Health Impact Assessment of PM(2.5) attributable mortality from the September 2020 Washington State Wildfire Smoke Episode

Major wildfires that started in the summer of 2020 along the west coast of the U.S. have made PM(2.5) concentrations in cities in this region rank among the highest in the world. Regions of Washington were impacted by active wildfires in the state, and by aged wood smoke transported from fires in Oregon and California. This study aims to assess the population health impact of increased PM(2.5) concentrations attributable to the wildfire. Average daily PM(2.5) concentrations for each county before and during the 2020 Washington wildfire episode were obtained from the Washington Department of Ecology. Utilizing previously established associations of short-term mortality for PM(2.5), we estimated excess mortality for Washington attributable to the increased PM(2.5) levels. On average, PM(2.5) concentrations increased 91.7 μg/m(3) during the wildfire episode. Each week of wildfire smoke exposures was estimated to result in 87.6 (95% CI: 70.9, 103.1) cases of increased all-cause mortality, 19.1 (95% CI: 10.0, 28.2) increased cardiovascular disease deaths, and 9.4 (95% CI: 5.1, 13.5) increased respiratory disease deaths. Because wildfire smoke episodes are likely to continue impacting the Pacific Northwest in future years, continued preparedness and mitigations to reduce exposures to wildfire smoke are necessary to avoid this excess health burden.