Estimating Reduced Heat-Attributable Mortality for an Urban Revegetation Project

This paper presents estimates of reductions in heat-attributable excess mortality in Philadelphia, Pennsylvania (USA) that could result under different levels of implementation for urban afforestation, urban green space, and green roof projects. These excess mortality reductions are quantified by integrating results from literature evaluating the possible thermal benefits of various urban heat island (UHI) mitigation measures with results from heat-mortality studies in Philadelphia. These estimates are developed for future periods using regionally downscaled climate change data that reflects one possible future climate in Philadelphia. The estimated time series of mortality reductions is then monetized using a premature mortality value from the health economics and regulatory impact analysis literature. Our results suggest that across the range of implementation currently under consideration, future excessive heat event (EHE) mortality could be reduced by roughly 135 to 315 deaths over the period 2020 through 2049. The equivalent monetized value for this health benefit would be between $0.74 billion and $1.69 billion dollars ($2006). These results highlight the importance of accounting for potential health benefits of UHI mitigation in benefit-cost assessments, especially as reductions in heat attributable mortality represents only a portion of the anticipated health benefits from the program (health benefits from air quality improvements would also be anticipated). These results also highlight the need to look for opportunities where multiple policy objectives can be achieved with a single action. In this case, the afforestation and urban vegetation options were initially identified as a possible approach for achieving compliance with mandates associated with reducing combined sewer overflows. As detailed here, these actions also provide substantial benefits for reducing excess mortality associated with EHEs through mitigation of UHI effects.

Suggested citation or credit:

Mills, David, Kalkstein, Laurence. 2009.  Estimating Reduced Heat-Attributable Mortality for an Urban Revegetation Project. Presented at 2nd International Conference on Countermeasures to Urban Heat Islands. September 19-23, 2009.

Publication Date: September 2009

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