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2P Modelling ecotoxic effects (MOP/148) Toxicity of PACs: a comparison between aquatic and terrestrial organisms. Bleeker, Eric1, 2, Droge, Steven1, Wiegman, Saskia2, van Gestel, Cornelis1, Kraak, Michiel2, 1 Vrije Universiteit Amsterdam, Amsterdam, The Netherlands2 Universiteit van Amsterdam, Amsterdam, The Netherlands ABSTRACT- Polycyclic aromatic compounds (PACs) form a highly diverse group of structures containing two or more fused rings, either benzene or cyclopentadiene rings or both. Apart from on-ring substitutions the diversity within this group is enhanced by a variety of atoms that can be incorporated in the aromatic rings, as for example sulphur and nitrogen atoms. Yet, risk assessment for PACs is solely based on (a small number of) homocyclic compounds (PAHs). Furthermore, for most PAHs quality criteria for soils and sediments are derived from aquatic toxicity data or tests with water column inhabiting species in pore water extracted from soil or sediments. To evaluate the consequences of these inevitable extrapolations in risk assessment the toxicity of four polycyclic aromatic compounds was tested for both an aquatic sediment inhabiting species (the midge Chironomus riparius), and two terrestrial species (the springtail Folsomia candida and the enchytraeid worm Enchytraeus crypticus). The chosen compounds are two sets of isomers: the homocyclic anthracene and phenanthrene, and the heterocyclic azaarenes acridine and phenanthridine. All animals were exposed for 28 days via sediment or soil. For the midge survival and day of emergence were scored and for the terrestrial species survival and reproduction were used as parameters. Considerable differences were observed between test species and compounds. Even between isomers toxicity for one species could differ several orders of magnitude. Physico-chemical properties of the test compounds were used to find explanations for the differences observed. Substantial differences between species for one compound were related to differences between the test species. Implications for risk assessment are implemented and will be discussed. Key words: risk assessment, PAH, chronic toxicity, species specifity |
