Physiological Evaluation of the WBGT Index for Occupational Heat Stress

Ramanathan, N.; Belding, Harwood S.

doi:10.1080/0002889738506866

Cited by 37 publications

(25 citation statements)

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“…However, participants in the current study exercised wearing only shorts and undergarments, representing little, if any, thermal and evaporative resistance to heat transfer. Given that numerous reports indicate that the WBGT underestimates the level of heat strain under conditions in which evaporative heat loss and/or air movement are/is restricted, (2)(3)(4) such as with very high humidity levels, reduced airflow, or increased clothing insulation, it is conceivable that differences in the level of thermal strain under high humidity conditions may be exacerbated even when clothing ensembles are worn that do not require WBGT clothing correction factors.…”

Section: Discussionmentioning

confidence: 95%

“…ACGIH guidelines require that for increasing levels of WBGT and/or work rates, longer recovery times must be provided to the worker such that core temperature is maintained at or below 38 • C. (1) There is a general lack of consensus about whether thermal strain is equivalent during exposure to Warm/Humid or Hot/Dry environments with similar WBGT. For example, findings from several studies (2)(3)(4) have shown that WBGT underestimates the level of thermal strain under conditions in which evaporative heat loss and/or air movement is restricted. In contrast, other studies have reported similar levels of thermal strain, as determined by changes in rectal temperature (T re ), during exercise at 28 • C WBGT (5) or 32 • C WBGT, (6) and still others have reported a greater change in T re and body heat storage, determined by partitional calorimetry, during exercise in a Hot/Dry compared with a Hot/Wet environment of a WBGT of 32 • C. (7) One way to provide additional insight to help resolve these discrepancies would be the use of wholebody direct calorimetry to accurately measure changes in body heat content rather than relying on thermometric estimates of the change in body heat content from changes in T re and T sk .…”

Section: Introductionmentioning

confidence: 95%

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Cortisol and Interleukin-6 Responses During Intermittent Exercise in Two Different Hot Environments with Equivalent WBGT

Wright

McLellan²,

Stapleton

et al. 2012

Journal of Occupational and Environmental Hygiene

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Blood marker concentrations such as cortisol (COR) and interleukin (IL)-6 are commonly used to evaluate the physiological strain associated with work in the heat. It is unclear, however, if hot environments of an equivalent thermal stress, as defined by a similar wet bulb globe temperature (WBGT), result in similar response patterns. This study examined markers of neuroendocrine (COR) and immune (IL-6) responses, as well as the cardiovascular and thermal responses, relative to changes in body heat content measured by whole-body direct calorimetry during work in two different hot environments with equivalent WBGT. Eight males performed a 2-hr heavy intermittent exercise protocol (six 15-min bouts of cycling at a constant rate of metabolic heat production (360W) interspersed by 5-min rest periods) in Hot/Dry (46°C, 10% relative humidity [RH]) and Warm/Humid (33°C, 60% RH) conditions (WBGT ∼ 29°C). Whole-body evaporative and dry heat exchange, change in body heat content (ΔH(b)), rectal temperature (T(re)), and heart rate were measured continuously. Venous blood was obtained at rest (PRE) and the end of each exercise bout for the measurement of changes in plasma volume (PV), plasma protein (an estimate of plasma water changes), COR, and IL-6. Ratings of perceived exertion and thermal sensation were measured during the last minute of each exercise bout. No differences existed for ΔH(b), heart rate, T(re),%ΔPV, plasma protein concentration, perceptual strain (thermal sensation, perceived exertion), and COR between the Hot/Dry and Warm/Humid conditions. IL-6 exhibited an interaction effect (p = 0.041), such that greater increases were observed in the Hot/Dry (Δ = 1.61 pg·mL(-1)) compared with the Warm/Humid (Δ = 0.64 pg·mL(-1)) environment. These findings indicate that work performed in two different hot environments with equivalent WBGT resulted in similar levels of thermal, cardiovascular, and perceptual strain, which support the use of the WBGT stress index. However, the greater IL-6 response in the Hot/Dry requires further research to elucidate the effects of different hot environments and work intensities.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Cortisol and Interleukin-6 Responses During Intermittent Exercise in Two Different Hot Environments with Equivalent WBGT

Wright

McLellan²,

Stapleton

et al. 2012

Journal of Occupational and Environmental Hygiene

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“…(22,23) These standards have inherent limitations in their ability to predict maximum allowable exposure durations. (33,(35)(36)(37)(38) In some of Canada's deep mechanized mines, thermal stress is voluntarily assessed; however, this is often only intermittent. Moreover, the ACGIH TLV work allocations (in a cycle of work and recovery) is perceived by industry as conservative, resulting in unnecessary loss of productivity.…”

Section: Discussionmentioning

confidence: 99%

A Field Evaluation of the Physiological Demands of Miners in Canada's Deep Mechanized Mines

