Journal of Health and Safety at Work

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Introduction: Assessing health, safety, and environment (HSE) performance based on up-to-date analytical models like resilience engineering, especially in automobile manufacturing companies, affected by the trilogy of HSE factors and functions, is of crucial importance. Therefore, this study was to review the factors effectively involved in HSE management performance assessment based on resilience engineering in automobile manufacturing industries.
Material and Methods: To collect and classify the data, many relevant articles and procedures published in journals or presented at seminars were researched and cited. In this study, reliable online databases, including Google Scholar, Web of Science, Scopus, and PubMed were searched to meet this purpose. Other databases in Farsi such as Magiran, CIVILICA, and Scientific Information Database (SID) were also employed. Accordingly, a total number of 211 articles were extracted and filtered in terms of content and topic by a team of four HSE senior experts, whereby irrelevant studies were deleted, the full text of each relevant article was more closely considered, and finally 18 studies were selected and thoroughly examined.
Results: The findings from these 18 articles revealed that the HSE would be influenced in various industries by factors such as organizational culture, learning and training, political-economic variables, workforce qualifications and skills, strategic and large-scale programs of organization plus its assets and financial resources. In automobile manufacturing industries as well, circumstances might emerge because of some extra-organizational threats and intra-organizational weaknesses, whereby the appearance of deficiencies in various processes and even the functions of the HSE as a whole would be impaired. Of the many external factors, one could mention economic sanctions, large-scale socioeconomic problems, and lack of materials and production equipment. The internal problems would also range from production reduction and cuts in budgets earmarked for different management departments to a rise in the number of accidents and diseases, soaring medical treatment costs, as well as growing expectations in employees, which together impact the HSE management performance.
Conclusion: Regarding the studies conducted on various models presented so far in the area of resilience, it was concluded that the HSE performance of organizations intended to prevent and control risk factors were by no means distinct from other management factors and strategic decision-making in an organization. Rather, the HSE indicators could be impacted by many extra- and intra-organizational factors. Based on the models surveyed, it would be essential to consider the concept of resilience in HSE management. The reason for this is that the idea of the HSE would appear to be an issue of less virtue and importance in various stages and situations in the lifecycle of an organization, which is not consistent with the HSE management system and does not keep pace with the influencing factors.

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Introduction: Determining methods for assessing heat stress in different work environments is one of the major challenges for researchers in this field. The purpose of this study was to validate WBGT index and heat pressure assessment (HPA) by some physiological responses in Iranian South Oil Company.
Material and Methods: This descriptive-analytical study was carried out on 154 employees of Kharg, Asalouyeh and Mahshahr oil terminals recruited from three different working conditions including indoor, outdoor and rest environments in the summer. The amount of heat stress in the workplace was evaluated by WBGT index HPA method. To meet this purpose, the environmental parameters i.e., temperature, wet temperature, radiation temperature, relative humidity, water vapor pressure and air flow rate were determined. In addition to the direct reading method by the WBGT meter, ISO 7243 was used to calculate the WBGT index. In order to validate the heat stress indicators, physiological parameters of oral temperature, tympanic temperature and work metabolism were measured.
Results: The results of paired sample t-test showed a significant difference between WBGT index and HPA in indoor and outdoor environment (P<0.05). Moreover, there was a significant difference between the physiological indices of oral and tympanic temperatures and work metabolism in the indoor and outdoor environment (P<0.05). Furthermore, the correlation test was significant between WBGT index as an independent variable and HPA as a dependent variable (P<0.05)  and showed a high correlation (R2=0.914) between WBGT index with oral temperature and tympanic temperature . Also, the rate of work metabolism was significantly related with the aforementioned parameters (P<0.05) and was equal to R2=0.423, R2=0.335, R2=0.552, respectively. The correlations were also significant between HPA with Oral temperature, tympanic temperature and work metabolism (P<0.05)and were equal to R2=0.632, R2=0.605, R2=0.557, respectively. The results showed also that the correlation rate between the HPA with physiological parameters is stronger than that between physiological parameters with the WBGT index.
Conclusion: This study showed that WBGT and HPA methods are useful for assessing the heat stress of Iranian South Oil Company. Also, the HPA method is more reliable for assessing heat stress in these regions.

