Wildfires have burned a record of 20 million acres across Canada so far this year, with no end in sight. There are currently 500 active wildfires throughout the country and more than 250 have been deemed out of control, according to the Canadian Interagency Forest Fire Center. The smoke has been making its way to the U.S. for over a month.
Here's how the news is developing. All times Eastern.
Jun 28, 2023, 11:53 AM EDT
White House monitoring air quality issues as Biden visits Chicago
President Joe Biden has touched down in Chicago for fundraising and an economic address, and the White House said his schedule has not been modified due to the poor air quality in the city.
Marine One with President Joe Biden flies over a hazy Chicago, June 28, 2023, as some 80 million people from the Midwest to the East Coast are under air quality alerts due to smoke from Canadian wildfires sweeping the nation.
Andrew Caballero-Reynolds/AFP via Getty Images
A jogger runs along the shoreline of Lake Michigan with heavy smoke from the Canadian wildfires, June 27, 2023, in Chicago, Illinois. Chicago Mayor Brandon Johnson said in a statement, "The City of Chicago is carefully monitoring and taking precautions as the U.S. Environmental Protection Agency has categorized our Air Quality Index as "unhealthy" due to Canadian wildfire smoke present in the Chicago region. We recommend children, teens, seniors, people with heart or lung disease, and individuals who are pregnant avoid strenuous activities and limit their time outdoors."
Kamil Krzaczynski/AFP via Getty Images
"No modifications to today's schedule that I'm aware of as a result of this," principal deputy press secretary Olivia Dalton said. "But certainly, we are monitoring the air quality issues across the country closely and federal agencies are ensuring that federal resources are available in affected regions as appropriate."
The Air Quality Index in hazy Chicago reached 207 on Wednesday morning. Any number over 100 is considered unhealthy for sensitive groups.
-ABC News' Molly Nagle
Jun 28, 2023, 10:33 AM EDT
How to stay safe from wildfire smoke amid reduced air quality
Wildfire smoke and ash can irritate eyes, nose, throat and lungs, making you cough or wheeze and can make it hard to breathe, according to the U.S. Centers for Disease Control and Prevention.
The CDC says the most effective way to protect yourself during wildfire emergencies is to stay indoors or limit time outdoors when there is smoke in the air. This is especially important for those with heart or lung conditions who are at higher risk for adverse health effects.
"People who are most at risk are [the] elderly, immunocompromised, young children and people who already have respiratory problems, people with asthma and things like that," said Dr. Stephanie Widmer, a member of ABC News' Medical Unit.
Winds at the mid-levels of the atmosphere are causing the Canadian wildfire smoke to concentrate over a specific area of the midwestern and eastern U.S.
Meanwhile, a heat dome that’s been causing stagnant deadly heat in the Deep South for weeks is keeping the smoke largely out of the region.
The next round of widespread showers and thunderstorms for this area of the eastern Midwest and the East is forecast to arrive on Friday and continue through the weekend, which will clear the smoke.
But as long as the wildfires continue to rage in Canada, these events of dense smoke plumes will likely continue to disperse into the U.S. Canada's wildfire activity typically peaks from June to August.
Jun 28, 2023, 7:59 AM EDT
What to know about the Air Quality Index from wildfire smoke and how it affects human health
Heavy blankets of smoke billowing over the United States from wildfires burning in neighboring Canada are threatening the health of millions of people -- even non-vulnerable populations with no preexisting conditions. But what about the smoke makes it so hazardous for humans to be around?
Wildfire smoke contains fine particulate matter, known as PM2.5, which are microscopic solid or liquid droplets -- often 30 times smaller than the diameter of a human hair -- that can be inhaled and cause serious health problems, according to the U.S. Environmental Protection Agency.
Most particles form in the atmosphere as a result of complex reactions of chemicals, such as sulfur dioxide and nitrogen oxides -- pollutants emitted from power plants, industries and automobiles. But wildfires likely contain PM2.5 that is up to 10 times more harmful than the same type of air pollution coming from combustion activity, according to a 2021 study conducted in California.
Air Quality Index (AQI)
ABC News Photo Illustration
PM2.5 is considered unhealthy for "Code Orange" and sensitive groups once the Air Quality Index surpasses 100, according to AirNow, a website that publishes air quality data. Once the AQI surpasses 150, it is considered "Code Red," unhealthy for some members of the general public who may experience health effects, with sensitive groups experiencing more severe effects.
The AQI is at "Code Purple" once it surpasses 200, considered "very unhealthy" with increased health risk for all populations. "Code Maroon" is labeled as "hazardous" and a health warning for emergency conditions once the AQI reaches 300 and higher.
At Code Maroon, "everyone is more likely to be affected," according to AirNow.
A "good" AQI is measured at 50 and below, and a "moderate" air quality index ranks between 51 and 100.
