Generic and comparative ecological risk assessment of pesticides for the terrestrial compartment

Ecological Risk Assessment is considered nowadays the best available tool t o predict the potential danger of human activities on the structure and fun ction of the ecosystems. The assessment can be either generic or very site- specific. In the European Union, under Directive 91/414/EEC the registratio n of a pesticide requires a Generic Risk Assessment to demonstrate that und er Good Agricultural Practices the pesticide can be used without unacceptab le risks for non-target organisms. This generic approach tries to identify those molecules which can be used safely even assuming worst-case scenarios . The opposite approach is to conduct Comparative Risk Assessments, in whic h several alternatives (different pesticides or pesticide combinations) are compared as alternatives to control specific pests in a particular area Th e potential risk of each alternative can be evaluated and used in the cost/ benefit analysis by decision makers. Both approaches can be developed under a common scientific basis, but using different procedures. The risk is qua ntified by a combination of relevant exposure scenarios with the use of det erministic and probabilistic approaches for setting ecotoxicological thresh olds The assessment of the terrestrial environment is a real challenge, due to the combination of several exposure routes and the high epistemological uncertainty of terrestrial ecotoxicology. The state of the art and several proposal are described in this paper.