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U.S. cities with the cleanest air

U.S. cities with the cleanest air
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U.S. cities with the cleanest air

The quality of air inhaled isn't something Americans consciously think about every day, but research from the World Health Organization reveals that 92% of the global population lives in places with unhealthy air quality.

Air pollution can come from transportation, coal-fired power plants, industrial activity, and other human-perpetuated activity as well as natural events like dust storms and wildfires. These invisible pollutants in the air can create smog and acid rain and can lead to serious health problems. Air pollution causes about one in eight deaths worldwide and accounts for many instances of chronic respiratory disease, lung cancer, strokes, and heart attacks. Ozone, which is the main ingredient in smog, can also increase the risk of asthma.

But it's not all bad news. Since the United States enacted the Clean Air Act in 1970, aggregate emissions of the six most common pollutants have dropped by 73%. Between 2000 and 2015, concentrations of contaminants in the U.S. have fallen 40% for fine particle concentrations over 24 hours and 34% for coarse particle concentration. The Clean Air Act also set new emissions standards for cars and trucks, improving the carbon monoxide levels in the air.

The U.S. Environmental Protection Agency collects air quality data for all 193 cities in the country and compiles the results into an annual report. Using data from EPA's 2018 Outdoor Air Quality report, Stacker determined 50 U.S. cities with the cleanest air.

Stacker ranked the top 50 cities by the annual average amount of coarse particulate matter or particles between 2.5 and 10 micrometers in 2018. Particulate matter between 2.5 and 10 micrometers, referred to as "PM10" is considered coarse, and cities with lower average amounts of PM10 have cleaner air.

In the event of a tie, Stacker used the second-highest coarse particulate matter recorded in a city in a 24-hour period in 2018 to exclude unusually low or high outliers. It's important to note that the annual mean amounts of fine inhalable particles smaller than 2.5 micrometers, referred to as PM2.5, were included in the slide data but were not factored into city rankings. Exceptional events data—such as wildfires—was excluded so that rankings would be determined by the typical air quality in each city, and not by unusual events and outliers.

The EPA's National Ambient Air Quality Standards referenced in this piece are 150 ug/m3 for coarse particulate matter (PM10) and 12 ug/m3 for fine particulate matter (PM2.5) over a 24-hour period.

Read on to find out the top 50 U.S. cities that boast the cleanest air.

You may also like: States with the costliest weather events

#50. Weirton-Steubenville, WV-OH
2/Roseohioresident // Wikimedia Commons

#50. Weirton-Steubenville, WV-OH

- Average coarse particulate matter (PM10) in 2018: 15 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 46 ug/m3 (69% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.8 ug/m3 (27% below EPA standard)

The Steubenville, Ohio, area was once home to a steel mill that caused a significant amount of pollution in the region, and a 1993 Harvard University study of six cities ranked Steubenville as having the highest particulate levels and worst air quality. Since then, the steel mill has closed, and Ohio power plants have installed scrubbers to cut back on smokestack emissions, which has drastically improved the area's air quality.

#49. Nashville-Davidson-Murfreesboro-Franklin, TN
3/Unsplash

#49. Nashville-Davidson-Murfreesboro-Franklin, TN

- Average coarse particulate matter (PM10) in 2018: 15 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 41 ug/m3 (73% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.2 ug/m3 (23% below EPA standard)

The state of Tennessee has a Division of Air Pollution Control that serves 91 counties within the state, while Davidson, Hamilton, Knox, and Shelby counties also have local enforcement teams that work to control air pollution. The Tennessee Air Pollution Control Board will also bring cases to court to bolster existing regulations to ensure clean air, while also maintaining the upkeep and surveillance of air sampling stations that study pollution.

#48. Deltona-Daytona Beach-Ormond Beach, FL
4/Pixabay

#48. Deltona-Daytona Beach-Ormond Beach, FL

- Average coarse particulate matter (PM10) in 2018: 15 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 34 ug/m3 (77% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.2 ug/m3 (40% below EPA standard)

A 2018 report found that air quality had improved in the state of Florida compared to the previous year and that the Sunshine State had experienced a reduction in ozone pollution. Deltona and Daytona Beach were ranked among the cleanest Florida cities for short-term particle pollution in 2018, experiencing no unhealthy air quality days. Both cities also had some of the lowest year-round particle pollution compared to neighboring areas.

