Expert opinion on toxicity profiling--report from a NORMAN expert group meeting.

This article describes the outcome and follow-up discussions of an expert group meeting (Amsterdam, October 9, 2009) on the applicability of toxicity profiling for diagnostic environmental risk assessment. A toxicity profile was defined as a toxicological "fingerprint" of a sample, ranging from a pure compound to a complex mixture, obtained by testing the sample or its extract for its activity toward a battery of biological endpoints. The expert group concluded that toxicity profiling is an effective first tier tool for screening the integrated hazard of complex environmental mixtures with known and unknown toxicologically active constituents. In addition, toxicity profiles can be used for prioritization of sampling locations, for identification of hot spots, and--in combination with effect-directed analysis (EDA) or toxicity identification and evaluation (TIE) approaches--for establishing cause-effect relationships by identifying emerging pollutants responsible for the observed toxic potency. Small volume in vitro bioassays are especially applicable for these purposes, as they are relatively cheap and fast with costs comparable to chemical analyses, and the results are toxicologically more relevant and more suitable for realistic risk assessment. For regulatory acceptance in the European Union, toxicity profiling terminology should keep as close as possible to the European Water Framework Directive (WFD) terminology, and validation, standardization, statistical analyses, and other quality aspects of toxicity profiling should be further elaborated.