Journal of Health and Safety at Work

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Introduction: Heat stress is considered as a serious risk factor to the health and safety of workers in most working environments, especially in outdoor works and jobs that workers are exposed to heat due to the working process. This study aimed to evaluate heat stress among workers of brick-manufacturing units in Qom city based on WBGT index as well as the relationship between WBGT and physiological indicators.
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Material and Method: The present study was conducted in 40 brick-manufacturing units in Qom city. WBGT measurements were performed according to ISO7243 standard. Physiological responses of 184 workers (up to 5 people per unit) and also atmospheric parameters were measured. The physiological responses included oral temperature, skin temperature, and temperature for the carotid artery of the ear, heart rate, systolic and diastolic blood pressure. Statistical analysis was done using SPSS software version 16.
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Result: Mean WBGT index for various brick-manufacturing jobs including firing, manual material handling, working with conveyors, molding, and tempering were 30.8 °C, 26.74 °C 26.58 °C and 24.25 °C, respectively and the average WBGT was estimated 27.98 °C. WBGT levels measured in all units exceeded the level provided in ISO7243 standard. The highest mean WBGT was belonged to kiln section (30.8 °C). The mean WBGT at three heights of head, abdomen and legs were not statistically different (using t-test). The correlation coefficients between mean WBGT and mean oral, skin and ears temperatures were 0.203, 0.319, and 0.490, respectively, with the highest correlation belonged to the carotid arteries of ears. Moreover, WBGT showed no significant association with the mean heart rate, systolic, and diastolic blood pressure (P-value>0.05). Indoor and outdoor WBGT index was significantly different (P-value<0.05).

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Conclusion: The level of heat stress in all brick-manufacturing units was higher than the recommended limits, and the workers in kiln unit were more exposed to heat stress, in comparison with other units. Therefore, special countermeasures should be adopted to control heat stress for this occupational group.

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Introduction: Heat stress is one of the hazardous agents in the steel industries which can threaten the health and safety of workers and lead to serious occupational diseases. The aim of the study was to assess the heat stress in the steel industries and compare PHS (Physiological Strain Index), WBGT (Wet-Bulb Globe Temperature), DI (Discomfort Index) and HSI (Heat Stress Index) indices for the estimation of heat stress and to determine the optimum index for steel industries.
 

Material and Method: This descriptive-analytic study was conducted among 220 workers engaged in two steel industries in Iran. Environmental and physiological parameters were measured according to ISO 7726 and ISO 9886 in three times of measurement, and finally the time-weight average of the heat stress indices were calculated. All data were analyzed using SPSS ver.  20.
 

Result: The time-weight average of WBGT (28.28 oC), DI (29.11 oC), HIS (65.7 %) indices were higher than the recommended limits. Physiological parameters (oral, tympanic and skin temperatures, systolic and diastolic pressures and heart rate) had the greatest value in the second time of measurement (afternoon). WBGT index comparing to the PHS, DI and HSI indices had highest correlation with oral, tympanic and skin temperatures and heartbeat (r=0.314 , 0.408 , 0.459 , 0.302, respectively; P < 0.05), while systolic and diastolic blood pressures showed no significant correlation with WBGT (P > 0.05). The WBGT index had the highest correlation with studied indices which was 0.945, 0.681 and 0.600 for DI, PHS and HSI, respectively.
 

Conclusion: This study assessed the optimal index with regard to the physiological parameters, and it was concluded that the WBGT index has the highest correlation with the most of physiological parameters, and therefore, WBGT index can be the most optimum index to heat stress assessment   in the studied steal industries.

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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: 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.