Prioritization of biocidal active substances based on the assessment of environmental risks in natural waters in Switzerland

Background, Aim and Scope Active substances for use in biocidal products can potentially occur as mi- cropollutants in natural waters. Biocides, which are used in Switzerland for non-agricultural applications, should be evaluated and prioritized with regard to their respective environmental risks. The following questions were emphasized: Which active substances are used for which purposes and in which amounts? Is there discharge to the aquatic environment? What are the environmental behaviours and ecotoxicological effects of these biocides? How can a prioritization be achieved? Which active substances should be suggested for further assessments? Methods Manufacturing firms, sales organisations, users and environmental experts were identified as key stakeholders for the issues of this project. Chemical identities, product compositions, used amounts, product types, ways and places of applications were elucidated. A database was established with information on approximately 1760 products with totally 277 active substances. A prioritization procedure was established, providing a distinction of the active substances. For priority setting, water pollution risks by biocides were evaluated based on potential environmental emissions as well as on environmental behaviour and ecotoxic effects. Results In the European Union 372 active substances were notified for biocidal products, which accounted for use of 7500 tons per year in Switzerland. More than 95 % of the total use bases on 30 active substances, of which seven are rapidly biodegradable. A group of experts determined 22 substances as candidates for an extended assessment. It became evident that many active biocidal substances are highly ecotoxic und could, therefore, cause an augmented environmental risk Discussion It could be shown which active substances are applied in Switzerland in substantial amounts. Although close to 300 active biocidal substances are used, only about 30 substances are employed in relevant amounts of more than 5000 kg per year. For 22 active substances with low biodegradability, a potential environmental risk for natural surface waters can be inferred. These active substances are used at amounts comparable to the pesticides. Recommendations and Perspectives Looking at the - in comparison to the pesticides - very scarce knowledge for biocidal products, it is necessary to have a closer look at usages, environmental behaviour and ecotoxicity of the priority substances. For the practical application of the bio- cides, consulting should be given which is orientated on a best-practice procedure for the particular products. © Springer-Verlag 2009.