Ecotoxicology - How to assess the impact of toxicants in a multi-factorial environment?

Ecotoxicology assesses the fate of contaminants in the environment and contaminant effects on constituents of the biosphere. With respect to effects assessment, current ecotoxicology uses mainly reductionistic approaches. For concluding from the reductionistic approach to the effects of toxicant exposure in a multifactorial world, ecotoxicology relies on extrapolations: (i) from suborganism and organism effect levels, as determined in laboratory tests, to ecological levels, (ii) from few laboratory test species to the broad range of species and their interactions in the ecosystem and (iii) from the analysis of the effects of single toxicants under standardized laboratory settings to the toxicant response under real world conditions, where biota are exposed to combinations of chemical, biological and physical stressors. The challenge to ecotoxicology is to identify strategies and approaches for reducing uncertainty and ignorance being inherent to such extrapolations. This chapter discusses possibilities to improve ecotoxicological risk assessment by integrating mechanistic and ecological information, and it highlights the urgent need to develop concepts and models for predicting interactions between multiple stressors.