When I worked for the Texas Air Control Board (state air pollution agency) in the mid 70s the EPA tried to force Texans to change their driving habits to lower ozone emissions to "safe levels".
It took years to convince the EPA that if we stopped all transportation, industry, and moved everyone out of the Houston area the ozone level would still be too high. The ozone was being produced by the pine forests. I have a commercial high volume ozone generator I run a few minutes a day when I am away from home for an extended period. Not only does the house smell fresh but, living in the country, I don't find my home invaded by various critters
