Journal of Health and Safety at Work

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Introduction: Many studies, especially in recent years, have evaluated and controlled the occupational heat stress in Iran using environmental indices. However, so far, no comprehensive study has been conducted to review and classify these studies. Therefore, this study aimed to review and investigate the occupational studies performed by environmental heat stress indices in Iran.
Material and method:  In the present study, the published articles from 2000 to 2016 were searched using Persian and English keywords including heat stress, heat strain, hot condition, warm condition, occupational health, thermal environment and Iran. Search of articles was performed in databases such as Web of Science, Google Scholar, PubMed, Scopus, Science Direct, SID, Magiran, Civilica, Iran Medex, Barakatkns and Irandoc. In total, 323 articles were found and 134 articles of them, based on the exclusion criteria, were selected and included in this study. 
Results: Based on the results, most numbers of the studies, with 93.3 percent of the total researches related to published article, have been carried out between years of 2010 to 2016. As well as, most of studies with 61.9 percent were related to the indoor industrial environments. Most of studies were also performed in cities of Isfahan with 31.08 percent, Tehran with 16.89 percent, and Assaluyeh with 11.48 percent, respectively. As well as, WBGT index with 76 percent and the UTCI and PHS indices with 0.6 percent had the highest and lowest usage in all environments and industries, respectively. In addition, the results showed that WBGT index had most usage in industries of melting and casting with 15.7 percent, petroleum with 8.3 percent, and outdoor small occupations with 8.3 percent, respectively. Based on the results, the industries of the refinery, steel, glasswork, melting and casting, mines, and ship repairs have the highest mean values of WBGT index, respectively.
Conclusion: The results showed the need to more attention of researchers for conducting studies in outdoor environments, in different cities of Iran, on development and validation of novel heat stress indices, and on implementation and evaluation of control measures in the environments with high heat stress.

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Introduction: This study was designed with the main purpose of examining the compatibility of the two indicators of wet bulb globe temperature (WBGT) and predicted thermal strain (PHS) in assessing the environmental conditions and the heat load imposed on the subjects.
Method: In this cross-sectional study, 163 bakers were included in the study. Thermal stress was determined using the WBGT and PHS. At the same time, physiological responses of subjects were recorded, including tympanic temperature, heart rate and mean skin temperature. Finally, the predicted heat strain was evaluated and compared with actual values.
Results: Based on the results, the WBGT index is accompanied with an underestimation and PHS with  an overestimation, compared to the tympanic temperature. In addition, the WBGT index with the core temperature and the predicted rectal temperature component of the PHS index are the most consistent (kappa value of 0.614 and 0.66, respectively). While the Kappa value is between the amount of water lost and the WBGT index, it indicates a mismatch (Kappa = 0.339).
Conclusion: The prediction of heat strains only based on the PHS index cannot reflect the actual heat load on individuals in thermal environments such as bakeries and it is associated with an overestimation. On the other words, this indicator is more suitable for indoor thermal environments, with minimal variation in individual and environmental factors affecting thermal stress

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Introduction: Many studies have been carried out on the effects of heat stress on cognitive functions, but the results are contradictory. Therefore, this study was conducted to review the effect of heat stress on cognitive functions.
Material and method:  In this study, all English articles conducted on effect of heat stress on cognitive, perceptual, and psychomotor functions from 1970 to 2018 were reviewed. For this, articles with keywords such as heat strain, heat stress, cognitive function, memory, comprehension, psychomotor, reaction time, mental performance, mood, mental response, error, task performance, fatigue, alertness, hyperthermia, and heat exhaustion in the  Scopus, Web of Science, Science Direct, Pub Med, Springer, Wiley Online Library and ProQuest databases were searched. Out of 157 retrieved articles, 39 articles were finally reviewed according to the inclusion criteria.
Results: Out of 157 retrieved articles related to the topic, according to the inclusion criteria, 39 articles were finally considered for review. Among this articles, 9 (%23) articles were published before 2000 and 30 (%77) after 2000. Two articles were in athletes, four articles (%10.2) in workers, four articles (%10.2) in students, four articles (%10.2) in military soldiers and twenty-five articles (%64.2) were conducted in ordinary people.Based on the results, heat stress was identified as a detrimental factor for decreased cognitive functions such as reading comprehension, memory, focus, mathematical processing, tracking test, reaction time, perception  and decoding text and numeric messages, visual alertness, mental computing, text reading , hidden figures test and verbal fluency.
Conclusion: Based on the results of these studies, heat stress has been introduced as a detrimental factor for disrupting cognitive functions, but conclusion based on the results of studies is a systematic method is difficult because many confounding variables such as type of work, exposure time, skill and adaptation plays a big role.

