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Reproducibility of binary‐mixture toxicity studies
Author(s) -
Cedergreen Nina,
Kudsk Per,
Mathiassen Solvejg Kopp,
Sørensen Helle,
Streibig Jens Carl
Publication year - 2007
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/06-196r.1
Subject(s) - reproducibility , toxicity , environmental chemistry , environmental science , chemistry , chromatography , organic chemistry
Binary‐mixture studies often are conducted with the aim of elucidating the effect of one specific chemical on the biological action of another. The results can be interpreted in relation to reference models by the use of response‐surface analyses and isobolograms. The amount of data needed for these analyses is, however, extensive, and the experiments therefore rarely are repeated. In the present study, we investigate the reproducibility of isobole shapes of binary‐mixture toxicity experiments in terms of deviation from the reference model of concentration addition (CA), dose‐level dependence, and isobole asymmetry. We use data from four herbicide mixtures tested in three to five independent experiments on the aquatic test plant Lemna minor and the terrestrial plant Tripleurospermum inodorum . The results showed that the variation both within and among experiments was approximately half the size for the aquatic test system compared to the terrestrial system. As a consequence, a consistent deviation from CA could be obtained in three of four herbicide mixtures for L. minor , whereas this was only the case for one or two of the herbicide mixtures tested on T. inodorum . For one mixture on T. inodorum , both CA synergism and antagonism were detected. Dose‐dependent effects could not be repeated consistently, just as the asymmetry found in some isoboles could not. The study emphasizes the importance of repeating mixture toxicity experiments, especially for test systems with large variability, and using caution when drawing biological conclusions from the test results.