AhR- and ER-CALUX Bioassays for Environmental Monitoring of Polycyclic Aromatic Compounds and Xenoestrogens

Since the early 2000s, emerging environmental contaminants have gained increasing scientific and regulatory attention. These substances can persist in the environment, accumulate in organisms, and may harm ecosystems as well as human health. Despite this, they are insufficiently studied, monitored, and regulated. This thesis focuses on two important groups of such contaminants: polycyclic aromatic compounds (PACs) and xenoestrogens (XEs). PACs are pollutants that are often released during incomplete combustion, while XEs are synthetic or naturally occurring chemicals that can interfere with hormonal systems. Due to their persistence, both groups of compounds are now widely detected in the environment.The challenge in environmental science is not only detecting these substances at trace levels, but also understanding their biological impact, especially when they appear in complex mixtures. Analytical chemical methods can identify known individual compounds, but this often only reveals the tip of the iceberg. The vast majority of unknown or interactive mixture effects are hidden beneath the surface.To address this, my thesis applies cell-based bioassays to assess how living cells respond to chemical mixtures. A key bioassay is the Chemically Activated LUciferase gene eXpression (CALUX). It uses genetically modified cells with a luciferase gene that produces light when activated by certain chemicals.First, an operating protocol was established for CALUX, enhancing its sensitivity, reliability, and accuracy for testing PACs. In addition, a relative potency library for selected PACs was built to support further mixture effect studies. Subsequent efforts focused on validating extraction protocols compatible with CALUX bioassays for analyzing bioactive PACs in both aqueous and soil matrices. Liquid chromatography coupled with fluorescence detector was also employed to evaluate extraction efficiency and calculate the chemical equivalents, allowing comparison of the results with those obtained from the CALUX bioassay.These validated methods were subsequently applied in two case studies. In the case of treated wastewater reuse in agriculture, CALUX was used to monitor bioactive PACs and XEs in wastewater, groundwater, and soil. Environmental risks concerning these substances were evaluated by comparing the results to background values before wastewater irrigation, and by establishing preliminary thresholds for reuse. In the case of plastic pollution in Brussels, CALUX was used to assess the transport of PACs on microplastics in the Zenne River. This research first used seston as a proxy of microplastics to rapidly screen the amount of bioactive PACs associated with microplastics in the urban river.