In a summer of historic wildfires, Canadians have undoubtedly been checking air quality more frequently than usual.
However, the way that figure is calculated varies by province and experts say it needs to be amended to better reflect the risks and spread of wildfire smoke.
For millions of Canadians, the particulate matter that colors their summer skies gray or orange — and leads to health effects over time — isn't fully visible in the readings they see.
Here's a closer look at the problem.
How AQHI Works (and How It Doesn't)
Canada's Air Quality Health Index (AQHI) is based on three different pollutants: ozone, nitrogen oxides and particulate matter (PM2.5).
All three can be found in wildfire smoke, but there are particularly high levels of PM2.5.
Wildfires release tiny, harmful particles 2.5 microns or smaller in size — smaller than a human hair — that can enter your lungs and enter your bloodstream, adversely affecting your health.
The AQHI is on a scale of one to 10+ and is designed to give the public a sense of the risk associated with exposure.
The idea is simple: the higher the number, the higher the health risks, especially for the elderly, children and people with pre-existing conditions such as cardiovascular disease.
The original metric, still used in Ontario, Quebec and Alberta, essentially averages the risk of the three pollutants.
However, experts say AQHI does not work as effectively in cases where there is a lot of wildfire smoke and no other pollutants, as the average is lower than the risk posed by PM2.5.
For example, on the morning of August 16, Toronto had an AQHI score of four (moderate risk) even though the PM2.5 concentration was 42.6 micrograms per cubic meter, which is considered “very bad”.
Note: An 11 in this table corresponds to a 10+ on the AQHI scale.
How it was changed in BC
British Columbia, no stranger to wildfire smoke, has developed a slightly modified version of the index known as AQHI-plus.
If the PM2.5 level in that province is above the average of all three pollutants, the PM2.5 level is used to measure the overall AQHI.
The change came after a particularly severe wildfire season in 2017.
“The AQHI was not very responsive to these air quality conditions,” said Sarah Henderson, scientific director for environmental health services at the British Columbia Centers for Disease Control.
“People were in the community and realized they were being exposed to smoke. And that discrepancy between what people were experiencing and what the AQHI was telling them was problematic for us.”
Reflect a new reality
The AQHI was originally developed by the federal government to communicate about air quality risks in urban environments, where sources such as transport and industry dominate the air quality profile.
But the air quality is changing, say experts.
Regulations have helped reduce industrial and vehicle emissions, while smoke from wildfires now accounts for a larger proportion of the overall measure of poor quality.
The changes made in BC reflect this new reality, Henderson said.
“I would perhaps describe what we did in British Columbia as a stopgap until we have the necessary conversations nationally to consider what AQHI needs to look like in the future,” she said.
“We need to keep our air quality communication tools up to date as air quality in Canada is changing.”
Millions of people are under air quality warnings as wildfire smoke blankets much of Canada and the US. About That producer Lauren Bird explores how this is affecting your health — and what you can do to protect yourself.
Ontario, Alberta and Quebec do things differently
The BC approach has been adopted by most other provinces and territories, but Ontario, Alberta and Quebec have not embraced it.
Armel Castellan, alert forecaster for Environment and Climate Change Canada, said the department hoped that would change.
“They haven't quite adopted the improved AQHI yet, but it's something we're obviously in close communication with,” Castellan said.
“We're harmonizing their processes with ours and the end goal is to enforce that across the country.”
Gary Wheeler, a spokesman for the Ontario Department of Environment, confirmed that the province is working with ECCC to “expand the AQHI program to include a PM2.5 trigger, in addition to the current process that utilizes the cumulative effects of ozone and nitrogen dioxide.” become.” and particulate matter.”
Alberta, too, said it is working with ECCC on the same matter and is “evaluating the federal PM2.5 override formula for AQHI reporting.”
“There are several reasons Alberta is considering this change, including whether this formula better reflects real-world experience of wildfire smoke events and provides the opportunity for more consistent AQHI reporting and forecasting across the country,” said Carla Jones, a spokeswoman .
Quebec uses a different scale. In a statement, a spokesman for the environment ministry said the province rates air quality on a scale of one to 50+ based on the percentage of pollutants that can be encountered each day. They also consider this particulate matter separately. When asked if the province intends to adopt the federal government's new AQHI model, the spokesman did not respond.
Why it matters in the long run
Jill Baumgartner, associate professor in the Department of Epidemiology, Biostatistics and Occupational Medicine at McGill University, said that as wildfire smoke increases, accurate measurement of air quality is becoming increasingly important.
“We tend to think of wildfire smoke as an acute exposure … but the greatest health impacts come from long-term exposure to air pollution,” she said.
“As these events become more frequent, as we have witnessed this summer, this wildfire smoke will increasingly become a long-term chronic burden and these are the ones that concern us most from a health perspective.”
