نشریه طب کار
سال ششم شماره 1 (پیاپی 14، بهار 1393)

In continuing our work on effects of noise stress, this study aimed to determine the effect of noise stress on the anxiety and the volume of the amygdale nuclei as a key brain component plays role in the anxiety. In this experimental study, two-months old Wistar male rats were randomly divided into noise stress and control groups (n=10 in each group). Control rats were maintained under standard laboratory conditions and noise-stressed rats were exposed to 75 dB noise (1100Hz), 20 min/3 times/day for 90 days. The anxiety behaviors were assessed applying elevated plus maze and Territory discrimination test. Coronal serial sections of 25 µm thickness through rat amygdale were made. Every 2th section was selected and the volume of amygdale nuclei was determined by using Cavalieri's principle. Results indicated that the noise-exposed rats had fewer entrances to open arm of elevated plus maze and spend less time in this arm. In territory discrimination test, noise stressed group had more latency to enter in unknown compartment. The volume of lateral nucleus of amygdale was significantly higher in noise stressed group compared to control animal. Result of this study indicated that the chronic exposure to noise induces anxiety behavior and caused increase in central nucleus of amygdale volume. In this view, our experimental research may present a useful approach in understanding some aspects of the pathophysioloy of anxiety disorders due to noise stress.

The importance of ergonomics is to create fit between work and human physiology using assessment methods of physical, physiological and subjective evaluation. The most commonly used tool for assessment of subjective symptoms is Borg scale during physical work and heart rate in physiological situations. This study is based on a subjective and physiological assessment during hard work in one of the metal industry in Isfahan. In this study, 200 male workers have entered voluntarily according to the Strand study protocol and were evaluated by ergometer. Subjects were asked to report Borg scale at the end of each minute pricing during the experiment, and the heart rate at the end of each minute was recorded by the device. There was a very strong correlation between the perceived intensity of effort as a subjective factor and ergometer increased workload (R^2= 0/91),(P<0.0001). Heart rate as a physiological factor associated with an increased workload and stiffness (R^2=0/96),(P<0.0001). Linear regression analysis of the relationship between perceived effort and workload was as equation Workload= 126.54 - 4.45 (RPE) and linear regression analysis of the relationship between heart rate and physical workload was as equation Workload= 125.89 – 0.54 (HR). In other words, the physical workload and heart rate has a more significant relationship than rating of perceived exertion with physical workload. Consequences: With a developed regression equation without any laboratory facilities, the workload of physical work is easily measurable. The physical working ability could be estimated based on measuring heart rate during work, or on the basis of changes in perceived physical ability and mental labor monitoring, so the required periodic checkups, education, etc. could be done.

Nowadays the tendency of understanding how effective management practices and organizational factors have highly developed and activities mostly focus on safety culture and climate. Despite extensive studies in the field of safety climate in different countries, few attempts have been made in Iran which in most of them the toolkit of Loughborough university has been used. The aim of present study was safety assessment of an Iranian commercial port, which was for the first time, by Nordic questionnaire. In this cross-sectional study 75 workers, which had 7 different occupations in that port, were selected and completed the questionnaire. For determination of validity and reliability of the questionnaire, 25 copies were completed and the coefficient of internal consistency was calculated. Seventy five copies of the finalized questionnaire were given to the safety management section of the port to be completed by self reporting system. The safety climate profile showed the average dimensions were in the range of 3.25 to 4.22. The highest score was for dimension of worker's trust in efficacy of safety systems (4.05) and the lowest was for dimension of worker's safety priority and non-acceptance risk (3.32). The highest and lowest score for safety climate were given by groups of cleaners (4.22) and staff (3.25) respectively. The differences of mean score between occupational groups were significant and between age, years of experience, and level of education groups were not significant. Because the worker's perception of safety does not depend on their age, years of experience, and level of education, then safety training is not implemented. Not significance of the average score of safety climate with the level of education means that the safety education in schools and universities is not good.

