Coarse Particulate Matter Levels in Four Different B.C. Airsheds

What is particulate matter?

The term particulate matter (PM) refers to tiny (no wider than 10 micrometers) solid or liquid particles suspended in the air. Since PM pollution causes respiratory complications in humans, the World Health Organization (WHO) recommends that a yearly PM average of 20 μg/m3 or less is maintained to help minimize human health problems.

How does Cranbrook compare to other B.C. communities in terms of air quality?

ϖThe above graph illustrates a comparison of PM concentrations between Cranbrook, Prince George, Radium, and Burnaby.

ϖCranbrook levels are higher than Radium’s. This is due to the fact that even though both communities are located within valley formations in the Kootenay Region, Cranbrook’s population is larger and therefore has a larger number of PM sources

ϖCranbrook’s PM average is almost as high as Prince George’s (95 per cent), even though Prince George is heavy in industry and harbours almost four times the population of Cranbrook.

ϖCranbrook levels are higher than Burnaby’s despite the fact that Burnaby is heavy in industry and has over ten times the population of Cranbrook.

Does this mean Cranbrook has poor air quality?

Since 2004, annual PM averages in Cranbrook have been under the WHO target. However, the presence of steep valley walls surrounding the community hinders the dispersion of air pollutants like PM. Consequently, Cranbrook is more susceptible to locally- produced PM than communities like Prince George and Burnaby, which are situated in wider valleys (i.e. not surrounded by steep walls). Like many other communities within the Kootenays, Cranbrook has abundant PM sources including road dust, woodstoves and forest fires. Cranbrook also has the highest population of all Kootenay communities, which means a considerable amount of PM is generated by individual behaviour – such as idling. This has led to a higher risk of PM pollution than most other communities in the Kootenays (such as Radium). Currently, Cranbrook airshed is classified as “threatened,” but through cooperative efforts of the municipal government and programs such as the Idle-free Ambassador Program, it could reach the status of a “clean” airshed.

1/ An airshed is a mass of air that is affected throughout by a source of pollution

2/ Kootenay Region communities have sources of PM such as woodstoves and forest fires that are not common to larger Lower Mainland communities. This is the reason why PM is often a more serious problem in interior BC communities.

3/ The Ministry of Environment describes airsheds using the classifications: “clean”, “threatened”, and “degraded”.

4/ For more information on improving air quality:   http://www.env.gov.bc.ca/air/airquality/pdfs/airshedplan_provframework.pdf