DETROIT — The wildfire smoke that has blanketed the state this month could take a toll on the health of Michiganians long after clearing.

The particles that form plumes of wildfire smoke are small (the average human hair is at least 30 times larger). That means they can seep into our blood, where they pose a triple threat to our lungs, hearts and brains, medical researchers say.

Doctors and medical researchers have known for decades that air pollution is linked to early death, said Sara Adar, a University of Michigan epidemiology professor and associate editor at the journal Environmental Health Perspectives.

From there, they discovered that air pollution hurts the respiratory and circulatory systems. The U.S. Centers for Disease Control and Prevention says particulate matter exposure can cause coughing, difficulty breathing, irregular heartbeats, asthma attacks and more.

Within the past decade, the pollutant has also been linked to affecting brain function, Adar said.

"Our brains are incredibly sensitive to how much oxygen we get, the pumping of the blood," she said. "Anything that's going to damage the blood vessels, which is part of what causes heart disease …, is going to damage the brain as well."

The connection is getting renewed attention as Michigan forecasters have issued more air quality warnings because of wildfire smoke this summer than at any time in at least 26 years. Further research into the role wildfires play in brain health will also be important going forward, as human-caused climate change intensifies droughts and amplifies wildfires, particularly in northern regions like Canada, according to the National Aeronautics and Space Administration.

"This is a climate change problem, no doubt about that," said Jonathan Overpeck, dean of the School for Environment and Sustainability at the University of Michigan. "We're paying the price. As long as we keep making it hotter and drier by burning fossil fuels, we're going to keep making this situation worse."

Last month, a team of researchers published a review of recent medical studies that show long-term exposure to small particle pollution known as PM 2.5 can increase a person's risk of developing dementia.

While exposure from any source of fine particle pollution was associated with greater rates of dementia, the link is particularly strong when those particles come from wildfire smoke and agriculture, according to a 2023 investigation Adar co-wrote in the journal JAMA Internal Medicine.

The researchers used data from a health survey of nearly 28,000 people who were part of a study between 1998 and 2016. Participants were surveyed on their cognitive health, overall health and behaviors until they died or stopped participating in the survey. Researchers only used data from people who did not have dementia at the time of their first interview.

They then reviewed the estimated amount of PM 2.5 the participants would have been exposed to at their home addresses over time, looking at the total amount of particle pollution and particle pollution from nine different sources, including road traffic, coal-fired power plants, wildfires and more.

Based on the results, the researchers estimated nearly 188,000 new cases per year of dementia were attributable to total PM 2.5 exposure in the U.S.

The researchers didn't determine why particles from wildfires and agriculture appear more closely linked to dementia, but Adar said they have several guesses.

Agricultural particles likely carry neurotoxic chemicals in pesticides and herbicides, which could affect the health and brain function of people who live nearby, she said.

Wildfire smoke tends to be very concentrated compared with other sources of pollution, which might increase its link to dementia, Adar said. It can also blanket areas for days at a time, like it recently did in Michigan.

"The pollution is really uncontrolled in a way that other sources are not," she said. "At this point, we've done a lot of work to clean up our cars and our trucks and our power plants in positive ways, but when you set the world on fire, you're burning everything."

It isn't just trees and vegetation that burn when wildfires rage.

"You're talking about burning gas stations and homes and cars, all of which are putting a toxic soup into the air," Adar said.

That toxic soup has been on the menu for a long time this summer.

As of Wednesday, there have been 21 days this summer when Michigan Department of Environment Great Lakes and Energy meteorologists issued air quality warnings for parts or all of Michigan.

The only comparable year is 2023, when Canadian wildfire smoke collected in Michigan and caused skyrocketing levels of pollution and a thick haze that hung low over Detroit. The pollution was stronger that year, but it didn't last as long, said Jim Haywood, EGLE senior meteorologist.

"We're almost double the number of days that we've issued some sort of an advisory" this summer, Haywood said. "It's been quite an active year."

2023 was the first year EGLE meteorologists issued an air quality advisory or action day because of wildfire smoke in Haywood's 26 years on the job, he said.

The location of wildfires, primarily in central Canada, is an important factor in this year's extensive length of poor air quality, Haywood said. Smoke from fires in the western U.S. and British Columbia has to blow a long way before it reaches Michigan. The ongoing fires are closer, and a north wind kicks their smoke directly toward Michigan.

Smoke is still lingering in the northern Lower and Upper Peninsulas, but at lower levels than earlier in August, Haywood said. The 10-day forecast shows Michigan getting a south wind that will blow the smoke back into Canada.

As for the rest of this summer, "it's going to be precarious," Haywood said.

"The one thing I can tell you is there are massive amounts of raging fires up in Manitoba and Ontario, which is pretty much due north of us, to the northwest a little bit," he said. "Just a few hundred miles away."

Haywood recommended people download the Enviroflash cellphone app at enviroflash.info to stay up to date on air quality advisories and alerts.

UM's Adar recommended people take steps to reduce their exposure to particle pollution. When there is a lot of PM 2.5 in the air, they should try to spend more time indoors and exercise indoors instead of outdoors. If available, they should run air filters or central air conditioning to filter particles from indoor air.

If someone has to be outside on a polluted day, wearing an N95 mask can reduce the amount of particles they breathe, Adar said.

People who are sensitive to pollution should take additional caution and pay closer attention to air quality, she said. Those include people with chronic health conditions, the elderly and children.

A warming climate change plays "a definitive and measurable role" in increasing wildfires in western North America, including in Canada, said Richard Rood, a UM professor emeritus of climate and space sciences and engineering.

Warmer air holds more moisture, which leads to longer dry spells and more extreme rain, he said. Dry air can suck moisture from plants and soil. That creates conditions ripe for wildfires.

"You get a burst of growth, especially in underbrush, that becomes more fuel," Rood said. "So if you have a dry summer that follows a wet spring, at some level it makes (fires) even more likely. It's sort of a pumping effect at some level."

Wildfires themselves exacerbate climate change, UM's Overpeck said, because greenhouse gases are released when wood and vegetation burn.

"It's a big positive feedback loop," he said. "You get hotter, drier conditions, you get more wildfire, you get more carbon dioxide released when the vegetation burns, and that makes things yet hotter and drier."

Michigan lawmakers, including the seven Michigan Republicans in the state's congressional delegation, have called on Canada to do more to suppress wildfires. They asked the Canadian government to "take immediate and decisive action to contain these fires and prevent future wildfires."

Good fire management practices and stopping the intentional or accidental blazes that spark wildfires can help protect against wildfires or limit their scope, but it's expensive work, especially for a country like Canada with so much remote landscape, Overpeck said.

It's reasonable to ask Canada to improve its fire management regimen, Overpeck said, but he said Canadians would be justified to criticize U.S. lawmakers and the Trump administration for trying to dismantle federal climate programs.

Pollution in Michigan blows into Canada, too, he said.

"I would ask our legislators to not just be telling Canada what to do, but to be cleaning up our air here in Michigan, which of course blows into Ontario," Overpeck said. "Our pollution is a precursor for the pollution in southern Ontario, and I'm sure there are politicians in Ontario that would like to see us reduce the pollution coming out of Michigan."

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