title: Water quality objectives for mixtures of toxic chemicals: problems and perspectives.
abstract: The need to develop water quality objectives not only for single substances but also for mixtures of chemicals seems evident. For that purpose, the conceptual basis could be the use of the two existing biometric models: concentration addition (CA) and independent action (IA), which is also called response addition. Both may allow calculation of the toxicity of mixtures of chemicals with similar modes of action (CA) or dissimilar modes of action (IA), respectively. The joint research project Prediction and Assessment of the Aquatic Toxicity of Mixtures of Chemicals (PREDICT) within the framework of the IVth Environment and Climate Programme of the European Commission, provided the opportunity to address (a) chemometric and QSAR criteria to classify substances as supposedly similarly or dissimilarly acting; (b) the predictive values of both models for the toxicity of mixtures at low, statistically nonsignificant effect concentrations of the individual components; and (c) the predictability of mixture toxicity at higher levels of biological complexity. In this article, the general outline, methodological approach, and some preliminary findings of PREDICT are presented. A procedure for classifying chemicals in relation to their structural and toxicological similarities has been developed. The predictive capabilities of CA and IA models have been demonstrated for single species and, to some extent, for multispecies testing. The role of very low effect concentrations in multiple mixtures has been evaluated. Problems and perspectives concerning the development of water quality objectives for mixtures are discussed.
authors.affiliation: Department of Environmental and Landscape Sciences, University of Milano-Bicocca, Ecotoxicology Research Group Piazza della Scienza 1, I-20126 Milan, Italy. marco.vighi@unimib.it
authors.forename: M
authors.initials: M
authors.lastname: Vighi
authors.forename: R
authors.initials: R
authors.lastname: Altenburger
authors.forename: A
authors.initials: A
authors.lastname: Arrhenius
authors.forename: T
authors.initials: T
authors.lastname: Backhaus
authors.forename: W
authors.initials: W
authors.lastname: Bödeker
authors.forename: H
authors.initials: H
authors.lastname: Blanck
authors.forename: F
authors.initials: F
authors.lastname: Consolaro
authors.forename: M
authors.initials: M
authors.lastname: Faust
authors.forename: A
authors.initials: A
authors.lastname: Finizio
authors.forename: K
authors.initials: K
authors.lastname: Froehner
authors.forename: P
authors.initials: P
authors.lastname: Gramatica
authors.forename: L H
authors.initials: LH
authors.lastname: Grimme
authors.forename: F
authors.initials: F
authors.lastname: Grönvall
authors.forename: V
authors.initials: V
authors.lastname: Hamer
authors.forename: M
authors.initials: M
authors.lastname: Scholze
authors.forename: H
authors.initials: H
authors.lastname: Walter
mesh_terms: D000818:Animals; D004347:Drug Interactions; D005544:Forecasting; D006801:Humans; D008962:Models, Theoretical; D011786:Quality Control; D018570:Risk Assessment; D013329:Structure-Activity Relationship; D018675:Toxicity Tests; D014873:Water Pollutants / Q000592:standards*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D014873:Water Pollutants