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Background: In both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift. Methods: This case–control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with α = 0.05. Results: The results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p

Background Noise is one of the most common harmful agents in the workplace. Exposure to excessive noise can lead to complications such as cardiovascular disorders, disturbance of body hormones’ rhythm and hearing loss. This study aimed at weighing and modelling factors influencing serum cortisol and melatonin concentrations of workers that are exposed to various sound pressure levels using neural network algorithm. Methodology A case-control design was adopted in the current research. The required data were collected from 75 industrial and mining firm staff members. They were assigned to three groups with equal sample sizes (25 workers). In developing the conceptual model in regard to variables that may affect workers’ serum cortisol and melatonin concentration, SPL, age, weight, and height were included. The influence of SPL on serum cortisol concentration as assessed in the three shifts. Moreover, radioimmunoassay (RIA) was utilized to assess serum cortisol and melatonin concentrations. Neural network algorithm was subsequently exploited to weigh and model predictor factors. IBM SPSS Modeler 18.0 was the software program used for data analysis. Results The average cortisol concentration values for administrative, condensing, and pelletizing units respectively were 10.24 ± 2.35, 12.15 ± 3.46, and 14.91 ± 4.16μgdl. On the other hand, the average melatonin concentration values for administrative, condensing, and pelletizing units respectively were 37 ± 12.52, 34 ± 13.15, and 27 ± 9.54μgdl. According to the results of the developed model for cortisol, SPL3 (32%) and age (5%) respectively had the highest and lowest impact. On the other hand, considering the model developed for melatonin, height (27%) and SPL1 (10%) were the most and least influential factors in that order. The accuracy rates of the model were also found to be 95% for cortisol and 97% for melatonin. Conclusion Comparing cortisol concentrations during various shifts revealed a significant reduction (from the beginning to the end of the shift) in all the three groups. Further, the rise of SPL would result in higher secretion of cortisol. Moreover, in all the three groups, the average serum melatonin concentration went up from the beginning to the middle of the shift and then declined to the end of the shift. Considering the accuracy rates of the models developed to predict hormones, neural network algorithm is a suitable and powerful tool for weighing and modelling factors influencing serum cortisol and melatonin concentrations., Industrial Engineering; Public Health; Software Engineering; Theoretical Computer Science; Acoustical Engineering; Safety engineering; Noise; modelling; cortisol; Melatonin; Neural network.

Background: Night shift work is associated with many problems such as sleep deprivation, sleepiness, decreased cognitive performance, increased human errors, and fatigue. This study set out to measure cognitive performance, melatonin rhythms, and sleep after different consecutive night shifts (7 vs. 4) among control room operators (CORs). Methods: The participants included 60 CORs with a mean age of 30.2 years (standard deviation, 2.0) from a petrochemical complex located in Southern Iran. Cognitive performance was assessed using the n-back task and continuous performance test. To evaluate melatonin, saliva was collected and tested by enzyme-linked immunosorbent assay. To assess sleep and sleepiness, the Pittsburgh Sleep Quality Index and Karolinska Sleepiness Scale were used, respectively. Results: Individuals who worked 7 consecutive night shifts had a significantly better cognitive performance and sleep quality than those who worked 4 consecutive night shifts. However, salivary melatonin profile and sleepiness trend were not affected by shift type. Conclusion: The main duty of CORs working night shifts at the studied industry included managing safety-critical processes through complex displays; a responsibility that demands good cognitive performance and alertness. It is suggested that an appropriate number of consecutive night shifts in a rotating shift system should be planned with the ultimate aim of improving CROs performance/alertness and enhancing safety. Keywords: melatonin, night shifts, performance, sleepiness

