Wildfires and the Changing Landscape of Air Pollution-Related Health Burden in California
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Rationale: Wildfires are a growing source of fine particulate (PM2.5) pollution, but associated trends in health burden are not well characterized.Objectives: We investigated trends and disparities in PM2.5-related cardiorespiratory health burden (asthma, chronic obstructive pulmonary disease, and all-cause respiratory and cardiovascular emergency department (ED) visits and hospital admissions) for all days and wildfire smoke-impacted days across California, 2008-2016.Methods: Using residential ZIP code and daily PM2.5 exposures, we estimated overall- and subgroup-specific (age, gender, race/ethnicity) associations with cardiorespiratory outcomes. Health burden trends and disparities were evaluated based on relative risk, attributable number, and attributable fraction by demographic and geographic factors and over time.Measurements and Main Results: PM2.5-attributed burden steadily decreased, whereas the fraction attributed to wildfire smoke varied by fire season intensity, comprising up to 15% of the annual PM2.5-burden. The highest relative risk and PM2.5-attributed burden (92 per 100,000 people) was observed for respiratory ED visits, accounting for 2.2% of the respiratory annual burden. Disparities in overall morbidity in the oldest age, Black, and “Other” race groups were also reflected in PM2.5-attributed burden, whereas Asian populations had the highest risk rate in respiratory outcomes and thus the largest fraction of the total burden attributed to the exposure. In contrast, high wildfire PM2.5-attributed burden rates in rural, central, and northern California populations occurred due to differential exposure.