The Most Polluted Cities in America [+Emission Sources]

Five of the 15 most polluted cities in our ranking came from California. The worst is the Riverside-San Bernardino-Ontario metropolitan center, with 65 days per year categorized as unhealthy, very unhealthy, or hazardous. Americans produce millions of pollution each year, contributing to lung cancer and shortened life spans for American families, and it is especially hazardous in the cities with the most pollution.

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Sara Routhier, Managing Editor and Outreach Director, has professional experience as an educator, SEO specialist, and content marketer. She has over five years of experience in the insurance industry. As a researcher, data nerd, writer, and editor she strives to curate educational, enlightening articles that provide you with the must-know facts and best-kept secrets within the overwhelming world o...

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Cynthia Lanctot is an insurance professional with ten years of industry experience. Cynthia is licensed in several states, and holds an associate in claims law, as well as a bachelor’s degree in English. Cynthia’s experience includes the New England and Northeast states. She currently works as a liability claims professional and an occasional online contributor.

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Reviewed by Cynthia Lanctot
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UPDATED: Jul 16, 2021

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While air pollution in the U.S. has improved remarkably since the passage of the Clean Air Act, the Environmental Protection Agency (EPA) estimates that 137 million people nationwide still live in counties where air pollution levels exceeded air quality standards.

This article dives deep into the most polluted cities in America. There are several different types of pollution in the cities with the most pollution. Ozone pollution, which appears in warmer temperatures (also known as smog), causes sunburn of the lung. Breathing ozone can lead to shortness of breath, coughing and asthma attacks and can shorten lifespan.

Particle pollution results from many sources that generate particulate matter in the air, such as wildfires, wood-burning devices, coal-fired power plants, and diesel engines. The concentration of particles can enter the bloodstream and the lungs and lead to various forms of cancer, heart diseases, strokes, and asthma.

In 2018, the U.S. emitted 76 million tons of pollution into the atmosphere, which according to the American Lung Association, contributes to increased rates of lung cancer and reduced lifespans among American families.

Air quality standards for common pollutants that pose a health threat to the public are managed by the EPA. These pollutants include ozone, fine and coarse particulate matter (PM2.5 and PM10), sulfur dioxide, lead, carbon monoxide, and nitrogen dioxide.

From 1980 to 2018, the greatest air quality improvements occurred in lead, sulfur dioxide, and carbon monoxide levels.

According to the EPA, efforts to remove lead from automobile gasoline alone helped reduce levels of lead in the air by 89 percent over three decades.

Similarly, a 1990 update to the Clean Air Act known as the Acid Rain Program set a permanent cap on emissions of sulfur dioxide and nitrogen oxides from power plants. The cap helped reduce sulfur dioxide to 9.0 percent of the 1980 value and the level of nitrogen dioxide to 39 percent over the same time period.

While levels of nitrogen dioxide, carbon monoxide, sulfur dioxide, and lead are all below 40 percent of their respective 1980 values, ozone and particle pollution continue to present a major public health risk. With these trends in mind, our researchers at BuyAutoInsurance.com analyzed data from the EPA to find the U.S. metropolitan areas with the highest levels of air pollution.

The EPA uses air pollution measures  known as the Air Quality Index (AQI) to report daily air quality, with higher values corresponding to greater levels of air pollution.

Values between 0-50 are considered good; values between 51-100 are moderate; values between 101-150 are unhealthy for sensitive groups; and values above 151 are unhealthy for the general public. Researchers used AQI data to determine air quality rankings for small, midsize, and large metropolitan areas.

The findings among the small and midsize metros are in line with the findings among the large metros. Specifically, locations in California make repeated appearances on these lists.

When comparing air pollution levels of large metropolitan areas, five of the top 15 metros were found to exist in the coastal state. The incidence is higher among the top 15 small and midsize metros.

Here are the small and midsize metropolitan areas with the worst air quality:

Small MetrosMedian AQIMidsize MetrosMedian AQI
1. Hilo, HI871. Bakersfield, CA84
2. Hanford-Corcoran, CA692. Visalia-Portersville, CA77
3. El Centro, CA623. Fresno, CA74
4. Las Cruces, NM574. El Paso, TX55
5. Madera, CA565. Stockton-Lodi, CA54
6. Chico, CA546. Modesto, CA54
7. Yuba City, CA547. Albuquerque, NM54
8. Merced, CA518. Oxnard-Thousand Oaks-Ventura, CA52
9. Decatur, IL519. Davenport-Moline-Rock Island, IA-IL52
10. Greeley, CO5010. Montgomery, AL52
11. San Luis Obispo-Paso Robles-Arroyo Grande, CA4911. Tulsa, OK50
12. Missoula, MT4812. Fort Collins, CO50
13. Weirton-Steubenville, WV-OK4813. Ogden-Clearfield, UT50
14. Amarillo, TX4714. Beaumont-Port Arthur, TX49
15. Evansville, IN-KY4715. Boise City, ID49
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In this article, you’ll find information on the most polluted cities in the world, the most polluted cities in the US, the most polluted countries, and a special look at the most polluted cities in California.

