Smog, air pollution colloquially called the "marine layer' in Los Angeles and the cause of choking midday darkness in Beijing, could be cleaned by special pavement.
The Los Angeles Times last week reported on a paper published in a recent edition of the Journal of Hazardous Materials. Dutch researchers had invented air purifying paving blocks (photocatalytic pavement) that were observed to have cut contaminants caused by vehicular by nearly half during a yearlong pilot study.
Vehicles and industrial emissions are the biggest contributors toward modern smog. The pavement was designed to target nitrogen oxides. It reduced that pollution anywhere from 19%-45% depending on conditions. The pollution becomes "less harmful chemicals," the Times reported.
A "smog eating" street has already debuted in Chicago where a two-mile stretch of road and sidewalk in the city's Pilsen neighborhood has been deployed to reduce air pollution caused by commercial transportation. The façade of a hospital in Mexico utilizes a similar chemical reaction to create a healthier campus for patients.
United Nations research has found that cities contribute up to a staggering 70 percent of greenhouse gasses. Air pollution is estimated to cost the Chinese economy at least US$100 billion annually. Smarter roads could be worth the investment (the concrete industry sure thinks so).
Note that nitrogen oxides are a minor greenhouse gas.