PROJECT SUMMARY (RESEARCH PROJECT 1: THE ROLE OF VULNERABILITY AND ADAPTATION ON THE EFFECTS OF CO-OCCURRING HEAT, AIR POLLUTION, AND WILDFIRE ON HEART FAILURE HOSPITALIZATIONS) To protect human health in the changing climate, research is urgently needed to understand adaptation and mitigation efforts impact on public health while protecting the most vulnerable and ensuring health equity. The climate-related hazards of high heat and high fine particulate matter air pollution (PM2.5), related to wildfire (WF- PM2.5), are increasingly occurring at the same time in California and other regions adversely affecting human health. Heart failure (HF) as a proposed sentinel climate change and health outcome exposes vulnerable individuals to heat and PM2.5 health effects due to heightened susceptibility. The research objective is to elucidate the joint effect of high heat, PM2.5, and WF-PM2.5 on HF hospitalizations and readmissions then evaluate how these effects may differ by vulnerability factors and adaptation strategies to inform solution-oriented policies and interventions. An electronic medical record (EMR) enriched with patient neighborhood characterization and state administrative hospitalization data are used to estimate the effect of co-exposure to heat and (WF-)PM2.5 on HF hospitalizations (Aim 1). Longitudinal EMR data will allow 30-day readmissions examination as a secondary outcome. Individual (e.g., age, race/ethnicity, socioeconomic status) and neighborhood characteristics (e.g., sociodemographics, social vulnerability index, climate vulnerability index) and power outages are assessed to understand if they modify heat- and PM2.5-effects (Aim 2). Possible adaptation strategies aimed at either the community (cooling centers/public spaces, community pools, greenspace) or individual level (air conditioning) are examined to observe how adaptive policies might change heat- and PM2.5-effects (Aim 3). These results will inform future action-oriented policies, programs, and targeted interventions to mitigate climate change health effects, especially among the most vulnerable. Research Project 1 will contribute to the University of Southern California’s (USC) CLIMAte-Related Exposures, Adaptation, and Health Equity (CLIMA) Center’s capacity building efforts to engage a scientifically diverse research team in conducting and developing approaches for impactful transdisciplinary climate health research.