EPA AirData
Cleanest Air by State
Every state and territory with an EPA air monitor, ranked by the same air formula as the ZIP score tool. Expand a state to see the monitored counties behind its rank.
In plain terms: Hawaii has the cleanest measured air of the 53 states and territories with an EPA air monitor, and California the worst.
1Hawaii3 monitored countiesGood80
- Maui County, HI84
- Honolulu County, HI81
- Hawaii County, HI74
2Puerto Rico8 monitored countiesGood77
- Mayagüez Municipio, PR90
- Caguas Municipio, PR82
- Guayama Municipio, PR82
- Ponce Municipio, PR79
- Bayamón Municipio, PR73
- Fajardo Municipio, PR72
- Guaynabo Municipio, PR72
- Cataño Municipio, PR69
3Virgin Islands1 monitored countyModerate75
- St. John Island, VI75
4Montana23 monitored countiesModerate75
- Rosebud County, MT87
- Teton County, MT87
- Gallatin County, MT87
- Beaverhead County, MT86
- Powell County, MT84
- Lake County, MT84
- Hill County, MT80
- Glacier County, MT78
- Phillips County, MT77
- Fergus County, MT76
- Dawson County, MT76
- Custer County, MT74
- Yellowstone County, MT73
- Roosevelt County, MT73
- Sheridan County, MT73
- Silver Bow County, MT73
- Sanders County, MT73
- Missoula County, MT72
- Richland County, MT71
- Ravalli County, MT71
- Flathead County, MT69
- Lewis and Clark County, MT68
- Lincoln County, MT67
5New Hampshire7 monitored countiesModerate73
- Merrimack County, NH77
- Belknap County, NH75
- Hillsborough County, NH73
- Rockingham County, NH73
- Grafton County, NH73
- Cheshire County, NH72
- Coos County, NH70
6Maine11 monitored countiesModerate73
- York County, ME78
- Knox County, ME78
- Sagadahoc County, ME77
- Hancock County, ME76
- Washington County, ME76
- Androscoggin County, ME73
- Kennebec County, ME73
- Aroostook County, ME72
- Penobscot County, ME71
- Oxford County, ME70
- Cumberland County, ME69
7Vermont4 monitored countiesModerate73
- Windham County, VT76
- Bennington County, VT73
- Chittenden County, VT73
- Rutland County, VT71
8Virginia28 monitored countiesModerate73
- Carroll County, VA92
- Fauquier County, VA78
- Caroline County, VA78
- Prince Edward County, VA78
- Prince William County, VA77
- Stafford County, VA77
- Hanover County, VA77
- Suffolk city, VA77
- Giles County, VA77
- Rockbridge County, VA77
- Wythe County, VA76
- Charles City County, VA75
- Norfolk city, VA74
- Hampton city, VA74
- Lynchburg city, VA74
- Arlington County, VA73
- Henrico County, VA73
- Chesterfield County, VA73
- Richmond city, VA73
- Virginia Beach city, VA73
- Roanoke County, VA73
- Bristol city, VA73
- Rockingham County, VA72
- Albemarle County, VA72
- Loudoun County, VA71
- Fairfax County, VA71
- Frederick County, VA71
- Madison County, VA71
9Wyoming17 monitored countiesModerate73
- Uinta County, WY91
- Washakie County, WY87
- Lincoln County, WY87
- Park County, WY86
- Carbon County, WY84
- Platte County, WY77
- Converse County, WY76
- Johnson County, WY76
- Sheridan County, WY75
- Natrona County, WY73
- Teton County, WY73
- Campbell County, WY69
- Laramie County, WY68
- Fremont County, WY68
- Sweetwater County, WY68
- Sublette County, WY68
- Albany County, WY62
10Massachusetts13 monitored countiesModerate72
- Dukes County, MA78
- Barnstable County, MA77
- Hampshire County, MA73
- Norfolk County, MA73
- Plymouth County, MA73
- Worcester County, MA72
- Middlesex County, MA72
- Essex County, MA72
- Bristol County, MA72
- Berkshire County, MA71
- Franklin County, MA71
- Hampden County, MA70
- Suffolk County, MA70
11Rhode Island3 monitored countiesModerate72
- Kent County, RI77
- Washington County, RI72
- Providence County, RI71
12West Virginia13 monitored countiesModerate72
