About the author: Jeffrey Levy joined EPA in 1993 to help protect the ozone layer. He is the National Web Content Manager.
I've been doing things outdoors most of my life: hiking, rockclimbing, etc. For the past 15 years or so, I've also been playing Ultimate Frisbee, which is sort of like soccer mixed with football and basketball. The upshot is you run. A lot. It's usually a race between my lungs and legs to see which will run out of juice first.
A few years ago, I found out I should be more worried about my lungs, especially since I have mild asthma (I don't wheeze so much as cough). Running a lot can be a real problem when the air quality is bad: a lot of ozone in the air can irritate my lungs and leave me out of breath. Note this is ozone down near the ground; the stuff up in the stratosphere protects us from the sun's ultraviolet rays
We can help you figure out when it's better to stay home with the Air Quality Index. This handy site gives you a color-coded, clickable national map with info for many communities. For example, the AQI is provided for "Northern Virginia," which means the DC suburbs where I live.
Try out the AQI and see if it works for you. If it doesn't, I'm sure the folks running it would like to hear your ideas for improvement.