Journal of Health and Safety at Work

Introduction: The power tiller is a multipurpose hand tractor designed primarily for rotary tilling and other farm operations. Vibration, transmitted from the handles of the tiller to the operators’ body, causes many injuries such as, pain, musculoskeletal disorders and white finger syndrome. The aim of this study was to evaluate the hand-arm vibration exposure in the operators of tiller model HT900, as the most frequently used model of tillers.

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Material and Method: In this study, 40 operators tiller of model HT900 in the city of Kashmar, Khorasan Razavi were examined. Hand-arm vibration measurement was done according to ISO 5349-1 and ISO 5349-2 in three different modes including, static and neutral (mode), transition to the ground mode and plowing the land mode in different gears. In order to measure the vibrations, human response vibration meter of B and K model 2512 was utilized.

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Result: Results of the present study indicated that in all measured situations, exposure to hand arm vibration was higher than the standard limit suggested by Iranian occupational health committee and there was risk of vibration-induced disorders. The maximum exposure to vibration is in plowing ground. Exposure to hand arm vibration in three modes of plowing, transmission and natural, were respectively 16.95, 14.16 and 8.65 meters per second squared. Additionally, in all situations, vibration exposure was highest in the X-axis in comparison with Z- and Y-axes.

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Conclusion: This study emphasizes on the need to provide intervention and controlling and managing strategies in order to eliminate or reduce vibration transmitted from tiller to operators hand and arm and also prevent to serious problems including neurovascular disorders, discomfort and white finger syndrome. Meanwhile, more studies are necessary to identify the sources of vibration on different models of tiller.

Introduction: Tractor drivers are continuously exposed to whole body vibration during driving that, this may cause disorders in the system of musculoskeletal, nervous, circulatory and occupational diseases. The aim of this study was to evaluate exposed to whole body vibration among tractor driver.

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Material and Method: In this study, whole-body vibration parameters such as root mean square (rms) of acceleration , total equivalent acceleration, vibration dose value (VDV) and crest factor (CF) were separately compared in three directions (x, y, and z) , in 3 Massey Ferguson Model 165 Tractor it was done during 3 different modes of transport (without trailer, with empty trailer and with a trailer load of soil) , plowing the land and loading trailer in working conditions with various gear according to the guidelines of ISO 2631 standard.

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Result: The results showed that in all measuring points, exposure to whole body vibration was higher than permissible level and the risks of disorders exist. Exposure to vibration were as with empty trailer (43.11m/s2). The maximum of crest factor was obtained for transportation mode of empty trailer with 3 gear (10.7), then plowing (7.35) and loading soil(6.50). The maximum of vibration dose value was eventuated for transportation mode with empty trailer with 4 gear (189.92 m/s1.75) and 3 gear (108.15m/s1.75). In all measuring modes exposure with vibration in Y direction was greater than X and Z axes.

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Conclusion: This study shows that the need to provide intervention , controlling and managing measures to eliminate or reduce exposure to whole body vibration among tractor drivers its necessary. And, preventing main disorder Including musculoskeletal disorders, discomfort and early fatigue is of circular importance. More studies are also necessary to identify the sources of vibration among various of tractors.

Introduction: Noise is one of the most common health hazards at the workplaces that can cause not only somatic problems, but also adversely affect mental health. The aim of this study was to investigate and evaluate occupational noise exposure and noise annoyance in one of the petrochemical companies.

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Material and Method: The study population included 47 people working in Administrative and Manufacturing parts of the petrochemical company. First, dosimetry of production workers and noise frequency analysis of Administrative employees were performed. Then, self-report questionnaire for the assessment of noise annoyance at workplace was completed by the subjects. The questionnaire consisted of three parts: scoring of the noise intensity in the workplace, scoring of the noise annoyance in the workplace and determining the feelings and emotions (e.g. fatigue, sleepiness, and concentration problems) that experienced by subjects during the working day.

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Result: The results of noise dosimetry measurements showed that mean eight hour equivalent continuous A-weighted sound pressure level was 86.13 dBA. According to the frequency analysis of office rooms, mean noise level and Preferred Noise-Criteria (PNC) was 69.4 dBA and 62 dB, respectively. The findings of our analysis revealed that 17.9% of administrative staff and 63.2% of manufacturing workers assigned “very high” score to the noise intensity in the workplace. The annoyance score was obtained “very annoyed” by 10% of employees of office section and 42% of manufacturing workers. For noise-related complaints and sensations defined by subjects, 49% of administrative staff and 60% of manufacturing workers marked the “sometimes” and “more” item of the questionary.

