In the Cowichan, the air contaminant of greatest concern is PM2.5, which refers to particulate matter that is less than 2.5 microns in diameter. This contaminant can travel deep into the lungs and become lodged there, causing heart and lung disease, and premature death.
Air quality data for the Cowichan region indicate that there are occasional exceedances of the provincial PM2.5 objectives from 2009 to 2015. Exceedances were primarily due to local open burning and wood burning appliances (winter), and forest fires located in other regions (summer). It has been estimated that 77% of the total PM2.5 in the Region is coming from area sources. Open burning accounted for 53% of the total PM2.5 and wood burning appliances accounted for 23% of the total PM2.5.