Often, a car owner’s environment can affect their insurance rates. Find out more about different types of auto insurances and how they might apply to you on our auto insurance coverages page.

If you’re looking for auto insurance quotes right away, just enter your ZIP code into our online quote comparison tool. You’ll get the best rates in your area based on your information.

The 15 Large Metros with the Worst Air Quality

#15 – New York-Newark-Jersey City, NY-NJ-PA

  • Median AQI: 53
  • Max AQI: 210
  • Good air quality: 156 days per year
  • Moderate or unhealthy for sensitive groups: 206 days per year
  • Unhealthy, very unhealthy, or hazardous: 3 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

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#14 – San Francisco-Oakland-Hayward CA

  • Median AQI: 53
  • Max AQI: 245
  • Good air quality: 147 days per year
  • Moderate or unhealthy for sensitive groups: 206 days per year
  • Unhealthy, very unhealthy, or hazardous: 12 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

#13 – Detroit-Warren-Dearborn, MI

  • Median AQI: 54
  • Max AQI: 151
  • Good air quality: 137 days per year
  • Moderate or unhealthy for sensitive groups: 226 days per year
  • Unhealthy, very unhealthy, or hazardous: 2 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

#12 – St. Louis, MO-IL

  • Median AQI: 54
  • Max AQI: 182
  • Good air quality: 157 days per year
  • Moderate or unhealthy for sensitive groups: 206 days per year
  • Unhealthy, very unhealthy, or hazardous: 2 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

#11 – Pittsburgh, PA

  • Median AQI: 55
  • Max AQI: 154
  • Good air quality: 136 days per year
  • Moderate or unhealthy for sensitive groups: 228 days per year
  • Unhealthy, very unhealthy, or hazardous: 1 day per year
  • Most common pollutant: Fine particulate matter (PM2.5)

#10 – Philadelphia-Camden-Wilmington, PA-NJ-DE-MD

  • Median AQI: 55
  • Max AQI: 164
  • Good air quality: 132 days per year
  • Moderate or unhealthy for sensitive groups: 230 days per year
  • Unhealthy, very unhealthy, or hazardous: 3 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

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#9 – Chicago-Naperville-Elgin, IL-IN-WI

  • Median AQI: 57
  • Max AQI: 177
  • Good air quality: 117 days per year
  • Moderate or unhealthy for sensitive groups: 242 days per year
  • Unhealthy, very unhealthy, or hazardous: 6 days per year
  • Most common pollutant: Fine particulate matter (PM2.5)

#8 – Las Vegas-Henderson-Paradise, NV

  • Median AQI: 61
  • Max AQI: 154
  • Good air quality: 122 days per year
  • Moderate or unhealthy for sensitive groups: 242 days per year
  • Unhealthy, very unhealthy, or hazardous: 1 day per year
  • Most common pollutant: Ozone

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#7 – Salt Lake City, UT

  • Median AQI: 61
  • Max AQI: 169
  • Good air quality: 138 days per year
  • Moderate or unhealthy for sensitive groups: 225 days per year
  • Unhealthy, very unhealthy, or hazardous: 2 days per year
  • Most common pollutant: Ozone

#6 – Sacramento-Roseville-Arden-Arcade, CA

  • Median AQI: 61
  • Max AQI: 314
  • Good air quality: 124 days per year
  • Moderate or unhealthy for sensitive groups: 217 days per year
  • Unhealthy, very unhealthy, or hazardous: 24 days per year
  • Most common pollutant: Ozone

#5 – San Diego-Carlsbad, CA

  • Median AQI: 64
  • Max AQI: 143
  • Good air quality: 73 days per year
  • Moderate or unhealthy for sensitive groups: 292 days per year
  • Unhealthy, very unhealthy, or hazardous: 0 days per year
  • Most common pollutant: Ozone

#4 – Denver-Aurora-Lakewood, CO

  • Median AQI: 64
  • Max AQI: 174
  • Good air quality: 83 days per year
  • Moderate or unhealthy for sensitive groups: 274 days per year
  • Unhealthy, very unhealthy, or hazardous: 8 days per year
  • Most common pollutant: Ozone

