New Report: Chicago Now Ranked 18th Most Polluted City in the U.S.

American Lung Association's 'State of the Air' report finds Chicago's air pollution worsened

The American Lung Association’s 2019 “State of the Air” report revealed that Chicago ranked the 18th most polluted city in the nation for ozone pollution, which is worse than last year’s report where the city was ranked 22nd most polluted. The 20th annual report found that Chicago had a weighted average of 14 unhealthy ozone days between 2015-2017, which is significantly higher than the average of 9.8 unhealthy days from last year’s report.

“Chicago residents should be aware that we’re breathing unhealthy air, largely caused by hotter days and vehicle emissions, placing our health and lives at risk,” said Angela Tin, national senior director for clean air initiatives for the Lung Association. “In addition to challenges here in Chicago, the 20th-anniversary ‘State of the Air’ report highlights that more than four in 10 Americans are living with unhealthy air, and we’re heading in the wrong direction when it comes to protecting public health.”

The annual “State of the Air” report tracks Americans’ exposure to unhealthful levels of ozone or particle pollution, both of which can be deadly. This year’s report covers the most recent quality-assured data available collected by states, cities, counties, tribes and federal agencies in 2015-2017. Notably, those three years were the hottest recorded in global history.

Each year the “State of the Air” provides a report card on the two most widespread outdoor air pollutants, ozone pollution, also known as smog, and particle pollution, also called soot. The report analyzes particle pollution in two ways: through average annual particle pollution levels and short-term spikes in particle pollution. Both ozone and particle pollution are dangerous to public health and can increase the risk of premature death and other serious health effects such as lung cancer, asthma attacks, cardiovascular damage, and developmental and reproductive harm.

Ozone Pollution in Chicago

  • Grade: F
  • Rank: 18th most polluted
  • 14 unhealthy ozone days

Compared to the 2018 report, Chicago experienced more unhealthy days of high ozone in this year’s report.

“My life has been affected by asthma since birth. I had to be very careful about walking outside year round. In the winter months it was the cold weather in the warmer months it was pollen,” said Chicago resident Renee Matthews, M.D. “Air pollution from cars and industrial buildings fills the air and even if I am in the car, it would cause me breathing problems. I often had to close the windows even if I had no air conditioning and it was boiling hot but I couldn't breathe. There was a city near my hometown that was known for its odor due to pollution and I was required to cover my mouth and nose if I was walking outside in this city.”

This report documents how warmer temperatures brought by climate change make ozone more likely to form and harder to clean up. This year’s report showed that ozone levels increased in most cities nationwide, in large part due to the record-breaking global heat experienced in the three years tracked in the report.

Particle Pollution in Chicago

  • Short-Term Particle Pollution
    • Grade: C
    • Rank: 35th most polluted
    • 1.2 unhealthy air quality days
  • Year-Round Particle Pollution
    • Grade: Pass
    • Rank: 19th most polluted

The 2019 report also found Chicago had the lowest levels ever of both year-round particle pollution and short-term particle pollution.

“Particle pollution is made of soot or tiny particles that come from coal-fired power plants, diesel emissions, wildfires and wood-burning devices. These particles are so small that they can lodge deep in the lungs and trigger asthma attacks, heart attacks and strokes, and can even be lethal,” said Tin. “Year-round particle pollution levels have dropped thanks to the cleanup of coal-fired power plants and the retirement of old, dirty diesel engines.”

While the report examined data from 2015-2017, this 20th annual report online provides information on air pollution trends back to the first report. Learn more about Chicago’s rankings, as well as air quality across Illinois and the nation, in the 2019 “State of the Air” report at

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