Mix of extreme heat and wildfire smoke can be very dangerous, experts say

As several cities across the United States are battling extreme heat, they're also facing the threat of wildfire smoke.

Canada is facing its worst wildfire season on record and fires have already broken out along the West Coast, causing hazy conditions and poor air quality.

While scorching temperatures and toxic plumes from fires are each hazardous to human health on their own, experts warn that the two coming together is a dangerous combination.

"Independently, wildfire smoke and extreme heat conditions can greatly impact human health, particularly those who are vulnerable, meaning those who already have some underlying cardiovascular and metabolic or respiratory conditions," Chris Minson, a professor of human physiology at the University of Oregon, told ABC News. "And so then, when you combine the two things, certainly there can be an exacerbation of those problems."

Cyclical relationships of wildfire smokes and heat

Scorching temperatures have been recorded across the county, shattering records.

Tuesday marked the 19th consecutive day that temperatures were at or above 110 degrees Fahrenheit in Phoenix, Arizona. On Monday, Miami recorded the 16th consecutive day that heat index values were at or above 105 degrees.

The National Weather Service Climate Prediction Center warned it's only going to get worse, tweeting Thursday, "Hot, summertime conditions expand over the Lower 48 beginning the middle of next week. Many locations within the Midwest may reach their hottest temperatures of the year thus far."

Meanwhile, wildfire smoke from Canada recently returned to the U.S, moving air quality index rankings into the "unhealthy" category.

What could be happening is that heatwaves are begetting wildfire seasons and vice versa.

"So, you have a heatwave? Well, that leads to a longer fire season," Saagar Patel, a doctoral Student at the Institute of the Environment & Sustainability at the University of California, Los Angeles, told ABC News. "Fires will begin earlier in the year, and they'll end later in the year and so there is a direct impact where a longer or more pronounced heat wave will lead to longer fire seasons."

"And during fire seasons, you know, you're producing more greenhouse gases, which directly lead to climate-influenced events, such as heat waves, and so you have this feedback loop that exists," he said.

Effects on the body

Many of the health impacts of wildfire smoke have been well-documented and mostly lie with fine particulate matter known as PM2.5.

Because these particles are too small to be seen with the naked eye, they can easily enter the nose and throat and can travel to the lungs, with some of the smallest particles even circulating in the bloodstream, according to the Environmental Protection Agency.

PM2.5 can cause both short-term health effects, even for healthy people, including irritation of the eyes, nose and throat; coughing, sneezing; and shortness of breath and long-term effects such as worsening conditions such as asthma and heart disease.

"When you add the heat on there -- humans are incredibly well adapted to adjust to heat as long as we're healthy and hydrated, but even in those conditions -- high heat stress puts a real strain on our cardiovascular system," Minson said.

To cool down, the body doesn't just sweat but increases skin blood flow. By increasing the amount of blood flowing through the body and speed, this widens blood vessels and allows heat to escape.

"That means we have to divert blood flow from other areas, which is harder to do if those other areas are having an inflammatory response," Minson said. "A healthy individual can manage those as long as things aren't getting out of control, but it's those who are at risk with other cardiovascular diseases are young and elderly, are going to really struggle."

Patel added that people also have to breathe deeper to cool down, which means people could be inhaling those fine particles that can cause health issues.

A June 2022 study from the University of Southern California found the number of deaths rose on hot days and on days with high levels of PM2.5 rose, but the risk of death was roughly three times greater when both happened compared to when the conditions occurred on their own.

"I think research has shown or at least demonstrate...the risk is greater than the sum of the parts." he said. "You're at risk of death when there's a heatwave, you're at risk of death when there's bad air quality, but it turns out, you're at more risk and when those happen at the same time."

Climate change will worsen the issue

Studies have shown climate change is already leading to an increase in wildfire season length and the frequency of wildfires. Research has also found climate change is increasing the number of hotter days and more extreme heat waves.

Experts fear his means there will be more overlap between extreme heat and wildfire seasons, leading to more people being affected.

"The problem is...that the real risk of climate change is that it's going to make much more dynamic climate problems meaning we're gonna have these heat domes more regularly, we're going to have extreme dry areas that normally get more rain or become very, very fire prone," Minson said. "And then that's going to be the problem is the number of heat events, we're going to have super dry periods, we're gonna have more forest fires."

He continued, "And then when you've got those things combined, you just are exacerbating all the problems independently, they're bad enough and challenging for a lot of humans. When you combine them, now you've got real, real problems."

Dr, William Vizuete, a professor in the Department of Environmental Sciences and Engineering in the Gillings School of Public Health at the University of North Carolina at Chapel Hill, said if you can, make sure you have a HEPA filter in your home to filer the air and put on air conditioning to handle hot temperatures or get to a cooling center.

He also advised wearing a mask limiting time outdoors, and wearing a mask if you need to be outside and keep track of temperatures and the wildfire smoke situation with air quality tracking sites like AirNow or PurpleAir.

"You can use that to kind of provide some sort of guidance, you know, 'Is it a better quality today? Maybe I should protect myself from being outside minimize my time outside,'" he said. People can also purchase a low-cost sensor that they can put in their home or just outside their home and be able to monitor their air quality in real time, he said.