Air quality concerns skyrocket as B.C. wildfire smoke drifts

Thursday, July 20, 2017, 9:57 AM - As the wildfire crisis in British Columbia enters its third week, a lingering trough over western Canada is driving a westerly flow, allowing thick smoke and haze to spread into the Prairies with air quality advisories extending into Saskatchewan.

New B.C. Premier John Horgan extended the state of emergency by two weeks. Initially, it was set to expire at midnight Friday. However, there are no signs of wildfire activity slowing down.

Over 100 wildfires larger than 0.01 hectares continue to burn across the province. On Monday, air quality advisories stretched from the entire B.C. interior through to parts of Manitoba, though by Wednesday morning, they had been pulled back to Alberta.

"Due to the smoke, the AQHI (Air Quality Health Index) will likely reach above 10, or very high risk, in parts of western and central Alberta tonight," said Environment Canada Wednesday afternoon. "There is some uncertainty as to where the thickest smoke will set up, but current indications are that the corridor of thickest smoke and thus poorest air quality will be between Hinton, Red Deer, and Edmonton."

The smoke is expected to remain over western and central Alberta until at least Thursday afternoon or evening, when thunderstorms may flush out some of the smoke, added the weather agency. 

Based on satellite imagery, smokey skies have spread over much of western Canada. Outside of the B.C. Interior, the smoke is mainly showing up as a light haze, but thicker smoke has been spotted moving across the Prairies into Manitoba, and one swath was even visible over the western Great Lakes on Monday.

Air Quality Impacts

The smoke inundating the B.C. Interior has been driving Environment Canada's Air Quality Health Index (AQHI) into the extremes.

On Monday, the AQHI in Kamloops reached 10+ (Very High Risk, the maximum level of the index) for 9 hours straight. Meanwhile, in Williams Lake, the AQHI only dropped down out of the 10+ range for two hours around midday, before climbing back above 10 and remaining there for the rest of the day, overnight.

Many other communities in the region were at 7 (High Risk) AQHI, while smoke drifting across Alberta and Saskatchewan pushed values up into the Moderate Risk (4-6) range there.

Elevated AQHI levels seen across Canada can usually be traced to human-caused factors, namely smog - the soupy combination of ground level ozone and fine particulate matter that can linger for days due to the presence of hot, humid, stagnant weather conditions. Ozone, when produced high in the stratosphere, is good for us and other forms of life on the planet, as it protects us from exposure to harmful ultraviolet rays from the Sun. At ground level, however, ozone forms when gases known as nitrogen oxides (NOx) react with volatile organic compounds (VOCs) in the presence of sunlight, and ground-level ozone acts as an irritant to lung tissues. Fine particulate matter is anything from smoke to ash to dust to pollen, and is dangerous all on its own, but even more so when combined with the lung irritation caused by exposure to ozone.

Children, the elderly, and those with lung and heart conditions are particularly vulnerable to exposure to smog, as are those who are exposed for extended periods of time, or who perform strenuous activity outdoors during elevated concentrations.

Even without the presence of ozone, wildfire smoke can still present a considerable health risk, especially to those identified as vulnerable, above. Environment Canada adds that during heavy smoke conditions, everyone is at risk, not just the most vulnerable.

Also, studies have shown that wildfire smoke may be causing higher levels of ground level ozone as the smoke drifts over urban areas, possibly due to the presence of volatile organic compounds in the smoke. Although artificial sources of VOCs (industry and transportation, mainly) are responsible for most smog episodes, since living trees naturally release VOCs into the air during their daily cycle, these same chemicals may be carried along with the ash and smoke particles as they drift on the wind.

With wildfires continuing in B.C. and the smoke drifting into central Alberta and beyond, check The Weather Network website for your city's air quality report.

SOURCES: NASA Earth Observatory | NASA Worldview | Firesmoke.ca | Environment Canada