Journal of Health and Safety at Work

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Introduction: Workers in open pit iron ore mines are exposed to heat stress which can cause health and safety problems. The purpose of this study was to evaluate heat stress among open-pit mine workers of iron ore based on Wet Bulb Globe Temperature (WBGT) index and also to investigate its relationship with physiological Strain.

Material and Method: This cross-sectional study was conducted on 120 healthy miners, working in an open-pit mine, during summer season, in 2014. Physiological parameters, including core body temperatures and heart rate, were measured according to ISO 9886 standard and physiological strain indices, including Physiological Strain Index (PSI) and Physiological Strain Index based on Heart Rate (PSIHR), were calculated using the equation. Environmental variables as well as physiological parameters were simultaneously measured and recorded during work shift. WBGT index was calculated according to ISO 7243 and using the equation. Statistical analysis was performed using the SPSS software version 22.  

Result: The mean WBGT index was estimated 29.09oC for workers. “Drilling” and “factory and Krasher” units showed the highest and lowest WBGT index values of 31.06oC and 29.05oC, respectively. Workers occupational exposure to heat stress were higher than recommended thresholds based on WBGT index in all work units. A statistically significant correlation was found between WBGT index and physiological strain indices
(P value<0.001). The Pearson’s correlation coefficients were obtained 0.658 and 0.566 respectively, between WBGT index and values of PSI and PSIHR.

Conclusion: WBGT index showed a higher correlation with physiological strain Index; and level of heat stress in all work units of mine was higher than recommended thresholds. Thus, countermeasures should be adopted to control heat stress for the workers in this field.

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Introduction: Occupational exposure to crystalline silica increases the risk of lung cancer and restrictive lung disease with extensive fibrosis. Silica dust is a major health hazard in foundry factories. The aim of this study was to determine core making workers’ exposure to respirable crystalline silica dust in a foundry factory.

Material and Method: This cross-sectional study was conducted in core-making unit of a foundry factory in 2015. Occupational exposure of 55 workers to respirable crystalline silica aerosols was evaluated by using the improved NIOSH7602 method in core-making unit. Risk assessments for silicosis and excess lifetime risk of mortality from lung cancer were done according to Manettej and Rice models, respectively. Data was analyzed with Spss19 software.

Result: The mean of respirable crystalline silica dust was 0.246 ± 0.351 (mg/m3). All  workers’ exposure to respirable crystalline silica was higher than recommended occupational exposure limits. Silicosis mortality risk and excess lifetime risk of mortality from lung cancer were estimated in the range of 6-63 and 65 per thousand people, respectively.

Conclusion: The mean of workers’ exposure to respirable crystalline silica was higher than recommended occupational exposure standards in core making unit. The risk assessment of silicosis mortality and excess lifetime risk of mortality from lung cancer were higher than acceptable levels of risk.

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Introduction: Resilience engineering is a novel approache to risk management and is the inherent ability of a system to adapt their work before, during and after the changes and adverse events in such a way that maintain the system performance under predictable and unpredictable conditions. The aim of this study was to identify indicators of organizational resilience of refineries and ranking them using fuzzy TOPSIS technique.  

Material and Method: A qualitative study was done to identify organizational resilience indicators of refinery complex. The main method of data collection was semi-structured interviews. Indicators were determined using qualitative content analysis and literature review. Weighting and ranking identified indicators was performed using fuzzy TOPSIS technique.   

Result: Eleven indicators were identified as follows: management commitment, performance management system, flow of information/communication, involvement culture, error management culture, education, preparedness, flexibility, innovation culture, change management, and human resource management.

Conclusion: Critical sociotechnical organizations especially refinery complexes in order to improve safety management and resilience situation should focus on effective indicators. Monitoring and improving them will increase safety and the resilience level of organization

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Introduction: Workers in open pit mines are frequently exposed to extreme heat stress during hot seasons. Several indices including Modified Discomfort Index (MDI) are used to evaluate the heat stress. The aim of this study was to evaluate the MDI and to investigate its relationship with ISO 7243 standard (Wet Bulb Globe Temperature index, WBGT) and physiological parameters of workers in an open pit mine.
 

Material and Method: This cross-sectional study was conducted among 120 healthy male miners in an open pit mine during summer season in 2014. Physiological parameters including body core and skin temperature, heart rate and blood pressure were measured according to ISO 9886 standard. All environmental and physiological parameters were simultaneously measured and recorded during a work shift. The MDI and WBGT indices were calculated using the related formula. Statistical analysis was performed using the SPSS 22 software.  
 

Result: According to the criteria of MDI, about 29 percent of workers had the average level, 68 percent of workers experienced the intense level and 2.5 percent suffered from the extreme level of exposure to the heat stress. No case of light level exposure to heat stress was obtained among workers. A significant correlation was found between MDI and ISO standard index (WBGT). Statistically significant correlation were also found between MDI and physiological parameters (P<0.001); in which the highest correlation coefficient was found for the heart rate variable (r=0.589).
 

