The Relative Importance Of Work Intensity And Environmental Heat Exposure In The Development Of Hyperthermia In Construction Workers In The Summer

Construction workers are at disproportionately high risk of heat illness. This is likely due to excessive heat stress, which is dictated by both environmental heat exposure and increased metabolic heat production, the latter being a function of work intensity. Together, these factors determine the risk of developing hyperthermia, defined as a rise in core temperature, with hyperthermia underlying the risk of heat illness. However, the comparative importance of environmental heat exposure versus work intensity on the development of hyperthermia in construction workers is unknown. PURPOSE: To determine the relative importance of environmental heat exposure and work intensity on core temperature in construction workers in the summer. METHODS: Over 5 full workdays in summer 2024, data were collected in 162 workers (39 ± 11 y, 6 women) employed at a large commercial construction worksite in the Midwest U.S. Enrolled workers were from 12 different job types. Wet bulb globe temperature (WBGT), measured over the workday at eight locations (Kestrel 5400), provided an index of environmental heat exposure with exposures customized for each worker depending on their location on the worksite. Intense work duration was calculated as the percentage of the workday in which workers engaged in heavy or very heavy work relative to rest, light, or moderate work, which was estimated from pulse rate and accelerometry (Garmin Instinct 2). Core temperature was estimated from continuous measurement of heart rate (Polar H10) using the algorithm developed by the U.S. Army Research Institute of Environmental Medicine (ECTemp). Data were collected using the SafeGuard App (VigiLife Inc). RESULTS: Workers engaged in intense work 14 ± 15% (range: 0-72%) of the workday. Peak and average WBGT was 28 ± 4 °C (range: 22-36 °C) and 25 ± 2 °C (range: 21-29 °C). Peak and average ECTemp was 37.8 ± 0.3 °C (range: 37.1-38.8 °C) and 37.5 ± 0.2 °C (range: 36.8-38.0 °C). Both intense work duration (r = 0.616, p < 0.001) and peak WBGT (r = 0.206, p = 0.010) were positively correlated with peak ECTemp, but intense work duration explained comparatively more variance in ECTemp (p < 0.001). CONCLUSION: Compared to peak WBGT, intense work duration is a stronger predictor of peak ECTemp in construction workers during the summer. Support: R01OH011528 & Turner Construction Foundation Supported by: R01OH011528 & Turner Construction Foundation