- Tucker County, WV77
- Greenbrier County, WV76
- Kanawha County, WV73
- Berkeley County, WV73
- Wood County, WV73
- Harrison County, WV73
- Ohio County, WV72
- Brooke County, WV72
- Marion County, WV72
- Cabell County, WV71
- Monongalia County, WV71
- Marshall County, WV69
- Hancock County, WV68
13Florida38 monitored countiesModerate72
- Putnam County, FL79
- Flagler County, FL78
- Liberty County, FL78
- Lake County, FL77
- Polk County, FL77
- Highlands County, FL77
- St. Lucie County, FL77
- Okaloosa County, FL76
- Indian River County, FL76
- Pasco County, FL76
- Alachua County, FL75
- Brevard County, FL75
- Manatee County, FL75
- Volusia County, FL74
- Osceola County, FL74
- Baker County, FL73
- Wakulla County, FL73
- Seminole County, FL73
- Martin County, FL73
- Collier County, FL73
- Citrus County, FL73
- Hamilton County, FL72
- Marion County, FL72
- Bay County, FL72
- Escambia County, FL72
- Palm Beach County, FL72
- Pinellas County, FL72
- Lee County, FL72
- Columbia County, FL71
- Holmes County, FL71
- Santa Rosa County, FL71
- Orange County, FL71
- Broward County, FL71
- Sarasota County, FL71
- Leon County, FL70
- Miami-Dade County, FL70
- Duval County, FL69
- Hillsborough County, FL69
14Idaho19 monitored countiesModerate72
- Custer County, ID85
- Blaine County, ID82
- Franklin County, ID81
- Bonneville County, ID79
- Twin Falls County, ID77
- Butte County, ID75
- Bannock County, ID74
- Latah County, ID72
- Boise County, ID71
- Canyon County, ID71
- Kootenai County, ID71
- Valley County, ID70
- Ada County, ID70
- Lemhi County, ID69
- Nez Perce County, ID69
- Idaho County, ID69
- Shoshone County, ID67
- Bonner County, ID67
- Benewah County, ID67
15Alaska8 monitored countiesModerate72
- Kenai Peninsula Borough, AK92
- Aleutians East Borough, AK90
- North Slope Borough, AK89
- Denali Borough, AK79
- Matanuska-Susitna Borough, AK77
- Juneau City and Borough, AK71
- Anchorage Municipality, AK70
- Fairbanks North Star Borough, AK58
16New Jersey15 monitored countiesModerate71
- Monmouth County, NJ75
- Atlantic County, NJ73
- Middlesex County, NJ72
- Hudson County, NJ71
- Morris County, NJ71
- Ocean County, NJ71
- Gloucester County, NJ71
- Cumberland County, NJ71
- Bergen County, NJ70
- Passaic County, NJ70
- Union County, NJ70
- Warren County, NJ70
- Hunterdon County, NJ70
- Mercer County, NJ69
- Camden County, NJ68
17Maryland16 monitored countiesModerate71
- Charles County, MD76
- Calvert County, MD76
- Carroll County, MD75
- Dorchester County, MD74
- Howard County, MD73
- Montgomery County, MD73
- Garrett County, MD73
- Kent County, MD73
- Prince George's County, MD72
- Anne Arundel County, MD71
- Frederick County, MD71
- Washington County, MD71
- Harford County, MD70
- Cecil County, MD70
- Baltimore County, MD68
- Baltimore city, MD68
18North Carolina34 monitored countiesModerate71
- Martin County, NC80
- Hyde County, NC78
- Macon County, NC78
- Rockingham County, NC77
- Caswell County, NC77
- Person County, NC77
- Lenoir County, NC77
- Carteret County, NC77
- Caldwell County, NC77
- Granville County, NC76
- Avery County, NC76
- Alexander County, NC76
- Lincoln County, NC75
- Union County, NC75
- Graham County, NC75
- Haywood County, NC75
- Montgomery County, NC74
- Edgecombe County, NC74
- Pitt County, NC74
- Northampton County, NC73
- New Hanover County, NC73
- Mitchell County, NC73
- Swain County, NC73
- Rowan County, NC72
- Guilford County, NC72
- Durham County, NC72
- Johnston County, NC72
- Cumberland County, NC72
- Buncombe County, NC72
- Wake County, NC71
- Catawba County, NC71
- Davidson County, NC70
- Forsyth County, NC69
- Mecklenburg County, NC69
