Just because air quality isn’t on your mind doesn’t mean it isn’t affecting your brain—or the way your favorite Major League Baseball team’s games are called.

New research by James Archsmith, assistant professor of agricultural and resource economics, takes a unique approach to the question of how air quality alters cognition, revealing that small increases in certain pollutants lead to significantly worse calls. Although based on the national pastime, the results aren’t a game, and carry major implications for federal air quality standards and policies, as well as industry and workplace standards.

For the paper published in the Journal of the Association of Environmental and Resource Economists, Archsmith analyzed air quality data at Major League Baseball stadiums and compared it to the quality of umpires’ calls. Although plenty of data show how air quality harms the health of workers in labor-intensive jobs like agriculture, Archsmith and collaborators Anthony Heyes, a University of Ottawa professor, and Soodeh Saberian, a professor at the University of Manitoba, had been looking for a way to measure air quality’s effect on cognition in mentally taxing jobs.

“I can’t remember exactly how I made the connection, but I remember sitting with my colleague and saying, ‘What about major league umpires?’” said Archsmith.

They quickly realized they’d hit the idea out of the park. Accurate measurement is a primary challenge for researchers, and measuring subtle changes in performance for mentally-taxing jobs—like that of a lawyer, for instance—is doubly difficult, Archsmith said.

But modern pitch tracking technology allows for a straightforward measure of the quality of the calls umpires are making, and that can be compared to publicly available EPA air quality data.

“Almost all baseball stadiums across the country have federal air pollution monitoring occurring very close to the stadium,” Archsmith explained, giving this approach another edge.

There’s another reason major-league umps also make great study subjects: their constant travel.

“Previous studies look at one particular place, which means there isn’t much variation in the pollution profile, most of which is coming from automobiles,” explains Archsmith. “Since umpires travel across the country, we can look at the same umpires making calls in a lot of different locations—you need the geographic variation.”

In order to make a connection to cognition and a particular type of pollution, variation in air quality exposure is necessary. Because of this, Archsmith and his collaborators were able to see that carbon monoxide and fine particulates in the air reduce umpires’ ability to get calls right, while ozone and nitrogen oxides, by contrast, didn’t seem to have an effect.

Carbon monoxide exposure—one of smoking’s major effects—depletes the body of oxygen and restricts blood flow to the heart and brain.

Although it may provide yet another kind of data for baseball analytics enthusiasts to chew on, the findings should be eye-opening far beyond the world of sports fans, Archsmith said.