Journal of Health and Safety at Work

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Introduction: The purpose of occupational health is to maintain and improve the health of employees and improve their physical, mental and social well-being through the prevention, control and elimination of occupational hazards. It is necessary to integrate educational, research and health service activities to prevent and control potential occupational health hazards in the community. This study aimed to develop a Joint Comprehensive Plan Of Action (JCPOA) for occupational health at Tehran University of Medical Sciences (TUMS).
Material and Methods: In this participatory action research, a strategic planning committee was established, whose members were professors of the occupational health department in the school of public health and managers of the occupational health department in the health deputy of TUMS. The strategic planning committee carried out a strategic evaluation of the internal and external environments of both occupational health deprtments of TUMS and identified the strengths, weaknesses, opportunities and threats. Then, the strategic direction of JCPOA including the vision, mission, values, goals and objectives was determined. Also, the strategies and actions to achieve the goals and objectives were identified. Finally, the action plan to achieve these objectives was developed.
Results: This applied research led to the strategic evaluation of the internal and external environments of the occupational health depratment of the School of Public Health and the occupational health depratment of the Health deputy of TUMS, determining the strategic direction, and finally, developing an action plan to achieve the goals and objectives.
Conclusion: The JCPOA for occupational health was developed using a collaborative and systemic approach. The proper implementation of this plan can lead to the improvement of occupational health indicators in the community. Cooperation between university and industry is necessary for the sustainable development of society.

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Introduction: The design of traffic signs should consider human cognitive abilities to enhance drivers’ understanding of the signs. Cognitive features, as one of the crucial principles of ergonomics, are among the influential factors in the design of signs. The present study aimed to evaluate the effect of graphic elements of eight new sign designs based on cognitive features on conveying the message “prohibition of using mobile phones.”
Material and Methods: This study was conducted in six driving schools in Tehran in 2013. One hundred seventy-four participants, with an average age of 23.5 and a standard deviation of six years, participated in this study. Participants were then presented with the designed signs through a colored questionnaire. They were instructed to evaluate the signs’ cognitive features including simplicity, concreteness, meaningfulness, and semantic closeness—using a Likert scale ranging from 0 to 100. 
Results: The results revealed that the average score of the cognitive features of the designed signs is higher than other traffic, industrial and pharmaceutical signs. In this study, “semantic closeness” was the best cognitive feature for predicting the message of the signs. The sign with the “hands-free” element had the best performance in transferring the message.
Conclusion: This research aimed to identify the most effective of eight proposed signs for banning mobile phone use while driving. Participants rated the sign featuring a button phone with a hands-free symbol as the top choice. Although most of the mobile phones in the market are of the touch screen type and the use of button phones has decreased a lot, the symbol of these phones as the dominant symbol still effectively conveys messages.
 

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Introduction: Disturbing noise can cause physical and mental illnesses among workers; for this reason, it is necessary to restrain it, especially in workplaces. Using sound-absorbing materials with suitable acoustic properties has been a growing trend in mitigating noise. This study aimed to improve the acoustic properties of polyurethane foam (PUF) as a sound absorber.
Material and Methods: In the present study, PUF was synthesized with different percentages of clay nanoparticles (0 -1.2 wt.%), and then the Sound Absorption Coefficient (SAC) of the synthesized PUF was measured by the acoustic impedance tube in the frequency range of 63 to 6400 Hz according to the ISIRI 9803 standard without an air gap behind the sample. The morphology of the foam was also investigated by Scanning Electron Microscope (SEM).
Results: The results showed that the addition of clay nanoparticles to PUF improved the sound absorption behavior of the samples, and the best sound absorption behavior was for PUF with 1.2% weight of nanoparticles at low frequencies (500-2600 Hz). This increase in the absorption coefficient can be due to the increase in the number and smaller size of the pores with the increase in the amount of nanoparticles in PUF.
Conclusion: This study illustrates that the incorporation of clay nanoparticles into PUF at varying percentages results in an enhanced absorption coefficient. The presence of clay nanoparticles leads to a reduction in cell size and an increase in the number of pores, consequently enhancing surface friction. The absorption coefficient was observed to increase with the growing concentration of clay nanoparticles in PUF.
 