#47. Huntsville, AL
5/Pixabay

#47. Huntsville, AL

- Average coarse particulate matter (PM10) in 2018: 15 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 33 ug/m3 (78% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.4 ug/m3 (38% below EPA standard)

The measured ozone concentrations in Huntsville, Ala., are below the national standard and have declined steadily in the last 40 years. Additionally, particulate concentrations in the Huntsville ambient air have also decreased in the past 27 years. Levels of deadly carbon monoxide in the city's atmosphere have also declined in the last 26 years.

#46. Walla Walla, WA
6/Danita Delmont // Shutterstock

#46. Walla Walla, WA

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 186 ug/m3 (24% above EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

The Clean Air Washington Act of 1991 helped set new statewide standards for air quality throughout the state, with far-reaching impacts. The law implemented stronger vehicle emissions testing, prohibited transportation funds from being used on projects that were forecast to worsen air quality, and required that 30% of vehicles purchased by the state be powered using alternative fuels. The legislation also phased out outdoor burning and banned it entirely in places that did not meet federal clean air standards.

#45. Ukiah, CA
7/Ian Poellet // Wikimedia Commons

#45. Ukiah, CA

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 59 ug/m3 (61% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.5 ug/m3 (38% below EPA standard)

While the air quality in Ukiah, Calif., is normally cleaner than most cities in the country, the devastating Camp Fire in 2018 sent the Air Quality Index in the region soaring to unhealthy levels, bringing an unusual amount of pollution to the area. Scientists determined that during the peak of the wildfire, breathing the air in Ukiah for just one day was the equivalent of smoking 13 and a half cigarettes.

#44. Crestview-Fort Walton Beach-Destin, FL
8/Unsplash

#44. Crestview-Fort Walton Beach-Destin, FL

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 54 ug/m3 (64% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

Crestview, Fort Walton Beach, and Destin are tied first for the cleanest metropolitan areas in the country for ozone, with practically no high particle days per year and almost no high ozone days. Just 5% of the adult population in Walton County report having asthma, while less than 2% of people have pediatric asthma.

#43. Bangor, ME
9/Pixabay

#43. Bangor, ME

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 43 ug/m3 (71% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5.2 ug/m3 (57% below EPA standard)

Bangor, Maine, was ranked as one of the cleanest cities in 2019 in terms of the country's most widespread air pollutants and was deemed one of only six cities nationwide as a “Cleanest City” in an American Lung Association report. But the rest of Maine fared worse, with the report finding that four other counties in Maine are experiencing more bad ozone days compared to the previous year.

#41. New Haven-Milford, CT (tie)
10/GoodFreePhotos

#41. New Haven-Milford, CT (tie)

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 38 ug/m3 (75% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.5 ug/m3 (29% below EPA standard)

Between 2007 and 2017, the pounds of discharged air pollution in New Haven, Conn., decreased by 21%, reflecting a larger trend of reduced air pollution in Connecticut and New England over the past decade. The state of Connecticut in the past has even sued the federal Environmental Protection Agency for failing to enforce pollution regulations on Midwestern factories, claiming that prevailing winds drift pollution from those states to Connecticut.

#41. Lancaster, PA (tie)
11/Pixabay

#41. Lancaster, PA (tie)

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 38 ug/m3 (75% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.5 ug/m3 (21% below EPA standard)

The air quality in Lancaster, Pa., is slowly improving, with a decreased amount of ozone pollution in 2017. The amount of soot in the air also fell for the third year in a row in 2017. Lancaster County—which historically has suffered from poor air quality—received a passing grade for the first time in 18 years in 2017 for smog pollution in an American Lung Association report.

#40. Buffalo-Cheektowaga-Niagara Falls, NY
12/Unsplash

#40. Buffalo-Cheektowaga-Niagara Falls, NY

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 35 ug/m3 (77% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.6 ug/m3 (37% below EPA standard)

Buffalo, N.Y., air quality is on the rise and has experienced reduced drops in smog and nitrogen dioxide, which can irritate asthma, in the last decade. From 2007 to 2009, however, air pollution was at an all-time high in the city. The average air monitor nitrogen dioxide reading for Buffalo during those two years measured 16 to 22% higher than levels in New York City, making it the highest in the country.

