Air-Quality Impacts and Intake Fraction of PM2.5 during the 2013 Rim Megafire

Abstract

The 2013 Rim Fire was the third largest wildfire in California history and burned 257 314 acres in the Sierra Nevada Mountains. We evaluated air-quality impacts of PM_2.5 from smoke from the Rim Fire on receptor areas in California and Nevada. We employed two approaches to examine the air-quality impacts: (1) an evaluation of PM_2.5 concentration data collected by temporary and permanent air-monitoring sites and (2) an estimation of intake fraction (iF) of PM_2.5 from smoke. The Rim Fire impacted locations in the central Sierra nearest to the fire and extended to the northern Sierra Nevada Mountains of California and Nevada monitoring sites. Daily 24-h average PM_2.5 concentrations measured at 22 air monitors had an average concentration of 20 μg/m³ and ranged from 0 to 450 μg/m³. The iF for PM_2.5 from smoke during the active fire period was 7.4 per million, which is slightly higher than representative iF values for PM_2.5 in rural areas and much lower than for urban areas. This study is a unique application of intake fraction to examine emissions-to-exposure for wildfires and emphasizes that air-quality impacts are not only localized to communities near large fires but can extend long distances and affect larger urban areas.