Key Findings

The State of the Air 2010 shows that the air quality in many places has improved, but that over 175 million people—roughly 58 percent—still suffer pollution levels that are too often dangerous to breathe.   Unhealthy air remains a threat to the lives and health of millions of people in the United States, despite great progress. Even as the nation explores the complex challenges of global warming and energy, air pollution lingers as a widespread and dangerous reality.

The State of the Air 2010 report looks at levels of ozone and particle pollution found in monitoring sites across the United States in 2006, 2007, and 2008. The report uses the most current quality-assured nationwide data available for these analyses.

For particle pollution, the report examines fine particulate matter (PM2.5) in two different ways: averaged year-round (annual average) and over short-term levels (24-hour). For both ozone and short-term particle pollution, the analysis uses a weighted average number of days that allows recognition of places with higher levels of pollution. For the year-round particle pollution rankings, the report uses averages calculated and reported by the U.S. Environmental Protection Agency. For comparison, the State of the Air 2009 report covered data from 2005, 2006 and 2007.1

The strongest improvement came in the year-round (annual) particle pollution levels, but most of the cities with the highest ozone and short-term particle levels improved as well. These results show that cleaning up major sources of air pollution produces healthier air.  However, the continuing problem demonstrates that more remains to be done, especially in cleaning up coal-fired power plants and existing diesel engines. The results also show the need for stronger limits on national air pollution levels—a fight that the American Lung Association has long led as a key to healthier air.

For the first time, the State of the Air 2010 includes population estimates for another at-risk group, people living in poverty. As discussed under Health Effects, people who have low incomes face higher risk of harm from air pollution. The population estimates here are based in the poverty definition used by the U.S. Census Bureau.  

1 A complete discussion of the sources of data and the methodology is included in Appendix: Methodology.