Vibration of body especially that of hand-arm is a key factor in developing inconvenience in drivers, which decreases efficiency, triggers fatigue and disturbance in physiological activities, and finally predisposes drivers to occupational diseases and traffic accidents. This study examines the effect of hydraulic steering wheel system on controlling and attenuation of the vibrations transmitted to driver’s hand-arm. This cross-sectional study was carried out according to convenience sampling on two perfectly homogeneous automobile groups (15 with hydraulic steering wheel and 15 without hydraulic steering wheel). Steering wheel vibration measurement was carried out in three vibration axes and three specified positions of automobile movement (in the same atmospheric and physical conditions) using Bruel & Kjaer-2231 Vibrometer. The data were analyzed by SPSS 11.5 using t-test and two-way ANOVA. The results indicated that the superior effective acceleration axis in the two groups. of automobiles and in three measurement positions is axis Y. Comparing the results with the 4-hour standard showed that in all positions the effective acceleration (in rms) is less than the permitted exposure limits and care limits (p<0.05). Also, compared to the standard 8- and 16-hour values, some of the positions were higher than the permitted and care limits (p<0.05) and some had no significance difference from the standards (p≥0.05). Two-way ANOVA showed that the type of steering wheel system, speed, and gear (measurement positions), independently, simultaneously, and jointly, are effective on the vibration transmitted to the drivers’ arm (p<0.05). In contrast to the whole body vibration where axis Z has been reported as axis with superior effective acceleration, in the vibrations derived from steering wheel the axis with superior effective acceleration is axis Y and the hydraulic steering wheel can significantly decrease the vibration transmission to the drivers’ hand and arm. On the other hand, the decrease in hours spent for working with the automobiles without hydraulic steering wheel can be considered as a very useful managerial tool.

Emotional intelligence is a group of abilities and non cognitive skills that increase individual success ability against stress and environment contingency specially burn-out and jab stress. The aim of this research was assessment the relation between emotional intelligence and burn-out among the managers and nurses in university hospitals in Yazd. This research is of correlation type which 200 subject selected randomly and participated in this research. The degree of emotional intelligence behaviors and burn-out was evaluated by questionnaires. Correlation coefficient of Pearson's and step by step coefficient of regression and t-test used to for data analysis at the level significant P<0.05. Significantly difference of emotional intelligence and burn-out among two genders was observed (P<0.05). Also reverse significantly correlation between emotional intelligence and burn-out was observed (P<0.05). Emotional intelligence behaviors especially self-perception, empathy and motivation had significantly affect on burn-out anticipation. Emotional intelligence behaviors could decrease burn-out, so we could suggest that medical organizations try to have educational periods to increase emotional intelligence and reduce burn-out.

Exposure to high temperatures is common among workers in warm environments (especially in bakeries) which could cause some undesirable physiological effects. The aim of this study was to determine heat stress and its relationship with physiological parameter of sublingual temperature in workers employed in bakeries of Arak city. In this cross- sectional study, 126 workers employed in 63 bakeries in Arak was evaluated. Heat stress was evaluated based on WBGT (wet bulb globe temperature) index and physiological strain was evaluated based on sublingual temperature. The heat stress was measured using digital WBGT apparatus in workstations of the bakers and the bread dough co-bakers as the hottest places. Sublingual temperature of workers was measured using electronic sublingual thermometer. Data was analyzed using SPSS version 16 software. In 76% of cases, heat stress exposed to workers based on WBGT index, was more than national recommended limit. Moreover, in 48% of cases, heat strain of workers based on sublingual temperature index was also more than the national recommended limit. The results showed significant difference between WBGT index in the bakeries based on baking technology type (traditional and mechanized bakeries) (p<0.001). The results showed significant difference between sublingual temperatures of workers in the bakeries based on baking technology type (p<0.001). Mechanization of bakeries could make notable effects on reducing the heat strain of workers. The significant relationship between WBGT index and sublingual temperatures of workers confirmed the reliability and generality of WBGT index for evaluating heat stress in bakeries.

Heavy vehicle transportation continues to grow in Iran, yet the risk of injury and death has increased during the recent decades. In Iran, there are more than 22000 deaths annually due to road accidents which is the highest in the world. Many of these accidents are related to poor sleep quality in professional drivers. The most significant detrimental consequence of poor quality of sleep is degradation in driver's performance. This study has been conducted to assess the sleep quality of commercial drivers and its relation factors. This cross-sectional study was done in 2011. One thousand and five hundred commercial drivers who consequently referred for health training course were chosen. A two sectional self-administered questionnaire was used: the first section included demographic characteristics of participants, while the second section included the Pittsburg sleep quality index (PSQI). Data were analyzed by T-test, Chi-square and Multivariate logistic regression using SPSS 11.5 software. The mean age of drivers was 36.6±9.4. Mean number of work hours/day was 9.3±2.5. About 24% of drivers were reported history of smoking, 14.4 % had low job satisfaction and 30.1% worked as shift worker. Mean PSQI was 5.6±2.7 and 62.3% had a PSQI>5. Multivariate logistic regression showed that smoking, job satisfaction, shift work and work hours/day were the most important factors that affect driver's sleep quality. This study showed a high prevalence of poor sleep quality in Iranian commercial drivers.