19South Carolina13 monitored countiesModerate71
- Berkeley County, SC76
- Darlington County, SC75
- Aiken County, SC75
- Anderson County, SC75
- Horry County, SC73
- Chesterfield County, SC71
- Florence County, SC71
- Charleston County, SC71
- York County, SC71
- Richland County, SC70
- Edgefield County, SC70
- Spartanburg County, SC69
- Greenville County, SC68
20Alabama15 monitored countiesModerate71
- Elmore County, AL77
- Shelby County, AL76
- Lawrence County, AL76
- Clay County, AL73
- Sumter County, AL73
- Morgan County, AL73
- Mobile County, AL73
- Baldwin County, AL73
- Russell County, AL73
- Tuscaloosa County, AL72
- Madison County, AL72
- DeKalb County, AL72
- Montgomery County, AL72
- Etowah County, AL70
- Jefferson County, AL66
21Mississippi10 monitored countiesModerate71
- Yalobusha County, MS78
- Lee County, MS76
- Lauderdale County, MS76
- Bolivar County, MS71
- Forrest County, MS71
- Hancock County, MS71
- Jackson County, MS71
- DeSoto County, MS70
- Hinds County, MS69
- Harrison County, MS69
22South Dakota10 monitored countiesModerate71
- Hughes County, SD78
- Meade County, SD77
- Clay County, SD74
- Jackson County, SD73
- Brown County, SD72
- Minnehaha County, SD71
- Codington County, SD71
- Custer County, SD71
- Pennington County, SD69
- Brookings County, SD67
23Nebraska11 monitored countiesModerate71
- Cass County, NE82
- Thomas County, NE79
- Scotts Bluff County, NE79
- Knox County, NE76
- Washington County, NE74
- Lancaster County, NE73
- Hall County, NE73
- Sarpy County, NE72
- Gage County, NE71
- Sioux County, NE71
- Douglas County, NE69
24Louisiana22 monitored countiesModerate71
- Ascension Parish, LA77
- St. John the Baptist Parish, LA76
- St. James Parish, LA76
- Pointe Coupee Parish, LA76
- St. Martin Parish, LA75
- Tangipahoa Parish, LA74
- Orleans Parish, LA73
- Lafourche Parish, LA72
- Caddo Parish, LA72
- Bossier Parish, LA72
- Rapides Parish, LA72
- St. Bernard Parish, LA71
- Terrebonne Parish, LA71
- St. Tammany Parish, LA71
- Livingston Parish, LA71
- Lafayette Parish, LA71
- Ouachita Parish, LA71
- Calcasieu Parish, LA70
- West Baton Rouge Parish, LA70
- Iberville Parish, LA70
- Jefferson Parish, LA69
- East Baton Rouge Parish, LA69
25Oregon21 monitored countiesModerate71
- Columbia County, OR78
- Clackamas County, OR74
- Deschutes County, OR74
- Wallowa County, OR74
- Wasco County, OR73
- Baker County, OR73
- Union County, OR73
- Washington County, OR72
- Multnomah County, OR72
- Linn County, OR72
- Marion County, OR71
- Harney County, OR70
- Lake County, OR69
- Jefferson County, OR69
- Crook County, OR68
- Umatilla County, OR68
- Josephine County, OR67
- Jackson County, OR67
- Grant County, OR67
- Lane County, OR66
- Klamath County, OR66
26Washington31 monitored countiesModerate71
- Pacific County, WA87
- Jefferson County, WA82
- Skagit County, WA80
- Grays Harbor County, WA80
- Kitsap County, WA79
- Garfield County, WA78
- Whatcom County, WA77
- Thurston County, WA77
- Lewis County, WA76
- Mason County, WA76
- Cowlitz County, WA76
- Adams County, WA75
- Columbia County, WA75
- Clallam County, WA74
- Klickitat County, WA74
- Franklin County, WA74
- Whitman County, WA73
- Kittitas County, WA72
- Clark County, WA72
- Benton County, WA72
- Walla Walla County, WA72
- Pierce County, WA71
- Grant County, WA71
- King County, WA70
- Snohomish County, WA70
- Spokane County, WA69
- Stevens County, WA69
- Okanogan County, WA67
- Asotin County, WA67
- Chelan County, WA66
- Yakima County, WA66
27Georgia26 monitored countiesModerate70
- Cobb County, GA77
- Dawson County, GA77
- Charlton County, GA77
- Rockdale County, GA76
- Pike County, GA75
- Murray County, GA75
- Henry County, GA72
