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Breathing Minnesota Air Thursday Was Like Smoking 19 Cigarettes, Per AQI Scale

Minneapolis had the world's worst air quality Thursday, and a doctor's smoking scale shows just how dangerous that air really was.

| Updated
A dog walks along the shores of Lake Superior amid heavy wildfire smoke Thursday, July 16, 2026, in Duluth, Minn. (AP Photo/Scott Bauer)

TWIN CITIES, MN — Wildfire smoke will continue to impact Minnesota on Friday, creating dangerous conditions, before wind pushes the smoke northeastward, according to the National Weather Service.

And those hazy skies aren't just an annoyance—they're a real danger, and breathing in the air is the equivalent of smoking multiple cigarettes, Dr. Jonathan M. Tan, division chief of General Anesthesiology at Children’s Hospital of Philadelphia, told AccuWeather.

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That's because of PM2.5, tiny particles that are also found in cigarette smoke and can travel deep into the lungs.

"Scientists have found that an air quality reading of about 20 on the AQI scale is roughly like smoking one cigarette a day," Tan said. "So when the AQI climbs into the 150+ range for a full day outside, that’s in the ballpark of 7 to 9 cigarettes."

Minneapolis had the worst air quality in the world on Thursday afternoon, with an Air Quality Index (AQI) of 374, FOX 9 reported.

Doing the math, breathing Minneapolis's air Thursday afternoon was roughly like smoking 19 cigarettes, based on Tan's scale.

Chicago was ranked second with an AQI of 338 and Detroit is now third with an AQI 219. As the air quality changes, the rankings are frequently updated.

Minneapolis is thankfully down to No. 92 as of Friday morning, according to IQAir.

Air Quality Alert Set To Expire Friday For Most Of Minnesota

The Minnesota Pollution Control Agency says air quality is set to improve across most of the state Friday, though the alert covering wildfire smoke will continue through the weekend in the northeast.

The agency's alert, in effect since 3 p.m. Thursday for east central, central, west central, southeast, north central, northwest, and northeast Minnesota, is scheduled to expire at 11 a.m. Friday for most of the state as a low pressure system moves through the region.

Read more here.

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