Since 1980, peak smog levels have declined by 70 percent.

This would certainly put a dent in smog levels and reduce our reliance on foreign oil.

At certain times during the summer, agency meteorologists will issue a smog watch for 48 hours when there are elevated smog levels.

High smog levels in the capital city mean that office blocks require no window tinting, a result of heavy amounts of air pollution.

Traffic began to swell, quickly surpassing its earlier fearful proportions - pushing up smog levels with it.

Congress ordered New Jersey and neighboring states in 1990 to reduce smog levels 15 percent by this year.

"It will be extremely difficult to significantly reduce smog levels in the future without this type of innovative approach," the official said.

The valley has more days when smog levels exceed federal standards than anywhere else in the country.

When smog levels are high the sky looks yellowish grey because nitrogen oxides are yellow.

More than 100 major cities now exceed the maximum permissible smog levels at some point during the year.