محمدرضا منظم

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.

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.

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.

The role of particle mesh as one of the important and influencing parameters on absorption coefficient has been investigated in this study.

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.

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.

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.

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.

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.

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.

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

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.

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.

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

  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.

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.

Working cloth is one of the most important personal protective equipment for workers and the military, and its proper selection for hot and dry areas plays an important role in heat exchange and balance between the human body and the environment. Therefore, this study was conducted to evaluate the heat transfer and comfort of fabrics and the optimal selection of fabrics for military personnel and workers in hot and dry areas.

This experimental study was carried out on 16 types of common fabrics of military personnel and workers in hot and dry areas. This fabric has a combination of 4 texture patterns and 4 types of percentage of a combination of cotton and polyester. The fabrics were evaluated in terms of air permeability and water vapor permeability, water absorption, equivalent pore radius, thermal conductivity, tear resistance, and bending stiffness of the machine. Finally, the optimal fabric was selected by combining multivariate decision-making and hierarchical analysis (AHP-TOPSIS) and compared with other fabrics using SPSS 16 software.

The results of AHP-TOPSIS showed that the fabric with a combined share of 65% cotton and 35% polyester with a texture of 1/2 shows the optimal behavior in terms of comfort characteristics and heat transfer of the fabric. In a texture of 1/2, the average amount of water absorption, bending stiffness and thermal conductivity in 35% polyester and 65% cotton fabrics are not significantly different from 100% cotton fabrics (P>0.05). Also, the average amount of air and water vapor permeability and tear resistance in 35% polyester and 65% cotton fabrics are not significantly different from 65% polyester and 35% cotton fabrics (P>0.05).  

The results of this study showed that the most optimal fabric for military personnel and workers in hot and dry areas has a composition of 65% cotton and 35% polyester and also has a texture of 1/2.

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.

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.

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.

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.

The noise could affect some aspects of human health, including the cognitive performance. In addition to sound pressure level and exposure time, the psychoacoustic features of noise may cause destructive effects on humans. A few recent studies have been conducted on effect of sound quality on cognitive performance. This study aims to find the noise loudness and sharpness levels as the most destructive effects on human cognitive performance.

This was a cross-sectional study on 10 male students of Tehran University of Medical Sciences. The Noises were generated in two channels that the left channel produced the pink noise as a background noise. The pink noise loudness and sharpness were 19.7 sone and 2.49 acum, respectively. The right channel generated noises with different loudness and sharpness levels the noise loudness ranged from 8.87 to 67.9 sone and the noise sharpness ranged from 1.07 to 6.4 acum. Finally, ten noises with different loudness and sharpness were applied. The students were exposed to ten different types of noise and a silent condition. The Mathematical Problem Solving Task (MPST) test was performed to assess cognitive performance. The reaction time and the accuracy rate were measured after 5 minutes of noise exposure. Data were analyzed by SPSS (ver. 22). P< 0.05 was considered as significant level.

The mean reaction time and the mean accuracy rate increased with the sharpness level.  However, alteration in the loudness and sharpness levels had no significant effect on the speed and accuracy of students. Performance speed increased in noise 3 with the highest loudness (L=67.9, SH=1.07) in comparison with the silent condition (p-value=0.05). The mean accuracy rate in exposure to the noise 9 reduced in comparison with silence (p-value=0.04)

Different levels of psychoacoustic features had no significant effect on the cognitive performance parameters. Although, the accuracy rate and the reaction time decreased in noises 9, the sharpest noise, and 3, the loudest noise, in comparison to the silence, respectively.

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

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

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

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

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

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

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

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

Reducing noise pollution has become an essential issue due to the increase in public concern and also social demands for a better lifestyle. Using sound absorption materials is a preferred method to reduce the noise pollution. Undesirable properties of pure polyurethane such as poor absorption of mechanical energy in narrow frequency ranges can be improved by providing polymeric nanocomposites.  The main purpose of this study is to synthesize the polyurethane nanocomposite foams in order to improve its acoustic properties.

At the first steage, pure polyurethane foam was synthesized using the pre-polymer method. Afterwards, nanocomposite foams were synthesized with different mass fractions of Nano silica. The cellular morphology of prepared nanocomposite foams was investigated by scanning electron microscopy (SEM (.Utilizing a  two-microphone impedance tube,  sound absorption coefficient (α) was calculated in the frequency ranges of 100 Hz to 1600 Hz in order to investigate the acoustic properties of the new absorbant.

