Investigating the Relationship between Heat Stress and Strain Indices with Human Productivity in Workers of a Steam Power Plant

Excessive work heat stress has profound effects on physiological responses that cause occupational injuries, losses, and reduced productivity. The aim of this study was to investigate the relationship between heat stress and strain indices with human productivity in workers of a steam power plant.

This cross-sectional study was performed on 104 workers of a steam power plant in summer season. To measure heat stress and strain, two indices wet bulb globe temperature (WBGT) and Heat strain score index (HSSI) were used to measure stress and heat strain, respectively. Human productivity was also measured using a Hersey and Goldsmit 26-item scale. Data were analyzed using ANOVA test and Pearson correlation coefficient.

The highest value of WBGT index was related to the 4th floor boiler unit with average (27.3 ± 5.6) and the lowest value was related to the administrative unit with average (16.9 ± 3.5). The maximum and minimum value of HSSI index was obtained for the 3th floor boiler (27.2 ± 0.4) and Workshop installation unit. The highest and lowest values human productivity is related to the welding (97 ± 25.9) and boiler unit (28.5 ± 2.8). The results of ANOVA analysis showed that the values of WBGT, HSSI indices and productivity subscales in different units were significantly different (P < 0.05). Pearson correlation coefficient analysis showed that there is a significant inverse relationship between productivity and its subscales with the amount of heat stress and strain (P < 0.05).

According to the results of this study, there is a negative relationship between productivity, heat stress and strain. Therefore, to protect workers' health and productivity, precautionary measures should be taken, including an appropriate rest-work ratio, short working hours, fluid replacement, and engineering controls such as the use of efficient cooling methods such as air conditioning, fan, or cooling clothing.