BACKGROUNDER

Data Highlights

• Nearly half (49 percent) of the US population—137,206,767—lives in areas with unhealthy levels of ozone despite modest improvements in air quality monitored between1999-2001.

• Over half—55.5 percent—of monitored counties received an “F” rating. Approximately 22 percent of all U.S. counties have ozone monitors.

• Over five million fewer Americans (5,462,079) lived in counties that received an “F” grade compared with last year’s report, despite the report including data from 14 additional counties.

• Over 7.4 million adults with asthma and two million children suffering from asthma attacks live in counties that received an “F” grade in ozone air pollution. Those totals represent 70 percent of the 10.6 million American adults with asthma and 69 percent of the 2.8 million children suffering from asthma attacks who live in counties with an ozone monitor.

• Over 1.5 million Americans with emphysema live in counties that received an “F” rating in ozone air pollution out of the 2.3 million Americans with emphysema who live in those monitored counties. Nearly 4.7 million Americans with chronic bronchitis live in those counties receiving an “F,” out of the 6.8 million Americans with chronic bronchitis living in counties with monitors.

• Of the nation’s over-65 population who live in monitored counties, 68 percent live in counties that received an “F” rating in ozone air pollution, while 70 percent of children under 14 who live in monitored counties reside in counties with a failing grade.

Analysis Highlights

• Slight improvements reflected in the 2003 report, versus State of the Air: 2002, are most likely due to favorable weather conditions, rather than significant new measures to reduce pollution.

• Ninety-three counties’ ratings improved by at least one grade since last year’s report, while 26 counties received lower grades this year.

• Allentown-Bethlehem-Easton, Pa. and Louisville, Ky. have the dubious distinction as the only newcomers in the top 25 metropolitan areas with the worst ozone pollution this year.

• Seven of the 25 most ozone-polluted counties and 10 of the 25 most ozone-polluted metropolitan areas are in the Southeast (Kentucky, North Carolina, South Carolina, Georgia, Tennessee, Alabama, Mississippi, and Florida).

• In the shuffle among most-polluted locales, six counties were deleted from last year’s list of the 25 most ozone-polluted counties, but all maintained their “F” grades. They include Blount, Tenn., Douglas, Ga., Knox, Tenn., Fayette, Ga., Maricopa, Ariz. and Wake, N.C. Newcomers to the most ozone-polluted counties list are Nevada, Calif., Placer, Calif., Tarrant, Texas, Henry, Ga., Camden, N.J., and Hartford, Md. Of the newcomers, only Camden County, N.J. has ever been on this list before.

• California again leads the charts in counties and metropolitan areas with the most ozone-polluted air. Two locales, however, saw their rankings improve significantly. San Luis Obispo, Calif. jumped from an “F” in 2002 to an “A” this year, and Redding, Calif. was one of only two cities (along with Chattanooga, Tenn.) who jumped off this year’s list of most ozone-polluted cities nationwide. (Both cities maintained their “F” grades even though their rankings among cities declined.)

• In Texas, the Houston-Galveston-Brazoria area ranked as the fifth most-polluted metropolitan area for the fourth year in a row, while Dallas-Fort Worth rose from 16^th in 2002 to 12^th on the same list this year. Both Laredo and Brownsville-Harlingen-San Benito, however, made the list of the 20 metropolitan areas with the least ozone air pollution.

• Urban, rural and suburban areas can all be affected by ozone, regardless of where the ozone is actually formed due to ozone transport—the pollutant’s being carried by winds, which vary from region to region. American Lung Association State of the Air: 2003 also presents new analyses of regional ozone sources and trends, as well as examining ozone transport, according to the 10 regions that EPA uses to group the states. Ozone not only moves into a state from the outside but also moves within the state. For example, some air pollution episodes have been followed hour-by-hour as they move downwind, city by city, within Pennsylvania. In many cases, the highest levels of ozone will show up in suburban areas downwind of larger communities. For example, even though an area like San Francisco County in California may not be experiencing high ozone readings, it may be contributing to poor air quality in outlying areas such as the Sacramento and San Joaquin Valley areas to the east and other parts of the Bay Area to the south.

• Some regions, including the Southeast and Midwest, are notable as sources of transported ozone affecting cities and states within the region and outside it. The Southeast (EPA Region 4) is home to some of the most polluting power plants in the nation and to cities with extremely high driving rates; as a result, this region produces more nitrogen oxide (NO_x) and volatile organic compound (VOC) emissions than any other section of the country. The Midwest (EPA Region 5) is home to eight of the top 20 NO_x-emitting facilities in the nation (1999 data) and produces the second-highest NO_x and VOC emissions nationwide.

Grading System

A weighted average was used to determine the grades for each county. The number of orange days experienced by each county was assigned a factor of 1; red days were assigned a factor of 1.5 and purple days were assigned a factor of 2. By multiplying the total number of days within each category by their assigned factor, a total was determined. Because the monitoring data was collected over a three-year period, the total was divided by three to determine the weighted average. Each county’s grade was determined using the weighted average. Counties were ranked by weighted average. Metropolitan areas were ranked by the highest weighted average among the counties in the Census Bureau-defined Metropolitan Statistical Area.

All counties with a weighted average of zero (corresponding to no exceedences of the 8-hour standard over the three year period) were given a grade of “A.” Counties with a weighted average of 0.3 to 0.9 (corresponding to 1 to 2 orange days) received a “B.” Counties receiving a “C” typically had only 3 to 6 days over the standard, including at most one red day, scored a weighted average of 1.0 to 2.0. Counties received a “D” if they had a weighted average of 2.1 to 3.2, which meant they generally had 7 to 9 days over the standard. Counties with weighted averages of 3.3 or higher (corresponding to approximately the 8-hour standard) received an “F.” These counties generally had at least 10 orange days or 9 days over the standard with at least one or more days in the red or purple category.

Weighted averages allow comparisons to be drawn based on severity of air pollution. For example, Bell County, Ky. received a “D” because it had nine orange days and 0 red days, earning it a weighted average of 3.0. However, Bronx County, N.Y. received an “F” although it only had eight orange days, because it also had two red days, signifying days with more serious air pollution. Bronx County had a weighted average of 3.7.

• State of the Air: 2003 Home