Top 10 Most-Polluted U.S. Cities.

Via Lynn Hasselberger
on Apr 30, 2012
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Photo: Jim Corwin

Surprise, surprise:

Is the air you breathe hazardous to your health?

Now’s your chance to find out, thanks to The American Lung Association and their thirteenth annual State of the Air report. Before checking out the worst of the worst lists, breathe in the good and not-so-good news about our air.

The good news: The report finds that in America’s most polluted cities, air quality was at its cleanest since the organization’s annual report began 13 years ago. This year’s report details the trend that standards set under the Clean Air Act to cleanup major air pollution sources—including coal-fired power plants, diesel engines, and SUVs—are working to drastically cut ozone (smog) and particle pollution (soot) from the air we breathe. Despite this progress, unhealthy levels of air pollution still exist and in some parts of the country worsened.

State of the Air shows that we’re making real and steady progress in cutting dangerous pollution from the air we breathe,” said Charles D. Connor, American Lung Association President and CEO. “We owe this to the ongoing protection of the Clean Air Act. But despite these improvements, America’s air quality standards are woefully outdated, and unhealthy levels of air pollution still exist across the nation, putting the health of millions of Americans at stake.”

The not-so-good news: The job of cleaning the air is not finished. More than 40 percent of people in the United States live in areas where air pollution continues to threaten their health. That means more than 127 million people are living in counties with dangerous levels of either ozone or particle pollution that can cause wheezing and coughing, asthma attacks, heart attacks, and premature death. Those at greatest risk from air pollution include infants, children, older adults, anyone with lung diseases like asthma, people with heart disease or diabetes, people with low incomes and anyone who works or exercises outdoors.

10 Most Ozone-Polluted US Cities:

  1. Los Angeles-Long Beach-Riverside, Calif.

  2. Visalia-Porterville, Calif.

  3. Bakersfield-Delano, Calif.

  4. Fresno-Madera, Calif.

  5. Hanford-Corcoran, Calif.

  6. Sacramento-Arden-Arcade-Yuba City, Calif.-Nev.

  7. San Diego-Carlsbad-San Marcos, Calif.

  8. Houston-Baytown-Huntsville, Texas

  9. San Luis Obispo-Paso Robles, Calif.

  10. Merced, Calif.

Ozone (O3), an extremely reactive gas molecule, is the primary ingredient of smog air pollution. It attacks lung tissue by reacting chemically with it and is very harmful to breathe.

The ozone layer—found high in the upper atmosphere (the stratosphere)—shields us from much of the sun’s ultraviolet radiation. Ozone air pollution at ground level where we can breathe it (in the troposphere) is harmful.

State of the Air 2012 finds that nearly four out of 10 people in the U.S. live in counties that received an F for air quality because of unhealthy levels of ozone air pollution, which can cause health problems that day, and even days after. When inhaled, ozone irritates the lungs, like a bad sunburn, and can cause wheezing, coughing, asthma attacks and can shorten life.

11 Cities Most Polluted by Year-Round Particle Pollution (Annual PM2.5)

  1. Bakersfield-Delano, Calif.
  2. Hanford-Corcoran, Calif.
  3. Los Angeles-Long Beach-Riverside, Calif.
  4. Visalia-Porterville, Calif.
  5. Fresno-Madera, Calif.
  6. Pittsburgh-New Castle, Pa.
  7. Phoenix-Mesa-Glendale, Ariz.
  8. Cincinnati-Middletown-Wilmington, Ohio-Ky.-Ind.
  9. Louisville-Jefferson County-Elizabethtown-Scottsburg, Ky.-Ind.
  10. Philadelphia-Camden-Vineland, Pa.-N.J.-Del.-Md.
  11. St. Louis-St. Charles-Farmington, Mo.-Ill.

Particle pollution refers to a mix of very tiny solid and liquid particles that are in the air we breathe. Think the dirty, smoky part of dirty truck exhaust or soot.

