Advanced Approaches for Species Surrogacy in Chemical Risk Assessment

Scope of the Meeting

Chemical risk assessment routinely relies on a limited number of sentinel species to inform protection of a much broader range of taxa. These surrogate species enable extrapolation of hazard and risk to related taxa or species of interest in the context of chemical risk assessment. While this practice is well established, it often relies on pragmatic safety factors or overly conservative approaches that lack grounding in mechanistic, exposure and/or ecological information.

Recent advances in toxicokinetics, toxicodynamics, comparative biology, species traits, computational modelling, and data integration provide new opportunities to strengthen the scientific basis for species surrogacy. In parallel, the increasing availability of curated toxicity databases and bioinformatics tools enables more transparent and defensible cross‑species extrapolation. These scientific advances, often referenced as New Approach Methods (NAMs), are ready for review and synthesis to improve the approaches used for species surrogacy in chemical risk assessment and ultimately increase confidence in regulatory decision‑making while minimizing the use of vertebrate animals in testing.

SETAC is convening this meeting as a continuation of its long tradition of bringing together environmental professionals, to advance the state of knowledge on various topics and resolve technical issues to identify solutions for pressing environmental challenges. The meeting is planned in a manner consistent with SETAC’s principles of multidisciplinary, multi-stakeholder engagement and science-based objectivity, is ideal for this topic.

Meeting Format

The meeting will be open to all who want to participate in knowledge exchange and collaborate on advancing the topic. The overall goal of the topical meeting is to engage in knowledge exchange that an expert group (steering committee and select speakers) can distill into publications summarizing the state of the science. Meeting outcomes will be submitted for publication in SETAC journals and disseminated though presentations at SETAC meeting and in SETAC Webinars and Technical Issue Papers.

Sessions

1. Exploring Toxicokinetics Across Species
   
   Chairs: Jon Arnot, Arnot Research and Consulting and Michelle Embry, Health and Environmental Sciences Institute
   
   Toxicokinetics describes rates of absorption, distribution, metabolism, and excretion of a substance. It links external exposure to an internal concentration within an organism (e.g. blood plasma concentration, tissue concentrations, predicted concentrations at the molecular site of activity, etc.).  The similarities and differences in toxicokinetics between species, even closely related species, can be a determining factor for species similarities and differences in their sensitivity to chemicals. This session will icnlude talks about how considerations of toxicokinetics can be used in species extrapolation.
2. Reviewing Toxicodynamics Across Species
   
   Chairs: John Colbourne, University of Birmingham and Jessica Head, McGill University
   
   Toxicodynamics examines how chemicals interact with a biological target or receptor. When extrapolated data across species, It is crucial to determine whether the biological responses observed in one species (such as a surrogate) are retained in others (such as species of concern in risk assessment). The conservation of responses and of a chemical-biomolecular interactions can be assessed using the principles of evolutionary biology and structure-function relationships across species. This session will examine how toxicodynamic considerations can aid in cross-species extrapolation of toxicological outcomes, alongside discussions of toxicokinetics and other biological variations.
3. Considering Species Traits in Species Surrogacy
   
   Chairs: Paul J. Van den Brink, Wageningen University and Mark Johnson, US Army Public Health Center (Retired)
   
   The term trait refers to specific attributes of organisms that are both inherent and characteristic to those organisms such as life history, morphology, physiology, and ecology. It is well established that the traits of organisms dictate their fitness and therefore potential sensitivity to chemical stressors. This sesssion will describe the state-of-the-science in collecting knowledge of functional traits across species, focusing on current and developing approaches, as well as how they can be applied to understand impacts to fitness of individuals and populations across species/taxa.
4. Leveraging Existing Data in Species Surrogacy
   
   Chairs: Luigi Margiotta-Casaluci, College London and Rebecca Dalton, Environment and Climate Change Canada
   
   Existing toxicity data should be leveraged whenever possible to improve predictions of toxicity to untested (target) species. Various tools exist that predict toxicity to an untested species using the known toxicity of the chemical to a surrogate species including interspecies correlation models, quantitative structure activity relationships (QSARs) and species sensitivity distributions (SSDs). This session will aim to review and summarize the latest techniques in this area to set the stage for a identifying a multifaceted, harmonized approach for assembling and integrating lines of evidence for improving cross-species extrapolations to improve risk assessment.