According to the microscopic investigations, morphology of the cells changed after adding silica nanoparticles. Also, the cell sizes were observed to be decreased by increasing the amount of silica nanoparticles. Furthermore, the acoustic analysis of nanocomposite foams indicated that the sound absorption increased by enhancing the load of silica nanoparticles.

In the current study, the effect of silica nanoparticles additive amount on acoustic properties of the polyurethane-based nanocomposite was investigated. Our findings depicted that the polyurethane-based nanocomposites were able to promote the sound absorption coefficient.

Perforated panels are one of the most common resonant absorbers for sound control. In this study the acoustic properties of non-flat perforated panels in oblique angle and field diffusion were investigated in both numerical and laboratory methods at 1.3 octave frequencies.

3 non-flat shapes were considered for perforated panel and their absorption performance was compared with the usual shape of (flat) perforated panel. After determining the best shape in terms of absorption coefficient, it was constructed according to the standard  ISO 354at the approved dimensions and the desired structural properties and was subjected to absorption coefficient test in the reverberation chamber

Numerical simulation results showed that the shapes defined in this paper all improve the absorption coefficient at the mid and high frequencies and also the shape C has higher absorption coefficient at the lower frequencies than the flat and two defined shapes. The results of measurement of absorption coefficient showed that the highest absorption coefficient of 0.77 is observed at the frequency of 160 Hz. Also, to compare the results, these conditions were implemented in numerical environment and the absorption coefficient was calculated according to the existing relationships.

Surface shape is effective in improving the absorption performance of these adsorbents and comparison of the numerical and laboratory results showed that acceptable agreement for these two methods is found in most of the frequency spectrum and the numerical method is able to predict this quantity with good accuracy.

Due to the high number of small workshops in the country, the numerous workforce of them from one hand, the existing noise as one of the harmful factors in the working environment and the importance of workers’ health from the other hand, this study was conducted with the aim of identifying the effect of training intervention of hearing protection devices use based on BASNEF model on the workers of Hamadan small workshops.

This study was performed in two groups of 45 workers. Data were collected through BASNEF questionnaire before and after 3 months of training intervention. Experimental group received three sessions of training intervention (theoretical and practical), while the control group received no trainings. The data were analyzed by SPSS software version 17.

The results showed that the mean score of all BASNEF model’s areas were increased significantly after training intervention relative to the former. In addition, the findings indicated that among all areas of BASNEF model, the highest score was related to behavioral intention, whereas the lowest was related to the performance.

The BASNEF training intervention had an important role in increasing the awareness and attitude of people and also their behavior and performance in relation to the usage of hearing protection devices. This lead to the increased duration of earmuff’s usage and decreased hearing threshold variation of workers who were exposed to excessive noise.

Nearly a third of people work in jobs that use voice to be part of their work. Teachers as the largest group of professional vocal users, are at risk of vocal disorders. The aim of this study was to investigate the effect of different risk factors on vocal disorders in teachers.  

This is a cross-sectional and descriptive-analytic study that was conducted on 73 primary and secondary male and female school teachers in Saveh in 2017 by random sampling. The researcher-made questionnaire on risk factors affecting verbal disorders with the aim of identifying risk factors and a Voice Handicap Index (VHI) questionnaire (30 items) aimed at evaluating verbal disorders and symptom questionnaire were used in this study. All of them have been shown to be valid and reliable in previous studies. Data were analyzed using t-test and chi square statistical tests by SPSS ver.24.

The reliability of the researcher-made questionnaire on the risk factors affecting vocal disorders was confirmed by Cronbach’s alpha (0.736) and its validity was confirmed by the experts regarding the adequacy of the number of questions, the lack of ambiguity and the assessment of content fitness. According to our gathered data, vocal disorders were observed in 55% of the teachers. Also the results showed the rate of vocal disorders in female teachers is far higher than male teachers. Functional disturbance of vocal cords and allergy as general risk factors, teaching tools and poor air quality as environmental risk factors and inadequate vocal rest and job stress as occupational risk factors contributed to increasing vocal disorders in teachers. Among the symptom associated with verbal disorders in teachers, vocal fatigue and hoarseness were more common in comparison with other symptoms.

