Challenges associated with projecting urbanization-induced heat-related mortality

• Published in: The Science of the total environment 2014-08, Vol.490, p.538-544
• Main Authors: Hondula, David M., Georgescu, Matei, Balling, Robert C.
• Format: Article
• Language: English
• Subjects: Arizona; Biological and medical sciences; Climate Change; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Environment. Living conditions; Environmental Exposure - statistics & numerical data; Exact sciences and technology; External geophysics; Extreme heat; Health; Heat-related mortality; Hot Temperature; Humans; Medical sciences; Meteorology; Models, Theoretical; Mortality - trends; Public health. Hygiene; Public health. Hygiene-occupational medicine; Risk Assessment; Urbanization; Urbanization - trends
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.04.130

Maricopa County, Arizona, anchor to the fastest growing megapolitan area in the United States, is located in a hot desert climate where extreme temperatures are associated with elevated risk of mortality. Continued urbanization in the region will impact atmospheric temperatures and, as a result, potentially affect human health. We aimed to quantify the number of excess deaths attributable to heat in Maricopa County based on three future urbanization and adaptation scenarios and multiple exposure variables. Two scenarios (low and high growth projections) represent the maximum possible uncertainty range associated with urbanization in central Arizona, and a third represents the adaptation of high-albedo cool roof technology. Using a Poisson regression model, we related temperature to mortality using data spanning 1983–2007. Regional climate model simulations based on 2050-projected urbanization scenarios for Maricopa County generated distributions of temperature change, and from these predicted changes future excess heat-related mortality was estimated. Subject to urbanization scenario and exposure variable utilized, projections of heat-related mortality ranged from a decrease of 46 deaths per year (−95%) to an increase of 339 deaths per year (+359%). Projections based on minimum temperature showed the greatest increase for all expansion and adaptation scenarios and were substantially higher than those for daily mean temperature. Projections based on maximum temperature were largely associated with declining mortality. Low-growth and adaptation scenarios led to the smallest increase in predicted heat-related mortality based on mean temperature projections. Use of only one exposure variable to project future heat-related deaths may therefore be misrepresentative in terms of direction of change and magnitude of effects. Because urbanization-induced impacts can vary across the diurnal cycle, projections of heat-related health outcomes that do not consider place-based, time-varying urban heat island effects are neglecting essential elements for policy relevant decision-making. •Extreme heat is a public health hazard in metropolitan Maricopa County, Arizona.•Urbanization is a key driver of future regional temperature changes.•Projections of heat–health impacts for 2050 vary across urbanization scenarios.•The sign and magnitude of projections are also sensitive to exposure variable choice.•Consideration of urbanization effects is critical for heat–health policymak