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Report: California Cities Top List of Most-Polluted Regions in U.S.

Most of the nation's cities with the highest air pollution rates are located in California, according to a report from the American Lung Association, the San Francisco Chronicle reports.

The report notes that recent studies have found that ozone and particle pollution have a more significant effect on residents' health than previously believed.

Report Details

For the 13th annual report, ALA used data that the Environmental Protection Agency obtained at various official monitoring sites from 2008 to 2010 to analyze levels of ozone -- commonly referred to as "smog" -- and particle pollution -- often referred to as "soot" or "ash" (Fimrite, San Francisco Chronicle, 4/30).

Overall Findings

Despite major improvements in U.S. air quality, researchers found that about 127.2 million U.S. residents, or 41%, live in counties where the level of ozone, short-term particles or year-round particles was unhealthful. It also found that 5.7 million residents live in a county were all three pollution levels were unhealthy.

The report notes that many of the most-polluted cities in the U.S. have significantly reduced air pollution levels in recent years. For example, Los Angeles reported the lowest level of smog in the report's 13-year history (ALA release, 4/25).

California Cities Top List of Most-Polluted Regions

ALA's annual report has regularly found California to have the most-polluted air quality in the U.S., mainly because the warm, dry climate tends to trap smog.

According to the latest report, nine of the 10 most ozone-polluted cities in the U.S. are located in California. The top five most ozone-polluted regions are:

  • Los Angeles-Long Beach-Riverside;
  • Visalia-Porterville;
  • Bakersfield-Delano;
  • Fresno-Madera; and
  • Hanford-Corcoran (San Francisco Chronicle, 4/30).

Meanwhile, the top five cities most polluted by short-term particle pollution are:

  • Bakersfield-Delano;
  • Fresno-Madera;
  • Hanford-Corcoran;
  • Los Angeles-Long Beach-Riverside; and
  • Modesto.

The top five cities most polluted by long-term particle pollution are:

  • Bakersfield-Delano;
  • Hanford-Corcoran;
  • Los Angeles-Long Beach-Riverside;
  • Visalia-Porterville; and
  • Fresno-Madera (ALA release, 4/25).
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