The American Lung Association (ALA) recently released its annual State of the Air report for 2008, which ranks cities and counties based on their levels of air pollution. The following is a list of the worst cities for air pollution based on the 24-hour PM2.5 concentration. This measure is the maximum daily value of the concentration of particles in the air that are less than 2.5 micrometers in size (PM2.5), which are thought to be the most harmful to human health. The ALA used the Environmental Protection Agency’s database to obtain the data and ranked cities based on the number of days that the 24-hour PM2.5 was rated in the categories unhealthy for sensitive groups, unhealthy, very unhealthy, or hazardous. The list below represents the cities (and surrounding areas) with the worst 24-hour PM2.5 measures over the years 2004-2006 followed in parentheses by the total population that inhabits each area. Note that cities both small and large make the list.

The top 10 most polluted cities in the U.S. are:

1. Pittsburgh-New Castle, PA (2,462,571)
2. Los Angeles-Long Beach-Riverside, CA (17,775,984)
3. Fresno-Madera, CA (1,038,101)
4. Bakersfield, CA (780,117)
5. Birmingham-Hoover-Cullman, AL (1,180,206)
6. Logan, UT-ID (111,156)
7. Salt Lake City-Ogden-Clearfield, UT (1,632,814)
8. Sacramento-Arden-Arcade-Yuba City, CA-NV (2,373,596)
9. Detroit-Warren-Flint, MI (5,410,014)
10. Washington-Baltimore-Northern Virginia, DC-MD-VA (8,211,213)

To find out more about diseases caused by air pollution, join the Healia Health Community for Lung Diseases or the Healia Health Community for Heart Diseases.

Related blog post: Study Finds Cleaner Air Lengthens American Lives by Nearly Five Months

_{Source: American Lung Association, State of the Air 2008, Table 2. http://www.stateoftheair.org/2008/key-findings/SOTA08_Table2.pdf}

_{Photo: saeru, Flickr, Creative Commons}