Heat stress as a physical harmful agent can increase the risk of health and safety problems in different workplaces such as mining. Although there are diff

The present study aimed to optimize the electrospinning parameters for polyacrylonitrile (PAN) nanofibers containing MgO nanoparticle to obtain the appropriate fiber diameter and mat porosity to be applied in air filtration. Optimization of applied voltage, solution concentration, and spinning distance was performed using response surface methodology. In total, 15 trials were done according to the prepared study design. Fiber diameter and porosity were measured using scanning electron microscopic (SEM) image analysis. For air filtration testing, the nanofiber mat was produced based on the suggested optimum conditions for electrospinning. According to the results, the lower solution concentration favored the thinner fiber. The larger diameter gave a higher porosity. At a given spinning distance, there was a negative correlation between fiber diameter and applied voltage. Moreover, there were curvilinear relationships between porosity and both spinning distance and applied voltage at any concentration. It was also concluded that the developed filter medium could be comparable to the high-efficiency particulate air (HEPA) filter in terms of collection efficiency and pressure drop. The empirical models presented in this study can provide an orientation to the subsequent experiments to form uniform and continuous nanofibers for future application in air purification. Implications: High-efficiency filtration is becoming more important, due to decreasing trends air quality. Effective filter media are increasingly needed in industries applying clean-air technologies, and the necessity for developing the high-performance air filters has been more and more felt. Nanofibrous filter media that are mostly fabricated via electrospinning technique have attracted considerable attention in the last decade. The present study aimed to develop the electrospun PAN-containing MgO nanoparticle (using the special functionalities such as absorption and adsorption characteristics, antibacterial functionality, and as a pore-forming agent) filter medium through experimental investigations for application in high-performance air filters.

Introduction. This article aimed to investigate the effect of heat stress on cognitive performance and the blood concentration of stress hormones among workers of a foundry plant. Methods. Seventy workers within the exposed (35 people) and unexposed (35 people) groups were studied. The wet bulb globe temperature (WBGT) index was measured for heat stress assessment. The cognitive performance tests were conducted using the Stroop color word test (SCWT) before and during working hours. For the assessment of the serum level of cortisol and the plasma level of adrenaline and noradrenaline, blood samples were taken during working hours from both groups. Results. Only for SCWT III was there a significant relationship between heat stress and test duration, error rate and reaction time. The laboratory test results revealed significantly higher concentrations of cortisol, adrenaline and noradrenaline in the exposed subjects than in the unexposed group. There existed a positive correlation between cortisol, adrenaline, noradrenaline and WBGT index and also test duration and reaction time of SCWT III, and number of errors of SCWT I, SCWT II and SCWT III during work. Conclusion. Heat stress can lead to an increase in the blood level of stress hormones, resulting in cognitive performance impairment.

The present study aimed to investigate the applicability of Universal Thermal Climate Index (UTCI) as an innovative and science-based index in public health researches, in occupational heat stress assessment. All indoor and outdoor workers (200 people) of Brick industries of Shahroud, Iran participated in the research. First, the environmental variables such as air temperature, wet-bulb temperature, globe temperature, air velocity and relative humidity were measured; then UTCI and WBGT (wet-bulb globe temperature) indices were calculated. Simultaneously, physiological parameters including systolic and diastolic blood pressure, oral temperature, skin temperature, tympanic temperature and heart rate of workers were measured. UTCI and WBGT indices were 34.2 ± 2°C, 21.8 ± 1.8°C in the outdoor environments and 38.1 ± 4.4°C, 24.7 ± 3.3°C at the indoor environments, respectively. There were the weak inverse relationships between UTCI and WBGT indices at the outdoor environments and physiological responses such as systolic blood pressure, and diastolic blood pressure. However, there were no similar results for indoor environments. The significant relationships were found between UTCI and WBGT at both indoor and outdoor environments. Both UTCI and WBGT indices are suitable for assessing the occupational heat stress. Although, UTCI index seems more appropriate for heat stress assessment in the environments with low humidity and air velocity.