While Italcemente’s smog-eating cement has been used in Europe for several years, it was released in the United States only in 2007 under the name TX Active. It contains titanium dioxide, which, in the presence of sunlight, acts as a photocatalyer, hastening the decomposition of such pollutants as nitrogen oxides, sulfur oxides, and ozone. TX Active also keeps a building shiny white – a quality admired by architects – by preventing the buildup of pollutants on the surface.

Research suggests that if 15 percent of the surface area of Milan, Italy, were covered in TX Active, air pollutants there could be reduced by 50 percent.

When weighing the environmental effects of concrete, some other benefits need to be included, says Rick Bohan of the Portland Cement Association (PCA), a nonprofit trade group based in Skokie, Ill. For example, the insulation provided by concrete walls combats greenhouse-gas emissions by reducing the energy needed for heating and cooling a building by up to 40 percent compared with wood- and steel-frame structures, according to PCA research.