Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates

Abstract Exertional heat illness poses a significant risk for workers, athletes, and military personnel participating in outdoor activities during hot weather. An important component of heat safety is to monitor environmental conditions through heat stress indices like the wet bulb globe temperature...

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Main Authors: A. J. Grundstein, S. W. Yeargin, E. R. Cooper, L. Cargile, J. Clark, R. M. Lopez, K. C. Miller, A. M. Montalvo, S. Scarneo‐Miller, R. L. Stearns
Format: Article
Language:English
Published: American Geophysical Union (AGU) 2025-03-01
Series:GeoHealth
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Online Access:https://doi.org/10.1029/2025GH001347
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author A. J. Grundstein
S. W. Yeargin
E. R. Cooper
L. Cargile
J. Clark
R. M. Lopez
K. C. Miller
A. M. Montalvo
S. Scarneo‐Miller
R. L. Stearns
author_facet A. J. Grundstein
S. W. Yeargin
E. R. Cooper
L. Cargile
J. Clark
R. M. Lopez
K. C. Miller
A. M. Montalvo
S. Scarneo‐Miller
R. L. Stearns
author_sort A. J. Grundstein
collection DOAJ
description Abstract Exertional heat illness poses a significant risk for workers, athletes, and military personnel participating in outdoor activities during hot weather. An important component of heat safety is to monitor environmental conditions through heat stress indices like the wet bulb globe temperature (WBGT) and adjust activity as conditions get progressively hotter. Traditionally, on‐site (OS) WBGT measurement devices are used, but phone applications (PAs) offering WBGT estimates have emerged as a potential alternative. However, there is little information on how closely PA‐derived WBGTs match OS measurements to guide decision‐making. This study compared the PA‐derived Zelus WBGT estimates with OS measurements from Kestrel 5400 devices and their impact on activity modification categorization. A 2‐month observational study collected 1,056 paired (OS and PA) WBGT measurements from 26 high schools across 11 states in the United States and over diverse surfaces (artificial turf 53%, natural grass 44%, others 3%). WBGT values were categorized using regional activity modification thresholds to account for local acclimatization. Our findings indicated that while exhibiting high correlation (r = 0.89), PA WBGTs were on average about 1°C cooler, with differences of 2–3°C at higher WBGTs. Findings were similar for both grass and artificial turf surfaces. Further, significant discrepancies were observed in WBGT‐based activity modification categories, with the PA more frequently indicating lower modification categories compared to OS devices, especially in hotter conditions. In light of these findings, the PA requires further validation prior to its adoption as a replacement for OS measurements.
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spelling doaj-art-4abb892df9544185b4d35166b2c4a7e12025-08-20T01:49:46ZengAmerican Geophysical Union (AGU)GeoHealth2471-14032025-03-0193n/an/a10.1029/2025GH001347Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application EstimatesA. J. Grundstein0S. W. Yeargin1E. R. Cooper2L. Cargile3J. Clark4R. M. Lopez5K. C. Miller6A. M. Montalvo7S. Scarneo‐Miller8R. L. Stearns9University of Georgia Athens GA USAUniversity of South Carolina Columbia SC USAUniversity of Georgia Athens GA USAUniversity of Georgia Athens GA USADuke University Durham NC USAUniversity of South Florida Tampa FL USATexas State University San Marcos TX USAArizona State University Phoenix AZ USAWest Virginia University Morgantown WV USAKorey Stringer Institute University of Connecticut Storrs CT USAAbstract Exertional heat illness poses a significant risk for workers, athletes, and military personnel participating in outdoor activities during hot weather. An important component of heat safety is to monitor environmental conditions through heat stress indices like the wet bulb globe temperature (WBGT) and adjust activity as conditions get progressively hotter. Traditionally, on‐site (OS) WBGT measurement devices are used, but phone applications (PAs) offering WBGT estimates have emerged as a potential alternative. However, there is little information on how closely PA‐derived WBGTs match OS measurements to guide decision‐making. This study compared the PA‐derived Zelus WBGT estimates with OS measurements from Kestrel 5400 devices and their impact on activity modification categorization. A 2‐month observational study collected 1,056 paired (OS and PA) WBGT measurements from 26 high schools across 11 states in the United States and over diverse surfaces (artificial turf 53%, natural grass 44%, others 3%). WBGT values were categorized using regional activity modification thresholds to account for local acclimatization. Our findings indicated that while exhibiting high correlation (r = 0.89), PA WBGTs were on average about 1°C cooler, with differences of 2–3°C at higher WBGTs. Findings were similar for both grass and artificial turf surfaces. Further, significant discrepancies were observed in WBGT‐based activity modification categories, with the PA more frequently indicating lower modification categories compared to OS devices, especially in hotter conditions. In light of these findings, the PA requires further validation prior to its adoption as a replacement for OS measurements.https://doi.org/10.1029/2025GH001347exertional heat illnesswet bulb globe temperatureWBGTphone applicationon‐site measurementactivity modification
spellingShingle A. J. Grundstein
S. W. Yeargin
E. R. Cooper
L. Cargile
J. Clark
R. M. Lopez
K. C. Miller
A. M. Montalvo
S. Scarneo‐Miller
R. L. Stearns
Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
GeoHealth
exertional heat illness
wet bulb globe temperature
WBGT
phone application
on‐site measurement
activity modification
title Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
title_full Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
title_fullStr Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
title_full_unstemmed Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
title_short Evaluating Heat Risk: Comparing On‐Site WBGT Measurements Versus Smartphone Application Estimates
title_sort evaluating heat risk comparing on site wbgt measurements versus smartphone application estimates
topic exertional heat illness
wet bulb globe temperature
WBGT
phone application
on‐site measurement
activity modification
url https://doi.org/10.1029/2025GH001347
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