Heat stress can lead to an increase in the blood level of stress hormones, resulting in cognitive performance impairment.

Urban air pollution caused by fine particles, the increasing development of nanotechnology and the spread of contagious diseases, as well as bioterrorism, has raised concerns about aerosols and bioaerosols. This research aims to study the effect of various parameters on the diameter and uniformity of electrospun polyurethane/chitosan nanofibers and to evaluate their filtration performance and antimicrobial activity against nanoaerosols and Escherichia coli (E. coli) bacteria as a model bioorganism, respectively. Using response surface methodology, the main and interactive effects of four parameters including polyurethane/chitosan weight ratio, applied voltage, needle tip-to-collector distance and polymer flow rate were investigated on the mean diameter and uniformity of electrospun nanofibers. The nanoparticle filtration efficiency of the polyurethane/ chitosan electrospun nanofiber filter was determined after preparation under recommended optimum conditions using a standard filtration test rig. There was an increase in the mean diameter of nanofibers and decrease in the uniformity of them with increase in polyurethane polymer solution concentration. The mean diameter of nanofibers decreased significantly with increasing applied voltage and chitosan content in polyurethane/chitosan blended polymer solution. A significant, positive correlation was seen between needle tip-to-collector distance, polymer flow rate and the mean diameter of nanofibers. The prepared nanofiber filters showed an acceptable range of quality factor and pressure drop for using in filtration applications such as industrial filtration processes and personal respiratory protection equipment. The results of the performing bacterial disk diffusion method indicated that electrospun polyurethane/chitosan nanofibers have good antibacterial activity against E. coli bacteria as a model microorganism.

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.

The low-frequency noise generated by wind turbines is known as one of the risk factors for health. The aim of this study was to study the noise effect of wind turbine on the general health of staff at Manjil wind farm. For this purpose, workers were divided into three groups: maintenance, security, and office staff. Equivalent sound levels were measured for each group. Individual's health data were assessed using the 28-item General Health Questionnaire. Pearson correlation, analysis of variance, and multiple regression tests were used for data analysis in the R software. Statistical analysis results showed that the noise exposure is significantly correlated to all sub-scales of general health, except for depression. The low-frequency noise from wind turbines can cause harmful effects on the health of workers that are too close to the wind turbine and receive very intense noise.

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.PAPER HISTORY