#39. Bridgeport-Stamford-Norwalk, CT
13/Pixabay

#39. Bridgeport-Stamford-Norwalk, CT

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 34 ug/m3 (77% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.9 ug/m3 (34% below EPA standard)

From 2007 to 2017, the pounds of air pollution released in Bridgeport, Conn., decreased by a whopping 90%, while Stamford, Conn., experienced a similarly impressive 68% decline. The state has taken efforts to combat air pollution, including updating wastewater plants and putting scrubbers on smokestacks.

#38. Baltimore-Columbia-Towson, MD
14/Joe Haupt // Flickr

#38. Baltimore-Columbia-Towson, MD

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 33 ug/m3 (78% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.6 ug/m3 (20% below EPA standard)

Although Baltimore City and Baltimore County have work to do on reducing smog, the city was given a ‘B' grade for the amount of soot in the air, while the county was given an ‘A' grade. However, Baltimore fared worse in terms of ozone, landing the #17 spot among cities with the highest ozone days. In Howard County, which is home to Columbia, Md., the soot grade was also an ‘A.'

#35. Urban Honolulu, HI (tie)
15/Pixabay

#35. Urban Honolulu, HI (tie)

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 31 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 4.3 ug/m3 (64% below EPA standard)

Honolulu is tied for first place for the cleanest metropolitan areas in the United States for ozone and the cleanest metropolitan areas for 24-hour particle pollution, even though ozone pollution is significantly more likely to occur in places with warmer temperatures. The city also came in second for year-round particle pollution, trailing only Cheyenne, Wyo.

#35. Charleston-North Charleston, SC (tie)
16/James Willamor // Flickr

#35. Charleston-North Charleston, SC (tie)

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 31 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.8 ug/m3 (43% below EPA standard)

The Charleston, S.C., metropolitan area experienced no unhealthy ozone days in 2017 and less than one day of unhealthy particle pollution levels. 2017 marked one of the lowest levels in years for recorded ozone and particle pollution in the city. But Charleston's geography may have worked to its advantage in keeping the air pristine—the city's spot on the coastline means sea breezes can “sweep” coastal air, making it cleaner than landlocked regions.

#35. Casper, WY (tie)
17/Unsplash

#35. Casper, WY (tie)

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 31 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6 ug/m3 (50% below EPA standard)

Casper, Wyo., is home to the least amount of short-term particle pollution in the country and has also scored high marks for its lack of ozone pollution and year-round particle pollution. The state of Wyoming has long been recognized as the best in the United States for air quality and low levels of pollution overall.

#34. Grand Rapids-Wyoming, MI
18/Matthew Saul // Pexels

#34. Grand Rapids-Wyoming, MI

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 30 ug/m3 (80% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.9 ug/m3 (26% below EPA standard)

Grand Rapids is home to the West Michigan Clean Air Coalition, which declares a “Clean Air Action Day” when air pollutants reach a higher-than-normal level that could affect those with sensitivities. On a Clean Air Action Day, residents are asked to reduce their emissions by carpooling, taking public transportation, and delaying refueling or mowing lawns to improve the region's air quality.

#33. Raleigh, NC
19/Unsplash

#33. Raleigh, NC

- Average coarse particulate matter (PM10) in 2018: 14 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 28 ug/m3 (81% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.1 ug/m3 (33% below EPA standard)

In 2018, Raleigh, N.C., experienced a reduction in year-round particle pollution, but the city did see some spikes in short-term particle pollution throughout the year. Year-round particle pollution has largely decreased as diesel engines get replaced and coal-fired power plants evolve and clean up.

#32. Sioux Falls, SD
20/Sopotnicki // Shutterstock

#32. Sioux Falls, SD

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 58 ug/m3 (61% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.6 ug/m3 (37% below EPA standard)

Despite many power plants in South Dakota still burning coal, the state has been applauded for its clean air, and Sioux Falls is notable in particular for its minimal levels of ozone pollution. One reason for South Dakota's pristine air quality is its use of wind energy, placing #2 in the country in its production of net electricity generated by wind. Power plants within the state have also moved toward using alternative fuel instead of nonrenewable resources.

