|
(02-10) Mixture toxicity analysis of complex environmental mixtures. Walter, Helge-Alexander*,1, Grote, Matthias1, Brack, Werner1, Altenburger, Rolf1, Scholze, Martin2, Pavan, Manuela3,4, Grammatica, Paola3, 1 Centre for Environmental Research, Leipzig, Germany2 University of Bremen, Bremen, Germany3 University of Insubria, Varese, Italy4 University of Milano Bicocca, Milan, Italy ABSTRACT- For the assessment and prediction of the toxicity of chemical mixtures, the pharmacological concept of CONCENTRATION ADDITION (CA), implying similar action of the mixture components, and the concept of INDEPENDENT ACTION (IA), assuming the chemicals to act independently and in a dissimilar way, are proposed. So far reference cases could be established demonstrating that these concepts might well be used to predict and assess combination effects of mixtures of chemicals which are characterised in respect to the number of mixture components, their mode of action, their concentration in the mixture and their toxicity as single compounds. However, environmental exposure situations are often characterised by a multitude of heterogenous chemicals with unknown modes of action lacking any classification presupposed by the concepts on mixture toxicity assessment. The majority of chemicals constituting the mixture are likely to occur in concentrations as low as their individual NOEC. Moreover, in environmental samples most of the compounds are rather unknown. Additionally environmental factors like light and pH characterise milieu conditions and may consequently influence the toxicity of environmental chemicals and mixtures thereof. In this study, biological and chemical methods were applied to identify pollutants for mixture experiments with ecotoxicological potency in sediments from a contaminated site. The mixtures investigated consisted of chemicals with were experimentally investigated individually and of unresolved complex environmental mixtures. Based on the toxicity information of the major toxicants expectations of the mixture toxicity were calculated allowing for the influence of abiotic factors like light and were compared with experimental results. The applicability of the concepts of CA and IA to assess and predict the toxicity of mixtures of environmental chemicals will be discussed with respect to the relevance of milieu factors and background mixtures. Key words: unresolved mixtures, milieu conditions, joined action, algae biotest |
