A breath of fresh air

The capital’s filthy atmosphere has improved at last

HEMMED in by mountains and volcanoes, Mexico City is the perfect smog-trap. At its altitude of 2,250m the air is already thin; on days when the toxic “cream”, as the familiar brown cloud of pollution is locally known, descends on the city, it is hard to breathe. Locals used to joke that the only life that could survive in the skies was jumbo jets.

Yet the smog is lifting. The average concentration of ozone, one of the most common pollutants, is about half its level in the early 1990s, when the air was at its dirtiest (see chart). In those days the national ozone limit of 0.11 parts per million was breached for at least an hour on nine days out of ten. Yet last year over half the days were below the cap. Joggers are back in parks and wildlife is airborne once more: a hummingbird regularly looks in on The Economist’s offices.

More recently, a car crackdown has helped: old bangers are checked twice a year for emissions, and all but the newest cars are forbidden from driving in the city on one day of each week. Every Sunday 22km of roads in the centre are roped off for bikes and pedestrians. From next year taxi drivers will be offered tax incentives to use electric technology. Mexico City’s pollution has been so severe that cleaning up the environment “is not a theoretical thing—it’s about life and death,” says Marcelo Ebrard, the mayor. Read more at www.economist.com