Cardiopulmonary hospitalization risks from wildfire and non-wildfire PM2.5 in 20 US states

Abstract Importance Given the increasing wildfire activity in the US, assessment of the health impacts of wildfire-specific fine particulate matter (PM 2.5 ), a growing source of surface air pollution, and its relative toxicity compared to non-wildfire PM 2.5 is needed to support mitigation strategies. Objective To investigate associations of long-term exposure of wildfire-specific and non-wildfire PM 2.5 with cardiopulmonary hospitalization risks. Design, Setting, and Participants We obtained over 89 million cardiopulmonary hospitalizations for residents across 20 US states from 2006 to 2019 from the State Inpatient Databases. We assigned estimated 2-year average concentrations of wildfire-specific and non-wildfire PM 2.5 to each hospitalization based on residential ZIP codes to characterize exposure levels. We used a self-controlled design, which is robust to unmeasured confounding, to assess the associations. Exposures 2-year moving average exposures to wildfire-specific and non-wildfire PM 2.5 from the year of hospitalization to the prior year. Main Outcomes and Measures The hospitalizations for cardiovascular (ischemic heart disease, cerebrovascular disease, heart failure, arrhythmia, other cardiovascular diseases) and pulmonary diseases (acute respiratory infections, pneumonia, chronic obstructive pulmonary disease COPD, asthma, other respiratory diseases) were identified based on the first 3 diagnosis codes at discharge. Results Wildfire-specific PM 2.5 had stronger effects than non-wildfire PM 2.5. Specifically, each 1-µg/m 3 increase in 2-year wildfire-specific PM 2.5 was significantly associated with increased hospitalization risks for all cardiopulmonary diseases, with relative risk ranging from 1.100 (95% CI: 1.091, 1.108) for heart failure to 1.160 (95% CI: 1.142, 1.178) for asthma. In comparison, a 1 µg/m 3 increase in non-wildfire PM 2.5 was associated with increased hospitalization risks for all cardiopulmonary diseases, but with relative risks ranging from 1.047 (95% CI: 1.042, 1.051) for COPD to 1.085 (95% CI: 1.082, 1.088) for hypertension. Stronger effects of both wildfire-specific and non-wildfire PM 2.5 were observed among minorities, individuals with obesity or diabetes, and those living in metropolitan areas, those with fewer years of education, and more deprived communities. Conclusions Long-term exposure to wildfire-specific PM 2.5 poses a greater risk of cardiopulmonary hospitalization than PM 2.5 from non-wildfire sources. Greater effort should be placed on wildfire management, with particular focus on strategies to reduce smoke in addition to traditional air quality control strategies. Key point Questions Does long-term exposure to fine particulate matter from wildfire and non-wildfire sources affect the risk of cardiopulmonary hospitalization differently? Findings Based on over 89 million hospitalization records for the residents of 20 US states from 2006 to 2019, exposure to fine particulate matter from wildfire was associated with a greater risk of cardiopulmonary hospitalization, compared to those from non-wildfire sources. Meaning Fine particulate matter from wildfire sources poses a greater health threat than those from non-wildfire sources; greater effort should be placed on wildfire management in addition to relying solely on traditional air quality control strategies.