Measurements from the Virginia Department of Environmental Quality show the Richmond area has been the smoggiest region of the state this year.

According to the figures, ozone has hit unhealthy levels on 16 days so far this spring and summer, compared with 11 days in northern Virginia.

The main pollutant in smog hit the unsafe mark on seven days in the Hampton Roads area.

The numbers are derived from an ozone limit issued this spring by the federal government. The new limit is tougher, which means more days violate the standard.

Spokesman Bill Hayden says ozone continues to be worse in northern Virginia, which has been out of compliance with federal clean-air requirements for nearly 20 years.

High levels of ozone can damage the lungs and aggravate breathing problems such as asthma.