Mexico's environment

A breath of fresh air

The capital’s filthy atmosphere has improved at last

Jul 29th 2010 | MEXICO CITY

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.

The revival began with the closure of some of the city’s heavy industry. The oil refinery in the borough of Azcapotzalco, which was said to belch out up to 7% of Mexico City’s air pollution, was shut in 1991. Some of its land was converted into a park.

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.

The air is still dangerous. “The only thing that is good is the trend,” says Arón Jazcilevich, an atmospheric scientist at the National Autonomous University of Mexico, who says he checks pollution readings before going running. He fears that in the state of Mexico, which borders the capital and contains most of its suburbs, regulation of industry and checks on motorists are weaker. The capital ought to improve public transport links with its neighbour too, he adds.

As the capital’s air improves, attention will turn to Mexico’s other big cities. One of the reasons for Mexico City’s infamy was its diligence in recording its own failings: the government keeps hourly readings of eight pollutants across 34 weather stations, some going back to 1986. Less well-measured places may actually be worse. Last year Monterrey, the country’s industrial capital, clocked a higher reading than Mexico City on its index of particles smaller than 10 microns, a form of pollution that is no less dangerous than ozone.