Journal of Health and Safety at Work

Introduction: Occupational exposure to manganese can cause neurobehavioral symptoms. The aim of present study was to survey neurobehavioral symptoms of welders exposed to manganese- containing welding fumes and compare the frequency of these symptoms with unexposed group.

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Material and Method: Twenty seven of welders as exposed group, and 30 administrative workers as unexposed controls, were participated in this study. Neurobehavioral symptoms data were gathered using Q16 questionnaire. Manganese concentrations were determined according to the NIOSH 7300 method. After preparing of blood samples using microwave assisted acid digestion method, all samples were analyzed to determine manganese by graphite furnace- atomic absorption spectroscopy (GF-AAS).

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Result: The mean exposure to air manganese was 0.023± 0.012 mg/m3. Manganese concentrations in blood samples of welders (15.88± 7.11 µg/l) were significantly higher than unexposed workers (9.37± 8.70 µg/l), (P-V<0.05). The frequency of neurobehavioral symptoms of welders was significantly higher compared to unexposed workers (P-V<0.05). The correlation between neurobehavioral symptoms and blood manganese was significant for welders (P-V<0.05).

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Conclusion: Welders’ exposure to manganese and its potential health effects should be evaluated periodically and effective control measures should be applied in order to to prevent neurobehavioral symptoms.

Introduction: Human and environment exposed to harmful factors, as the result of industrial pollutants. Volatile organic compounds (VOCs) play important role in photochemical reactions in troposphere layer of atmosphere and results in production of ozone and photochemical oxidants.

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Material and Method: In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing xylene. In the next step, the bioreactor incubated with microbial consortiums with ratio of 1 to 3. The performance of bioreactor in treatment of xylene vapors in presence of 10% silicone oil, as an organic phase was assessed in concentrations ranging from 551 mg/m3 to 3330 mg/m3 for 432 hours.

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Result: The results of xylene biodegradation showed that removal efficiency up to the concentrations of 2756 mg/m3 was 82 percent. Moreover, adding 10% silicone oil increased removal efficiency of BTX by 85.7% in comparison with context without organic phase. The microbiological experiments on the bioreactor media showed that three spices of Pseudomonas putida, Chryseobacterium and Ralstonia pickettii were found, in the presence of xylene.

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Conclusion: Overall, the results of the present research revealed that application of two phase stirred tank bioreactors (TPPBs) for xylene from contaminated treatment of streams was successful.

Introduction: Pollutants in gas turbine air intake can cause erosion ،corrosion، fouling as well as reduction of power and efficiency of turbine and noticeable economic losses. In order to select the appropriate filtration system, air monitoring of turbine inlet and its filtration is essential. Therefore, this study was performed to assess the quality of gas turbines inlets in a gas power plant in Tehran.

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Material and Method: In this cross- sectional study, the concentration of particulates contained in air intake of 4 types of gas turbines, including: Fiat, Assec, Hitachi and mitsubishi were evaluated in second-half of spring season. For this means, 12 series of air samples were collected using 8 stages cascade Impactor, model AN -200 made by OGAWA company on cellulose – ester filters . The dust concentrations were determined gravimetrically in different ranges of sizes . Then the concentrations of 8 metals including Sodium, Potassiumu Lead, Mercury, Aluminum ,Copper and Cadmium were measured using ,Atomic Absorption Spectroscopy method and the data were statistically analyzed by SPSS Software, version16.

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Results: The results showed that the mean of particulate concentration with the diameter less than 4.7 µ were 64% ,66% ,60% ,67% for Fiat, Assec, Hitachi, mitsubishi respectively and it was 64.25% totally. The concentrations of all assessed metals in particulates less than 4.7 µ were greater than of larger than 5 µ. There were not any differences between particulate concentration in the inlet of Fiat and Hitachi (P>0.05), while in the case of other gas turbine intakes , there were statistically significant differences (P<0.05).

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Conclusion: Based on mass distribution of particles, the highest concentration belongs to particles with diameter of less than 4.7 µ. These particles could damage turbine blades, especially due to the presence of sodium and potassium as corrosive elements in this range (200 µg/m3). Therefore,this range of particle size must be considered in selecting the air intake filtration system.

