Development and validation of an environmental heat strain risk assessment (EHSRA) index using structural equation modeling based on empirical relations

BACKGROUND@#Need to a simple, available, accurate, comprehensive, and valid indicator is felt to assess thermal effects. Therefore, the present study was aimed to develop and validate the environmental heat strain risk assessment (EHSRA) index using structural equation modeling (SEM) based on empirical relations.@*METHODS@#This cross-sectional study was performed on 201 male workers in environments with various climatic conditions. The heart rate and tympanic temperature of the individuals were monitored at times of 30, 60, and 90 min after beginning the work. At these times, values of dry temperature, wet temperature, globe temperature, and air velocity were also measured and metabolism rate and clothing thermal insulation value were estimated. At the end, a theoretical model was depicted in AMOS software and obtained coefficients were applied to develop a novel index. The scores of this indicator were categorized into four risk levels via ROC curves and validate using linear regression analysis.@*RESULTS@#Indirect effect coefficients of the globe temperature, dry temperature, wet temperature, air velocity, metabolism, and clothing thermal insulation variables on the tympanic temperature were computed by 0.77, 0.75, 0.69, 0.24, 0.49, and 0.39, respectively. These coefficients were applied to develop the index. Optimal cut-off points of boundaries between risk levels included 12.02, 15.88, and 17.56. The results showed that the EHSRA index justified 75% of the variations of the tympanic temperature (R@*CONCLUSIONS@#The novel index possesses appropriate validity. It was suggested that this indicator is applied and validated in various environments in the next studies.

Investigation of heat stress and heat strain in outdoor workers: a case study in Iran

Heat stress is an important and serious threat at work and is a particular concern in outdoor occupational environments. This study aims at comparing heat stress and heat strain at different outdoor groups, examining the protective and adaptive actions which were done by workers and also provi services to them by government or employer to reduce heat load. This cross-sectional study was conducted in the hottest days of the summer 2015 in Shabestar, Iran and 53 healthy men in nine occupational groups including concrete makers, porters, construction, waste site and road making workers, stonemasons, farmers, traffic officers, and street vendors participated. A set of physiological parameters, like heart rate, blood pressure, skin temperature and etc., WBGT index details and some of the adaptive and protective parameters were measured and monitored simultaneously at different times of the day. The study finds that heat exposure in outdoor workplace is prevalent and WBGT TWA/TLVave is less than 1 in some groups like stonemasons, waste site workers, traffic officers and street vendors whereas in other studied occupations, it is more than 1.This matter is compounded by the fact that the provision of health services by employers or local government was limited, and almost all of the participants had poor or insufficient access levels to public health and welfare services. This study confirms the necessity of interventions by a range of factors, such as government plans, improvement of services in the prevention of heat stress, and planning training courses for outdoor workers to build their knowledge of heat stress

passive noise control approach utilizing air gaps with fibrous materials in the textile industry

Noise pollution is currently a major risk factor in industries in both developed and developing countries.The present study assessed noise pollution in the knitting industry in Iran in 2009 and presented a control method to reduce the rate of noise generation. The overall noise level was estimated using the network environmental noise as-sessment method in Sina Poud textile mill in Hamadan. Then, frequency analysis was per-formed at indicator target stations in the linear network. Finally, a suitable absorbent was rec-ommended for the ceilings, walls, and aerial panels at three phases according to the results found for the sound source and destination environment. The results showed that the highest sound pressure level was 98.5 dB and the lowest was 95.1 dB. The dominant frequency for the industry was 500 Hz. The highest and lowest sound suppression was achieved by intervention at 4000 Hz equivalent to 14.6 dB and 250 Hz in the textile industry. When noise control at the source is not available or insufficient because of the wide distribution of the acoustic field in the workplace, the best option is to increase the absorp-tive surface of the workplace using adsorbents such as polystyrene.

Heat stress level among construction workers

The purpose of this study was to determine the level of heat stress to construction workers using Thermal Work Limit [TWL] and Wet Bulb Globe Temperature [WBGT] indices and by measuring Urine Specific Gravity [USG] among construction workers in Iran and comparing the appropriateness of these indices for measuring heat stress in Iran climate. This comparative and experimental study was conducted during September 2012 in Baghe Ketabe Tehran, one of the large size construction sites in Tehran City, Iran. Sixty participants were randomly selected in two groups [exposed to sun and non-exposed] among the construction workers in a construction campus with similar work type, climate and diet. TWL and WBGT and USG were measured in two consequent days and at the beginning, mid and end of the work shift, for both groups. The mean WBGT index was 22.6 +/- 0.9°C for control group and 27.5 +/- 1.2°C for exposure group, the mean TWL index measure was 215.8 +/- 5.2 W/ m[2] for control group and 144 +/- 9.8 W/ m[2] for exposure group and the mean USG was 1.0213 +/- 0.0054 in control group and 1.026 +/- 0.005 in exposure group. There was a significant difference in TWL, WBGT and USG between exposed and non-exposed group [P<0.01]. Workers were at an allowed level of heat stress. TWL, WBGT and USG measures were significantly correlated; however as TWL level enabled classification based on required intervention, it had some merit over WBGT index

Assessment and control design for steam vent noise in an oil refinery

Noise is one of the most important harmful agents in work environment. Noise pollution in oil refinery industries is related to workers' health. This study aimed to determine the overall noise pollution of an oil refinery operation and its frequency analysis to determine the control plan for a vent noise in these industries. This experimental study performed in control unit of Tehran Oil Refinery in 2008. To determine the noise distributions, environmental noise measurements were carried out by lattice method according to basic information and technical process. The sound pressure level and frequency distribution was measured for each study sources subject separately was performed individually. According to the vent's specification, the measured steam noise characteristics reviewed and compared to the theoretical results of steam noise estimation. Eventually, a double expansion muffler was designed. Data analysis and graphical design were carried out using Excel software. The results of environmental noise measurements indicated that the level of sound pressure was above the national permitted level [85 dB [A]]. The Mean level of sound pressure of the studied steam jet was 90.3 dB [L]. The results of noise frequency analysis for the steam vents showed that the dominant frequency was 4000 Hz. To obtain 17 dB noise reductions, a double chamber aluminum muffler with 500 mm length and 200 mm diameter consisting pipe drilled was designed. The characteristics of steam vent noise were separated from other sources, a double expansion muffler was designed using a new method based on the level of steam noise, and principle sound frequency, a double expansion muffler was designed

Evaluation of noise propagation characteristics of compressors in Tehran oil refinery center and presenting control methods

The adverse effects of noise are well known and noise problems due to industrialization of communities are increasing over the time. Oil industries due to the process and nature of production; contain many noise sources such as compressors, turbines, and pumps, which cause excessive noise exposure. The objective of this study was to evaluate the noise characteristics of compressors in Tehran Oil Refinery and study on visible control measures. To get to the appropriate control method, procedures such as basic theories, measuring sound parameters, frequency analysis, related diagrams and noise propagation schemes due to the measurement results, equivalent noise exposure level [L[eq[8h]]] and exposure noise dose and technical specification of compressors are considered in this paper. Considering field and analytical results, module enclosure with particular specifications [like absorbent layer, specific wall, window and door design etc.] is predicted to be the best control method. Calculation results of multiple layer density of the enclosure [W=16.5 kg/m[2]] and needed density for the dominant frequency of the source [W=12 kg/m[2]] demonstrated that the designed enclosure satisfies the goal. Results of designing sandwich layers' module demonstrated that installing the designed enclosure causes 20 dB[A] reduction in total sound pressure level of the source's dominant frequency