PARENT SESSION

2A - Mixture Toxicity
Hall 6
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Hermens, J.¹, ¹
Co-chair: Toy, R.², Backhaus, T.³, ^{2 3}

(MO6/5) Non-polar and polar narcotics have equal effective membrane concentrations and act concentration-additive in mixtures.

Escher, Beate¹, Eggen, Rik¹, Vye, Erika¹, Schwarzenbach, Rene^{1, 2}, ¹ EAWAG Swiss Federal Institute for Environ. Sci. and Technol., Dübendorf, Switzerland, Switzerland² ETH Swiss Federal Institute of Technology, Zürich, Switzerland, Switzerland

ABSTRACT- Baseline toxicity (narcosis) is experimentally determined with an in-vitro test system composed of membrane vesicles isolated from photosynthetic bacteria. This test system is selective for baseline toxicity and is more sensitive than other mechanistic test systems for baseline toxicity. Since the tests system contains only the target site for baseline toxicants, the biological membrane, effective target site concentrations could be directly determined by combining the in-vitro test with membrane-water partition experiments. No difference was observed between the effective membrane concentrations of non-polar and polar compounds, confirming the earlier hypothesis that differences in lethal body burdens are caused by unequal distribution between target and non-target lipids but not by different mechanisms. Mixture experiments confirmed concentration-additivity for mixtures containing both polar and non-polar compounds and mixtures of industrial chemicals and pharmaceuticals.

Key words: baseline toxicity, narcosis , membrane-water partitioning, mixtures