Introduction: In real Conditions, pollution emission are mostly released as mixed components rather than a single pure emission of the chemicals. In this study, a miniature stirred tank bioreactor was optimized for treatment of waste gas containing BTX (benzene, toluene and xylene).

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Material and Method: The sludge of an oil refinery was sampled based on the assumption that it contains BTX-degrading microorganisms and used as microbial consortium. Also, silicone oil was added to improve removal efficiency. The operational parameters of the bioreactor were optimized during the study.

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Result: The removal efficiency and elimination capacity of benzene, toluene and xylene vapors simultaneously in the presence of 10% silicone oil as an organic phase showed increasing trend up to the concentrations of 1730 mg/m3, 1710 mg/m3 and 1380 mg/m3, respectively. In these concentrations the removal efficiency and elimination capacity of benzene were 100% and 59 g/m3/h, toluene 100% and 58 g/m3/h and xylene 91% and 42 g/m3/h, respectively. The total removal efficiency and elimination capacity for BTX were 91 to 100% and 159 g/m3/h, respectively.

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Conclusion: It was shown that presence of 10% silicone oil increased 44.5% in total removal efficiency of BTX. The microbiological experiments on the bioreactor media showed that three spices of Pseudomonas putida, Chryseobacterium and Ralstonia pickettii can be found, when BTX ware treated. This work revealed that two phase partition bioreactors (TPPBs) can be successful method for the treatment of streams contaminated with BTX.

Introduction: Individuals’ jobs performance is one the most important factors in industries and organizations. The aim of the present study was to investigate the simultaneous effect of exposure to noise, lighting and heat stress on the workers’ job performance.
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Material and Method: In this analytical-descriptive study, 30 employees of the auto parts manufacturer, in Tehran city, were chosen by simple random sampling. By controlling and limiting confounding factors, the simultaneous effect of noise, lighting and heat stress on the participants’ job performance was investigated, using tow series of mental and manual testes. Data were analyzed by SPSS software version 18, using descriptive statistic, ANOVA and Tukey testes and also person correlation coefficient.
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Result: The results showed that by increasing the noise and heat stress (P = 0.046, r=0.344) and decreasing of lighting (P =0.008, r = -0.472), the required time for performing the Minnesota placement test has been gone up. Moreover, the result revealed that by increase in noise and heat stress (P = 0.007, r = 0.478) and decrease in lighting (P=0.003, r = 0.523) the required time for competing hand tool dexterity test has been also increased at surface and mid level.
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Conclusion: Finding of the present research manifested that increase in noise and heat stress and also reduction in lighting lessen the speed of manual tests and time and accuracy of mathematical calculations. Therefore this result confirm the effects of various environmental factors on individuals’ job performance, in a way that by variation of different environmental factors, time of manual test and time and accuracy of mental tests would be changed.

Introduction: Heat stress is considered as one of the hazardous occupational agents in hot environments. Working under heat stress condition may lead to individuals’ health problems. Several studies have been shown that stress in the working environments can elevate stress hormones such as cortisol. Since heat stress is one of the serious stresses in hot industries including melting, this study was done to investigate the effect of heat stress on the cortisol concentration of workers in one of the melting industries.
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Material and Method: In this cross-sectional study, 70 workers in two groups of case and control (35 people in case group from foundry unit and 35 people in control group from casting unit without heat stress) were investigated. First, a demographic questionnaire was complete for each subject. Then in order to evaluate the changes in cortisol level, blood samples were taken from the participants during their working hours (9:30 to 10 AM) and the obtained levels were compared with the normal level of cortisol, provided at 7 to 10 AM. In order to assess environmental condition, WBGT (Wet Bulb Globe Temperature) index was measured at three highest including feet, waist and head. Moreover, noise and lighting were measured at the workers work station. Data were analyzed using SPSS software version 16.
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Result: Regarding WBGT, it was shown that mean WBGT index were 33 C and 16.7 C in case and control groups, respectively. Additionally, cortisol concentration in case group was significantly higher than control group (P<0.001).
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Conclusion: Results of the present study indicate that physical stresses of working environment can lead to changes in physiology of human body. Thus, variations in hormone level in its consequences in hot environment should be considered in occupational hygine.

