SUMMARY - RESEARCH PROJECT 2: Landscape fire PM2.5, air conditioning, and mortality among dialysis patients Patients with end-stage renal disease (ESRD) would benefit from more knowledge about health risks posed by climate change. One risk that is not fully explored for these patients is the long-term impact of exposure to fine particulate matter (PM2.5) from landscape fire smoke. Large wildfires, an important portion of landscape fires, have increased in frequency and size and models project that the risk of these fires will increase in coming years due to climate change. Though research has shown that short-term exposure to landscape fire PM2.5 (e.g., 1-30 days) increases risk of all-cause mortality among patients receiving dialysis, we do not yet know if long-term exposure to landscape fire PM2.5 increases mortality among ESRD dialysis patients. In addition, residential factors that may mitigate climate change-related risks have not been fully explored for ESRD patients. One of these residential factors is residential air conditioning (AC), which may provide multiple benefits, including potentially reducing exposure to both heat and PM2.5 (from all outdoor sources). Recent research has shown unequal intra-urban distribution of residential AC prevalence across metropolitan areas in the US. We will examine whether residential AC prevalence may influence mortality among dialysis patients. In coordination with the Community Engagement Core (CEC), we will work with a patient advisory board from the American Association of Kidney Patients (AAKP) to discuss planned and future research, disseminate results, and plan for continued engagement. The US Renal Data System (USRDS) maintains a nationwide registry of patients who require dialysis. We will use the USRDS data of approximately 1.5 million patients who initiated dialysis between 2006-2018 and follow them until 2019, creating a retrospective cohort to examine whether landscape fire PM2.5 or AC prevalence influence mortality in dialysis patients. For Aim 1, our exposure is number of days exposed to elevated landscape fire PM2.5, defined as days when landscape fire PM2.5 exceeded the current National Ambient Air Quality Standards 24-hr standard for PM2.5 of 35 µg/m3. We will use publicly available estimates of 24-hr mean landscape fire PM2.5 (and control for non-fire PM2.5), which uses spatially interpolated PM2.5 observations, available on a 15 x 15 km grid, for the full contiguous US each day. We will interpolate the data to the ZIP code level, as residential ZIP codes are available for dialysis patients. We will use a semiparametric multi-level mixed-effect Cox hazards regression for mortality and estimate the hazard ratios of our exposure (landscape fire PM2.5 or prevalence of AC), adjusting for both individual- and community-level covariates. For Aim 2, AC prevalence was previously estimated for 115 metropolitan areas. We will restrict our analyses to examine these 115 metropolitan areas and employ a similar model and confounders. This research will provide information critical to help guide preventive strategies for dialysis patients, a population vulnerable to health effects of climate change. Through the CEC and AAKP engagement, we will design present and future research, disseminate findings, and engage end-users.