Journal of Health and Safety at Work

---

Introduction: In all societies, tools and equipment are generally designed for right-handed people, who make up approximately 90% of the population, but left-handed and ambidextrous people (those who use both hands in manual activities) also live among us. Even in delicate and sensitive jobs. This research investigated the relationship between the spectral effect of the dominant hand and grip strength and hand dexterity.
Material and Methods: A cross-sectional study was designed to measure the power and precision grip of 182 adult participants (56% female and 44% male). The dominant hand of the participants was determined using the Edinburgh Dominant Hand Questionnaire. Power grip strength was measured using the Constant 14192-709E. Pinch grip test was performed using Saehan Hydraulic Pinch Gauge SH5005 for both hands separately. Dexterity of both hands was also measured using the Pegboard 32020A tool.
Results: Power and precision grips were more common in men than in women (P<0.001). Power grip differed between right- and left-handed women (P=0.019), with right-handed women having greater grip strength. The Precision grip of left-handed men was significantly (P<0.001) greater than that of right-handed men. Hand dexterity of left-handed men was significantly (P<0.001) higher than that of right-handed men. Two-handed agility (P<0.001) and assembly dexterity (P<0.001) are significantly higher in ambidextrous people than in right- and left-handed people.
Conclusion: The power, precision grip and dexterity are different between women and men. The grip strength of men is stronger than that of women. Ambidextrous people have more dexterity and assembly agility, so in jobs that require the use of two hands, they perform better and will be recommended for employment in this category of jobs. 

---

Introduction: Despite the numerous studies on occupational noise-induced hearing loss, there is limited documentation on the vibration effects on the workers’ auditory system. Heavy equipment drivers are exposed to high levels of whole-body vibration (WBV) and noise. Therefore, this study aims to investigate the heavy equipment drivers’ auditory response to WBV exposure and combined exposure to noise and WBV.
Material and Methods: 30 male heavy equipment drivers with an average age of 32.40 ± 4.91 years participated in this study, which was designed based on the repeated measurements model. During 3 defined scenarios of exposure to WBV, combined exposure to noise and WBV, as well as the scenario without exposure, the drivers’ auditory response was measured using distortion product otoacoustic emissions (DPOAE). Statistical analyses were performed by IBM SPSS-25 software.
Results: The range of heavy equipment in-cabin noise was 84-89 dB. Also, the most exposure of drivers to WBV was obtained in the Z axis with an average acceleration of 1.29 m/s2. The DPOAE amplitude of the drivers in all three investigated scenarios showed significant changes (P<0.05); But in comparison between different scenarios, exposure to WBV and combined exposure to noise and WBV had a significant effect on the response of the auditory system of the participants in the study compared to the scenario without exposure (P<0.05). Also, there was a significant difference in the changes of the DPOAE amplitude in different frequencies; Thus, the most changes in the DPOAE amplitude were observed in the frequencies of around 4000 Hz.
Conclusion: The results of this study showed the damaging consequences of exposure to noise and WBV on the auditory response; In addition, the present study provided evidence of synergistic effects of combined exposure to noise and WBV on heavy equipment drivers.
 

---

Introduction: Micro-perforated panel (MPP) absorbers are emerging as next-generation absorbers due to their considerable advantages. However, their main drawback compared to other absorbers is their limited bandwidth. This study aims to investigate methods for enhancing the bandwidth of an MPP in the frequency range of 1 to 1500 Hz through simulation using the Finite Element Analysis (FEA) in COMSOL software.
Material and Methods: The modeling was conducted using FEA in COMSOL version 5.3a. To increase the bandwidth, techniques such as series-parallel configurations, symmetrical and asymmetrical air gap depths, and the incorporation of two porous absorbing materials in symmetric and asymmetric air gap layers were employed. In the initial phase, the best configuration was selected and retained for the subsequent stages.
Results: The optimal arrangement involved two upper MPPs having larger holes and a lower perforation percentage compared to the two lower MPPs. It was also found that increasing the depth difference between the air layers of the upper and lower MPPs led to a greater increase in bandwidth than when they were closer together. Furthermore, the use of fibrous porous materials in one of the layers resulted in a reduction of resonance peak while enhancing the bandwidth.
Conclusion: MPP absorbers exhibit diverse behaviors due to their Helmholtz structure and parametric design. If their constituent parameters are tailored to match the acoustic characteristics of the target sound, they achieve optimal efficiency. Additionally, employing numerical methods such as FEA serves as a suitable alternative to more costly laboratory methods.

