KWR at EUROTOX 2025

EUROTOX 2025 brought together a diverse community of scientists and professionals, including experts from RIVM and other leading international organisations. Both formal sessions and informal networking created a dynamic space for cross-sector dialogue, generating fresh insights that will help guide future water-quality research and management. Sanah actively engaged with discussions and gained knowledge about new toxicological methods and their real-world applications. She also presented her poster, “Mixture toxicity assessment: Advancing approaches for drinking water quality”, showcasing KWR’s latest work on evaluating complex chemical mixtures. 

KWR’s participation shows our commitment to bridging science and practice, ensuring that our research advances scientific understanding to deliver tangible benefits for safe and sustainable drinking water. It also strengthens our active ties with toxicology specialists across organisations, including food and public-health authorities, reinforcing our role in the wider public-health network. 

Image 1. Sanah M Shaikh at EUROTOX 2025 – Athens, Greece

Why chemical mixtures matter

People are constantly exposed to diverse low-level chemicals originating from multiple sources, such as environment, consumer products, industrial emissions, and pharmaceuticals. Many of these exposures occur unintentionally, and some cannot reasonably be avoided due to their pervasive presence in environmental media such as drinking water sources. In real life, chemicals rarely occur singly. These often co-occur in varying combinations, concentrations, and over time, making exposure far more complex than what is considered in single-substance assessments. Depending on their concentrations, these substances can interact in the environment or within biological systems, sometimes producing combined effects that differ from those of the individual chemicals, a phenomenon referred to as mixture toxicity. These interactions can be additive, where effects accumulate; synergistic, where effects amplify each other; or antagonistic, where one chemical reduces the effect of another. Understanding these interactions is essential, as they can influence both human health and ecosystem safety in ways that are not captured by evaluating chemicals individually. 

Regulatory challenges in mixture toxicity assessment

In the EU, public concern over chemical exposure is high, yet current regulatory frameworks primarily focus on individual substances. Intentional mixtures, like disinfectants added during water treatment, can be evaluated based on their known toxicity, but unintentional mixtures from agriculture, industry, or urban runoff remain difficult to assess. The sheer number of possible chemical combinations, limited hazard data, and variable human exposure patterns make experimental testing of all mixtures impractical. As a result, the cumulative risks posed by everyday chemical exposures are often underestimated. To address these challenges, the Chemical Water Quality and Health Team of KWR is currently working on a framework aimed at better understanding and evaluating the risks of low-level chemical mixtures in drinking water and its sources. This approach combines chemical analysis with (targeted) bioassays to evaluate complex and variable mixtures, including emerging contaminants such as PFAS. By identifying “relevant mixtures” and incorporating their combined effects into risk assessments, KWR aims to strengthen drinking water safety, support regulatory development, and ensure public health protection in a rapidly evolving chemical landscape.