Introduction: Air health is an important environmental issue which has been endangered in recent years due to application of advanced technologies used for improving the financial welfare and relative prosperity of humans. Making use of pollution control systems and refinement methods are some general ways to control environmental pollution. Since several different techniques of control, each with its advantages and disadvantages are employed in order to mitigate the spread of air pollution, the aim of current study was to design a fuzzy multi-attribute decision making model to select the most appropriate air pollution control equipment in Mashhad Shargh Cement Company.
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Material and Method: After identifying the desired industry and also the production process, all factors affecting decision-making process including environmental factors, technical factors and economic factors were considered by utilizing Fuzzy Analytic Hierarchy Process method. Importance weight of these criteria was calculated and subsequently the priority of model choices were also determined using this approach.
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Result: Among main criteria of the model, economic criteria was identified as the most important factor influencing the selection of the type of air pollution control equipment, with the wight of 0.555. Environmental and technical factors with weighting of 0,286 and 0,159 also gained the next priorities, respectively. Final weights of Electro filter, Baghouse and Hybrid filter technologies were calculated 0.256, 0.415 and 0.329 in cement mill unit and 0.291, 0.374 and 0.334 in material grinding and furnace unit, respectively.
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Conclusion: Finally, the proposed model that is based on the Fuzzy Analytic Hierarchy Process indicates that the Baghouse Technique is the most appropriate technique for the purpose of dust filtration in major sources of air pollution spread in Shargh Cement Company.

Introduction: Chromium (VI) is a known human carcinogenic agent which is used in numerous industrial processes such as electroplating, welding, textile, cement and steel fabrication. The aim of this study was to determine the effectiveness of natural zeolite on the fixed bed adsorption of Cr (VI) from air stream.
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Material and Method: In this experimental study, chromium mists were generated by a nebulizer (3A model, Italy). Performance of natural zeolite in the Cr (VI) adsorption and its influencing factors such as air flow rate (1 and 3 L/min), the initial Cr concentration (0.05, 0.15, 1 and 10 mg/m³) and the bed depth (2.5, 5 and 10 cm) were investigated.
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Result: Zeolite adsorption capacity elevated by the increasing of bed depth but decreased with increasing of flow rate and inlet concentration. In order to facilitate the prediction of natural zeolite column performance Yoon-Nelson and Thomas models were used. The results showed that these models have a good agreement with our experimental data.
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Conclusion: Due to the extensive use of chromium in various industries and regulatory requirements related to workplace health and safety, Cr emission control in the occupational environment is essential. The adsorption process is one of the controlling measures of chromium emissions. The results indicated that natural zeolite has a high efficiency in Cr (VI) adsorption.

Introduction: Heat-related illnesses are major causes of morbidity in the world. Workers who are exposed to extreme heat are not be able to activate their compensatory mechanisms and their health will consequently be at risk. Heat stress due to its impact on work performance increases the likelihood of worker disease and injuries and it also affect productivity. During sugar beet harvest, farmers from about 8 am to 4 pm, are exposed to sunlight and excessive heat. Therefore, preventive measures are essential in order to protect the health of farmers and improve productivity. The aim of this project as to study the effectiveness of the rehydration to reduce heat stress and increasing productivity during sugar beet harvest, conducted in 2012.

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Material and Method: in this project, 20 farmers from sugar beet farmers were studied during summer season, from 8 am to 4 pm in West Azarbaijan- Boukan city where the average temperature and relative humidity were 29.85 0C and 41%, respectively during sugar beet harvest. Selection criteria were defined as working more than 50% of the day’s working schedule and to have worked for at least 10 days of the follow-up period. Individual characteristics and water consumption rate during the work shift and also Production output data by farmers were recorded at the end of the working day. Environmental parameters using a portable monitoring device was measured and recorded and finally, the collected data was used for analysis using spss software version 20.

