Environment/Climate Change
Spatial patterns of wildfire-related PM2.5 increases and historical redlining during the January 2025 Los Angeles Wildfires Malaika Jade Mason* Malaika Jade Mason University of Chicago
High fine particulate matter (PM2.5) exposure is associated with adverse cardiovascular and pulmonary health outcomes. Wildfire smoke can substantially increase PM2.5 levels in surrounding areas. Although historically redlined neighborhoods experience higher baseline air pollution, less is known about whether this pattern also exists regarding wildfire-related PM2.5 increases. We examined spatial and temporal patterns of PM2.5 across the City of Los Angeles during the January 2025 wildfires, including the spatial overlap between PM2.5 increases and historically redlined areas. Daily PM2.5 data from 11 U.S. Environmental Protection Agency monitors and 86 World Air Quality Index sensors were aggregated into weekly means and spatially interpolated using ordinary kriging to generate PM2.5 surfaces for pre-wildfire, peak wildfire, and post-wildfire periods. Mean PM2.5 concentrations were summarized by Los Angeles Community Planning Areas (CPAs), and changes in PM2.5 were calculated between baseline and peak wildfire weeks. Historical redlining data from the Home Owners’ Loan Corporation were intersected with CPAs. HOLC grades range from A (“Best”) to D (“Hazardous”), with grades C and D historically assigned to neighborhoods disproportionately inhabited by communities of color and subjected to housing disinvestment. Spatial heterogeneity in PM2.5 was observed during the peak wildfire period, with the largest increases occurring in inland and eastern CPAs. The greatest increases were observed in Boyle Heights (+27.1 µg/m3) and Northeast Los Angeles (+26.4 µg/m3), while western CPAs experienced smaller changes. CPAs predominantly classified as HOLC grade C or D tended to exhibit large wildfire-related increases in PM2.5 compared to those graded A or B. Wildfire-related PM2.5 increases during the January 2025 Los Angeles wildfires were unevenly distributed across the city, with larger increases occurring in historically redlined areas.