Due to the prevalence of vocal disorders in half of the teachers and the impact of general, environmental and occupational risk factors, it is necessary to identify and control the risk factors of vocal disorders in teachers. It can also be concluded that teachers can enjoy a healthy voice by considering the principles of ergonomics and occupational health.

Outdoor workers are vulnerable to heat stress and climate change due to their occupational and environmental conditions. Short-term exposure to extreme heat (acute exposure) can lead to rise the core body temperature, which it may directly cause heat related illnesses such as mild rash, cramps, heat exhaustion and heat stroke. It is reported that long-term chronic exposure to heat leads to chronic kidney diseases, cardiovascular diseases, and mental health problems.
 The vulnerability consists of three components including sensitivity, exposure, and adaptability. According to the third assessment report of the intergovernmental panel on climate change (IPCC), the defiition of vulnerability is the degree to which a system or an individual is sensitive to, or unable to adapt to the adverse effects of Heat Stress and Climate Changes. Sensitivity is the physical capacity of workers to be affected by a hazardous agent like the heat. Sensitive is an intrinsic and internal factor that indicates how the person is vulnerable to heat stress. Individual risk factors in heat stress may decrease the individual’s tolerance to heat stress. The ability of system to cope with climate changes and adapt to extreme heat to reduce the risks and consequences resulted from these conditions is called adaptive capacity. Adaptation leads to reducing the vulnerability and increasing heat tolerance. Adaptive capacity is definedas“Theabilityof asystemtoadjusttoclimatechange, to moderate potential damages, to take advantage of opportunities, or to cope with the consequences”.
Therefore, it should be necessary to reduce the level of vulnerability through providing the control programs and strategies. Since there are no national laws, regulations, guidelines to protect outdoor workers against heat stress in the country, only the relevant policy in this area is the permissible occupational exposure limit. Therefore, the present study aimed to develop a comprehensive operational program to reduce the vulnerability of outdoor workers to heat stress and climate change. The results of this study can be very effective in decision making of the macro-management as well as planning of control measures in the country. Also, the program presented in this study can be helpful for organizations in charge of health and safety such as the Ministry of Health and Medical Education and the Ministry of Cooperatives, Labor and Social Welfare (which are responsible for maintaining, protecting and promoting the health of the workforce).

According to the objective of the study, which was the development and implementation of an operational plan to reduce the vulnerability of outdoor workers to stress and climate change, several technical panels and brainstorming sessions were held   with the cooperation of the Institute for Environmental Research, Tehran University of Medical Sciences by eminent experts in the fields of industrial hygiene, environment engaging in  Medical Sciences University, Department of Environment and Ministry of Health and Medical Education during the 2014-2016.  The main components of the vulnerability, the areas and strategies for application of an operational program to reduce the effects of exposure to heat stress and climate changes in outdoor workplaces were taking into account in the meetings. Also, the Delphi technique (due to the lack of access to some of the professors and executives directors), the study of text books and articles have also been used in this study.
Delphi, as an effective and highly flexible technique, is used to achieve consensus or forecast future events. It is a proper method to collect the opinions of experts, who cannot easily meet each other due to geographical distance. Using Delphi as a research method is useful when there is no integrated knowledge about a specific issueorproblem.

According our finding, six main components including general plans and policies (16 Strategies), prevention programs (6 Strategies), conservation programs (11 Strategies), training programs (11 Strategies), management planning (14 Strategies) and research and future study programs (11 Strategies) were proposed in the form of 69 strategies with three goals: reduction of sensitivity, reduction of exposure levels and increase of compatibility.

The proposed program and strategies in present study, can be used to prepare guidelines for work in hot environments. Our results can be of great help to the occupational health and safety -related organizations such as the Iran's Ministry of Health and Medical Education and Ministry of Cooperatives, Labour, and Social Welfare for planning and providing preventive procedures and control measures, in order to take effective action to maintain and improve employees' workplace health. Should be noted that the development and implementation of the mentioned policy require the cooperation of all members including employers, health and safety committee, supervisors and employees.