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Introduction: People’s risk perception in an emergency situation affects how they behave. During the pandemic of a disease like COVID-19, the fear of the disease and its consequences causes people to deal with anxiety. The present study was conducted with the aim of determining the relationship between the perception of the risk of COVID-19 and the experience of anxiety caused by it among workers in manufacturing industries. 
Material and Methods: The present descriptive-analytical study was conducted cross-sectionally in 2022 among 545 workers of manufacturing industries located in Tehran, Mazandaran and North-Khorasan provinces. In the study, data collection was conducted using three questionnaires: a demographic information questionnaire, the COVID-19 Disease Anxiety Scale (CDAS), and the COVID-19 Risk Perception and Psychological Predictors against COVID-19 questionnaire. Data analysis was done using descriptive (mean and standard deviation) and analytical statistics (Canonical Correlation Coefficients or CCC) in SPSS V25 software.
Results: The mean ± SD of the workers’ age was 35.98 ± 7.58 years, while the scores for risk perception and anxiety were 12.89 ± 3.31 and 4.51 ± 1.51, respectively. The Concordance Correlation Coefficient (CCC) between risk perception and anxiety caused by the COVID-19 disease in the first Canonical point was 0.734, and in the second Canonical point, it was 0.229. The corresponding p-value was found to be less than 0.01. Psychological symptoms (Canonical loading = -0.725) and physical symptoms (Canonical loading = -0.421) played a significant role in predicting the variability of the risk perception of COVID-19.
Conclusion: The perception of risk related to the COVID-19 disease resulted in a decrease in anxiety, having a more pronounced effect on psychological symptoms compared to physical symptoms. Therefore, in times of pandemic outbreaks similar to COVID-19, implementing measures that enhance workers’ awareness and understanding of the disease risks can prove effective in managing anxiety. 

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Introduction: The prevalence of COVID-19 has significantly impacted work environments and the workforce. Therefore, identifying the most important preventive and control strategies, as well as assessing their effectiveness, is of paramount importance. Various studies have shown that machine learning algorithms can be used to predict complex and nonlinear issues, including predicting the behavior of various diseases such as COVID-19 and the parameters affecting it, and can be beneficial. The purpose of this study has been to examine the importance of preventive measures and hygiene behaviors in preventing COVID-19 in the oil refining industry using various machine learning models.
Material and Methods: For this purpose, demographic information and health behaviors of individuals were collected. Subsequently, a multi-layer perceptron (MLP), radial basis function (RBF), and support vector machine (SVM) models were compared to enhance the analysis of the effects of preventive measures on COVID-19 infection. Finally, the most influential factors affecting the likelihood of COVID-19 infection were determined using sensitivity analysis.
Results: The results showed that the accuracies achieved in predicting the impact of preventive measures and health behaviors on COVID-19 in occupational settings were 78.1%, 81.2%, and 78.1% by MLP, RBF, and SVM respectively. The RBF model was identified as the most accurate model for predicting the impact of health behaviors on COVID-19 disease Additionally, the level of social distancing with customers, handwashing frequency and disinfection, the availability of cleansing and disinfecting agents for hands and surfaces in the workplace, and gatherings for eating meals and snacks were identified as the most significant health behaviors influencing the prevalence of COVID-19 in the workplace.
Conclusion: Studies of this nature can underscore the importance of attention to preventive measures and health behaviors in unprecedented circumstances. Furthermore, the utilization of artificial intelligence models and tools such as DSS (Decision Support Systems) can serve as powerful tools for optimizing control measures in work environments.
 

