A team of students from the University of California, Riverside's Bourns College of Engineering developed an innovative roof tile coating that, when applied to a typical residential roof, can clean the air by breaking down smog-causing nitrogen oxides.

And only costing about an additional $5 to make, this roof coating could break down as much nitrogen oxide pollution as is produced by a car driven for 11,000 miles.

A titanium dioxide mixture is the key to making this invention work. One tile at a time, if these titanium dioxide-coated tiles replaced the roof tiles on one million homes, it would eliminate 21 tons of nitrogen oxides every day.

That's significant considering Southern California emits 500 tons of the harmful pollute daily in the South Coast Air Quality Management District coverage area, which includes all of Orange County and the urban portions of Los Angeles, Riverside and San Bernardino counties.

Nitrogen oxide is produced from the burning of certain fuels at high temperatures, and turns into the cloudy smog we know when they react with volatile organic compounds in the presence of sunlight.

The UC Riverside team - Carlos Espinoza, Louis Lancaster, Chun-Yu "Jimmy" Liang, Kelly McCoy, Jessica Moncayo and Edwin Rodriguez - came up with the roofing design as part of an Environmental Protection Agency student design competition.

After coating two off-the-shelf clay tiles with different amounts of titanium dioxide - a common compound found in everything from paint to food to cosmetics - they found that the coated tiles removed between 88 percent and 97 percent of the nitrogen oxides. And it didn't matter how much of the compound was applied to the tile (despite one having about 12 times as much titanium dioxide coating), it still broke down the harmful pollute.

The findings were detailed in a UC Riverside press release, released June 4.