Children and the infirm in metro Atlanta are being cautioned to avoid strenuous activity because forecasters expect high levels of ozone.
The Clean Air Campaign says children and people with heart or lung ailments should avoid prolonged outdoor activities Wednesday afternoon and early evening. That's when ozone levels are generally worst.
Smog is a respiratory irritant that has been linked to asthma attacks and other illnesses. It's created when emissions from cars, power and chemical plants, refineries and other factories mix in sunlight and heat.