Combining cell-based bioassays, chemical analysis and mixture modeling for water quality monitoring in the EU project SOLUTIONS

PRESENTER:

Professor Beate Escher

UFZ – Helmholtz Centre for Environmental Research, Germany

Eberhard Karls University Tübingen, Environmental Toxicology, Center for Applied Geosciences, Germany

ABSTRACT:

In vitro bioassays including cell-based bioassays and low-complexity whole-organism assays have been applied for decades in water quality monitoring and more recently high throughput screening tools have become available and with them large datasets of effect data for single chemicals. We can make use of single chemical effect data for linking analytical concentration to predicted effects of the detected chemicals by using the concept of bioanalytical equivalent concentration (BEQ) that is based on the mixture model of concentration addition, which is applicable for many reporter gene assays. The BEQ_chem from chemical analysis can be compared to the BEQ_bio directly quantified in water samples. The gap between BEQ_bio and BEQ_chem (i.e. BEQ_unknown) constitutes the effects elicited by unknown chemicals. As several field studies from the EU project SOLUTIONS demonstrated, for hormone receptors and other highly specific effects, known chemicals typically explain the majority of the observed effects but the analysis of adaptive stress responses, activation of metabolic enzymes and apical effects quantified large fractions of effects caused by unidentified chemicals. Hence bioassays can yield information on chemicals that are not identified or not routinely quantified to obtain an overall estimate of the chemical risk in a water samples. However, there is no common agreement what level of response is acceptable. As of now, bioassay results were only benchmarked against each other but not against an absolute measure of chemical water quality. The EU environmental quality standards (EQS) differentiate between poor and acceptable surface water concentrations for individual chemicals of concern but cannot capture the thousands of chemicals in water and their biological action as mixtures. In the EU project SOLUTIONS, we developed a method for the definition of effect-based trigger methods (EBT) that reads across from existing EQS and makes additional mixture considerations to assure that the derived EBT are protective for complex mixtures as they occur in surface water.