Advancing environmental risk assessment: investigating the relevance of non-conventional endpoints for effect prediction

Rasmussen, A.S.B. (2026)

Doctoral Thesis

Our modern society thrives on chemicals, and demand is only growing with novel chemicals being introduced onto the market.  However, with increasing demand, so come potentially increasing ecological consequences of these man-made chemicals. Evidence is staggering, showing that chemicals present in our environments at low concentrations over extended timescales can contribute to wildlife population declines and, in many cases, these effects are not predicted by our current widely used standardized methods to assess environmental risk.
A disconnect between measured standardized endpoints such as mortality, growth and reproduction and the way chemicals exert their sublethal effects is likely contributing to a failure in identified adverse effects. Hence, we urgently need to rethink how we assess environmental risk. Therefore, to improve chemical effect assessment, this thesis aims at investigating the relevance of non-conventional endpoints in predicting potential effects of chemical-induced stress.
Through a series of experiments and a meta study focusing on literature on multigenerational studies, this thesis draws the conclusion that while standardization ensures streamlined regulatory processes, it comes with the loss of complexity necessary for specific and novel chemicals. However, added complexity through non-standardized non-conventional endpoints does not always equal to enhanced prediction sensitivity, and ideally endpoint selection in risk assessment, should be on a case-by-case basis. Effect assessment based on a tailored approach considering environmental relevance; allowing the incorporation of non-conventional endpoints and flexible testing requirements can enhance environmental protection urgently needed for effective risk assessment.

• Ecotoxicity
• Non-conventional endpoints
• Neurotoxins
• Biomechanical endpoints
• Behaviour
• Multi-stress
• Benthic species
• Chronic
• Insect
• Long-term exposure

• All authors: Rasmussen, A.S.B.
• Supervisor: Vijver, M.G.; Bosker, T.
• Co-supervisor: Barmentlo, S.H.
• Committee: Peijnenburg, W.; Trimbos, K.; Gsell, A.; Selck, H.; Brink, N. van den
• Qualification: Doctor (dr.)
• Awarding Institution: Institute of Environmental Sciences (CML), Faculty of Science, Leiden University
• Date: 2026-05-07
• Sponsorship: The work presented in this thesis has been conducted with funding received from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska- Curie Actions (MSCA-ITN) no 956009 entitled “Chronic exposure scenarios driving environmental risks of Chemicals (CHRONIC)”.