Smog-eating chemical

The unit cell of Anatase - one of the mineral forms of TiO2

Richard Meier's church in Tor Tre Teste, Rome, that features the TiO2 coating

The chemical industry (e.g. Italcementi Group, Millennium Chemicals) has come up with a revolutionary coating, of titanium dioxide (TiO2), that can be applied to the surface of buildings or as an ingredient in plastics, fabrics, ceramic tiles and road paving materials. TiO2, particularly in the anatase form, is a photocatalyst under UV light that allows the pollutants in the air to react with the oxygen in the air and coverts it to a form which then falls onto the ground and is washed away by the rain. So, in addition to keeping walls clean, it has the potential to cut breathing problems by cleaning the air around buildings. According to Italcementi, tests in urban settings determined that some pollutants could be reduced by 20 to 70 percent. The reduction of pollutants is greatest within about 8 ft. of a surface that has been treated, the company said. This means that a pedestrian on a street with traffic would inhale fewer pollutants while passing treated buildings. It has already been tested on Meier's church and more trials are under way on a pavement in Southampton Row in central London, and at Sir John Cass’s school in the City.

Sources: The Sunday Times, The New York Times