“When the American architect Richard Meier was asked to design a church in Rome to commemorate the 2,000th anniversary of Christianity, he offered an imposing white concrete structure dominated by three soaring ‘sails.’ The project’s main technical sponsor got to work on a coating that would enhance Mr. Meier’s trademark white sculptural forms. It came up with a material that essentially cleans itself, minimizing the need for maintenance. What the sponsor, the Italcementi Group, did not know was that the new material — which contains titanium dioxide, a white pigment — has another peculiarity. It ‘eats’ surrounding smog.”