Journal of Health and Safety at Work

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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: Micro-perforated absorbents are one of the structures that are widely used nowadays. The sound absorption mechanism is performed by viscous energy losses in the cavities on the plate. In this study, the acoustic properties of non-flat perforated panels in oblique angle was investigated in numerical method.
Material and Methods: This paper examined the effect of the surface shape on the micro perforated absorber performance at low frequencies (less than 500 Hz). The three-dimensional finite element method was used to predict the absorption coefficient of this group of adsorbents. Also, the results obtained from the shaped absorbents were compared with the flat micro perforated ones. After validating the numerical results, six different designs were defined as the surface shape of the micro perforated plates in the COMSOL Multiphasic, Ver. 5.3a software
Results:  The results reflected the fact that the factor of the surface shape can be used as a contributing factor in lower frequencies. In general, the dented or concave shapes provide better outcomes than other flat designs and shapes and the convex or outward shapes bring the weakest results.
Conclusion: To explain this function, shaping creates a phase difference and angling the sound wave and creates a variable depth behind the micro-perforated plate. It also influences the reflection process which affect the absorption coefficient.

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Introduction: The study of noise has always been of interest to occupational health professionals as a harmful physical factor in the workplace. However, the psychological and psychoacoustic aspects of noise in the workplace have been less studied. This study has dealt with different colors of noise and their applications in psychoacoustics.
Material and Methods: This review study was conducted by searching the databases of Google Scholar, ProQuest, Science Direct, PubMed, and Scopus to extract the articles related to the research subject within a 50-year interval from 1970 to 2020.
Results: Based on the results of the present study, colored noises and white noise seem to have the potential to be used as acoustic stimuli to improve the sleep of employees, especially shift workers, to improve memory and attention, especially in jobs that require high care and attention. Colored noise and white noise have potential applications to improve cognitive function in different occupations to reduce the activity of the sympathetic nervous system and anxiety and stress, especially in jobs with high job stress. Also, these noises are helpful for people’s privacy, especially in the open workplace, for noise masking and noise control purposes, as well as for medicine and treatment of disorders such as tinnitus, ADHD, and hyperacusis.
Conclusion: Paying attention to the colors of noise and their psychoacoustic impacts shows us that the noise impacts are not limited to their undesirable and damaging effects. Instead, their positive and applied aspects should also note. Familiarity with such aspects and their introduction can identify the existing information gaps in this field and pave the way to fill them.

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Introduction: Universities play a key role in creating a knowledge-based society and its sustainable development. Strategic planning by strategically analyses internal and external environments of the organization, forecast its future, identifying its strategic direction, and strengthening organizational structures, processes, and outcomes, creates and sustains competitive advantages. This study aimed to formulate a strategic plan for the Occupational Health Engineering (OHE) department of School of Public Health (SPH) at Tehran University of Medical Sciences (TUMS).
Material and Methods: In this participatory action research, a strategic planning committee was formed. The strategic planning committee used the strength, weakness, opportunity and threat (SWOT) matrix to evaluate the internal and external environments of the OHE department. Then, the mission, vision, values, goals and objectives of the OHE department were defined. Finally, the operational plan including actions to achieve the goals and objectives were formulated.
Results: Experienced professors and staff, specialized laboratories, professional journals, and high ranked postgraduate students were the most important strengths; and theoretical and non-practical courses, lack of educational protocols, poor communication with industries, lack of resources, and low motivation of employees were some of the weaknesses of the OHE department.  The support of senior managers of TUMS, industry liaison council at school and university, facilities of the university faculties, comprehensive research laboratories of the university, capacities of the private sector and increasing the demand for research in the industry were the opportunities. High inflation, political sanctions, the absence of consulting engineering companies and the uncertainty of research priorities of industries were important threats to the OHE department. Therefore, the OHE department is in a conservative strategic position. The strategic direction of the department, including the mission, vision, values and goals, until 2025 was determined. Improving the structures, working processes and performance of the occupational health department were determined as objectives and 81 actions were formulated to achieve these objectives.
Conclusion: The educational departments, schools and universities must have a strategic plan for progress. The strategic plan of the occupational health department of TUMS was formulated in line with the four-year plan of the university and coordinated with the operational plans of the educational, health and research deputies of TUMS and school of public Health. Proper implementation of this comprehensive and evidence-based strategic plan will improve the performance of the occupational health department.

