The AQHI downplays exposures from particulate pollution

By -
How much is a human life worth? If you live in rural British Columbia or in resource-based communities like Kamloops you may be surprised to learn that your life is worth far less than someone from Vancouver or Victoria.

Recent forest fires in the interior of BC, and the massive amounts of wood smoke produced, demonstrate how risk communication tools like the Air Quality Health Index (AQHI) are designed to treat differentially exposures across populations.

The AQHI is a scale used in Canada to weigh the relative contribution of three air pollutants; namely, particulate matter in the 2.5 micron range (PM2.5), ground level ozone, and nitrogen dioxide. It normally ranges between 1-10 or from “low” to “very high” health risk but can reach numbers like 49 as was recorded on August 3, 2017, in Kamloops.

The formula used for calculating the AQHI is straightforward and it involves using a three-hour average for these pollutants in micrograms/m3 for PM2.5, and parts-per-billion (ppb) for ozone and nitrogen dioxide. A weight is assigned to each of these pollutants based on observed adverse health outcomes.

In BC, the air quality objective for PM2.5 (24-hour average) is 25 micrograms/m3. With recent forest fires, numbers have been in the 150-200 range for several consecutive weeks.

The AQHI is mathematically flawed and out of line with these objectives. It downplays the significance of PM2.5 exposures and it generates low AQHI levels when air pollution risks from PM2.5 are actually high.

For example, a community exposed to no nitrogen dioxide, no ozone, and 100 micrograms/m3 of PM2.5 pollution yields an AQHI of 5, or “moderate risk.”  This is actually a staggering amount of pollution yet the risk messaging is tempered and muted. It would take 400 micrograms/m3 of PM2.5 with this scenario to hit a 10 on the AQHI. China issues “red alert” warnings when 24-hour averages exceed 150 micrograms/m3.

The AQHI poorly protects people in rural and resource-based communities from particulate pollution, and it seems designed more for urban environments where ozone and nitrogen dioxide pollution are more common. As a result, this tool exposes us to higher levels of risk.




Michael D. Mehta, Ph.D. (August 8, 2017) 

Comments

Post a Comment

Popular posts from this blog

Press release - Wood Smoke is a Serious Health Hazard

By -
FOR IMMEDIATE RELEASE: Wood Smoke is a Serious Health Hazard (April 6, 2017, Vancouver, British Columbia)— Vicki Morell feels like a prisoner in her own home. And she warns that if it happened to her and her family, it can happen to you too.  The misery began 12 years ago when wood smoke from a neighbour’s fireplace began to permeate the Morell family’s home. The smoke gives Morell headaches and causes burning eyes and other health effects. “My wood-burning neighbours have told me that it is their right to burn wood,” said Morell. "But what about my right to breathe fresh clean air in my own home? I don’t understand why the right to burn wood outweighs another’s right to breathe clean air.” Morell used to think that closing windows would keep out the wood smoke, but she soon discovered that she was wrong. Wood smoke particles are far smaller than the width of a human hair — so tiny that, research has shown, the insides of nearby houses can wind up having ...
Read more

Clean "country" air is an illusion

By -
Image
If you moved to the "country" for clean air and a healthy lifestyle it's time to rethink things. Right now air quality on Gabriola Island is mosty in the warning zone due to wood burning appliances like woodstoves and fireplaces with air quality readings of over 100. By contrast downtown Vancouver at rush hour is in the 50s and downtown Victoria is in the teens.
Read more

How to understand PurpleAir sensor readings

By -
Image
Air pollution has a unique signature depending on the source or sources, location, baseline, magnitude of change, and the mechanisms by which it is produced. He re are some simple ways to identify what's happening when reading PurpleAir monitors like what we have  here . The first image is from a rural community. Note the good quality air with PM2.5 levels between 1 and 2 with a sudden but short-lived spike to 7.5 at 11:15AM. This is a pattern I have seen before and it represents a dirty diesel truck (most likely a water truck) going past the sensor. The second image represents normal variation on a good air quality day.  The third image is from a city with the sensor reflecting activity from a local pulp and paper mill and local traffic. The last image is a rural community snapshot of a good day punctuated by what happens when a wood stove or fireplace is lit nearby. Note the sudden and dramatic increase in pollution and the saw tooth pattern as the stove ge...
Read more