Smoke from wildfires raging thousands of miles away in central and western Canada and the western United States that began affecting air quality in Maine around midday Monday won’t dissipate until late Tuesday.

The particle pollution concentration will reach the “Unhealthy for Sensitive Groups” range on the Air Quality Index for Maine before the smoke clears out Tuesday evening, according to the Maine Department of Environmental Protection.

Though the smoke may only be seen as hazy skies and a reddened sunset, the hidden dangers of wildfire smoke – even from fires burning thousands of miles away – are significant for at-risk individuals.

For those with respiratory illnesses such as asthma or bronchitis, this means a greater risk of irritation and possibly reduced lung function. Signs of distress include coughing, shortness of breath, throat irritation and uncomfortable sensations in the chest.

But the most significant concern is for people with cardiovascular disease.

“People who are at risk of heart attack or stroke are much more likely to experience problems when they’re breathing fine particle pollution,” said Kevin Stewart, director of environmental health at the American Lung Association.


Approximately half of the country’s population can be considered part of a ‘sensitive group,’ which includes children and teenagers, the elderly and people with heart or lung diseases, Stewart said.

“Children are not just miniature adults, their lungs are developing,” he said. “And there’s certainly a tendency for children not to pay attention to their symptoms when they’re playing outdoors.”

It is still safe to be active outside, but sensitive people should avoid heavy exertion and take more breaks when outdoors, the DEP said in an air quality alert it issued Monday. The department also recommends that at-risk individuals circulate air indoors and keep windows shut.

The agency’s spokesman did not respond to a message seeking additional information Monday.

“We don’t want people to panic or overreact, but we do want people to exercise good caution,” Stewart said. “Maybe you make certain changes in your schedule, you don’t do that big outdoor exercise event, and you pay more attention to your body.”

With wildfire smoke, the main health concern is microscopic toxins 2.5 microns in diameter, referred to as PM 2.5, which are approximately 30 times smaller than the width of human hair. When inhaled, these particles can injure the linings of the lungs and enter the bloodstream.


And even though the wildfires are burning thousands of miles away, the largest ones have enough heat to push smoke upward into the free troposphere, where strong upper level winds carry the smoke to Maine and reduce the air quality.

Although it’s common for smoke from western wildfires to reach eastern North America during fire season, the smoke normally isn’t detected because it passes at altitudes of 5 to 10 kilometers, or roughly 3 to 6 miles, according to the NASA Earth Observatory.

But smoke from the current fires is less than 1 mile from the ground, producing hazier conditions and more air quality warnings along the Eastern Seaboard, NASA reported.

The smoke reaching Maine is likely originating from wildfires in Canada just north of Minnesota, though fires in the western U.S. also may be contributing a smaller amount of smoke, according to a NASA publication, Smoke Across America.

“This is clear evidence that we can be downwind, even thousands of miles away, and feel the effect of these increasingly powerful fires,” Stewart said. “The Lung Association recognizes that one of the clear public health issues of our time is the need to solve the problem of climate change, because it leads to this kind of problem that can actually affect air quality today.”

Though human activities, such as making campfires and discarding lit cigarettes, are the main causes of wildfires, rising temperatures and extended droughts connected to climate change make forests much more flammable.

Recent record-setting heatwaves and droughts in the western U.S. and Canada have kick-started this year’s fire season much earlier than anticipated.

In the United States, there are currently 85 active fires, the majority of which are in Idaho, Montana, Washington, California and Oregon. In Canada, there were 263 uncontrolled fires as of Wednesday.

Air quality in Maine can be monitored at the DEP website, or via the EPA’s email and text alert system, EnviroFlash.

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