No Smoking!

On June 4, 2025 Toronto’s air quality was the worst for major cities in the world.

On June 6, Montreal’s air quality was the second worst in the world.

Downtown Toronto June 4, 2025

This was due to the smoke from the large number of wildfires in western Canada. In 2023 the record breaking Canadian wildfires that blanketed much of North America originated in Alberta and BC. In early June this year, it was the intense and widespread wildfires in Saskatchewan and Manitoba that were polluting the atmosphere down through much of the American Midwest and the East Coast.

Canada experienced its worst wildfire season on record in 2023, more than double the previous record. Over 42 million acres burned, an area larger than England.

Fires happen naturally in many parts of the world. It is difficult to know if climate change has triggered a specific wildfire because other factors are also relevant, such as changes to the way land is used. But climate change is making the weather conditions that help wildfires spread more likely. Extreme, long lasting heat draws more moisture out of the soil and vegetation. These dry conditions provide fuel for fires which can spread at an incredible speed, particularly if winds are strong.

This Smoke Forecast map is an animation showing how wildfire smoke is expected to move across North America over the next 48 hours. There can be quite a dramatic change in one particular location over the course of this short period.

The light yellow to dark brown colors on the map show the measurements of fine, inhalable Particulate Matter, PM 2.5.

Pollution from wildfires is more harmful to the respiratory system than particle pollution from other causes. PM 2.5 is the air pollutant from wildfire smoke that is of the greatest concern to public health because it can travel deep into the lungs and may even enter the bloodstream. These minuscule particles can lead to breathing problems like bronchitis and cause inflammation that aggravates diabetes, heart disease and other health conditions.

Why wildfire smoke is a health concern

Some of the symptoms you might experience after breathing air polluted with wildfire smoke are scratchy or sore throat, coughing, watery or irritated eyes, shortness of breath, runny nose and nasal congestion.

For most healthy people, occasional exposure to moderate wildfire smoke when the Air Quality Index (AQI) is 50–100 (color coded yellow), does not pose a long term risk. However, frequent or extended exposure, especially for sensitive groups, may contribute to cumulative effects on respiratory and cardiovascular health. 

AQI over 100 can have serious long term health effects.

AQI over 200 indicates serious, immediate health risks. Even short term exposure can cause acute symptoms.

The Smoke Forecast provides a good overall picture and you can zoom in to particular locations. But a better way to monitor your own location is the IQAir website. It shows the current air quality, plus weather and the forecast for the next 7 days.

There is also a smartphone app IQAir which is more convenient as it pops up alerts when the air quality exceeds a certain amount or when it improves to a certain level.

🔍What can I do?

The Air Quality Index site and app will actually provide recommendations depending on the air quality index. For example, when the air quality is rated moderate, for people with health issues or the elderly it recommends using a KN95 mask outdoors and reducing outdoor exercise. When indoors, it recommends closing your windows and running an air purifier.

To remove wildfire smoke, you need an air purifier that can remove fine particulate matter (PM 2.5) and Volatile Organic Compounds (VOCs), the two main harmful components in wildfire smoke. Look for these features in an air purifier.

True HEPA Filter (High-Efficiency Particulate Air)
→ Captures at least 99.97% of particles as small as 0.3 microns. This includes smoke, ash, and other fine particles. PM 2.5 (particles ≤2.5 microns) is well within this range.

Activated Carbon Filter
→ Removes odors and gases including VOCs emitted during wildfires.
→ Essential for eliminating the smell of smoke and reducing exposure to chemical pollutants.

Installing a HEPA filter system that can purify all the air in a house is quite expensive. However a good room air purifier can be purchased for around $300. 

As an example, I use the following air purifier in my bedroom. A nice feature of this model is that besides the basic carbon filter, there is an option to get filters for intense smoke, allergens and pet hair. You need to remember to clean the filters regularly as they collect a lot of dust and replace the filters according to the manufacturer specifications.

Be prepared! 

The 2025 Canadian wildfire season is shaping up to be exceptionally severe, with record early burn rates, rising summer heat and dryness. Expect a long, dangerous fire season stretching well into autumn, with recurring smoke hazards spanning the continent.