Strategies that dramatically reduce leaching of water-soluble 
metal-containing biocides from treated biodegradable products. Aqueous, 
preservative compositions of the present invention incorporate one or more water-soluble 
metal species having biocidal activity and one or more agents that increase the leaching resistance of these 
metal species when impregnated into biodegradable products. Using one or more of these agents allows usage rates of the 
biocide impregnants to be dramatically lowered at the time of impregnation of the products. Because less of the metal 
biocide leaches in the presence of these agent(s), less 
biocide has to be added in order to meet desired loading goals. Generally, an agent of the present invention that reduces leaching of metal biocides is 
water soluble, is substantially nonionic in aqueous media, has a molecular weight greater than about 100, and has a 
vapor pressure less than that of water at standard temperature. Preferred agents are those including at least 10 weight percent, more preferably at least 16 weight percent, and even more preferably at least 20 weight percent 
oxygen. Examples of these preferred agents include (poly)ethers and / or nonionic surfactants including one or more oxyalkylene units in the backbone and / or as substituents of the molecule.