- Glynn County, GA72
- Douglas County, GA71
- Chatham County, GA71
- DeKalb County, GA70
- Clayton County, GA70
- Houston County, GA70
- Washington County, GA70
- Coffee County, GA70
- Floyd County, GA69
- Hall County, GA69
- Clarke County, GA69
- Fulton County, GA68
- Walker County, GA68
- Lowndes County, GA68
- Dougherty County, GA68
- Muscogee County, GA68
- Gwinnett County, GA67
- Bibb County, GA66
- Richmond County, GA65
28Tennessee23 monitored countiesModerate70
- Claiborne County, TN78
- DeKalb County, TN77
- Sevier County, TN77
- Wilson County, TN76
- Anderson County, TN76
- Williamson County, TN75
- Jefferson County, TN75
- Putnam County, TN75
- Maury County, TN74
- Loudon County, TN74
- Roane County, TN74
- Lawrence County, TN74
- Montgomery County, TN73
- Sullivan County, TN73
- Dyer County, TN73
- McMinn County, TN72
- Blount County, TN72
- Madison County, TN72
- Hamilton County, TN70
- Knox County, TN70
- Sumner County, TN69
- Davidson County, TN68
- Shelby County, TN67
29Kentucky25 monitored countiesModerate70
- Greenup County, KY77
- Morgan County, KY77
- Simpson County, KY76
- Edmonson County, KY76
- Oldham County, KY75
- Washington County, KY75
- Carter County, KY75
- Livingston County, KY75
- Perry County, KY74
- Pike County, KY74
- Bullitt County, KY73
- Boone County, KY73
- Boyd County, KY73
- Warren County, KY73
- Pulaski County, KY73
- Jessamine County, KY72
- Fayette County, KY72
- Campbell County, KY72
- Christian County, KY72
- Hardin County, KY71
- Bell County, KY71
- McCracken County, KY71
- Hancock County, KY71
- Daviess County, KY70
- Jefferson County, KY67
30Kansas12 monitored countiesModerate70
- Douglas County, KS76
- Leavenworth County, KS76
- Sherman County, KS76
- Ford County, KS75
- Chase County, KS73
- Johnson County, KS70
- Shawnee County, KS70
- Sumner County, KS70
- Trego County, KS70
- Neosho County, KS69
- Sedgwick County, KS69
- Wyandotte County, KS67
31New York27 monitored countiesModerate69
- Saratoga County, NY78
- Hamilton County, NY78
- Oswego County, NY78
- Wayne County, NY78
- Putnam County, NY77
- Dutchess County, NY77
- Tompkins County, NY77
- Jefferson County, NY77
- Niagara County, NY76
- Orange County, NY74
- Chautauqua County, NY74
- Oneida County, NY73
- Westchester County, NY72
- Rockland County, NY72
- Onondaga County, NY72
- Steuben County, NY72
- Nassau County, NY71
- Richmond County, NY70
- Essex County, NY70
- Monroe County, NY70
- Kings County, NY69
- Suffolk County, NY68
- Queens County, NY68
- Albany County, NY68
- Bronx County, NY67
- Erie County, NY67
- New York County, NY66
32Missouri21 monitored countiesModerate69
- Stoddard County, MO80
- Monroe County, MO77
- Boone County, MO76
- Callaway County, MO75
- Ste. Genevieve County, MO75
- Taney County, MO74
- Perry County, MO73
- Cass County, MO73
- Cedar County, MO73
- Lincoln County, MO71
- Andrew County, MO71
- Jasper County, MO71
- St. Louis County, MO70
- Jefferson County, MO70
- Jackson County, MO69
- Buchanan County, MO69
- Greene County, MO69
- Clay County, MO68
- Clinton County, MO67
- St. Charles County, MO65
- St. Louis city, MO62
33Arkansas11 monitored countiesModerate69
- Clark County, AR77
- Newton County, AR75
- Washington County, AR73
- Crittenden County, AR72
- Ashley County, AR71
- Polk County, AR71
- Arkansas County, AR71
- Jackson County, AR70
- Union County, AR69
- Garland County, AR69
- Pulaski County, AR66
34Connecticut8 monitored countiesModerate68
- Windham County, CT77
- Tolland County, CT70
- New London County, CT70
- Litchfield County, CT68
- Hartford County, CT66
- New Haven County, CT66
- Fairfield County, CT63
- Middlesex County, CT62
