Understanding the Grades and Tables

A full explanation of the sources of data and methodology is in Methodology.

» Understanding the grades
» Understanding the population tables

Understanding the Grades

  1. Not all counties have monitors for either ozone or particle pollution. If a county does not have a monitor, that county’s name is not on the list in these tables. The decision about monitors in the county is made by the state and the U.S. Environmental Protection Agency, not by the American Lung Association.
  2. INC (Incomplete) indicates that monitoring is underway for that pollutant in that county, but that the data are incomplete for all three years. Those counties are not graded or received an Incomplete.
  3. DNC (Data Not Collected) indicates that data on that particular pollutant is not collected in that county.
  4. The Weighted Average (Wgt. Avg) was derived by adding the three years of individual level data (2008-2010), multiplying the sums of each level by the assigned standard weights (i.e. 1=orange, 1.5=red, 2.0=purple and 2.5=maroon) and calculating the average. Grades are assigned based on the weighted averages as follows: A=0.0, B=0.3-0.9, C=1.0-2.0, D=2.1-3.2, F=3.3+.
  5. 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. Design values for the annual PM2.5 concentrations by county were collected from data previously summarized by the EPA and were downloaded on September 24, 2011 from EPA’s website at http://www.epa.gov/air/airtrends/values.html. The numbers refer to micrograms per cubic meter, or µg/m3.
  6. The annual average National Ambient Air Quality Standard for PM2.5 is 15 µg/m3. Counties with design values of 15 or lower received a grade of “Pass.” Counties with design values of 15.1 or higher received a grade of “Fail.”

Understanding the Population Tables

  1. Total Population is based on 2010 US Census and represents the at-risk populations in counties with ozone or PM2.5 pollution monitors; it does not represent the entire state’s sensitive populations.
  2. Those 18 & under and 65 & over are vulnerable to ozone and PM2.5. Do not use them as population denominators for disease estimates—that will lead to incorrect estimates.
  3. Pediatric asthma estimates are for those under 18 years of age and represent the estimated number of people who had asthma in 2010 based on the state rates (Behavioral Risk Factor Surveillance System, or BRFSS), applied to county population estimates (U.S. Census).
  4. Adult asthma estimates are for those 18 years and older and represent the estimated number of people who had asthma during 2010 based on state rates (BRFSS) applied to county population estimates (U.S. Census).
  5. Chronic bronchitis estimates are for adults 18 and over who had been diagnosed within 2010 based on national rates (from the National Health Interview Survey, or NHIS) applied to county population estimates (U.S. Census).
  6. Emphysema estimates are for adults 18 and over who have been diagnosed within their lifetime based on national rates in 2010 (NHIS) applied to county population estimates (U.S. Census).
  7. Cardiovascular disease estimates are for adults 18 and over who have been diagnosed within their lifetime, based on national rates in 2010 (NHIS) applied to county population estimates (U.S. Census). CV disease includes coronary heart disease, hypertension, stroke, and heart failure.
  8. Diabetes estimates are for adults 18 and over who have been diagnosed within their lifetime based on state rates (BRFSS) applied to county population estimates (U.S. Census).
  9. Poverty estimates include all ages and come from the U.S. Census Bureau’s Small Area Income and Poverty Estimates program. The estimates are derived from a model using estimates of income or poverty from the Annual Social and Economic Supplement and the Current Population Survey, 2010.
  10. Adding across rows does not produce valid estimates. Adding emphysema and chronic bronchitis will double-count people with both diseases.

FACT: Big polluters and some members of Congress are trying to change the Clean Air Act and dismantle 40 years’ of progress. The Lung Association is fighting to keep the law strong to continue to protect public health.

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