#3 – Los Angeles-Long Beach-Anaheim, CA

  • Median AQI: 77
  • Max AQI: 201
  • Good air quality: 35 days per year
  • Moderate or unhealthy for sensitive groups: 310 days per year
  • Unhealthy, very unhealthy, or hazardous: 20 days per year
  • Most common pollutant: Ozone

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#2 – Phoenix-Mesa-Scottsdale, AZ

  • Median AQI: 77
  • Max AQI: 996
  • Good air quality: 42 days per year
  • Moderate or unhealthy for sensitive groups: 304 days per year
  • Unhealthy, very unhealthy, or hazardous: 19 days per year
  • Most common pollutant: Coarse particulate matter (PM10)

#1 – Riverside-San Bernardino-Ontario, CA

  • Median AQI: 97
  • Max AQI: 296
  • Good air quality: 25 days per year
  • Moderate or unhealthy for sensitive groups: 275 days per year
  • Unhealthy, very unhealthy, or hazardous: 65 days per year
  • Most common pollutant: Ozone

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Air Quality Results for All US Metro Areas

Metro AreaAvg Air Quality IndexMax Air Quality IndexGood DaysUnhealthy DaysHazardous DaysMost Common PollutantPopulationRank
Riverside-San Bernardino-Ontario, CA972962527565Ozone4,622,3611
Hilo, HI87249127134104SO2200,9832
Bakersfield, CA841906527327Ozone896,7643
Phoenix-Mesa-Scottsdale, AZ779964230419PM104,857,9624
Los Angeles-Long Beach-Anaheim, CA772013531020Ozone13,291,4865
Visalia-Porterville, CA771747326626Ozone465,8616
Fresno, CA741858426219Ozone994,4007
Hanford-Corcoran, CA69180892679Ozone151,3668
Denver-Aurora-Lakewood, CO64174832748Ozone2,932,4159
San Diego-Carlsbad, CA64143732920Ozone3,343,36410
El Centro, CA62286952619Ozone181,82711
Sacramento--Roseville--Arden-Arcade, CA6131412421724Ozone2,345,21012
Salt Lake City, UT611691382252Ozone1,222,54013
Las Vegas-Henderson-Paradise, NV611541222421Ozone2,231,64714
Las Cruces, NM571871442174Ozone217,52215
Chicago-Naperville-Elgin, IL-IN-WI571771172426PM2.59,498,71616
Madera, CA561651522085Ozone157,67217
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD551641322303PM2.56,096,37218
El Paso, TX551641332302Ozone845,55319
Pittsburgh, PA551541362281PM2.52,324,74320
Chico, CA5444515219518Ozone231,25621
Yuba City, CA5433515319913PM2.5174,84822
Stockton-Lodi, CA5430815220013PM2.5752,66023
Modesto, CA5424015719315Ozone549,81524
St. Louis, MO-IL541821572062PM2.52,805,46525
Albuquerque, NM541651512131Ozone915,92726
Detroit-Warren-Dearborn, MI541511372262PM2.54,326,44227
San Francisco-Oakland-Hayward, CA5324514720612PM2.54,729,48428
New York-Newark-Jersey City, NY-NJ-PA532101562063PM2.519,979,47729
Oxnard-Thousand Oaks-Ventura, CA521661741901Ozone850,96730
Cincinnati, OH-KY-IN521591632002PM2.52,190,20931
Birmingham-Hoover, AL521561661981PM2.51,151,80132
Davenport-Moline-Rock Island, IA-IL521081721930PM2.5381,45133
Montgomery, AL52931501760PM2.5373,22534
Houston-The Woodlands-Sugar Land, TX512041661909PM2.56,997,38435
Merced, CA511711731839Ozone274,76536
Decatur, IL511261721930PM2.5104,71237
Minneapolis-St. Paul-Bloomington, MN-WI511221731920PM2.53,629,19038
Tulsa, OK501921841801PM2.5993,79739
Fort Collins, CO501691951673Ozone350,51840
Dallas-Fort Worth-Arlington, TX501661861709Ozone7,539,71141
Ogden-Clearfield, UT501571841783Ozone675,06742
Indianapolis-Carmel-Anderson, IN501561871771PM2.52,048,70343
Greeley, CO501331871780Ozone314,30544
Washington-Arlington-Alexandria, DC-VA-MD-WV491661941701PM2.56,249,95045