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Introduction: This study aims to determine the amount of hand-arm vibration transmitted from heavy electric destruction tools and the effect of using chisel with different lengths and shapes when demolishing concrete surfaces.
Material and Methods: To evaluate the magnitude of hand-arm vibration on the left and right handles of two powerful electric demolition hammers commonly applied in Iranian construction work and urban services, 323 measurements were made (RONIX and NEC). The demolition procedure was carried out by two experienced users on 49 concrete slabs of the same grade (20 C) with thicknesses of 10 and 15 cm while utilizing standard tools, such as hammers with two different chisel head shapes (flat and point) and lengths (40 and 60 cm). Utilizing two SVANTEK vibration meters concurrently on each hammer handle, measurement and evaluation were according to the ISO 5349:1, 2 procedures.
Results: The mean effective (frequency weighted root mean square) acceleration (awrms) for the Vector Sum Values (VSV) in the hammer handles were 15.71 m/s². The primary vibrational axis transmitted to the handle of tool was the vertical axis, at 13.60 m/s². When employing flat and point chisel, the mean awrms were 16.59 m/s² and 14.82 m/s², respectively. The difference between the results of 60 and 40 chisel was a little more than 2m/s2. The dominant and harmonic frequencies of the tools were generally in the range of 25 Hz to 80 Hz and 200 Hz to 400 Hz
Conclusion: The mean results generally indicated that point chisel with shorter lengths (40 cm) accelerates at a lower rate than flat chisel with longer lengths (60 cm). In the frequency range below 40 Hz, the RONIX hammer produced a larger acceleration than the NEC hammer indicating that the NEC hammer had a higher safety competitive advantage compared to the another hammer.

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Introduction: Climate change and hot processes in the workplaces has led to an increase in the effects of heat stress on employed people, which has become a major concern, especially in tropical and subtropical countries. Early detection of biomarkers in induction of heat stress-related DNA damage can be used in the identification and evaluation of health and safety, including occupational health professionals, as well as to prevent serious diseases caused by heat stress in various occupations with the nature of hot processes or to help different warm seasons of the year. Therefore, this review study was conducted to identify diagnostic biomarkers heat stress induced- DNA damage in occupational exposure.
Material and Methods: Databases such as PubMed, Scopus, Google Scholar, and Web of Science were systematically searched to meet the study’s goals. Moreover, references to relevant publications were examined. Finally, suitable articles were selected and analyzed using the inclusion (studies on different occupations, different biomarkers in hot work environments, all articles published without time limit until the end of April 2022 , and English and Persian language)  and exclusion criteria.
Results: The results of search in databases showed that 9234 articles were found in the initial search. After removing duplicate and unrelated articles, 2209 eligible articles were selected. Based on abstract full-text screening, 7166 studies were excluded, and based on abstract full-text screening, 21 studies were not accessible. Finally, seven articles were selected to be reviewed. The evidence showed that diagnostic biomarkers included the measurement of 8-hydroxy-2-deoxyguanosine (8-OHdG), micronuclei semen quality, heat shock proteins (HSP70), and leukocytes were extracted to heat stress induced- DNA damage in occupational exposure.
Conclusion: Based on a review of studies,  biomarkers identified are suitable for heat stress induced- DNA damage as a result of occupational exposure to extremely high heat climate conditions. Understanding and identifying appropriate biomarkers in inducing DNA damage can help health and safety professionals determine the amount and magnitude of heat stress responses in occupational exposure to different temperatures and take appropriate measures and interventions to control and reduce the hazard effects of thermal stress. This study can also be considered as a preliminary study for research in the future.

