Little by Little, Breathing Easier in Mexico City

MEXICO CITY —  Quietly but steadily, Mexico City made significant progress in reducing its infamous air pollution during the 1990s, thanks to one of the world’s most aggressive anti-smog initiatives.

Metropolitan officials disclosed pollution data this week that shows 1999 was the least-dirty year of the decade here for the air, with the fewest emergency days and the most days within acceptable norms.

To be sure, Mexico City remains badly polluted. Ozone, one of the most serious threats to health and the worst airborne offender in the capital, was still above acceptable levels on 300 days last year. And some programs have lagged, such as the conversion of smoke-belching buses from gasoline and diesel to cleaner-burning fuel sources.

But federal and local experts agree that the trend is strongly in the right direction compared with the worst days from 1990 to 1992, when pollutants hit emergency levels on as many as 177 days a year. During 1999, even after a stricter threshold had been introduced the year before, pollutants triggered emergencies on just five days.

The achievement suggests that even huge Third World cities can begin to reduce pollution if they muster the will.

Better air quality had a payoff in improved health, said Alejandro Encinas, secretary of the environment in the Federal District. “Eye and bronchial illnesses were less severe and placed less demand on medical services and hospitals,” he said while releasing the latest figures.

The Federal District, which is similar to the U.S.’ District of Columbia, worked with the adjacent state of Mexico during the 1990s to attack pollution. The Federal District is home to 8.5 million people; 10 million more live in the state within the Valley of Mexico.

The valley is surrounded by mountains and sits at 7,300 feet above sea level. Housing is spread out, commutes are long and roads are congested. There is little wind to disperse pollutants, and thermal inversions are common during the winter.

Conditions for pollution, in short, are excellent. What’s more, Mexico’s mid-1990s economic crisis made it more difficult for people to afford new vehicles, which tend to produce less pollution. The Private Sector Center for Environmental Studies and Sustainable Development reported last year that 24% of vehicles in Mexico City are pre-1980 models, which can release as much as 70 times more pollutants than new models.

Against these obstacles, the local governments have carried out two five-year programs to improve air quality. Some measures were harsh and controversial, such as the “Today You Can’t Drive” law. It takes 20% of all vehicles without catalytic converters off the roads each weekday, and halts as many as 40% of vehicles on emergency days.

In the early 1990s, lead was removed from gasoline sold in the valley. The government supports reforestation efforts by paying residents about 10 cents for each tree planted that has been growing for at least a year. Inspections of factories to reduce pollution doubled in 1999 to 1,521.

Luis Manuel Guerra, head of the independent National Institute of Ecological Studies and a frequent critic of government anti-pollution efforts, said Mexico City “has achieved significant advances.”

“There is a political will here,” he said, “that has translated into measures that have changed the behavior of the people.”

But the real test is whether pollution declined, and there the evidence is persuasive. The average daily ozone reading fell from 197.6 in 1991 to 144.9 in 1999, according to the city’s measurement service, on a scale equivalent to California’s system. The acceptable air quality norm of 100 points for ozone is equivalent to exposure to 0.11 parts per million for one hour.

Similar progress occurred last year in reducing small particulates, which can penetrate the lungs and cause serious health problems. There was a jump in small-particulate pollution in 1998, probably fueled by forest fires, when readings were below 100 points on just 176 days. In 1999, there were 345 days below 100.

The valley’s environmental authority is now developing its third strategic plan.

“We are going to have even stricter, tougher norms,” vowed Gustavo Olaiz, federal director general of environmental health. “We can’t forget that not having emergencies does not mean we have good air quality, nor does it mean we no longer have health problems. We have to keep working toward meeting the norms.”

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A Clear Trend

An aggressive campaign has begun to reduce Mexico City’s high levels of air pollution.

Average daily maximum ozone levels, on scale in which below 100 points is acceptable and 240 triggers a pollution emergency.*

Number of days of acceptable ozone levels.

* Emergencies triggered by reading of 350 points until 1995, and then 250 points until last year.

Source: Mexico City Environment Ministry