Background: Exposure to heat stress is considered one of the most prevalent occupational hazards affecting performance. This study was conducted to investigate heat stress and its impact on the physiological and cognitive functions of operational field workers at a power plant.
Methods: This study was conducted on 150 male power plant personnel with 41.34±2.91 years (conducted in the summer of 2023). Physiological parameters were measured, and the assessment of heat stress (based on the Wet Bulb Globe Temperature (WBGT) index) and environmental monitoring were performed according to International Organization for Standardization (ISO) 7243 standards. Also, cognitive performance was investigated using the continuous performance test (CPT).
Results: Based on the results, individuals were exposed to heat stress conditions, and the mean WBGT index at the workstations was reported as 31.50±0.31 (above the standard limit). It was observed that all physiological indices in the exposed group increased significantly compared to the controls (P<0.05). The mean commission and omission errors showed a significant difference between the non-exposure and exposure groups. Also, the reaction time in the presence of occupational heat differed significantly from the mean reaction time in the absence of exposure (P<0.05). 
Conclusion: Based on the results and considering the importance of the power generation industry, the exposure of employees to heat stress and the subsequent physiological and cognitive performance disorders can have significant implications for health and safety outcomes. Therefore, attention to occupational exposures, the functional status of employees, and influencing factors are necessary as part of control and management strategies.