Background: Fire service workers often implement multiple duties in the emergency conditions, with such duties being mostly conducted in various ambient temperatures. Methods: The aim of the current study was to assess the firefighters' physiological responses, information processing, and working memory prior to and following simulated firefighting activities in three different hot environments. Seventeen healthy male firefighters performed simulated firefighting tasks in three separate conditions, namely (1) low heat (LH; 29â31°C, 55â60% relative humidity), (2) moderate heat (MH; 32â34°C, 55â60% relative humidity), and (3) severe heat (SH; 35â37°C, 55â60% relative humidity). It took about 45â50 minutes for each firefighter to finish all defined firefighting activities and the paced auditory serial addition test (PASAT). Results: At the end of all the three experimental conditions, heart rate (HR) and tympanic temperature (TT) increased, while PASAT scores as a measure of information processing performance decreased relative to baseline. HR and TT were significantly higher at the end of the experiment in the SH (159.41±4.25 beats/min; 38.22±0.10°C) compared with the MH (156.59±3.77 beats/min; 38.20±0.10°C) and LH (154.24±4.67 beats/min; 38.17±0.10°C) conditions (p0.05). Nonetheless, there was a measurable difference in PASAT scores between LH and SH (p

Firefighters perform various tasks during firefighting operations under unknown and unpredictable conditions. The present study investigated the impact of firefighting activities and cooling tactics on information processing and work performance. Firefighters performed typical firefighting tasks in the four experimental conditions, namely i) no cooling device (NC), ii) cooling gel (CG), iii) cool vest (CV), and iv) cooling gel and cool vest (CG + CV). The measurement of information processing, Paced Auditory Serial Addition Test (PASAT) scores decreased significantly after the firefighting activities in the four conditions, relative to baseline. The results revealed no significant difference in PASAT scores among the four conditions. However, the performance time (PT) was significantly shorter for the CV and CG + CV compared to the NC and CG conditions. The findings confirmed that the firefighting activities have a detrimental effect on information processing. The CG + CV and CV were more effective than CG and NC in improving PT during firefighting. However, the cooling strategies have a negligible effect on improving information processing performance.

Background: Firefighters often perform multiple emergency tasks during firefighting and life-saving operations under unknown and unpredictable conditions in hot and hostile environments. Therefore, this study examined the effect of cooling strategies on attenuating physiological and cognitive function response during simulated firefighting activities in a smoke-diving room. Methods: Each firefighter engaged in four conditions: namely (1) no cooling device; control (NC), (2) cooling gel containing menthol (CG), (3) cool vest (CV), and (4) cooling gel and cool vest (CG+CV). Cooling effects were evaluated by heart rate (HR), temporal temperature (TT), reaction time (RT), and the correct response (CR). Results: In the four experimental conditions, physiological response increased, reaction time improved, and correct response decreased after the activity relative to baseline. HR and TT were significantly lower at the end of the firefighting activity in the CG+CV (147.47 ± 4.8_bpm; 37.88 ± 0.20_○C) and CV (147.53 ± 4.67_bpm; 37.90 ± 0.22_○C) compared with the CG (153.67 ± 4.82_bpm; 38.10 ± 0.22_○C) and NC (154.4 ± 4.91_bpm; 38.11 ± 0.23_○C) conditions. RT and CR were significantly higher at the end of the activity in the CG+CV and CV compared with the CG and NC conditions. Conclusion: It is concluded that strenuous firefighting tasks have a detrimental effect on firefighters’ physiological responses and cognitive function. The findings also revealed that CV was more effective than the CG in attenuating physiological responses and cognitive function during firefighting operations. Furthermore, combining CV with CG provides no additional benefit. It is concluded that cooling the body by the use of CV offered physiological and psychological benefit for firefighters during simulated firefighting activities.

