Abstract
For time- and cost-efficient heat stress assessment procedures at workplaces or in experimental studies, short-time measurement periods (e.g. 1 h) are sometimes employed in lieu of whole shift observations assuming that the short time period will provide valid figures of equilibrium physiological responses. We studied the influence of exposure duration on physiological heat strain considering the modifying effects of clothing and heat acclimation using a database of 564 climatic chamber exposures performed by 28 young males under heat stress conditions with widely varying air temperature and humidity levels. We compared heart rates, rectal and mean skin temperatures, and sweat rates recorded after 1 h with the values averaged over the third hour of exposure representing steady-state. One-hour measurements agreed with equilibrium values for rather low strain levels only, with heart rates below 100 bpm and rectal temperatures below 37.2 °C. On average, one-hour values underestimated all heat strain parameters. This underestimation error was only moderately influenced by clothing and heat acclimation status, but increased significantly with air temperature and humidity, reaching considerable magnitude under hot-humid conditions associated with elevated heat strain. Regression analyses of the prediction error depending on the equilibrium response revealed that underestimation increased with equilibrium strain level. This correlation was strongest for heart rate and core temperature, and was shown to potentially cause a misclassification of hazardous working conditions as safe by given heat strain criteria.Practical Relevance: The severe underestimation of heat strain due to short measurement periods, as observed under hot-humid conditions and/or when associated with high physiological strain, will immediately impact the exposed personnel, but will also inform occupational health professionals and standard writers regarding the heat stress assessment for work shifts with high activity levels or with protective clothing.
Highlights
1.1 Background and literature reviewClimate change will pose escalating risks associated with heat stress to both the general and working population (Casanueva et al 2020; ILO 2019; Morris et al 2021; Watts et al 2021)
The aim of this study was to compare shorttime measurements (1 h) of physiological strain experienced over a wide range of heat stress conditions to long-term responses observed during the 3rd hour (3 h) of climatic chamber exposures considering the potentially modifying influence of clothing and heat acclimation
The ANCOVA results revealed that t for all physiological variables were significantly related to Ta and pa (Table 2, with borderline significance of pa for tTsk) and were on average negative for all clothing and acclimation conditHR 0
Summary
1.1 Background and literature reviewClimate change will pose escalating risks associated with heat stress to both the general and working population (Casanueva et al 2020; ILO 2019; Morris et al 2021; Watts et al 2021). A major strain criterion applied in heat related health risk assessment procedures is equilibrium core temperature, usually measured in the rectum (Malchaire et al 2000), which should not exceed a specified threshold value, e.g. 38 °C as applied by ISO 7933 (2004). The level of this equilibrium core temperature will only depend on workload within the so-called ‘prescriptive zone’ (Fig. 1), a term coined by Lind (1963). As performing a corresponding hazard assessment will require time-consuming and cost-intensive observations at workplaces
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
