A scientist and an award winning poet, both at the University of Sheffield, have made a giant poster that uses nanotechnology to gobble up pollution.
It can absorb the poisonous compounds from around 20 cars each day if you put it by a busy road.
Prof Tony Ryan (the science expert) and Prof Simon Armitage (the words expert) came up with the idea to highlight one possible way to cut disease and save lives by taking poisonous compounds from the air in our towns and cities.
First the science bit: The 10m by 20m poster is coated with microscopic, pollution-eating nanoparticles of titanium dioxide. It's the same stuff they use for self-cleaning windows, apparently.
Prof Ryan told me that when light hits them they get excited, react with oxygen, and wash the pollution out of the air.
It doesn't get rid of all the nasties from traffic, but it will eat up things called nitrogen oxides, which you can't see or feel but which have been linked to breathing problems including asthma.
But it's not free of course.
Professor Ryan comments: "If every banner, flag or advertising poster in the country did this, we'd have much better air quality.
"It would add less than £100 to the cost of a poster and would turn advertisements into catalysts in more ways than one."
He's also working on another idea, which is to add the nanoparticles to washing powder, so that your clothes soak up these poisons while you walk along.
Two pairs of jeans could apparently clean up the nitrogen oxides from one car. And you wouldn't be able to see or feel anything different.
Now for the words. Simon Armitage, who's professor of poetry at the university, has written a poem to go on the poster. It's called "In Praise of Air" (see box).
The poster will be on display in Sheffield for the next year.