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Results: WBGT-TWA index for four the period of the time from morning to afternoon obtained 27.39 0C, as it was greater than the allowable thresholds. Ten workers receive 6-7 L of liquid and harvest production was significantly increased among those who are better hydrated (P=0.005), from 5 to 7 tons of harvest sugar beet per any worker per day, against lower 5 tons for farmers without drinking enough water.

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Conclusion: Farmers productivity can be increased by applying rehydration measures during work.

Introduction: Prevention of accidents and work related diseases, are not allowed regardless of the safety of employees, customers, contractors and other persons. Assessment of individual safety management activities could reduce many losses. Present study aimed to evaluate the safety management of a household appliance manufacturing company.

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Material and Method: This study has done in a household appliance manufacturing company in Damavand city. Two questionnaires were firstly designed based on the weighted scores. The questionnaire 1 consisted of 4 indicators: Safety of machinery, Electrical safety, Risk assessment and Fire safety. Questionnaire 2 consisted of 11 sub indicators. Both questionnaires were completed by 30 HSE experts and supervisors. Reliability of questionnaires was based on cronbachs alpha coefficient. the safety status of each unit was determined and scored using information acquired by the questionnaires. Lastly, the safety of the entire company was determined.

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Result: Results showed that in safety management: the pressing and store house were in a good range of 66.66 and 60.12 points. Powder painting, enameling, laboratory were in a average range of 56.25, 55.92 and 54.15 points. Assembling and door storage were in a week range of 46.06 points.

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Conclusion: The findings showed that the safety status in the studied appliances company is in average range with 55.45 points. Therefore, it is recommended that the safety indicators should be improved for the betterment of the safety management in the company.

Introduction: Volatile organic compounds such as xylene, which are the main constituents of the oil and petrochemical industries, have serious impacts on health and can cause adverse effects on the environment. It is clear that release of these compounds into the environment should be controlled. The two-phases partitioning stirred tank bio-reactor is one of the newest methods for treating these compounds which have few side-effects besides of having appropriate efficiency since itdestroyscontaminant completely and transform it tosafer compounds.

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Material and Method: In this study, a two phase partitioning stirred tank bio-reactor, in lab scale, was used for treating the gas stream containing xylene vapors. The aqueous phase containing the bacteria Pseudomonas putida and nutrients inserted into the bioreactor with 3:1 ratio and system performance was evaluated for 432 hours in the concentration range of 1000 mg/m3 to 3500 mg/m3

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Result: Empirical findings of this study showed that the maximum, minimum and average of removal of xylene vapors by stirred two phase bioreactor containing a pure strain of Pseudomonas putida were 94.00, 54.00 and 84.94 percent, respectively.Furthermore, maximum, minimum and average of elimination capacity of xylene were obtained 93.00,24.00 and 62.02 g/m3/h, respectively

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Conclusion: Overall, the results of the present research revealed that the application of two phase stirred tank bioreactors (TPPBs) containing pure strains of Pseudomonas putida was successful for treatment of air streams with xylene.

Introduction: Working in hot and inappropriate climate condition is one of the most common problems of occupational health which can lead to heat induced diseases and even death. Heat stress may impair the cognitive processes involved in decision-making and converting simple tasks to complex ones. The aim of present study was to assess selective attention and reaction time among workers in a casting unit of a car manufacturing industry and to investigate the effects of heat stress on mentioned variables.

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Material and Method: In this retrospective cohort study 70 workers from a hot industry were selected in two of exposed and control groups. First, demographic questionnaire was completed for each of the participants and noise and light were measured as the likely confounding factors. Stroop test 1, 2, and 3 were done before and during the work in order to determine the effects of heat on selective attention and reaction time. Besides,WBGT were measured at the ankle, waist, and head levels. Data were analyzed using SPSS software, version 18.

Result.: WBGT measurements showed that the mean WBGT were 33 and 16.7 for the exposed and not exposed groups, respectively. Moreover, no significant relationships were observed between test duration, reaction time, and number of errors in Stroop tests 1 and 2 and the level of heat (P-value<0.0001). However, the mentioned variables had a significant positive correlation with Stroop test 3. Additionally, for exposed group variables of test duration, reaction time, and number of errors in Stroop 3 were significantly higher than those of control group.

