Synthetic TiO2 nanoparticle emission from exterior facades into the aquatic environment

Abstract We present direct evidence of the release of synthetic nanoparticles from urban applications into the aquatic environment. We investigated TiO 2 particles as these particles are used in large quantities in exterior paints as whitening pigments and are to some extent also present in the nano-size range. TiO 2 particles were traced from exterior facade paints to the discharge into surface waters. We used a centrifugation based sample preparation which recovers TiO 2 particles between roughly 20 and 300 nm. Analytical electron microscopy revealed that TiO 2 particles are detached from new and aged facade paints by natural weather conditions and are then transported by facade runoff and are discharged into natural, receiving waters. Microscopic investigations are confirmed by bulk chemical analysis. By combining results from microscopic investigations with bulk chemical analysis we calculated the number densities of synthetic TiO 2 particles in the runoff.