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Introduction: Determining methods for assessing heat stress in different work environments is one of the major challenges for researchers in this field. The purpose of this study was to validate WBGT index and heat pressure assessment (HPA) by some physiological responses in Iranian South Oil Company.
Material and Methods: This descriptive-analytical study was carried out on 154 employees of Kharg, Asalouyeh and Mahshahr oil terminals recruited from three different working conditions including indoor, outdoor and rest environments in the summer. The amount of heat stress in the workplace was evaluated by WBGT index HPA method. To meet this purpose, the environmental parameters i.e., temperature, wet temperature, radiation temperature, relative humidity, water vapor pressure and air flow rate were determined. In addition to the direct reading method by the WBGT meter, ISO 7243 was used to calculate the WBGT index. In order to validate the heat stress indicators, physiological parameters of oral temperature, tympanic temperature and work metabolism were measured.
Results: The results of paired sample t-test showed a significant difference between WBGT index and HPA in indoor and outdoor environment (P<0.05). Moreover, there was a significant difference between the physiological indices of oral and tympanic temperatures and work metabolism in the indoor and outdoor environment (P<0.05). Furthermore, the correlation test was significant between WBGT index as an independent variable and HPA as a dependent variable (P<0.05)  and showed a high correlation (R2=0.914) between WBGT index with oral temperature and tympanic temperature . Also, the rate of work metabolism was significantly related with the aforementioned parameters (P<0.05) and was equal to R2=0.423, R2=0.335, R2=0.552, respectively. The correlations were also significant between HPA with Oral temperature, tympanic temperature and work metabolism (P<0.05)and were equal to R2=0.632, R2=0.605, R2=0.557, respectively. The results showed also that the correlation rate between the HPA with physiological parameters is stronger than that between physiological parameters with the WBGT index.
Conclusion: This study showed that WBGT and HPA methods are useful for assessing the heat stress of Iranian South Oil Company. Also, the HPA method is more reliable for assessing heat stress in these regions.

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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: Prevention of heat-related diseases requires the participation of the workers. For this reason, the aim of this study was the development and validation of the tools for evaluating awareness and practice related to heat stress among the workers of warm workplaces.
Material and Methods: The various items and factors related to the awareness and practice of the workers were identified by the literature review. Then, several questions for evaluating these items were designed. In the next step, the reliability and validity of the questionnaires were appraised using calculating the content validity ratio (CVR) and content validity index (CVI), and Cronbach’s alpha coefficient, respectively. After that, these questionnaires were completed by 2338 employees of six industries in various regions of Iran. Finally, collected data were analyzed using SPSS software.
Results: In total, 77 questions, including 53 questions on awareness and 24 questions on practice in six groups of water and beverages, food, snacks and additives, heat exchange, thermal strain risk factors, clothing and heat protection equipment, and heat-related disorders and body reactions, were designed. The values of content validity index (CVI) of remained questions in the questionnaires of awareness and practice were equal to 0.954 and 0.824, respectively. The values of Cronbach’s alpha coefficients of these questionnaires were calculated by 0.755 and 0.716, respectively. The values of the chi-square divided by degrees of freedom (CMIN/DF) and root mean square error of approximation (RMSEA) in the construction of the awareness questionnaire were computed as 4.58 and 0.079, respectively. These values in the construction of the practice questionnaire were calculated by 2.33 and 0.084, respectively.
Conclusion: The results showed that the designed questionnaires had appropriate reliability and validity and could be used to evaluate the awareness and practice in warm workplaces.