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Introduction: The goal of this study is to investigate how the development of technology has affected the industry (especially the mining industry). For this purpose, this paper examines the impact of intelligent mining machinery systems, including tire pressure monitoring systems (TPMS), dispatching systems, and vehicle health monitoring systems (VHMS), on health, safety, and environmental parameters and preventative maintenance.
Material and Methods: This study is descriptive-analytical research that was conducted between time intervals before and after employing the intelligent mining machinery systems. Initially, parameters were identified using the Delphi method. These parameters include human accidents, equipment accidents, environmental incidents, warnings and fines in the domains of health, safety, and the environment, tire usage parameters, the shelf life of the tire, oil overfill, fuel consumption, failure rate, mean time between failures, and preventive maintenance compliance schedules in the domain of preventative maintenance. The effectiveness of using these systems was then assessed by comparing the state of the specified parameters before and after the introduction of the intelligent mining machinery systems.
Results: The findings of this research indicate that using intelligent mining machinery systems will decrease equipment accidents by 33.3%, extend the useful life of tires by 7.1%, reduce fuel consumption by 14.6%, cut the mean time required to repair by 25.5%, and enhance preventive maintenance compliance schedules by 5.7%.
The findings showed the effectiveness of the use of intelligent systems of mining machines was obtained as follows: reduction of equipment accidents by 33.3%, increasing the useful life of tires by 7.1%, reducing fuel consumption by 14.6%, reducing the average downtime of the car for repair by 25.5% and increasing compliance with the maintenance program by 5.7%.
Conclusion: Utilizing intelligent mining machinery systems might have a positive impact on the safety of machines, reduce negative environmental effects like fuel consumption, and improve the maintenance of heavy machinery, which would lead to better mining conditions and lower costs.
 

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Introduction: Emergency technicians face workplace violence and increasing occupational stress. The purpose of this study was to investigate the impact of a virtual self-management training in communication skills on occupational stress and the degree of aggression among emergency technicians.
Material and Methods: This study involved 60 emergency technicians randomly assigned to either the intervention or control group. They completed surveys on workplace violence and occupational stress. The intervention group received six weeks of a virtual self-management training in communication skills. Data was collected after two months and analyzed using SPSS software.
Results: The findings showed that there was no statistically significant difference between the control group (110.08±11.92) and the two intervention groups (114.39±11.25) in terms of the average occupational stress before the intervention; The average job stress score between the intervention (94.0±12,70) and control (98.81± 20,81) groups significantly differed following the intervention (p=0.034); After the intervention, the intervention group had lower verbal and physical abuse frequencies compared to the control group.
Conclusion: The virtual self-management communication training demonstrated the potential to reduce occupational stress but did not significantly decrease the violence towards the emergency technicians. A comprehensive training program addressing violence factors and communication techniques, implemented over a longer period, is recommended.

 

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Introduction: Steel erection is known as one of the most hazardous construction activities. From an occupational health and safety perspective, this process carries high risk. Therefore, this study aims to conduct a qualitative risk analysis of steel structure assembly and model it using the Functional Resonance Analysis Method (FRAM).
Material and Methods: In this cross-sectional study, the construction site of a high-rise building steel structure was first visited to identify the main processes involved. Then, semi-structured and open-ended interviews were conducted with 33 workers partaking in this process. Data from the interviews and process identification were entered into FRAM Model Visualiser (FMV) software to investigate and model complex relationships and interactions between daily tasks.
Results: Of the 19 major system component functions identified, four functions had potential instability and defects due to complex human, organizational, and technological function interactions. By intensifying the FRAM graphic model, risks may be imposed on the system if the interactions of these four functions are neglected. These include coordination with the experienced rigger, preparation of the tower crane, attachment of parts at the installation site, and execution of the rescue rope.
Conclusion: The findings demonstrate that conducting qualitative risk assessment and modeling the steel frame construction process using FRAM allows for an in-depth understanding of nonlinear conditions and dynamics resulting from escalating technical-social interactions. This approach enables a comprehensive analysis of system safety status.
 