Introduction: Increasing population, the need for services, and industrialization of societies have led to a growing demand for shift work. Shiftwork causes several disorders, and determining the weight of each disorders is important for their prevention and treatment. Therefore, the purpose of the present study was to use Analytic Network Process (ANP) to prioritize and weigh shift work disorders among the personnel of hospitals of Kerman University of Medical Sciences. Methods: This cross-sectional, descriptive-analytical study was conducted in 2017 among 300 shift work personnel of 10 public hospitals affiliated with Kerman University of Medical Sciences. ANP was used to prioritize and weigh shift work disorders. To this end, the criteria, sub-criteria, and alternatives were initially identified. Then, shift work disorders were categorized into 7 general criteria, 20 sub-criteria, and 3 alternatives. After designing the ANP and determining the effect of each criterion on the sub-criteria, the ANP questionnaire was developed and administered among the shift work personnel, who filled it out based on ANP. Super Decisions was subsequently used to weigh and prioritize shift work disorders. Results: The results indicated that shift work disorders among the nurses included sleep disorders (0.297), psychological disorders (0.275), digestive disorders (0.137), personal life disorders (0.122), etc., in that order of weighing. With respect to the support staff, the major shift work disorders involved sleep disorders (0.252), digestive disorders (0.198), personal life disorders (0.168), and psychological disorders (0.164). Considering security personnel, the top four shift work disorders were sleep disorders (0.201), digestive disorders (0.186), psychological disorders (0.174), and personal life disorders (0.145). Conclusion: According to the findings, sleep disorders had the highest weight in the three studied groups. Moreover, the night shift had the most profound effect on shift work disorders among the personnel in the three groups. It was followed by the evening shift. Morning shift had the lowest influence on shift work disorders. Therefore, the schedules should be taken to prevent these complications in the shift workers. It is suggested that work shift complications be included in the periodic examination program and, in case of discovery of any rhythmic disorder in each shift workers, the person should not remain in the shiftwork group for some time.

Introduction: A two-shift work schedule with different rotations is common among firefighters in Iranian petrochemical companies. This study compared salivary melatonin and sleepiness on the last night before turning to day shift at 19:00, 23:00, 3:00, and 7:00 among petrochemical firefighters (PFFs) working seven and four consecutive night shifts. Methods: Sixty four PFFs working in the petrochemical industry were selected. To measure melatonin, saliva samples were taken, whereas the KSS index was used to assess sleepiness. Chi-square and independent samples t-test were carried out to analyze the data, and generalized linear model (GLM) was employed to determine the effect of confounding factors such as lighting and caffeine. Results: The levels of melatonin at 3:00 and 7:00, and the overall changes during the shift in the two shift patterns under the study were different (P < 0.05). Sleepiness was significantly different only at 3:00 in the two studied shift patterns, while the effects of lighting and caffeine on melatonin changes were not significant (P > 0.05). Conclusion: It seems that a slow shift rotation is better because it reduces the secretion of melatonin (hence reducing sleepiness during the night) and changes the peak of melatonin secretion to the daytime, which is a sign of adaptation.

Background Because of their positive impact on individuals’ performance and alertness, blue enriched white light sources are gaining popularity in households and industries. However, these sources of blue light spectrum may cause oxidative stress. On the other hand, there are no empirical studies investigating the negative effect of blue enriched white light on oxidative stress. Thus, the current study aimed at empirical assessment of the effect of such light sources on oxidative stress among night shift workers. Methods The study, which adopted a cross-sectional design, focused on 30 control room operators of a petrochemical complex. The subjects followed a shift-work schedule comprising 7 night shifts, 7 day shifts, and 7 days off. The subjects were exposed to 6500 K, 3000 K, and 17,000 K light sources (which have various degrees of blue light) during three consecutive work cycles, with each cycle lasting for 7 nights. In each light condition, three salivary measurements were conducted (at the beginning, in the middle, and at the end of the shift). The measurements were used to assess catalase (CAT), total thiol molecules (TTG), and total antioxidant capacity (TAC), and melatonin. Results The results of repeated measures ANOVA showed that there was no significant difference among various light conditions with regard to salivary biomarkers (catalase, total thiol molecules, and total antioxidant capacity). There was however a significant difference between 3000 K and 17,000 K conditions with regard to the concentration of salivary melatonin (p = 0.001). Conclusion Given that there was no significant difference among various light conditions in terms of biomarkers, it is concluded that using sources of light with high color temperature can be recommended. Nonetheless, because of the limitations of the present study (e.g. short period of intervention), it is suggested that care should be exercised in using such light sources.

