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U.S. cities with the cleanest air

  • 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 (EPA) 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 24 hours.

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

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  • #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

    - 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

    - 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

    - 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

    - 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.

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  • #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

    - 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

    - 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)

    - 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)

    - 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.

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