Using the average is dangerous and irresponsible when it comes to air pollution exposures from wood stoves

When it comes to air pollution, there seems to be special "rules" for how it is measured that doesn't reflect true risk or scientific evidence.

Averaging exposures over longer periods of time ignores hundreds of scientific and medical studies on the significant and often irreversible impacts associated with short-term, acute exposures to high levels of air pollution. Yet, regulators and others usually ignore these effects and exposures.

This approach involves using 24-hour and annual averaging which works somewhat when you believe that the airshed is a uniform and homogenous thing. This model is designed for urban areas where industrial pollution is more common, but in rural communities this approach understates the risks from wood burning for home heating and other purposes.

Wood burning creates hyperlocal air pollution and the nature of this combustion process leads to rapid increases in PM2.5 pollution. PM2.5 sized particles are the most dangerous air pollutant, and short and long term exposures are definitively linked to cancer, lung disease, heart attack, stroke, and many other things. They are also next to impossible to avoid if a neighbour burns wood, and the particle size allows this air pollution to easily enter houses even when every window and door is closed.

Imagine if we used the same approach for noise. We know that noise exposure can also have many health impacts.

Picture this... you live in a quiet rural community with little traffic and no industry. The sweet sound of birds punctuate the air from time to time and you are lulled to sleep by waves.

The normal level of noise in this environment is probably around 30 dB - just above a quiet whisper. All of a sudden a neighbour begins using a jackhammer with an extremely loud and unhealthy rating of 120 dB. At this level, health effects are guaranteed if one doesn't protect themselves. This jackhammering goes on for 8 hours/day. The daily average would be 60 dB which is the same as a busy street.

Would the averaging approach make sense here? Clearly not, yet it is used for air pollutants like PM2.5.

Here's a real example from one of our sensors on Gabriola Island from April 14, 2020, where the temperature in the evening was in the 11C range.

This location has extreme levels like this all the time and for at least 9 months/year, and 178 micrograms/m3 of PM2.5 is similar to what we would see in a wildfire.

In fact, at the time this measurement was taken this location had the second worst air pollution in North America. At 10:22PM the reading was 126 micrograms/m3. The World Health Organization recommends less than 10 and studies show that health impacts begin once 5-6 micrograms/m3 are reached.

All on this small island where every property has access to electricity.

Here's where the issue of average comes into play. Take a look at the following chart from this sensor.

You can see an 8 hour + period of time when the air pollution from wood stoves in the area created extremely high and dangerous levels of air pollution. This is heart attack, asthma attack, stroke-inducing air pollution.

The horizontal line shows a figure of 6.5 micrograms/m3. This is the average over several days and it falls within guidelines.

This is how averaging obscures and distorts the real risk generated by wood burning. It is a deceptive, medically and scientifically indefensible approach, yet is still dominant in the regulatory world.

This must change.


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