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Introduction: Regarding the daily growth of Volatile Organic Compounds (VOCs) application in a vast variety of industries which also contributed to their adverse effects, different methods were used for controlling their emission. One of the most effective methods for this purpose, is a combination of cold plasma and catalyst or photo catalyst. In this study, the effectiveness of the HZSM-5/ Tio2 for Toluene treatment removal was investigated
Material and Methods: HZSM-5 zeolite, and Tio2 in 3 and 8 weight percent were used for photo catalyst preparation. The TiO2 particles were coated on the zeolite by impregnation method. X-Ray Diffraction, Scanning Electron Microscope and Brunauer Emmett Teller tests were used for the identification of photo catalyst structural properties. Toluene vapors with 58±2 PPM concentrations were produced in ambient condition including the room pressure and temperature by a dynamic system and introduced to a reactor included 1 gr of the photo catalyst. Vapors were passed from the reactor continuously with a rate of 0.5 liter per minute. Removal efficiency in three different states; plasma only, plasma /HZSM-5/TiO2 3%tw, and plasma/HZSM-5/TiO2 8% tw were assessed at the voltages of 4000 to 8000.
Results: In the current study, the removal efficiency of toluene vapors were 44.9, 75.36 and 66.68 percent for plasma, plasma /HZSM-5/TiO2 3%tw and plasma/HZSM-5/TiO2 8% tw, respectively. Photo catalyst with 3 weight percent showed the best removal efficiency. In all tests, the removal efficiency increased when the voltage increased and in 7000 volts it reached the maximum level. Therefore, adding photo catalyst to the plasma caused significant improvement in removal efficiency. Also, HZSM-5/TiO2 3% tw showed the best performance for toluene vapors removal.
Conclusion: According to the current study findings, using this combination in an industrial environment can be an effective way for Toluene vapors without the need for high temperatures. This combination can be proposed for other VOCs.

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Introduction: 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.
Material and Methods: 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.
Results: 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.
Conclusion: Lighting interventions can be used as a supplement to other strategies for increasing alertness and performance in the workplace.

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Introduction: Over recent years, various programs have been conducted to reduce noise, indicating the increasing concerns of society over noise pollution. This study has been performed to enhance the performance of parallel barriers on two sides of a highway considering the surrounding buildings.
Material and Methods: The 2D boundary element simulation method was employed to predict the noise reduction in barriers. Regarding the effect of buildings and water canals, various kinds of models were investigated to compare the effectiveness of different boundary barriers in real conditions from a listener’s perspective.
Results: The use of a single YA model could improve the performance of parallel barriers by 3.5 dB compared to that of a TS model. Moreover, by using a pair of barriers, no significant change was observed in the performance of the second barrier. However, by using parallel barriers along the surrounding buildings, the TD model improved the efficiency by 3 dB compared to the TS model. The rise in the frequency resulted in remarkable adverse effects on the barrier performance, such that the surrounding buildings at a distance of 8 m had a negative effect on the performance of the parallel barriers by almost 8.34 dB.
Conclusion: In general, by ignoring the buildings, the use of a pair of TZ barriers showed a higher performance. Meanwhile, by considering the buildings in the design model, the TD model was found to be optimum. Therefore, it can be concluded that choosing an ideal barrier only based on the noise behind it cannot indicate its behavioral and acoustic characteristics in a real environment.

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Introduction: Studies show that in many cases, environmental hazardous agents such as heat, noise, as well as chemical pollutants cause adverse health effects through the mechanism of oxidative stress. This study has examined the effect of exposure to noise and whole-body vibration (WBV) on some parameters of oxidative stress (enzyme superoxide dismutase (SOD), total antioxidant capacity (TAC), and malondialdehyde (MDA)) of workers in a foundry industry.
Material and Methods: The workers were selected based on the calculations related to the sample size and taking into account the inclusion criteria as well as completing the informed consent form. The level of exposure to noise and WBV was measured according to ISO 9612 and ISO 2631, respectively. For each worker, the time-weighted average was calculated. The level of exposure of workers to the studied stressors was divided into three categories: low, medium, and high. The blood samples were taken from all participants between 7-9 am. Then, via ELISA method according to the protocol of the kit manufacturer, the samples were prepared and analyzed. Univariate analysis of variance was performed to determine the “effect size” of each physical stressors on the studied parameters.
Results: The mean levels of MDA, SOD, and TAC among participants were 22.48 (11.19) nmol / ml, 61.28 (10.97) U / ml, and 1.64 (0.90) mM, respectively. Among the exposure variables, noise had the largest effect on MDA level (B = 0.090), which was not statistically significant (P = 0.865). WBV had the largest effect on SOD level (B = -1.469) which was statistically significant (P = 0.016). None of the studied variables had a significant effect on the TAC level; however, among the exposure variables, the greatest effect was related to WBV (B = -0.077; P = 0.133).
Conclusion: The effect of noise on oxidative stress parameters was not statistically significant. The effect of whole-body vibration on oxidative stress parameters except SOD was not statistically significant. Noise and WBV had increasing effect on MDA and decreasing one on SOD and TAC levels.

