Ozone Can Trigger Respiratory Problems.

• Position: Brief Article

The hot days of late summer provide the perfect climate for formation of ground-level ozone and can cause short-term difficulties for the respiratory system, warns David Khan, assistant professor of internal medicine and an allergist at the University of Texas Southwestern Medical Center at Dallas. Ground-level ozone is created when pollutants emitted by cars and chemical plants react to heat and sunlight.

"When there is an ozone alert, everyone needs to be conscious of the time they spend outdoors," he notes. "High ozone levels make a person with allergies or...