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Introduction: Acceptance of Health, Safety, and Environment (HSE) rules plays a crucial role in determining the performance of employees in HSE-related areas at the workplace. This study aimed to design a questionnaire to investigate influential factors on acceptance of HSE rules among employees.
Material and Methods: The face validity of the survey was assessed by ten individuals from the target population, while content validity was evaluated by ten HSE experts using both quantitative and qualitative methods. The impact scores were calculated for the quantitative assessment of face validity, and the Content Validity Ratio (CVR) and Content Validity Index (CVI) values were used to assess content validity. Construct validity was determined through Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) involving 506 participants. The reliability of the survey was evaluated using Cronbach’s alpha and the Intraclass Correlation Coefficient (ICC).
Results: All items in the survey showed satisfactory levels of impact score (>1.5), CVR (>0.69), and CVI (>0.79). The mean values for the Impact score, CVI, CVR, and S-CVI-UA were 4.26, 0.963, 0.944, and 0.62, respectively. The survey and its dimensions demonstrated strong reliability, as indicated by Cronbach’s alpha and ICC values exceeding 0.70. Additionally, EFA successfully identified the structure of the questionnaire, and CFA confirmed its goodness of fit.
Conclusion: The Persian version of the questionnaire demonstrated satisfactory validity and reliability. This instrument can be effectively used to assess the factors that influence the acceptance of HSE rules among employees in various workplace settings.

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Introduction: The accurate evaluation of error probability and risk is important. Accordingly, this Comparative study was conducted to evaluate the risk of human error in emergency situations using SLIM and Fuzzy SLIM techniques in fierfighting tasks.
Material and Methods: This cross-sectional and descriptive-analytical study was conducted among 12, using Fuzzy SLIM and SLIM techniques. 39 sub-tasks were studied in 4 phases (Awareness, Evaluation, Egress and Recovery). Considering the advantages of the Fuzzy SLIM method, fuzzy logic was used in weighting of performance shaping factors (PSF). Excel software was used to calculate the probability of error. Also, correlation and kappa statistical tests were used for data analysis in SPSS software.
Results: The mean and standard deviation of human error probability in different sub-tasks of firefighting in SLIM and Fuzzy SLIM methods were 0.095357 ± 0.026193 and 0.06490 ± 0.051748, respectivly. In 48.7 percent of the sub-tasks, the probability category of human error and the assessed risk were the same; however, in 89.7 percent of the sub-tasks, the estimated level of risk was the same in both methods. Correlation test showed that the correlation coefficient of error probability values between the two methods was 0.32, which indicated a moderate correlation in this regard. Additionally, the results of kappa statistical test for the estimated level of risk showed that there is a high agreement between Fuzzy SLIM and SLIM (P value <0.05).
Conclusion: The results of the study indicated meaningful agreement and a moderate correlation between Fuzzy SLIM and SLIM. Therefore, due to the relatively high accuracy of Fuzzy logic methods, and also the long steps of implementing the SLIM method, the Fuzzy SLIM method can be a good alternative to this method.

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Introduction: Lifting loads in awkward postures is a main cause of low back musculoskeletal disorders. In this context, researchers have used various indicators to determine the relationship between biomechanical variables and the risk of these disorders. This study aimed to investigate the correlation between plantar pressure distribution and the values of UTAH back-compressive forces (BCF) and lifting index (LI) during symmetrical load-lifting tasks.
Material and Methods: Thirteen healthy men, aged 25 to 35, took part in this study. The participants were instructed to symmetrically lift loads weighing 7.5 kg and 15 kg in 15 different postures, considering three horizontal distances (A, B, C) and five different heights (1-5). Pressure on the foot soles was recorded using 16 force-sensitive resistors (FSR) corresponding to eight anatomical areas on each foot. The BCF and LI were also calculated using the UTAH method and the NIOSH equation, respectively. Statistical analysis was performed using SPSS (version 21) software.
Results: Based on the results, when the load was closest to the body (A1-A5), the highest pressure was recorded in the heel and the 4th and 5th metatarsal of both feet. In lifting a load of 15 kg in the A2, B1, B2, C1, C2 postures and lifting a load of 7.5 kg in the C2 posture, the average BCF exceeded 700 pounds. The LI was greater than 1 for specific postures (B1, B2, B4, B5, C1-C5) at 15 kg and (C1, C2, C4, C5) at 7.5 kg load-lifting. During the 7.5 kg and 15 kg load-lifting, there was a significant correlation between the plantar pressure and the values of LI and UTAH (p-values < 0.05) in most postures.
Conclusion: The results showed a significant correlation between plantar pressure distribution and load-lifting postures. The study findings, which identify risk levels associated with lifting postures, lay the groundwork for future research aimed at categorizing safe and unsafe plantar pressure patterns.

