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Background & objectives: Heat stress at workplaces can cause several problems including decreased thermal comfort and increased heat strain; moreover, it can effect negatively on worker performance and productivity. The present study aims to investigate the effect of heat stress on performance loss among outdoor workers in a hot and dry climate.
Methods: An analytic study was conducted during four months from June to September 2013, in one of the provinces of Iran (Qom). Environmental parameters including dry temperature, surface temperature of soil , solar radiation, relative humidity and air velocity were measured in weather stations every ten minutes between 7 am and 7 pm (in total, 8598 measurements). Potential labor performance losses based on WBGT (Wet Bulb Globe Temperature) heat stress index provided by Australian Bureau of Meteorology were determined using a graph presented by Kjellstrom. SPSS 16 was applied for all statistical analysis.
Results: The total average of WBGT was 27±2.57 °C. The maximum WBGT (28.59°C) was obtained between 3 and 4 pm. The average performance loss in jobs with power of 200, 300, 400 and 500 watts was 1.6%±0.43, 9.6±1.94, 19.65±2.68, 65.53±2.68 and 29.1±2.5 respectively. A statistically significant relationship was found between WBGT values and percentage of performance loss.
Conclusion: Outdoor workers in warm seasons with hot-dry climate experience the loss of performance, which can effect adversely on labor health and economy growth of country.