Millions of Americans in 14 states are breathing toxic wildfire smoke, prompting widespread air quality alerts across the Midwest and Northeast. Detroit, Michigan, recorded the world's worst air quality on Thursday morning, with an Air Quality Index (AQI) of 426, a level considered hazardous. Minneapolis, Minnesota, ranked third with an AQI of 349.
The smoke plume contains fine particulate matter, known as PM2.5, which consists of microscopic toxic particles small enough to penetrate deep into the lungs and bloodstream. The U.S. Environmental Protection Agency links exposure to PM2.5 with aggravated asthma, decreased lung function, irregular heartbeat, heart attacks, and premature death for individuals with pre-existing heart and lung conditions.
Most air quality alerts are expected to remain in effect until midnight Thursday. However, warnings in Minnesota may extend into Friday morning if dense smoke persists. Officials have cautioned that even brief exposure to the polluted air can lead to serious health effects and have advised residents to avoid outdoor activities.
In New York City, PM2.5 concentrations were found to be 7.8 times higher than the safety levels recommended by the World Health Organization. The widespread air quality issues stem from hundreds of wildfires burning across Canada, sending smoke southward into densely populated areas of the United States.
Michigan is experiencing some of the most severe conditions. Statewide air quality alerts are in place, with pollution levels ranging from unhealthy for sensitive groups in southern parts of the state to unhealthy, and potentially very unhealthy or hazardous, farther north. Major population centers, including Detroit, Grand Rapids, and Flint, are covered by these warnings. Residents are advised to limit strenuous outdoor activity and monitor for symptoms such as coughing, dizziness, or chest tightness. Closing windows and using air conditioning with high-efficiency filters are recommended to reduce indoor smoke intrusion.
Minnesota has also seen hazardous air quality, with dense smoke surpassing previous records in the Twin Cities. Ash particles have been observed in some areas. Officials are warning that everyone in central and northeastern Minnesota is likely to be affected and are advising the general public to avoid all outdoor physical activity. Air quality can vary significantly, with some nearby locations experiencing much cleaner air than others.
Northern Illinois, including Rockford and the Chicago metropolitan area, has declared air pollution action days. The National Weather Service noted the region is on the edge of a thick smoke plume moving south from Canada. Everyone in affected areas is urged to reduce prolonged outdoor activity, with particular caution advised for children, older adults, and those with respiratory illnesses.
Neighboring Indiana counties, particularly those south and east of Chicago, have also issued air quality action days due to expected unhealthy levels of PM2.5. Ohio has issued advisories for the entire state, anticipating air quality to reach unhealthy levels for sensitive groups. Northeastern Ohio, around Cleveland and Akron, faces maroon alerts, indicating extremely hazardous conditions for the general population.
Pennsylvania is under a statewide Code Red alert, meaning air quality is unhealthy for everyone. Smoke from Ontario and Minnesota is moving into the state, and while conditions are expected to improve slightly to Code Orange by Friday, air quality will remain unhealthy for sensitive groups. New York has issued fine-particle advisories across most of the state, including New York City and Buffalo, where AQI readings have exceeded 200, placing the pollution in the very unhealthy category. Alerts also extend across New England and into northern New Jersey and West Virginia's northern counties.