The Co-occurrenceof Wildfire Smoke and Extreme HeatEvents in British Columbia, 2010–2022: Evaluating SpatiotemporalTrends and Inequities in Exposure Burden

Climate change is fueling more frequent and severe wildfire smoke (WFS) and extreme heat events (EHEs), and co-exposure may have synergistic adverse health effects. We evaluated the spatiotemporal trends in population exposure to co-occurring WFS and EHEs (WFS-EHEs) in British Columbia (BC). We calculated the frequency, intensity, and trends in WFS-EHEs in each census dissemination area (DA) in BC between 2010 and 2022. WFS-EHEs were identified using established exceedance thresholds and daily data on fine particulate matter, smoke plumes, and meteorological conditions. Trends were identified using the Mann–Kendall and Theil–Sen approaches. Census data was used to identify the characteristics of the most exposed communities. Over 13 years, there were 276,666 DA-level WFS-EHEs, impacting all BC residents and leading to a cumulative 170.8 million person-days of exposure. Although there was substantial year-to-year variability, the frequency and intensity of WFS-EHEs increased over time, with 60.8% of co-occurrences between 2018 and 2022. 42.5% of DAs (∼1.9 million people) experienced significant increases in exposure. The highest co-exposure burden occurred in rural communities with lower adaptive capacity. Our findings demonstrate the need for public health guidance on these increasingly frequent and intense compound hazards and can inform climate change adaptation and mitigation efforts in BC and elsewhere.