by Oakland Ross

Mexico City -- On a clear day, you can see Iztaccihuatl.
Which is not to say that you can pronounce it.
One of two massive, snow-glazed volcanoes that crown the high blue horizon a two-hour drive southeast of Mexico City, Iztaccihuatl (pronounced Ees-ta-SEE-wah-tul) used to be perpetually invisible from the streets of this Latin megalopolis, its four connected peaks invariably obscured by the nearly permanent shroud of smog that once covered the Mexican capital, among the largest and most severely contaminated cities on the planet.
But that was then - circa 1985 - and this is now. These days, the ancient volcano can often be seen in all its glory, shimmering above the city against a Marian-blue sky, just as it has done for millennia.
How can this be?
Well, in Mexico, they've done the seemingly impossible. They've cleaned up this city's famously polluted air - to a point.
"It's still bad, but it's much better than it used to be," says Canadian Jean-Francois Prud'homme, a long-time Mexico City resident.
"It has been a long, sustained effort, but it has worked."
Twenty years ago, this overgrown conglomeration of concrete, humanity and smoke seemed bound for environmental and demographic disaster.
In those days, denizens of Mexico City - chilangos, as they are known - were reckoned to be ingesting the foulest air on Earth, most of them suffering from a hacking cacophony of respiratory complaints.
Even so, their ranks just kept swelling.
According to the worst-case predictions, the population of the city's greater metropolitan area was poised to proliferate to about 36 million people by the year 2000, all of them competing for what little oxygen was likely to survive in the rank and toxic atmosphere.
Fortunately, it hasn't worked out that way.
Mexico City in the year 2006 is huge, yes, and troubled, certainly - but it is not quite the gasping urban nightmare that some feared it would become. The population of the city's greater metropolitan area is now about 20 million.
Meanwhile, the city's air quality has done something almost no one would have predicted just two decades ago: improved.
"We are still among the 10 most-polluted cities in the world, but we are better than New Delhi or Bangkok," says Jorge Bustamante, who works with a non-governmental organization here that studies air pollution in big cities. "We used to be in first place."
Over the course of a single generation, and thanks in large part to a concerted campaign against the worst excesses of the internal-combustion engine, Mexico's capital has gone from being the dirtiest city in the world to what it is today - still an unpleasant place to draw breath but not as unpleasant as before.
In April 1992, for example, atmospheric monitoring stations scattered around the city recorded high or "bad" concentrations of pollutants on 11 occasions, including two instances when the air quality was "muy mala" - serious enough to aggravate existing respiratory ailments in some people.
Eleven years later, in April 2003, a "bad" reading - ozone in this case - was recorded on just one occasion.
"I first came here in '93," says a U.S. resident of the city, "and the air is much better now."
But not what anyone would call good. Polluted or "unsatisfactory" air remains an abiding feature of Mexico City life, causing sensitive people to suffer irritation to their eyes, noses and throats just about every single day.
By way of comparison, the air in downtown Toronto caused a similar degree of annoyance on a total of 67 days last year, or about 20 per cent of the time. The air over Nathan Phillips Square and environs was "poor" - roughly equivalent to "bad" in Mexico City - on seven additional days, almost all of them during the summer.
In the Mexican capital, smog is at its worst right now, during the wintry dry season, when there are few if any rains to cleanse the city's atmosphere and when thermal inversions - masses of cold air squatting above the high intermontane basin that surrounds the city, allowing pollutants no means of escape - are a frequent occurrence
"During the rainy season, it's fine," says JoAnne Butler, head of the Canadian Chamber of Commerce in Mexico City. "But these winter days can be difficult."
When the city's air quality index hits unacceptable levels, ozone is often the main culprit.
A major component of smog, ozone is generated at ground level when by-products of faulty combustion interact with ultraviolet light. It has proved to be a stubborn pollution problem here, exacerbated by the city's lofty perch at 2,240 metres above sea level.
Still, the terse travel advice once issued as a matter of course to prospective visitors to the Mexican capital, "don't breathe," no longer seems to have quite the urgency it once did.
In recent years, many harmful pollutants that once clogged the city's air - carbon monoxide and lead, in particular - have been hauled down to tolerable levels, but other contaminants persist. Ground-level ozone, for example, is still a problem about 80 per cent of the time, while "suspended particles" - minute specks of matter that can do serious injury to humans - are at unacceptable concentrations one day out of three.
"It's still a risk to raise children here in Mexico City," says Bustamante. "We still have a long way to go in nitrogen oxide, ozone and suspended particles."
Authorities here struck a major blow against pollution in 1991 when they shut down and dismantled the 18 de Marzo petroleum refinery, which had been operating within city limits. They also took aim at the capital's notoriously cranky and crepitating automobiles, gradually getting rid of older cars that used dirty leaded fuel, while limiting the number of vehicles that could operate in the city on any given day.
Nowadays, all cars and trucks here are legally required to be equipped with catalytic converters, devices that help engines burn fuel more efficiently. Since 1997, only unleaded fuel has been available at Mexico City gas pumps, and efforts continue to reduce the sulphur content of local gasoline.
Last year, in an effort to speed public transit and reduce dependence on private cars, the city launched the first route in a planned network of dedicated bus lanes running along major urban arteries, a project called Metro Bus.
The inaugural line runs straight through the city for nearly 20 kilometres, along Avenida Insurgentes, and it's a traveller's delight, especially given Mexico City's chronically congested streets.
Brand-new articulated diesel buses shuttle swiftly along the open lanes, from Indios Verdes to San Angel, making stops at airy stations with raised platforms and cantilevered glass-and-steel roofs.
According to Bustamante, the city plans eventually to operate as many as 30 similar routes.
He credits the sheer din of public outrage for this and other advances against pollution.
"The interesting thing was the public alarm," he says. "It wasn't the scientists alone."
It has also helped, he says, that authoritarian Mexico has gradually been democratizing in recent years.
"If it hadn't been for democratization," Bustamante says, "we would be like Bangkok. We would be talking about people collapsing in the streets because they couldn't breathe."
The air in Mexico City may still be far from good, but it is not quite as bad as that - and, on a clear day, you can even see Iztaccihuatl.

The Toronto Star, 17 April, 2006