#31. Cheyenne, WY
21/Michel Rathwell // Flickr

#31. Cheyenne, WY

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 44 ug/m3 (71% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 4.9 ug/m3 (59% below EPA standard)

Cheyenne, Wyo., has been ranked as one of the cleanest cities in the nation for both ozone pollution and year-round particle pollution. In 2019, the city experienced only one day with high levels of ozone pollution, despite ozone levels shooting up across the country as global temperatures rise.

#30. Jackson, WY-ID
22/Unsplash

#30. Jackson, WY-ID

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 41 ug/m3 (73% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 3.7 ug/m3 (69% below EPA standard)

Jackson, Wyo., has taken several steps in recent years to monitor its air quality as separate from neighboring areas. Before 2011, air quality data for Jackson came from as far as Yellowstone and Pinedale, Wyo. But in 2011, Grand Teton National Park installed an air quality monitoring station to collect data and provide information about levels of ozone, sulfur dioxide, fine particles, and other pollutants.

#29. Harrisburg-Carlisle, PA
23/Rina Pitucci // Flickr

#29. Harrisburg-Carlisle, PA

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 35 ug/m3 (77% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.7 ug/m3 (19% below EPA standard)

Carlisle, Pa., established a Clean Air Board in 2005 to assess and improve the air quality of the greater Cumberland Valley area. The board has taken on several projects, including preventing school bus idling to enhance the quality of air and passing a state law to regulate truck idling. The group has also enlisted many schools to raise air quality flags with the American and state flags daily to alert community members of air pollution.

#28. Augusta-Richmond County, GA-SC
24/Sean Pavone // Shutterstock

#28. Augusta-Richmond County, GA-SC

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 33 ug/m3 (78% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.9 ug/m3 (18% below EPA standard)

From 2015 to 2017, Augusta, Ga., recorded zero high ozone pollution days and only a handful of elevated fine particle pollution days—thanks to heightened regulations at power plants and more fuel-efficient vehicles on the road. The air quality in the region is only expected to improve, as Georgia Power has requested to shut down two coal-fired power plants.

#27. Winston-Salem, NC
25/Kevin Ruck // Shutterstock

#27. Winston-Salem, NC

- Average coarse particulate matter (PM10) in 2018: 13 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 30 ug/m3 (80% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 9.3 ug/m3 (23% below EPA standard)

In 2017, reports showed that Winston-Salem, N.C., and neighboring areas of Greensboro and High Point had significantly cut back on ozone pollution, and the city was one of the cleanest areas for short-term particle pollution. In Winston-Salem, air quality has drastically improved since scrubbers were installed at a steam station to remove dust particles from smokestacks, and other nearby plants have started using natural gas.

#26. Farmington, NM
26/Eric Strand // Shutterstock

#26. Farmington, NM

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 84 ug/m3 (44% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

Farmington, N.M., has some of the cleanest air in the country in terms of particle pollution, tying with Cheyenne, Wyo., for first place in 2017 for soot-free air, but earning less than satisfactory grades on ozone pollution. However, Farmington still has a long way to go when it comes to monitoring air quality. The city only has one air quality monitoring station, which only collects data every 12 days.

#25. Clearlake, CA
27/Eden Vieira // Shutterstock

#25. Clearlake, CA

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 44 ug/m3 (71% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5 ug/m3 (58% below EPA standard)

Lake County, Calif., which is home to the city of Clearlake, has been rated as one of the top places in the country for its lack of fine particle pollution but has exceeded federal ozone standards due to wildfires. The county has bested all other locales in California in air quality for at least 24 years.

#24. Beaver Dam, WI
28/V-ron // Shutterstock

#24. Beaver Dam, WI

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 38 ug/m3 (75% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.5 ug/m3 (38% below EPA standard)

A clean energy center outside Portage, Wis.—a neighboring town of Beaver Dam—opened in 2018, and has cut nitrogen emissions in half by installing a selective catalytic reduction system in the boilers of a power plant. The technology removed nitrogen from the plant's exhaust, improving air quality and reducing the effect on Wisconsinites' respiratory health.

