HEPA Air Filters for Preventing Wildfire-related Asthma Complications, a Cost-Effectiveness Study

Air pollution caused by wildfire smoke is linked to adverse health outcomes, especially for people living with asthma. We studied whether government rebates for high-efficiency particulate air (HEPA) filters, which reduce smoke particles indoors, are cost-effective in managing asthma and preventing exacerbations in British Columbia (BC), Canada.A Markov model analyzed health states for asthma control, exacerbation severity, and death over a retrospective time-horizon of 5 years (2018-2022). Wildfire smoke-derived particulate matter (PM2.5) from the CanOSSEM model and relevant literature informed the model. The base case analysis assumed continuous use of the HEPA filter. Costs and quality-adjusted life-years (QALYs) resulting from varying rebates were computed for each Health Service Delivery Area (HSDA).In the base case analysis, HEPA air filter use resulted in increased costs of $83.34 (SE=1.03) and increased QALYs of 0.0011 (SE=0.0001) per person. Average incremental cost effectiveness ratio (ICER) among BC HSDAs was $74,652/QALY (SE=3,517), with ICERs ranging from $40,509 to $89,206 per QALY in HSDAs. Across the province, the intervention was projected to prevent 4,418 exacerbations requiring systemic corticosteroids, 643 emergency department visits, and 425 hospitalizations during the 5-year time horizon. A full rebate was cost-effective in one of the 16 HSDAs across BC. The probability of cost-effectiveness ranged from 0.1% to 74.8% across HSDAs. A $100 rebate was cost-effective in most HSDAs.Our results indicate variable cost-effectiveness of HEPA filters in managing wildfire smoke-related asthma issues in BC. The effectiveness of government rebates varies by region but rebates up to two-thirds of the filter cost generally appear cost-effective, with a full rebate only cost-effective in Kootenay Boundary.