The smoke brought a charred smell, short-term symptoms that can be uncomfortable and long-term health risks.
Weather forecasters say relief should come when winds begin to clear the smoke on Friday.
In the meantime, we have answers to some basic questions about wildfire smoke and air quality in Detroit.
When will the smoke go away?
Keep your fingers crossed for Friday.
“There’s going to be some hazy skies again (on Thursday), and hopefully by at least Thursday night and into Friday, there’ll be a push of good westerly winds, and that should push most of it out,” said Andrew Arnold, meteorologist for the National Weather Service in Detroit.
The key to understanding the smoke forecast is wind, Arnold said. Winds out of the north, for instance, will tend to push smoke into Michigan and tank our air quality.
The wind will occasionally carry smoke to Detroit as long as fires are burning out of control at a large scale.
Are the Canadian wildfires going to be controlled any time soon?
Canada has 483 fires burning as of June 28, and more than half of them are out of control, according to the Canadian Interagency Forest Fire Centre Inc.
The fires are larger in size and number than usual for Detroit’s southern neighbor.
Wildfires in Canada have burned more land area in 2023 than in any year since 1982, and five times more than last year.
Canadian firefighting agencies are stretched thin as they contend with an unusual number of large fires.
What exactly is in the smoke?
All smoke is made of microscopic floating particles. The wildfire smoke particles are typically 0.3 micrometers in diameter — less than half the size of a single particle carrying COVID-19.
“This size of particles has the unfortunate ability to penetrate all the way down into the deepest parts of your lungs,” said Stuart Batterman, a professor at the University of Michigan who researches air quality. “This is one of the reasons why the health effects of this kind of particulate matter can be really severe.”
Smoke particles are smaller than typical air pollution in Detroit, according to measurements Batterman took when wildfire smoke came to Detroit in early June.
Because of their extra-small size, smoke particles have an easier time evading the body’s natural filters in the nose and lungs when compared to dust or other common pollutants.
The Canadian wildfire smoke is made up of several chemicals, some of which cause an irritating reaction upon contacting the lungs.
“The general consensus is that it’s more toxic than our usual pollutants,” Batterman said.
What are the health risks of breathing wildfire smoke?
Inhaling smoke can cause a lot of immediate health effects, according to the Centers for Disease Prevention and Control, including coughing, trouble breathing normally, stinging eyes, scratchy throat, runny nose, irritated sinuses, wheezing and shortness of breath, chest pain, headaches, an asthma attack, tiredness and fast heartbeat.
We know less about the long-term health effects of inhaling wildfire smoke, but the available research suggests a link with cancer and respiratory illnesses.
Doctors at Henry Ford Health have seen more patients than usual this month with respiratory complaints, likely due to wildfire smoke and high pollen counts, said Dana Jay, a spokesperson for the medical care provider.
How can Detroiters stay safe when the air is unhealthy?
When the air is unhealthy, wear an N95 or KN95 mask outdoors. Limit your time outdoors, and especially avoid physical exertion. Stick to indoor spaces where the air is filtered by central air or standalone air purifiers. Keep your windows closed.
If you have central air at home, double check that the fans in your system are running and that your air filters are rated at least MERV 13, meaning they can capture smoke particles.
If you’re in the car, turning on the A/C with air recirculation can reduce smoke, Batterman said.
What does AQI mean?
The Air Quality Index, or AQI, is a measure of pollution in the air we breathe. It’s calculated based on readings from a network of air monitoring stations around metro Detroit.
You can see a map of the monitoring stations and their readings on an air monitoring website from the Environmental Protection Agency.
AQI is calculated on a scale of 0-500. Detroit’s air is often between 50 and 100 AQI, meaning it’s of moderate quality but might irritate people who are especially sensitive to pollution.
Detroit’s AQI topped out at 376 early Wednesday morning. (From the EPA’s air quality site for Detroit, click “recent trends” to see calculations for the week and month.)
Does human-caused climate change affect wildfires?
Yes. Higher global temperatures are already linked to more severe wildfire impacts in the U.S. The land area burned by wildfires has increased in recent decades, and experts expect that global warming will lead to drier weather, which fuels wildfires.