ABSTRACT
(Quantitative) structure-activity relationships ([Q]SARs) are used as the first tier in tiered risk assessments and, as such, typically result in the application of the highest uncertainty factors for extrapolation of data, due to the relative remoteness of natural realism in the model. This chapter focuses on ecotoxicological (Q)SARs and introduces ecotoxicological (Q)SARs in general and provides examples of and potential regulatory uses of (Q)SAR models. Baseline toxicity is the reference case for most (Q)SARs because it is assumed to represent the minimal toxicity of any given chemical. The number of known structures of receptor sites is rapidly increasing, opening new possibilities in the area of environmental (Q)SARs. (Q)SARs are developed for chemical classes based on measured test data that have been submitted by industry, or they are developed by other sources for chemicals with similar structures. The exact procedure for using (Q)SARs in the European Union after implementation of the new chemicals policy is unclear.
