Abstract Body (Do not enter title and authors here): Background: Wildfire smoke (WFS) events pose hazard to cardiopulmonary (CPM) health, and are expected to increase in intensity and frequency. In June 2023, western Canadian WFS drifted >2,000 miles to the Eastern US, resulting in an 18% state-wide increase in CPM disease clinical encounters across the University of Maryland Medical System (UMMS). This observation supports proactive strategies that mitigate WFS-associated disease burden; however, data on healthcare-associated cost of WFS exposure are needed to build effective resource deployment methods.

Hypothesis: If there was a higher CPM clinical encounter burden in association with the 2023 Canadian WFS event, then we will identify significantly increased healthcare costs.

Methods: We analyzed our previously published data identifying N=6 “hotspot” days when air quality in Maryland exceeded toxic levels due to Canadian WFS during June 2023. Using a two-part regression model and a Monte Carlo simulation, we quantified costs of increased CPM clinical visits during the 6 hotspot days in June 2023 vs. control days in 2019+2018.

Results: During the N=6 hotspot days, we modeled increased costs of cardiopulmonary disease as $2,265,565 (95% credible interval [CrI]: $341,565-$4,275,182), of which $2,065,019 ($305,384-$3,892,125) (91.1%) was due to direct medical costs and $200,546 ($33,306-$383,057) (8.9%) was due to indirect costs. In a 10-year projection model of cardiopulmonary disease costs from future wildfire events, we estimated the direct and indirect costs for 5 future wildfire events of $9,205,805 ($1,361,394-$17,351,002) and $894,031 ($148,478-$1,707,659), respectively, and for 15 future wildfire events as $27,082,023 ($4,005,008-$51,043,904), and $2,630,097 ($436,798-$5,023,665), respectively. Modeling dissemination of N95 respirators to high risk patients at 95 % efficiency projected a cost reduction of 7,156,848 ($1,078,993-$13,505,164) if 15 potential future wildfires within the next 10 years.

Conclusion: The estimated healthcare cost burden caused by increased CPM disease burden in Maryland occurring in association with Western Canadian WFS over a 6 day period was ~$2M. Our prediction models also anticipates a major adverse economic impact of future WFS events, ranging $9M-27M when considering events of similar magnitude as included in this study. These data emphasize the need for preventative action to reduce future WFS-associated healthcare burden and consequent economic cost.