoxicology working group, led by the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research, including members from government, academia, and industry, reviewed global fish acute test data requirements for the major chemical sectors. The present study highlights ongoing initiatives and provides an overview of the key challenges and opportunities associated with replacing, reducing, and/or refining fish acute toxicity studies-without compromising environmental protection. Environ Toxicol Chem 2020;39:2076-2089. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

OECD approaches and considerations for regulatory evaluation of endocrine disruptors

Identifying the potential endocrine disruptor hazard of environmental chemicals is a regulatory mandate for many countries. However, due to the adaptive nature of the endocrine system, absence of a single method capable of identifying endocrine disruption, and the latency between exposure to endocrine disrupting chemical during sensitive life stages and the manifestation of adverse responses, satisfying the regulatory requirement needed to identify a chemical as an endocrine disruptor is a challenge. There are now a variety of validated regulatory tests that can be used in combination to provide evidence that a chemical affects the oestrogen, androgen, thyroid, and steroidogenic pathways of vertebrates, but most rely (at least to some extent) on animal testing and require considerable cost and time to produce the necessary data. Emerging research methods are able to evaluate other endocrine pathways, incorporate more sensitive endpoints, and combine multiple alternative methods to predict in vivo outcomes. Some research approaches may also bridge gaps that have been identified in current endocrine regulatory testing. For the near term, considering new endpoints in a regulatory context may require adding them to existing test methods in order to establish relationships between the traditional and the innovative. From the outset, endocrine testing has always required integration of multiple methods that provide data on different levels of biological organisation, thus, the area of endocrine disruption is particularly adaptable to adverse outcome pathway (AOP) frameworks and integrated test methods built around AOPs. Herein, we provide a review of the status of endocrine disruptors in the OECD context, examples where innovation from research is needed to improve or bridge gaps in endocrine testing, and suggestions for regulators and researchers to facilitate uptake of innovate methods for endocrine disruptor regulatory testing. The increase in several human complex human disorders that include an endocrine component and the alarming decrease in wildlife biodiversity are commanding directives to include the best, most informative, innovative approaches to accelerate the rate and throughput of chemical evaluation for endocrine disruption.