A field method for ecotoxicity assessment of rain water wash-off from anti-sapstain treated timber was developed. In the course of this study freshly sawn timber treated with 1.5% Busan 30 L (reference preservative) and a control stack with untreated pine were exposed to weathering. The run-off water was ecotoxicologically tested with organisms from three trophic levels (Vibrio fischeri, Kirchneriella subcapitata, Daphnia magna). Results show, that the highest ecotoxicity can be detected immediately after treatment and within the first 4 weeks of storage - depending on the precipitation: high rainfall during the first month of exposure significantly increases ecotoxicity. Covering the treated stack provides sufficient protection of timber against leaching of chemicals and further on significantly minimises the environmental risk. Results suggest either storage of anti-sapstain treated timber in saw mills underneath a roof or, when stored outside, protection of treated stacks by coverage.

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