QUANTITATIVE STRUCTURE-ACTIVITY-RELATIONSHIPS AND ECOLOGICAL RISK ASSESSMENT - AN OVERVIEW OF PREDICTIVE AQUATIC TOXICOLOGY RESEARCH

In the field of aquatic toxicology, quantitative structure-activity re lationships (QSARs) have developed as scientifically credible toot for predicting the toxicity of chemicals when little or no empirical data are available. A fundamental understanding of toxicological principle s has been considered an important component to the acceptance and app lication of QSAR approaches as biologically relevant in ecological ris k assessments. As a consequence, there has been an evolution of QSAR d evelopment and application from that of a chemical-class perspective t o one that is more consistent with assumptions regarding modes of toxi c action. In this review, techniques to assess modes of toxic action f rom chemical structure are discussed, with consideration that toxicody namic knowledge bases must be clearly defined with regard to exposure regimes, biological models/endpoints and compounds that adequately spa n the diversity of chemicals anticipated for future applications. With such knowledge bases, classification systems, including rule-based ex pert systems, have been established for use in predictive aquatic toxi cology applications. The establishment of QSAR techniques that are bas ed on an understanding of toxic mechanisms is needed to provide a link to physiologically based toxicokinetic and toxicodynamic models, whic h can provide the means to extrapolate adverse effects across species and exposure regimes.