This year, hundreds of square miles in the western US has been on fire, resulting in terrible air quality which often has exceeded EPA guidelines. Dr Kevin Shilling is a long time ultrarunner, was 10th at the HR100 this year, and is a pulmonary physician based in Salt Lake City. So we ask him an important question:
When does air pollution get so bad it's better not to exercise?
"That depends on how badly you want to go for a run."