In a world that is often characterised by anthropogenic pressures, environmental protection is required and a complex task. Anthropogenic chemicals are part of the stressors that threaten biodiversity and ecosystem functions. For this reason, chemicals undergo a risk assessment procedure before being authorised for the market, with different risk assessment procedures applying to different classes of chemicals.  There are a number of challenges associated with chemical risk assessment, but one of the most significant is that chemicals need to be tested prospectively before they are authorised. This implies that tests need to be performed under (semi-)laboratory conditions, often in very much simplified systems under standardised conditions. Once authorised, however, the released chemicals enter the environment and distribute there, exposing a much larger variety of species than those tested to residues, usually in multi-stress conditions, in a community context, and under sub-optimal conditions. The aim of environmental risk assessment of chemicals is to bridge the gap between simplified (semi-)laboratory testing, and the real-world conditions under which organisms are faced with chemicals.

Mechanistic effects models are emerging, but already crucial methods in environmental risk assessment that allow to understand processes that lead to transport and distribution of chemical in the environment, to the exposure of organisms and uptake, to damage accrual and eventually to apical outcomes at levels of organisms, populations and ecosystems. These effect models are quite valuable in combination with experimental and environmental monitoring data, because they are ideal tools to understand mechanisms of effects, to generalise experimental findings to more realistic environmental conditions, to assess chemical risks under the impact of stressors that cannot be tested in the laboratory, and to evaluate monitoring data in a retrospective way. The seminar talk will shortly introduce the concept of chemical risk assessment, and give an overview of types of mechanistic effect models that are currently applied or are in development for different purposes. Specific examples for modelling chemical effects on terrestrial arthropods, amphibians and honeybees will be given, and additional highlights on currently ongoing work will include the fusion of mechanistic models with machine learning methods for pollinators, algae community modelling and models for uptake and distribution of chemicals in migratory birds.