Thermal responses of workers during summer: An outdoor investigation of construction sites in South China

Abstract

Extreme thermal environments harm the health and reduce the productivity of outdoor workers. Variations in human physiological indices and the thermal exposure time limit are the main factors in evaluating heat safety in an extreme thermal environment. Therefore, it is necessary to determine the relationships between human physiological indices, psychological responses, and thermal parameters to accurately predict and evaluate human thermal safety in extreme thermal environments. A field survey, including thermal parameter measurements, was conducted at construction sites in South China during the summer of 2019. The relationship between health risk and thermal parameters was obtained, and the adaptability and sensitivity of workers to i) thermal parameters (outdoor ambient temperature (Ta), mean radiant temperature (Tmrt), wind speed (Va), and relative humidity (RH)) and ii) physiological indicators (heart rate (HR) and auditory canal temperature (ACT)), as well as the variations in their cognitive ability, were analyzed. The results indicate that 40 % of workers experienced discomfort and that when Ta > 34 °C, the working intensity of workers needs to be reduced in construction sites. The HR and ACT increased with increasing working hours, and the thermal parameters and cognitive ability decreased. To avoid discomfort, it is suggested that the HR may be kept near 94 beats/min. The effects of physiological indicators and cognitive ability on the physical and mental state of the workers were significant; with an increase in thermal environment parameters, the efficiency decreased by approximately 8%. The results of this investigation are beneficial for ensuring the occupational safety of workers and reducing the risk of heat exposure.