According to the report "Air Quality in Latin America: A Panorama" published in 2012 by the International Clean Air Institute, some 15,000 people died prematurely in Mexico in 2008 due to pollution, placing it third on the list of Latin American countries.  A great deal of that pollution comes from the nation's capital, which two decades ago the UN called the most polluted city on Earth.  But the winds may be changing direction: this Wednesday, Mexico City won the Air Quality prize at the City Climate Leadership Awards in London for its program ProAire, which has aimed to reduce emissions from automobiles and industrial complexes, contain urban sprawl and carry out public awareness campaigns on the topic of pollution.  

Since ProAire launched in 1990, the city says it has closed the most polluting factories and banned the use of cars one day per week in the metropolitan area; since 2005, its Metrobus system, the longest in Latin America, runs in designated lanes through the city's most central zones, and a recently launched Ecobici bike-sharing program is also the largest in the region.  In four years (between 2008 and 2012), Mexico's capital recorded a 7.7 million-ton reduction in carbon emissions, surpassing a target of 7 million.  "Once ranked the most polluted city on the planet, Mexico City proves that long-term determination and a comprehensive approach can make a huge difference in the air quality of a megacity," said the awarding committee.  But the city still produces 150 percent of the ozone contamination recommended by the World Health Organization, according to the International Clean Air Institute's 2012 report.  And the award committee didn't just applaud Mexico City's "outstanding commitment" to an increasingly ambitious set of ProAire programs, but also its government's acknowledgement that more needs to be done.  "Although the city has seen definite progress," the committee wrote, "it recognizes there is still a long way to go."

Part of the problem has to do with Mexico City's geography: wind circulation in the capital is very poor, as it sits in a basin ringed by mountains.  According to the Food and Agriculture Organization (FAO), that allows thermal inversion to occur - a process in which warm air settles over cooler air closer to the ground and prevents pollutants from escaping the city's environs.  The other factor is the army of automobiles - about 2.9 million, many of them old and poorly maintained - driven by about 17 million inhabitants.

According to National Geographic, the awards took place at the Crystal -- a center on sustainable urban development built by the German engineering firm Siemens, which put on the event together with the C40 group of megacities that take action to address climate change.  Mexico City was one of ten cities to win prizes.   

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