#23. Scranton-Wilkes-Barre-Hazleton, PA
29/Ashton Zanecki // Wikimedia Commons

#23. Scranton-Wilkes-Barre-Hazleton, PA

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 32 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

The Pennsylvania towns of Scranton, Wilkes-Barre, and Hazleton in 2018 made the American Lung Association's Cleanest Cities list for the third year in a row, measuring minimal amounts of short-term particle pollution. While the cities experienced no days with high levels of particle pollution, the region suffered from elevated levels of ozone pollution and had poorer ozone pollution compared to the previous year.

#22. Durham-Chapel Hill, NC
30/Unsplash

#22. Durham-Chapel Hill, NC

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 29 ug/m3 (81% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.9 ug/m3 (26% below EPA standard)

Durham and Chapel Hill, N.C., both experienced lower rates of year-round particle pollution in 2018, but fared somewhat worse in terms of short-term particle pollution, possibly because of wildfire smoke drifting in from the western part of the state. Both cities also experienced more unhealthy ozone days in 2018 compared to 2017.

#21. Richmond, VA
31/Ron Cogswell // Flickr

#21. Richmond, VA

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 28 ug/m3 (81% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.1 ug/m3 (33% below EPA standard)

Reductions of coal-powered plants and vehicles running on cleaner energy have contributed to Richmond's rise in air quality. The city measured low amounts of daily fine particles in the air in 2016 and also cut down on year-round fine air particulate pollution. Smog has also waned in the metropolitan Richmond area, but the city still has work to do curbing unhealthy levels of ozone.

#17. Portland-Vancouver-Hillsboro, OR-WA (tie)
32/GoodFreePhotos

#17. Portland-Vancouver-Hillsboro, OR-WA (tie)

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 27 ug/m3 (82% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.1 ug/m3 (33% below EPA standard)

The air pollution in Portland, Ore., experienced significant improvements since the 1980s and 1990s when measurements on the Air Quality Index indicated that the city's pollution was inching toward a dangerous level. Oregon has installed six air-testing stations to measure harmful pollutants.

#17. Orlando-Kissimmee-Sanford, FL (tie)
33/Pixabay

#17. Orlando-Kissimmee-Sanford, FL (tie)

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 27 ug/m3 (82% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.8 ug/m3 (43% below EPA standard)

Orlando, Fla., has been named as one of the cleanest cities in the United States for short-term particle pollution, but every locale in Florida is in danger of air pollution as global temperatures rise and the Sunshine State's warm climate gets even hotter. Orlando has also experienced an increase in days with unhealthy levels of ozone pollution.

#17. Lewiston-Auburn, ME (tie)
34/Paul VanDerWerf // Flickr

#17. Lewiston-Auburn, ME (tie)

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 27 ug/m3 (82% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5.2 ug/m3 (57% below EPA standard)

The region from South Portland to Lewiston, Maine, has some of the lowest daily particle pollution in the state, according to data from 2018, and the state overall has relatively few days with unhealthy levels of ozone pollution. However, despite Lewiston's low levels of particle pollution, the city did not crack the country's top 25 cities with the least measured daily short-term particle pollution.

#17. Salem, OH (tie)
35/Nyttend // Wikimedia Commons

#17. Salem, OH (tie)

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 26 ug/m3 (83% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

The air quality in Ohio has dramatically improved in recent years, with 2019 marking the first time Cleveland and Cincinnati received high marks for their low levels of year-round particle pollution as well as short-term particle pollution. However, the Akron area—of which Salem, Ohio, is a suburb—experienced more days of elevated ozone pollution this year compared to 2018.

#16. Palm Bay-Melbourne-Titusville, FL
36/crossfirecw // Flickr

#16. Palm Bay-Melbourne-Titusville, FL

- Average coarse particulate matter (PM10) in 2018: 12 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 26 ug/m3 (83% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5.4 ug/m3 (55% below EPA standard)

The Florida region encompassing the towns of Palm Bay, Melbourne, and Titusville went from 11.5 days of unhealthy levels of ozone pollution in 1996 to zero days in 2018, while the number of days with unhealthy levels of particle pollution fell from 0.3 days to zero days since 2003. Traffic jams in Brevard County have exacerbated some air pollution in the locale, and some have suggested implementing modernized systems to improve traffic flow and alleviate idling.