---

Introduction: Despite advancements in road safety and vehicle design, road accidents remain prevalent, a quarter of which are caused by driver distraction. This issue is particularly critical in the public transport sector, especially among urban bus drivers, as distraction can lead to serious injuries and fatalities. Accordingly, this study explored the factors influencing distraction among urban bus drivers through a qualitative approach and a macroergonomics perspective.
Material and Methods: In this study conducted in 2024 in Tehran, 18 urban bus drivers were selected through cluster sampling. The participants included 10 drivers from bus rapid transit (BRT) system and 8 drivers from non-BRT services. Data were collected through semi-structured interviews with the drivers as well as on-site observations. Subsequently, a directed qualitative content analysis approach, based on the balance theory model, was used to analyze the collected data.
Results: The findings revealed that the primary sources of distraction belonged to six levels of the work system, the most cited of which were environment, tasks, and organization. Specifically, inappropriate behavior of other street users as an environmental factor and the driver’s interactions with passengers as task-related factors were identified as key sources. Additionally, organizational factors such as interactions with supervisors and colleagues, as well as salary issues, were significantly important. The participants very limitedly expressed using mobile phone while driving as a main distractor to their driving.
Conclusion: The current study identified various influential factors, spanning different levels of the work system, affecting bus drivers’ distraction, including generic factors that impact all urban drivers and specific factors that uniquely affect bus drivers. Addressing these factors through providing appropriate education for both passengers and street users along with implementing management strategies in the organization to enhance intra-organizational relationships and organizational support can lead to the safety of the bus drivers.
 

---

Introduction: Operating room personnel are involved with occupational physical activities such as repetitive bending, holding surgical tools and standing for long hours that can lead to musculoskeletal disorders (MSDs). Low back pain (LBP) is the most prevalent and costly problem among these disorders. The aim of this study was to determine the relationship between occupational physical activity, LBP and disability among operating room personnel.
Material and Methods: A total of 60 operating room personnel voluntarily participated in the study, all of which had at least two years of working experience. At the end of a working week, the degree of disability and pain were assessed by Graded Chronic Pain (GCP) questionnaire. The International Physical Activity Questionnaire (IPAQ) was used to evaluate the level of physical activity. Simple linear regression was conducted to investigate the relationship between physical activity, LBP and disability. 
Results: The survey using the GCP questionnaire revealed that 58.3% of participants reported experiencing occupational back pain, while 41.7% reported no back pain.  Among those with back pain, the average pain intensity was rated 43.11 (18.22) on the scale.  Pain remained stable for an average of 2.3 days (standard deviation = 0.95).  The average level of disability associated with back pain was 32.09 (27.44). Statistical analysis using simple linear regression showed a significant relationship between back pain and several factors: vigorous physical activity (p-value = 0.02), prolonged sitting time (p-value = 0.01), and chronic pain (p-value < 0.001).
Conclusion: Occupational physical activity characterized by low intensity, but high repetition and standing for a long time in fixed postures were the most significant contributors to lumbar back pain among operating room personnel. Chronic pain in this population was reported as grade 2, indicating severe pain with minimal disability; if left unaddressed, this could lead to movement restrictions.