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Introduction: Numerous studies have been conducted on the development of modern insulators, including nano-insulators. However, a comprehensive study has yet to be performed to review and investigate the thermal properties of these insulators. Consequently, this study aimed to examine the effect of nanomaterials on thermal insulation function.
Material and Methods: In this review, articles were searched for in English databases (PubMed, Web of Science, and ScienceDirect), Persian databases (Magiran, SID), and Google Scholar. The keywords used in the search were Nano Material, Nano Insulation, Thermal Insulation, Thermal Insulator Stability, and Thermal Conductivity in both English and Persian.
Results: Of the 4068 studies identified through search databases, 15 were selected according to the entry criteria. Among the studies, the three types of silicone, composite, and aerogel insulation had the highest frequency (each 26.67%), and SiO2 nanoparticles were the most prevalent nanomaterial (26.67%). According to the studies, the type of nanomaterial used in insulation will improve its properties such as thermal resistance, mechanical strength, dielectric strength, tensile strength, elasticity, and hardness.
Conclusion: The results of this study showed that using nanotechnology could be an effective step in improving the properties of insulation materials, the most important of which is increased thermal resistance. Moreover, nanotechnology insulators can prevent thermal energy loss, reduce costs, and provide safety and comfort.

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Introduction: Many industries have multiple factors harmful to health, leading to simultaneous exposure of these factors to each other. Noise is one of the most common physical parameters in the work environment. On the other hand, heat is also increasing due to various energy processes in industries. Therefore, this study was conducted with the aim of determining changes in physiological parameters and visual-auditory attention in acute exposure to heat and noise.
Material and Methods: In this experimental study, 72 individuals (36 men and 36 women) aged between 23 and 33 years participated according to the inclusion criteria. In total, 12 different test modes were performed (3 temperature levels and 4 noise pressure levels). The test was conducted for each person in 4 steps during a specific day. The duration of exposure to each condition was half an hour, and a half-hour rest was given between each test condition. Saliva samples of each subject were collected before and immediately after exposure to noise and heat. Also, The Integrated Visual and Auditory (IVA) was recorded by the participants simultaneously.
Results: The results of combined exposure to noise and heat on visual and auditory attention showed that only two modes of combined exposure, SPL95+WBGT34 and SPL95+WBGT29, caused a significant increase (P < 0.05) in mental workload and a significant decrease (P < 0.05) in visual and auditory attention. In addition, the results showed that independent exposure to noise at the levels of 85 and 95 dB and exposure to heat at higher temperature levels of 34 and 29 degrees Celsius cause a significant increase (P < 0.05) in salivary cortisol after exposure. The results of the effect of combined exposure to noise and heat on salivary cortisol showed that three experimental modes of combined exposure (SPL85+WBGT34, SPL95+WBGT29, and SPL95+WBGT34) caused a noticeable and significant (P<0.001) increase in salivary cortisol.
Conclusion: Indeed, salivary cortisol can be recommended as a physiological index to evaluate noise and heat exposure. It’s also noteworthy that salivary cortisol is more affected by noise and heat exposure than cognitive performance.

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Introduction: Workers who work in warm situations need clothes with better thermal regulation. Nowadays, improving the thermal regulation properties of cotton fabric by treating it with phase change materials (PCMs) has been considered. The type of fabric plays an important role in providing thermal comfort. Cotton fabric is the most popular raw material in the textile industry due to its distinctive features. Therefore, this systematic review aims to investigate the effects of PCM nanoencapsulation in commonly used cotton fabrics, including morphology, thermal properties, thermal stability, tensile strength, abrasion resistance, leakage, water absorption, washing ability, and breathability of the fabric, related challenges, and future research trends.
Material and Methods: This research was conducted with the papers obtained from the systematic search in Science Direct, Web of Sciences, Scopus, and PubMed databases. Keywords “nanoencapsulated phase change materials”, “nanoenhanced phase change materials”, “cotton”, “cotton fabric”, and “cotton textiles” were used.
Results: Of the 1251 studies identified through search databases, 13 were selected according to the entry criteria. The results revealed that in all the studies, PCM nanocapsules were successfully synthesized and inserted into the cotton fabric, improving the fabric’s thermal properties. Most studies used in situ polymerization and mini-emulsion polymerization for nanoencapsulation. The pad-dry-cure method was also widely used for applying nanocapsules to cotton fabric.
Conclusion: This systematic review showed that synthesized nanocapsules of phase change materials and applied them to cotton fabric can improve the thermoregulating properties of the fabric. It is suggested to expand the research to design thermoregulating clothes made from treated fabrics and investigate their cooling performance.