title: Read-Across Prediction of the Acute Toxicity of Organic Compounds toward the Water Flea Daphnia magna.
abstract: According to the European REACH Directive, the acute daphnid toxicity needs to be assessed for industrial chemicals with market volumes ≥1 t/a. Employing a data set of 1365 organic compounds with experimental 48-h LC50 data for Daphnia magna, a read-across approach has been developed that makes use of the atom-centered fragment (ACF) method as quantitative measure for structural similarity. Both quantitative log LC50 predictions and a discrimination between narcosis-level and excess toxicity can be obtained, augmented by similarity-triggered information that characterizes a compound as inside or outside the quantitative or qualitative model domain. Reading across proceeds as interpolation of the toxicity enhancement (Te ) over predicted narcosis-level toxicity, taking experimental log Te values from similarity-selected reference compounds as input. The resultant decision tree model yields r(2) =0.85 and rms=0.66 for the subset of 757 compounds (56 %) identified as inside the quantitative model domain, and can handle further 318 compounds (23 %) with the categorical submodel, with 290 compounds (21 %) being outside its domain. The new in silico approach appears useful as ITS (Integrated Testing Strategy) tool for the daphnid toxicity assessment. The discussion includes a comparison of Kow - and LSER-predicted narcosis-level toxicity in the read-across context.
authors.affiliation: UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany tel/fax: +49-341-235-1262/1785.
authors.forename: Ralph
authors.initials: R
authors.lastname: Kühne
authors.affiliation: UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany tel/fax: +49-341-235-1262/1785.
authors.forename: Ralf-Uwe
authors.initials: RU
authors.lastname: Ebert
authors.affiliation: UFZ Department of Effect-directed Analysis, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany.
authors.forename: Peter C
authors.initials: PC
authors.lastname: von der Ohe
authors.affiliation: UFZ Department of Effect-directed Analysis, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany.|Institute for Organic Chemistry, Technical University Bergakademie Freiberg, Leipziger Str. 29, 09596 Freiberg, Germany tel/fax: +49 341 235-1262/1785.
authors.forename: Nadin
authors.initials: N
authors.lastname: Ulrich
authors.affiliation: UFZ Department of Effect-directed Analysis, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Brack
authors.affiliation: UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany tel/fax: +49-341-235-1262/1785. gerrit.schuurmann@ufz.de.|Institute for Organic Chemistry, Technical University Bergakademie Freiberg, Leipziger Str. 29, 09596 Freiberg, Germany tel/fax: +49 341 235-1262/1785. gerrit.schuurmann@ufz.de.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Schüürmann
keywords: Aquatic Toxicity; Atom-centered fragments; Baseline narcosis; Daphnia magna; Read-across; Toxicity enhancement