مجله بهداشت و ایمنی کار
سال یازدهم شماره 4 (زمستان 1400)

In recent years tend to use of natural fibers has increased in making sound absorbers. Fiber-based natural materials have low density, low production costs, and are biodegradable.

In this study, the effect of nanoclay and the behavior of the nanocomposite specimens containing tea waste, polypropylene, and nanoclay in the sound absorption coefficient are investigated. 

The results showed the sound absorption coefficient increases by increasing the tea waste weight percent of the polypropylene. 60% increase in tea waste has a special role in the absorption of sound waves at a frequency of 1000 Hz and 2500 to 6300 Hz frequency range as the TW60 N5 sample has the sound absorption coefficient 0.94 and 0.84 in 1000 and 6300 Hz frequencies, respectively. Comparison of the sound absorption coefficient of composite and nanocomposite showed that sound absorptions increase by adding nanoclay to the 5%, at frequencies above 2000 Hz.

Tea waste-based sound absorbers can be used in noise control due to the high acoustic absorption and no harmful effects on human health.

Toluene is considered as a group of chemical contaminants, causing problems for people’s health. Due to the high rate of evaporation and rapid emission in the surrounding environment, it leads to the exposure of many employees and people at risk and, subsequently, its irreparable effects on their health in different jobs. Therefore, its removal is very important. In the present study, this contaminant was removed using the copper metal-organic framework (MOF) under different operating conditions. 

In this study, the copper MOF was synthesized using the one-pot and in situ method. Physical and morphological properties of the adsorbent were investigated using BET, XRD, FTIR and SEM techniques. The efficiency of the adsorbent in removing toluene from the air stream under the dynamic adsorption system was investigated by examining the effect of the variables of adsorbent mass, pollutant concentration and humidity. Isotherm, thermodynamics and kinetics equations were used to evaluate the data.

The results of experiments determining the properties of the metal-organic framework showed the formation of pure Cu-BDC crystals with mean and particle size distribution of 1.95 nm. The specific surface area calculated by the BET method for the mentioned sample was 686 m2 g-1 and the total volume of structural pores was 0.335 g3 cm3. The presence of micropores increased the dynamic adsorption capacity of toluene. The findings follow the Langmuir isotherm model and the Pseudo-second order kinetic model. Based on the results of thermodynamic studies, entropy change (ΔS°) and enthalpy change (ΔH°) were equal to -0.44 kJ mol-1 K-1 and -15.67 kJ mol-1, respectively. Gibbs free energy change (ΔG°) was also calculated negatively, indicating that the adsorption process was spontaneous and exothermic. The regeneration of the adsorbent was 77% after three cycles.

According to the results of this study, the microporous copper MOF can be used as a result of cheapness, high access, high adsorption capacity and appropriate regeneration rate in different operating conditions for adsorption of toluene.

Chemical industries often have risks for the environment and communities, due to the use of complex facilities and processes. Also, in the ammonia tanks, the probability of risk of explosion is high, owing to their specific characteristics. The aim of this study is to evaluate the risks of explosion scenario at the ammonia tank in the Kermanshah petrochemical complex

To achieve the purpose of this study, the Fuzzy Fault Tree Analysis (FTA) method was used to estimate the probability of reliability in the basic events. In this study, after drawing Fault Tree for identifying basic events, the probability of basic events was estimated by means of expert’s elicitation, and the probability of minimal cut sets was computed through Boolean logic gates.

According to the results, the probability of occurrence of the top event was obtained equal to 0/054997. In the minimal cut set prioritizing, the failing of pressure safety valves identified as the most effective factor in the top event occurrence, and afterward failing the control valves and human errors were identified.

This study indicates that, based on expert elicitation, a fuzzy error tree method can be used to assess the risk of various scenarios in the industry. Overall, in assessing the risk of the explosion scenario in the ammonia reservoir, it was found that some minor defects, and even human error, could be considered as a major contributor to the explosion.

