Linking of chemical and effect-based monitoring to support comprehensive assessment of pollution in wastewater and surface water
Authors:   , Finckh Saskia 
Published: February 2025

Since the beginning of industrialisation, the global production of chemicals has increased many times over. According to a comprehensive analysis of national and regional chemical inventories by Wang et al. in 2022, over 350 000 chemicals and mixtures of chemicals have been registered for production and use worldwide. While chemicals offer numerous benefits to society, they can also have serious adverse effects on both humans and the environment. In light of this, various monitoring and regulatory measures have been implemented. However, at current rates of progress, it would take more than 100 000 years to assess all existing synthetic chemicals for their safety to humans and the environment, and an additional 2 000 years to assess new products each year. In consequence of the ever-increasing number of new chemicals and the insufficient monitoring and assessment capacity, it has been claimed that the planetary boundary for chemical pollution is being exceeded. Crossing a planetary boundary is expected to have harmful or even catastrophic consequences for humans and the ecosystem as a whole. Thus, the aim of this work is to gain a better understanding of the occurrence and fate of chemicals in the environment and their ecotoxicological effects. In this context, water resources play a crucial role in the receiving and relocation of chemicals into the environment. Therefore, the thesis focuses on complex chemical mixtures in wastewater and surface water on the European scale, with the objective of contributing to enhance the monitoring and assessment of potential harmful chemicals to support the EU’s vision of a toxic-free environment.
Part I provides a general introduction to the topic (chapter 1) and the definition of the research focus (chapter 2), outlining the objectives and strategies of the three studies. Part II includes the three publications of the studies carried out (chapters 3-5). Part III contains a final synthesis consisting of a summary discussion (chapter 6), an overview of the conclusions of this dissertation (chapter 7) and a final outlook (chapter 8).
The first publication deals with the monitoring and assessment of chemicals in treated wastewater. The main objectives were (i) to gain more knowledge about chemicals in treated wastewater and (ii) to identify and prioritise those substances that pose an increased risk to the environment. A total of 56 treated effluent samples from wastewater treatment plants in 15 European countries were analysed using advanced analytical techniques based on liquid chromatography coupled with high resolution mass spectrometry (LC-HRMS). Of the 499 substances analysed, 366 were detected in at least one of the samples. Concentrations ranged mostly between 1 ng/L and 100 µg/L. A comprehensive assessment using three different risk metrics (TU, HU and RQ) showed that the majority of effluent samples exceeded risk thresholds, with 32 chemicals identified as consensus mixture risk contributors of high concern. Much lower risks were consistently estimated for samples that had undergone advanced treatment with ozonation or activated carbon.
The second publication deals with the endocrine effects of treated wastewater. The main objectives were (i) to compare three different receptor-based estrogenity tests and (ii) to investigate a combined approach of chemical analysis and effect testing for four endpoints: Estrogenity (ERα), Glucocorticogenic activity (GR), Androgenity (AR) and Progestagenic activity (PR). The same treated wastewater samples from the first study were re-analysed by LC-HRMS and LC-MS/MS, adding a further 78 potential endocrine disruptors to the list of measured substances. A total of 56 steroids and phenols were detected in concentrations ranging from 25 pg/L (estriol, E3) to 2.4 µg/L (cortisone). The comparison of three different receptor-based estrogenicity tests (ERα-GeneBLAzer, p-YES, ERα-CALUX) revealed that the results of the ERα-GeneBLAzer and the p-YES test showed the highest agreement. For the majority of the samples analysed in the ERα-, GR-, AR- and PR-GeneBLAzer assay, a ratio of measured mixture-based effects (BEQbio) to calculated component-based effects (BEQchem) between 1 and 10 could be determined, demonstrating the high potential of linking chemical and effect-based monitoring.
The third publication deals with the monitoring and assessment of chemicals in surface waters. The main objectives were (i) to characterise the chemical load of European rivers, here referred to as the ‘chemical footprint’, and (ii) to derive site- and substance-specific information for management prioritisation purposes. A total of 445 European surface water samples from 22 different river basins were analysed using liquid chromatography coupled with high resolution mass spectrometry (LC-HRMS). Of the 610 substances analysed, 445 were detected in at least one of the samples at concentrations up to 74 µg/L. The main finding was that three quarters (74%) of the sites studied exceeded established thresholds for chemical footprints in freshwater, leading to expected acute or chronic effects on aquatic organisms. The largest chemical footprints were found for invertebrates, followed by algae and fish. Cumulative risks are not based on individual substances, but on a large number of substances, as the example of invertebrates shows, where 70 chemicals have contributed to exceeding the chronic risk thresholds. Therefore, focusing on restrictions of single substances would not reflect the complexity of the problem.
In conclusion, this dissertation demonstrates the many advantages of chemical and effect-based monitoring, or the combined use of chemical and effect data, in assessing water quality. Finally, the results of this thesis demonstrate the need for a general reduction in chemical emissions to the water cycle. This can be achieved through both advanced wastewater treatment and measures to reduce emissions at the source in accordance with the ‘polluter-pays-principle’.