The influence of air humidity on human heat stress in a hot environment

Abstract

This article aims to present the physical adaptation capabilities of a human, seen as a response to extreme hot and dry or hot and humid conditions. Adaptation capabilities are expressed as safe exposure time in two variants: at rest and during physical activity. The study shows the results of calculations of the variability over time of the core temperature and skin temperature as well as heat balance. Calculations were made according to Standard No. EN ISO 7933:2005 on the basis of assumed and actual meteorological data. The results of the calculations show that in these conditions a hot but dry environment enables a human (although to a limited extent) to stay and perform low physical activity, provided access to drinking water is ensured. In contrast, a hot but humid environment causes more serious problems, due to the inability to reduce skin temperature by evaporation of sweat from the skin surface.

Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

“…In still air, PWC decreased linearly with increased relative humidity at each level of T a (Fig. 2), reflecting the increase in thermal strain typically associated with increased ambient humidity (Maughan et al, 2012;Sobolewski et al, 2021). Conversely, the best fit curve to the fan data were almost always curvilinear, caused by interaction of sweat rate, sweat evaporation capacity, sweat evaporation efficiency, and humidity.…”

Compounding Risks Caused by Heat Exposure and COVID-19 in New York City: A Review of Policies, Tools, and Pilot Survey Results

“…Another limitation of the maps is that they only use land surface temperature data compared to other heat indices that include humidity and air temperature. Humidity is potentially a major contributor to causing heat-related health issues ( Sobolewski et al . 2019 ).…”

Association with Temperature Variability and Physical Activity, Sedentary Behavior, and Sleep in a Free-Living Population

“…The general assumption is that low temperatures in winter would lead to less involvement in PA, but the results document that high temperatures could be more restrictive to PA than cold days. Sobolewski et al [ 29 ] demonstrated that a hot and humid environment made the humans stay and perform a low PA because they became more exhausted when they were exposed to high ambient temperature, The temperatures exceeding 30 °C with a high relative humidity imposed upon humans an extra burden of thermal stress that added to the physical stress [ 30 ]. The longitudinal study undertaken in Perth, Australia, with weather conditions relatively constant across all seasons, showed little impact on PA behavior.…”