Mexico City struggles to clear the air
Some pollutant levels are decreasing, but car and factory emissions still trouble city
FOR decades the March 18 Oil Refinery in northern Mexico City belched out enough smoke, gases, and dirt to produce close to 5 percent of the pollution fouling the air of this notoriously polluted city.Skip to next paragraph
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Then in 1991, President Carlos Salinas de Gortari, increasingly aware of the mounting toll the bad air was taking on residents' health and the Mexican capital's reputation, announced the refinery would be closed. Soon, in place of smokestacks, a park, baseball fields, and an ecological reserve will bloom.
The case of the March 18 Oil Refinery is one small chapter in the story of Mexico City's recent battle to clean up some of the worst air-quality conditions in the world. Begun in earnest during the six-year presidency of Mr. Salinas, who took office in December 1988, the campaign has yielded some important results. It includes everything from driving restrictions and the world's second-largest air-quality monitoring system to the planting of millions of trees.
According to an assessment of Mexico City air quality released last month, average levels of some of the worst airborne poisons, including lead and carbon monoxide, have been steadily reduced. At the same time, however, ozone - an eye and throat irritant and health hazard produced in a photochemical reaction to airborne hydrocarbons - has tended to stabilize at levels that carry the designation ``poor air quality.''
Some public officials are trumpeting the encouraging results. But even as they do, critics warn that what progress has been made will be lost if more comprehensive measures aren't taken: notably to improve traffic flow, to address the city's worsening public-transit woes, and to get tougher on industrial emissions.
``Mexico City can point to some important successes, but we also have grave problems to resolve before we can talk about clean air,'' says Luis Manuel Guerra, executive director of the National Autonomous Institute of Ecological Studies (INAINE), a nongovernmental agency.
Among successful measures, he counts the requirement of catalytic converters on all cars made after 1991 and the progressive switch to unleaded gas, which by the end of this year should account for about half of gas used.
``But with ozone, all we've seen is a stabilization of the crisis,'' Mr. Guerra says. ``Unfortunately it's stabilization at very high levels.''
Public officials argue that Mexico City should be allowed to tout its progress. It is the world's most populous megalopolis (population nearly 20 million) with all the acute economic challenges of any developing-world city, plus climatic conditions that exacerbate air-quality problems.
``In five years we've reduced lead levels 90 percent, sulfur dioxide levels have been within norms equivalent to those of the US EPA [Environmental Protection Agency] for 31 months running, and for carbon monoxide it's been 27 months,'' says Fernando Menendez Garza, executive director of the Metropolitan Commission for the Prevention and Control of Mexico Valley Pollution. ``I don't know of any other city whether in the industrialized or developing world that has controlled to this extent, and in a few years time its most dangerous pollutants.''
Another recent report, based on a five-year joint US-Mexico study of Mexico City air quality, concluded that reducing certain contaminants is not enough, since that means remaining pollutants simply react to each other in different ways often causing new problems.
Called the Global Air Quality Study and directed by the Mexican Petroleum Institute, the report acknowledges that the region's particular natural conditions mean that no one strategy for combating pollution can be uniformly implemented.
Mexico City is located in a valley surrounded by mountains that have been denuded of the trees that would act as natural pollution ``processors.'' The hills trap the pollutants of 2.6 million vehicles, 30,000 industries, and dust-producing, chemical-spraying farmers.