---

Introduction: A significant contributor to noise pollution in urban areas is automobile exhaust systems, wherein mufflers, as passive devices, are designed to mitigate the noise produced. The dimensions, shape, and configuration of the muffler, along with its associated components and pipes, influence its effectiveness in sound transmission loss. This study investigates the impact of varying the length of the muffler’s connecting pipes and their associated holes on sound transmission loss in reactive mufflers, utilizing software simulation for analysis.
Material and Methods: The research utilized COMSOL 5.5 to simulate the effects of different geometric factors on sound transmission loss in mufflers. Modifying factors such as the length of connecting pipes and the existence of holes led to the development of various designs. Analysis of the results was conducted to assess the impact of each parameter on sound attenuation, enabling a straightforward comparison of acoustic efficiency.
Results: Studies demonstrate that changing the form of pipes at different frequencies produces diverse outcomes. Introducing a perforation prior to the tube and utilizing elongated connecting tubes with expansion chambers can enhance transmission attenuation. On the other hand, transmission loss decreases with longer pipes that lack holes. Lower pitches experience minimal attenuation, whereas higher pitches undergo more loss. Reactive mufflers work best at certain frequencies, where the length of the connecting pipe affects both the acoustic mass and the effectiveness of the muffler.
Conclusion: The results obtained from this study can inform the optimal design of mufflers aimed at enhancing their efficacy in sound transmission loss. Furthermore, it is essential to consider the synergistic impact of the geometrical configurations of the internal pipes within the muffler to minimize sound emissions from the exhaust outlet.
 

---

Introduction: The Total Quality Safety Management (TQSM) model is a tool used to assess the performance of occupational health and safety (OHS) management. This study evaluated the OHS management performance in two edible oil production factories using the TQSM model.
Material and Methods: A total of 78 OHS-related evaluation criteria across four main areas of the TQSM model were assessed at the Saboos Mazand (Factory 1) and Mino Caspian (Factory 2) factories, located in Mazandaran Province, Iran. The four areas included Total Quality Management (TQM), the ISO 9001 Quality Management System guidelines, the Voluntary Protection Program (VPP), and Process Safety Management (PSM). The study population consisted of 20 individuals from each factory, including managers, supervisors, and members of the OHS Committee, all with at least one year of experience in their respective roles. Participants were selected using a convenience sampling method.
Both factories had established active management systems for quality management (ISO 9001), customer satisfaction management (ISO 10002), and Hazard Analysis and Critical Control Points (HACCP) at the time of the study, reflecting the nature of the industry.
Results: The total scores achieved by Factory 1 and Factory 2 across the four main areas were as follows: 52.11 and 51.8 in the TQM area, 43.94 and 45.5 in the QMS-ISO 9001 area, 45.23 and 46.45 in the VPP area, and 30.22 and 30.06 in the PSM area. The overall scores obtained in the TQSM model were 171.51 for Factory 1 and 173.81 for Factory 2, corresponding to 54.97% and 55.7% of the maximum achievable score, respectively. No significant difference was observed between the mean scores across the four areas of the TQSM model for the two factories (p > 0.05).
Conclusion: Both factories exhibited an overall average performance level in OHS management. The evaluation criteria across the four areas of the TQSM model indicated weak to moderate conditions in the assessed subareas. Effectively using this model highlighted the organizational and operational areas requiring increased effort and focus to enhance OHS management performance in both factories.

