Page 468 - Environment: The Science Behind the Stories

CEnTRAl CASe StUdy

Clearing the Air in L.A.

and Mexico City

“I left L.A. in 1970, and one of the reasons
California UNITED STATES I left was the horrible smog. And then they
cleaned it up. That was one of the greatest
things the government has ever done for me.
You have beautiful days now. It’s a much, much
Los Angeles nicer place to live.”
— Actor and comedian Steve Martin, speaking to Los
Angeles Magazine
Gulf of
Mexico
MEXICO “This city can be a model for others.”
— Mexico City Mayor Miguel Ángel Mancera
Pacific
Ocean

Mexico City

Los Angeles has long symbolized air pollution in Americans’ (7350 ft) above sea level—solar radiation is intense, which
minds. Smog blanketed the city in the 1970s, 1980s, and worsens the formation of urban smog. Mexico City environ-
1990s, a result of the exhaust from millions of automobiles mental chemist Armando Retama likens his hometown to “a
clogging its freeways. But Los Angeles has improved its air casserole dish with a lid on top.”
quality, thanks to policy efforts and new technologies. Today Despite all the challenges facing the world’s third-largest
L.A. still suffers the nation’s worst smog, but its skies are metropolis, Mexico City’s 20 million people have fought back
clearer than they have been in decades—and its air is cleaner and turned things around. A series of mayors took bold action
than in many of its “sister cities” elsewhere in the world. to clean up the air, and today Mexico City is enjoying a renais-
Devised to foster peace and understanding among sance. As the smog begins to clear, revealing beautiful views
nations, the Sister Cities program links hundreds of American of the snow-capped peaks that ring the valley, the city has CHAPTER 17 • AT m os PHER i C sC i E n CE , Ai R Qu A li T y, A nd Poll u T i on Con TR ol
cities with foreign counterparts through shared government become a model for other cities seeking to fight pollution.
visits and cultural ties. One of L.A.’s sister cities is Mexico City, Efforts began in the 1990s when city leaders shut down
the capital of Mexico. Alas, one thing these two cities share is an oil refinery and pushed factories and power plants to shift to
smog. cleaner-burning natural gas. Lead was phased out from gaso-
Not long ago Mexico City suffered the most polluted air line, the sulfur content of diesel fuel was reduced, and pollution
in the world. On bad air days throughout the 1990s, residents control technologies such as catalytic converters were phased
wore surgical masks on the streets, teachers kept students in for new vehicles.
inside at recess, and outdoor sports events were cancelled. Levels of many pollutants fell, but as the city grew in popu-
Birds were said to die in flight, and children used brown cray- lation and sprawled across the valley, smog from automobile
ons to color the sky. Each year thousands of deaths and traffic persisted. In response, city officials stepped up vehi-
tens of thousands of hospital visits were blamed on pol- cle emissions testing and upgraded taxis and city vehicles to
lution. Mexican novelist Carlos Fuentes called his capital cleaner models. To monitor air quality, 34 sampling stations
“Makesicko City.” were set up across the city, sending real-time data to city
As in Los Angeles, traffic generates most of the pollution engineers.
in Mexico City, where motorists in 6 million cars sputter across In 2007 Mayor Marcelo Ebrard accelerated efforts as part
miles of urban sprawl. And like L.A., Mexico City lies in a valley of a 15-year sustainability plan he launched aiming to make
surrounded by mountains, so thermal inversions trap pollutants Mexico City “the greenest city in the Americas.” New lines
over the city. Moreover, at Mexico City’s high altitude—2240 m were added to the subway system, and 800 exhaust-spewing 467

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