#15. Evanston, WY
37/Publichall // Wikimedia Commons

#15. Evanston, WY

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 67 ug/m3 (55% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

To combat EPA rolling back some federal pollution regulations, Wyoming state regulators proposed in 2018 to implement rules that would reduce methane emissions from infrastructure within the state and levy additional requirements in the Upper Green River Basin, which was once heavily polluted. The region had a spike in gas development when natural gas deposits were discovered, and its bowl-shaped geography exacerbated air pollution.

#14. Williston, ND
38/Andrew Filer // Flickr

#14. Williston, ND

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 51 ug/m3 (66% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.1 ug/m3 (49% below EPA standard)

While Williston, N.D., annually received high marks for its clean air, wildfires in the western part of the United States brought smoky and hazy air into the city, and with it, particle pollution. However, Williams County, where Williston is located, had little to no ozone pollution in 2018. North Dakota's clean air is primarily because of constant wind presence in the state, which ushers out dirty air and brings in clean air.

#13. Allentown-Bethlehem-Easton, PA-NJ
39/Ritu Manoj Jethani // Shutterstock

#13. Allentown-Bethlehem-Easton, PA-NJ

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 40 ug/m3 (73% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8 ug/m3 (33% below EPA standard)

The air in Pennsylvania's Lehigh Valley is gradually becoming cleaner. Allentown, Pa., and its surrounding areas in 2017 measured its lowest-ever ozone levels as well as daily and yearly average particle pollution. Officials say the area's geography and emission sources hinder more drastic improvements in air quality.

#12. Erie, PA
40/Pubdog // Wikimedia Commons

#12. Erie, PA

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 32 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: Data not available

Pennsylvania's Erie County achieved its best-ever results for daily and yearly particle pollution as well as ozone pollution in 2017 and has been able to maintain those results since. In 2018, the locale had zero days of unhealthy air quality. The annual particle pollution measured in 2017 showed a modest decline from 2014 to 2016 data collected in Erie County.

#11. Rochester, NY
41/Patrick Ashley // Wikimedia Commons

#11. Rochester, NY

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 31 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.3 ug/m3 (39% below EPA standard)

Rochester, N.Y., has worked to reduce air pollutants from the stacks of coal-burning power plants and other stationary sources and has put more cars with cleaner tailpipe emissions on the road, which have contributed significantly to improvements in air quality. From 2001 to 2003, Rochester experienced about 18.5 days per year with elevated ozone levels, while between 2013 to 2015, the city had just one day with higher-than-normal ozone pollution.

#9. Providence-Warwick, RI-MA (tie)
42/Sean Pavone // Shutterstock

#9. Providence-Warwick, RI-MA (tie)

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 23 ug/m3 (85% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 8.9 ug/m3 (26% below EPA standard)

The whole of New England no longer relies on coal-fired power plants and instead harvests its electricity from hydropower and wind power, improving the region's air quality. While Providence County has received poor ratings for its ozone pollution, the locale performed better with the presence of short-term and annual particle pollution.

#9. Portsmouth, OH (tie)
43/Spongefan // Wikimedia Commons

#9. Portsmouth, OH (tie)

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 23 ug/m3 (85% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7 ug/m3 (42% below EPA standard)

Portsmouth, Ohio, is home to the Portsmouth Local Air Agency, which enforces state and federal air pollution control regulations. Not only does the group monitor the air quality at five monitoring stations, but it also reviews facility compliance, conducts inspections, and responds to complaints from residents about air quality.

#8. Virginia Beach-Norfolk-Newport News, VA-NC
44/gargola87 // Wikimedia Commons

#8. Virginia Beach-Norfolk-Newport News, VA-NC

- Average coarse particulate matter (PM10) in 2018: 11 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 21 ug/m3 (86% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.6 ug/m3 (45% below EPA standard)

In 2018, the Virginia Beach and Norfolk area landed on the American Lung Association's list of cleanest U.S. cities in terms of daily fine particle pollution for the third year in a row. The air quality in the region even improved compared to previous years. 2018 also marked the eighth year that the locale met national standards for air pollution, even though the Virginia Beach area still sometimes struggles with ozone pollution levels.