Low back pain is one of the most common musculoskeletal disorders leading to disability around the world. Several studies have suggested that prolonged computer/ laptop work contributes to the development of low back pain and discomfort. The results of the studies conducted on the association of back discomfort and muscle activity are contradictory. Thus, the present study aims to evaluate the relationship between the activity level and relative rest time of the trunk muscles with back discomfort while working with a laptop in a sitting position.

First, 20 young healthy males performed laptop work including mouse work and typing in conventional and ergonomic setups. In the ergonomic setup, the screen height and keyboard placement were specifically adjusted for each individual. In addition, the electromyographic activity of the lumbar erector spinae, right and left multifidus and transversus abdominis, rectus abdominis, external oblique muscles, and the posture of the lumbar spine were recorded in the first and last two minutes of an 8-min task. After the end of each task, the participants scored their back discomfort.

The results showed a positive correlation (r=0.57 and p=0.009) between back discomfort and the EMG amplitude of the lumbar erector spinae muscle. In addition, back discomfort was negatively correlated to the relative rest time of the multifidus muscle (r=0.50 and p=0.023), and a positive correlation was reported with the relative rest time of the transversus and rectus abdominis (r=0.47, p=0.039, and r=0.45, p=0.049, respectively).

The relative rest time of the trunk muscles may be a better index than that of the EMG amplitude to highlight the risk factors for back discomfort. However, a causative link between muscle activity and discomfort cannot be implied from this study. The current results do not undermine the role of other factors associated with the increased level of discomfort during sitting.

Heat stress is a critical problem in hot industries, especially in incredibly hot climates. It can greatly impair the work process and put the health of workers at risk. This study aims to investigate the applicability of the WBGT index in determining the allowable working time in very hot weather conditions in one of the steel industries in Ahvaz.

This study was conducted in different sectors of a steel industry in Ahwaz. The physiological parameters of sixty workers working in different parts of the industry were evaluated. Environmental variables and the Wet-Bulb globe temperature (WBGT) Index were also simultaneously measured during work shifts. The acceptable work time was calculated based on the reserve heart rate (RHR) and the WBGT index.

The heat stress index among all occupational groups, based on the WBGT index, was incredibly high and surpassed the recommended level (P<0.05). The statistical test results also indicated a significant difference between the two indices in predicting the adequate work time at different work stations (P <0.05).

The current study results revealed that using the WBGT index for assessing and managing the risk of heat exposure in a hot climate may not have sufficient reliability and performance. Consequently, it is recommended to use optimal indices based on environmental and physiological assessments in a hot climate in order to monitor and control the heat stress associated with heat exposure.

There are several generic and specific models to assess the individual job performance (IJP). While these methods may provide the valuable information, none of them cover the complexity and wide range of the behaviors which express the IJP. This review study aimed to identify all existing models and incorporate them to achieve a comprehensive conceptual model to assess the IJP. 

Databases such as PubMed, Scopus, Embase, and ProQuest were systematically searched to meet the study’s goals. Moreover, references to relevant publications were examined. Finally, suitable publications were discovered and analyzed using the inclusion and exclusion criteria. 

The results of Search in databases, including PubMed, Scopus, Embase, and ProQuest, showed that 12754 articles were found in the initial search. After removing duplicate and unrelated articles, finally, 155 eligible articles were selected. Based on full-text screening, 10 studies were excluded, and 5 studies were not accessible. Finally, by checking the references mentioned in the selected articles, 4 more eligible articles which were not retrieved in the search strategy were added; finally, 61 articles were selected to be reviewed. Ninteen articles were related to the general models, and 19 articles addressed job-specific assessment models. The remaining 23 articles described other existing models. 

To evaluate IJP, a heuristic structure was developed based on the literature research. These dimensions were selected because they can accommodate all of the preceding models’ dimensions. They also include any behaviors that may have an impact on IJP.

Recognizing the personality traits of employees and examining the role of these traits in motivating people’s safety can greatly lead to the formation of safe behavior of employees. Considering the significant importance of reducing adverse events and developing safe behaviors, the present study aimed to investigate the role of nurses’ personality traits in their safety behaviors with the mediating role of safety motivation during 2019-2020. 

