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Megacity breathes easier after smog crackdown

Mexico City once had the world's worst air, with skies so poisonous birds dropped dead in flight. Today, efforts to clean the smog are showing visible progress.
Image: Fine Arts Palace in Mexico City
An aerial view of the Fine Arts Palace in Mexico City in February shows how the government’s attempts to battle air pollution are paying off. Ronaldo Schemidt / AFP - Getty Images
/ Source: a href="" linktype="External" resizable="true" status="true" scrollbars="true">The Washington Post</a

This megalopolis once had the world's worst air, with skies so poisonous that birds dropped dead in flight. Today, efforts to clean the smog are showing visible progress, revealing stunning views of snow-capped volcanoes – and offering a model for the developing world.

As Mexico prepares to host world leaders at a U.N. climate-change conference later this year, international experts are praising the country's progress. Many say its determined efforts to control auto emissions and other environmental effects of rapid urbanization offer practical lessons to cities in China, India and other fast-growing countries.

International officials say steady improvement of Mexico City's air could bolster President Felipe Calderón's bid for a leadership role among developing countries seeking to address global warming.

"We have seen a lot of improvement. It is very clear," said Luiz Augusto Cassanha Galvao, a senior environmental officer at the Pan-American Health Organization. "On a scale of one to 10, they were at 10, and now they're at five."

Example to others
Mexican officials have attacked the root causes of pollution that plagues many large urban centers with spiraling growth.

They plan to further reduce vehicle emissions, which are the city's greatest source of pollution. Pemex, the state oil monopoly, plans to build a $9.3 billion plant to produce low-sulfur fuel. Mexico City Mayor Marcelo Ebrard is expanding the low-emissions Metrobus system, which has eliminated 80,000 tons of carbon monoxide annually since 2005. Officials plan to add hybrid buses. A suburban train system is to replace hundreds of thousands of vehicles.

The potential payoff for such efforts is now in sight: Mexico City does not even rank among the top 10 polluted cities worldwide, said Walter Vergara, a leader of the climate-change team at the World Bank, which is aiding public transportation projects in Mexico.

Mexico City appears to have cut most of its pollutants at least by half, said Miguel Naranjo, a Panama City-based official of the U.N. Environment Program, while recent studies show a number of cities in China and India recording higher levels of the most serious pollutants.

"They are having the same problems Mexico had in the past," Naranjo said. "They are growing faster than their capacity to adjust. They face a big challenge not to repeat the mistakes of Mexico."

In 1992, the United Nations declared Mexico City the most polluted on the planet. High ozone levels were thought to cause 1,000 deaths and 35,000 hospitalizations a year. Thermal inversions held a toxic blanket of dirty air over a grimy city that seemed to embody the apocalyptic "Makesicko City" of the fiction of Mexican author Carlos Fuentes.

Mexico was forced to act. It replaced the city's soot-belching old cars, removed lead from gasoline, embraced natural gas, expanded public transportation, and relocated refineries and factories.

Change was gradual, but the pace has quickened in recent years.

Lead drops by 90 percent
The presence of lead in the air has dropped by 90 percent since 1990. Suspended particles – pieces of dust, soot or chemicals that lodge in lungs and cause asthma, emphysema or cancer – have been cut 70 percent. Carbon monoxide and other pollutants also have been drastically reduced.

"It is no longer an emergency situation," said Raul Estrada, a spokesman for Greenpeace in Mexico, "though obviously, it is not 100 percent satisfactory."

In March, the Mexico City Atmospheric Monitoring System, which has pollution sensors all over the city, began to measure additional chemicals, such as the highly toxic benzene, that are suspected to contribute to Mexico City's ozone problem.

Ozone levels have dropped 75 percent since 1992, but they still exceeded international standards for a total of 530 hours last year.

"You shouldn't even have one hour of high ozone levels in an entire year, and we have 530 hours," said Humberto Bravo Álvarez, one of Mexico's most respected air pollution experts. Bravo said corruption, such as people paying off emissions inspectors, has reduced the impact of the new controls.

Had Mexico not taken action, "it would be living hell," said Exequiel Ezcurra, a former head of Mexico City's National Institute of Ecology who is now a professor at the University of California, Riverside.

Ezcurra attributes much of the improvement to a requirement that Mexico-based auto manufacturers put catalytic converters on cars produced for the Mexican market. Now Mexico must require all diesel vehicles to be retrofitted with a filter that is the equivalent of a catalytic converter, he said.

"If the government decides to do something about it, it can be done," said Nobel Prize-winning air quality expert Mario Molina. "There's really no excuse not to do more."

More to do
Experts say Mexico must do more, simply to hold on to its progress in the face of uncontrolled growth.

Cars have doubled to more than 4.2 million. New suburbs are endemic.

Mexico City's geography adds to the problem; the city of more than 20 million is cradled in a 7,300-foot-high bowl, surrounded by peaks higher than 17,000 feet that trap pollutants.

But experts say many places overcame similar challenges. European cities, for example, halved pollution in recent decades by dramatically reducing coal fuel.

"Simple measures that enormously reduce pollution are feasible, and they are not expensive," said Michal Krzyzanowski, an air quality adviser for the World Health Organization.

"It is not the destiny of mankind to live in polluted cities."