Introduction

Each year, the American Lung Association assesses the toll that air pollution places on our nation's ability to breathe. This year's look at county-level air quality expands by more than two times the information provided in previous reports. The American Lung Association State of the Air: 2004 for the first time examines an additional pollutant, PM2.5 or particle pollution¹, in two new measures: the short-term exposure, which are occasional spikes in particle pollution from relatively infrequent events (although these spikes may last hours to days); and the year-round or chronic exposure from particles produced routinely in the environment. In addition, the report examines the latest qualityassured data on ozone for each county that has an ozone monitor, as it has for five years.

Particle pollution has emerged as a widespread problem, especially in large parts of the eastern United States and California. This report looks first at the presence of particle pollution by U.S. Environmental Protection Agency (EPA) region in the next chapter, Regional Analyses. This report also includes tables with each state's short-term and year-round particle grades for each county with a particle monitor. These data come from a network of monitors in over 700 counties established in 1998 and 1999 following EPA's adoption of a new health standard to address particle pollution in 1997. This is the first such analysis of the three years of complete data from those monitors.

Ozone continues to be the most pervasive air pollutant, and remains a present danger despite decreases in levels of this pollutant across the nation since 1980. During the 1990s, ozone concentrations remained remarkably and uncomfortably unchanged.2 EPA's own records show this stagnation. However, EPA's data are now showing a slight trend toward lower ozone readings, a trend also reflected by the analysis in this report. This slight decline also comes in the face of a particularly hot summer in 2002 when many cities reported "Code Red" days, when air pollution levels reached unhealthful levels for all populations. EPA speculates that these declines may be coming from controls put in place to clean up coalfired power plants in the eastern United States.3 If so, this trend will likely persist in future reports, as work is expected to continue in this period as additional control measures are installed on plants through May 2004.