With smoky skies pretty much a thing of the past, you may think that air pollution isn't a concern anymore. But now our biggest air pollution problem is a colorless gas called ozone. Breathing ozone can irritate your respiratory system and aggravate asthma and other diseases.

Ozone forms when certain air pollutants react in sunny, warm weather. Some of these pollutants come from the burning of fuels, like the emissions from cars and trucks. Other pollutants are gases like the vapors from paints, chemicals, and fuels. That smell as you fill up the gas tank - that's the aroma of an ozone-causing pollutant. When this stew bakes in the air on a sunny, hot day, ozone pollution can build to unhealthy levels.

You may be surprised to learn that all of Delaware, New Jersey, and southeastern Pennsylvania, and much of Maryland, don't meet the federal health standard for ozone pollution. And it's not just a city problem. Unhealthy ozone levels occur regularly in suburban and even rural areas.