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Conclusion: According to the findings in present study, heat stress causes an increase in reaction time and a decrease in selective attention. Thus, heat can be assumed as a stressor in hot work environments and the heat should be taken into account while design of job and tasks which needed selective attention or reaction time.

Introduction: Outdoor workers are exposed to heat from solar radiation and the atmospheric conditions, in addition to the heat from the working process, which is worse by global warming. The purpose of this study was to evaluate heat stress based on wet bulb globe temperature index and also to examine the relationship between WBGT and physiological indices among outdoor workers of Shabestar city.

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Material and Methods: This cross-sectional study was conducted in August 2014. WBGT measurements were taken according to ISO7243 standard in different hours. The physiological response of 53outdoor workers (including heart rate, systolic and diastolic blood pressure, oral temperature, and skin temperature) were measured among9occupationalgroups, including municipal workers, concrete makers, porters, construction and road making workers, stonemasons, farmers, traffic officers, and street vendors.

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Result: The mean WBGT index for all outdoor workers, except for municipal workers, street vendors, traffic officers and stonemason, was greater than threshold limit. The highest average WBGT index was for construction workers and the lowest was for municipal workers (respectively 27 and 26 °C). Moreover, a significant direct association was reported between the WBGT index and physiological parameters (P <0.0001), with the highest correlation coefficient belonged to heart rate (r=0.492).

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Conclusion: According to WBGT index, porters, Concrete makers, construction and road makers, and farmers had the highest exposure at all times of the day while the lowest level was related to municipal workers. What is more, heat stress showed a significant correlation with the study strains. Therefore, it is essential to conduct further research and in order to represent preventive countermeasures for the workers in this field.

Introduction: Polycyclic aromatic hydrocarbons (PAHs) are one of the most significant current environmental issues. Phenanthrene and naphthalene adsorption at activated carbon beds prevent the release of these compounds into the environment. The objective of this research was to compare the amounts of phenanthrene and naphthalene adsorption at activated carbon beds in the n-hexane solution.

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Material and Method: This discontinuous experimental study was conducted in the laboratory scale batch and in the n-hexane solution containing phenanthrene and naphthalene.PH values were adjusted by adding hydrochloric acidand 1 N NaOH. The initial and residual phenanthrene and naphthalene concentrations were spectrophotometrically measured at 270 and 266 nm, respectively.

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Results: Findings showed that the maximum adsorption of naphthalene was obtained at pH=5 and contact time of 8 hours (7.4 mg/gr). The maximum adsorption was reached at pH=7 and contact time of 11 hours for phenanthrene (8.34 mg/gr).Improvement in the adsorption capacity was happenedby the increases in contact time and initial phenanthrene and naphthalene concentrations. The adsorption kinetics of these two compounds followed pseudo-second-order and Freundlich isotherm model.

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Conclusion: Freundlich isotherm model showed a strong association with PAHs adsorption process. A weak correlationwas observed between Langmuir theory and the results of the adsorption at activated carbon beds in the organic n-hexane solution.

Introduction: Heat is one of the hazardous physical agents in the workplace. Exposure to heat and consequent thermal stress influence workers productivity in addition to adverse health effects. The aim of this study was to determine the heat stress induced productivity loss related to different tasks of farmers in Darreh Shahr city, during summer.

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Material and Method: This cross-sectional study was conducted in summer, 2014, among farmers in Darreh Shahr city. After determining the sample size, farmers’ activities were determined using hierarchical task analysis (HTA), and WBGT measurements were done according to the ISO7243. Metabolism was estimated by the ISO8996. Following, the type of activities were identified according their required metabolism. Knowing WBGT and workload and using the work capacity model, the productivity loss in different tasks and ultimately total productivity loss were calculated.

