Abstract
Objectives: Different indices are used to evaluate heat stress in outdoor environments. This study was aimed at examining the applicability of the Relative Strain Index (RSI) to the assessment of heat stress in several climates of Iran. Methods: Based on the Köppen classification, three different climates were studied. Arak, Bandar Abbas, and Sari were selected as representative of semi-arid and cold climates, hot and dry, and Mediterranean, respectively. The data recorded by the meteorological organization, including air temperature, relative humidity and air velocity were surveyed during 15-year period in three different climates. The RSI index was calculated by the formula. Also, the Wet Bulb Globe Temperature (WBGT) index was computed using a model presented by the Australian Bureau of Meteorology (ABM). Data were analyzed using SPSS v.22, descriptive statistics, Pearson correlation coefficient, and linear regression. Results: The mean RSI index in summer of the 15 years in Arak was 0.033 ± 0.33, in Bandar Abbas 0.54 ± 0.6 and for Sari was 0.17 ± 0.05. A high correlation was found between environmental variables and RSI index in three different climates. As well, there was a positive and significant correlation between both RSI and WBGT indices in three different climates (R2>0.96). Conclusion: The RSI index is a simple and empirical index and can be used for the evaluation of heat stress along with other indices. The index estimates the situation more than expected to be stressful in warm and dry conditions. So, it is not a useful index for hot and dry climates such as Bandar Abbas.
Highlights
Heat stress and its effects in outdoor environments have become one of the biggest health challenges
In the Arak city during the last 15 years, the maximum air temperature was observed in July (28.12 ± 0.65), the maximum relative humidity in June (24.7 ± 1.55), the maximum amount of Relative Strain Index (RSI) and Wet Bulb Globe Temperature (WBGT) indices was related to July, 0.151 ± 0.013 and 23.26 ± 0.4, respectively
In the Bandar Abbas city, the maximum air temperature was in July (34.27 ± 0.26), the maximum relative humidity was observed in August (68.38 ± 2.4), and the maximum amount of RSI and WBGT indices was obtained in July (0.6 ± 0.03) and (37.22 ± 0.43), respectively
Summary
Heat stress and its effects in outdoor environments have become one of the biggest health challenges. If due to high ambient temperatures people cannot balance between the generated and received heat by the body and lost heat, the heat generated is greater than the lost heat, due to which heat stress can occur (Asghari et al, 2017b, Nassiri et al, 2018b, Nassiri et al, 2017, Nassiri et al, 2018a). Climate change and global warming, produced by greenhouse gases, have caused heat wave especially in the warm seasons, to put many people at risk of hyperthermia and other heatrelated complications.
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