Appendix A: Description of Methodology

Statistical Methodology: The Air Quality Data
Data Sources
The data on air quality throughout the United States were obtained from the U.S. Environmental Protection Agency’s Air Quality System (AQS), formerly called Aerometric Information Retrieval System (AIRS) database. The American Lung Association contracted with Dr. Allen S. Lefohn, A.S.L. & Associates, Helena, Montana, to characterize the hourly averaged ozone concentration information and the 24-hour averaged PM_2.5 concentration information for the three-year period for 2003-2005 for each monitoring site.

Design values for the annual PM_2.5 concentrations by county were collected from data previously summarized by EPA and were used as received from EPA on October 30, 2006 in personal correspondence from Mr. Mark Schmidt, EPA.

Ozone Data Analysis
The 2003, 2004, and 2005 AQS hourly ozone data were used to calculate the daily eight-hour maximum concentration for each ozone-monitoring site. The data were considered for a three-year period for the same reason that EPA uses three years of data to determine compliance with the ozone standard to prevent a situation in any single year where anomalies of weather or other factors can create air pollution levels that inaccurately reflect the normal conditions. The highest eight-hour daily maximum concentration in each county for 2003, 2004, and 2005, based on the EPA-defined ozone season, was identified.

Using these results, A.S.L. & Associates prepared a table by county that summarized, for each of the three years, the number of days the ozone level was within the ranges identified by EPA based on the EPA Air Quality Index:

No data capture criteria were used to eliminate monitoring sites. All data within the ozone season were used in the analysis because the goal was to identify the number of days that eight-hour daily maximum concentrations occurred within the defined ranges.

Following receipt of the above information, the American Lung Association identified the number of days that each county, with at least one ozone monitor, experienced air quality designated as orange, red, or purple.

Short-term Particle Pollution Data Analysis
A.S.L. & Associates identified the maximum daily 24-hour AQS PM_2.5 concentration for each county in 2003, 2004, and 2005 with monitoring information. Using these results, A.S.L. & Associates prepared a table by county that summarized, for each of the three years, the number of days the maximum of the daily PM_2.5 concentration was within the ranges identified by EPA based on the EPA Air Quality Index, adjusted by the American Lung Association as discussed below:

from 0.0 µg/m3 to 15.4 µg/m3	Good (Green)
from 15.5 µg/m3 to 35.0 µg/m3	Moderate (Yellow)
from 35.1 µg/m3 to 65.4 µg/m3	Unhealthy for Sensitive Groups (Orange)
from 65.5 µg/m3 to 150.4 µg/m3	Unhealthy (Red)
from 150.5 µg/m3 to 250.4 µg/m3	Very Unhealthy (Purple)
greater than or equal to 250.5 µg/m3	Hazardous (Maroon)

On September 21, 2006, the EPA announced a revised 24-hour National Ambient Air Quality Standard for PM_2.5, changing the standard from 65 µg/m³ to 35 µg/m³. The EPA has not yet announced changes to the Air Quality Index based on the new standard. However, the Lung Association adjusted the level of the category “Unhealthy for Sensitive Groups” to include the new standard, making that category range from 35.1 µg/m³ to 65.4 µg/m³.

No data capture criteria were used to eliminate monitoring sites. All data were used in the analysis because the goal was to identify the number of days that the maximum in each county of the daily AIRS PM_2.5 concentration occurred within the defined ranges. Only 24-hour averaged PM data were used. Included in the analysis are data collected using only FRM and FEM methods, which reported 24-hour averaged data. As instructed by the Lung Association, A.S.L. & Associates included the exceptional and natural events that were identified in the AQS database and identified for the Lung Association the dates and monitoring sites that experienced such events.

Following receipt of the above information, the American Lung Association identified the number of days that each county, with at least one PM_2.5 monitor, experienced air quality designated as orange, red, purple or maroon.

