For a second day in a row, thick wildfire smoke continued to smudge out the sky in Calgary, where air-quality values rose to levels considered to be a "very high" health risk.
The city remained Wednesday under a special air-quality statement, along with vast areas of Western Canada, as wildfires continue to burn amid a stretch of dry, warm and windy weather.
According to forecasters with Environment and Climate Change Canada, the smoke most likely isn't leaving the Calgary area for the next few days, although the thickness might fluctuate.
Terri Lang, a meteorologist with the agency, said that smoke and air-quality conditions are likely to improve slightly on Thursday. However, after that, they might worsen again over the weekend as a ridge of high pressure descends from the northwest, where dozens of wildfires are burning.
"Forecasting smoke is very, very difficult, just because it's at the mercy of the winds that we see," she said.
"It's not like a thunderstorm. You see a thunderstorm coming, it's going to go through and then it's done. …With smoke, there are so many variables that go into it, and one of them is how much smoke is coming off the wildfires."
For their forecasts, Lang and other meteorologists lean on complex dispersion models, which map out how smoke might move across an area.
One of these, FireSmoke, is available to the public. It's latest update shows smoke from fires in northern Alberta and Saskatchewan wafting over the Calgary area in varying levels of thickness.
Top of the scale
On Wednesday afternoon in Calgary, the Air Quality Health Index was again at 10+, the highest level issued. The index shot up to 10+ on Tuesday morning, when the thick smoke first blanketed the region.
The Calgary Region Airshed Zone Society maintains monitoring stations across the city that test for air quality. The data gathered is what forecasters uses to inform the Air Quality Health Index.
While the machines test several factors, the most important of these is PM 2.5. In plain English, that translates to particulate matter that's 2.5 micrometres across or smaller. Such particles are heavy in wood smoke.
"It's that stuff that you can't cough out. You're not coughing out that 2.5. It's staying in your lungs," said Jill Bloor, the Calgary airshed zone's executive director.
Watch | Dr. Raj Bhardwaj explains how wildfire smoke impacts the body
The extended period of extremely poor air quality with readings in the 10+ range has led sports teams to cancel practices and school to keep children indoors during the day.
Dr. Kerri Johannson, a clinical associate professor of medicine at the University of Calgary and lung specialist, said the most vulnerable groups are newborn babies with developing lungs, elderly adults, pregnant people, and those with lung or heart conditions.
People in these groups can experience severe symptoms, as the air quality can exacerbate the pre-existing conditions. And it's not just the PM 2.5 particles that pose a threat.
"Wildfire pollution is more toxic than general pollution, because it's representative of just burning everything in its path, and that can be rubber and plastic, and tires and buildings," she said. "All of that gets vaporized and gaseous, and it's what we inhale."
Johannson noted that the severe symptoms linked to extremely poor air quality might not present themselves when the wildfire smoke arrives, but instead, studies suggest, the symptoms manifest days later.
Alberta Health Service told CBC News that there's been no significant spike in ER visits due to wildfire smoke since Tuesday morning. However, an AHS spokesperson said that call centre staff in the Calgary zone did reported an increase in calls regarding wildfire smoke and air quality.
Masks only do so much
The best defence against exposure to toxic levels of wildfire smoke is staying indoors, health experts say. They encourage people to keep their windows shut at home or spend time in places with good air filtration systems, such as shopping malls or swimming pools.
For those who must venture outdoors, it's advised they wear an N95 mask. However, while these masks can filter out the tiny PM 2.5 particles, they don't protect against the toxic gasses in wildfire smoke, Johannson said.
She noted that it's also important for people with chronic conditions to have their medications on hand in case of an emergency. For example, those with asthma should have their inhalers at the ready.
Tammy MacDonald, who has asthma, said the last 24 hours have been difficult.
"I've been coughing a lot," she said in downtown Calgary on Wednesday. "I try not to go outside."