Air pollution in the CVRD: where’s it from?

Editor’s Note: This article is the fifth in a series the Citizen will be publishing in partnership with the provincial Ministry of the Environment and the Cowichan Valley Regional District about the importance of clean air the effects of pollution.

In the Pacific Northwest, the air we breathe is usually much cleaner compared to some parts of the world, but even here air quality can be an issue.

Traffic, industry, open and backyard burning, home and commercial heating – each of these activities produces a long list of pollutants, often the same ones. Under certain weather conditions, or if you live close to a source, you may have higher exposure to pollution than others.

In Canada, most of the focus is on managing sulphur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), ground-level ozone (O3), and particulate matter (PM). Even though there are many more pollutants of concern, many contribute to or are part of what makes up PM, and monitoring fine particulate matter (PM2.5) is a good overall indicator.

A few months ago, an emissions inventory was completed for the Cowichan Valley Regional District, which estimates how much SOx, NOx, CO and PM2.5 are produced by the most common sources

The pulp and paper industry produces 99 per cent of the SOx in the CVRD, 27 per cent of the NOx, 10 per cent of CO, and 17 per cent of PM2.5.

Heating and open burning emit nine per cent of the NOx, 30 per cent of CO, and 77 per cent of PM2.5.

Traffic, including on and off road vehicles, aircraft and marine vessels, puts out 64 per cent of NOx, almost 70 per cent of CO, but only six per cent of PM2.5.

It is a complex mix – different sources are responsible for varying amounts of each pollutant – but looking at measured levels in comparison to guidelines helps identify priorities for air quality management.

It is no surprise that the pulp and paper industry emits virtually all of the SOx in the CVRD, as there are no other significant sources in the region. Sulphur dioxide (SO2) is a harmful component of SOx, and data for 2011-2013 (29,000 hours) at the Crofton Escarpment station show that 99.9 per cent of the time, SO2 levels fall with the "good" category established by Vancouver Island Health Authority. Only three hours were in the "unhealthy for sensitive groups" category.

Measured levels of NOx, CO, and O3 in the CVRD are always well below provincial and federal guidelines.

PM2.5 levels in the CVRD are more concerning. The provincial 24-hour guideline of 25 micrograms/cubic metre is typically exceeded every year in the fall and winter in the Duncan area. The past four heating seasons (October – February) have seen at least 10 days above the guideline, with a high of 23 days in 2011-2012. For this heating season, four days have been higher than the guideline so far. Since 2010, only one day outside of the heating season – Aug. 5, 2010, has been above the guideline due to regional wildfires. Given that backyard burning and wood heating produce 77 per cent of the PM2.5 in the CVRD, and that most of the emissions are close to homes and people, managing these sources can make a big difference in local air quality.

More on common air pollutants: CVRD Emissions Inventory: cowichan_valley.pdf Visit the Island Health (VIHA) website for more information on SO2: sulphur_dioxide_monitoring.htm Eleanor Setton is a research scientist at the University of Victoria. Contributions were also made by the Cowichan Valley Regional District and the B.C. Ministry of Environment.