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Introduction: One of the ways to produce electricity in power plants is to use gas turbines and generators. Due to the use of methane gas as the fuel of the burners and the high rotation speed, this equipment has a high DOW index level, therefore, if the hazardous conditions in the gas turbine are not controlled by the safety instrumented system and the process is not directed to a safe state, Catastrophic events will occur such as fire and explosion and damage to property and people as well as interruption of the power generation process will happen in the long term, so gas turbine safety instrumentation systems can be considered as “critical safety systems”. Therefore, the reliability and availability of their function should be evaluated. The purpose of this research is to determine and verify the safety integrity level (SIL) related to the safety instrumented function (SIF) of the gas turbine and generator in a combined cycle power plant.
Material and Methods: In this study, the safety integrity level was determined by using two methods, Calibrated Risk Graph (CRG) and Independent Protection Layer Analysis (LOPA), and to verify the safety integrity level, the requirements related to random hardware failure, hardware failure tolerance, and systematic capability are considered according to IEC 61511 and IEC 61508 standards.
Results: The results of a case study in gas turbine and generator showed that the LOPA method is more quantitative than CRG and provides more details of independent protective layers, so it is a more suitable method for determining SIL. The SIL verification results show the SIL2 level, closer to the LOPA results.
Conclusion: The obtained results show that the function of the studied gas turbine safety instrumentation system has a suitable level of reliability and availability and is well responsive to risky conditions and possible deviations. The present approach helps safety engineers and instrumentation engineers to calculate the reliability and availability of the Function of the safety instrumentation systems of their process equipment and ensure its acceptability or not.

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Introduction: Protection of the respiratory system has been a vital, and for this purpose, various solutions have been proposed, including the use of masks. One of the most important parameters to measure the effectiveness of the mask against the penetration of microbial agents. The present study was conducted with the aim of evaluating the bacterial and particle filtration of medical masks.
Material and Methods: To assess bacterial performance, the national standard 6138, compliant with EN14683, and Type I medical masks were utilized. Staphylococcus aureus bacterial suspension was prepared and passed through the mask using a nebulizer and through an impactor with a flow rate of 28.3 l/min. Plates containing soy agar were placed in the impactor. Subsequently, all plates were incubated, and the bacterial filtration efficiency (BFE) of the masks was determined by counting the bacterial colonies that passed through the mask’s media as a percentage of the total bacteria. It is worth noting that the pressure drop and particle filtration efficiency were also determined for all masks
Results: Based on the results of the particle removal performance for the particle size of 3 µ, the masks were categorized into three groups with efficiency above 99%, above 95% and 90%. According to the standard, all masks had an acceptable pressure drop below 40 Pa. The acceptable bacterial filtration rate for type I masks should be above 95%. The results showed that type A and B masks have an acceptable bacterial filtration rate and there is a significant correlation between the types of masks examined in terms of bacterial and particle efficiency.
Conclusion: The results showed that different types of masks under investigation have significant differences in terms of particle capture efficiency and bacterial filtration performance. In addition, there is a significant correlation between bacterial and particle filtration efficiency.
 

