Effects of different humidity levels on the human body in a high-temperature environment at high altitude

Abstract: Workers in high-temperature, high-humidity, and low-oxygen environments face multiple environmental stressors, leading to increased blood circulation, changes in metabolic heat production, elevated heart rates, and reduced nerve sensitivity. These factors may contribute to a significant heat stress on the body, which directly reduces physical work capacity and impacts overall performance.As society advances, greater emphasis is placed on the safety of human factors, particularly in the most challenging work environments involving high temperatures and humidity at high altitudes. This issue has garnered significant attention. Previous studies mainly focused on one specific aspect, such as the impact of high-temperature environments on the human body. To address the need for comprehensive research on human factors in complex working conditions, this study aims to investigate thermophysiological indicators of the human body under high-temperature, high-humidity, and low-oxygen conditions. The findings will serve as a reference for improving human safety and ergonomic standards in challenging environments.METHODS: To enhance current protective measures and reference standards for specialized work and mitigate risks to human health, this study examined the effects of varying humidity levels on body surface temperature and humidity under 40℃ conditions at simulated 3000 meters above sea level. Eight participants (four males and four females) sat in a high-temperature chamber at high altitude with humidity levels of 30% and 60% for 40 minutes. During this period, body surface temperatures and humidity of seven different body segments, including forehead, chest, back, upper arm, hand, thigh and calf, were recorded using button-temperature sensors, while participants completed subjective scales.The temperature and humidity of body surface at each measured segment were linearly fitted to time to determine the correlation between these variables and time. Paired T-tests were conducted on the temperature and humidity of body surface at each 5-minute interval compared to the initial values to assess the stability. Independent T-tests were performed to compare the temperature and humidity between male and female groups at each time interval for different ambient humidity levels to identify gender-based differences. Additionally, independent T-tests were used to evaluate the effect of ambient humidity on the temperature and humidity of each body segment for both genders.RESULTS & CONCLUSIONS: Statistical analysis indicated that temperature and humidity levels varied across different body segments over time under two ambient humidity conditions. Body surface humidity showed significant differences based on body segment but was less influenced by temperature changes. Additionally, gender differences were observed. Females exhibited higher and more variable body surface temperatures compared to males in both ambient humidity conditions, while trends in body surface humidity over time differed between genders. Overall, the small-sample study in this research suggests that the design of protective clothing should incorporate breathable and moisture-absorbing fabrics tailored to specific body areas, while should also consider gender-specific requirements. Besides, the weak correlation between subjective thermal comfort ratings and body surface temperature and humidity indicates that the current indicators are insufficient to fully represent human thermal comfort in such environments, and more comprehensive or combined indicators are needed.

Keywords: High temperature and high humidity, Thermal comfort, Ergonomics

DOI: 10.54941/ahfe1006462

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