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Introduction: Strategic management involves determining the organization’s direction, preparing a strategic vision and mission statement, and providing the basis for growth, profitability, and production. It also includes the inclusion of employee safety and health programs throughout the organization. The existence of a strategic plan for the scientific and practical strengthening of occupational health and safety is one of the country’s academic and industrial priorities. The purpose of this study is to present a strategic plan for developing the specialized field of occupational health and safety engineering in Iran.
Material and Methods: The current study is a collaborative action research study that was conducted in 2021. The strategic planning committee consisted of 20 professors, experts, and doctoral students. Over the course of 14 weeks, they held regular weekly meetings, collected information from inside and outside the organization, analyzed the organization’s internal and external environment, and identified its strengths, weaknesses, opportunities, and threats. Based on this analysis, the committee determined the organization’s mission, perspective, values, and general and specific goals for 2021-2024. They also identified the necessary measures to achieve these goals and developed an operational plan to improve the performance of the specialized field of occupational health and safety.
Results: Conducting this applied research led to the strategy of internal and external analysis of the specialized OHS field, determining the direction of the basic strategy, mission, perspective, values, and general goals. Finally, seven specific goals and 286 actions were determined to improve the performance of OHS. The SWOT analysis of OHS’s internal and external environment identified 27 strengths, seven weaknesses, 26 opportunities, and 12 threats. According to the results of the SWOT matrix, the strategic position of the OHS field is to implement preventive strategies and maintain existing conditions.
Conclusion: This plan aligns with the 4-year OHS plan. In developing the program, attention has been paid to the documents and policies of upstream organizations. The strategic position of occupational health and safety engineering is a prudent strategy. In this situation, strategies for maintaining existing conditions can be applied. Therefore, it is suggested to reduce the weaknesses of OHS as much as possible and increase its strategic capabilities by focusing on prudent strategies. From the second year of implementing the strategic plan, the OHS field can gradually focus on developing activities.

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Introduction: Many industries have multiple factors harmful to health, leading to simultaneous exposure of these factors to each other. Noise is one of the most common physical parameters in the work environment. On the other hand, heat is also increasing due to various energy processes in industries. Therefore, this study was conducted with the aim of determining changes in physiological parameters and visual-auditory attention in acute exposure to heat and noise.
Material and Methods: In this experimental study, 72 individuals (36 men and 36 women) aged between 23 and 33 years participated according to the inclusion criteria. In total, 12 different test modes were performed (3 temperature levels and 4 noise pressure levels). The test was conducted for each person in 4 steps during a specific day. The duration of exposure to each condition was half an hour, and a half-hour rest was given between each test condition. Saliva samples of each subject were collected before and immediately after exposure to noise and heat. Also, The Integrated Visual and Auditory (IVA) was recorded by the participants simultaneously.
Results: The results of combined exposure to noise and heat on visual and auditory attention showed that only two modes of combined exposure, SPL95+WBGT34 and SPL95+WBGT29, caused a significant increase (P < 0.05) in mental workload and a significant decrease (P < 0.05) in visual and auditory attention. In addition, the results showed that independent exposure to noise at the levels of 85 and 95 dB and exposure to heat at higher temperature levels of 34 and 29 degrees Celsius cause a significant increase (P < 0.05) in salivary cortisol after exposure. The results of the effect of combined exposure to noise and heat on salivary cortisol showed that three experimental modes of combined exposure (SPL85+WBGT34, SPL95+WBGT29, and SPL95+WBGT34) caused a noticeable and significant (P<0.001) increase in salivary cortisol.
Conclusion: Indeed, salivary cortisol can be recommended as a physiological index to evaluate noise and heat exposure. It’s also noteworthy that salivary cortisol is more affected by noise and heat exposure than cognitive performance.

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Introduction: Despite the legal prohibition of asbestos fiber usage in the country, numerous studies have documented its presence in the air of various cities, including Tehran. This urban air pollution stems from the extensive use of asbestos in construction materials such as pipes, insulators in cooling and heating systems, and friction devices like brake pads and clutch plates, among other consumer products. Prolonged exposure to these fibers can have severe health consequences for residents, leading to respiratory issues, pulmonary fibrosis, and cancers such as mesothelioma. Consequently, we conducted a descriptive cross-sectional study to examine both the extent and nature of asbestos fiber distribution in Tehran’s air.
Material and Methods: This study measured the concentration of asbestos fibers in Tehran’s air over a 12-month period. Monthly samplings were conducted at eleven Tehran Air Quality Control Company-operated stations. The sample collection, preparation, and analysis adhered to the NIOSH 7400 method. Microscopic examination results were then translated into asbestos fiber concentrations using the appropriate formulas.
Results: Analysis of samples taken across four seasons revealed that spring recorded the highest average asbestos fiber concentration at 0.00134 f/ml, while the lowest concentration was observed in summer at 0.117 f/ml.
Conclusion: Given the widespread ban on asbestos use in many countries, including Iran, its presence in urban air is unexpected. Regrettably, flawed policy decisions made during the import ban announcement and the extended timeframe set for the ban’s initiation allowed companies to import and stockpile asbestos indiscriminately for future use.