This is a descriptive-analytical study conducted among nurses working in educational hospitals affiliated by Qazvin University of Medical Sciences, from which 435 individuals were selected by multi-stage proportional sampling method. Data were collected using McCray and Costa Five-Factor Personality Questionnaire, Saleh Motivation Questionnaire (2010) and Safe Behavior Questionnaire (2016) and analyzed by SPSS software version 26 and AMOS software version 23.

The path coefficients between nurses’ personality traits and their safety motivation (0.557) and safety motivation with safe behavior of individuals (0.267) were statistically significant (p<0.05). Furthermore the path coefficient between nurses’ personality traits and safe behavior (0.573) was statistically significant (p<0.05).

Results affirmed that safety motivation in nurses had a significant effect on their safety behavior. Therefore, it is recommended to improve safety motivation through establishing an incentive systems to appreciate the employees who had an appropriate and safe behavior in the workplace.

Ethylbenzene is a volatile organic compound used in many industries, including oil and gas, oil colored and insecticides. Due to the toxic effects of this chemical substance, control and elimination of this vapor is necessary. Photocatalytic degradation is a possible method to remove organic compounds from air. This study was performed to determine the efficiency of photocatalytic removal of ethylbenzene vapor using ZnO nanoparticles immobilized on modified natural zeolite. 

Natural zeolite was first modified with hydrochloric acid and then with diphenyl dichlorosilane. Next, zinc oxide nanoparticles were stabilized on the zeolites. Dynamic air flow and different concentrations of ethyl benzene (25, 50, 100 and 200 ppm) were produced and the removal efficiency of ethylbenzene vapor was investigated using UV/MZe/ZnO. The temperature and relative humidity were set at 25±2°c and 35%. The surface and volume of the pores of the bed were determined by the BET method and surface structure was determined by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD).

Evaluations for BET showed the specific surface areas decreased by increasing the amount of ZnO. XRD analysis and SEM images showed that zeolite structure was stabled and nanoparticles was successfully stabilized on Ze. The results showed that the highest removal efficiency (50.8%) by the process of UV/MZe/ZnO at concentration 25 ppm.

The result of this study showed that the Ze/ZnO catalyst may be an applicable and hopeful method to removal of ethylbenzene from air flow under UV irradiation

Recent evidence indicates that lighting can affect physiological and neurobehavioral human functions, referred to as non-image forming (NIF) effects of lighteffects. This study aimed to determine the effects of illumination levels and correlated color temperature (CCT) on alertness and performance under NIF conditions.

In this study, 22 participants were exposed to light at various levels of illumination, including very low illuminance (<5 lux, control) and light conditions with correlated color temperatures (CCT) of 4000 K, 8000 K, and 12000 K at 300 and 500 lux. The data collection process included recording the power of brainwaves (alpha, alpha-theta, beta, and theta), sleepiness and mood scales, and cognitive performance tests for sustained attention, psychomotor vigilance task (PVT), working memory, and inhibitory capacity.

The results indicated that 500 lux light conditions at correlated color temperatures of 8000 and 12000K significantly reduced normalized alpha, alpha-theta power, subjective sleepiness, and performance compared to the dim light condition. Under illumination levels of 300 and 500 lux, there were no significant differences in the measured values of the variables.

Lighting interventions can be used as a supplement to other strategies for increasing alertness and performance in the workplace.

Working with a computer and workplace conditions expose people to risk factors of musculoskeletal disorders (MSDs). This study aimed to assess posture, examine MSDs, and determine, weigh and prioritize the risk factors among computer users by a neural network algorithm. 

This descriptive-analytical cross-sectional study was conducted in six phases on computer users in 2019. The status of MSDs was determined via Nordic musculoskeletal questionnaire (NMQ). The factors affecting these disorders were determined by the ROSA method, and then these factors were weighed by the neural network algorithm. The data were analyzed in IBM SPSS Modeler.

