Air Quality Impacts of the January 2025 Los Angeles Wildfires: Insights from Public Data Sources

Smoke from the Los Angeles (LA) wildfires that started on January 7, 2025 caused severe air quality impacts across the region. Government agencies released guidance on assessing personal risk, pointing to publicly available data platforms that present information from monitoring networks and smoke plume outlines. Additional satellite-based products provide supporting information during dynamic wildfire smoke events. We evaluate the regional air quality impacts of the fires through publicly available fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) observations from regulatory monitoring stations, PurpleAir low-cost sensors, the TEMPO and TROPOMI satellite sensors, and Hazard Mapping System (HMS) Smoke Plumes during this multifire event. The most extreme air quality impacts were observed on January 8–9, particularly in the southern half of LA county, where daily average PM_2.5 concentrations at the downtown LA regulatory monitor reached 101.7 μg/m³ and 52.3 μg/m³ in Compton. On January 8th, 12 PurpleAir sensors located closer to burn areas exceeded daily PM_2.5 concentrations of 225 μg/m³. While smoke impacts were largely consistent across all data sources, differences in the spatiotemporal, including vertical, resolution of each product may affect interpretability for end users. This study underscores the importance of integrating multiple air quality data sources and improving accessibility to enhance public health messaging during wildfire events.