35Delaware3 monitored countiesModerate68
- Sussex County, DE72
- Kent County, DE69
- New Castle County, DE67
36District of Columbia1 monitored countyModerate68
- District of Columbia, DC68
37Iowa15 monitored countiesModerate68
- Bremer County, IA73
- Pottawattamie County, IA72
- Muscatine County, IA71
- Montgomery County, IA70
- Woodbury County, IA70
- Johnson County, IA70
- Van Buren County, IA70
- Black Hawk County, IA69
- Polk County, IA68
- Webster County, IA68
- Harrison County, IA68
- Linn County, IA66
- Palo Alto County, IA65
- Clinton County, IA65
- Scott County, IA65
38Minnesota23 monitored countiesModerate68
- Pine County, MN78
- Washington County, MN77
- Mille Lacs County, MN77
- Goodhue County, MN75
- Cook County, MN73
- Winona County, MN73
- Cass County, MN71
- Ramsey County, MN70
- Lake County, MN70
- Dakota County, MN69
- Stearns County, MN69
- Carlton County, MN69
- Crow Wing County, MN69
- Anoka County, MN68
- Scott County, MN68
- Olmsted County, MN68
- Lyon County, MN68
- Wright County, MN67
- Beltrami County, MN66
- Hennepin County, MN65
- Blue Earth County, MN65
- Becker County, MN64
- St. Louis County, MN61
39Pennsylvania38 monitored countiesModerate67
- Somerset County, PA77
- Elk County, PA77
- Franklin County, PA76
- Susquehanna County, PA75
- Monroe County, PA74
- Wyoming County, PA74
- Bradford County, PA73
- Tioga County, PA72
- Westmoreland County, PA71
- Fayette County, PA71
- Indiana County, PA71
- Cambria County, PA71
- Warren County, PA71
- Erie County, PA71
- Centre County, PA71
- Greene County, PA70
- Armstrong County, PA70
- Blair County, PA70
- Adams County, PA70
- Lycoming County, PA70
- Montgomery County, PA70
- Bucks County, PA70
- Lackawanna County, PA70
- Washington County, PA69
- Cumberland County, PA69
- Lehigh County, PA69
- Mercer County, PA68
- Lebanon County, PA68
- Dauphin County, PA68
- Berks County, PA68
- Northampton County, PA68
- Delaware County, PA68
- Chester County, PA68
- York County, PA67
- Beaver County, PA65
- Lancaster County, PA65
- Philadelphia County, PA64
- Allegheny County, PA61
40Indiana33 monitored countiesModerate67
- Brown County, IN77
- Hendricks County, IN76
- Shelby County, IN76
- Carroll County, IN76
- Wabash County, IN76
- Knox County, IN76
- Perry County, IN76
- Boone County, IN75
- Posey County, IN75
- Warrick County, IN73
- Henry County, IN71
- Bartholomew County, IN71
- Monroe County, IN71
- Greene County, IN71
- Dubois County, IN71
- Spencer County, IN71
- Tippecanoe County, IN71
- Madison County, IN70
- Whitley County, IN70
- Howard County, IN70
- Clark County, IN70
- Floyd County, IN70
- Hamilton County, IN69
- Delaware County, IN69
- Vanderburgh County, IN69
- Vigo County, IN68
- Elkhart County, IN67
- Allen County, IN66
- Marion County, IN65
- Porter County, IN65
- St. Joseph County, IN65
- LaPorte County, IN64
- Lake County, IN63
41Wisconsin29 monitored countiesModerate67
- Taylor County, WI77
- Vilas County, WI76
- La Crosse County, WI76
- Fond du Lac County, WI75
- Jefferson County, WI73
- Manitowoc County, WI71
- Columbia County, WI71
- Sauk County, WI71
- Rock County, WI70
- Marathon County, WI70
- Dodge County, WI69
- Grant County, WI69
- Ashland County, WI69
- Jackson County, WI69
- Monroe County, WI69
- Eau Claire County, WI69
- Dane County, WI68
- Forest County, WI68
- Outagamie County, WI68
- Door County, WI68
- Ozaukee County, WI67
- Walworth County, WI67
- Brown County, WI67
- Kewaunee County, WI67
- Waukesha County, WI66
- Milwaukee County, WI63
- Sheboygan County, WI62
- Kenosha County, WI62
- Racine County, WI62
42North Dakota9 monitored countiesModerate67
- Mercer County, ND71
- Oliver County, ND71
