Ecotoxicological behaviour of leachates from superficially treated timber as an approach for a test strategy of environmental risk assessment in wood preservation
H W Wegen, U J Lucks
At present for wood preservatives, which in Germany are subject to the quality mark of the RAL-Gütegemeinschaft Holzschutzmittel, health and safety as well as environmental aspects are evaluated by official authorities, as BgVV (Federal Institute for Consumer Health Protection and Veterinary Medicine) and the UBA (Federal Environmental Agency).
From the environmental point of view to day there are additional requirements concerning the environmental behaviour of RAL-preservatives for timber used in hazard class 3. Information on the ecotoxicity of preservatives and ingredients as well as on the effect of losses from treated timber is requested in general.
There is a lack of generally approved and harmonized test procedures in this field of wood preservation assessment. Therefore, a first test model was developed in accordance with the German federal environmental agency. This test procedure follows existing standards on efficacy of wood preservatives such as EN 84 and ecotoxicological testing of chemicals. Otherwise, it takes into account practical aspects of the application of wood preservatives.
Ecotoxicological studies using fish, daphnids, green algae and luminescent bacteria as bioindicators were conducted with a range of formulations based on modern biocides. The ecotoxicity of leachates from treated timber is compared with the acute ecotoxicity of the formulations themselves. It becomes obvious, that a clear differentiation must be made between the effects of the formulations and the timber treated with them. In all trophic stages tested, it was shown, that enormous safety factors are existing for properly treated timber.
It is possible to use the described test model for an environmental assessment with regard to the European Biocidal Products Directive. If ecotoxicological studies of a wood preservative are in accordance with the designed test model, additional ecotoxicological tests on the product or environmentally relevant components of it can be avoided or justifiably confined to a minimum.