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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: 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: Lung cancer is the second most common cancer in the world. Smoking occupational and environmental exposures are the most important causes of lung cancer. Cadmium is known as a human carcinogen due to its ability to increase lung cancer risk. This study estimates the general results of all studies on the relationship between cadmium and lung cancer.
Material and Methods: In the present study, studies that evaluated the relationship between cadmium and lung cancer until May 2022 were searched and retrieved. From the funnel plot to determine the existence of diffusion skew, from the statistical tests Chi-squared test (x2) and I2 to determine heterogeneity, from the meta-regression method to identify the root of heterogeneity, and from the sensitivity analysis approach to identify the effect of each study on the result, it was generally used. This study performed all analyses with Stata statistical software version 15.
Results: In this study, it was observed that the chance of developing lung cancer compared to the base group, in the people exposed to a higher dose than the base level of cadmium is equal to 1.31 (95% CI: 1.06-1.62; p-value = 0.024), which is statistically significant. Based on Egger’s test (p-value = 0.178) and Begg’s (p-value = 0.276), no diffusion bias was observed in this study.
Conclusion: ccording to the final results of this review research, exposure to cadmium leads to a 31% increase in lung cancer risk, which is statistically significant. Therefore, cadmium is a risk factor for lung cancer.

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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: Risk assessment matrix is a tool used in a project’s risk assessment process to identify the probability of risks and evaluate the potential damages caused by those risks. Generally, a risk assessment matrix is drawn in a two-dimensional form, with two factors: the severity of the accident and the probability of its occurrence. So, the purpose of this study is to develop a specific risk assessment matrix in a three-dimensional form by using the accident severity grade (ASG) rating system, the accident probability, and taking into account the preventive approach that helps occupational injury risk assessment in the automobile industry.
Material and Methods: This cross-sectional study was conducted in 1402 (2023) in one of the automobile assembly industries. One hundred cases were randomly selected by examining the reports of this industry’s past accidents. The ASG scoring checklist was designed and completed by the experts to assess the severity of accidents. Then, considering the ASG score, the frequency of the accident, and its preventability, a three-dimensional risk assessment matrix specific to this industry was presented.
Results: According to the findings of the accident analysis, a total of 658 accidents and 15,019 lost working days were recorded in this period. The most influential factor in the occurrence of accidents is related to “surface condition” (influence factor = 0.6), and the least of them belongs to the “weather conditions” (influence factor = 0.028). The results of the three-dimensional matrix show that when the ability to prevent accidents increases, the risk of accidents decreases.
Conclusion: Using the accident severity grade (ASG) and preventability in the proposed three-dimensional risk assessment matrix, the accident severity can be quantified immediately after the accident. This approach allows monitoring workplaces during the accident, leading to timely control and risk management implementation.
 

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Introduction: In recent years, exposure to nanomaterials has been known as a challenge among occupational health experts. In this line, personal protective equipment has been considered as a solution to reduce the worker’s exposure. Since respiratory and skin tracts represent the most common workplace exposure routes, knowledge of the efficiency of respiratory and skin protection equipment is particularly important. So, the aim of this study is the assessment of the efficiency of respiratory and skin protection equipment toward controlling nanoparticles in the workplace with a scoping review approach.
Material and Methods: This study was conducted in 2022 with a scoping review approach. Arksey and O’Malley’s five-step framework was chosen as the research method. The search strategy was followed in the databases necessary to access the research data, including PubMed, Google Scholar, Science Direct, Web of Science, and Scopus. Also, EndNote X9® and Microsoft Excel software were used to collect and analyze studies, respectively.
Results: In the first step, 1014 articles were identified. Finally, 38 articles were included in the study to examine quantitative and qualitative information about the efficiency of respiratory and skin protective equipment. Twenty-five articles were related to breathing masks, and six studies were about protective gloves, and seven other articles were devoted to protective clothing. According to the studies of breathing masks, the mean total penetration of nanoparticles was estimated at 2.27%. Also, based on the studies of protective clothing, the maximum penetration of nanoparticles was 30nm for protective clothing made of polypropylene and polyethylene with different layers.
Conclusion: Although the efficiency of existing personal protective equipment showed a good result for controlling nanoparticles, the size of nanoparticles is one of the essential parameters in determining the efficiency of the equipment, which should be considered the workplaces. So, it is recommended that more studies be considered to improve their efficiency, and standard tests should be developed to evaluate them.

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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. 

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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.
 

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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.