South of the Border

For the last two years, Russell has modeled air quality in Mexico City, which has the highest ozone levels in North America. His latest effort involved investigating the impact of switching to day-light savings time. The Mexican Petroleum Institute, the research division of the government-run petroleum company, was interested in switching for two reasons: It would reduce energy use because people would turn on their lights later, and it would help align the travel industry with the United States. The unknown quantity, however, was how it would affect ozone production. The government tapped Russell for help. "The environment," says Russell, "is one of the key policy questions in Mexico right now."

Russell and his colleagues found that the switch would create a 5 percent increase in ozone. "What happens, in essence," says Russell, "is you're pushing the morning rush hour up one hour compared to solar noon, so it's allowing the species to react one more hour before the sun starts to go down." Russell presented his results at a government meeting, and shortly after, the Mexican officials nixed the day-light savings plan.

Russell and his colleagues plan further studies of Mexico City air quality. With new data, they will increase the number of chemical species included in their model, and they will model production of particulate emissions. The small particles that help create the hazy gray cloud over a city on a hot day are increasingly recognized as a health factor in lung disease. "Mexico is making a serious commitment to improve their smog problem," says Russell. "Imagine what would happen in the United States if a city prohibited driving personal vehicles one day a week, which is what they've done in Mexico City. They're looking for real answers and trying to progress as much as they can."

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