---

Introduction: Individual work performance (IWP) plays a crucial role in both organizational effectiveness and employee well-being. To address the limitations of existing job performance questionnaires, the Individual Work Performance Questionnaire (IWPQ) was developed based on a holistic and systematic framework. This study aimed to translate, culturally adapt, and evaluate the psychometric properties of the Persian/Farsi version of the IWPQ.
Material and Methods: This descriptive methodological study was conducted in two stages: (1) translation and cultural adaptation (assessment of face and content validity), and (2) psychometric evaluation (assessment of internal consistency, test-retest reliability, and construct validity). The sample consisted of 206 administrative employees with a mean age of 34.29 years (SD = 7.66) and an average work experience of 8.48 years (SD = 7.39). The IWPQ was translated using forward and backward translation methods, and its validity was evaluated using exploratory and confirmatory factor analyses.
Results: The Persian IWPQ demonstrated acceptable face and content validity. Exploratory factor analysis confirmed a three-factor structure: task performance, contextual performance, and counterproductive work behavior. Confirmatory factor analysis indices (e.g., CFI = 0.87, SRMR = 0.08 and RMSEA = 0.09) indicated a approached model fit acceptability. Internal consistency and test-retest reliability were satisfactory across all dimensions (Cronbach’s alpha > 0.70 and ICC > 0.80).
Conclusion: The Persian version of the IWPQ is a reliable and valid instrument for assessing individual work performance across diverse occupational groups. It provides a valuable resource for evaluating workplace interventions and strategies aimed at enhancing performance.

---

Introduction: Nurses play a crucial role in hospital settings, often undertaking demanding tasks that exceed their physical and cognitive capacities. The Structured Multidisciplinary Work Evaluation Tool (SMET) is an instrument for evaluating and identifying risks in workplace environments. The objective of this study was to assess the psychometric properties of the Persian (Farsi) version of the SMET.
Material and Methods: In this cross-sectional study, the face and content validity of the questionnaire were evaluated both qualitatively and quantitatively by a panel of 13 experts. Quantitative content validity was performed using the Content Validity Ratio (CVR) and Content Validity Index (CVI). Reliability was measured using Cronbach’s alpha and Intraclass Correlation Coefficient (ICC).
Results: The face validity assessment revealed that questions 3, 4, 6, 23, and 24 required clarification. The CVI for all items was calculated to be above 0.79. However, several questions had a CVR below 0.54, indicating that specialists considered some questions unnecessary or repetitive. Consequently, these questions were either removed or merged with similar items based on the scores and subsequent reviews. Cronbach’s alpha and ICC values for the entire questionnaire and its dimensions were above 0.7, indicating acceptable to strong reliability.
Conclusion: The Persian version of the SMET questionnaire demonstrated acceptable psychometric properties for comprehensive multifactorial evaluation of healthcare workplaces.

---

Introduction: Wearable thermal management systems and phase change materials (PCMs) have emerged as effective solutions for regulating body temperature and storing thermal energy. This study focuses on synthesizing and thermal optimizing a sodium sulfate decahydrate-based nanocomposite incorporating various nanoparticles to improve its performance for personal thermal regulation applications.
Material and Methods: The composite was prepared using sodium sulfate decahydrate as the base PCM. Potassium chloride (KCl) was added to adjust the melting point, borax (STD) served as a nucleating agent, and sodium polyacrylate (SPA) was included as a thickening agent to suppress phase separation. To evaluate the effect of nanoparticle additives, 0.05 wt.% of aluminum oxide (Al₂O₃), iron oxide (Fe₂O₃), graphene oxide (GO), and titanium dioxide (TiO₂) were separately incorporated into the base formulation. A field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the resulting nanocomposites. Differential scanning calorimetry (DSC) assessed thermal properties, including phase transition temperatures (melting and freezing points) and latent heat.
Results: Differential scanning calorimetry (DSC) analysis indicated that sample S-5-5 comprising sodium sulfate decahydrate with 3 wt.% KCl, 5 wt.% STD and SPA exhibited a melting temperature of 29.5 °C and a latent heat of 120 J/g. This composition remained stable without phase separation. The incorporation of nanoparticles raised the melting point of the base PCM by 0.6 to 1.72 °C. Aluminum oxide (Al₂O₃) and iron oxide (Fe₂O₃) reduced the latent heat of fusion, whereas GO and TiO₂ increased it.
Conclusion: These findings confirm that the thermal properties of sodium sulfate decahydrate-based PCMs can be tailored by including specific additives and nanoparticles. Hydrated salt nanocomposites demonstrate strong potential as PCMs for wearable body temperature regulation.

