Summary

• On Wednesday, Toronto’s air quality was the worst in the world, as wildfire smoke from northern Ontario blanketed the city. 
• Research suggests even moderate levels of wildfire smoke can pose significant health risks.
• The federal government uses the Air Quality Health Index to communicate the severity of air pollution. The higher the index score, the more precautions people — especially those with health conditions — should take to stay safe and comfortable.

On Tuesday, Sol Mamakwa was driving to Thunder Bay, Ont., sunshine behind him, darkness ahead. 

The Ontario NDP MPP represents the large, remote northwestern Ontario region that is currently burning at extreme rates. More than 100 active wildfires in his riding have displaced six communities so far, and put dozens more under threat as temperatures reached close to 40 C on July 15.”

Meanwhile, choking smoke from these fires has spread more than 1,000 kilometres away, making Toronto’s air quality one of the worst in the world. (On Wednesday, it was even the worst in the world and hospital visits are on the rise.) 

Ontario is not the only province burning. Per the Canadian Wildland Fire Information System, 858 active forest fires across the country have impacted 2.4 million hectares to date; 111 of these fires are considered out of control. Such wildfires are fuelled by warmer-than-average temperatures and drier conditions which make forests more prone to burning and lead to fires spreading faster and further. 

This year, there have already been 483 wildfires recorded inside Ontario’s fire region, compared to 351 last year and the 10-year average of 320. The number of fires has been climbing sharply, with 31 new fires discovered in a single day earlier this week.

“It’s eerie to be in my part of Ontario right now,” Mamakwa told The Narwhal. “The situation is unprecedented, and it’s getting worse.”

As the number of wildfires grows, so do the health risks of smoke, which is more toxic than normal pollution as it can linger in the air for weeks and travel thousands of kilometres. 

“Wildfires in my region have gotten worse and are getting worse,” Mamakwa said. “It needs to be treated like the emergency it is. Every possible measure needs to be taken to keep our communities safe.” 

Here are some things you need to know.

Wildfire smoke may increase health risks

Wildfire smoke continues to cloud much of Ontario, forcing people to stay inside as much as possible. 

This kind of smoke has three main ingredients. There are gases, such as carbon dioxide and sulphur dioxide, and volatile organic compounds, like benzene, toluene and butene. There is also particulate matter, which can include soot, dust, pollen and spores, as well as chemical particles. The particles are classified according to size and fine particulates — the really tiny ones, less than 2.5 microns in diameter and typically referred to as PM2.5 — pose the greatest threats to human health because they can travel deeper into the lungs than larger ones.

The more particulates in the air, the hazier it becomes. Extremely poor air quality due to wildfire smoke is hard to ignore, often resulting in new reports and public health warnings to stay indoors and take precautions.

Research suggests even moderate levels of wildfire smoke can pose significant health risks, especially for people with chronic lung diseases like asthma or emphysema that make them more vulnerable to negative health impacts. Fine particulates found in smoke and other types of air pollution have been linked to damage in several organ systems, including the heart, brain and reproductive system.According to a study by the Canadian Climate Institute, long-term exposure to increased toxic wildfire smoke is associated with an estimated 2,500 premature deaths annually in Canada. The study found wildfire smoke caused an estimated total of $5.3 billion in acute health damages between 2014 and 2025.

Most air quality advisories in Canada are now the result of wildfires, not other pollution

Wildfires are now the most common reason for air quality advisories, which are issued when concentrations of particulate matter and hazardous gases rise to levels that can negatively impact human health.

To help Canadians understand the health risks stemming from current air conditions, authorities use the Air Quality Health Index (AQHI), a colour-coded scale of one to 10 (with a plus sign if it’s off the charts), based on concentrations of ozone, particulate matter and nitrogen dioxide — the pollutants found to have the greatest health impacts. 

The higher the health index score, the greater the risk and the more precautions people — especially those with health conditions that make them vulnerable to poor air quality — may need to take to stay safe and comfortable. Avoiding polluted air by staying inside and using air purifiers is the most effective protection but avoiding strenuous outdoor activity and wearing a respirator can also help.

Small amounts of wildfire smoke also come with long-term health risks

At the University of British Columbia, physician Chris Carlsten is leading an effort to shed light on how wildfire smoke affects human health over the short and long term. His team was recently awarded a federal grant to support its work.

Carlsten said the team is focusing on chronic exposure to any amount of wildfire smoke versus acute exposure to high levels, even though the short-term peaks are “problematic.” 

“There may be more health effects, ultimately, from the more common but lower-concentration exposures,” Carlsten said in an interview. The team will also explore how wildfire smoke affects people differently based on age, sex, genetics, exercise habits and socio-economic status.

Better data will help improve public health policy and planning when wildfires flare, allowing people to make more informed choices about how to reduce their risk.

The Narwhal’s reporters are telling environment stories you won’t read about anywhere else. Stay in the loop by signing up for our free weekly dose of independent journalism.