Not even a decade ago, the atmosphere surrounding Mexico's capital was so toxic that birds died midflight and many of the city's residents were forced to walk the streets in surgical masks. But today, things are looking brighter: The skies are sometimes blue, and the volcanic range that rings the city has reemerged from the haze.
"We're in the best position we've ever been in," says Luis Roberto Acosta, director of Mexico City's International Environmental Monitoring Institute (SIMA), confirming that the skies are clearing above North America's largest city.
On Oct. 15, this city will mark two straight years without a smog emergency, something that would have been unthinkable a decade ago.
Mexico City is reaping the benefits of seeds planted in 1986. Then, the government began to heed local and international alarm bells about the worsening situation. It established greenbelts, phased out leaded gasoline, introduced emission standards for vehicles, and passed legislation to pull cars off the streets and shut factories when pollution levels reach dangerous heights.
Thanks to those efforts, the key pollution index, which measures the amount of poisonous ozone gas in the air, has fallen from an average of 211 points in 1991 to 104 so far this year. But, says Mr. Acosta, "better doesn't mean good." He worries that after 15 years of slow but steady improvement, a sense of crisis could be lost. "We've become desensitized. By North American standards, the air here is still terrible."
Despite the drop in the ozone count, Mexico City's average remains nearly double that of the most polluted US cities, where any reading above 100 would be considered a public health crisis.
Last year, the ozone count here was above 100 on 243 days. Getting it consistently below that mark will require tougher rules to get the most-polluting cars off the roads, and major investments in public transport to give drivers an alternative.
"We've reached the point where making progress is going to get a lot more expensive," says Rafael Ramos, director of air-quality management for the Mexico City government. About 80 percent of the city's pollution is caused by its 3.5 million vehicles. Mr. Ramos says most of that pollution comes from the roughly 50 percent of them that are older than 10 years.
Ernesto Rodriquez, the driver of one of this city's aging cabs, knows cars like his Volkswagen Bug are a problem, but he's not going to leave the road. "There's no money for new cabs, and I'd be out of a job if they took this one away," he says.
A lengthy political fight is likely before older cars are taken off the road. "The question is: Are people willing enough to make personal sacrifices for cleaner air?" says SIMA's Acosta.
Although the improvement in air quality is largely due to government efforts, the weather has also been favorable. The city, which is surrounded by peaks that keep the wind out and emissions in, has had steady rainfall which helps clean the air. But Ramos warns that a major drought could lead to a drastic short-term deterioration in air quality, which is why he wants to see tougher standards imposed soon.
He's especially worried because people continue to pour into the valley, already home to about 20 million. Acosta agrees: "We have no controls on growth, which is our biggest problem. If we're not careful, we could get pushed back to the bad old days."