For sampling, scroll pumps (Agilent, USA) were used to draw approximately 30 L min -1 through the filters until roughly 5 mg of PM2.5 was collected on each filter. The mass on each filter was estimated based on PM2.5 concentrations from the air quality monitoring stations located in the same cities as the collection sites (Figure ) and daily in-line flow meter measurements (Mass Flow Meter 4043, TSI, USA). Based on calculations using archived hourly air quality data, we estimate that the Kelowna sample had 4.5 mg of PM2.5, 88% of which was from wildfires, while the Kamloops sample had 8.1 mg of PM2.5, 96% from wildfires (Table ).