Evaluation of the isobologram method for the assessment of mixtures of chemicals. Combination effect studies with pesticides in algal biotests.

The aim of this paper is an evaluation of isobolograms, a method proposed for the assessment of combined effects of chemicals. In order to examine potentials and shortcomings of this approach for ecotoxicological purposes, algal biotests with selected pesticidal compounds were performed. Additivity, as defined by the model, is demonstrated for the combination of atrazine and metribuzin for different combination ratios, response levels, and parameters. Subadditivity is shown for amitrole and glufosinate-ammonium. The results and inherent biometrical features are discussed in terms of criteria considered suitable for comparative evaluation of biometrical models for the assessment of mixtures of chemicals.