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Result: The mean WBGT activities for plowing, terracing, planting seeds, watering, fertilizing, weeding, spraying, and harvesting were 29.98 °C, 31.28 °C,30.66 °C,31.39 °C,31.99 °C,31.75 °C,31.08 °C, and 30.3 °C, respectively. WBGT values were higher than the permissible level provided by ISO7243 in all farming activities. Maximum value of WBGT was belonged to fertilizing activity (31.99 °C) and the lowest value was for plowing (29.98 °C). ANOVA test results did not show a significant difference in WBGT at head, waist, and ankle height. The highest and lowest amount of productivity loss was estimated respectively for weeding and plowing activities. The total productivity loss for farming was calculated 69.3 percent in an hour which is due to high physical activity, working outdoor, with exposure to direct solar radiation, and consequent heat stress imposed to workers.

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Conclusion: Productivity is a factor which is affected by the workplace heat stress. According to results of the present research, the amount of productivity is reduced in different tasks due to heat and this reduction is exacerbated by increase in temperature and might impact the local economy. Thus, further studies are needed to improve the working conditions.

Introduction: Volatile organic compounds such as xylene are one of the main air pollutants. Adsorption method are of the most common methods used in the control of volatile organic compounds. The aim of this study was to investigate the xylene removal from air through nano activated carbon adsorbent in comparison with NIOSH approved carbon adsorbent.
 

Material and Method: Xylene adsorption tests on nano activated carbon and activated carbon in static mode (batch) were done in glass vials with volume of 10 ml. Gas chromatography with FID detector was used for analysis. Various variables including contact time, amount of adsorbent, concentration of xylene, and temperature were studied.
 

Results: Absorption capacity of xylene at ambient temperature (25° C) in static mode and duration of 10 minutes for activated carbon and nano activated carbon was obtained 349.8 and 435 mg/g, respectively. Results of Scanning Electron Microscope (SEM) images of nano activated carbon showed particle size pf less than 100 nm. Furthermore, Transmission Electron Microscope (TEM) pictures showed particle size of 30 nm. XRD images also showed cube structure of nano activated carbon adsorbent.
 

Conclusion: The results showed that adsorption capacity at constant humidity increased by raising in temperature and contact time. What is more, nano activated carbon absorbent showed greater absorption capacity for xylene removal compared to activated carbon absorbent

Introduction: Volatile organic compounds from industrial activities are one of the most important pollutants released into the air and have adverse effects on human and environment. Therefore, they should be removed before releasing into atmosphere. The aim of the study was to evaluate xylene removal from air by nano-grapheme and nano-graphene oxide in comparison with activated carbon adsorbent.

Material and Method:  After preparing adsorbents of activated carbon, nano-graphene, and nano-graphene oxide, experiments adsorption capacity in static mode (Batch) were carried out in a glass vial. Some variables including contact time, the amount of adsorbent, the concentration of xylene, and the temperature were studied. Langmuir absorption isotherms were used in order to study the adsorption capacity of xylene on adsorbents. Moreover, sample analysis was done by gas chromatography with Flame Ionization Detector (GC-FID).

Results: The adsorption capacities of activated carbon, nano-graphene oxide and nano-graphene for removal of xylene were obtained 349.8, 14.5, and 490 mg/g, respectively. The results of Scanning Electron Microscope (SEM) for nano-graphene and nano-graphene oxide showed particle size of less than 100 nm. While, the results of Transmission Electron Microscope (TEM) showed particle size of 45nm for nano-graphene and 65 nm for nano-graphene oxide. Also, X-Ray Diffraction (XRD) showed cube structure of nano-adsorbents.

Conclusion: In constant humidity, increase in exposure time and temperature caused an increase in the adsorption capacity. The results revealed greater adsorption capacity of xylene removal for nano-graphene compared to the activated carbon, and nano-graphene oxide.

Introduction: Regarding development of several thermal indices and limitations of each, in this research applicability and validity of temperature- humidity index (Humidex) were examined against the standard heat index, Wet Bulb Globe Temperature -WBGT, as well as tympanic temperature of subjects.

