Summer of smoke among the worst on record for Alberta's biggest cities

Smoke drifting through an open window. Haze so thick the street lamps glow hours before dusk.

Air pollution from wildfires has become an unwelcome part of summer in Alberta and this season has been particularly poor, rivalling the worst years on record for Edmonton and Calgary.

Smoke has choked the skies over Alberta this week, triggering high-risk air pollution that forced people to cancel their outdoor plans and hunker down inside.

A few more hazy days could make this wildfire season a record-breaker for Edmonton and Calgary, as experts caution that smoky summers fed by longer, more intense wildfire seasons will become the norm.

"It's not a good story here or a happy story," said Natalie Hasell, a warning preparedness meteorologist with Environment Canada.

"The people who are susceptible to smoke are the same people, more or less, who are susceptible to heat.

"And we have seen a number of times already this year where both have happened at the same time. That could easily happen again in the not-so-far future for Alberta."

Tracking 'smoke hours'

For the past 70 years, Environment Canada has tracked "smoke hours" for communities across the country. Smoke hours are counted when the haze from wildfires is so thick that visibility is reduced to 9.7 kilometres or less.

The smokiest year on record for both Edmonton and Calgary was 2018. Between May and September of that year, Edmonton recorded 229 smoke hours.

Between May 1 and July 17 of this year, Edmonton has already recorded 194 smoke hours, already the second-highest number of hours on record.

"By the end of this season we might not be in second place anymore, if this year continues the way it has been," Hasell said in an interview Monday.

In 2018, Calgary recorded 450 smoke hours between May and September. To date this year, the city has seen 258 smoke hours, the fourth highest year on record.

Alberta spent the weekend under a blanket of smoke with air pollution measuredat a 10-plus on the Air Quality Health Index.

Developed by Health Canada, the system monitorsthe severity of air pollution by tracking fine particulate matter, ground-level ozone, and nitrogen dioxide. When the rating is high, people exposed to the smog face significant health risks.

The haze lifted on Monday but the clearer skies are not expected to last. Heavy rainsTuesday will be followed by a return to hot, dry weather that is expected to fuel fires burning across the west.

"We do see another long stretch of hotter and drier conditions coming," Hasell said."This could be a very short-lived reprieve, unfortunately."

• Check theCBC News Climate Dashboardfor live updates on wildfire smoke and active fires across the country.

This season has been historic for wildfires across the Prairies, and air quality advisories have been triggered repeatedly as smoke from fires burning across the country drifts across the province.

A summer heat wave fuelled an early start for the wildfire season.

Experts say climate change is driving the shift. Weather conditions in all seasons are growing more extreme and fire activity continues to intensify, allowing fires to start earlier each spring and burn longer into the fall.

Air-quality expert Michael Brauer, a professor in the School of Population and Public Health at the University of British Columbia, said persistent exposure to smoke will pose an increasing risk to public health.

"Even if we're otherwise healthy and we're not feeling symptoms, it's this cumulative effect over the course of our lifetime that we may be facing," he said.

The health effects of smoke can be fatal and ongoing exposure to smoke every season will accelerate the progression of illnesses such as lung and heart disease, he said.

"What about a long smoke season this summer, and then next summer, and every summer thereafter? And that's really the era that we're getting into with this warming climate.

"All the suggestions that we have point to this being similar to what we know from general air pollution, which means that it leads to life-shortening. Basically, people will not live as long."

Brauer said wearing a mask, relying on air filtration systems and taking refuge in clean air shelters can all help limit exposure.

People vulnerable to smoke should prepare for each season by ensuring their medical issues are well managed before the smoke arrives, he said.

Brauer cautions that governments can no longer approach air pollution caused by wildfire as isolated events, but must be prepared to protect public health every year.

"There may come a time where we need to change the way we think of summer," he said.

"If this is really happening every year, we need to get serious about it."