Wildfires have charred over 7.6 million acres in dramatic blazes in the United States so far this year, but that may not be so unusual in coming years: The risk of similar "very large" wildfires is expected to increase sixfold by mid-century, according to a new study from the National Oceanic and Atmospheric Administration.
What toll will those fires take on our health? Early research provides a glimpse of what it could mean.
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Smoke, which billows far from the fire's source, is known to be dangerous to the lungs and heart, although many details on exactly how wildfires impact the body's systems are still emerging.
For example, a study published earlier this month reviewed medical records over a two-month span of raging wildfires in Australia, noting a jump of 6.9 percent in cardiac arrests outside of hospitals. And it's been established that they exacerbate asthma and other respiratory problems.
Although they say more studies are needed, researchers believe the culprit to be particles so tiny, 2.5 thousandths of a millimeter in diameter, they're typically invisible.
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"These particles are amazingly harmful," said Janice Nolen, assistant vice president of the American Lung Association.
"They are tiny bits of things that can get into the lungs, bypassing the systems of protection because they're so tiny -- you cough the bigger ones out," Nolen said. "The tiniest of them can pass through the lungs into the bloodstream. There are various chemicals and toxic gases associated with them."
In fact, these particles may prove to be harmful to our health in ways yet to be seen, said study author Anjali Haikerwal, a doctoral candidate at the School of Public Health and Preventive Medicine at Monash University in Melbourne, Australia.
"There are lots of postulations and different theories as to how they affect the heart," she said. "There's no concrete evidence that this is exactly what it does."
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For example, most of the research so far has focused on population groups that are already at risk: those who have preexisting heart conditions, for example, and the elderly, and it's clear that children, low-income people and Native communities are also likely at a higher risk.
"Pretty much everybody has somebody in their family who's at risk," Nolen said. "We're talking about a lot of people."
It's also quite possible that the particles are unhealthy for all of us. Wildfires aren't the only cause of them: the ambient air near power plants, for example, carries them, and campfires and wood stoves can be culprits as well.
The particles shouldn't all be lumped in the same category, however. Wildfires produce particles with a different chemical composition, and their reach is intense and far-reaching while the fire blazes. It's hard to replicate those conditions in a lab, and challenging to gather research material in dangerous situations.
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In the meantime, the American Lung Association offers tips on protecting yourself during wildfires, and the Environmental Protection Agency maintains air quality updates.
"This is something we're going to have to deal with for a long time," Nolen said. "Climate change contributes to a lot of the drought that is feeding this, and it's why we're supporting steps that would help to tackle climate change, such as reducing emissions. In terms of helping to fix it, it's going to take a while, but we have got to do it because we are already seeing the impact of it today."
Plumes of smoke rise from the Rocky fire after it jumped Highway 20 near Clearlake Oaks, Calif.
Nearly 30,000 firefighters and support staff were battling blazes across a handful of mainly western U.S. states, after millions of acres and multiple buildings have burned. A total of 7.16 million acres have gone up in flames across the country this year, the National Interagency Fire Center said. That's the earliest the 7 million mark has been reached in the past 20 years, it said, adding that a large portion of this was from Alaskan wildfires several months ago.
A total of 41,194 fires were burning across the United States, Boehle said, adding that as of Tuesday, 1,074 structures had been scorched. "You'll see firefighters from all over assisting with the western wildfires," center spokeswoman Tina Boehle said, adding that personnel from the eastern seaboard to Alaska had been tapped.
Above, the Jerusalem Fire burns at the Lake and Napa County lines after jumping north of the highway Tuesday afternoon.
Canada has offered 100 firefighters plus other personnel and 20 "smokejumpers" who parachute in to fight the blazes. The center was also in discussion with Australia to provide assistance, she said. On Tuesday, authorities announced that the U.S. military would be sending troops.
Navy Captain Jeff Davis, a Pentagon spokesman, said 200 troops from Washington state would receive three days' training before heading out to confront the infernos.
A heatwave exacerbating four years of drought is also making California vulnerable. A total of 41,194 fires were burning across the United States, Boehle said, adding that as of Tuesday, 1,074 structures had been scorched.
In California, dry lightning strikes sparked most of the fires, while the causes of others remained unknown. But authorities said they did not suspect foul play. Thousands of lightning bolts since caused hundreds of smaller fires throughout the state, but most of the blazes were concentrated in the north, California fire chiefs said.
Idaho's Soda Fire, which has been one of the largest blazes, was 90 percent contained Wednesday after burning through 283,686 acres.
Meanwhile since Friday, more than 1,000 firefighters have struggled with a blaze started by lightning in the Chelan, Wash., area, where at least 49 buildings have been destroyed and authorities have issued evacuations that affect some 3,000 people, the Seattle Times reported.
The 10 states affected by large fires are Oregon, Washington, Idaho, Montana, California, Nevada, North Carolina, Louisiana, Texas and Arizona, Boehle said. The northwest quadrant -- Washington and Oregon -- is the center's "highest priority," she said. "The last couple of years have been unusual in the Northwest with reduced precipitation. We've been seeing more fires in the Northwest than usual."