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Conclusion: Based on the obtained results of investigating the noise level (objective exposure) as well as the noise annoyance (subjective exposure) at the studied company, it is necessary to adopt the management –technical noise reduction measures at manufacturing sectors as the personal noise exposure and environmental noise exposure and also noise personal exposure of administrative staff can be decreased.

Introduction: Noise is one of hazardous agents of workplaces in industries. Electric industries and power plants are among industries in which noise pollution should be taken into account. This study aimed to develop and verify a statistical model for acoustic wave propagation in an indoor environment for noise related risk reduction management.

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Material and Method: This theoretical-experimental study was performed in a gas power plant with nominal capacity of 648 MW including four gas turbine with nominal capacity of 162 MW. The relations between sound power level and sound pressure level in indoor environments were used for developing the statistical model. Moreover, verification of the obtained data was done by a field inside a turbine hall study using ISO9612 standard method.

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Result: Comparison of results from the field and the theoretical study showed no significant differences. The differences between predicted value and field measurements was, in average, less than 0.5 db. This shows the acceptable accuracy of the presented model in estimating the workplace noise level, according to the real functional conditions of the noise sources.

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Conclusion: The presented model is easy and practical and allows managers to model scenarios of noise pollution reduction in indoor environments, before huge expenses of actual control measures. This method is faster comparing to numerical modeling methods. Furthermore, its accuracy is also acceptable.

Introduction: The previous studies have used fibrous absorbents usually in the form of cone-shaped wedges for making anechoic and semi-anechoic chambers which their design and construction have been costly and difficult. The present study aimed to design a semi-anechoic chamber, using rectangular fibrous absorbents and also perform acoustic analysis for it.

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Material and Method: In the present study, which was done at semi-anechoic chamber of the laboratory in Tehran University of Medical Sciences. The reverberation time, the total surface and the absorption surface of the chamber were determined, before and after the design and also they were compared with the target values. Intersection layout of the rectangular fibrous absorbents were design using graphic design software (AutoCAD and 3Ds Max). before design, the reverberation time were measured according to ISO 3382:2000. The reverberation time in redesigned chamber was also calculated through retention time equation (Sabine). Moreover, Sabin’s formula was applied for determining the absorption surface and the total surface of the chamber, before and after the design.

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Result: Before design, the reverberation time in the cut-off frequency of 250 Hz according to ISO 3382:2000 was determined 0.3 second. Moreover, the total chamber surface was 47.97 m2. CAD software estimated at least 253 rectangular absorbents with dimensions of 50×18 cm. After design, the absorption surface and the total chamber surface were obtained 46.32 m2 and92.64 m2, respectively and the reverberation time in the mentioned frequency was 0.07 (s).

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Conclusion: According to the results, it can be concluded that the suggested intersection layout of rectangular fibrous absorbents can be used as a reliable method in order to reduce the reverberation time and to gain lower cut-off frequency for construct a semi anechoic chamber with the high efficiency.

Introduction: According to previous researches, working at the airport is one of the most vociferous jobs in the world. Airport workers are at risk of noise induced hearing loss. The present study was done to evaluate the Sound Pressure Level (SPL) in the closest aprons to Ground Safety department at Mehrabad airport and to investigate the effect of airport noise on the employees of this department.

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Material and Methods: Evaluation of SPL in the given aprons was done using sound meter and sound analyzer. Measurement stations at specific intervals to the sound source were identified inside and outside of the participants 'workplace and SPL was measured at night and day. The mean estimated values were compared with those presented by Ministry of Health. The annual participants' audiometry information was extracted from medical records. Then a self-administered questionnaire was distributed among the study sample in order to measure quality of noise exposure. The questionnaire was developed based on three general criteria including the knowledge toward the noise pollution, job satisfaction, and the exposure to the noise source and the purpose of this questionnaire was to find the relationship (correlation) between these parameters among the study population.

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Result: The measured equivalent for 8 hours noise exposure was obtained 94 dB(A) and no relation was observed between octave band sound of aircraft and recorded audiometry. Analysis of the questionnaire showed that people with more knowledge about noise pollution used more hearing protective equipment. Subsequently, by using more hearing protection equipment the level of hearing loss was reduced significantly (P<0.05). There was a significant and negative correlation between noise exposure and job satisfaction, as well (P<0.05). Also there was a significant and negative correlation between using of ear muffs and catching Noise-Induced Hearing Loss (P<0.1). The percentage of noise-induced hearing loss was calculated 51.4% among study sample.

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Conclusion: The noise exposure of employees of Ground Safety working in Mehrabad airport was higher than the permissible limit which implies the necessity for use of earmuffs and implementation of noise reduction programs.

