7 U.S. cities with the worst air pollution
Wed, Aug 04, 2010 at 12:20 PM
The American Lung Association's State of the Air 2010 report found that more than half the population of the U.S. lives with dangerous pollution levels. Despite progress in many places, the report found the air in some California cities was more polluted than before. Cities were ranked in three areas: year-round particle pollution, short-term particle pollution and ozone.