Cheap roof tile coating can clear heavy smog

What if you can clean the air inside your home with roof tiles? This may soon be a reality with a roof tile coating that when applied to an average-sized residential roof breaks down the same amount of smog-causing nitrogen oxides per year as a car driven 17,600 km.

Researchers at University of California (UC) - Riverside have estimated that 21 tonnes of nitrogen oxide would be eliminated daily if tiles on one million roofs were coated with their titanium dioxide mixture.

They also calculated it would cost only about $5 (Rs.300) for enough titanium dioxide to coat an average-sized residential roof.

Nitrogen oxides are formed when certain fuels are burned at high temperatures.

Nitrogen oxides then react with volatile organic compounds in the presence of sunlight to create smog.

"Currently, there are other roofing tiles on the market that help reduce pollution from nitrogen oxides. However, there is little data about claims that they reduce smog," said student Carlos Espinoza from University of California - Riverside's Bourns College of Engineering.

In their experiment, the team of students coated two identical off-the-shelf clay tiles with different amounts of titanium dioxide, a common compound found in everything from paint to food to cosmetics.

The tiles were then placed inside a miniature atmospheric chamber that the students built out of wood, teflon and PVC piping.

The research by the UC - Riverside team received an honourable mention award for phase two of the US Environmental Protection Agency's student design competition last month.