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Introduction: Natural materials are more efficient and attractive than synthetic materials. In this study, the sound absorption behavior by natural kenaf composite and Micro-Perforated Panel (MPP) at low and medium frequency region was investigated.
Material and Methods: Initially, the results of kenaf fibers with a thickness of 10 mm were validated by the Finite Element Method (FEM) based on COMSOL Multiphysics 5.3a. The studied combined panel is consisting kenaf fibers with micro-perforated plates and an air layer. This study examined the varying arrangement of the behind layers of the MPP, the different thickness of the layers, and the structural parameters of MPP. The structure with the best absorption coefficient was chosen for the following stage and was considered constant at each stage.
Results: The arrangement of composite layers indicated a strong direct effect on the sound absorption performance; as we discovered that kenaf fibers behind MPP led to better performance in frequencies below 2500 Hz. In addition to the chamber depth behind the MPP, the material and macroscopic properties of the layers, at the same depth, are also important determinants of the exact point of the resonant frequency. Furthermore, configurations in which air layer depth is more than the absorption layer, with the same diameter (hole) and depth (chamber), maximum resonant absorption peak is achieved.
Conclusion: Low-frequency sounds can be successfully dissipated by combining MP plates with kenaf fibers as reinforcing absorber in combined panel. In general, choosing the optimum structural parameters (Composite panel according to structure A with 0.5 mm hole diameter and 2% perforation percentage) allows a significant absorption at a specific frequency range. In this context, the use of numerical estimation to assess the sound absorption behavior can be meticulously substituted the difficult methods and laboratory costs.

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Introduction: Wood-Wool Cement Panels (WWCPs) are environmentally friendly sound absorbers also used as heat, energy, and moisture insulators. WWCPs have suitable mechanical properties due to using Portland cement and wood strands as raw materials. In this study, the acoustic performance of WWCP absorbents will be investigated.
Material and Methods: The mixed raw materials were molded under pressure through a hydraulic press to fabricate the WWCP samples. Samples were demolded after 24 hours. Samples were created with two thicknesses of 2 and 4 cm and three bulk densities of 400, 500, and 600 kg/m3 to examine the impact of thickness and bulk density on the acoustic absorption coefficient. The sound absorption coefficients were determined as a function of frequency for two frequency ranges: low (63-500 Hz) and high (630-6300 Hz).
Results: In the low-frequency range, increasing the thickness from 2 to 4 cm increased the absorption coefficient at 500 Hz by 0.16 and 0.23 for densities of 400 and 500 kg/m3, respectively. Increasing the thickness added an absorption peak and increased the value of these absorption peaks to 0.9 in the high-frequency range. When the bulk density of the 4-cm-thick samples increased from 400 to 600 kg/m3, the low-frequency absorption peak increased by 0.33. In the high-frequency range, the same density change increased the absorption peak by 0.26 for the 2-cm-thick sample.
Conclusion: Increasing the thickness of WWCP improves both its high- and low-frequency acoustic absorption coefficients. In addition, increasing the bulk density to approximately 500 kg/m3 boosts the sound absorption efficiency in both frequency ranges.

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Introduction: Colored noises with acoustic and psychoacoustic characteristics have several biological effects on human or animal health. While studies on auditory effects focus on noise’s physical aspects, its psychoacoustic aspects can also result in health and safety risks. Therefore, this study aims to investigate frequency-based damages due to exposure to colored noise in an animal model.
Material and Methods: Twenty-four male Wistar rats were randomly divided into four groups (6 in each group). The groups included the control (no exposure) and three exposure groups (white, pink, and violet). The rats were exposed to 110 dB SPL for 4 hr/day for 14 consecutive days. Auditory brainstem responses (ABR) with click and tone-burst stimuli were recorded one day before (baseline), 7, and 14 days after exposure. Statistical analyses were conducted using ANOVA and repeated measures ANOVA.
Results: There was a statistically significant increase in ABR threshold values in exposure groups (p<0.05). Hearing threshold shifts in the white noise group showed a homogeneous pattern, violet noise showed an increasing pattern, and pink noise showed a decreasing pattern in low frequencies and a homogeneous pattern with increasing frequency. The highest shift in hearing threshold was observed in exposure groups from day 0 to 14. Additionally, the shift in hearing threshold in the second week was less than in the first one.
Conclusion: The current study observed that noise’s power spectral density affected hair cells’ damage severity. Accordingly, pink noise causes less damage to the cochlea compared to white and violet. Over time after noise exposure, cochlear pathogenesis gradually decreases and hair cell lesions become stable.