Beaumont-Port Arthur, TX491541951691PM2.5409,52646
Boise City, ID491342001650PM2.5730,42647
San Luis Obispo-Paso Robles-Arroyo Grande, CA491332021630Ozone284,01048
Tucson, AZ491291961690Ozone1,039,07349
Louisville/Jefferson County, KY-IN481662051582PM2.51,297,30150
Missoula, MT481531981661PM2.5118,79151
Reno, NV481462131520Ozone469,76452
Cleveland-Elyria, OH481382021630Ozone2,057,00953
Atlanta-Sandy Springs-Roswell, GA481332091560PM2.55,949,95154
Weirton-Steubenville, WV-OH481102071580PM2.5117,06455
San Jose-Sunnyvale-Santa Clara, CA4719421613811Ozone1,999,10756
Kansas City, MO-KS471722111531Ozone2,143,65157
Amarillo, TX471612241401Ozone265,94758
Baltimore-Columbia-Towson, MD471502081570PM2.52,802,78959
Oklahoma City, OK471502121530Ozone1,396,44560
Evansville, IN-KY471432041610Ozone314,67261
Colorado Springs, CO471332261390Ozone738,93962
Farmington, NM471292131520Ozone125,04363
Santa Maria-Santa Barbara, CA471142441210Ozone446,52764
Asheville, NC461992341256Ozone459,58565
Provo-Orem, UT461622181407Ozone633,76866
Boulder, CO461592191421Ozone326,07867
Grand Junction, CO461502161490Ozone153,20768
Dayton, OH461402181470PM2.5806,54869
Logan, UT-ID461332351300Ozone140,79470
New Orleans-Metairie, LA461122191460PM2.51,270,39971
Omaha-Council Bluffs, NE-IA461082291360PM2.5942,19872
Yuma, AZ451692391251Ozone212,12873
Baton Rouge, LA451532241401Ozone831,31074
Knoxville, TN451332401250Ozone883,30975
Boston-Cambridge-Newton, MA-NH451262251400PM2.54,875,39076
Flagstaff, AZ451262401250Ozone142,85477
Charlotte-Concord-Gastonia, NC-SC451222291350Ozone2,569,21378
Waterloo-Cedar Falls, IA451122301350PM2.5169,65979
Canton-Massillon, OH451082371280PM2.5398,65580
Raleigh, NC45902401210PM2.51,362,54081
Spokane-Spokane Valley, WA4425722413011PM2.5573,49382
Seattle-Tacoma-Bellevue, WA441922391197Ozone3,939,36383
Milwaukee-Waukesha-West Allis, WI441692361272Ozone1,576,11384
Memphis, TN-MS-AR441592421221Ozone1,350,62085
Providence-Warwick, RI-MA441472651000Ozone1,621,33786
Springfield, OH441402401250PM2.5134,58587
Cedar Rapids, IA441292491160PM2.5272,29588
Lancaster, PA441262461190Ozone543,55789
Columbus, OH441222541110Ozone2,106,54190
Fort Wayne, IN441222431220Ozone437,63191
Santa Fe, NM44122279860Ozone150,05692
Rapid City, SD441182581070Ozone148,74993
Austin-Round Rock, TX441152391260PM2.52,168,31694
Show Low, AZ441152611020Ozone110,44595
Youngstown-Warren-Boardman, OH-PA441152451200Ozone538,95296
Kingsport-Bristol-Bristol, TN-VA441142391260Ozone306,61697
Jackson, MS441122551100PM2.5580,16698
Bloomington, IL441082481170PM2.5188,59799
Lake Charles, LA441082361290PM2.5210,080100
St. George, UT441082281370Ozone171,700101
Chattanooga, TN-GA441012521130PM2.5560,793102
Winston-Salem, NC441012331320PM2.5671,456103
Sierra Vista-Douglas, AZ4490276890Ozone126,770104
Redding, CA43190277826Ozone180,040105
Sheboygan, WI43185186512Ozone115,456106
San Antonio-New Braunfels, TX431622511131Ozone2,518,036107
Idaho Falls, ID43154287771Ozone148,904108
Nashville-Davidson--Murfreesboro--Franklin, TN431512471171PM2.51,930,961109
South Bend-Mishawaka, IN-MI431332441210Ozone322,424110
Bloomington, IN431292561080Ozone167,762111
Tampa-St. Petersburg-Clearwater, FL431292421230Ozone3,142,663112
Miami-Fort Lauderdale-West Palm Beach, FL431262641010PM2.56,198,782113
Little Rock-North Little Rock-Conway, AR431222571080PM2.5741,104114
Springfield, IL431222531100Ozone207,636115
