"I write in praise of air. I was six or five/when a conjurer opened my knotted fist/and I held in my palm the whole of the sky./I've carried it with me ever since."
So begins a poem by the British poet Simon Armitage. Called "In Praise of Air," the ode is now splayed across a 65-foot billboard at the University of Sheffield in the north of England. But the words aren't the only special thing. The poster actually cleans the air as well as extolling it.
The material used for the poster, which drapes off the side of a building, is coated with particles of titanium dioxide, a well-known smog-eating material. The university says it can absorb the equivalent pollution of 20 cars every day.
"If every banner, flag or advertising poster in the country did this, we’d have much better air quality," says Tony Ryan, pro-vice-chancellor for science, in a press release. "The countless thousands of [billboards] that are selling us cars beside our roads could be cleaning up emissions at the same time."
Titanium dioxide reacts with sunlight to break down pollutant gases that can cause lung and other problems. And it's also self-cleaning. It takes in a thin layer of rainwater, which washes away grime and leaves the surface clear. Several buildings now employ titanium dioxide, such as this elegant design in Denmark.
Meanwhile, there are also several pollution-eating billboards in existence now, such as one recently unveiled one in Peru. In the future, there are bound to be more dual-action anti-smog structures.