Monitoring dioxin-like and estrogenic activity using the ERE- and DRE-CALUX Bioassay: Case-study in the Zenne River crossing the Brussels Region (Belgium)

Introduction
Emerging pollutants (EPs) are a group of chemical substances that have been recently detected in fresh waters, as a result of human activities1. According to the NORMAN website these substances are "pollutants currently not included in routine monitoring programmes (at least at the EU level) but which could pose a significant risk requiring regulation, depending upon their potential (eco)toxicological and health effects and on their levels in the (aquatic) environment".

Among the various substances that can be categorized as EPs, endocrine disrupting chemicals (EDCs) are of special concern because these substances interfere with hormone biosynthesis, metabolism, or their action results in a deviation from normal homeostatic control or reproduction2. The group of molecules identified as EDCs is highly heterogeneous and includes synthetic chemicals used as industrial solvents/lubricants and their by-products, plastic/resin precursors, plasticizers, pesticides, pharmaceutical and personal care products and flame retardants. The peculiarity of EDCs is that these substances are extremely diverse and do not apparently share any structural similarity other than usually being of small molecular mass (