The association between wildfire emitted PM2.5 and hospital admissions in the greater Seattle area

Abstract

Short-term exposure to wildfire particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) has been associated with increases in respiratory and cardiovascular hospital admissions. Inconsistent results among studies suggest that there may be regional differences due to chemical variability in wildfire-generated PM2.5. The present study looked at how PM2.5 concentrations were associated with respiratory, cardiovascular and cerebrovascular hospital admissions in the greater Seattle area (GSA). The study period covered 11 years from 2007-2017 throughout the fire season (June 1– October 1) and specific days with wildfire smoke. Daily PM2.5 measurements were obtained from a tapered element oscillating microbalance (TEOM) PM2.5 monitor located in Seattle-Beacon Hill to estimate exposure concentrations throughout the GSA. Generalized linear models were created using 3rd degree B-splines to estimate the relative risk (effect estimates) of daily hospital admissions for respiratory, cardiovascular and ischemic stroke diagnoses for all ages and for older adults (≥ 65). All-cause respiratory hospital admissions increased by 5.0% (95% Confidence Interval (CI) 1.3% - 8.9%) for all ages and ischemic stroke admissions increased by 4.4% (0.9% - 8.0%) for older adults (≥ 65) for every 10 μg/m³ increase in PM2.5 during the fire season. Adults aged ≥ 65 showed no increases for all-cause respiratory or all-cause cardiovascular diagnoses during the fire season. Cardiovascular diagnoses and ischemic stroke showed null associations during wildfire smoke days. Respiratory morbidity was pronounced for wildfire smoke days, with significant increases in hospital admissions for children ages 0-19. Whereas many similar studies have looked at wildfire smoke episodes that frequently exceeded the U.S. Environmental Protection Agency’s (EPA) federal PM2.5 regulatory standards, few have looked at lower concentrations. This study found that hospital admissions for respiratory diagnoses in the GSA significantly increased during periods of wildfire smoke, even though the EPA’s PM2.5 standards were infrequently exceeded. These results suggest that increased exposure to wildfire smoke could result in lower quality of life, reduced labor productivity, and increases in health costs in the GSA.