Conclusion: Based on MDI, a high percentage of open pit mine workers were at risk of heat stress hazards. MDI had a moderate correlation with physiological parameters of the workers and showed a remarkable correlation with the WBGT.

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Introduction: Driving a train is one of the high demand job due to high vigilance task requiring the ability to long periods monitor surrounding environment and recognizing signals. The aim of this study was to assess train drivers’ mental workload using heart rate (HR) and heart rate variability (HRV) indices.
Material and Method: An experimental design was conducted among 12 well-trained subjects to induce two different levels of mental demands in a metro simulator and to monitor mental workload levels while driving the train. The HR and HRV parameters were recorded and analysis using ECG signals.
Result: The HRV parameters including SDNNIX (p-value=0.01), RMSSD (p-value=0.00), %PNN50 (p-value=0.01), SDNN (p-value=0.07) and LF/HF Ratio (p-value=0.04) were significantly reduced in a normal operation task comparing to the abnormal one.
Conclusion: The HR and HRV (SDNN, SDNNIX, RMSSD, %PNN50 and LF/HF Ratio) were found to be sensitive to mental workload in metro train driving .It is recommended to include the HRV parameters for mental workload assessment of train drivers.

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Introduction: Changing the national System of Classification and Labelling of Chemicals to Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is beneficial for all the industries of the countries, their workers and the general public. Increasing the awareness of chemical hazards, improving the safety uses, reducing chemical accidents, and providing better conditions for emergency response in the event of chemical accidents, are some of the most important benefits of the GHS. Present study aimed to develop a tool for assessing the awareness level of chemical related personnel using the GHS and current status.  
Material and Methods: By reviewing the literatures, the GHS Guide, available sources and consultation with experts, two questionnaires were developed to assess the level of awareness of chemical related personnel and current statue. The two designed questionnaires included personal information, multiple choice questions and questions related to safety signs. The face and content validity was conducted using the experts’ panel assessment. The face validity, content validity ratio (CVR) and content validity index (CVI) were all calculated for each question.
Results: Content Validity Ratios (CVR) and Content Validity Index (CVI) were calculated for each question. The general clarity, general fit and general simplicity of the awareness questionnaire (questionnaire number 1) were obtained 0.87, 0.91 and 0.77, respectively. The mean content validity index and the mean content validity ratio were obtained 0.85, 0.85, respectively. The overall clarity, overall fit, and the general simplicity of the current status questionnaire (questionnaire number 2) was 0.92, 0.89 and 0.93, respectively. The mean content validity index and mean content validity ratio were obtained 0.92 and 0.81, respectively.
Conclusion: The two questionnaires used to assess the awareness level of chemical related personnel and current statue of GHS, were identified as valid instruments and therefore is recommended as a valid tool for future studies.

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Introduction: Hydrogen sulfide (H2S) is a toxic gas that has adverse effects on human health and equipment. One of the methods for eliminating of H2S gas is the use of adsorbent substrate. In this study, the effect of adding iron oxides including ferric (Fe2O3) and magnetite (Fe3O4) nanoparticles to ZSM-5 zeolite substrate was investigated on the efficiency of H2S elimination from the air stream.
Methods: In this study, Fe2O3 and Fe3O4 nanoparticles were impregnated in ZSM-5 zeolite in two weight ratios of 3% and 5%. The structural properties of the substrate were studied using XRD, BET and SEM. Then, the efficiency of substrate in removing H2S from air was studied while H2S gas was injected in to a pilot setup, in concentrations of 30, 60, 90 and 120 ppm at three bed temperatures of 100, 200 and 300 o C.
Results: The accuracy of combination and the morphology of inoculated zeolite was confirmed using XRD and SEM. The BET test also showed that the loading of iron oxide nanoparticles on the substrate educed the substrate surface area. The results revealed that increasing the percentage of nanoparticles and increasing the temperature from 100 ° C to 300 ° C increase the time of breakthrough point. The maximum adsorption capacity was obtained equal to 44.449 (mgH2S/g zeolite) for ZSM-5/Fe3O4-5% substrate at 120 ppm concentration.
Conclusion: Iron oxide  nanoparticles  inoculated  in  ZSM-5  zeolite  substrate  increase  the  capability of eliminating of H2S gas at high temperatures and therefore can be used as a suitable method for the elimination of similar pollutants.

