Mexico City Vanishing Into Its Own Haze : Unchecked Rural Migration Chokes Area in Overpopulation, Pollution

Mexico’s supercity, a noisy jumble of traffic, people and pollution, lost sight of its own surroundings as it grew swiftly into what will soon be the world’s biggest urban sprawl.

Only on a rare day does the heavy smog lift sufficiently to give greater Mexico City’s 17 million residents--roughly a fourth of the national population--a view of the snow-capped volcanoes that ring their valley, a magnificent panorama they took for granted just a generation ago.

Before the end of this decade, Mexico City is expected to pass the Tokyo-Yokohama urban region as the world’s largest metropolitan area. Despite a stepped-up government campaign to persuade the rural poor to stay away, the United Nations projects that Mexico City’s population--only 3.1 million in 1950--may reach 26 million by the year 2000.

As in many cities of the developing world, officials here concede that too little attention was paid to the environment too late as the rapidly expanding population simply swamped the ability to meet people’s needs.

Mexico City has enormous problems of water supply and sewage, transportation and housing, education and employment. A gas explosion and fire last November that killed at least 499 people illustrated the perils of overcrowding and the lack of environmental controls. Bleak slums of squatters spread out over the city’s arid plateau.

But the trademark of Mexico City is what obscures the landmarks of Mexico City--the smog, generally regarded as among the world’s worst.

The city’s natural setting, in a basin 7,392 feet high hemmed in by mountains, is a major contributor to its notorious pollution problems. About 40% of Mexico’s industry is located here in the Valley of Mexico, much of it to the north of the city.

Trapped Contaminants

In a pattern repeated daily, winds pick up the contaminants in the industrial zone and take them south into the city before blowing them out of the valley. On still days, the air can be trapped in the valley.

Power plants and refineries pour hundreds of thousands of tons of sulfur dioxide and solid particles into the air over the valley. Small and mid-size industries send a tremendous amount of dust into the air from the cement, bricks, tiles, asbestos and asphalt they produce, says Armando Baez, chief of the air pollution department at the National University of Mexico. And metallic fumes spew from the area’s many foundries.

At least 2.5 million vehicles travel the city’s streets, all but a few without emission-control devices and many in poor working order, which adds to the pollution.

The thinner air at this altitude multiplies the harmful effect of the toxic fumes.

In the United States, Environmental Protection Agency standards permit an annual mean particulate count--a measure of dust and other solids in the air--of 75 micrograms per cubic meter. U.S. specialists note that Mexico’s maximum permissible count is 275 micrograms per cubic meter, and that actual readings in Mexico City often exceed that level.

Brown Specks, Then Smog

Arriving over the Mexican capital by air offers a graphic demonstration of the problem: First, wisps of brown appear in the sparkling blue sky. Then, as the plane flies on, the wisps become an angry storm cloud of smog that swallows up the view of the pristine volcanic peaks.

The government has done little to control the problem. Officials say they cannot afford costly pollution controls at a time when Mexico is in its worst recession in a half-century and jobs are a priority. And in Mexico City, the poor have at least a chance at finding work--or think they do.

“There are political solutions to this,” Baez said. “It’s not a scientific or technical problem.”

The precise impact on human health remains uncertain. Although Baez said no studies have yet been completed establishing ties between pollution and medical problems, some doctors report an alarming increase in cases of asthma and other respiratory disease.

As in Southern California during Santa Ana wind periods, residents here complain of sore eyes, scratchy throats and sinus trouble. A drive down a traffic-jammed street may well produce a throbbing headache.

Hazardous Diplomacy Pay

Because of the pollution, the State Department last year decided to give extra benefits to Foreign Service employees here, adding six months’ credit toward retirement for each year worked in Mexico City. The program is not available in any other city.

Not just the air is polluted. Such books as “Disaster Zone: Let’s Save Our City” document the problems of solid waste in a city where 3 million people do not have sewage facilities, where the water is polluted and scarce. Noise pollution and acid rain are only starting to be discussed.

The most popular Mexican movie of 1983 was “El Milusos--The Jack-of-all-Trades,” a comedy about a peasant who comes to the city and finds only squalor and hard luck. The government has aimed its newest anti-growth campaign at such discontented new urban dwellers, offering them 59 mid-size cities as alternatives to the overburdened capital.

“These cities are ready to receive you and your family,” an advertisement says. “If you wish to eat better and be healthier, you only need to take the spoon by the handle. The information is ready showing you the path to take.”

But past programs, including tax incentives for industries to locate elsewhere, have done little to slow Mexico City’s growth. Not even the overall reduction in the nation’s annual population growth rate--from 3.5% in 1970 to 2.4% today--helped much. Despite family planning programs, rural Mexicans still migrate here at a rate believed to approach 1,000 a day.