Terre Haute, IN431152421230Ozone169,725116
St. Joseph, MO-KS431122511140PM2.5126,490117
Peoria, IL431012551100Ozone368,373118
Prescott, AZ43101292730Ozone231,993119
Durham-Chapel Hill, NC43100268910PM2.5575,412120
Vallejo-Fairfield, CA422472639012Ozone446,610121
Medford, OR422331957731PM2.5219,564122
Racine, WI42161187472Ozone196,584123
Allentown-Bethlehem-Easton, PA-NJ421362461190Ozone842,913124
Madison, WI42122271940Ozone660,422125
Champaign-Urbana, IL42112283820Ozone239,643126
Harrisburg-Carlisle, PA421082511140PM2.5574,659127
Akron, OH421052561090PM2.5704,845128
Morristown, TN42100202420Ozone118,581129
Topeka, KS4299272930PM2.5232,594130
Fayetteville-Springdale-Rogers, AR-MO4287266990Ozone549,128131
Bridgeport-Stamford-Norwalk, CT411852581007Ozone943,823132
Kalispell, MT41182268925Ozone102,106133
Jacksonville, FL41155267971PM2.51,534,701134
Gadsden, AL41153231921Ozone102,501135
Green Bay, WI41151288761Ozone321,591136
Toledo, OH41151272921Ozone602,871137
Augusta-Richmond County, GA-SC411502521130PM2.5604,167138
Richmond, VA41147280850Ozone1,306,172139
Appleton, WI41132271940Ozone237,524140
Eau Claire, WI41129282830Ozone168,669141
Huntsville, AL41115275900PM2.5462,693142
McAllen-Edinburg-Mission, TX411152381250PM2.5865,939143
Sioux City, IA-NE-SD41112284810Ozone169,045144
Greensboro-High Point, NC41105277800Ozone767,711145
Wheeling, WV-OH41105271940Ozone140,045146
Wichita, KS411002611040Ozone644,888147
Brownsville-Harlingen, TX41992461190PM2.5423,908148
Lafayette, LA4197266990Ozone489,364149
Yakima, WA402142391179PM2.5251,446150
Trenton, NJ40187283811Ozone369,811151
Muskegon, MI40174203343Ozone173,588152
New Haven-Milford, CT40156276872Ozone857,620153
Bismarck, ND40153282792Ozone132,678154
Ann Arbor, MI40150281840Ozone370,963155
Holland, MI40150232540Ozone117,327156
Salisbury, MD-DE40140295700Ozone409,979157
Shreveport-Bossier City, LA40128279860Ozone436,341158
Niles-Benton Harbor, MI40126208370Ozone154,141159
Springfield, MA40126277880Ozone631,761160
Whitewater-Elkhorn, WI40126202350Ozone103,718161
Lawton, OK40122275900Ozone126,198162
State College, PA40122286790Ozone162,805163
Huntington-Ashland, WV-KY-OH40119291740PM2.5352,823164
Reading, PA40117270950Ozone420,152165
Grand Rapids-Wyoming, MI40115290750Ozone1,069,405166
Gulfport-Biloxi-Pascagoula, MS40115278860PM2.5397,261167
Kalamazoo-Portage, MI40115282740PM2.5340,318168
Lafayette-West Lafayette, IN40115286790Ozone221,828169
Buffalo-Cheektowaga-Niagara Falls, NY40112273920Ozone1,130,152170
Des Moines-West Des Moines, IA40112284810Ozone655,409171
Owensboro, KY40112270870PM2.5119,114172
Columbia, MO40105208370Ozone180,005173
Gettysburg, PA40105294710Ozone102,811174
Columbia, SC40101279860Ozone832,666175
York-Hanover, PA40101268970Ozone448,273176
Bowling Green, KY40100280850PM2.5177,432177
Elizabethtown-Fort Knox, KY40100269920PM2.5153,378178
Hickory-Lenoir-Morganton, NC40100278870PM2.5368,416179
Columbus, GA-AL4099271940PM2.5305,451180
Clarksville, TN-KY4090289760Ozone292,264181
Jefferson City, MO4090210350Ozone151,520182
Lexington-Fayette, KY4090266990PM2.5516,697183
Greenville-Anderson-Mauldin, SC4087291740Ozone906,626184
Spartanburg, SC4077296690PM2.5341,298185
Napa, CA39183273838PM2.5139,417186
Lansing-East Lansing, MI39147296690Ozone481,893187
Hartford-West Hartford-East Hartford, CT39143286790Ozone1,206,300188
Janesville-Beloit, WI39133217290Ozone163,129189
