Northwestern researchers published Monday the first real-world trial examining the effects of human behavior and gasoline use on air pollution.

The interdisciplinary study reports a 20 percent drop in the ozone levels of Sao Paulo, Brazil, after fuel prices encouraged commuters to switch from ethanol to gasoline. The fuel switch also showed an increase in the concentration of nitric oxide and carbon monoxide.

Chemistry Prof. Franz Geiger and former Kellogg Prof. Alberto Salvo conducted the four-year study, which was published Monday in the journal Nature Geoscience.

“Individuals often don’t realize it, but in the aggregate, you can have a real impact on the environment,” Salvo said in a news release.

Sao Paulo has a strong air monitoring system, moderate weather and the world’s largest fleet of flexible-fuel vehicles, making it the best “natural laboratory” in which to study the impact of consumers on air quality.

Geiger and Salvo plan to begin working with McCormick Prof. Aaron Packman to study how the concentration of air pollutants in Chicago could change depending on future traffic scenarios.

“This work allows us to start thinking about the urban metabolism of Chicago, which is an emerging megacity surrounded by ‘corn country,’” Geiger said in the release. “Ethanol from corn is a particularly intriguing option for future, possibly more competitive, energy markets. It’s an area we need to watch.”

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