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Key Findings

The State of the Air 2019

Too many cities across the nation experienced more ozone and more particle pollution in 2015-2017. Many reached or tied their highest levels ever.

The "State of the Air" 2019 found that, in 2015-2017, more cities had high days of ozone and short-term particle pollution compared to 2014-2016 and many cities measured increased levels of year-round particle pollution.

The "State of the Air" 2019 report shows that too many cities across the nation increased the number of days when particle pollution, often called "soot," soared to often record-breaking levels. More cities suffered from higher numbers of days when ground-level ozone, also known as "smog," reached unhealthy levels. Many cities saw their year-round levels of particle pollution increase as well.

The "State of the Air" 2019 report adds to the evidence that a changing climate is making it harder to protect human health. The three years covered in this report ranked as the hottest years on record globally. High ozone days and spikes in particle pollution zoomed, putting millions more people at risk and adding challenges to the work cities are doing across the nation to clean up.

The 2019 report—the 20th annual release—uses the most recent quality-assured air pollution data, collected by the federal, state and local governments and tribes in 2015, 2016 and 2017. The "State of the Air" 2019 report looks at levels of ozone and particle pollution found in official monitoring sites across the United States in 2015, 2016 and 2017. For comparison, the "State of the Air" 2018report covered data from 2014, 2015 and 2016.1 The report uses the most current quality-assured nationwide data available for these analyses.

The report examines particle pollution (PM2.5) in two separate ways: averaged year-round (annual average) and short-term levels (24-hour). For both ozone and short-term particle pollution, the analysis uses a weighted average number of days that allows recognition of places with higher levels of pollution. For the year-round particle pollution rankings, the report uses averages calculated and reported by the U.S. Environmental Protection Agency (EPA).

Overall Trends

The "State of the Air" 2019 found that ozone and short-term particle pollution worsened in many cities in 2015-2017, compared to 2014-2016. Even levels of year-round particle pollution increased in some cities.

More than 141 million Americans, or more than 4 in 10 of us, live in counties that got at least one "F" for unhealthy air.

More than four in 10 Americans, approximately 43.3 percent of the population, live in counties that have monitored unhealthy ozone and/or particle pollution. The number of people exposed to unhealthy air increased to nearly 141.1 million. That represents an increase from the past two reports: higher than the 133.9 million in the 2018 report (covering 2014-2016) and the 125 million in the 2017 report (covering 2013-2015). Close to 20.2 million people, or 6.2 percent, live in 12 counties with unhealthful levels for all three measures.

More than 4 in 10 people live where the air is unhealthy.

Still, progress continues, thanks to the tools in the Clean Air Act. While this is a significant spike in areas with unhealthy levels of ozone and particle pollution, it remains still far below the 166 million in the years covered in the 2016 report (2012-2014).

Los Angeles remains the city with the worst ozone pollution as it has for 19 years of the 20-year history of the report. Fresno-Madera-Hanford, CA returned to the most-polluted slot for year-round particle pollution, while Bakersfield, CA, maintains its rank as the city with the worst short-term particle pollution.

More must be done to address climate change and to protect communities from the growing risks to public health. This year's report covered the three warmest years in modern history and demonstrates the increased risk of harm from air pollution that comes despite other protective measures being in place. The Clean Air Act must remain intact and enforced to enable the nation to continue to protect all Americans from the dangers of air pollution. This law has driven improvements in air quality for nearly 50 years, improvements that the "State of the Air" 2019 continues to document. Figure 1 from EPA shows that since 1970, the air has gotten cleaner while the population, the economy, energy use and miles driven increased greatly.2 We must ensure that the Clean Air Act’s tools remain in place, funded, and followed.

Comparison of Growth Areas and Emissions

Air pollution emissions have dropped steadily since 1970 thanks to the Clean Air Act. Source: U.S. EPA, Air Trends: Air Quality National Summary, 2019.

As climate change continues, cleaning up these pollutants will become ever more challenging.

The "State of the Air" 2019 report shows, again, that climate change makes it harder to protect human health. This year’s report shows the spike in high ozone days and in unhealthy particle pollution episodes driven by wildfires. While most of the nation has much cleaner air quality than even a decade ago, too many cities suffered increased ozone from the increased temperature and continued high particle pollution from wildfires driven by changing rain patterns.

As climate change continues, cleaning up these pollutants will become ever more challenging. Climate change poses many threats to human health, including worsened air quality and extreme weather events. The nation must work to reduce emissions that worsen climate.

The Clean Air Act must remain intact and enforced to enable the nation to continue to protect all Americans from the dangers of air pollution. At its core, the Clean Air Act protects public health and has driven improvements in air quality for nearly 50 years, as shown in Figure 1. Since 2000, the "State of the Air" reports have also documented these improvements, as shown in trend charts for counties and cities available at That progress is not certain to continue, as some in Congress seek to remove or weaken that law, and as the administration seeks to repeal or reverse the safeguards in place to enforce the law.

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Did You Know?

  1. More than 4 out of 10 people live where the air they breathe earned an F in State of the Air 2019.
  2. More than 141.1 million people live in counties that received an F for either ozone or particle pollution in State of the Air 2019.
  3. More than 20.1 million people live in counties that got an F for all three air pollution measures in State of the Air 2019.
  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, cardiovascular disease and diabetes.
  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 rollback 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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