Ambient Air Quality Impacts During and After the 2025 Los Angeles Wildfires
PROVAT SAHA, Christopher Lim, Yumeng Cui, Steven Boddeker, Joseph Salazar, Zihan Zhu, Julia Montoya-Aguilera, Mohammad Sowlat, Payam Pakbin, Andrea Polidori, Jason Low, South Coast Air Quality Management District
Abstract Number: 471
Working Group: Burning Questions of Aerosol Emissions, Chemistry, and Impacts from Wildland-Urban Interface (WUI) Fires
Abstract
The January 2025 Eaton and Palisades fires in Los Angeles County were some of the most devastating urban-wildland interface wildfires in California’s history. There is significant concern from both the public and the research community regarding the air quality impacts of this event—particularly because many older homes were burned, raising concerns about emissions of various air toxics, including arsenic, lead, and asbestos. Air monitoring data from South Coast Air Quality Management District (South Coast AQMD) air monitoring stations and low-cost sensor (LCS) network across the South Coast Air Basin provided a valuable resource for assessing ambient air quality impacts during the fire, as well as the spatial and temporal extent of these impacts. Analysis of data from several stations revealed substantial increases in PM₁₀, PM₂.₅, and several air toxic metals—including lead and arsenic—specifically at locations impacted by the smoke plume. However, within a few days once the smoke generation was over, pollutant concentrations returned to typical background levels. There are also potential air quality impacts during the cleanup and repopulation phases, due to resuspension of dust and ash that may contain air toxic metals and/or asbestos. To assess these impacts, South Coast AQMD conducted mobile monitoring surveys using a multi-metal mobile platform in both burn areas. These surveys enabled rapid, area-wide assessments of air toxics metals concentrations and helped identify potential exposure risks for cleanup workers. Following the mobile surveys, South Coast AQMD established five fixed monitoring sites in the two burn areas to conduct continuous monitoring of PM₁₀ and PM₂.₅, as well as time-integrated sampling for analysis of air toxics metals and asbestos. This presentation will discuss the observed air pollution enhancements during the fires, as well as South Coast AQMD’s post-fire mobile and stationary air quality monitoring efforts in the affected areas.