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Introduction: Commercial complexes are one of the most prestigious public and city-centered areas in terms of urban safety and passive defense. The purpose of this study was to determine the fire safety risk score of commercial complexes and its related factors.
Material and method:  The commercial complexes of area 1 of District 12 of Tehran were studied. The characteristics of the complexes, including construction, height, activity, Occupancy Coefficient and etc in each complex were collected. fire risk assessment was performed using NFPA101 standard and CFSES software in three areas of control, Egress and general safety. In SPSS software version 21, linear regression and ANOVA tests were used to determine the relationship between variables.
Results: Of the 79 commercial complexes studied, only 8 in control area and 4 in general area achieved acceptable risk level. None of them achieved an acceptable score in the Egress. According to the results, there was no significant relationship between risk levels and height, type and activity Coefficient of them(p>0.05). However, between Occupancy Coefficient of complexes with fire safety risk levels of control(p<0.001) and general(p= 0.013) and between construction with all risk levels ((p_Egress= 0.004), (p_Control & p_General<0.001)) There was a significant relationship.
Conclusion: The results showed the current situation of the studied commercial complexes is prone to cause a disaster in the 12th district of Tehran; Using the results of this study in urban planning and cross-sectoral communication to improve the safety of commercial complexes in the region is suggested.

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Introduction: Determining the size distribution of the particles for assessing their effects on human health and their control mechanisms is very effective. One of the most important equipment used in determining particle size distribution is the DMA. In this study, in addition to the design and construction of a DMA, the size distribution measurement of aerosol particles was carried out.
Material and Methods: In this experimental-laboratory study, according to the theoretical principles, the geometric dimensions and operating conditions of the DMA were determined by Fortran programs. The design of the technical drawing of the DMA was done using the Salidworks-2017 software. The DMA designing was performed by studying the size distribution of 12 ranges of DOP particles in 15 voltages.
Results: The results of applying different voltages to the DMA showed that one range of particles size had the highest number of particles in the output of the DMA at each voltage. As the number of particles with the size of 0.26-0.3 µm at 3500 volts and those larger than 2 µm at 9000 volts is the highest at the output of the DMA.
Conclusion: DMA systems are a robust tool in determining the particle size distribution. As by knowing the required voltage to separate a specific size of the particles, the DMA will be able to specify the spectrum of unknown particles.

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Introduction: The study of noise has always been of interest to occupational health professionals as a harmful physical factor in the workplace. However, the psychological and psychoacoustic aspects of noise in the workplace have been less studied. This study has dealt with different colors of noise and their applications in psychoacoustics.
Material and Methods: This review study was conducted by searching the databases of Google Scholar, ProQuest, Science Direct, PubMed, and Scopus to extract the articles related to the research subject within a 50-year interval from 1970 to 2020.
Results: Based on the results of the present study, colored noises and white noise seem to have the potential to be used as acoustic stimuli to improve the sleep of employees, especially shift workers, to improve memory and attention, especially in jobs that require high care and attention. Colored noise and white noise have potential applications to improve cognitive function in different occupations to reduce the activity of the sympathetic nervous system and anxiety and stress, especially in jobs with high job stress. Also, these noises are helpful for people’s privacy, especially in the open workplace, for noise masking and noise control purposes, as well as for medicine and treatment of disorders such as tinnitus, ADHD, and hyperacusis.
Conclusion: Paying attention to the colors of noise and their psychoacoustic impacts shows us that the noise impacts are not limited to their undesirable and damaging effects. Instead, their positive and applied aspects should also note. Familiarity with such aspects and their introduction can identify the existing information gaps in this field and pave the way to fill them.

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Introduction: Studies show that in many cases, environmental hazardous agents such as heat, noise, as well as chemical pollutants cause adverse health effects through the mechanism of oxidative stress. This study has examined the effect of exposure to noise and whole-body vibration (WBV) on some parameters of oxidative stress (enzyme superoxide dismutase (SOD), total antioxidant capacity (TAC), and malondialdehyde (MDA)) of workers in a foundry industry.
Material and Methods: The workers were selected based on the calculations related to the sample size and taking into account the inclusion criteria as well as completing the informed consent form. The level of exposure to noise and WBV was measured according to ISO 9612 and ISO 2631, respectively. For each worker, the time-weighted average was calculated. The level of exposure of workers to the studied stressors was divided into three categories: low, medium, and high. The blood samples were taken from all participants between 7-9 am. Then, via ELISA method according to the protocol of the kit manufacturer, the samples were prepared and analyzed. Univariate analysis of variance was performed to determine the “effect size” of each physical stressors on the studied parameters.
Results: The mean levels of MDA, SOD, and TAC among participants were 22.48 (11.19) nmol / ml, 61.28 (10.97) U / ml, and 1.64 (0.90) mM, respectively. Among the exposure variables, noise had the largest effect on MDA level (B = 0.090), which was not statistically significant (P = 0.865). WBV had the largest effect on SOD level (B = -1.469) which was statistically significant (P = 0.016). None of the studied variables had a significant effect on the TAC level; however, among the exposure variables, the greatest effect was related to WBV (B = -0.077; P = 0.133).
Conclusion: The effect of noise on oxidative stress parameters was not statistically significant. The effect of whole-body vibration on oxidative stress parameters except SOD was not statistically significant. Noise and WBV had increasing effect on MDA and decreasing one on SOD and TAC levels.