#7. Baraboo, WI
45/Pixabay

#7. Baraboo, WI

- Average coarse particulate matter (PM10) in 2018: 10 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 32 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.6 ug/m3 (45% below EPA standard)

While former Wisconsin Governor Scott Walker spent his tenure at the helm of the state curbing environmental regulations, his successor, Democratic Governor Tony Evers, has spent the first year of his administration working to enforce pollution standards. In April, the state withdrew from a lawsuit that challenged an Environmental Protection Agency rule governing the emissions of hazardous air pollutants from power plants. The effort is one of many of Evers' efforts to reinstate air quality regulations hoping to up the state's clean air.

#6. Augusta-Waterville, ME
46/Sean Pavone // Shutterstock

#6. Augusta-Waterville, ME

- Average coarse particulate matter (PM10) in 2018: 10 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 28 ug/m3 (81% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5.2 ug/m3 (57% below EPA standard)

South Portland, Maine—just an hour from the state's capital of Augusta—debuted an air quality monitoring program in June using data collected in Augusta. The air quality samples, which will be collected by residents, are set to be examined by Maine's toxicologist for pollution and potential health concerns. Lawmakers in Maine have also introduced legislation to alert towns of emissions violations and require independent emissions tests.

#5. Hartford-West Hartford-East Hartford, CT
47/Pixabay

#5. Hartford-West Hartford-East Hartford, CT

- Average coarse particulate matter (PM10) in 2018: 10 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 24 ug/m3 (84% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.2 ug/m3 (40% below EPA standard)

Air pollution in Connecticut has dropped significantly in the last decade, according to the Environmental Protection Agency. Between 2007 and 2017, land, water, and air pollution in Connecticut dropped by a whopping 57%. The drop in pollution levels is partly due to industrial facilities implementing 4,000 new pollution source reduction activities that have limited chemical waste.

#4. Winchester, VA-WV
48/Jon Bilous // Shutterstock

#4. Winchester, VA-WV

- Average coarse particulate matter (PM10) in 2018: 10 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 20 ug/m3 (87% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 7.2 ug/m3 (40% below EPA standard)

While Winchester has pristine air quality now, residents are concerned that the Trump administration's Affordable Clean Energy Rule, which replaces an Obama administration plan, would dirty the air and disproportionately affect the Shenandoah Valley as opposed to the rest of the country. In fact, under the new policy, there would be an increase of between 0.43 and 0.85 deaths per 100,000 residents in the Shenandoah Valley, according to the EPA.

#3. Minot, ND
49/Bobak Ha'Eri // Wikimedia Commons

#3. Minot, ND

- Average coarse particulate matter (PM10) in 2018: 9 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 56 ug/m3 (63% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 5.7 ug/m3 (53% below EPA standard)

North Dakota's windy weather and open spaces without obstruction from high elevation have long served the state's air quality, resulting in a consistent “cleaning” of air pollutants from the state's air. Still, some officials in North Dakota are worried that the presence of power plants and oil and gas emissions is still adversely affecting the state, despite stellar air quality reports. Currently, the state is seeking funding for an additional air quality monitoring station to better review pollution data.

#2. Boston-Cambridge-Newton, MA-NH
50/Unsplash

#2. Boston-Cambridge-Newton, MA-NH

- Average coarse particulate matter (PM10) in 2018: 9 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 31 ug/m3 (79% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 10.1 ug/m3 (16% below EPA standard)

In 2018, the Boston area recorded some of its lowest pollution levels on record, improving in both measures of particle pollution and ozone pollution. Counties in the greater Boston area, including Bristol, Essex, and Suffolk, also cut pollution levels, and only one county in all of Massachusetts saw an increase in ozone levels. The state's improvement in air quality was in contrast to a national trend that saw an average rise in ozone levels nationwide.

#1. Burlington-South Burlington, VT
51/Erika J. Mitchell // Shutterstock

#1. Burlington-South Burlington, VT

- Average coarse particulate matter (PM10) in 2018: 6 ug/m3
- Second-highest average coarse particulate matter (PM10) over a 24-hour period: 20 ug/m3 (87% below EPA standard)
- Average fine particulate matter (PM2.5) in 2018: 6.5 ug/m3 (46% below EPA standard)

Year after year, Vermont is considered one of the cleanest places in the United States for air quality, but the Burlington area has consistently outshone other cities with its sparkling clean air. In 2019, Burlington was one of only six cities in the country to record zero days of unhealthy ozone levels as well as short-term pollution. Year-round particle pollution also decreased in 2019 compared to the year before.

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