Where There’s Fire, There’s Smoke: Examining Population Exposure to PM2.5 from Prescribed Burning in Northeastern Washington

Abstract

Prescribed burning is receiving wider scientific and political recognition as a tool for reducing wildfire risk and mitigating the impacts of future wildfires. Indeed, Washington DNR's 2017 Forest Health Strategic Plan set a goal of conducting mechanical treatments and prescribed burning on 1.25 million acres of Washington's forests over the next 20 years. However, the risk of smoke from prescribed burning impacting local communities is not well understood. Therefore, prescribed burning is highly regulated, limiting the achievement of this goal. This thesis examines the impacts to air quality as a result of smoke from a set of broadcast burns in North-central and Northeastern Washington in 2019. We compare spatial and temporal data from prescribed burning permits with 24-hour average PM2.5 concentrations recorded by a network of permanent air quality monitors and low-cost sensors. Our analysis found the network of air quality monitors and sensors is inadequately distributed in relation to prescribed burning activity to fully measure population exposure to PM2.5 using sensors and monitors alone. However, where prescribed burns did occur near air quality monitors and sensors, three out of 22 prescribed burns had nearby monitors or sensors register PM2.5 concentrations above 35.5 μg/m3, the maximum set by the National Ambient Air Quality Standards. 1,411 people were within 16 kilometers of all three burns.