Challenges in retrospective toxicological monitoring: Current issues and a potential way forward

Water quality management in the European Union is governed by the Water Framework Directive (WFD), which has a synergistic overlap with the Marine Strategy Framework Directive (MSFD) and the Drinking Water Directive (DWD). The WFD mandates achieving a “good chemical and ecological status” for surface, groundwater, and coastal waters, primarily through retrospective in situ biomonitoring and targeted chemical analysis of 45 priority pollutants. However, this approach has faced criticism in environmental toxicology. Targeted chemical analysis is inherently limited to preselected substances, overlooking a myriad of other micropollutants present in the environment – often referred to as the “iceberg scenario”. Additionally, while in situ biomonitoring assesses aggregate adverse effects on biota, analysis is only conducted a posteriori, detecting issues only after harmful impacts have occurred – potentially too late to mitigate damage to higher trophic levels of biological hierarchy. Instead, bioassays (in vitro bioanalytical tools) have been proposed as a crucial supplement to current practices. They can be applied as stand-alone methods for assessing toxic effects, such as monitoring influent and effluent waters at wastewater treatment plants in a high-throughput manner. Alternatively, bioassays can complement chemical analysis and in situ monitoring in what is known as the TRIAD approach, offering a more comprehensive assessment. This strategy not only enhances environmental safety evaluations but also facilitates the detection of emerging pollutants that might evade prospective regulatory testing. In this contribution, we will discuss the current challenges of retrospective toxicological monitoring and explore how novel in vitro test methods can address these issues. Additionally, we will highlight ongoing research at Linnaeus University that contributes to these advancements.