The Assessment of Heat stress in the employees of the confectionery workshops based on WBGT and DI Indexes (A case study of Ilam city)

Background and Objective: Inappropriate atmospheric conditions are harmful factors that cause particular problems in certain seasons (summer or winter). The occupation of confectionery in the regions like Ilam causes severe problems due to the heat generated by the nature of the work (synthetic heat-generating processes) and the heat resulting from the climatic conditions in the region. Exposure to excessive heat, in addition to disrupting the physiology and health of the individuals that may cause many diseases and complications, also affects their efficiency and safety. One of the indices of heat stress is the WBGT index, confirmed by various national and international organizations and institutions as the standard method for measuring heat stress. WBGT index engages important environmental factors directly or indirectly in its computational structure. The Discomfort Index (DI) has been recommended for more than four decades along with the WBGT index for the evaluation of warm environments. Today, the oral temperature is used to determine the heat stress and strain. In addition, oral temperature is one of the important parameters for the validation of indices. Therefore, in order to prevent the occurrence of heat stress complications in occupational environments, a study was conducted to determine the amount of heat stress in the employees of confectionery workshops in Ilam city, so as to identify the factors affecting the heat stress of workers and to provide recommendations for the reduction of these risk factors and to create a healthy working environment. Methods: This descriptive-analytical study was carried out on 104 workers in 35 confectionary workshops in summer of 2017. The sample size was selected based on census method. Prior to the study, the workers were monitored through medical records and interviews, and, two of them did not qualify for inclusion in the study. Measurement of the study variables was performed at the hottest work hours (10 to 14), once for each worker, in the worst workstation (nearest to the heat source). In the present study, four groups of occupations, i.e. workers of oven, mixer, flattener, cleaning and packaging, three types of ovens, i.e. layered, winch and furnace, and three productions of wet and dry pastry, cake and French bread, Baghlava and Ka’ak. Assessment of heat stress was performed by the WBGT (based on ISO7243 standard) and the DI indices. Metabolism and activity of workers were calculated according to the ACGIH standard. Also, the working pattern was 75% of the work-25% of the rest, and according to ISO 9920, the clothing insulation coefficient in WBGT calculations was 0.6 clo. Along with the environmental parameters such as dry bulb temperature, natural wet bulb temperature, globe bulb temperature, relative humidity and dew point temperature, the oral temperature of the workers was measured by a digital medical thermometer. Finally, data analysis was performed using SPSS v.22 and statistical tests of Kolmogorov-Smirnov, Mann-Whitney, Kruskal-Wallis, one-way ANOVA and Pearson correlation were performed. Results: Findings of this study showed that the mean of WBGT index in the workers of oven, mixer, flattener, cleaning and packaging was 33.66±3.96, 29.58±3.05, 31.73±3.61 and 29.87±2.4. Also, this index was 30.94±3.86, 34.14±3.89, and 32.2±2.91 for the winch (wet and dry pastry), layered (cake and French bread), and furnace (Baghlava and Ka’ak) ovens (products). These results show that the amount of heat stress in working with the oven and the cake and French bread product (layered oven) was more than others. Kruskal Wallis tests and one way ANOVA showed a significant difference between the mean of WBGT and DI indices with job variables, type of oven and products (p <0.05). A 95% confidence interval was observed in terms of the WBGT index between the subgroups of the oven and flattener, oven and cleaning and packing, layered oven and winch oven, and French bread and the wet and dry pastry. However, in terms of the DI index, this difference was found between the sub-groups of the oven and cleaning and packing, oven and mixer with flattener, layered oven and winch oven, and French bread and the wet and dry pastry. Pearson correlation test showed that there was no significant correlation between oral temperature and indices and variables (p<0.05). Based on the results of this study, the mean of WBGT index at the heights of head, waist and ankle was 32.54±5.01, 31.54±3.86 and 30.49±3.12, respectively. Also, according to Kruskal Wallis statistical tests and one way ANOVA, there was a significant difference in WBGT index and dry bulb temperature, natural wet bulb temperature, globe bulb temperature and relative humidity at the heights of head, waist and ankle (P <0.05). The results of the Mann-Whitney test indicated that there was a significant difference between the gender variable and the oral temperature (p <0.05), with the mean of this variable was higher in women (36.7±0.27) than men (36.42±0.84). The results of this study showed that 85.6% of the subjects had a “severe” discomfort index (DI), and regarding the WBGT index, 14.4% and 85.6% were lower and higher than the threshold, respectively. Conclusion: According to the results, almost all of the workers in the confectionary workshops are exposed to heat stress, but subgroups of oven, mixer, layered oven (cake and French bread), furnace oven (Baghlava and Ka’ak) and the females were exposed to higher stress. So, these subjects have a priority when adopting control measures. It is recommended that measures such as pre-employment examinations, preparation of proper drinks, training the workers, reduction of working time, using thermal shields, using air conditioning system, and paying particular attention to reducing the wet temperature and relative humidity of the workplace are taken to minimize the exposure to heat and the resulting diseases.