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Introduction: Obesity and overweight are major global health challenges. One of the bad effects of noise that has been recently expressed is the effect of noise on obesity. This study aimed to investigate the effect of high-frequency noise exposure on obesity, food intake, and abdominal visceral fat in adult male guinea pigs.
Material and Methods: The animals in this study were 24 adult male guinea pigs randomly divided into 3 groups (control and two case groups). Each case group was separately exposed to high- frequency white noise with sound pressure levels in 65 dB and 85 dB for 5 days per week in 30 days. The food intake was measured daily. The weight of animals was measured at the start and on days 6, 12, 18, 24, and at the end of exposure period. The abdominal visceral fat was extracted and weighted at the end of the study period. The data were assessed using SPSS V.22 software.
Results: ANOVA analysis showed that exposure to high-frequency noise at 65dB and 85dB had a significant effect on weight gain, food intake, and abdominal visceral fat weight (P-value< 0.05) which in the group exposed to the noise with 65 dB was more than other groups.
Conclusion: Based on this study, exposure to high-frequency noise may be an effective factor in obesity and increasing abdominal visceral fat. Further studies are needed to investigate the mechanism affecting weight status following noise exposure.
 

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Introduction: Improving health and the environment is one of the components of development, social welfare, and economic growth. Another influential factor in increasing health costs and reducing social welfare is work-related accidents and diseases, which impose high costs on individuals, industries, and the national economies of countries. Therefore, using multi-criteria decision-making methods, the present study provided a conceptual model to identify and rank work-related diseases’ environmental and health costs.
Material and Methods: The present study was conducted in 2023. A classification model for the economic evaluation of environmental and health costs of occupational diseases was developed to achieve the study’s aim. In the current research, the Delphi method was used to identify health and environmental criteria, and the Analytic Network Process (ANP) was used to weight the sub-criteria. Finally, the cost of health and the environment was estimated based on the available information. Naft Tehran Hospital (NSHT) was also selected as a case study site.
Results: The results showed that the drug and medical equipment cost factor, with a weight of 0.312 in the treatment sector, and the particular and infectious waste cost factor, with a weight of 0.085, were the most critical factors in the economic evaluation. Also, the parametric model results showed that 99.84% of the total costs are related to health costs, and 0.16% are related to environmental costs. In general, the results of this research showed that 61.3% of the costs of the health sector are related to the two sectors of medicine and medical equipment and the cost of service personnel, and 91.7% of the costs of the environmental sector are related to wastewater treatment and the cost of electricity consumption.
Conclusion: This study presented a semi-quantitative model to estimate health and environmental costs caused by occupational diseases. The results can create a novel scientific insight into implementing control measures using the optimal point of cost-benefit parameters. Implementing this integrated model can be a practical and effective step in allocating resources and prioritizing interventions.
 

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Introduction: Considering the abundance and the large number of workers employed in micro and small industrial workshops in Iran and the importance of workers’ health, the present study aimed to investigate the mediating role of chronic fatigue in the relationship between mental workload and work ability with cognitive failure using path analysis.
Material and Methods: This study was conducted using a cross-sectional design on a sample of workers employed in micro and small industrial workshops in the city of Eghlid. Data were collected utilizing various measures, including demographic and occupational information questionnaires, the NASA Task Load Index (NASA-TLX), the Work Ability Index (WAI), and questionnaires for chronic fatigue and cognitive failure. The correlation test and path analysis modeling were used in SPSS (version 24) and AMOS softwares to investigate the relationship between variables.
Results: The mean scores of mental workload, work ability, chronic fatigue, and cognitive failure  
were 69.63, 35.20, 15.58, and 53.30, respectively. The values of the goodness of fit indices lead to  
the confirmation of the conceptual model by the research data. Also, based on the findings of the path analysis, the current research model has a good fit (CFI=1.00, GFI=0.998, NFI=0.999, AGFI=0.98 and RMSEA=0.003(0.00,0.169)).
Conclusion: The path analysis results indicate that chronic fatigue plays a significant mediating role  
in the relationship between mental workload and work ability with cognitive failure. A better understanding of the mediating mechanisms and complex effects of these relationships can contribute to improving the management of chronic fatigue and enhancing cognitive performance in the workplace.
 

