Human response regulation in hot and humid environments with salt spray

High temperature, humidity, and salt spray are common in coastal areas, posing health risks to maritime workers. Understanding and quantifying their impacts on the human body are essential. Therefore, a study was conducted with 72 participants in an artificial climate chamber under 18 different environmental conditions, combining three levels of air temperature (T_a: 34, 36, and 38 °C), two relative humidity levels (RH: 70 and 90 %), and three airborne salt spray concentrations (S_c: 0, 8, and 23 mg/m³). The oral temperature, tympanic temperature, heart rate, and blood samples of the participants were analyzed. The significance analysis results showed that T_a and RH had significant effects on oral and tympanic temperatures and heart rate, but the presence of salt spray masked these effects. Effect decomposition analysis further quantified the individual and interactive contributions of T_a, RH, and S_c to these physiological parameters. The findings confirm the presence of combined effects among the three environmental parameters. The combined effects values of T_a and RH were consistently above zero, whereas the same S_c had opposing effects under different conditions. At 34 °C-70 %, S_c = 23 mg/m³ increased oral temperature, tympanic temperature, and heart rate by 0.8 °C, 0.6 °C, and 32 bpm, respectively, whereas at 38 °C-90 %, it decreased them by 0.6 °C, 0.3 °C, and 13 bpm. Blood analysis also indicated that S_c induced changes in blood indicators. This study reveals environmental impacts on the human body and provides insight into heat stroke prevention.