Laboratory scale studies of biocide leaching from façade coatings

Organic architectural coatings require the use of biocides to prevent microbial defacement of building façades. The biocides are meant to slowly release to the surface, but they can still potentially enter the environment via runoff during rain events. Accurate source emissions estimates are necessary for risk assessments, and knowledge of the release mechanism can aid both regulators and producers alike. In this study, several biocides and several market and reference coating systems were subjected to regular irrigation and drying cycles with varying temperature conditions. The results were compared to other studies and models from the controlled release literature, demonstrating diffusion controlled release with dependence on the experimental conditions. The role of wetting and drying cycles in accelerating release is highlighted.