Ecotoxicity of furfurylated wood – Effect of leachate on aquatic bacteria
A Pilgård, M Westin
Environmental concern regarding the use of toxic preservatives such as CCA (chromated copper arsenate) has been put forward. In the EU, USA and Japan, CCA is now phased out for residential use and for use in water contact. Several ecotoxicological studies of wood treated with conventional preservatives were carried out in the late 1990s. In these studies it was concluded that the main impact is to water and thereby to aquatic organisms. Today, alternatives to conventional preservation, marketed as “environmentally friendly” or “non-toxic” are emerging on the market. Examples of such alternatives are modified wood, e.g. thermally modified, furfurylated and acetylated wood. So far, not enough ecotoxicological studies have been done on these new methods. In the presented study the Microtox assay with the marine bacterium Vibrio fischeri are used as a screening method. Vibrio fischeri were exposed to water leachates from furfurylated wood using two different leaching procedures. The results from the OECD 2 standard test show that Kebony 2 (one of the commercially used furfurylation processes) treated Scots pine have a lower toxicity than all the other samples at all points and that it is the lowest at every point for Radiata pine as well. The explanation might be that there is an immobilization of slightly toxic wood extractives by incorporation in the furan polymer. The lower toxicity for Kebony 2 than for Kebony 1 might be a result of the intermediate vacuum drying step for Kebony 2 that leads to a more efficient curing/polymerisation and less hydrophobic oligomers of a type that may be slightly toxic.