I found a link that interested me in ScienceDaily: https://www.sciencedaily.com/release...0718143112.htm
This is from Iowa State University. You may have seen something about this on the major media. Well worth the read. I then found a related article in Scientific American that does a bit more than simple reporting but does not cross the line into the fake news realm: https://www.scientificamerican.com/a...d-your-breath/
Note:
I know that car fumes are not ozone, but even in the mid 1960's the air quality in Yellowstone was very poor. Too many cars were simply following the loops. The families then bundle out to view the geyser mud pot or what ever the attraction at the next parking lot was. I was not impressed until I went off road and camped far from the loops. The air was better, but only marginally. The down wind problem noted in the articles still is a problem with even combustion fumes. Now as I said, car combustion is not ozone, but it is still nasty stuff when walking down a big city street or if you are stuck in traffic like in the Yellowstone loops. People are oblivious to the damage we do in the name of tourism. They are locked into an air-conditioned vehicle with their only contact with nature being the occasional bear looking in the window for food.Other researchers are unsure of the connection between ozone warnings and park visitation. “Correlation is not causation,” says Joel Burley, an air pollution scientist at Saint Mary’s College of California who was not involved in the study. He notes the researchers did not pinpoint why people decided whether to visit a park. He is skeptical that travelers who, for example, reserve campsites in Yosemite National Park months in advance would abandon plans to visit so easily. “How many visitors are actually changing their behavior after checking air quality?” he asks. “It’s a fascinating study,” he adds, but the next step should be to determine whether air quality alerts really impact park visitation decisions. “They didn’t measure that,” he says.
I still think the study is interesting, but I suggest you read the SA article as well.