What Is Year-round Particle Pollution?

Particle pollution is a mix of very tiny solid and liquid particles in the air. "Year-Round" refers to an annual average level that represents the concentration of particles day-in-and-day-out.

Fresno-Madera-Hanford, CA returned to the rank of most polluted by year-round particle pollution in 2015-2017. This metro area now officially includes Kings County, the county with the highest year-round levels of particle pollution in the nation. This ties the highest year-round levels ever for Kings County, and for the metro area.

Fourteen of the 25 cities most polluted year-round by particle pollution improved over the levels in the 2018 report. Bakersfield, Visalia, CA, and El Centro, CA, continued to improve as they had in the 2018 report. Last year's most-polluted city, Fairbanks, AK, dropped back to #3. Ten reached their lowest annual level ever: Cleveland; Detroit; Birmingham; Lancaster, PA; Houston, TX, Philadelphia; Chicago; Indianapolis; Harrisburg, PA; and Knoxville, TN. This is Chicago's first year back with complete data on particle pollution in Illinois.

Six others improved over the 2017 report: Visalia-Porterfield-Hanford, CA; Bakersfield, CA; El Centro, CA; San Jose-San Francisco; San Luis Obispo, CA; and Atlanta.

Fairbanks, AK, moved to the most-polluted city for the first time. Previously ranked as #17 most polluted, Fairbanks' improved monitoring in the borough now identifies that this problem is more severe than previously known. Six other cities in the 25 most polluted had higher particle levels year-round: Los Angeles; Pittsburgh; Lancaster, PA; Birmingham, AL; Harrisburg-York-Lebanon, PA; and Las Vegas.

Fourteen of the 25 cities with the highest year-round particle levels experienced lower levels in the 2019 report.

Eleven of the 25 cities suffered worse year-round levels. Two, Fresno-Madera-Hanford, CA and Missoula, MT, tied their worst annual average levels of particle pollution. Others that had higher levels were Los Angeles; San Jose-San Francisco; Pittsburgh; Medford-Grants Pass, OR; Cincinnati; Johnstown-Somerset, PA; Atlanta; McAllen-Edinburg, TX; and Shreveport, LA.

All the cities below the seven most polluted meet the current national air quality standards. Often annual levels vary in cities once they clean up enough to meet that standard. However, evidence shows that no threshold exists for harmful effects from particle pollution, even below the official standard.

California continues to dominate this list, with six of the 10 most-polluted, and five of the seven cities that fail to meet the annual standard. Pennsylvania has five cities on this list, although only Pittsburgh fails to meet the standard. Other areas with several cities on the list include the Midwest with five cities; Southeast with four cities; the Northwest with three cities; and Texas with two.

For San Jose-San Francisco, the higher levels came in the two counties added to the metro area by the Office of Management and Budget. Both had been part of the former Merced-Modesto, CA MSA. They were incorporated into the larger CSA because of increased integration with the larger metro area.

Cities with high power plant emissions as well as local, industrial sources continue to show up on the list. That list includes Pittsburgh; Philadelphia; Detroit; Cincinnati; Cleveland; Chicago; Birmingham; Atlanta; Indianapolis; Youngstown; and Shreveport, LA.

Fortunately, year-round particle pollution continues to decline across most of the nation, unlike the days with high ozone and high short-term particle pollutions.

Because of the high numbers and long duration, the western wildfires contributed to some of the elevated annual averages in western cities. That is especially true in Missoula, MT, Medford-Grants Pass, OR, and likely in Los Angeles as well.

Did You Know?

  1. Nearly 5 out of 10 people live where the air they breathe earned an F in State of the Air 2020.
  2. 150 million people live in counties that received an F for either ozone or particle pollution in State of the Air 2020.
  3. More than 20.8 million people live in counties that got an F for all three air pollution measures in State of the Air 2020.
  4. Breathing ozone irritates the lungs, resulting in something like a bad sunburn within the lungs.
  5. Breathing in particle pollution can increase the risk of lung cancer, according to the World Health Organization.
  6. Particle pollution can also cause early death and heart attacks, strokes and emergency room visits for people with asthma and cardiovascular disease.
  7. Particles are smaller than 1/30th the diameter of a human hair. When you inhale them, they are small enough to get past the body's natural defenses.
  8. Ozone and particle pollution are both linked to increased risk of lower birth weight in newborns.
  9. Do you live near, or work on or near a busy highway? Pollution from the traffic may put you at greater risk of harm.
  10. People who work or exercise outside face increased risk from the effects of air pollution.
  11. Millions of people are especially vulnerable to the effects of air pollution, including infants, older adults and people with lung diseases like asthma.
  12. People of color and those earning lower incomes are often disproportionately affected by air pollution that put them at higher risk for illnesses.
  13. Air pollution is a serious health threat. It can trigger asthma attacks, harm lung development in children, and can even be deadly.
  14. You can protect your family by checking the air quality forecasts in your community and avoiding exercising or working outdoors when the unhealthy air is expected.
  15. Climate change enhances conditions for ozone to form and makes it harder to keep ozone from forming.
  16. Climate change increases the risk of wildfires that spread particle pollution and ozone in the smoke.
  17. This Administration is trying to roll back or create loopholes in core healthy air protections under the Clean Air Act. The Lung Association opposes these actions that will add pollution to the air we breathe.
  18. Cutting air pollution through the Clean Air Act will prevent at least 230,000 deaths and save $2 trillion annually by 2020.
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