US Air Quality Gradebook

Emission Gradesheets

Autumn Leaves for US Air Quality Gradebook - Emission Gradesheets


The emission gradesheets, which are accessible through hyperlinks below, consider county-by-county air emission densities, in tons per square mile per year, of the following pollutants: carbon monoxide (CO), lead and lead compounds (Pb), nitrogen oxides (NOx), volatile organic compounds (VOC), particulate matter less than or equal to 10 micrometers (PM10), particulate matter less than or equal to 2.5 micrometers (PM2.5), ammonia (NH3), sulfur dioxide (SO2), total hazardous air pollutants (HAP), and two particular HAP’s, namely diesel emissions and acrolein emissions.  For the first eight pollutants except lead and its compounds, (CO through SO2, except Pb), emissions are based on 1999 data from the EPA National Emissions Inventory at, and in particular at More recent data can be found at


Lead, acrolein, diesel emissions, and hazardous air pollutants are 1996 data: see

For more recent data see, and in particular For a discussion of hazardous air pollutants see, and for a list of them see Diesel emissions top the list of air pollutants adding to cancer risk.  Acrolein (CH2CHCHO, pronounced a-kro’-lee-in, “acrid+olein”) is the dominant air pollutant for noncancer hazard.  It is an air pollutant produced by forest and wildfires, open burns, structure fires, and as a combustion product of gasoline, diesel, and jet engines.  One can find related consideration of these pollutants at online reference, and specifically at  Scorecard ranks counties by total tons per county, rather than considering tons per square mile of a county’s total jurisdictional land and water area as here.


For each US county, assign grade levels to emission densities, in tons per square mile per year, according to the following table:



Grade Levels



The grade "A" represents the Best/Cleanest emission densities in the US, and "F" the Worst/Dirtiest in the US.  The grades reflect the statistical distribution

of base-10 logarithms of the measured emission densities for all US counties, as in the following tables:



Bell Curve - Non-Lead



Bell Curve - Lead



The shift of the bell curve by one standard deviation for lead reflects a cleaner national average for this pollutant.  The statistical procedure makes each grade limit a common multiple of the next lower limit.  For example, the upper grade A limit for VOC before "rounding up" is 0.505 tons per square mile per year, and the common multipler for the VOC distribution is 3.87
= 10(one standard deviation).

The unrounded upper limit for
grade B is 0.505 x 3.87=1.954,
grade C is 1.954 x 3.87=7.56, and
grade D is 7.56 x 3.87=29.3.


When applied individually to the 11 emissions, the procedure results in the following percentages of measured counties in the grade levels:




[N = Number of US counties with emissions data for the pollutant.  Example: Grade D for CO means at least 72.2% of 3143 US counties have smaller CO emission densities (72.2% = 6.7% A's + 21.4% B's + 44.1% C's).]



The hyperlinks below bring up sheets showing grades for each type of emission, the overall ambient grade, and the resultant county grades.  There are two county grades, "self" for the county as determined by its own emission and ambient grades, and "map" for the county as affected by neighboring counties.  (See "Maps" for more discussion on map grades.)  One can use the grade sheets to determine which individual grades caused a county to be at the level it is.  These are highlighted in bold

italics.  If the cause is a neighboring county, the "map" grade is highlighted.  If the cause is ambient monitoring, one can further look in "Ambient Grade Sheets" to determine the specific pollutant measurement that determined the county's ambient grade.


Click on a state, county-range combination to bring up that grade sheet.  After viewing, click the browser's back button/arrow to return to this index page.



Alabama, Autauga-Monroe    Montgomery-Winston

Alaska (emissions all 1999)

American Samoa


Arkansas, Arkansas-Nevada    Newton-Yell

California, Alameda-Stanislaus    Sutter-Yuba

Colorado, Adams-Prowers    Pueblo-Yuma



District of Columbia

Florida, Alachua-Palm Beach    Pasco-Washington

Georgia, Appling-Echols    Effingham-Miller    Mitchell-Washington

Georgia, Wayne-Worth




Illinois, Adams-Lake    Lawrence-Williamson    Winnebago-Woodford

Indiana, Adams-Marshall    Martin-Whitley

Iowa, Adair-Jasper    Jefferson-Wright

Kansas, Allen-Labette    Lane-Wallace    Washington-Wyandotte

Kentucky, Adair-Hart    Henderson-Pulaski    Robertson-Woodford

Louisiana, Acadia-St. Martin    St. Mary-Winn




Michigan, Alcona-Macomb    Manistee-Wexford

Minnesota, Aitkin-Mower    Murray-Yellow Medicine

Mississippi, Adams-Neshoba    Newton-Yazoo

Missouri, Adair-Jefferson    Johnson-St. Francois    St. Louis-Wright

Montana, Beaverhead-Teton    Toole-Yellowstone

Nebraska, Adams-Kearney    Keith-York


New Hampshire

New Jersey

New Mexico

New York, Albany-St. Lawrence    Steuben-Yates

North Carolina, Alamance-Jackson    Johnston-Yancey

North Dakota, Adams-Walsh    Ward-Williams

Northern Mariana Islands

Ohio, Adams-Mahoning    Marion-Wyandot

Oklahoma, Adair-Murray    Muskogee-Woodward


Pennsylvania, Adams-Perry    Philadelphia-York

Puerto Rico, Adjuntas-Mayaguez    Moca-Yauco

Rhode Island

South Carolina

South Dakota, Aurora-Moody    Pennington-Ziebach

Tennessee, Anderson-Lawrence    Lewis-Wilson

Texas, Anderson-Coryell    Cottle-Hardin    Harris-Llano

Texas, Loving-Runnels    Rusk-Wood    Yoakum-Zavala



Virgin Islands

Virginia, Accomack-Galax (City)    Giles-Powhatan    Prince Edward-York


West Virginia, Barbour-Wayne    Webster-Wyoming

Wisconsin, Adams-Portage    Price-Wood




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