The mean age and work experience of the users were 34 ± 6.9 and 1.5 ± 0.7 years, respectively. Most of years were observed at the lower back, neck, and upper back, respectively. The final mean scores of the chair, telephone-monitor, and mouse-keyboard were 3.7 ± 1, 3.6 ± 1.1, and 3.65 ± 1.2, respectively and the final mean score of ROSA was 4.4 ± 0.9. The greatest correlation with the ROSA score was observed in chair (R2 = 0.46), followed by telephone-monitor (R2 = 0.43), and mouse-keyboard (R2 = 0.42). The highest predictor importance of the effective factors based on the neural network algorithm prioritization belonged to the chair (48%), followed by telephone-monitor (28%) and mouse-keyboard (24%). The accuracy of the neural network algorithm in examining the effect of factors on musculoskeletal disorders was 98% based on the ROSA score.

Factors affecting years due to working with computers are the chair, telephone-monitor, and mouse-keyboard, respectively, as prioritized by the neural network algorithm. These disorders can be prevented by ergonomic modification of users’ chairs and correct placement of the monitor and telephone.

Previous studies have been conducted on the effects of exposure of industrial workers to high levels of noise and their association with mental health or exposure of people to harmful levels of environmental noise. In this study, we investigated the association between moderate noise levels and the symptoms of depression, anxiety, and stress in non-industrial workers.

This study is a Cross-Sectional study that was conducted using the enrollment phase data of the Tehran University of Medical Sciences Cohort (TEC) study. The study population consisted of 3899 workers of Tehran University of Medical Sciences who were employed in seven occupational groups of the university, Office Workers, Healthcare workers, technical personnel, services workers, security guards, and radiology-radiation units. Exposure to moderate noise level was examined using the Leq10min index, and the Depression Anxiety Stress Scales were examined on the mentioned population by DASS-42 questionnaires.

The results showed that the prevalence of severe to very severe symptoms of depression, anxiety and stress were 8.2, 7.9, and 11% respectively. Also, it was observed that 14.5% of the participants of the study were exposed to noises of more than 70 dB(A). Furthermore, the results indicated that the highest average noise was equal to 71.3 dB(A) for the technical staff group, and the lowest value with an average of 59.1 dB(A) was recorded for the office workers group. The symptoms of severe to very severe depression was associated with exposure to noises above 70 dB(A) (OR:5.22) anxiety (OR:1.16), stress (OR:1.17) and socioeconomic status (OR:1.84). The severe to very severe anxiety was associated with stress (OR: 1.25). On the other hand, the symptoms of severe to very severe stress was associated with variables of age (OR:0.99), gender (OR:0.46), socioeconomic status (OR:1.52), having job management position (OR:0.81) and having healthcare working job (OR:0.65).

Regarding the obtained results of the present study, it was concluded that exposure to moderate noise levels had positive and significant association with depression in non-industrial workers. In non-industrial work environments, exposure to moderate noise levels is and can be independently associated with depression.

Labor is one of the most important wards of hospital, where human error is high. Midwifery errors in the maternity ward and in the delivery can be a serious threat to the health of the mother and the infant, resulting in increased treatment costs. Factors affecting human error are diversity in work, high workload, and fatigue. Therefore, this study aimed to evaluate the midwifery errors in the maternity ward using the systematic human error reduction and prediction approach (SHERPA) technique.

This cross-sectional study was conducted in 2019, during which different midwifery tasks were determined in four stages of admitting, pre-labor, delivery, and postpartum. Tasks and sub-tasks were identified using the hierarchical task analysis (HTA) technique and human error was evaluated using the SHERPA technique.

The results of the HTA technique identified 19 main tasks, 52 sub-tasks, and 114 activities. After assessing human error risk with the SHERPA technique, the performance was the most frequent type of  error and the highest frequency was related to the undesirable risk level.

The errors of the midwifery profession in the hospital’s labor are high-risk and largely critical. Factors such as high workload, time pressure, and fatigue influence the incidence of human error. In order to reduce human error in this area, strategies such as reducing staff workload, developing standard checklists and guidelines are essential to reduce human error in this ward.