This study examined the impact of various types of firefighting activities on firefighters' physiological responses and cognitive function. Each firefighter was engaged in three conditions: (1) Live-fire activities (LFA), (2) Typical firefighting activities (TFA), and (3) Rescue operations at height (ROH). The effects of various types of firefighting activities on the physiological responses and cognitive function were evaluated by heart rate (HR), temporal artery temperature (TT), and the correct response (CR) on a cognitive test. The results indicated that, compared to the baseline, physiological response increased, while information processing performance decreased after the activity. Furthermore, HR and TT were significantly lower at the end of the firefighting activity in the LFA (149.33 bpm; 38.08 °C) compared with the TFA (152.22 bpm; 38.17 °C) and ROH (159.28 bpm; 38.24 °C) conditions. Also, CR was significantly higher at the end of the activity in the LFA and TFA compared with the ROH condition. The results showed that rescue at height was more intensive than the other firefighting tasks in decreasing physiological and cognitive function capacity after the experiment. Practitioner Summary: We assumed that various types of firefighting activities would have different effects on physiological and cognitive functions during firefighting activities. The Findings suggest that rescue at height operations, performed without the use of special protective equipment, was more influential than other firefighting duties in changing firefighters' physiological and cognitive capacity. Abbreviations: CR: correct response; LFA: live-fire activities; TFA: typical firefighting activities; ROH: rescue operations at height; HR: heart rate; TT: temporal artery tempearture; PASAT: pased auditory serila addition teat; FPC: firefighting protective clothing.

This study investigated the combined effect of firefighting operations and exposure to smoke on physiological responses, cognitive functions and physical performance among firefighters. Each firefighter was engaged in two experimental conditions: (a) without artificial smoke, control (NS); (b) with artificial smoke (WS). The results of data analysis revealed that heart rate and body temperature increased significantly after the firefighting activities in the two conditions relative to baseline. In addition, reaction time (RT) and correct response (CR) decreased after the activity relative to baseline and there was a significant difference in RT and CR between the NS and WS conditions. There was also a significant difference in performance time between the NS and WS conditions. These findings demonstrated that a smoke compound has an insignificant effect on physiological responses during firefighting activity. On the contrary, the smoke compound has a detrimental influence on cognitive and physical performance.

"Mental workload refers to the amount of effort put in by the mind during the accomplishment of a duty. It essentially has to do with individuals’ mental capacity and the way they receive and process information in order to make decisions and take appropriate actions. The present study aimed at investigating the relationship between mental workload and prevalence of musculoskeletal disorders among welders of Tehran Heavy Metal Structures Company. This cross-sectional descriptive study was conducted in 2016. The sample included 100 welders working at Tehran Heavy Metal Structures Company. Sampling was done by census method. A demographic features questionnaire, NASA-TLX workload questionnaire, and Nordic Questionnaire were used for data collection. Data were analyzed by the use of SPSS (Version 22). Various data analysis procedures, including independent samples t-test, Pearson correlation, chi-square, and Fisher’s exact test, were employed. The mean of participants’ overall score in mental workload was 65.88 ± 21.15. Eighty four percent of the studied welders reported that they had experienced musculoskeletal disorders during the past 12 months (leading to the study), with the highest prevalence being recorded for waist (65%). Furthermore, the results of Pearson correlation indicated that there was a significant relationship between the prevalence of disorders in the legs and physical demand (P = 0.032). Also, a considerable association was observed between disorders in the wrist / hand and overall NASA mental workload score during the past 12 months (P = 0.021). Mental workload and the prevalence of musculoskeletal disorders are relatively high among welders. Waist was the most important risk factor among the participants studied. Future studies should attempt to detect risk factors that cause such disorders and suggest ways to reduce or prevent these problems among welders as much as possible."