---

Introduction: Demographic changes are an inevitable phenomenon in today’s organizations. By acknowledging the aging of the workforce as a significant organizational challenge, the purpose of this research is to design a structural model of elderly-oriented human resource management measures in public organizations.
Material and Methods: This study is categorized as applied in terms of objective, descriptive-survey in terms of approach, and a mixed-method design (qualitative-quantitative) in terms of data collection. The information gathering tools used to review the research literature were library research methods, while a questionnaire was employed for collecting field data. Initially, the Delphi method was utilized to extract and identify elderly-oriented human resource management practices. In the second phase, a quantitative method was used to validate the model of elderly-oriented practices in public organizations and assess the current status of these practices.
Results: The results obtained from the model’s goodness-of-fit in SmartPls 3 software and confirmatory factor analysis indicated high validity of the elderly-oriented human resource management practice model.
Conclusion: Additionally, the findings revealed that, from the perspective of the study’s employees, the status of elderly-oriented human resource management practices in terms of implementation was not in a desirable state and did not meet employees’ expectations.

---

Introduction: Safety in healthcare facilities is critically important for the health and well-being of employees, patients, and organizational effectiveness. In recent years, various studies have examined the relationship between leadership styles or approaches and safety performance as one of the indicators of safety promotion. The present systematic review examines the relationship between different leadership styles and the safety performance of employees in healthcare facilities to provide a better understanding of the positive or negative effects of leadership on safety and to suggest strategies for improving safety performance in healthcare facilities. 
Material and Methods: A search was conducted in Scopus, PubMed, and Web of Science (ISI) databases. Keywords related to leadership, safety performance, and healthcare employees were used. Studies published up to the end of 2024 were identified and reviewed in accordance with PRISMA guidelines.
Results: Nineteen relevant papers were selected and included in the study. During the review of studies, eleven leadership styles or approaches were identified in relation to safety performance in various healthcare facilities. These included transformational leadership, leader-member exchange leadership, leader safety priority communication and feedback, ethical leadership, empowering leadership, inconsistent and destructive leadership, transactional leadership, task-oriented leadership, authentic leadership, safety leadership, and servant leadership. All leadership styles except for inconsistent and destructive leadership had a direct or indirect positive effect on safety performance. Also, the largest number of studies (n=4) focused on transformational leadership style and leader-member exchange leadership.   
Conclusion: The selection of appropriate leadership styles can contribute to enhanced safety, a reduction in occupational incidents, and improving service quality in healthcare settings. The findings of this study highlight the importance of developing effective leadership styles and strengthening appropriate managerial approaches to improve safety in healthcare facilities. 

---

Introduction: Fumigant gases in maritime and container chains, along with occupational noise in marine and manufacturing industries, are among the most significant chronic risk factors. They are usually assessed separately, despite their simultaneous impact on workers’ health. The importance of this study lies in presenting an integrated approach for real-time monitoring of combined risk and aligning it with occupational exposure limits (OELs). The aim is to develop and validate an interpretable, regulation-oriented framework for predicting combined risk.
Material and Methods: This research integrated and normalized data from the Global Burden of Disease (GBD) 2021 study including age-standardized disability rates (ASDR) and average annual percentage change (AAPC) for 204 countries with occupational exposure limit tables for fumigants. A Sugeno-type fuzzy inference system with three inputs and four rules was designed. Weights and membership function boundaries were optimized using the Prairie Dog Optimization algorithm, and a threshold-based scenario generation module was applied to produce high-risk synthetic data. Model performance was evaluated through an OEL compliance test.
Results: Findings revealed that the proposed optimization reduced the loss function by 42% compared to random search. The mean absolute error (0.028 ± 0.006) and root mean square error (0.041) were obtained. Threshold-based scenario generation improved data coverage in high-risk regions from 0.62 to 0.90 and increased the accuracy of critical condition detection from 0.71 to 0.89. The OEL compliance index reached 0.93, confirming input weighting as the most influential factor.
Conclusion: The proposed framework simultaneously ensures numerical accuracy, interpretability, and regulatory compliance with occupational exposure limits. It can be deployed within real-time monitoring dashboards for ports and factories. Future research should integrate IoT sensors and multi-objective optimization to enable dynamic updates in response to evolving regulations and operational conditions.

