Climate‑Related Performance of the Wet‑Bulb Globe Temperature (Wbgt) Index: A Fuzzy Analytical Hierarchy Process Approach Publisher

Summary: Could climate-aware heat metrics protect workers? Reweighting WBGT raised estimates by 0.4–0.8°C and improved heart-rate agreement, possibly shifting work-rest advice. #HeatStress #WorkerSafety

Mousavi S M ; Dehghan H ; Yazdanirad S
Source: Theoretical and Applied Climatology Published:2026

Abstract

The Wet Bulb Globe Temperature (WBGT) index is widely used for occupational heat stress assessment, particularly under ISO 7243. However, its classical formulation relies on fixed empirical weighting of environmental parameters, which may introduce systematic bias for use in heterogeneous climatic conditions. Given that previous studies report climate-related variability in WBGT performance, a climate-related theoretical evaluation is required. This study assessed the climate-related performance of WBGT using a Fuzzy Analytical Hierarchy Process (FAHP) framework. Environmental measurements were collected from March to September 2025 in three cities in Iran, including Abadan (hot-humid environment), Isfahan (hot-dry environment), and Gorgan (temperate-humid environment). Baseline WBGT values were calculated based on the standard of ISO 7243. Weights for air temperature, relative humidity, wind speed, and solar radiation were derived through FAHP modeling using triangular fuzzy numbers to address uncertainty in expert judgments. Sensitivity analysis was conducted using ± 10% perturbations of each parameter. Physiological validation was performed using data on heart rate and thermal sensation related to 150 outdoor workers. Air temperature and relative humidity in Abadan, air temperature in Isfahan, and relative humidity in Gorgan had the greatest influence on the estimation of the WBGT index. Use of climate-specific weights increased WBGT values by 0.4–0.8 °C. This change may affect work-rest recommendations when exposure levels are close to the ISO 7243 threshold limits. The weighted WBGT improved physiological agreement, with an increase of heart rate correlations from 0.55 to 0.62 to 0.66–0.71 and a decrease of root mean square error (RMSE) by 10–18%. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2026.