What you need to know about bad air quality as wildfire smoke blankets major U.S. cities

Smoke from Canadian wildfires obscured the Statue of Liberty in New York City on Wednesday.

Chicago, Detroit, Minneapolis and New York City are considered some of the world's most polluted cities on Thursday, with eerily orange skies and dangerously bad air quality affecting residents.

Smoke from wildfires in Canada has drifted into several Midwest and Northeast states, similar to what happened in June 2023. According to the U.S. Air Quality Index, the air is considered unhealthy for sensitive groups in north Brooklyn. In downtown Minneapolis, the air is much worse and is considered hazardous for everyone. And in Chicago, the air around Wrigley Field is classified as "very unhealthy."

People with respiratory and cardiovascular conditions who live in these regions should pay close attention to their health.

Being exposed to wildfire smoke can cause elevated blood pressure, coronary events and issues with heart rhythm, according to a piece published last year in the journal Health Affairs and written by Michael Hadley, system director of advanced cardiac imaging at Northwell Health in New York. It can also worsen asthma and chronic obstructive pulmonary disease, or COPD.

"We can no longer afford to view wildfire smoke exposure as an isolated event," Hadley wrote. "It is a growing cardiovascular threat - one that demands a response as urgent as the fires themselves."

Research has shown that smoke pollution is a major health concern. A study published in 2024 in JAMA Network Open found that smoke from the Canadian wildfires in 2023 increased the cardiopulmonary disease burden for Maryland residents. Another study found that there is a connection between smoke pollution and older adults being hospitalized for respiratory diseases. Other research has shown that bad air quality brought on by wildfire smoke often leads to surges in emergency-room visits.

Wildfire smoke includes fine particulate matter - also called PM2.5 - which can raise the risk of heart problems. It's also what causes the air to appear hazy.

"If you look at the burden of cardiovascular disease across the world, this PM2.5, some of which comes from traffic and industry, but an increasing proportion comes from wildfires, that is really the No. 1 environmental risk factor chronically for the development of heart attack [and] stroke cardiovascular mortality," Hadley said in an interview.

People living in affected regions should minimize their exposure to the smoke, particularly if they have a cardiovascular or pulmonary condition or are considered at higher risk due to pregnancy or age. People can also consider using HEPA air purifiers, wearing an N95 mask and limiting outdoor exercise.

-Jaimy Lee

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July 16, 2026 15:30 ET (19:30 GMT)

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