Material and Method:  This cross-sectional study was done on 163 subjects at spring and summer (2013) in outdoor jobs of arid and semi-arid climates of Iran. Environmental parameters as well as tympanic temperature of subjects were measured simultaneously and then heat indices were determined. Data were analyzed using linear correlation charts and Kappa coefficient of agreement by means of SPSS software version 20.

Result: A strong correlation was obtained between WBGT and Humidex in both arid and semi-arid regions (r>0.98), while the correlation between Humidex and tympanic temperature was moderate (r=0.5-0.8). Based on the obtained Kappa value, the agreement coefficient between Humidex and WBGT was 0.878. This value was obtained equal to 0.226 for the Humidex and tympanic temperature.

Conclusion: The results of this study showed that Humidex can be applied as an appropriate substitute for the WBGT index. However, if evaluation of environmental condition with low air temperature or very hot situation is considered, relying only on the Humidex results will not provide a realistic estimation of thermal strain imposed to individuals.

Introduction: Nowadays, Shielded Metal Arc Welding (SMAW) is the most widely used arc welding. During the welding operation, typically, various harmful agents such as fumes, gases, heat, sound and ultraviolet radiation are produced of which fume is the most important component from the viewpoint of occupational health. The present study aims to compare the number and the mass concentration emitted in SMAW to determine the most appropriate index of exposure to fumes in the welding processes.

Material and Method: In this study, the portable laser aerosol spectrometer and dust monitor of GRIMM, model 1.106, was used to measure the number and mass concentration of fumes emitted from SMAW on 304 stainless steel with a thickness of 0.4 mm. Air sampling was performed at a distance of 41 cm representing the welder’s breathing zone. The measurements of number concentration (NC) and mass concentration (MC) were taken under the condition of 25 volt voltage and direct current of the electrode polarity.

Result: The total NC and MC of welding fumes in welder’s breathing zone was 1140451 particles per liter and 1631.11 micrograms per cubic meter, respectively. The highest number concentration was found to correspond to the particles with 0.35 to 0.5 micrometer-sized distribution (NC1; 938976 particles per liter) and the lowest was related to the particles with 5 to 6.5 micrometer-sized distribution (NC7; 288 particles per liter) and the particles larger than 6.5 micrometer (NC8; 463 particles per liter). Moreover, the highest mass concentration was related to the particles with 0.35 to 0.5 micrometer-sized distribution (MC1; 450 micrograms per cubic meter) and the particles larger than 6.5 micrometer (MC8; 355 micrograms per cubic meter).

Conclusion: The findings indicated that there is no agreement between number and mass concentration as two particles assessment index, and as the particles’ size become smaller, the mismatch of them is becoming more apparent. Since the smaller particles penetrate into the lower respiratory tract and have higher potential for adverse health effects, it is necessary to measure and assess particles in various size distributions and especially the smaller fraction of particles. Therefore, it is thought that considering the mass concentration alone and not paying attention to number concentration in the assessment of exposure to particles in the industrial workplaces and specifically in welding stations will not be reflected valid assessment of adverse health effects of welding fumes as a systemic poison on body organs.

Introduction: To evaluate heat stress in the workplace different indices are used. But, none of these measures have been widely accepted. The aim of this study was to determine effective criteria in selecting a heat stress index and weighting of these criteria.

Material and Method:  This study is a qualitative study that was designed and conducted within 10 stages. In the current study, effective criteria for choosing a heat stress index was determined by using Delphi technique and expert’s opinions (30 people), and then the fuzzy analytic hierarchy process was used for weighting and prioritization of these criteria.

Results: Analyzing the completed questionnaires by the experts and according to the percentage of respondents, 11 criteria were finally selected. “Simplicity” criteria by %76.6 had the highest percentage of response. But, the relative weight of this criteria was 0.041, and had the lowest weight after the “low cost” criteria.  The criteria relating to the “Standard” item was 0.141as the highest relative weight.

Conclusion: It can be concluded that the first step to have a reliable and accurate measurement is to choose a proper and correct index. Based on specialists and expert’s opinions, standardization of the index is the most important selection criteria. Other criteria that must be considered were accuracy, reliability and good correlation with the physiological strain indices.