---

Introduction: Commercial trucking is one of the most challenging occupations, with long work hours, short rest periods, and substantial psychological pressures that contribute to fatigue and deterioration at work. Since regular physical activity is one of the pillars of healthy life and can improve physical and mental functioning, the present study investigated the relationship between physical activity and driver performance with occupational fatigue as a possible mediator.
Material and Methods: The study population was intercity commercial truck drivers in several cities of Razavi Khorasan Province. Using Green’s formula, we calculated a sample size of 140 participants. Data were collected with the Swedish Occupational Fatigue Inventory, the Sharkey Physical Activity Questionnaire, and the Driver Performance Questionnaire (unsafe behaviors). Statistical analyses included Pearson correlation coefficients and multiple regression analyses.
Results: Our results showed a significant positive correlation between occupational fatigue and driver performance problems (P=0.001). Both the correlation between physical activity and work fatigue, and the correlation between physical activity and driver performance were significant negative correlations (P=0.001). In addition, the indirect link between physical activity and driver performance via occupational fatigue was also significantly negative (P=0.001).
Conclusion: Based on our research results, enhanced physical activity contributes to enhanced driver performance (decreased unsafe behaviors) of commercial truck operators, directly and indirectly through decreased occupational fatigue. This study provides scientific evidence for the development of safety policy in the transportation industry of Iran.

---

Introduction: Relief work is inherently associated with various stress-inducing factors due to the nature of the profession. Among relief-related professions, firefighters, due to the responsibilities related to firefighting and safety services, are exposed to various physical and chemical hazards. Therefore, the primary aim of this research was to compare the effect and practice retention, central and operational and skill-based stability over the balance of the firefighters with and without firefighting and rescue clothing and Hazardous Materials.
Material and Methods: The statistical population consisted of 5500 firefighters from the city of Tehran. As for the intervention, in the first group, central stability exercises, and in the second group, operational and skill-based exercises were performed by the firefighters during their shift days for a period of 6 weeks. The balance of the firefighters in both groups was measured at three stages: at the beginning of the intervention, immediately after the 6-week training period, and one month after the end of the training. The “Y Balance” board was used to assess the firefighters’ balance. Data analysis was performed using repeated measures analysis of variance and the Bonferroni post hoc test at a 5% significance level, using version 26 of the SPSS software.
Results: According to the results of this study, the balance of firefighters in both the right and left legs was significantly greater in the operational and skill-based training group compared to the central stability training group, both immediately after training and one month later (p < 0.05). With performing operational and skill-based training, right leg balance in the rescue suit was significantly higher than in the fire protection and hazmat suits (p < 0.05), while there was no significant difference between the fire protection and hazmat suits (p > 0.05). Left leg balance in the rescue suit was significantly higher than in both the fire protection and hazmat suits, and balance in the fire protection suit was significantly higher than in the hazmat suit (p < 0.05). Additionally, firefighters’ balance significantly improved after balance training (p < 0.05), and there was no significant difference between the balance measured one month after training and immediately after training (p > 0.05).
Conclusion: In addition to the fact that core stability exercises particularly task specific functional training are effective in improving balance and preventing injuries, the retention of these effects over time should be taken into account.

