Toxicity, tolerance and bioremediation of wood treated with copper based preservatives

Copper compounds are one of the most important and frequently used ingredients in commercial preservatives for construction wood. Copper toxicity has been utilised for more than 100 years. Though the mechanisms of toxicity are not completely understood, it is clear that copper must be soluble in order to have a fungicidal effect. Over the past 10 years there has been an increasing occurrence of the copper tolerant wood decay fungi. The occurrence is not completely understood. It seems that the phenomenon of copper tolerance can significantly be linked to copper solubility. Oxalic acid excreted by tolerant strains reacts with copper and insoluble copper oxalate is precipitated. Because of the copper tolerant fungal strains, classical copper based preservatives, like CCA or CCB, are not efficient in some cases. Wood treated in such a way may cause significant economical damage. Therefore, it is of great commercial importance to understand the phenomenon of copper tolerance and develop new, more reliable preservatives. By year 2020, about 19 X 10(6) m(3)/year of copper treated wood world-wide will have been available for recycling, and, as no environmentally sound solution for its deposition or detoxification has been found, the use of copper tolerant strains for remediation of waste copper treated wood seems to be a very promising solution.