Smog Blog: Mega Mexico City in Tough Pollution Fight

Vacationing here in Mexicoâ''s Federal District, one of the worldâ''s biggest of megacities, you canâ''t ignore the bad air. Last year, in IEEE Spectrum magazineâ''s special issue about megacities, Erico Guizzo drew attention to the innovative way Sao Paulo has introduced special reserved bus lanes to make bus travel speedier and discourage private cars. In Mexico Cityâ''s Insurgentes, the main thoroughfare that traverses the city much as Broadway cuts diagonally all the way up Manhattan, lanes reserved for express buses also are to found.

Those dedicated bus lanes are just one of the many ways that Mexico City keeps a lid on inner-city traffic and automotive emissionsâ''this splendid city has an outstanding subway system that the French and which costs just 20 pesos to ride (two U.S. cents) and ubiquitous minibuses (including the lovely new Volksbus built by VW). But in a sprawling metropolitan area of close to 20 million people, at a high altitude where the air is thin to begin with and catalytic converters work poorly, and where so many antiquated cars and trucks belch putrid fumes, curtailing air pollution is an uphill battle.

Five years ago, before Guizzo graced IEEE Spectrum with his presence, he wrote an article for a competitor publication (that we naturally prefer not to name) about how Luisa T. Molina and her husband the Nobelist Mario Molina had organized a program at MIT and Harvard to study air pollution in major urban areas worldwide; they have done closely related work in a joint program in La Jolla. Erico described how the Molinas had vans equipped with state-of-art monitors drive around Mexico City to test air and identify mobile and point sources of pollution.

That article came vividly to mind two days ago as I drove back into the city with my wife and son from Teotihuacan, the spectacular 2000-year-old complex of pyramids and temples northwest of the Federal District. We had the bad luck to get caught in a highway bottleneck, where a superhighway was being extended. For close to an hour and a halfâ''resulting finally in a little burst of road rage on my part, a minor moving violation, the threat of a ticket, and the usual bribe paid to a well-organized group of extortionist traffic copsâ''we sat nearly motionless behind decades-old trucks belching black diesel smoke.

With some feeling of chagrin we thought and talked about how when the superhighway was completed, there would be fewer trucks sitting motionless spewing pollutantsâ''but there also would be all the more trucks and cars speeding along the new highway into and out of the city.

That night we were blessed with a gigantic thunderstorm, and when we woke the next morning, the sky over Mexicoâ''s downtown was miraculously clear blue. I took my son up to the top of the television tower, to catch a rare glimpse of the two sacred volcanoes that loom over the city, almost always invisibly.

Astonishingly and yet not so astonishingly, when we got to the top of the tower, everything right under us in the inner city was beautifully clear. But all around there was a doughnut of pollution so dense, we not could see through or over it to Popocatepetl and Ixtaccihuatl (Popo and Ixta). In the inner city with its fabulous subway system, adorable VW minibuses, and dedicated express bus lanes, the air was almost pristine. But all around, where the city is sprawling cancerously in every direction, the air was perhaps worse than ever.


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