(R21) Physicochemical and toxicological assessment of the particulate matter (PM) from the Los Angeles Wildland-Urban Interface (WUI) Fires and its impact on respiratory health

About This Grant

EXECUTIVE SUMMARY/ABSTRACT The increasing frequency and intensity of wildfires are having serious public health consequences. Wildfire exposures have adverse health impacts, but the specific mechanistic effects remain unknown, especially for wildland-urban-interface (WUI) fires. Due to the burning of human-made structures as well as biomass in WUI fire episodes, the particulate matter with aerodynamic sizes less than 2.5 microns (PM2.5) generated from WUI fires, (WFPM2.5), maybe more toxic than urban background PM2.5, which is mostly generated from fossil fuel combustion, or pure biomass WFPM2.5. Such wildfire exposures will have devastating health consequences, especially in those with existing disease such as asthma and COPD. In January 2025, catastrophic WUI fires impacted Los Angeles(LA), resulting in a severe air pollution event with high PM concentrations. During this event, in collaboration with UCLA, we deployed state- of-the-art instruments in two locations to collect air quality data and size-fractionated WFPM for physicochemical characterization and toxicological assessment. The WFPM samples are stored at 4°C, and their physicochemical and toxicological properties must be analyzed in a timely manner to avoid degradation. The proposed interdisciplinary project consists of two Aims and focuses on the impact of WFPM on respiratory health. In Aim 1 we will perform detailed physicochemical analysis of the collected PM0.1 and PM0.1- 2.5 size fractions, including: i) X-Ray Fluorescence (XRF) for 28 trace elements; ii) Thermal Optical Carbon (TOC) analysis of organic carbon (OC) and elemental carbon (EC) fractions; iii) GC-MS analysis of 105 polyaromatic hydrocarbons (PAHs); and iv) ICP-MS analysis of metal content;. In Aim 2 we will employ 1). a translational ex vivo human precision-cut human lung slice (hPCLS) model and an in vitro primary cultured HASM cell model to assess the effects of WFPM on airway function, including effects on bronchoconstriction/dilation, excitation-contraction (E-C) coupling pathways, and secreted inflammatory mediators; and 2). An in vitro THP-1 macrophage model to evaluate the effects of WFPM on the health and innate immune function of alveolar macrophages, including multiple toxicity endpoints as well as phagocytosis and killing of Acinetobacter baumannii, a prevalent cause of secondary bacterial pneumonia The proposed time-sensitive work will provide a detailed physicochemical characterization of WUI WFPM in LA in comparison to non-WUI WFPM and traffic-related PM, as well as its relative toxicity and effects on respiratory health and will support the main hypothesis that WFPM from WUI fires is more toxic compared to background PM. Findings and WFPM samples from this study are timely needed by public health risk assessors and will also support future epidemiological and mechanistic studies on WUI fires and help develop remediation strategies to protect the health of impacted communities.