Evaluation of Smoke Exposure Risk from January 2025 Los Angeles Wildfires Using Crowdsourced Data

Area of Science:

• Environmental Health
• Air Pollution Science
• Public Health

Background:

• Wildfire smoke is a growing air pollution concern in the western US, impacting health and personal exposure assessments.
• Elevated PM2.5 levels were observed in Los Angeles County following the January 2025 Palisades and Eaton Fires.

Purpose of the Study:

• To evaluate indoor and outdoor PM2.5 levels during wildfire smoke events using crowdsourced sensor data.
• To analyze disparities in smoke exposure across communities based on vulnerability, building type, and home value.

Main Methods:

• Utilized a high-resolution network of crowdsourced PurpleAir sensors to monitor PM2.5.
• Matched indoor and outdoor sensors to assess exposure.
• Analyzed data in relation to CalEnviroScreen (CES) vulnerability scores, ventilation types, and home values.

Main Results:

• Outdoor PM2.5 significantly increased during smoke events, with highest concentrations in the most vulnerable communities.
• Indoor PM2.5 also rose, but indoor/outdoor ratios decreased, suggesting partial indoor protection and behavioral changes.
• Infiltrated PM2.5 varied across CES groups, with building attributes showing limited predictive power.

Conclusions:

• Wildfire smoke exposure is influenced by a combination of behavioral actions and neighborhood characteristics.
• Targeted interventions are needed to enhance indoor air quality in vulnerable communities during smoke events.