The technique involves applying titanium dioxide, a mineral, as a spray coating to the surface of buildings or as an ingredient in plastics, fabrics and ceramic tiles. Used in this way it acts as a catalyst to break down the pollutants from vehicle exhausts.
The material could be applied to the outside of existing buildings or be incorporated in new ones. In addition to keeping walls clean, it has the potential to cut breathing problems by cleaning the air around buildings.
Trials are under way on a pavement in Southampton Row in central London, and at Sir John Cass’s school in the City.
The technique has been developed by Millennium Chemicals, based near Grimsby, Lincolnshire, and research into its use is now being supported by the European Union. Titanium dioxide has been used for decades as a whitener in products such as toothpaste, but its ability to soak up pollution has been recognised only recently.
Roy Colvile, senior lecturer in air quality management at Imperial College London, who has been acting as an air quality consultant on the London project, said: “I was sceptical at first but . . . there is good reason to believe this could have a measurable effect.
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“The titanium dioxide 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.”