Global Courant
The wildfire smoke that has hovered over parts of eastern Canada and the US this week has led many to look at charts and numbers to get a feel for the air quality in their area.
But what exactly do these indexes measure and how should they be interpreted?
Different countries have different ways of measuring air quality, including Canada, said Dan Westervelt, an associate professor at Columbia Climate School’s Lamont-Doherty Earth Observatory.
There is some variability between the indices used by countries, but he says they generally measure similar elements in the air.
Here’s a quick introduction.
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How does Canada measure air quality?
Canada uses the so-called Air Quality Health Index (AQHI)a measurement designed to make it easier for the public to understand the level of risk involved.
There are 286 measurement sites in a total of 203 communities across the country, the federal government.
The index measures health impacts related to air pollution on a simple scale of one to 10+, with 10 and anything above being the worst. The AQHI takes into account the following pollutants: ground-level ozone, particulate matter and nitrogen dioxide. All three were found in the smoke from wildfires.
How do I read the scale?
The index is designed to inform the public about the “health risk from air pollution on any given day,” according to Health Canada.
Anything between seven and ten is considered “high risk.” At that time, Environment Canada advises the public to reduce strenuous outdoor activities.
A reading above 10 is considered “very high risk”.
In those circumstances Environment Canada advises and recommends that the general population reduce or reschedule strenuous outdoor activities at-risk populationssuch as young children, seniors, and people with chronic conditions, avoid strenuous activities altogether.
You can find the air quality level in your area here.
Why are US numbers in the hundreds?
The US uses a different scale of measurement, with a much wider range. The Air Quality Index (AQI) is based on air quality standards and is measured from 0 to 500. The higher the value, the greater the air pollution.
The AQI measures particulate matter pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide. All of these are also found in the smoke from wildfires.
An AQI value of 50 or lower indicates good air quality, while an AQI value above 300 indicates hazardous air quality.
On Wednesday, AQI readings topped 400 at times in Syracuse, New York City, and Pennsylvania’s Lehigh Valley. On an average day in recent years, New York City’s AQI has remained below 50, or “good.”
Those numbers, and the eerie photos of blurry American landmarks, have sparked an unusual amount of interest in a subject that is rarely held in high esteem.
“The amount of coverage and news over the past few days in New York and D.C. and all these major cities has been really, really unprecedented,” Westervelt said, noting that he couldn’t remember the air quality index ever before being a topic of discussion. on CNN.
“I think these stories can be a little fleeting at times, but the fact that this has hit New York City so badly and so hard I think will be a motivating factor that can get people involved and more willing to take action on the air. quality.”
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What about PM2.5?
The tiny particles that result from wildfires are a concern for health experts. Both AQI and AQHI measure the amount of particulate matter with a diameter of 10 microns or less.
PM2.5 is even smaller, measuring 2.5 microns or less in diameter – that’s about 30 times smaller than the diameter of a human hair.
At that size, the particles can potentially be inhaled deep into the lungs and into the bloodstream, causing particular problems for people with underlying conditions, said Dr. Samir Gupta, a respiratory specialist and associate professor of medicine at the University of Toronto.
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What can you do to stay safe?
Environment Canada says air quality and visibility from wildfire smoke can vary over short distances and from hour to hour, and is advising the public to monitor air quality in their area.
If levels are high, you may want to adjust your behavior. This may mean choosing not to exercise outside or staying indoors with doors and windows closed and a air purifier run.
If you need to spend time outdoors when AQHI is high, experts say wearing a properly fitted N95 mask can help.
Metropolitan Transportation Authority employee Shanita Hancle, left, hands out N95 masks to commuters at the entrance of a New York City subway station on Thursday. Air pollution from wildfires in Canada blankets much of the northeastern US for a second day. (Seth Wenig/The Associated Press)
Chris Carlsten, professor and chief of respiratory medicine at the University of British Columbia, had a simple suggestion: Follow public health guidelines and use your own common sense.
“People are all different, ages are all different, circumstances are all different,” he said. “It’s a combination of these guidelines, but also learning one’s own individual tolerance based on experience.”
A more detailed set of recommendations on what to do can be found here.