Efforts to improve the effectiveness of noise barriers have been made, including shape, aesthetics, form and gender. Therefore, the aim of this study was to investigate the effect of the angle upper edge in shaped noise barriers with a T-shaped upper edge. A 2D boundary element method (BEM) was used to predict the insertion loss of the tested barriers. The results obtained from the angular obstructions of the upper edge with the upper T-face were compared. The design of the angular barriers of the upper edge in the shape of the barrier caused a significant increase in the insertion loss performance, especially in the low frequency range, as compared to the upper T-shaped face. The highest amount of insertion loss in the angular barriers of the upper edge in the shaped barriers was estimated to be 3.79 dB (A) above the upper edge of T, which usually depends on the relative dimensions and position relative to the source and location of the receiver. The results of this study showed that among the tested models to determine the efficiency, the best noise barrier for controlling the traffic noise was the angular barrier with a high angle of 19 degrees compared to the other higher angles and a simple T barrier at a frequency of 315, 400, 500, and 630 Hz was obtained. The performance of the barriers  in the case of applying the angle at the upper edge on the T-shaped barrier surface is improved in comparison with the use of a simple T-barrier in lower frequencies. In this regard, the best form for applying angular obstructions with a high angle was about 19 degrees from the horizon.. The cause of this effect was the presence of a failure and reflection of the angled edges in the direction of transmission of sound wave from source to receiver. All angular barrier are able to increase the barrier performance at a specific frequency range, especially at low frequencies.

Using diesel generators is necessary for activities like welding in construction sites and it is often accompanied with noise pollution. The aim of this study was to evaluate noise pollution induced by diesel generators in construction activities in one of the districts of Tehran city.
Material and In this descriptive study, 14 construction sites were selected for the evaluation of noise pollution in Tehran, district 4. Background and diesel generators sound pressure level were measured in accordance with BS 5228(2015) and noise guidance in the area around the construction sites. Diesel generators sound pressure level at 4 points and also the audio frequency analysis, one meter away from the device was measured at a random locations around it. TES-1358, Type 2(Taiwan) sound level meter was used to measure sound pressure level and calibration was performed before and after noise measurement. The validated Noise annoyance questionnaire adopted from ISO15666 standard, completed by the residents. T test, correlation and analysis of variance was performed to analyze data using SPSS software ver. 22.
The mean equivalent sound level of diesel generators background noise were respectively 76 ± 4.05 dB(A) and 46.2 ± 1.09 dB(A) around the construction sites. Diesel generators noise around the construction sites was higher than the noise limit (background noise plus 5 dB)(P Value Diesel generators noise in the area around the construction sites was higher than the environmental noise limit and it was accompanied with abundant noise annoyance for residents around these construction sites. Therefore, due to the lack of environmental rules related to construction industry noise pollution in Iran, assessment and approving of such rules is essential to reduce noise annoyance in urban areas.

Working in hot environments is one of the common physical risks factor in the workplace, which can also cause heat-related illnesses and various health effects on workers, and also increasing the risk of injuries and occupational accidents. The purpose of this paper is review conducted studies about heat stress in different countries, investigation the indices of heat stress, the characteristics of the exposure in hot environments, high-risk occupations, and sutvey the status and importance of these studies.
In this review study used Web of Science, Scopus, Pubmed, ScienceDirect, Iran Medex, Magiran, Google Scholar and SID databases. The keywordsincluded Heat stress, heat exposure, heat waves, workplace, knowledge and attitude of workers about heat stress, the period of 2000 to 2015 was investigated, and finally 103 original articles were identifed.
90% of all study being cross-sectional studies, 41% being related to outdoor workplaces, and 42% being related to indoor environment. Most studies were carried out in the tropical zones.19 studies were about perceptions and behavioural responses of exposure to heat stress.A range of heat indices were used with 60 (71%) studies using Wet Bulb Globe Temperature Index (WBGT). Most of studied focused on manufacturing workers and farmers. Most of studies indicated that workers were suffering from heat stress and strain.
The results of studies showed that stress in workplace is worrying due to the nature of the working processes both indoor and outdoor, and of climate change. Therefore it is necessary to considering preventive and control programs to reduce the heat stress by the management and staff's participation to eliminate or reduce its lethal effects.

