CHART: RESEARCH PROJECT – SUMMARY High ambient temperature is a well-recognized environmental hazard to human health. The overarching goal of this project is to examine factors related to physiologic susceptibility and factors along exposure pathways that may lead to disparities in heat-related illnesses. The project also aims to map features within multiple social determinants of health (SODH) domains that can alter an individual’s ability to mitigate heat exposure to help identify actionable intervention strategies. Aim 1 will quantify disparities in associations between heat and emergency department (ED) visits in Atlanta, GA during the period 2013 to 2021. ED visit is an important and understudied heat-related morbidity outcome. We will compile a database of geocoded electronic medical records from the Grady Memorial Hospital and four hospitals within Emory Healthcare. We will assess patient- level effect modifiers (e.g., age, sex, homelessness, insurance status, co-morbid conditions, and home medication), and modifiers that are related to the residential built environment (e.g., building type, building year and green space). Aim 2 will conduct a matched case-control study of 400 participants from Grady and Emory hospitals to examine risk factors for heat-related ED visits that are not captured through medical records, such as how and why exposure occurred. We will develop a survey tool and structured interview to assess demographic, physiological/health status, neighborhood and individual SDOH, and knowledge, attitudes, and practices around factors hypothesized to impact susceptibility and exposure to heat. Qualitative analysis will be used to contextualize and understand the exposure pathways and challenges experienced among the cases leading to their presentation at the ED. To address knowledge gaps in the understanding of heat exposures, Aim 3 will characterize temperature exposure for 120 individuals living in under-resourced communities by conducting 48-hour continuous monitoring of personal, indoor and outdoor exposure to temperature, humidity and air quality. We will characterize absolute differences between personal, indoor, and outdoor temperatures, as well as identify demographic, behavioral, socioeconomic, time-activity-location, and built environment factors contributing to these differences in exposures. We will disseminate findings and monitoring results back to participants. In all Aims, we will engage with community partners to determine additional salient risk factors, develop surveys and interviews, and identify participants for recruitment. Overall, the project will provide timely knowledge on the adverse health effects of heat in an urban setting with a focus on under-resourced communities. The proposed research project is highly aligned with the Center’s theme of assessing how climate change threatens the health of urban communities. Moreover, the project’s findings, data, and infrastructure will provide opportunities for capacity building and translation in climate and health research.