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Introduction: The aim of this study was to investigate the effect of particle size (mesh) on the sound absorption coefficient of the absorbers made from Arundo Donax reed and to determine the optimal mesh for sound absorption.
Material and Methods: After crushing the reed stems in 10, 30, 20, 16, and 40 mesh sizes, they were washed with 5% NaOH. To make the samples 3 and 10 cm in diameter, 10% PVA was used as a binder, and the impedance of the two-channel tube was used according to ISO 10534-2 standard to determine the absorption coefficient. 22 samples of meshes 16 and 20 were made to achieve the optimal mesh based on the optimized RSM method, and the SAA index was used to compare the samples and determine the optimal mesh.
Results: The highest absorption peak was related to meshes 16 and 20 at the frequency of 2500 Hz, which is 0.94 and 0.98 ,respectively. The effect of increasing the thickness and density on the absorption coefficient is evident. The results have shown the effect of increasing the thickness and density on the absorption coefficient in mesh 20 in such a way that by increasing the density from 150 to 250 and the thickness from 10 to 30 mm, the absorption coefficient has increased from 35 to 63.5%. The optimal sample was mesh 20 with a thickness of 30 and a density of 250 kg/m3, which had the highest average absorption (SAA=0.57). The greater distance between the real and imaginary parts of the impedance shows the reactivity of the sample. In mesh 16 this distance is greater, as a result, mesh 16 has more reactivity and correspondingly less absorption.
Conclusion: The role of particle mesh as one of the important and influencing parameters on absorption coefficient has been investigated in this study.

 

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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: To ensure employee safety and health, it is crucial to choose and use personal protective equipment correctly. An investigation of the respiratory and hearing protection equipment used in the industries of Tehran was conducted in the present study.
Material and Methods: This study was a descriptive-analytical study conducted in 2023 on 400 occupational health and safety experts in Tehran province. A researcher-made checklist and questionnaire (physical and online versions) were used to determine the criteria that are considered when selecting protective equipment. Statistical analysis and graphing were performed using SPSS-v21 and Excel-2016.
Results: Participants had an average age of 38.66 and an average work experience of 11.78 years. The participants reported 48.3% and 47.7% disapproval of the quality and 42.5% and 39.5% disapproval respectively of the quantity of respiratory and hearing protection equipment available in their industrial units. In addition, 56.3% of them admitted that they have no responsibility for providing or approving the equipment in their workplace. Overall, 27 and 29 criteria were mentioned by study participants pertaining to respiratory and hearing protection equipment, respectively. In the identified criteria, the frequency distribution ranged from 0.3% to 38%.
Conclusion: A high rate of expert dissatisfaction with protective equipment and a low frequency of most of the criteria mentioned indicates that industries aren’t paying much attention to the issue of choosing the right respiratory and hearing protection equipment. To improve the situation, more investigation is needed and practical and operational solutions will be provided. This study highlights the importance of proper selection and use of personal protective equipment in ensuring the safety and health of employees.

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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: 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: This study aimed to analyze the effects of endurance training (Aerobic) on the levels of inflammatory markers (IL-6/TNF-α) and some metabolic parameters in male rats with non-alcoholic fatty liver disease to investigate the feasibility of using exercise training to reduce inflammation.
Material and Methods: A total of 44 Wistar rats were randomly assigned into two groups: (I) standard diet group of 22 rats and (II) high-fat diet group with 22 rats supplemented with free access to fructose water. After 17 weeks, two rats from each group were sacrificed, and liver tissue was collected for hematoxylin-eosin staining. Subsequently, the remaining 20 rats in the (I) group were divided into a training group (T) and a control group (C). The 20 rats in the (II) group supplemented with fructose water were divided into a fatty liver group (FL) and a fatty liver + training group (FL+T), each comprising ten rats. In the next phase, the T-groups underwent an eight-week endurance training intervention. Then, IL-6, TNF-α, glucose, insulin, insulin resistance and sensitivity levels were measured.
Results: The results of the present study showed that as a result of a high-fat diet with liquid fructose in HFD+HF group rats, non-alcoholic fatty liver disease (NAFLD) with complications such as a significant increase in the levels of IL-6 and TNF-α, Hepatic dysfunction, and metabolic parameters were disturbed (p<0.001). However, endurance training improved most of these complications by reversing the disease process (p<0.001).
Conclusion: According to the results of the present study, it can be concluded that the improvement of inflammatory markers, liver dysfunction, and metabolic parameters through endurance training is one of the key mechanisms of exercise in the treatment of NAFLD, the consequences of which may show the importance of endurance training in treatment of NAFLD highlights.