PARENT SESSION

5G - Species sensitivities distribution
Hall 2
1:45 PM - 3:30 PM, Tuesday, 29 April 2003
Chair: Posthuma, L.¹, ¹

(TU2/14) Differential Aquatic Freshwater Invertebrate Risk Assessment for an AChE inhibitor (Carbaryl).

Schaefers, Christoph¹, Hommen, Udo¹, Ebert, Eugen², ¹ Fraunhofer IME, Schmallenberg, Germany² Bayer CropScience, Frankfurt, Germany

ABSTRACT- The risk for different groups of freshwater macroinvertebrates due to use of the insecticide Carbaryl was estimated based on intrinsic toxicity to and ecological requirements of different species. The large data set of available toxicity data in the literature was checked and completed by eight new studies conducted under GLP conditions. The final data set represents almost all taxonomic groups of freshwater macroinvertebrates and considers laboratory single species studies as well as some model ecosystem and field studies. Due to the well-known mode of action (AChE-inhibition), the fast manifestation of effects, and the physico-chemical properties of Carbaryl, the data show a high consistence, independently of the relation to nominal or measured concentrations. Despite the fact that for some studies only poor information was available, all studies contribute to a clear pattern: The water exchange probability at respiratory membranes seems to rule sensitivity. Three groups of sensitivity without overlap could be attributed to (1) inhabitants of fast flowing waters, (2) species living in considerable flow habitats and (3) inhabitants of slowly flowing or lentic waters. An additional group of sensitive organisms is formed by Cladocera as planktonic high performance filterers. For the most sensitive group (inhabitants of fast flowing waters), such as Plecoptera and Heptageniidae, risk is reduced by very short exposure in these type of habitats due to fast dilution and transport. Cladocera as the next sensitive group are characterized by a high potential of recovery due to fast reproduction and resting stages. The third sensitive group of species, living in considerable flow habitats, is represented by Gammaridae and different insect larvae without fast reproduction and resting stages and without restriction to habitats with high stream velocity. Therefore, for this group an acceptable environmental concentration was estimated by a probabilistic approach, using a species sensitivity distribution of NOECs.

Key words: Macroinvertebrates, Carbaryl, Species Sensitivity Distribution, Higher tier study