Regarding development of several thermal indices and limitations of these indexes, in this research we were examined the applicability and validity of Modified discomfort index (MDI) in Outdoor occupational environments.
This cross-sectional study was done on 175 subjects in summer (2016) in 12 mines construction materials of Tehran Province. Environmental and Physiological parameters (oral temperature, tympanic temperature and skin temperature) were measured simultaneously at three periods; also Modified discomfort index (MDI) together with three other Direct Indices include Wet-bulb globe temperature (WBGT), Oxford index (WD) and Wet-bulb dry temperature (WBDT) were calculated. For survey of applicability and validity of Modified discomfort index, the correlation between this index and other Direct Indices at different times of day with Physiological parameters was determined through the Pearson correlation coefficient.
The results showed that MDI index had more correlation with environmental parameters (dry bulb temperature and relative humidity), also very high correlation coefficient with wet-bulb temperature and black-globe temperature. Among the thermal indices used in this study, MDI index had more correlation coefficient with three other indices. On the other hand; MDI had the highest correlation coefficient with oral temperature and the higher correlation with the tympanic and skin temperature after the WBGT index. In all cases, there was a very good correlation between MDI and other indicators at different times of day.
It can be concluded that MDI, despite being simple, lack of need for sophisticated equipment to measure, having a high correlation with physiological parameters, low cost and easy interpretation can be used as substitute for the WBGT index in the range of temperature and humidity study.

After the engineering noise control and management control, the last way for controling noise is using the hearing protective devices, whose effectiveness depends on full-time use of it. Due to the lack of a standard questionnaire about increasing the duration of worker's usage of hearing protection devices based on BASNEF behavioral pattern, this study has been done to design and measures this tool psychometrically.
The initial questionnaire of this study is drawn out of the texts, similar articles, and questionnaires. Face Validity and Content validity are measured by Lavsheh method based on obtaining the view of experts’ panel and the reliability was done by cronbach's alpha coefficient by tile industry workers. All analyses were performed using 19 SPSS software.
Findings: face validity and content validity of 49 items were identified. In professional content evaluation, CVR of items up to 60% were selected and the CVI of the remaining questions became 0.79%. The reliability of each of below indexes was approved as follow: knowledge: 82%, attitude: 88%, abstract norms: 83%, enabling factors: 88%, behavioral intention: 96% function: 89% and the overall reliability of research tool were approved by measuring Cronbach's alpha as 88%.
Discussion & Conlusions: vThese results introduced good evidence about the validity and the reliability of measurement tools on BASNEF model in increasing duration of workers usage of hearing protection devices.

Nowadays, Noise pollution control has great importance. Noise pollution causes harm to human’s body as well as distressing calmness. One way to control noise is the use of sound absorbing materials (especially polymer foams). In recent years, composite polymers especially interpenetrating polymer networks have received much attention because of the improved properties of polymers. Polymer composites with interpenetrated polymer network structure (IPN) are widely used as sound and vibration damping agents due to their high viscoelastic properties, within the glass transition temperature range. In this study, IPNs foams of polyurethane (PU) and poly(methyl methacrylate) (PMMA) were prepared by in situ polymerization using different ratios of PU/ PMMA (85:15, 75:25 and 65:35).
IPN components including polyurethane and polyethyl methacrylate were synthesized separately to compare thermal properties, attenuation, mechanical and sound absorption coefficient of polymer. The chemical structure of the compounds was investigated by FT-IR spectroscopy and mechanical properties were studied using Tensile testing machine.
Damping and thermal properties of the samples were performed using dynamic mechanical analysis (DMA) and thermo gravimetric (TGA) respectively. Measuring the absorption coefficient was performed using the Impedance Tube (SW60, BSWA) in the frequency range from 63 to 6300 Hz, according to ISO10534-2. As indicators of effective damping capability, viscoelastic parameters including loss factor (tan δ), glass transition temperature (Tg) and effective damping interval (tan δ > 0.3) were also determined.
The formation of a semi-compatible morphology was indicated by the broad tan δ curve and two distinct transition peaks observed in the DMA curves of IPNs. The results revealed that formation of IPNs foams compound due to transform of glass transition temperature to higher temperatures and temperature of damping was increased. Therefore, in the result of the PU / PMMA IPNs damping properties were improved. Results show that because of the formation of IPN, the sound absorbing capacity of prepared samples increased at a certain frequency, and the resonance frequency shifted to lower frequencies by increasing the PMMA content in IPN foams.
Therefore,it is possible to realize a purposeful selection of sound-damping materials for solving specific technological problems by varying the composition of the material.

