Human health and heat stress: an analysis of neighborhoods in metropolitan Phoenix, AZ

Two foremost challenges facing the rapidly urbanizing and naturally hot Phoenix, AZ metropolitan area are the urban heat island (UHI) effect and water scarcity. The transformation of native landscapes into built environments coupled with anthropogenic heat (e.g., vehicles, air conditioners, and industry) has produced the UHI effect (higher nighttime temperatures in cities compared to nearby native areas). Recent research, however, documents significant temperature variability within the urban environment which is highly correlated with landuse. For instance, irrigated landscapes, such as turf grasses and trees, mitigate against warm temperatures through evapotransportation in some areas of Phoenix, while impervious surfaces and soils of drought-resistant landscaping store heat, exacerbating high temperatures in other metropolitan areas. So while some residents utilize valuable water supply to support vegetated yards, other residents have drought-resistant landscaping which uses less water but is correlated with higher levels of exposure to heat stress. This study examines 16 diverse census blocks groups within the city of Phoenix, AZ and utilizes four datasets to investigate the complex relationship between landuse, human health and vulnerability to heat stress, and water consumption. Surface air temperature is estimated using the Weather Research and Forecast (WRF) climate model at a spatial resolution of 1km for a 2005 summer heat wave; vegetation fraction is calculated using the remote sensing Object-Based Image Analysis (OBIA) classification technique based on 2005 National Agriculture Imagery Project (NAIP); monthly water consumption data provided by the City of Phoenix is aggregated to the census block group for 2005; and data from the Phoenix Area Social Survey (PASS) 2006 reflect heat-related illnesses among 808 local respondents. Results indicate that exposure to extreme heat varies significantly throughout the Phoenix metropolitan area; water consumption and vegetation fraction are highly correlated with exposure to environmental conditions; and heat-related illnesses are related to social characteristics.