- Burleigh County, ND70
- Billings County, ND70
- Dunn County, ND70
- McKenzie County, ND70
- Ward County, ND70
- Burke County, ND67
- Cass County, ND65
43Ohio37 monitored countiesModerate66
- Columbiana County, OH89
- Knox County, OH73
- Noble County, OH73
- Lorain County, OH73
- Athens County, OH73
- Washington County, OH73
- Wood County, OH71
- Clermont County, OH71
- Greene County, OH71
- Lawrence County, OH71
- Licking County, OH70
- Delaware County, OH70
- Ashtabula County, OH70
- Geauga County, OH70
- Clinton County, OH70
- Miami County, OH70
- Allen County, OH70
- Clark County, OH68
- Belmont County, OH68
- Mahoning County, OH68
- Preble County, OH68
- Scioto County, OH68
- Summit County, OH67
- Medina County, OH67
- Warren County, OH67
- Montgomery County, OH67
- Jefferson County, OH66
- Madison County, OH65
- Lake County, OH65
- Portage County, OH65
- Stark County, OH65
- Hamilton County, OH65
- Lucas County, OH64
- Franklin County, OH63
- Trumbull County, OH63
- Butler County, OH62
- Cuyahoga County, OH61
44Michigan27 monitored countiesModerate66
- Keweenaw County, MI92
- Tuscola County, MI76
- Wexford County, MI76
- Huron County, MI75
- Clinton County, MI75
- Mason County, MI75
- Benzie County, MI75
- Genesee County, MI72
- Missaukee County, MI71
- Bay County, MI70
- Cass County, MI70
- Muskegon County, MI70
- Ingham County, MI69
- Marquette County, MI69
- Manistee County, MI68
- Schoolcraft County, MI68
- St. Clair County, MI67
- Oakland County, MI67
- Berrien County, MI67
- Lenawee County, MI67
- Macomb County, MI66
- Washtenaw County, MI66
- Ottawa County, MI66
- Kalamazoo County, MI65
- Kent County, MI64
- Wayne County, MI63
- Allegan County, MI63
45Oklahoma20 monitored countiesModerate66
- Mayes County, OK76
- Grant County, OK74
- Carter County, OK73
- Sequoyah County, OK72
- Kay County, OK72
- Canadian County, OK70
- Kiowa County, OK70
- Osage County, OK70
- Washington County, OK70
- Creek County, OK70
- Cleveland County, OK68
- Pittsburg County, OK68
- Adair County, OK68
- McClain County, OK67
- Comanche County, OK67
- Ottawa County, OK67
- Oklahoma County, OK65
- Dewey County, OK65
- Tulsa County, OK63
- Love County, OK60
46Colorado30 monitored countiesModerate64
- Jackson County, CO87
- San Juan County, CO86
- Routt County, CO79
- Pitkin County, CO79
- Prowers County, CO78
- Fremont County, CO78
- Alamosa County, CO76
- Delta County, CO74
- Grand County, CO70
- Archuleta County, CO70
- San Miguel County, CO70
- Gilpin County, CO68
- Pueblo County, CO68
- Montezuma County, CO68
- Mesa County, CO68
- El Paso County, CO67
- Clear Creek County, CO67
- Gunnison County, CO67
- Garfield County, CO67
- Arapahoe County, CO65
- Adams County, CO65
- Boulder County, CO65
- Douglas County, CO65
- Denver County, CO63
- La Plata County, CO63
- Park County, CO62
- Weld County, CO60
- Jefferson County, CO58
- Larimer County, CO58
- Chaffee County, CO58
47Illinois23 monitored countiesModerate62
- Jo Daviess County, IL77
- Effingham County, IL77
- Macoupin County, IL76
- Adams County, IL76
- Clark County, IL76
- Lake County, IL70
- Rock Island County, IL70
- Randolph County, IL70
- Sangamon County, IL70
- Hamilton County, IL70
- St. Clair County, IL69
- Macon County, IL68
- DuPage County, IL67
- Champaign County, IL67
- Winnebago County, IL67
- Peoria County, IL67
- McLean County, IL67
- Jersey County, IL67
- McHenry County, IL65
- Will County, IL65
- Madison County, IL65
- Kane County, IL64
- Cook County, IL58
48Utah17 monitored countiesModerate61
- Garfield County, UT89
- Wayne County, UT87
- San Juan County, UT70
- Tooele County, UT68
- Cache County, UT68
- Grand County, UT68
