The Health Department's Role in New York City's Mitigation Plans for Future Extreme Heat Events

New York City (NYC), like many other large cities, is projected to experience more severe and frequent heat waves in the coming decades. Its high density of population, traffic, and large buildings results in a strong urban heat island effect and drives distinct intra-city variation in air pollution. NYC is also highly racially segregated, and the historical disinvestment in neighborhoods with people of color has contributed to poor housing conditions and other environmental issues that contribute to disparity in both exposures and health burdens across neighborhoods. Because of its large population size—currently 8.6 million—the adverse health impacts (e.g., heat-stroke and excess natural cause deaths) of extreme heat events in the city in the past decades were substantial enough to detect. The New York City Department of Health (the Health Department, or we, hereafter) has been involved in epidemiological analyses to understand adverse health impacts of extreme weather events, air pollution, and power outages for more than a decade. The Health Department also established in 2008 the New York Community Air Survey (NYCCAS), a high-density air quality monitoring network to analyze and report trends in neighborhood-level air pollution. In collaboration with the Mayor’s Office and other city agencies, these operations are integrated into the City’s planning and development of sustainability and resiliency policies, including mitigation plans for future extreme heat events and a health impact assessment of the city’s plan to reduce greenhouse gas emissions in the coming decades. We have used several epidemiological approaches to investigate the risk of heat including a time-series analysis of the relationship between temperature indices and excess deaths, identifying a multiday, non-linear function of heat that resulted in the local National Weather Service lowering the threshold for heat advisories in 2008. We also have developed heat-related illness syndrome and its near-real time prediction model to assist the City’s heat emergency response operations during extreme heat events. In collaboration with academic researchers, we investigated individual- and neighborhood-level risk factors for excess deaths during and days after extreme heat events, identifying four key variables: percentage of non-Latinx Black, percentage of public assistance, the lack of vegetative cover, and the average surface temperature, which led to development of a Heat Vulnerability Index (HVI). The Mayor’s Office of Resiliency developed “Cool Neighborhoods NYC”, an adaptation and mitigation strategy targeted to high HVI neighborhoods that includes street tree planting, increasing the area of high albedo surfaces, and expanding green infrastructure. To help the City evaluate the impact of street tree planting, we used temperature data collected at 150 NYCCAS network locations to develop land-use regression models using built and natural environment datasets. The model results indicated that building density and vegetation metrics drove neighborhood-to-neighborhood variation in temperature. Based on these results, the Health Department designed and launched with the Mayor’s Office and Parks Department a campaign in 2018 to capture hyper-local baseline temperature measurements in 14 high HVI neighborhoods, using over 400 temperature sensors installed on street trees and light poles. With two summers’ data, we will characterize the relationship between various vegetation indices, built environment, and spatial variation in temperatures within and across these neighborhoods. These data are expected to help NYC improve mitigation plans to reduce urban heat island effects and future impacts of extreme heat events. In addition to these environmental measurements data, we also continue to conduct analyses of health outcome data to quantify morbidity and mortality burden, which can support policies to reduce inequities in the adverse impacts of weather and air pollution. For example, reviews of heat-stroke deaths from the Office of Chief Medical Examiner found that most occur indoors in homes without air conditioning. These findings coupled with analyses of excess deaths and healthcare visits due to heat have focused policy efforts on increasing air conditioning access in low-income neighborhoods. In this presentation, we share some of the results that support NYC’s mitigation plans for future extreme heat events and other environmental issues, describe how we collaborate with other City agencies and academic partners, and discuss the challenges we face in prioritizing short-term and long-term research goals in the rapidly changing environment. While some of the environmental and social issues we face may be unique to NYC, the dynamics of interagency and external collaborations may provide lessons learned for other cities facing current and preparing for future environmental and health impacts of climate change.