Dataset Information

Heat-related deaths in hot cities: estimates of human tolerance to high temperature thresholds.

ABSTRACT: In this study we characterized the relationship between temperature and mortality in central Arizona desert cities that have an extremely hot climate. Relationships between daily maximum apparent temperature (ATmax) and mortality for eight condition-specific causes and all-cause deaths were modeled for all residents and separately for males and females ages <65 and ? 65 during the months May-October for years 2000-2008. The most robust relationship was between ATmax on day of death and mortality from direct exposure to high environmental heat. For this condition-specific cause of death, the heat thresholds in all gender and age groups (ATmax = 90-97 °F; 32.2-36.1 °C) were below local median seasonal temperatures in the study period (ATmax = 99.5 °F; 37.5 °C). Heat threshold was defined as ATmax at which the mortality ratio begins an exponential upward trend. Thresholds were identified in younger and older females for cardiac disease/stroke mortality (ATmax = 106 and 108 °F; 41.1 and 42.2 °C) with a one-day lag. Thresholds were also identified for mortality from respiratory diseases in older people (ATmax = 109 °F; 42.8 °C) and for all-cause mortality in females (ATmax = 107 °F; 41.7 °C) and males <65 years (ATmax = 102 °F; 38.9 °C). Heat-related mortality in a region that has already made some adaptations to predictable periods of extremely high temperatures suggests that more extensive and targeted heat-adaptation plans for climate change are needed in cities worldwide.

SUBMITTER: Harlan SL

PROVIDER: S-EPMC3987036 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Heat-related deaths in hot cities: estimates of human tolerance to high temperature thresholds.

Harlan Sharon L SL Chowell Gerardo G Yang Shuo S Petitti Diana B DB Morales Butler Emmanuel J EJ Ruddell Benjamin L BL Ruddell Darren M DM

International journal of environmental research and public health 20140320 3

In this study we characterized the relationship between temperature and mortality in central Arizona desert cities that have an extremely hot climate. Relationships between daily maximum apparent temperature (ATmax) and mortality for eight condition-specific causes and all-cause deaths were modeled for all residents and separately for males and females ages <65 and ≥ 65 during the months May-October for years 2000-2008. The most robust relationship was between ATmax on day of death and mortality ...[more]

PMID: 24658410

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Project description:ContextMany organizations associated with sports medicine recommend using wet-bulb globe temperature (WBGT)-based activity-modification guidelines that are uniform across the country. However, no consideration has been given to whether the WBGT thresholds are appropriate for different weather conditions, such as warm-humid (WH) relative to hot-dry (HD), based on known differences in physiological responses to these environments.ObjectiveTo identify if personnel in regions with drier conditions and greater evaporative cooling potential should consider using WBGT-based activity-modification thresholds that differ from those in more humid weather.DesignObservational study.SettingWeather stations across the contiguous United States.Main outcome measure(s)A 15-year hourly WBGT dataset from 217 weather stations across the contiguous United States was used to identify particular combinations of globe temperature, wet-bulb temperature, and air temperature that produce WBGTs of 27.9°C, 30.1°C, and 32.3°C. A total of 71 302 observations were clustered into HD and WH environmental conditions. From these clusters, maximum heat-loss potential and heat-flux values were modeled at equivalent WBGT thresholds with various activity levels, clothing, and equipment configurations.ResultsWe identified strong geographic patterns, with HD conditions predominant in the western half and WH conditions predominant in the eastern half of the country. Heat loss was systematically greater in HD than in WH conditions, indicating an overall less stressful environment, even at equivalent WBGT values. At a WBGT of 32.3°C, this difference was 11 W·m-2 at an activity velocity of 0.3 m·s-1, which doubled for an activity velocity of 0.7 m·s-1. The HD and WH difference increased with the WBGT value, demonstrating that evaporative cooling differences between HD and WH conditions were even greater at a higher, rather than lower, WBGT.ConclusionsPotential heat loss was consistently greater in HD than in WH environments despite equal WBGTs. These findings support the need for further clinical studies to determine the appropriate WBGT thresholds based on environmental and physiological limits to maximize safety while avoiding unnecessary limitations.

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Heat-related deaths in hot cities: estimates of human tolerance to high temperature thresholds.

Publications

Heat-related deaths in hot cities: estimates of human tolerance to high temperature thresholds.

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