Poor air quality hurts the performance of women marathoners, while male runners are relatively unaffected, according to research from scientists at Virginia Polytechnic Institute.

“If women are running in polluted conditions, their times are going to be slower,” said Linsey Marr, a civil and environmental engineer at Virginia Tech. “You’re not going to PR [achieve a personal record] on a highly polluted day.”

Marr and her collaborator, Matthew Ely, an exercise physiologist at the U.S. Army Research Institute of Environmental Medicine, evaluated marathon race results, weather data, and air pollutant concentrations at seven marathons during a period of eight to 28 years. They compared the top three male and female finishing times with course records and air pollution levels retrieved from the Environmental Protection Agency’s data base, and adjusted for high temperatures, which also have a negative impact on performance.

They found that even though pollution levels rarely exceeded national health standards for air quality during these marathons, women’s performances still suffered. While higher levels of air particles prompted slower running times for women, men were not significantly affected, Marr said.

The performance differences may be due to the smaller size of women’s tracheas, which makes it easier for particles to collect and cause irritation. “Women have smaller windpipes than men,” Marr said. “You get more particles depositing in that area by a factor of two.”

Initially, researchers expected that the problems would be caused by exposure to carbon monoxide, which displaces oxygen in the blood’s hemoglobin, and ozone, a well-established respiratory irritant that can narrow airways. “But we didn’t see it with either,” she said.
Rather, the culprits turned out to be particles, such as soot, windblown dust and diesel exhaust, among other things, she said.

“Previous research has shown that during a race, marathon runners inhale and exhale about the same volume of air as a sedentary person would over the course of two full days,” Marr said. “Therefore, runners are exposed to much greater amounts of pollutants than under typical breathing conditions.”

The researchers conducted their studies at popular U.S. major marathons, including New York, Boston, Chicago, Twin Cities (Minneapolis/St. Paul), Grandma’s (Duluth, Minn.), California International Marathon (Sacramento) and Los Angeles.

The idea for this study arose after male world marathon record holder Haile Gebrselassie of Ethiopia announced he would forego the 2008 Beijing Olympics because he feared that air quality in the Chinese city would endanger his health if he competed there. “After that, we began to wonder what effect air pollution would have on running,” Marr said.

There is not much women runners can do to avoid the effects of air pollution, other than to train when air pollution is low and, as Gebrselassie did, shun marathons in cities known to have poor air quality.

“Of course, you can never predict what the conditions will be on the day of a race,” said Marr, who herself has completed five marathons and one full Ironman (Canada). “The temperature can be high and the air can be bad, but if you’ve spent three to six months training, you’re still going to do it.”

Marr is a member of the national Center for Environmental Implications of Nanotechnology, which is funded by the National Science Foundation (NSF). The center is studying the relationship between a vast array of nanomaterials and their potential consequences on the environment. She is also a past recipient of NSF’s Faculty Early Career Development Program Award, which supported her work with air pollution, in particular how to measure air pollutant emissions.

The study was published in the official journal of the American College of Sports Medicine, Medicine and Science in Sports & Exercise.