New building material 'eats smog'

New building material 'eats smog'

Twenty years ago, the air in Mexico City was considered the worst in the world. It was so badly polluted that on one day, birds fell dead out of the sky. Since then, the city has worked to clean up its act. But traffic remains a major problem. Streets are still clogged with carbon-emitting vehicles. But one new building can counteract the effect of one-thousand cars. Nick Parker explains how.