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What's PM2.5 and why it is behind B.C.'s 10th consecutive day of toxic air

Saturday, September 19th 2020, 7:47 pm - The catastrophic wildfires blazing across western U.S. continues to create unhealthy air for B.C., PM2.5 are the particles that are making the air such poor quality.

Canada usually isn't on the radar for the global conversation on air quality, especially unrelenting poor air quality.

For the past 10 days, Vancouver, and other areas in British Columbia, have topped world charts for having the poorest air quality.

The cause of the plummeting air quality is the smoke coming from the historical wildfires in western areas of the U.S.

The smoke has made its way across many Canadian provinces but has stayed aloft for most areas. B.C.'s situation, however, is its own story, as thick smoke has suffocated its most densely populated cities.

Environment Canada has released air quality advisories for Vancouver for 10 consecutive days, marking the air "unhealthy."

The air pollutant is called PM2.5, which is the same "poor air quality" pollutant prevalent in some major Asian cities.


If it's science, it's going to be an acronym. So all PM2.5 stands for is Particulate Matter 2.5 micrometres or less in size. These are particles found in air such as dust, soot, dirt, smoke, and liquid droplets. One of the issues with PM2.5 is their literal microscopic size. A human hair is expansive compared to the tiny particles that live in the air.


PM2.5 is believed to be the greatest health threat to people because it can get absorbed in the bloodstream when inhaled, and it stays in the air for a long period of time.

Particulate matter can directly come from natural or manmade sources, or be a product of other pollutants reacting to each other.

Examples of sources include emissions from industrial processes such as motor, power plants, wood burning.

The fires have scorched a record 3.2 million acres (1.3 million hectares) just in California since mid-August. Another 1.7 million acres (650,000 hectares) have burned in Oregon and Washington state since Labour Day. So it's no surprise that B.C. has been suffocated with PM2.5, the byproduct of a ton of wood burning.


Air quality in B.C. has shown signs of improvement due to a pattern change currently underway. An onshore flow from the Pacific has improved air quality and visibilities to several communities, especially in low-lying, urban areas. The province is also expected to get some unsettled weather, so the expected showers will also help.

BC air quality

However, there is still significant smoke in the higher levels of the atmosphere. These levels are expected to ease later this weekend and into early next week as a broad upper-trough moves onshore, bringing slightly unsettled conditions to the West Coast, according to Weather Network meteorologist Jessie Uppal.

"Poor air quality and reduced visibility is expected through the day Saturday for parts [of] southern Alberta and Saskatchewan due to wildfire smoke. Conditions expected to improve for Alberta later tonight with an incoming low-pressure system and through the day Sunday for parts of Saskatchewan," said Uppal.

There has also been moisture in the air stateside, which has helped control the fires and the plumes of smoke.


Dr. Courtney Howard, from the Canadian Association of Physicians for the Environment, discusses the potential impacts of being exposed to PM2.5.

Thumbnail courtesy of Mark Windsor/Grand Forks, B.C.

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