One of the pollutants that is developing in human life day by day is Magnetic field. In modern urban transport systems, diesel motors have been replaced with electric motors, working with alternating and direct currents, and leading to occupational exposure of drivers with magnetic fields. This study aimed to determine the urban train's drivers exposure with static magnetic fields and compare it with national occupational exposure limits.
In order to measure the train's drivers exposured with static magnetic field, several samples were selected from urban AC and DC and AC intercity trains, in the 1,2,4, and 5 lines of Tehran, Iran. After determination of the sampling location, static magnetic field was measured by three axes magnetic field meter (HI-3550), according to the standard IEEE std C95.3.1 and previous studies. In order to analyze the data, SPSS software (ver. 20) was used.
The maximum exposure of drivers was in DC trains- line 2- (0.52 mT), meanwhile, average exposure of AC trains driver (0.095 mT) was higher than DC trains driver (0.081 mT). The average magnetic flux density between different lines has not have significant differences. The highest levels of time-weighted average exposure were related to line 1 AC train drivers (0.06 mT).
Exposure of train’s drivers was 10 time higher than background level, indicating a significant exposure in this job. However, in none of the assessment situation, the whole body exposure of train’s drivers was not exceeded from National Occupational Exposure Level (TWA= 0.2 and ceiling= 2 T). Of course, it does not imply that this level of exposure is completely safe, because different studies have reported health problems even at lower values of the magnetic field.

Heat stress is caused by many factors such as individual factors, environmental factors, and management factors. Individual risk factors can decrease the heat tolerance, and play an important role in heat stress disorders incidence. The aim of this study was to review individual parameters influencing the thermal stress and review the preceding studies.
Material and In this review study sites such as Web of Science, Scopus, Pubmed, Iran Medex, Magiran, Google Scholar and SID databases were used for search. The keywords included heat stress, personal factors and heat exposure. The period of 1995 to 2015 was investigated, and finally 75 original articles were identified.
At the individual level, exposure with a single risk factor may reduce the workers’ heat tolerance; while exposure with a combination of several risk factors probably synergistically increases the risk of heat-related disorders. Individual risk factors include age, gender, obesity, fatigue, race, and previous heat disorders and dehydration. In addition, some diseases (such as cardiovascular disease, diabetes and infectious diseases) or use of certain drugs or alcohol can reduce the heat tolerance.
It is necessary to pay attention to the mentioned items when selecting workers in the hot environments. Also, due to the lack of awareness and knowledge of workers, it is necessary to provide appropriate training programs to reduce the effects of heat stress.

In large cities (metropolitan areas) the most important causes of noise pollution are transport systems, urban land uses, including heavy industries, workshop and noisy jobs. The workshops scattered throughout Tehran, such as carpentry, turnery, smoothing and smithery, in the vicinity of residential areas, and educational-healthcare centers can increase and affect the noise pollution level.
To determine the status of industries activities and occupations which are responsible for noise pollution and noise pollution increase in Tehran, an extensive study was carried out. Then the list of all the jobs and activities located within the boundaries of zone 3 of district 12 of Tehran were identified. Classification of noise polluting occupations in the study area was done in A, B groups. According to the results, the noise polluting jobs were identified to be about 1845 in number. The highest number of jobes was related to shoe manufacturing units, molding and casting and the lowest number was related to coppersmithing.
After presenting the SPL and Leq charts and also roviding the GIS maps the amounts SPL and Leq from the workshop in the study area were obtained. The maximum SPL belonged to thinsmithing and coppersmithing units and the maximum Leq belonged to bending units. The turnery workshps, in spite of having low SPL, were identified to be the noisiest units because of their high levels of activity duration and the area used. Considering the high SPL and the area used, bending workshop was ranked in the second place, and the rest of the workshops were ranked subsecuently.

Noise is one of the most important physical agents in the workplace which causes numerous effects on physical and mental health. Hence its elimination or control is necessary in noisy industrial workplaces. Saab dyamples device is one of the most important sources of noise in the sub line in granite industry. Thus, this study intended to reduce noise using enclosure method in Behsaram granite company.
Due to the high level of noise produced by dyamples, in this study, the enclosure technique was used to encapsulate the noise area. After measurement and analysis, the required noise reduction was determined. A chamber with dimensions of 1.5×1.55×1.8 m3with an opening in front for observation and another opening in the back for access to control keys. The chamber was manufactured from galvanized stainless steel with 0.55 thickness and 6 kg/m2 density with a glass wool cover with 2 inches thickness.
The noise level before and after enclosure was 93.63 dB and 86.91 dB, respectively. According to the measured values before and after the installation of the chamber.
Considering noise reduction, it is recommended that engineering controls (enclosure) in similar industries could reduce exposure of the workers to high level of noise.