Claire Schollaert , Rachel Connolly, Lara Cushing, Michael Jerrett, Tianjia Liu, Miriam Marlier

Smoke from the Los Angeles 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 regulatory and low-cost monitoring networks. Additional satellite-based products provide useful supplementary information during dynamic wildfire smoke events. We evaluate the regional air quality impacts of the fires through publicly available fine particulate matter (PM2.5) and nitrogen dioxide (NO2) observations. Specifically, we analyze pollutant data from regulatory monitoring stations, PurpleAir sensors, the TEMPO and TROPOMI satellite sensors, and HMS Smoke Plumes during the January 2025 Los Angeles wildfires. The most extreme air quality impacts were observed on January 8 and 9, particularly in the southern half of Los Angeles County. While smoke impacts were largely consistent across all evaluated data sources, differences in the spatial and temporal 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.