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(025) Theory and practice of using Species Sensitivity Distributions to predict multi-toxicant ecological effects at contaminated sites. Posthuma, Leo1, Aldenberg, Tom1, Zwart, Dick1, 1 ABSTRACT- Species Sensitivity Distributions (SSDs) are the statistical summary of the phenomenon that species differ in their sensitivity to toxicant exposure. The SSD-distribution functions serve a dual purpose, both in the derivation of Environmental quality Objectives (EQOs) and in Ecological Risk Assessment (ERA). An international group of authors have compiled a book on the use of SSDs in ecotoxicology, overviewing the current status of theory and use. The presentation will present some highlights of the "Evaluation" and "Outlook" chapters of the book, providing the theoretical basis for calculating the net toxic pressure of a mixture of toxicants at a site. Net toxic pressure is quantified as the "multi-substance Potentially Affected Fraction". This ms-PAF is a dimensionless value, quantifying which fraction of species is affected beyond the toxicity endpoint used in SSD-construction. The dimensionless value can be used to rank sites (overall hazard), taxa (which taxa most at risk), and ecotoxicity of compounds in the mixture. The values can be used directly in risk management, or in higher-tier assessments. Currently, for practical application of the SSD-concepts, a computer programme (IQ-tox) is developed, to calculate ms-PAF, and some examples will be shown. The presentation will finally introduce the confirmation of the dimensionless rankings by comparing them to field effects observed at contaminated field sites. Broader confirmation results will be presented in another contribution from our SSD-research line. Key words: Species Sensivitiy Distribution, Potentially Affected Fraction, risk quantification, taxonomic groups |
