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Luisa, Mario Molina battle air pollution in Mexico City

An international team led by an MIT research scientist and her husband, an MIT Nobel laureate, is working to help Mexican policy-makers find ways to reduce Mexico City's severe and persistent air pollution. The researchers, who have been working on the project for more than three years, will be traveling back to Mexico in late March to spend another five weeks using a novel mobile laboratory to collect field data.

The project is the initial focus of the Integrated Program on Urban, Regional and Global Air Pollution, directed by Dr. Luisa T. Molina of the Department of Earth, Atmospheric and Planetary Sciences and Institute Professor and Nobel laureate Mario Molina. It includes investigators from across MIT, the Harvard School of Public Health and other U.S. and international institutions. More than a dozen institutions and government agencies in Mexico are involved.

The goal of the program is to perform "integrated assessments" of different emissions-reduction strategies, considering not only scientific and technological factors but also the broader social, economic and political dimensions of the problem and possible actions that could be taken.

Without data, it's impossible to predict how various emission-reduction strategies might actually improve air quality. The Mexico City metropolitan area has been the subject of air quality studies, including widespread air-pollution monitoring and "emissions inventories" (lists of specific sources and their emissions). However, initial computer simulations by the Molinas' team showed that the current emissions inventories did not fully explain the pollution that was measured in the atmosphere.

As a result, the team instituted an intensive field campaign to improve the quality of the available data. Key to the work is the mobile lab--a van carrying highly sophisticated, state-of-the-art instruments to accurately track and map noxious emissions. The lab was provided by Aerodyne Research Inc., a collaborator in the work.

In a two-week campaign last year in Mexico City, the researchers rode in the van while following cars, trucks and buses to analyze their exhaust plumes. To "map" the city's air quality and determine daily variations, they also parked the van at different locations, sometimes for 24 hours or more.

Last summer and fall, they checked human exposures by carrying handheld monitors while riding in commuter buses and delivery trucks. They also left monitors in bus and truck terminals for several days at a time.

Preliminary mobile laboratory findings indicate the potential significance of the new measurements. For example, measurements taken on the grounds of an elementary school showed tremendous photochemical activity; ozone reached high peak concentrations on two consecutive afternoons, even though the weather was not unusually hot or sunny.

The team continues to analyze the resulting data--a process that will take many months and will result in refined air-pollution models and numerous technical publications. In the meantime, the novel design of the program itself can begin to serve as a model for similar programs in other highly polluted cities.

This research is supported by the Comisión Ambiental Metropolitana (via Fideicomiso Ambiental del Valle de México), the MIT Alliance for Global Sustainability, the National Science Foundation and the MIT Laboratory for Energy and the Environment. The team published a book entitled "Air Quality in the Mexico Megacity: An Integrated Assessment" (Kluwer Academic Publishers, 2002), which provides an overview of the current understanding of the air pollution problem and lessons learned from air-quality management programs to date.

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A version of this article appeared in MIT Tech Talk on April 2, 2003.

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