Lima, OH39119304610Ozone102,663190
Portland-South Portland, ME39119311540Ozone535,420191
Laredo, TX39107237760PM2.5275,910192
Athens-Clarke County, GA39105262700PM2.5211,306193
Charleston, WV39105303620PM2.5211,037194
Fond du Lac, WI39101213310Ozone103,066195
Lebanon, PA391012601050Ozone141,314196
La Crosse-Onalaska, WI-MN3997300650Ozone136,808197
Wausau, WI3997205270Ozone135,428198
Hagerstown-Martinsburg, MD-WV3993285740Ozone268,049199
Pensacola-Ferry Pass-Brent, FL3993295700Ozone494,883200
Springfield, MO3993294710Ozone466,978201
Bellingham, WA381822481143SO2225,685202
Portland-Vancouver-Hillsboro, OR-WA38165279842Ozone2,478,810203
Salinas, CA38155319442Ozone435,594204
Traverse City, MI38154218311Ozone149,914205
Orlando-Kissimmee-Sanford, FL38151309551Ozone2,572,962206
Dover, DE38133310550Ozone178,550207
Altoona, PA38132296660Ozone122,492208
Worcester, MA-CT38129302630Ozone947,866209
Flint, MI38122291710Ozone406,892210
Albany-Schenectady-Troy, NY38119288770Ozone883,169211
North Port-Sarasota-Bradenton, FL38119300650Ozone821,573212
Rochester, NY38115296690Ozone1,071,082213
Elkhart-Goshen, IN38105285780Ozone205,560214
Mobile, AL38105290750PM2.5413,757215
Scranton--Wilkes-Barre--Hazleton, PA38101300650Ozone555,485216
Fayetteville, NC38100284650Ozone387,094217
Corpus Christi, TX3899284810PM2.5452,950218
Rochester, MN3898292690PM2.5219,802219
Tallahassee, FL3898272860PM2.5385,145220
Johnstown, PA3893297660Ozone131,730221
Vineland-Bridgeton, NJ3893305600PM2.5150,972222
Iowa City, IA3892287750PM2.5173,401223
Burlington-South Burlington, VT3889322430Ozone221,083224
Erie, PA3884280850Ozone272,061225
Savannah, GA3882303620PM2.5389,494226
Longview, TX37140290750Ozone219,417227
Blacksburg-Christiansburg-Radford, VA37139313490Ozone184,029228
Palm Bay-Melbourne-Titusville, FL37129330350Ozone596,849229
Panama City, FL37126273510Ozone201,451230
Hattiesburg, MS37119284750PM2.5149,414231
Sioux Falls, SD37115309560Ozone265,653232
Tuscaloosa, AL37115265550Ozone243,575233
Atlantic City-Hammonton, NJ37112327380Ozone265,429234
Port St. Lucie, FL37112328370Ozone482,040235
Dalton, GA37100241300Ozone143,983236
Decatur, AL37100304600PM2.5152,046237
Valdosta, GA3793264510PM2.5146,174238
Meridian, MS3787206310Ozone100,948239
Roanoke, VA3787318470Ozone314,172240
Santa Rosa, CA362263253010Ozone499,942241
Santa Cruz-Watsonville, CA36170331295Ozone274,255242
Michigan City-La Porte, IN36161305571Ozone110,007243
Eugene, OR36154266981PM2.5379,611244
Killeen-Temple, TX36136320450Ozone451,679245
Barnstable Town, MA36133338220Ozone213,413246
Torrington, CT36133319440Ozone181,111247
Jamestown-Dunkirk-Fredonia, NY36126311510Ozone127,939248
Syracuse, NY36115318470Ozone650,502249
Sebastian-Vero Beach, FL36101325310Ozone157,413250
Charleston-North Charleston, SC3697326330Ozone787,643251
Manchester-Nashua, NH3697338270Ozone415,247252
Virginia Beach-Norfolk-Newport News, VA-NC3697321440Ozone1,728,733253
Joplin, MO3695304610Ozone178,902254
Charlottesville, VA3693275350Ozone235,232255
Claremont-Lebanon, NH-VT3690336290Ozone217,215256
Houma-Thibodaux, LA3690314490Ozone209,136257
Florence, SC3687321420PM2.5204,961258
Deltona-Daytona Beach-Ormond Beach, FL3680329360Ozone659,605259
Naples-Immokalee-Marco Island, FL3680320450Ozone378,488260
Tupelo, MS3680226170Ozone140,552261
Rockford, IL35151316451Ozone337,658262
Norwich-New London, CT35140284310Ozone266,784263
