Here's my view on it.
I try to stay out of the ozone. The best way is to become familiar with the smog patterns, for example:
1) Windless days can be worse for smog.
2) The later it gets (in the summer) past 4:00, the worse it gets for smog.
3) If it rains, ozone drops to almost nothing.
4) These are all generalizations. In Georgia, call the Environmental Protection Division's air pollution standard reporting system at (404) 362-4909 for an hourly report for your city.
Today, Friday, June 7, is not a smog alert day. At 3:00 today, the estimated air quality index for Atlanta was 48, considered, "Good." 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," 151-200 is "Unhealthy," etc.
Unless the smog is already high in the morning (not having cleared adequately from the previous day,) there is a good chance that I can make it home before 6:00 when the smog levels frequently begin to be "Unhealthy for Sensitive Groups," or "Unhealthy." But I've seen smog levels higher than 250! I don't even let my 6 year-old daughter outside at these times.
The smog levels often become troublesome after 6:00 pm and continue to rise until the peak sometime around 10:00 pm. They level off and then fall back to "Good" levels by early morning, before most of us ever wake up.
No, I am very concerned about riding in high ozone levels and will not ride in it: I avoid it like the plague. I have had "lung burn" many times in the past, before I knew about ozone. Now, I watch the smog levels religiously in the summer (and I rant obsessively about the evils of gasoline-powered vehicles.)