Introduction: Noise pollution in urban areas has been recognized as a major problem. Since hearing damages are the main concern of noise exposure, other physical and psychological effects should not be ignored. Noise-induced annoyance and consequently its side-effects, such as fatigue and loss of concentration, would increase the probability of human errors occurrence and occasionally irreversible occupational accidents. This matter show the importance of noise exposure level from the standpoint of both community health and workplace safety.

Material and Method: This cross-sectional study was conducted to investigate the annoyance caused by air transportation noise in tehran, 2014. In this sense, a sample of 200 individuals were selected from residential and nonindustrial noise-exposed population in four southwest regions in Tehran. Following, the study questionnaires including annoyance (Recommended based on ISO 15666-2003), visibility of airplane, noise perception, and demographic variables were distributed and completed by the participants. Data obtained from Integrated Noise Model (INM) and geographic coordinates of measurement stations, recorded by Glopal Positioning System (GPS), were entered into the GIS software in order to estimate air traffic noise.

Result: The present study showed that the equivalent sound level of all regions during night, the day average sound level only in the Simetry Jey area, and the average night noise level in all regions except Dorahi Ghopan were more than the acceptable level; and the most precentage of people with high annoyance was belonged to night annoyance rate. On the other hand, the correlation between day level (DL) and day annoyance rate (P=0.01, R=0.142), night level and night annoyance rate (P=0.004, R=0.334), and Day-Night Average Sound Level (DNL) and the day-night annoyance rate (P<0.0001, R=0.235) were obtained statistically significant.

Conclusion: Adopting management srategies for reduction of number of night flights or engineering measures such as improving construction to decrease the rate of receiving noise by exposed people can have a positive considerable effect on declining noise pollution and individuals’ annoyance rate.

Introduction: To evaluate heat stress in the workplace different indices are used. But, none of these measures have been widely accepted. The aim of this study was to determine effective criteria in selecting a heat stress index and weighting of these criteria.

Material and Method:  This study is a qualitative study that was designed and conducted within 10 stages. In the current study, effective criteria for choosing a heat stress index was determined by using Delphi technique and expert’s opinions (30 people), and then the fuzzy analytic hierarchy process was used for weighting and prioritization of these criteria.

Results: Analyzing the completed questionnaires by the experts and according to the percentage of respondents, 11 criteria were finally selected. “Simplicity” criteria by %76.6 had the highest percentage of response. But, the relative weight of this criteria was 0.041, and had the lowest weight after the “low cost” criteria.  The criteria relating to the “Standard” item was 0.141as the highest relative weight.

Conclusion: It can be concluded that the first step to have a reliable and accurate measurement is to choose a proper and correct index. Based on specialists and expert’s opinions, standardization of the index is the most important selection criteria. Other criteria that must be considered were accuracy, reliability and good correlation with the physiological strain indices.

Introduction: 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 Method: 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.

Result: 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.

Conclusion: 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.

Introduction: Chronic occupational noise exposure may constitute a risk factor for cardiovascular disease for workers. The aim of this study was to investigate the relationship between occupational noise exposure and noise annoyance with blood pressure, serum cholesterol and triglyceride levels in workers of a textile industry.

Material and Method: This cross-sectional study was carried out among 220 employees of Savadkouh textile industry complex in Mazandaran province, Iran in 2017. To achieve the study objectives, the 8 -hour equivalent sound exposure level was measured and the cumulative noise exposure was calculated. Based on noise exposure level, workers were divided into control and case groups. Then, blood pressure was measured and blood samples were collected from each individual for determination of the serum cholesterol and triglyceride levels and they were transfered to the laboratory for further analysis. The noise annoyance scale and socio-demographic questionnaire were used to collect noise annoyance and other background and demographic information, respectively. Finally, Paired t-test, one-way ANOVA and multivariate regression were used to study the relationship between variables using SPSS Version 20.

Result: In total, 159 workers participated in this study considering the inclusion and exclusion criteria. Eighty-three participants were exposed to more than or equal to 85 dBA, and 76 person were exposed to less than 85 dBA noise level, respectively. The results showed that mean blood pressure and cholesterol were significantly different between the control and case groups (P-value< 0.05). Based on multivariate regression results, noise exposure, cumulative noise exposure (CNE) and noise annoyance had a significant effect on blood pressure (P-value< 0.001).  Cholesterol was also significantly affected by noise exposure and noise annoyance (P-value< 0.005).

Conclusion: Based on the results of current study, noise can be considered as a risk factor for cardiovascular disease ampong workers. Actually, high intensity noise affect serum cholesterol and blood pressure directly, and may do indirectly by causing noise annoyance which acts as a mediator. Therefore, it seems necessary to conduct a controlled cohort study to investigating the interactions among whole variables of interest.