Description of County Grading System.
Ozone and short-term particle pollution (24-hour PM2.5)
The grades for ozone and short-term particle pollution (24-hour PM_2.5) were based on a weighted average for each county calculated using the Air Quality Index (adjusted to accommodate the 2006 changes in the National Ambient Air Quality Standard for PM_2.5) as noted above. The number of unhealthful days experienced by each county was assigned a factor for weighting purposes: each orange day, a factor of 1; each red day, 1.5; each purple day, 2; and each maroon day, 2.5. By multiplying the total number of days within each category by its assigned factor, a total was determined. Because the monitoring data were 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. In 2003 and again in 2005, the U.S. Census Bureau published revised definitions for the nation’s Metropolitan Statistical Areas. Therefore, comparisons between MSAs of the State of the Air reports from 2000 to 2003 and the State of the Air reports in 2004 and later should be made with caution.

All counties with a weighted average of zero 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” had only 3 to 6 days over the standard, including at most one red day, and 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 had 7 to 9 days over the standard. Counties with weighted averages of 3.3 or higher (corresponding to approximately the eight-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. The number of days for an “F” grade was set to roughly correlate with the number of days that would place a county in nonattainment for the ozone standard. For short-term particle pollution, the number of days required for an “F” would roughly approximate a 99th percentile form of the PM_2.5, a form the American Lung Association supports.

Grading System
Grade	Weighted Average	Approximate Number of Allowable Orange/Red/Purple/Maroon days and Example Combinations
A	0.0	None
B	0.3 to 0.9	1 to 2 orange days with no red/purple/maroon
C	1.0 to 2.0	3 to 6 days in unhealthy ranges: 3 to 5 orange with no more than 1 red or 6 orange with no red/purple/maroon
D	2.1 to 3.2	7 to 9 days in unhealthy ranges: 7 total (including up to 2 red) to 9 orange with no red/purple/maroon
F	3.3 or higher	9 days or more in unhealthy ranges: 10 orange days or 9 total including at least 1 or more red/purple/maroon

Weighted averages allow comparisons to be drawn based on severity of air pollution. For example, if one county had nine orange days and 0 red days, it would earn a weighted average of 3.0 and a D grade. However, another county that had only eight orange days but also had two red days, which signify days with more serious air pollution, would receive an F. That second county would have a weighted average of 3.7.

Note that this system differs significantly from the methodology that the EPA uses to determine violations of both the ozone standard and the 24-hour PM_2.5. EPA determines whether a county violates the standard based on the fourth maximum daily eight-hour ozone reading each year averaged over three years. Multiple days of unhealthy air beyond the highest four in each year are not considered. In contrast, the system used in this report recognizes when a community’s air quality repeatedly results in unhealthy air throughout the three years. Consequently, some counties will receive grades of “F” in this report showing repeated instances of unhealthy air, while still meeting EPA’s 1997 ozone standard or the one-hour ozone standard set in 1979.

Year-round particle pollution (Annual PM_2.5)
Since no comparable Air Quality Index exists for year-round particle pollution (annual PM_2.5), the grading was based on EPA’s determination of violations of the national ambient air quality standard for annual PM_2.5 of 15 µg/m³, as reported October 30, 2006 in personal correspondence from Mark Schmidt, EPA. Counties that EPA listed as being in attainment of the standard were given grades of “Pass.” Counties EPA listed as being in nonattainment were given grades of “Fail.” Where insufficient data existed for EPA to determine attainment or nonattainment, those counties received a grade of “Incomplete.” Counties were ranked by design value. Metropolitan areas were ranked by the design value among the counties in the defined Metropolitan Statistical Area as of 2005. The Design Value is the calculated concentration of a pollutant based on the form of the national ambient air quality standard, and is used by EPA to determine whether the air quality in a county meets the standard.

The Lung Association received critical assistance from members of the National Association of Clean Air Agencies, formerly known as the State and Territorial Air Pollution Control Administrators, and the Association of Local Air Pollution Control Administrators. With their assistance, all state and local agencies were provided the opportunity to review and comment on the data in draft tabular form. The Lung Association reviewed all discrepancies with the agencies and, if needed, with A.S.L. & Associates. Questions about the annual PM design values were referred to Mr. Schmidt of EPA, who reviewed and had final decision on those  determinations. The American Lung Association wishes to express its continued appreciation to the state and local air directors for their willingness to assist in ensuring that the characterized data used in this report are correct.