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Titel (primär) A general best-fit method for concentration-response curves and the estimation of low-effect concentrations
Autor Scholze, M.; Boedeker, W.; Faust, M.; Backhaus, T.; Altenburger, R.; Grimme, L.H.
Journal / Serie Environmental Toxicology and Chemistry
Erscheinungsjahr 2001
Department BIOTOX; COE
Band/Volume 20
Heft 2
Seite von 448
Seite bis 457
Sprache englisch
Keywords Low-effect concentration; Generalized least squares; Nonlinear regression; No-observed-effect concentration; Bootstrap
Abstract Risk assessments of toxic chemicals currently rely heavily on the use of no-observed-effect concentrations (NOECs). Due to several crucial flaws in this concept, however, discussion of replacing NOECs with statistically estimated low-effect concentrations continues. This paper describes a general best-fit method for the estimation of effects and effect concentrations by the use of a pool of 10 different sigmoidal regression functions for continuous toxicity data. Due to heterogeneous variabilities in replicated data (i.e., heteroscedasticity), the concept of generalized least squares is used for the estimation of the model parameters, whereas a nonparametric variance model based on smoothing spline functions is used to describe the heteroscedasticity. To protect the estimates against outliers, the generalized least-squares method is improved by winsorization. On the basis of statistical selection criteria, the best-fit model is chosen individually for each set of data. Furthermore, the bootstrap methodology is applied for constructing confidence intervals for the estimated effect concentrations. The best-fit method for the estimation of low-effect concentrations is validated by a simulation study, and its applicability is demonstrated with toxicity data for 64 chemicals tested in an algal and a bacterial bioassay. In comparison with common methods of concentration-response analysis, a clear improvement is achieved.
dauerhafte UFZ-Verlinkung
Scholze, M., Boedeker, W., Faust, M., Backhaus, T., Altenburger, R., Grimme, L.H. (2001):
A general best-fit method for concentration-response curves and the estimation of low-effect concentrations
Environ. Toxicol. Chem. 20 (2), 448 - 457