Terrific News in Mexico City: Air Is Sometimes Breathable
nytimes.com
January 5, 2001
By TIM WEINER
MEXICO CITY, Jan. 4 The atmosphere is infamous here. For decades it
has been a danger to the millions inhaling it. But now something
new is in the air.
It seems to be getting fresher or at least less foul. This would
be quite a change: in 1992, the United Nations called Mexico City's
air the world's worst.
"That's no longer true," said Dr. Mario J. Molina, a Mexico City
native leading the most intensive study of the problem yet
undertaken. Dr. Molina, a chemistry professor at Massachusetts
Institute of Technology, shared the Nobel Prize in Chemistry in
1995 for showing 20 years earlier that chlorofluorocarbons, then
widely used in aerosols, refrigerators and air conditioners, were
depleting the ozone layer.
"There are data that suggest that the air may be improving," said
Dr. Molina. Indeed, there has been no smog alert for 15 months.
Lead, carbon dioxide and sulfur dioxide in the air are down.
Other pollution levels are still often unacceptably high, but on
many days, especially weekends, the air is sometimes clear enough
to breathe with pleasure this in a place where it contributed to
the deaths of hundreds of people in one terrible week four years
ago.
"You would have expected pollution levels to increase if you look
at the increased number of cars, people and economic activity in
the past three years," Dr. Molina said.
They have not. While fair winds and cleansing rains may take some
credit, so do increasingly stringent environmental rules, which
call for cleaner fuels, catalytic converters on cars, emissions
tests and rules on industry.
The air has tested the limits of human endurance. The air quality
index runs from zero to 500, zero representing the Garden of Eden,
and 300 or more representing hell on earth. Below 100 is officially
satisfactory, 101 to 200 is unsatisfactory, and anything higher is
dangerous and a potential threat to life. In the mid- 1990's, it
exceeded 100 about 9 days out of 10; simply breathing was like
smoking two packs of cigarettes a day. Sometimes it went off the
charts: once, in 1996, it spiked at 394. There are good days and
bad days, and the pollution level still often exceeds 100. But on
Wednesday, in the heart of Mexico City, it peaked at 69, with a low
of 9. Levels of sulfur dioxode, nitrogen dioxide, carbon monoxide
and particulates were all 40 or less. And winter is normally the
worst time of year for air pollution.
Mexico City still rates as one of the planet's more toxic places,
along with Beijing, New Delhi, Jakarta, Bangkok, Tehran and other
mega cities with too many people, too many cars, too many polluting
industries and too few coordinated efforts to clear the air.
This is where Dr. Molina and his wife, Dr. Luisa T. Molina, a
research scientist at M.I.T., come in. They are leading the Mexico
City Case Study, part of a program at M.I.T. for exploring the
problems of megacities in the developing world. With close to $2
million from M.I.T., the National Science Foundation and the
Mexican government, they have brought together scores of government
officials, scientists, engineers, economists and other experts to
figure out how to cut the smog.
No mad scientist could think up a better machine for creating air
pollution than this capital of nearly 20 million people. It sits in
a bowl 7,400 feet above sea level, ringed by mountains, under a
tropical sun a petri dish for brewing and trapping bad air. The
miasma spews from three million cars, buses and trucks, and from
thousands of dirty companies and dump sites. They fill the air with
toxic chemicals and tiny particles of everything from heavy metals
to human waste.
Mexico's leaders spent most of the 1970's and 1980's ignoring the
pollution. The Institutional Revolutionary Party, which until last
year had enjoyed a monopoly on power for decades, had little
incentive to be accountable to the public, to listen to scientists
or to press for changes, especially ones that could thwart economic
development.
This attitude filtered down to the public in the form of fatalism,
a disbelief that anything but a strong wind could clear the air.
Pemex, the national oil company, which produces much of Mexico's
gasoline, also spent years "sort of denying the problem," Mario
Molina said. "There were statements that there was no pollution
problem."
Not until 1995 did federal health authorities state clearly that
the air was unhealthy. That year, the World Bank financed a study
suggesting that high ozone levels alone were responsible for as
many as 1,000 premature deaths and 35,000 hospitalizations for
respiratory diseases each year in Mexico City. Those numbers
appeared conservative when, in November 1996, a five-day smog
emergency sent 400,000 people to hospitals and contributed to the
deaths of 300 or more, according to city officials.
So what has gone right?
The gasoline is cleaner than it was a
few years ago. Pemex took the lead out, upgraded its refineries,
and since 1996 has quadrupled its gas imports from the United
States. That cleaner fuel from the United States accounts for as
much as a quarter of the gasoline burned in Mexico today.
New cars have catalytic converters, which reduce carbon monoxide
and nitrogen oxide. Some large industries have become cleaner or
moved away from Mexico City. A hulking oil refinery within the city
limits was closed in the face of political pressure from labor
unions.
F. Sherwood Rowland, one of two other scientists who shared the
1995 Nobel Prize in Chemistry with Dr. Molina, demonstrated that
same year that leaks of liquefied petroleum gas, or L.P.G., used
for cooking and heating in almost every home in Mexico City, were a
major factor in the poisoning of the air.
People burn more than two million tons of L.P.G. a year in Mexico
City 70,000 barrels a day. Pemex reformulated the bottled fuel,
removing butylene, a volatile and environmentally harmful
ingredient, but the gas still leaks from millions of poorly
maintained pipes and tubes, and it represents perhaps 15 percent of
the air pollution in Mexico City, the Molinas say.
Then in 1997 the first popularly elected municipal government took
power in Mexico City. Its left-of-center leaders were more amenable
to stiffer environmental regulations, the Molinas say.
The Mexico City study, which will continue for another two years,
suggests that "new technology exists that is clean enough to solve
the problem to a significant extent," Mario Molina said. "But it's
expensive. The main one would be clean cars, buses, trucks I'm
just talking about plain standard internal combustion engines.
Then, the next set of changes are harder: repairing leaks of L.P.G.
in peoples' homes, replacing pilot lights, the use of solvents in
small industries and homes. For industries, you need clean
furnaces, to remove nitrogen oxide and other pollutants."
Things had gotten so bad in Mexico City that some scientists
seriously proposed blowing a hole in the mountains on one side of
the capital and setting up giant fans on the other to push away the
smog. Dr. Molina suggests that with clear-air regulations and
cleaner government to enforce them such desperate measures may
not be necessary.
Thirty years ago, the air in Los Angeles was worse than it is in
Mexico City today, Dr. Molina says. "Mexico City's air can improve
as much as Los Angeles's did, and in a shorter time," he said.
"That's a goal that can be achieved."
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