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Introduction: Driving has various harmful factors due to its nature, which affect drivers’ health directly and indirectly. Therefore, it is necessary to know the situation and prevalence of these factors in drivers to implement preventive measures.
Material and Methods: This cross-sectional study is a part of a cohort study conducted (2016 to 2018) among the professional drivers of Shahroud, Iran. Data related to background information, blood pressure, height, weight, waist circumference, body mass index, blood factors, hearing loss (dB), respiratory performance indicators, sleep disorders, and accidents were collected from the participants with standard tools and methods.
Results: This study examined 1461 male professional drivers with an average age of 37.30±6.96 years. A total of 426 participants had metabolic syndrome. 797 and 942 people had different degrees of hearing loss, respectively, in the right and left ear. About 129 people had obstructive sleep apnea, and 1330 people had insomnia. Investigations showed that 351 drivers had at least one accident.
Conclusion: This study showed the prevalence of health risk factors in professional drivers at the examined time point. Considering the vital role of drivers in transportation and the country’s economy, it seems necessary to pay more attention to the health of this occupational group. Regular health screening, healthy lifestyle training, improvement of working conditions, and stress management are some interventions that can effectively improve drivers’ health.
 

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Introduction: A wood-wool cement panel (WWCP) is wood wool combined with Portland cement mortar. This environmentally friendly acoustic material can be used as a thermal insulator and fire-resistance material with desired mechanical properties. This study aimed to determine the mechanism by which WWCP absorbs sound and the effect of production and application parameters on absorption
Material and Methods: The samples were prepared from poplar wood wool and white Portland cement as a binder in two Cement Fiber Ratios (CFR), namely 2:0.7 and 2:0.95, with bulk densities of 400, 500, and 600 Kg/m3 and thicknesses of 2 and 4 cm. Three layers of backing: air, polyurethane foam, and glass wool were examined separately. Acoustic absorption coefficient was measured using an impedance tube based on ISO 10534-2.
Results: The highest increase in the average absorption coefficient due to the increase in thickness was observed for the sample with a density of 400 kg/m3 and CFR = 2: 0.95, equal to 0.3. Increasing the bulk density to 500 kg/m3 for most samples and in the high-frequency range led to rising absorption efficiency. The optimal backing effect was due to the placement of 4 cm of polyurethane foam behind the sample, which in both thicknesses led to an absorption peak with an absorption coefficient higher than 0.95 at frequencies between 400 and 500 Hz. Selected samples showed that painting WWCPs led to a limited drop in absorption coefficients at high frequencies, comparing the before and after painting results with oil-based paints.
Conclusion: Tuning the absorption frequencies of these absorbers can be achieved by altering factors such as the thickness or density. It has been demonstrated that the effects of thickness and bulk density on the sound absorption of WWCP are related to each other. Concerning the CFR values, increasing the density did not significantly affect absorption in the two frequency ranges.

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Introduction: One of the questions that always arises in the minds of researchers, especially young researchers, is what pattern the progress of science follows in their field of expertise and what is the direction of the studies. The purpose of this study is to analyze the content of the studies published from 2011 to 2022 in Persian scientific journals in the field of workplace safety and determine the direction and scientific process of studies in this field.
Material and Methods: All the studies published from the years 2011 to 2022 in the Persian scientific research journals ”Iran Occupational Health”, “Occupational Health and Safety”, “Occupational Health Engineering”, ”Iranian Journal of Ergonomics”, “Occupational Medicine” and “Occupational Health and Health Promotion” were gathered using census method from the websites of the journals. In total, 595 published articles were categorized according to the thematic codes determined by the opinion of experts, the theme of “risk analysis, assessment, and risk management” had the highest percentage of frequency (18.66 percent), while the theme of “safety application in other industries or specific workplaces” had the lowest frequency of percentage (0.34 percent). Approximately 50 percent of the variance of the published studies explained the themes of “risk analysis, risk assessment, and management”, “inspection, analysis and modeling of accidents”, “human error and safety”, “social, organizational factors, culture, safety climate, and behavior-based safety”.
Conclusion: The existing trends emphasize the importance of learning lessons from accidents as a reactive approach and risk management, human factors, and behavioral aspects in safety interventions as a preventive approach. The research development of the country’s safety at the workplace should be further improved with new policies in different fields while taking advantage of international scientific advances on the specific functions and challenges of the country and with a problem-oriented approach.