Muncie, IN35129320410Ozone114,772264
Fargo, ND-MN35121315450Ozone245,471265
Lakeland-Winter Haven, FL35112324410Ozone708,009266
Duluth, MN-WI35109305600Ozone278,799267
East Stroudsburg, PA35108319360Ozone169,507268
Cape Coral-Fort Myers, FL35106316490Ozone754,610269
Macon, GA35106312530PM2.5229,737270
Texarkana, TX-AR35106246510PM2.5150,242271
Waco, TX3598268440Ozone271,942272
Daphne-Fairhope-Foley, AL3597245250Ozone218,022273
Florence-Muscle Shoals, AL3593251260Ozone147,149274
Fort Smith, AR-OK3590308550Ozone282,318275
Ocala, FL3590325400Ozone359,977276
Greenville, NC3587306390Ozone179,914277
Winchester, VA-WV3585309430Ozone139,810278
Dothan, AL3580249280Ozone148,245279
Jonesboro, AR357271190PM2.5132,532280
Kennewick-Richland, WA34178289742PM2.5296,224281
Eureka-Arcata-Fortuna, CA34163324401Ozone136,373282
Myrtle Beach-Conway-North Myrtle Beach, SC-NC34116314400Ozone480,891283
Warner Robins, GA34108259630PM2.5193,835284
St. Cloud, MN34101309560Ozone199,801285
Morgantown, WV3493311300Ozone140,259286
Utica-Rome, NY3493337270Ozone291,410287
Brunswick, GA3474255170Ozone118,456288
Pittsfield, MA33122284810PM2.5126,348289
Tyler, TX33112324400Ozone230,221290
Watertown-Fort Drum, NY33105307220Ozone111,755291
Ithaca, NY33101330340Ozone102,793292
Gainesville, FL3390335290Ozone288,212293
Crestview-Fort Walton Beach-Destin, FL3380325280Ozone278,644294
Rocky Mount, NC3380321330Ozone146,021295
Monroe, LA32100338250Ozone176,805296
Bangor, ME3297337280Ozone151,096297
Harrisonburg, VA3280339260Ozone135,277298
Chambersburg-Waynesboro, PA3274343100Ozone154,835299
Homosassa Springs, FL3271321380PM2.5147,929300
Salem, OR31125244270Ozone432,102301
Sebring, FL31108337140Ozone105,424302
Williamsport, PA3197327180Ozone113,664303
Alexandria, LA3191102170PM2.5153,044304
Lewiston-Auburn, ME3184336250Ozone107,679305
Lincoln, NE3178330350Ozone334,590306
Anchorage, AK30151293711PM2.5399,148307
Albany, GA30137292640PM2.5153,009308
Odessa, TX3091296410PM2.5162,124309
Augusta-Waterville, ME3090344160Ozone122,083310
Wilmington, NC3077308210Ozone294,436311
Urban Honolulu, HI307535870Ozone980,080312
Gainesville, GA3068282400PM2.5202,148313
Mount Vernon-Anacortes, WA29180341213Ozone128,206314
Twin Falls, ID29151319442PM2.5110,096315
Bay City, MI2883321350PM2.5103,923316
Hammond, LA2878110150PM2.5133,777317
Wenatchee, WA274262905817PM2.5119,943318
Billings, MT27154317461PM2.5171,677319
Concord, NH2787355100Ozone151,132320
Cookeville, TN2764319330PM2.5112,669321
Olympia-Tumwater, WA26173305335PM2.5286,419322
Jackson, TN2678321300PM2.5129,209323
Lynchburg, VA265510660PM2.5263,353324
Coeur d'Alene, ID25204272545PM2.5161,505325
Bozeman, MT25153323411PM2.5111,876326
Lubbock, TX25134275280PM2.5319,068327
Albany, OR24122243300PM2.5127,335328
Pueblo, CO2310111760PM2.5167,529329
Longview, WA20152338252PM2.5108,987330
Kahului-Wailuku-Lahaina, HI197335740PM2.5167,295331
Bend-Redmond, OR18189223435PM2.5191,996332
Roseburg, OR18135233130PM2.5110,283333
Lake Havasu City-Kingman, AZ18105350130PM10209,550334
Ogdensburg-Massena, NY14110282770SO2108,047335
Bremerton-Silverdale, WA12172333133PM2.5269,805336
Ottawa-Peru, IL16236020SO2148,163337
Monroe, MI15936410SO2150,439338
Salem, OH15230210SO2102,665339
College Station-Bryan, TX02633200SO2262,431340
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Frequently Asked Questions: Cleanest Cities vs Most Polluted

