Risk mapping of pesticides: the Dutch atlas of pesticide concentrations in surface waters: www.pesticidesatlas.nl.

Many pesticides are being measured in surface water. To promote the use of monitoring data in the process of risk mapping, post-registration, and improvement of water quality, a free available Internet tool has been developed to present all measurements of pesticides in surface water on the level of individual active ingredients in a spatial framework: the Dutch pesticides atlas (www.pesticidesatlas.nl). With this communication tool one can easily get maps concerning where a pesticide is being measured, observed and possibly constitutes a problem over the years. Pesticide concentrations are being compared with environmental standards and maps can been made of each pesticide at a national level. The pesticide maps have been linked with GIS land use data. At present statistical correlations can be made between crop areas and pesticides concentrations in the water. Moreover, predictions can be made where a pesticide might be exceeding environmental standards. Policy makers, chemical industry (product stewardship), NGO's and farmers can use the maps as a tool for communication and improving environmental quality. The atlas is also being used to evaluate the effectiveness of pesticide policy over the years. In this contribution the methodological background of the pesticides atlas is presented.