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, data on pollution will not show up in these tables. The decision about placing 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 (2011-2013), 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. The numbers refer to micrograms per cubic meter, or µg/m3. Design values for the annual PM2.5 concentrations by county for the period 2011-2013 are as posted on August 28, 2014 at EPA's website at http://www.epa.gov/air/airtrends/values.html. The 2011-2013 design values were compared to the 2012 National Ambient Air Quality Standard for Annual PM2.5, particularly to the EPA’s assessment of data quality required, as discussed on EPA's website at http://www.epa.gov/pmdesignations/2012standards/regs.htm. Many design values are missing because state data did not meet quality requirements.
  6. The annual average National Ambient Air Quality Standard for PM2.5 is 12 µg/m3 as of December 14, 2012. Counties with design values of 12 or lower received a grade of "Pass." Counties with design values of 12.1 or higher received a grade of "Fail."

Understanding the Population Tables

  1. Total Population is based on 2013 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 2013 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 2013 based on state rates (BRFSS) applied to county population estimates (U.S. Census).
  5. COPD estimates are for adults 18 and over who had ever been diagnosed with chronic obstructive pulmonary disease, which includes chronic bronchitis and emphysema, based on state rates (BRFSS) applied to county population estimates (U.S. Census).
  6. Cardiovascular disease 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). CV disease includes coronary heart disease, hypertension, stroke, and heart attack.
  7. 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).
  8. 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, 2013.
  9. Adding across rows does not produce valid estimates. Adding emphysema and chronic bronchitis will double-count people with both diseases.
Did You Know?

Did You Know?Cleaner air may add 4 months on to the average person's life, according to one study.

Help us Fight For Air!  |  See more facts »