Umsetzung und Anwendungen
(Englisch)
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Summary and Conclusions
Within the scope of the OECD pesticide risk reduction program a project for the development of pesticide aquatic risk indicators was initiated in 1998. As a result, three indicators (REXTOX, ADSCOR and SYSCOR) were developed to estimate relative risk of agricultural pesticide use to surface water organisms. They were designed as political tools, for national authorities to follow progress of risk reduction measures or plan pesticide management.
The indicators combine pesticide properties, pesticide use data such as applied dose rate, application characteristics such as method of application, and some environmental parameters. In contrast to various existing approaches which calculate hazard indices based on worst case assumptions, the OECD aquatic risk indicators calculate risk indices based on actual use data. In all three indicators relative risk values are estimated by calculating the «exposure:toxicity» ratio. While all indicators include toxicity to the same target organisms (algae, daphnia, and fish), they differ in the approach of exposure estimation. REXTOX uses a mechanistic approach and is the only indicator considering several field site properties. ADSCOR and SYSCOR are scoring indicators, assigning scores to variables assumed to contribute to aquatic risk.
In 2000, the OECD aquatic risk indicator pilot project started as follow up to the indicator development project. Its scope was to allow several countries to test the indicators with their own input data, to assess the indicators' usefulness, validity, and acceptability as policy tools. Apart from Switzerland, Denmark, France, Germany, Japan, Norway, and USA participated in this project.
Input data
Compilation of reliable input data for the indicators turned out to be time consuming. In general properties of active ingredients were derived from handbooks or registration dossiers. For most pesticides physico-chemical data such as log Kow and solubility were readily available. In contrast, for degradation rates in natural water and long term toxicity significant data gaps or data variability of several orders of magnitude were encountered. Swiss use data were only available for the years 1997 and 1998 for the catchment areas of three lakes, namely Greifensee, Baldeggersee, and Murtensee. The limited availability of use data did not allow the calculation of time trends or extrapolation to a national level. In general, the quality of input data, i.e. pesticide use data, physico-chemical data of pesticides, and toxicity data of pesticides has to be improved.
Validation
The Swiss contribution to the indicator validation, included three parts: Sensitivity analysis, exemplary and scenario calculations, and comparison of indicator results with monitoring data. Only two of the three indicators could be thoroughly tested, because the third (SYSCOR) was still under development during the final phase of the project.
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