---

Introduction: Computer-based numerical simulation can serve as an effective approach for replicating system behavior over time. It enables the analysis of a system’s capabilities, capacities, and performance during the design phase—prior to physical implementation. Accordingly, simulation tools can be used for the design, modeling, evaluation, and visualization of heat transfer interactions among the components of a Liquid Cooling Garment (LCG) system. Therefore, the present study was conducted with the aim of designing and experimentally validating a numerical simulation model for a thermoelectric-based LCG.
Material and Methods: A new model of a liquid cooling garment (LCG) based on fluid circulation was developed using the Finite Element Method (FEM) in COMSOL Multiphysics software. To validate the simulated model, a physical prototype of the LCG with similar characteristics was designed, and human experiments were conducted under controlled environmental conditions. Finally, the findings obtained from the simulation and experimental results were compared.
Results: The results showed that the difference in microclimate temperature between the simulated predictions and the average experimental data ranged from 0.1 °C to 0.65 °C. Additionally, the deviation in coolant temperature within the piping system between the simulation and experimental data ranged from 0.1 to 0.6 °C. These findings indicate that the developed model demonstrates a satisfactory level of accuracy in predicting thermal parameters
Conclusion: The results suggest that the proposed model can serve as an effective tool in the design and evaluation process of wearable cooling systems before fabricating physical prototypes. Further studies are recommended to enhance the performance and precision of LCG simulation models.
 

---

Introduction: Surgical technologists encounter a challenging work environment, and therefore, they require well-organized workplaces and appropriate health-related training. This study aimed to determine the effect of a participatory ergonomics program on musculoskeletal disorders (MSDs) and general health among surgical technologists
Material and Methods: This single-blind randomized controlled trial was conducted in 2023-2024 in operating rooms of teaching hospitals in Isfahan, Iran. The study population comprised 88 surgical technologists meeting the inclusion criteria. One hospital was randomly selected as the intervention site, while the remaining hospitals served as the control group. Data were collected using a demographic questionnaire, the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ), and the 28-item General Health Questionnaire (GHQ-28). Initially, all participants in both groups completed baseline assessments. The intervention group received a participatory ergonomics program. Follow-up assessments were conducted at 3 and 6 months post-intervention in both groups. Data were analyzed using SPSS version 24 employing both descriptive and inferential statistical methods, with a significance level set at 0.05.
Results: Before the intervention, no significant differences were observed between the intervention and control groups in terms of mean scores for general health and MSDs (p=0.55). Three months post-intervention, a significant difference was found in the mean score of lower extremity MSDs between the groups (p=0.033). Six months post-intervention, a significant difference was observed in the mean score of Trunk region MSDs between the groups (p=0.038). Significant differences in mean general health scores were observed between the groups at 3 months (p=0.001) and 6 months (p=0.001) post-intervention, with the intervention group reporting better general health compared to the control group.
Conclusion: The implementation of a participatory ergonomics program can improve general health and reduce MSDs among surgical technologists.

---

Introduction: Workplace safety is a critical factor for organizational success and the protection of human capital. Safe behavior among employees is influenced by various psychological and organizational factors, including safety climate and safety motivation. Considering the importance of enhancing safety motivation and the lack of standardized indigenous tools in Iran, this study aimed to culturally adapt the Self-Determination Safety Motivation Scale (SDSM) and examine its mediating role in the relationship between safety climate and employees’ safe behavior at Kavir Steel Complex in Aran and Bidgol County.
Material and Methods: This analytical cross-sectional study was conducted in 2024 among 256 production line employees. Data were collected using the Safety Climate Questionnaire, the Safe Behavior Questionnaire, and the Persian-adapted SDSM. The adaptation process included forward–backward translation, content validity evaluation by experts, and confirmatory factor analysis. Data were analyzed using SPSS version 26 and structural equation modeling with SmartPLS version 4.
Results: The findings indicated that safety climate had a positive and significant effect on safe behavior (β = 0.608, p < 0.001), and safety motivation significantly mediated this relationship (β = 0.388, p < 0.001). It is noteworthy that the direct relationship between safety climate and safety motivation was significantly negative. The structural model explained approximately 42% of the variance in safety behavior (R² = 0.419), indicating satisfactory predictive power. Model fit indices (NFI = 0.91, SRMR = 0.06) demonstrated a satisfactory model fit. Convergent validity, discriminant validity, and construct reliability were all confirmed at acceptable levels.
Conclusion: The results highlight the importance of fostering a positive safety climate and strengthening employees’ intrinsic motivation in high-risk environments to reduce workplace accidents and promote organizational health. These findings can serve as a foundation for policy-making and training programs in the field of HSE.