- Iron County, UT68
- Washington County, UT68
- Box Elder County, UT67
- Carbon County, UT67
- Utah County, UT64
- Duchesne County, UT63
- Wasatch County, UT63
- Weber County, UT63
- Uintah County, UT62
- Davis County, UT61
- Salt Lake County, UT55
49New Mexico16 monitored countiesModerate61
- Los Alamos County, NM87
- Taos County, NM84
- Socorro County, NM82
- Chaves County, NM77
- Rio Arriba County, NM73
- Santa Fe County, NM71
- Sandoval County, NM68
- Valencia County, NM68
- Lea County, NM68
- Luna County, NM66
- San Juan County, NM63
- Catron County, NM63
- Lincoln County, NM63
- Bernalillo County, NM56
- Eddy County, NM55
- Doña Ana County, NM43
50Texas45 monitored countiesModerate59
- Karnes County, TX92
- Wilson County, TX91
- Potter County, TX80
- Rockwall County, TX78
- Lubbock County, TX77
- Polk County, TX76
- Ellis County, TX75
- Hunt County, TX75
- Smith County, TX75
- Gregg County, TX73
- Brazos County, TX72
- Bowie County, TX71
- Harrison County, TX71
- Johnson County, TX71
- Orange County, TX71
- Victoria County, TX71
- Ector County, TX71
- Kaufman County, TX70
- Parker County, TX70
- Hood County, TX70
- Atascosa County, TX70
- Randall County, TX70
- Maverick County, TX69
- Navarro County, TX68
- Bell County, TX68
- McLennan County, TX68
- Brewster County, TX68
- Montgomery County, TX67
- Jefferson County, TX67
- Culberson County, TX67
- Galveston County, TX66
- Hidalgo County, TX66
- Brazoria County, TX65
- Webb County, TX65
- Travis County, TX65
- Kleberg County, TX63
- Dallas County, TX62
- Nueces County, TX62
- Cameron County, TX62
- Bexar County, TX60
- Denton County, TX57
- Collin County, TX55
- Tarrant County, TX52
- Harris County, TX50
- El Paso County, TX39
51Nevada9 monitored countiesModerate57
- Nye County, NV78
- Lyon County, NV75
- Douglas County, NV75
- Carson City, NV74
- Churchill County, NV73
- Elko County, NV73
- White Pine County, NV68
- Washoe County, NV65
- Clark County, NV53
52Arizona13 monitored countiesModerate55
- Navajo County, AZ88
- Mohave County, AZ83
- Apache County, AZ71
- La Paz County, AZ68
- Yavapai County, AZ67
- Yuma County, AZ66
- Cochise County, AZ65
- Coconino County, AZ65
- Santa Cruz County, AZ64
- Pima County, AZ60
- Gila County, AZ57
- Maricopa County, AZ50
- Pinal County, AZ50
53California47 monitored countiesUnhealthy for sensitive groups45
- Sonoma County, CA92
- Lake County, CA81
- Solano County, CA79
- Marin County, CA76
- Mono County, CA75
- San Benito County, CA75
- Monterey County, CA74
- Santa Cruz County, CA74
- Tuolumne County, CA73
- Humboldt County, CA73
- Del Norte County, CA73
- Amador County, CA73
- El Dorado County, CA73
- Glenn County, CA73
- Tehama County, CA73
- Calaveras County, CA72
- Siskiyou County, CA72
- Colusa County, CA72
- Mendocino County, CA71
- Nevada County, CA71
- Santa Barbara County, CA70
- Butte County, CA70
- Shasta County, CA70
- Yolo County, CA69
- Mariposa County, CA68
- Trinity County, CA68
- Sutter County, CA68
- Ventura County, CA67
- San Luis Obispo County, CA67
- San Joaquin County, CA67
- Placer County, CA65
- Sacramento County, CA64
- Madera County, CA62
- Merced County, CA62
- Orange County, CA61
- Inyo County, CA60
- Stanislaus County, CA60
- Kings County, CA58
- Plumas County, CA58
- San Diego County, CA50
- Fresno County, CA50
- Tulare County, CA48
- Imperial County, CA46
- Kern County, CA44
- Los Angeles County, CA27
- Riverside County, CA25
- San Bernardino County, CA22
Informational only, not professional advice. This ranking summarises public EPA monitoring records. It is not a health assessment or a substitute for checking current conditions at a specific address.
