Different transparent, hydrophobic wood coatings with conventional organic formulations as biocides and nanosilver were exposed to natural and artificial weathering. Run-off water was collected and analyzed, to assess toxicological effects on the aquatic environment. Furthermore, the coatings were evaluated for overall performance and for their protective effect against different microorganisms.

The coating with conventional biocides released the biocides slowly over the exposure time, depending on the weather conditions, especially the intensity of rainfall, but showed a good overall performance free from mould, blue stain and algae.

The products with nanosilver released a small amount of silver, correlating with the overall erosion of the coating. The small quantity and the fact that silver in the run-off water was not ionic and not particulate lead to the assumption, that the risk of these emissions for the aquatic environment is low. On the other hand the protective effect against mould, blue stain and algae seems to be insufficient.