---

Introduction: Environmental and health concerns regarding synthetic sound absorbers necessitate natural, sustainable alternatives. Agricultural waste like walnut shells is promising due to its inherent porosity. This study evaluates the acoustic properties of walnut shell composites, investigating the influence of key design parameters like thickness and chopping level on sound absorption performance. 
Material and Methods: Porous granular samples were fabricated from walnut shells at three chopping levels (minimally, moderately, finely) and four thicknesses (20, 40, 60, and 80 mm). The sound absorption coefficient was measured via the impedance tube method. Field Emission Scanning Electron Microscopy (FESEM) analyzed the material’s morphology, and results were validated with Slanted Slit (SS) and Non-uniform Pore Size Distribution (NUPSD) mathematical models.
Results: Both increased thickness and chopping level significantly enhanced sound absorption. For finely chopped samples, increasing thickness from 20 to 80 mm shifted the absorption peak from 2000 Hz to 630 Hz. At a constant 80 mm thickness, intensified chopping boosted the absorption coefficient at 630 Hz from 0.48 to 0.97. This improvement correlated directly with increased density, tortuosity, and airflow resistivity. Model predictions showed the best agreement for the most finely chopped samples.
Conclusion: Walnut shell waste, especially after intensive mechanical processing, is a highly effective and sustainable sound-absorbing material. The chopping process optimizes the acoustic structure by activating the material’s inherent micro-porosity, yielding excellent performance in the speech frequency range (500-2000 Hz). This material shows significant potential as a green alternative to synthetic absorbers for indoor noise control. 

---

Introduction: Industrial units, such as oil refineries, face significant hazards due to the release of toxic and flammable gases. Hydrogen sulfide (H₂S), due to its high toxicity and environmental impact, is among the most dangerous pollutants. This study aimed to model and assess the consequences of H₂S release in the Sulfur Recovery Unit (SRU) of Abadan Refinery using PHAST software to support safety planning and risk reduction strategies.
Material and Methods: Consequence modeling was conducted using PHAST version 8.4. Process data, including temperature, pressure, flow rate, and feed composition, along with meteorological conditions (average temperature, relative humidity, and wind speed based on Pasquill stability classification), were used to define probable scenarios. Scenarios included partial pipeline rupture, variable leak flow, short pipe release, and catastrophic reactor tank rupture. Key damage criteria, including thermal radiation threshold, explosion overpressure, and toxic dose, were used to determine hazard zones.
Results: Thermal radiation up to 71.027 kW/m² can cause instant death within a 70-meter radius, while overpressure exceeding 0.206 bar can destroy equipment and structures up to 35 meters in summer conditions. The H₂S cloud can spread up to 120 meters downwind, causing immediate fatalities among exposed personnel. These findings identify high-risk zones in and around the SRU, emphasizing the need to relocate shelters, install gas monitoring systems, and provide protective equipment. Results are limited to the defined scenarios and PHAST assumptions.
Conclusion: Due to the lack of risk assessment studies in early phases and during operation, identifying safe points and high-risk zones, along with prioritizing risk reduction, is essential to ensure workplace and public safety. Comprehensive risk assessment, including probability analysis (using software such as SAFETI) and application of advanced models (CFD and AI-based methods), is recommended for future research.