New approach methodologies (NAMs): identifying and overcoming hurdles to accelerated adoption.

New approach methodologies (NAMs) can deliver improved chemical safety assessment through the provision of more protective and/or relevant models that have a reduced reliance on animals. Despite the widely acknowledged benefits offered by NAMs, there continue to be barriers that prevent or limit their application for decision-making in chemical safety assessment. These include barriers related to real and perceived scientific, technical, legislative and economic issues, as well as cultural and societal obstacles that may relate to inertia, familiarity, and comfort with established methods, and perceptions around regulatory expectations and acceptance. This article focuses on chemical safety science, exposure, hazard, and risk assessment, and explores the nature of these barriers and how they can be overcome to drive the wider exploitation and acceptance of NAMs. Short-, mid- and longer-term goals are outlined that embrace the opportunities provided by NAMs to deliver improved protection of human health and environmental security as part of a new paradigm that incorporates exposure science and a culture that promotes the use of protective toxicological risk assessments.

Risk assessment in the 21st century: where are we heading?

Reliance on animal tests for chemical safety assessment is increasingly being challenged, not only because of ethical reasons, but also because they procrastinate regulatory decisions and because of concerns over the transferability of results to humans. New approach methodologies (NAMs) need to be fit for purpose and new thinking is required to reconsider chemical legislation, validation of NAMs and opportunities to move away from animal tests. This article summarizes the presentations from a symposium at the 2022 Annual Congress of the British Toxicology Society on the topic of the future of chemical risk assessment in the 21st century. The symposium included three case-studies where NAMs have been used in safety assessments. The first case illustrated how read-across augmented with some in vitro tests could be used reliably to perform the risk assessment of analogues lacking data. The second case showed how specific bioactivity assays could identify an NAM point of departure (PoD) and how this could be translated through physiologically based kinetic modelling in an in vivo PoD for the risk assessment. The third case showed how adverse-outcome pathway (AOP) information, including molecular-initiating event and key events with their underlying data, established for certain chemicals could be used to produce an in silico model that is able to associate chemical features of an unstudied substance with specific AOPs or AOP networks. The manuscript presents the discussions that took place regarding the limitations and benefits of these new approaches, and what are the barriers and the opportunities for their increased use in regulatory decision making.

Challenges and opportunities for overcoming dog use in agrochemical evaluation and registration.

Progress in developing new tools, assays, and approaches to assess human hazard and health risk provides an opportunity to re-evaluate the necessity of dog studies for the safety evaluation of agrochemicals. A workshop was held where partic­ipants discussed the strengths and limitations of past use of dogs for pesticide evaluations and registrations. Opportunities were identified to support alternative approaches to answer human safety questions without performing the required 90-day dog study. Development of a decision tree for determining when the dog study might not be necessary to inform pesticide safety and risk assessment was proposed. Such a process will require global regulatory authority participation to lead to its acceptance. The identification of unique effects in dogs that are not identified in rodents will need further evaluation and determination of their relevance to humans. The establishment of in vitro and in silico approaches that can provide critical data on relative species sensitivity and human relevance will be an important tool to advance the decision process. Promising novel tools including in vitro comparative metabolism studies, in silico models, and high-throughput assays able to identify metabolites and mechanisms of action leading to development of adverse outcome pathways will need further development. To replace or eliminate the 90-day dog study, a collaborative, multidisciplinary, international effort that transcends organi­zations and regulatory agencies will be needed in order to develop guidance on when the study would not be necessary for human safety and risk assessment.

Thresholds of adversity and their applicability to endocrine disrupting chemicals.

Within the European Union, various legislative acts contain specific provisions on endocrine disruption, requiring the regulation of substances with endocrine disrupting properties via a hazard-based approach. Presumably this is due to an assumed lack of thresholds for the adverse effects of such substances. Conversely, in other jurisdictions, such as USA, Canada, Australia and Japan, endocrine disruptors (EDs) are regulated using a risk-based approach. As a consequence, in recent years there has been increasing controversy on whether thresholds can be inferred for endocrine-mediated effects. There is concern that the endocrine system is too complex to allow estimation of safe levels of exposure to such chemicals. This brief review aims to evaluate the available scientific evidence in this area and offer a sound and robust conclusion supported by this analysis. It is concluded that there is nothing special or unique about endocrine disruption or greater uncertainties in its assessment compared to other non-genotoxic forms of toxicity to justify adopting a non-threshold approach by default. Biology predicts that thresholds of adversity exist and are the rule for all endpoints, including those arising from endocrine disruption. A threshold approach to the risk assessment of endocrine disrupting chemicals is scientifically justified.

An approach to the identification and regulation of endocrine disrupting pesticides.

Recent decades have seen an increasing interest in chemicals that interact with the endocrine system and have the potential to alter the normal function of this system in humans and wildlife. Chemicals that produce adverse effects caused by interaction with endocrine systems are termed Endocrine Disrupters (EDs). This interest has led regulatory authorities around the world (including the European Union) to consider whether potential endocrine disrupters should be identified and assessed for effects on human health and wildlife and what harmonised criteria could be used for such an assessment. This paper reviews the results of a study whereby toxicity data relating to human health effects of 98 pesticides were assessed for endocrine disruption potential using a number of criteria including the Specific Target Organ Toxicity for repeat exposure (STOT-RE) guidance values used in the European Classification, Labelling and Packaging (CLP) Regulation. Of the pesticides assessed, 27% required further information in order to make a more definitive assessment, 14% were considered to be endocrine disrupters, more or less likely to pose a risk, and 59% were considered not to be endocrine disrupters.