Evaluation of environmental heat stress on physiological parameters

Background: Thermal component of the atmospheric environment is an important issue which is related to human's health. Thermal environment includes both heat exchange conditions (stress) and the physiological response (strain). The aim of this study was to measure the association of heat indices (PSI, HSI, Humidex) especially subjective one (STI) with some physiological parameters (Blood pressure, pulse rate and skin temperature). Methods: This is a cross-sectional study conducted on 387 male farmers on Boukan, West Azerbaijan, Iran in 2016. Sampling was conducted on the hottest days in summer on July based on the meteorological report. Heat parameters was measured 3 times in each session. Results: Direct associations were found between heat indices and physiological parameters except systolic BP. However, invers associations were found between blood pressure, skin and core body temperature, pulse rate with all heat indices. Based on the results of linear regression analysis, significant association was found between WBGT and skin temperature (B = 0.31, CI: 0.02, 0.61, P = 0.03). Results also showed significant association between Humidex and skin temperature (B = 0.21, CI: -0.03, 0.40, P = 0.02). However, no significant associations were found between other heat stress indices including UTCI, PHS, HIS, STI and Humidex with all study physiological parameters (core body temperature, systolic and diastolic blood pressure and also pulse rate). Conclusion: As expected, farmer's health is affected by physiological parameters. Moreover, among assessed types of heat stress indices WBGT and Humidex were more powerful to show better the association with mentioned physiological parameters.