Journal of Health and Safety at Work

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Introduction: Safety signs provide information,related to hazards or dangers in the industry,in form of instructions. These signs are effective as long as they are designed in accordance with principles of ergonomics and design cognitive features. The purpose of this present research was to study the relationship between cognitive features of signs and ability to guess, and to develop the relevant regression model.

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Materials and methods: This descriptive cross-sectional study was carried out on 100 employees in a petrochemical industry complex. A three part questionnaire was used to collect required data while first part of the questionnaire dealt with demographic information, second part included cognitive features of signs designand the third part proceeded on testing the ability to guess. Then, a regression model was developed to determine the relationship between cognitive features, and the ability to guess.

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Results: Mean and standard deviation obtained for the ability to guess the total study signs were 63.73 and 4.36, respectively. The feature of “familiarity” obtained the lowest possible score (49.15). The “semantic closeness” (β=0/390) and “meaningfulness” (β=0/369) had the highest correlation with the ability to guess safety signs.

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Conclusion: According to results of this study, use of principles of ergonomic design of signs and training are necessary to promote the ability to guess the safety signs to the minimum available standards. Therefore, it is possible to balance cognitive features especially “familiarity”, with the lowest score, and “meaningfulness” and “semantic closeness”, with the highest influential relationship with the ability to guess of signs. The developed regression model for this industry can be used to predict the ability to guess of safety signs in future studies

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Introduction: Considering the accreditation of international standards of hospitals and the necessity to improve the safety and quality of patients’ care, this study aimed at evaluating reliability among nurses using predictive analysis of cognitive errors and human event analysis techniques.
Material and Methods: The analysis of nurses̓ tasks was done by HTA method. Then, the types of errors and their causes were identified by TRACER method. In the next step, the error probability of each task was calculated by ATHEANA method. In order to calculate the probability of total event, the probability of human error was imported to probabilistic risk assessment.
Results: Factors affecting performance of the nurses were included: the complexity of the work, high workload, nurse’s experience, work environment design, fatigue, anxiety, shortage of the workforce, insufficient time period for doing job, sleep disturbance, and poor lighting and noise pollution. According to the instruction of ATHEANA method, the error probability for each base event was considered 0.001. Given that there are 15 base events, the probability of human error in the heart attack event was calculated 0.015.
Conclusion: The finding of this study was indicated the need for providing required nursing workforce, reducing overtime, scientific planning for nurses’ work shifts and giving practical training and stress management methods in the emergency conditions.

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Introduction: Heat stress is a critical problem in hot industries, especially in incredibly hot climates. It can greatly impair the work process and put the health of workers at risk. This study aims to investigate the applicability of the WBGT index in determining the allowable working time in very hot weather conditions in one of the steel industries in Ahvaz.
Material and Methods: This study was conducted in different sectors of a steel industry in Ahwaz. The physiological parameters of sixty workers working in different parts of the industry were evaluated. Environmental variables and the Wet-Bulb globe temperature (WBGT) Index were also simultaneously measured during work shifts. The acceptable work time was calculated based on the reserve heart rate (RHR) and the WBGT index.
Results: The heat stress index among all occupational groups, based on the WBGT index, was incredibly high and surpassed the recommended level (P<0.05). The statistical test results also indicated a significant difference between the two indices in predicting the adequate work time at different work stations (P <0.05).
Conclusion: The current study results revealed that using the WBGT index for assessing and managing the risk of heat exposure in a hot climate may not have sufficient reliability and performance. Consequently, it is recommended to use optimal indices based on environmental and physiological assessments in a hot climate in order to monitor and control the heat stress associated with heat exposure. 

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Introduction: Occupational back pain is one of the musculoskeletal disorders (MSDs) caused by manual load-lifting among women involved in manual lifting activities. Limits for lifting loads are used to assess the risk and prevention of occupational back pain. The Washington Industrial Safety and Health Act (WISHA) checklist is used as a permissible load assessment limit in Iran. The present study aimed to evaluate the reliability of using the WISHA checklist to determine the allowable limits of manual load-lifting among women based on biomechanical and psychophysical methods.
Material and Methods: In this study, ten women workers aged 20-30 years with a history of manual load-lifting were asked to perform 21 load-lifting tasks designed according to the permitted limits of Iran. A wireless electronic clinometer was used to determine the flexion angles of the trunk while lifting the load. Anthropometric information, load weight, trunk angle, and posture were entered into 3DSSPP software to obtain biomechanical forces for each task and compared them with the recommended National Institute for Occupational Safety and Health (NIOSH) limits. After performing each task, the rate of perceived exertion of each person for each task was collected by using the Borg scale.
Results: The flexion angle for 47.61% of the lifting tasks were more than 20 degrees. The estimated average compressive force for the six tasks exceeded NIOSH’s recommended limits. The average Borg scale was determined hard for 33.33% of lifting tasks and hard to very hard for 9.52% of tasks.
Conclusion: It was found that the manual load-lifting standard for some tasks might not be sufficient to control and prevent low back pain caused by manual lifting in women, and some non-compliance was found with the allowable lifting limits. Manual load-lifting with anthropometric and biomechanical features may increase the biomechanical force on the women’s low back. Therefore, it seems that the allowable lifting limits of Iran for women based on the WISHA checklist should be reviewed and redesigned based on anthropometric and biomechanical characteristics.

