Effect of Heat Stress on Productivity Loss of Outdoor Workers: A Case Study in a Hot and Dry Climate

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.
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.
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.
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.