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Joint algal toxicity of p… - University of Gothenburg, Sweden Till startsida
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Joint algal toxicity of phenylurea herbicides is equally predictable by concentration addition and independent action.

Journal article
Authors Thomas Backhaus
Michael Faust
Martin Scholze
Paola Gramatica
Marco Vighi
L Horst Grimme
Published in Environmental toxicology and chemistry / SETAC
Volume 23
Issue 2
Pages 258-64
ISSN 0730-7268
Publication year 2004
Published at Botanical Institute, Plant Physiology
Pages 258-64
Language en
Keywords Algae, Green, drug effects, growth & development, Dose-Response Relationship, Drug, Drug Interactions, Herbicides, toxicity, Models, Chemical, Phenylurea Compounds, toxicity, Toxicity Tests, Water Pollutants, Chemical, toxicity
Subject categories Natural Sciences, Chemical Sciences, Environmental chemistry, Environmental toxicology, Biological Sciences, Biochemistry, Toxicology, Ecology, Freshwater ecology, Marine ecology, Toxicology


Photosynthesis-inhibiting phenylurea derivatives, such as diuron, are widely used as herbicides. Diuron concentrations clearly exceeding the predicted-no-effect concentration have been regularly measured in European freshwater systems. The frequently observed exposure to mixtures of phenylureas additionally increases the hazard to aquatic primary producers. Fluctuating numbers and concentrations of individual toxicants make experimental testing of every potential mixture unfeasible. Thus, predictive approaches to the mixture hazard assessment are needed. For this purpose, two concepts are at hand, both of which make use of known toxicities of the individual components but are based on opposite mechanistic suppositions: Concentration addition is based on the idea of similar mechanisms of action, whereas independent action assumes dissimilarly acting mixture components. On the basis of pharmacological reasoning, it was therefore anticipated that the joint algal toxicity of phenylurea mixtures would be predictable by concentration addition. Indeed, we could demonstrate a high predictive power of concentration addition for these combinations. Surprisingly, however, the opposite concept of independent action proved to be equally valid, because both concepts predicted virtually identical mixture toxicities. This exceptional case has previously been derived from theoretical considerations. Now, the tested phenylurea mixtures serve as an example for the practical relevance of this situation for multicomponent mixtures.

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