How this is calculated
The same air formula as the Air & Water Score by ZIP Code tool, applied to a population-weighted average across every monitored county in a state instead of one county at a time. The full derivation, sources, and coverage limits live on that page; this section summarises.
county 90th-percentile AQI, averaged across a state's monitored counties, weighted by county population state air score = 100 − (weighted average AQI ÷ 2), floored at 0
From EPA AirData's annual AQI by county file for 2025, the same 985 monitored counties behind the ZIP score tool. Air has no adjustable weighting — unlike the water formula's violation coefficients, the AQI-to-score mapping follows EPA's own published breakpoints directly, so there is nothing to expose as a control here.
Sources
- EPA AirData — annual AQI by county (2025)
- US Census Bureau — county population estimates (used only to weight the state average)
Last reviewed: September 2026 · Data in use: AirData 2025 · Dataset built 2026-09-02
Frequently asked questions
Why are some states missing from the ranking?
A state only appears once it has at least one county with an EPA air monitor. EPA's monitor network covers about half of US counties, concentrated where people live, so a state with only sparsely populated, unmonitored counties won't appear at all rather than being scored from no data.
How is a state's score calculated when it has several monitored counties?
Each monitored county's 90th-percentile AQI is averaged, weighted by that county's population, then scored with the same formula as the ZIP score tool's air half: 100 minus half the weighted AQI, floored at 0. Weighting by population stops one small, lightly populated county's reading from outweighing a county where most of the state's monitored residents actually live.
Can I trust the rank of a state with only one monitored county?
Treat it more cautiously. A state ranked from a single county is one measurement standing in for the whole state, not an average across many — expand that state's row to see exactly which county and how many days it measured. A state built from a dozen monitored counties is a sturdier estimate than one built from a single small county.
Does a high rank mean every county in that state has clean air?
No. The rank is a population-weighted average across only the monitored counties, and air quality varies by county — a state can rank well overall while one of its monitored counties, or an unmonitored one nearby, reads worse. Expand the state to see its own counties individually, or look up a specific ZIP code on the Air & Water Score tool.
Related tools
Air & Water Score by ZIP Code
A composite score for outdoor air quality and drinking-water compliance in any US ZIP code, built from EPA AirData and SDWIS/ECHO records.
Open tool →Compare Two ZIP CodesSide-by-side air quality and drinking water score for any two US ZIP codes, from the same EPA data as the ZIP score tool.
Open tool →Drinking Water by UtilityLook up a US public water system by name and see its EPA violation record and score, from the same SDWIS/ECHO data as the ZIP score tool.
Open tool →Worst Water Violations by StateEvery US state and territory with an active public water system, ranked worst-first by a pooled drinking-water compliance score built from EPA SDWIS/ECHO violation records, drilling down to the counties behind each rank.
Open tool →Best & Worst Counties for Air and Water QualityEvery US county with both an EPA air monitor and an active water system, ranked by composite score — the top 100 best and worst in the country, each with a representative ZIP.
Open tool →Cleanest Drinking Water by StateEvery US state and territory with an active public water system, ranked best-first by the same pooled drinking-water compliance score as the worst-water ranking.
Open tool →