Inversion index: 7 of the most polluted cities in Utah

Air quality index: 164. (151-200 is the unhealthy range.)

Population impacted: 526,810 people are at risk in the Provo/Orem area.

On the American Lung Association's list of top short-term particle polluted cities, Provo/Orem was No. 11. The association also graded Provo as having an "F" for 24-hour particle pollution. The association found that many particle pollutants can cause heart attacks.

>> Aerial views of Utah Lake in Utah County on Friday, Mar. 2, 2012.