Why You Don’t Want to Run in Smog

Tell us again,why don’t we want to run in smog? Because, as the L.A. Times reports, exercise exacerbates the unhealthful effects of pollutant-rich air. During exercise, muscles need more oxygen to work,
breathing rates increase by about seven times. When that happens, the lungs take in and expel double to triple the normal amount
of air — dramatically increasing their exposure to pollutants.
The paper reminds those fortunate enough to live in Southern California that the air quality board issues health warnings based on ozone and
pollutant levels; an index of 101 to 150 is unhealthy for sensitive
groups. An index of 151 to 200 is
considered unhealthy, meaning everyone should discontinue prolonged,
vigorous exercise outdoors that lasts more than an hour. And finally, very unhealthy air, with an index of 201 and above, comes with a warning that all  vigorous outdoor activity should be stopped.
Read more in the L.A. Times.