The report finds that nearly 50 million Americans live in counties with too many unhealthy spikes in particle pollution levels, and nearly six million people live in areas with unhealthy year-round levels of particle pollution. Particle pollution is the most dangerous and deadly widespread air pollutant in America. This noxious mix of microscopic bits of ash, soot, diesel exhaust, chemicals, metals and aerosols can lead to early death, heart attacks, strokes and emergency room visits. Only eight counties received a failing grade for year-round particle pollution, further evidence of the continuing improvement even since last year’s report.

10 Cities Most Polluted by Short-Term Particle Pollution (24-hour PM2.5)

  1. Bakersfield-Delano, Calif.
  2. Fresno-Madera, Calif.
  3. Hanford-Corcoran, Calif.
  4. Los Angeles-Long Beach-Riverside, Calif.
  5. Modesto, Calif.
  6. Pittsburgh-New Castle, Pa.
  7. Salt Lake City-Ogden-Clearfield, UT
  8. Logan, UT-ID
  9. Fairbanks, Alaska
  10. Merced, Calif.

“We still need to fulfill the promise of clean, healthy air for everyone, and that can only become a reality through the full implementation of the Clean Air Act. The American Lung Association strongly opposes any efforts to weaken, delay, or undermine the protective standards the law provides,” said Connor.

Get more detailed information for your state by clicking here. Click here to get local up-to-date air quality reports and forecasts.

More air pollution facts from the American Lung Association:

More than four in 10 people (41 %) in the United States live in counties that have unhealthful levels of either ozone or particle pollution. Over 127.2 million Americans live in the 235 counties where they are exposed to unhealthful levels of air pollution in the form of either ozone or short-term or year-round levels of particles.

Over 5.7 million people (1.9%) in the United States live in six counties with unhealthful levels of all three: ozone and short-term and year-round particle pollution: ozone and short-term and year-round particle pollution.

The strongest improvement came in reducing ozone smog levels across the nation. More than half of the country’s most-smog-polluted cities experienced their best year yet. Twenty-two of the 25 cities with the most ozone pollution improved their air quality over the past year’s report. More than half of the country’s most smog-polluted cities experienced their best year yet. Still, nearly four in ten people in the U.S. (37.8%) live in areas with unhealthful levels of ozone pollution.

All but two cities with the most year-round particle pollution (sometimes called soot) improved over the previous report. Seventeen of those cities reported their best-ever particle pollution levels.

Success in reducing short-term particle pollution levels varied among metro areas. Thirteen of the most polluted cities saw improvement compared to last year’s report, while twelve had worse problems with these spikes in particle levels.

Make your voice count for clean air.

The Clean Air Act has been protecting us from dirty air for forty years and is under attack. Send a letter to your representatives by clicking here. It shouldn’t take you more than a minute or two to fill out the form and could save lives.

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About Lynn Hasselberger

Lynn Hasselberger is co-founder of GDGD Radio; The Green Divas Managing Editor; and Producer of The Green Divas Radio Show. She's also a mom, writer and award-winning cat-herder who lives in Chicagoland. Sunrises, running, yoga, lead-free chocolate and comedy are just a few of her fave things. In her rare moments of spare time, she blogs at and A treehugger and social media addict, you'll most likely find Lynn on twitter (@LynnHasselbrgr @GreenDivaLynn & @myEARTH360), instagram and facebook. She hopes to make the world a better place, have more fun, re-develop her math skills and overcome her fear of public speaking. Like her writing? Subscribe to her posts.


7 Responses to “Top 10 Most-Polluted U.S. Cities.”

  1. Bud Wilson says:

    Hello Lynn – Once again, you are skillfully bringing to our attention an inconvenient truth. Thanks for the link to the "Protect Your Air" petition. In my view, we need to strengthen the standards of the clean air act and hold every single polluter accountable. It is long past the time we "ecologize our economy". Thank you for being a vigilant observer, encouraging all of us to be responsible citizens!
    We know that Fracking activity is also a hazardous contributor to methane air pollution in addition to the toxins that poison ground water – here is a bill introduced in Colorado that could set a trend nationwide to put a check on the feeding frenzy our oil and gas companies are pursuing.

  2. Thanks, Bud. I certainly hope the safe fracking bill passes. Thanks for the link!

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  4. Jill Barth says:

    Bud and Lynn — Great reminders. Thanks for sharing.

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