Population models

Extrapolation of adverse effects on individual organisms to effects on populations is not linear or straightforward. Population models have the potential to make this link by integrating aspects of life history (e.g., reproductive rate), interactions between individuals (e.g., competition and predation) and population-level processes (e.g., density dependence) within a dynamic environment. However, they require a fundamental understanding of ecological principles, quality data for parameterisation and validation with clear and transparent documentation. When all these aspects of model development combine, a powerful tool in the risk assessment of chemicals is produced.

We have developed several population models and used many more in a regulatory context. ECHA/EFSA (2018) guidance on assessing endocrine active substances suggests that population models can be used to extrapolate effects on individuals to those on populations (important as the protection goal is at the population level for non-target organisms). However, no guidance on how to do this is provided, so we have developed a method for using population models in the assessment of endocrine active substances. Specifically, we have made a recommendation on how these models can be parameterised to be consistent with the concept of a hazard assessment as specified in the guidance. This work was presented at SETAC Copenhagen 2022 and as an invited contribution at the Akademie Fresenius ED Conference in Cologne 2022. This work has now been published (Hazlerigg et al. 2023). We have also used this modelling approach in a regulatory context to support active substance renewal. If you are observing adverse effects on individual organisms in the laboratory from an endocrine MoA, then our modelling method for extrapolating to the population level should be your next step.

Individual-based fish population models

Using individual-based fish population models (e.g., stickleback, trout, zebrafish), we have evaluated the population relevance of malformations and other adverse effects from exposure. This uses a risk-based assessment (i.e., dose–response) and applies to the standard assessment of plant protection products. We have an ongoing research project developing population models for bats and mayflies (see EMBARC). In addition to our population modelling work, we have successfully registered products for our clients using body burden modelling in bird and mammal assessments. This incorporated ADME processes as well as ecological traits of focal species to explore the time course of exposure/recovery and determine potential risk. If you would like any further information regarding our effects modelling services, please contact us and we would be happy to talk through your options.

Other expertise

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