In urban metropolitan areas in particular, air quality is harmed by fine dust particles, industrial and traffic nitric oxide (NOx) exhaust, and volatile organic compounds (VOC). Nitric oxide pollution can be reduced at its immediate point of origin through the use of photo-catalytically active surfaces. This involves the mixture of titanium dioxide (TiO2), which acts as a catalyzer, with the building material. Through the interaction of UV rays on the surfaces, the nitric oxide is converted into water-soluble nitrate. The nitrate precipitates as salt and, when dissolved in surface water, is washed away.