Kenny

Vierula

Mate

et al. 2012

Journal of Occupational and Environmental Hygiene

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This study was conducted to evaluate the physical/mechanical characteristics of typical selected mining tasks and the energy expenditure required for their performance. The study comprised two phases designed to monitor and record the typical activities that miners perform and to measure the metabolic energy expenditure and thermal responses during the performance of these activities under a non-heat stress environmental condition (ambient air temperature of 25.8°C and 61% relative humidity with a wet bulb globe temperature (WBGT) of 22.0°C). Six common mining jobs were evaluated in 36 miners: (1) production drilling (jumbo drill) (n = 3), (2) production ore transportation (load-haul dump vehicle) (n = 4), (3) manual bolting (n = 9), (4) manual shotcrete (wet/dry) (n = 3), (5) general services (n = 8) and, (6) conventional mining (long-hole drill) (n = 9). The time/motion analysis involved the on-site monitoring, video recording, and mechanical characterization of the different jobs. During the second trial, continuous measurement of oxygen consumption was performed with a portable metabolic system. Core (ingestible capsule) and skin temperatures (dermal patches) were recorded continuously using a wireless integrated physiological monitoring system. We found that general services and manual bolting demonstrated the highest mean energy expenditure (331 ± 98 and 290 ± 95 W, respectively) as well as the highest peak work rates (513 and 529 W, respectively). In contrast, the lowest mean rate of energy expenditure was measured in conventional mining (221 ± 44 W) and manual shotcrete (187 ± 77 W) with a corresponding peak rate of 295 and 276 W, respectively. The low rate of energy expenditure recorded for manual shotcrete was paralleled by the lowest work to rest ratio (1.8:1). While we found that production drilling had a moderate rate of energy expenditure (271 ± 11 W), it was associated with the highest work to rest ratio (6.7:1) Despite the large inter-variability in energy expenditure and work intervals among jobs, only small differences in average core temperature (average ranged between 37.20 ± 0.22 to 37.42 ± 0.18°C) were measured. We found a high level of variability in the duration and intensity of tasks performed within each mining job. This was paralleled by a large variation in the work to rest allocation and mean energy expenditure over the course of the work shift.

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“…c The presented values are for 8 hours exposure, so, exposure time must be considered. ferentiate between strenuous warm humid conditions and hot dry environments that did not result in excessive physiological strain (14,21).…”

Section: Discussionmentioning

confidence: 99%

Consistency Assessment of Heat Stress Monitoring of Outdoor Workers Using Sweat Rate Measurement and Wet Bulb Globe Temperature WBGT in Arid and Semi-Arid Climates

Heidari¹,

Golbabaei²,

Shamsipour³

et al. 2018

Health Scope

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Background: Heat stress as a major problem that strikes a lot of people, especially outdoor workers, throughout the world. Many parts of Iran have arid and semi-arid climates, in which high air temperature and radiant temperature, along with usually low humidity, cause hazardous conditions for outdoor workers in hot months. Therefore, in order to take every preventive measure to protect exposed workers against heat related disorders, it is indispensable to select an appropriate index that accurately relates environmental parameters to physiological responses. Objectives: This investigation aimed at investigating two heat stress and strain indices of wet bulb globe temperature-WBGT-and sweat rate, respectively, in order to examine their consistencies in arid and semi-arid climates of Iran. Methods: A total of 272 outdoor workers from different jobs were randomly selected and their sweat rate was calculated via a defined protocol three times a day. Simultaneously, environmental parameters, as well as WBGT index, were recorded for each working station. This study was performed during spring and summer. Results: The obtained results based on Kappa value showed a weak agreement between two standard indices. In addition, evaluation of outdoor workers using WBGT compared to sweat rate was accompanied by an overestimation. Moreover, based on mean and standard amounts of sweat rate, there were no cases exceeding the presented reference value regarding sweat rate at any time of the study. Conclusions: It seems that sweat rate standard level at a shift work may need some modifications related to the real condition of work in arid and semi-arid climates of Iran. In addition, judgment based on monitoring sweat rate alone, as a physiological response to heat in these climates, can be probably accompanied by underestimation

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Physiological Evaluation of the WBGT Index for Occupational Heat Stress

Cited by 37 publications

References 0 publications

Cortisol and Interleukin-6 Responses During Intermittent Exercise in Two Different Hot Environments with Equivalent WBGT

Cortisol and Interleukin-6 Responses During Intermittent Exercise in Two Different Hot Environments with Equivalent WBGT

A Field Evaluation of the Physiological Demands of Miners in Canada's Deep Mechanized Mines

Consistency Assessment of Heat Stress Monitoring of Outdoor Workers Using Sweat Rate Measurement and Wet Bulb Globe Temperature WBGT in Arid and Semi-Arid Climates

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