Correlation investigation between Wet Bulb globe temperature (WBGT) and thermal work limit (TWL) comparing modified threshold limit of tympanic temperature

Thermal stress risk management requires the development of applied indicators. The purpose of this study was to evaluate the performance of the two indicators including WBGT and TWL and their fit with the tympanic temperature.
This cross-sectional study was carried out on 101 urban service personnel in a heat and dry area in 2016. The measurements of the study indices including WBGT, TWL, air velocity and tympanic temperature were performed using a WBGT Digital Thermometer, TWL software, thermal anemometer and Thermometer measuring the temperature of the tympanic curtain, respectively. Data were analyzed by SPSS software version 22.
The results of this study showed that the highest correlation was observed between WBGT index and tympanic temperature (r=0.669) and the lowest correlation coefficient was between TWL index and tympanic temperature (r=0.343). In addition, the absolute magnitude of the correlation coefficient between the WBGT and TWL indicators was higher in comparison with other indicators (r=0.660) and the correlation with the increase in air temperature was also higher, so that at temperatures above 35 ° C, the correlation coefficient of the two indices reached 0.996.
The findings of this study indicated that the TWL index can be considered and applied as a suitable substitute for the WBGT index.