Mixture Modelling and Effect-Directed Analysis for Identification of Chemicals, Mixtures and Effects of Concern

Abstract

The complex mixtures of organic pollutants detected in environmental matrices means that chemical analysis alone does not provide a full picture of the chemical burden. Instead, bioassays, which detect the effects of all active chemicals in a sample, are proposed as complementary tools for environmental monitoring. This chapter outlines relevant mixture toxicity modelling concepts and demonstrates how the bioanalytical equivalent concentration approach (BEQ) can be used to evaluate the effects of environmental mixtures. Using iceberg modelling, BEQ from bioanalysis and BEQ from chemical analysis can be compared to determine how much of the effect can be explained by detected chemicals, with examples of iceberg modelling in water and sediment discussed. In the case of contamination hotspots, effect-directed analysis can be applied to identify unknown bioactive chemicals using a combination of fractionation, bioanalysis and chemical analysis with structural identification. Finally, effect-based trigger values derived by reading across from existing chemical guideline values were proposed to assess whether the effects of chemical mixtures in water are acceptable or unacceptable. This chapter highlights the importance of using bioassays in parallel to chemical analysis for environmental monitoring to gain a better understanding of the overall chemical burden.