Journal of Health and Safety at Work

Background: Generally every different machines which are implemented in industries, agriculture and transport systems exposed human to excessive vibration. The produced vibration can reduce comfort and productivity and also cause adverse effect on human health and safety. Long term human exposure to high vibration levels may lead to physiological disorders.

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Material and methods: This paper presents the results of an experimental study which is done on 584 students of Tehran University of medical sciences. The data was gathered by interview and a validated questionnaire. In this study the stimulus was produced by a calibrated 3 axis vibrated seat. The voltage of stimuli was 90 and 95 V in two different frequencies of 20 and 25 Hz in two axis of x and y. During exposure the transferred whole body vibration was monitored by a calibrated whole body vibration meter.

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Finding: The results of this investigation showed that whole body vibration effect on mental disorder is significantly higher among female compared with that of in male. The disorder induced by frequency of 25 Hz was three times higher than that of produced by 20 Hz. The frequency of mental disorders was increased by rising vibration acceleration. It was also found that taller people are slightly less sensitive to the range of tested frequencies and acceleration compared with of shorter one.

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Conclusion: A significant relation between height and mental disorders was found in this study which can be used on whole body vibration exposure management.

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: Whole body vibration occurs when human is on a vibrating surface and the vibration influences parts of the body which are far from the contacted part. Up to now, various health-related problems due to whole body vibration have been reported, including back pain, sciatica, gastrointestinal problems, genital problems and hearing impairment. In the present research, vibration was measured about 2000 minutes in 23 train of 4 active lines of Tehran metro in order to determine the rate of subway drivers’ exposed to whole body vibration.
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Material and Method: Vibration meter and SVAN 958 analyzer, made by Svantek company, were utilized for measuring the whole body vibration. The level of weighted r.m.s acceleration for each axis, the combination of axes, peak factor, VDV and other common exiting ratios in the standard were measured and calculated according to ISO 2631-1.
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Result: Findings showed that according to Basic method drivers exposure to vibration is less than the lowest value of health guide critical region (<0.45m/s2). However, based on Vibration Dose Valuation (VDV), the exposure of 12 cases were higher than the lowest value (<8.5 m/s1.75) and only 11 cases were lower than the mentioned amount.
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Conclusion: Investigation of the result obtained from Basic method and VDV method manifested different amounts of vibration exposure in a way that VDV predicts higher level of risk, compared to basic method. The results shows that some presented indicators can not presented the safe zone in human vibration evaluations.

Introduction: Whole-body vibration is one of the factors which may have adverse effects on the comfort of passengers and crew of rail transportation vehicles. In this study, the probable impacts of whole-body vibration were explored on the convenience of the passengers of Tehran metro.
 

Material and methods: Planning, measurement, and pre-analysis calculations were mainly done based on ISO guidelines No. 2631-1, 4. Moreover, measurements and calculations were done using SVAN 958 sound & vibration analysis and Microsoft Excel software, respectively.
 

Results: Average calculated RMS acceleration values on the levels of seat cushion, seat back, and legs were 0.57, 0.44, and 0.64 m/s² on the dominant axes, and total r.m.s acceleration in all these three levels equaled to 1.02 with the standard deviation of 0.11 m/s². Mean Vibration Dose Value (VDV) of total exposure in the minimum and maximum exposure durations were 6.44 and 9.63 m/s ^1.75, respectively.
 

Conclusion: Calculated amounts of dominant axes were mainly ranked as “relatively unpleasant” in the convenience limits of ISO 2631-1, but the total calculated amount of exposure based on WRMS was at “unpleasant level”. The measured VDV amounts were mostly on the z axis, as the dominant one.

Introduction: Exposure to vibration as one of the consequences of industrial noise or the use of vibration generators can cause discomfort, reduce the efficiency and level of safety in workplaces. Therefore, in this study, the effect of whole body vibration on individual’s mental performance and response time was investigated.

Material and Method: In this study, 40 male students of Tehran University of Medical Sciences were selected randomly and divided into two 20 subjects groups. Each group participated in two Pegboard Board and Math Calculations tests. Subjects in each stage of test were exposed to whole body vibration with acceleration in 0.8 and 1.1 m/s2 as well as background mode without vibration and were investigated response time and mental performance.

Result: In the present study, the mean response time to the manual Purdue Pegboard test in the vibrational acceleration of 0.0, 0.8 and 1.1 m/s2 with a decreasing trend was 197.55 ± 2.7, 176.25 ± 5.38 and 177.58 ± 2.92, respectively, which results in a significant reduction in the accuracy of the test. Also, the results showed that whole body vibration does not affect mental performance in shallow levels. But, in the intermediate and deep levels, this difference is statistically significant (p <0.001).

Conclusion: Based on the results, whole body vibration is an effective factor in individual’s response time and mental performance, which can lead to a reduction in the accuracy of the work.