Park officials were reviewing the new study but had not evaluated whether ozone and visitation are linked, spokesman Jeffrey Olson said. He said nine parks issue ozone alerts when warranted _ Acadia, Great Smoky Mountains, Mammoth Cave, Pinnacles, Rocky Mountain, Sequoia, Kings Canyon, Shenandoah and Yosemite.
Virginia Tech economist Kevin Boyle, who has researched ozone in parks and was a peer reviewer for the study, said it provides “strong, suggestive evidence” that air pollution is changing people’s behavior when planning a park visit. Boyle said follow-up research is needed to confirm the findings.
Tourists also cut visits short for other air quality problems, such as thick smoke from wildfires that was blanketing Yosemite National Park this week and led to health warnings.
Ozone concentrations nationwide have generally fallen since the Clean Air Act was amended in 1990 to address the problem, according to the U.S. Environmental Protection Agency.
Yet amounts still regularly exceed national guidelines, and the researchers determined that many national parks have pollution levels similar to New York or Los Angeles.
A comparison of ozone in parks to levels in the 20 most populous U.S. cities showed they were “statistically indistinguishable,” according to the study.
At Sequoia National Park, about 200 miles (322 kilometers) north of Los Angeles, there have been more bad ozone days than in the city in all but two years since 1996, the study said.
Park visitors who live nearby are more likely to change their plans than out-of-town visitors who have sunk money into airplane tickets, lodging and rental cars, said John Loomis, an economics professor at Colorado State University who was not involved in the study.
Studies of air quality alerts and the reactions they trigger among schoolchildren in England and children and the elderly in Los Angeles have reached similar conclusions.
“You basically shift what you do” to avoid pollution, Loomis said.