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Introduction: Musculoskeletal disorders (MSDs) have a multifactorial nature. Biomechanical factors are one of the most important factors. Consequently, the precise identification of effective factors plays a significant role in controlling and preventing these disorders. Therefore, the current study aimed to identify the awkward upper body postures and their effect on the prevalence of MSDs in office workers in both women and men groups by objective methods.
Material and Methods: In this cross-sectional study, the participants were 36 office workers (18 women and 18 men). The prevalence of musculoskeletal discomfort was evaluated using the Nordic questionnaire. The upper limbs posture, including the back, neck, and wrists, was evaluated continuously with an electronic inclinometer and an electrogoniometer for 30 min, followed by analyzing the collected data.
Results: The results revealed that the highest prevalence of musculoskeletal symptoms in both gender groups was in the neck (58.33%), trunk (52.77%), and wrist (47.22%), respectively. The results disclosed that the median trunk and neck flexion in both groups is over 20° and the posture angle in women is higher than that of men (P<0.05). The results showed that pain and discomfort in the trunk and neck in both gender groups have a significant relationship with the median posture angle (P<0.05). Also, the wrist posture in both gender groups during work was in extension and static condition.
Conclusion: Based on the results of this study, the prevalence of disorders in women was higher than in men. Although the tasks performed in both groups were similar, the assessment of postures disclosed that women office workers had more awkward postures in the trunk and neck than men. In both groups, the prevalence of musculoskeletal discomfort had a significant relationship with awkward postures in the trunk and neck. According to the results of the current study, ergonomic interventions are recommended to reduce awkward postures and to prevent MSDs, particularly among women office workers.

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Introduction: Biomechanical risk factors, including wrist and elbow angle and standing and sitting position, are the primary factors affecting hand grip strength and perceived exertion. The interaction of these factors can include different effects on grip strength and perceived exertion. Therefore, the present study examines the interaction of varying wrist and elbow angles in sitting and standing postures on the variability of grip strength and perceived exertion.
Material and Methods: In the present study, 30 students (15 females, 15 males) aged 19-30 participated. The average grip strength was measured by a dynamometer for 12 different positions based on the angle of the wrist and elbow in both standing and sitting postures. Perceived exertion was also assessed using the Borg CR-10 scale for each setting. Data analysis was performed using SPSS 23. The Wilcoxon test was applied to compare perceived exertion between standing and sitting postures. Furthermore, a three-way ANOVA was performed to examine interactions between posture (standing/sitting), elbow, and wrist angles. Mauchly’s Sphericity Test was applied to confirm the ANOVA assumptions, and effect sizes for multivariate analysis were calculated (partial η2).
Results: In both sitting and standing postures, the highest average grip strength was observed at a 0-degree wrist angle with a 90-degree elbow angle (standing: 28.6 ± 10.8, sitting 25.8 ± 9.8), while the lowest average grip strength was recorded at full wrist extension with a 0-degree elbow angle (standing: 19.3 ± 6.5, sitting 17.9 ± 6.9). In all three elbow angles examined (0°, 60°, and 90°), the highest value of perceived exertion was recorded in the full extension of the wrist. The changes in the grip strength at different angles were the same for sitting and standing postures, yet the hand grip strength was higher in the standing than the sitting posture (P-value<0.001). The effect of each of the studied factors (sitting and standing postures, wrist angle, and elbow angle) alone on hand grip strength and perceived exertion was deemed to be significant (P-value<0.001). Regarding the two-way interactions of the research variables, the interaction effect of elbow and wrist angles on grip strength (partial η2=0.09, P-value=0.015) and perceived exertion was significant (partial η2=0.08, P-value=0.06). Furthermore, findings indicated that the wrist angle had a more pronounced effect on the value of the perceived exertion (partial η2=0.31, P-value<0.001).