Cleaning Big Cities' Air "Not Rocket Science," Expert Says

October 27, 2005

Hemmed in by mountains on three sides, the basin that houses Mexico City, Mexico, has some the dirtiest air in the world.

Pollutants spewed by power plants and tailpipes have nowhere to go. They stay within the city and compromise the health of thousands of people.

But it doesn't have to be this way, according to Mario Molina, a Nobel laureate in chemistry who is affiliated with the Massachusetts Institute of Technology in Cambridge and the University of California, San Diego.

"Technologies exist now, clean technologies that produce a lot less pollution," he said in a broadcast of the Pulse of the Planet radio program that aired yesterday.

(The National Science Foundation funds the radio program and this related National Geographic News series.)

Molina directs the Integrated Program on Urban, Regional, and Global Air Pollution, a project that seeks to resolve air pollution problems in the world's largest cities. Mexico City, Molina's hometown, is the initial focus.

The project has helped the Mexican government transition the country to unleaded gasoline and to make significant reductions in vehicle and power plant emissions.

Clean Technologies

The high altitude and ample sunlight of Mexico City create an ideal environment for pollutants to accumulate and linger, Molina said.

One major culprit, ground-level ozone, forms due to a sunlight-fueled chemical reaction between nitrogen oxides and volatile organic compounds. Commonly called smog, ground-level ozone causes a host of respiratory ailments, according the U.S. Environmental Protection Agency.

Particulate matter is the term applied to the tiny bits of dust, soot, dirt, smoke, and liquid droplets that accumulate in the air and give smog its color.

Breathing particulate matter also causes respiratory ailments. In addition, it adversely affects the environment by changing the acidity of lakes, streams, and forests.

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