Now that we’ve covered the most polluted cities in America, let’s get to your frequently asked questions. They include:

  • What US city has the cleanest air?
  • Which US state is the most polluted?
  • What is the cleanest city in the world?

Scroll down for the answers to those questions and more.

#1 – Which US cities have the worst air quality?

Which city has the worst air quality? The five most polluted cities in our ranking are the Riverside-San Bernardino-Ontario metro, the Phoenix-Mesa-Scottsdale metro, the Los Angeles-Long Beach-Anaheim metro, the Denver-Aurora-Lakewood metro, and the San Diego-Carlsbad metro.

#2 – What US city has the cleanest air?

Wondering which city has the cleanest air? A 2019 American Lung Association report named Bangor, Maine as the US city with the cleanest air. It was one of just six cities that received that distinction.

#3 – Which US state is the most polluted?

California, which has five metros in our ranking of the most polluted cities in the United States, is considered the most polluted state throughout the country.

#4 – Which US state has the cleanest air?

According to the World Population Review, Hawaii is the state with the cleanest air with an air quality index of 21.2, well into the “good” air quality index range.

#5 – What is the cleanest city in the world?

The cleanest city in the world, according to the European organization Clearwater, is Calgary, which is a city that actually has over a million people. Other incredibly clean cities include Zurich (Switzerland) and Luxembourg (a country in Europe).

#6 – What country is the most polluted?

Wondering what is one of the most polluted places in the world? According to Statista, Bangladesh is considered the most polluted country in the world with an average PM2.5 concentration of 77.1 micrograms per cubic meter of air.

#7 – What country is the cleanest?

New Zealand is considered the country with the lowest amount of pollution, likely due to its coastal geography and the low-density towns that are located around that coast.

#8 – Is Los Angeles a dirty city?

While “dirty” is a term that resides in the eye of the beholder, Los Angeles and its metro certainly suffer from the major consequences of a highly populated and dense city.  While it’s not the dirtiest city in the world, it definitely isn’t the cleanest. Some of its issues include increased amounts of pollution along with less greenage, which can lead to more air quality issues.

Methodology: Determining the Most Polluted Cities in America

Statistics on annual levels of air pollutants by metropolitan area for 2018 were obtained from the U.S. Environmental Protection Agency. For each metro, the EPA calculates a daily index value for each pollutant.

The highest of those index values are reported as the daily Air Quality Index (AQI) value, and the pollutant responsible for the highest index value is considered the main pollutant for the day. For each metro, the median of the daily AQI values is reported as the overall measure of air quality for the year—the median AQI.

Additionally, for each metro, the pollutant listed as the main pollutant for the greatest number of days in the year is listed as the most common pollutant in that metro. PM10 and PM2.5 represent coarse and fine particulate matter, respectively.

To improve relevance, metropolitan areas were grouped into the following cohorts based on population size:

  • Large: 1,000,000 or more
  • Midsize: 350,000-999,999
  • Small: 100,000-349,999

Metros were ordered by their median AQI. In the event of a tie, both the maximum annual AQI and the number of unhealthy, very unhealthy, or hazardous days were considered.

Many of America’s most polluted metros are in California.

The rankings can be attributed to a few factors. First, California is the most populous U.S. state, which means more people are commuting, consuming, and ultimately polluting. Second, California is generally warm and sunny.

Ground-level ozone pollution is more likely to form in this type of climate as the sun and heat act as accelerants. California’s hot weather has also been linked to severe wildfires, which push more dangerous particles into the air.

Finally, many California cities exist on plains or in valleys that are encased by mountains. This topography helps trap pollutants in, keeping ambient air concentrations high.

Across the U.S., major sources of pollution vary by pollutant. For example, vehicles produce the largest share of carbon monoxide gas, while industrial processes and stationary fuel consumption (like power plants) are responsible for the majority of particulate matter and sulfur dioxide in the air.

Commonly, ground-level ozone pollution is caused by automobiles, power plants, chemical plants, refineries, and industrial boilers.

However, it can also be created through natural sources including trees. Prolonged exposure to this type of pollution can lead to numerous health problems, particularly those related to the lungs and respiratory system.

Air pollution in the U.S. has greatly improved since the passage of the Clean Air Act. Yet, millions of Americans continue to live in polluted cities where air pollution remains a threat.

To tackle this ongoing problem, the EPA and other federal, state, and local environmental agencies are implementing new policies and programs aimed at individuals and companies.

For example, the EPA SmartWay program helps companies identify more fuel-efficient ways to move goods. Similarly, cities and states across the nation are heavily investing in and promoting public transportation systems as a way to reduce air pollution and protect the environment.

Pollution can cause damage to your car, including upkeep. One way to save is to find the best rates on auto insurance. Just plug your ZIP code into our online quote generator to find the best auto insurance rates in your area based on your information.

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