[Assessment of the efficiency of electro-Fenton process in degradation of formaldehyde from a highly concentrated aqueous solution by aluminum and iron electrodes]

Due to its high reactivity, colorlessness, stability, purity in different commercial forms and low price, formaldehyde is increasingly used in industries. According to the CERCLA list, formaldehyde is toxic and dangerous to the humans and environment. The aim of this study was to investigate the efficiency of electro-Fenton process for pretreatment of industrial wastewater containing high concentrations of formaldehyde. This was an experimental laboratory study. First of all a reactor was designed and built. Then optimal reaction time was determined and kept constant to determine optimal pH. Finding optimal pH and reaction time, the influence of initial hydrogen peroxide concentration and arrangement of iron and aluminum electrodes as anode and cathode material in constant density, with 1 L/min aeration was investigated for treatment of synthetic wastewater containing initial concentration of 7500 mg/L of formaldehyde. MS Excel 2010 and relative standard deviation were used for data analysis and interpretation. Our findings demonstrated that the increase of pH and initial hydrogen peroxide concentration resulted in an increase of formaldehyde removal by Electro-Fenton Process. Increasing the reaction time up to 10 min resulted in an increase in formaldehyde removal, but increase of the reaction time more than 10 min led to a decrease in formaldehyde removal by the above mentioned process. Use of iron as anode and cathode electrodes led to more removal of formaldehyde in comparison to other possible arrangements between iron and aluminum. The results indicated that the maximum formaldehyde removal was 71.54 percent which was achieved at operational conditions of pH=10, current intensity of 8.5 mA/cm2, primary H2O2 concentration of 50 mM/L after 10 minutes by using iron for anode and cathode electrodes

Temporary and permanent level shifts in distortion product otoacoustic emissions following noise exposure in an animal model

Noise-induced hearing loss [NIHL] is one of the most common occupational illnesses. Most of the studies on NIHL were conducted at high noise levels that people are rarely exposed to but in industries. The function of the outer hair cells [OHCs] is impaired after exposure to industrial noise. Distortion product otoacoustic emissions [DPOAEs] are useful in examination of noise-induced level shifts. To assess the function of OHCs by DPOAE temporary and permanent level shifts [TLSdp and PLSdp] in rabbits exposed to white noise at realistic levels typically found in industrial settings over a broad range of frequencies. 12 albino rabbits were divided into two groups: the experimental group rabbits which were exposed to 95 dB SPL white noise at 500-8000 Hz for 8 hrs/day for 5 consecutive days, and the control group rabbits with no exposure to noise. The function of OHCs was examined by DPOAE level [Ldp] in different occasions. The study groups were compared for DPOAE temporary and permanent level shifts [TLSdp and PLSdp] to assess the effect of noise on OHCs function. Noise-induced DPOAE levels [Ldp] were decreased up to 20.65 dB [on day 8] and 18.93 dB [on day 11] at 5888.50 Hz [p=0.081]. TLSdp and PLSdp were significantly decreased up to 17.99 dB and 16.27 dB, respectively in the experimental group. The most and least Ldp were significantly different [p<0.05]; they occurred at 5888.50 and 588.00 Hz, respectively. There were significant differences between temporary and permanent threshold shift at various frequencies [p<0.05]. These differences were mainly related to 5888.50 Hz compared to other frequencies in each ear [p<0.05]. DPOAEs are an attractive tool for obtaining information about small temporary or permanent threshold shifts, even when the pure tone audiogram is normal

[Evaluation of chlorine dispersion from storage unit in a petrochemical complex to providing an emergency response program]

Chlorine gas is a dangerous material that is used in chemical industries. In spite of the attempts for chlorine gas release control, sudden releases still occur in the related installations. Not taking proper emergency measures after chlorine gas dispersion may result in serious harm to health of the personnel and the people residing around the industrial area. The present study considers chlorine gas dispersion scenarios, determines emergency levels and presents an optimized pattern for more effective and faster response with the least required measures for emergency conditions control. In the present paper by using Hazard and Operability Study [HAZOP] and risk matrix the possible scenarios of chlorine gas dispersion in storage tanks unit of a petrochemical complex were considered. Then the intervals of these scenarios were determined with a view to Emergency Response Planning Guideline 1-2-3. With a view to the intensity of pollution extension and the population exposed to risk the scenarios were classified in the four emergency levels defined by Center for Chemical Process Safety [CCPS]. Finally for each class of scenarios with a view to the related emergency level an optimum pattern of response plan in emergency conditions was presented. On the basis of the results of this study, chlorine gas dispersion scenario of the catastrophic explosions of the tank and scrubber system failure in the summer was classified in emergency level 4, in the winter in emergency 3, chlorine gas dispersion due to chlorine lines rupture in the summer and winter in emergency level 3 and chlorine gas dispersion due to leakage of flanges and gaskets in emergency level 2 according to emergency levels of CCPS. The results of this study showed that systematic process risks analysis by use of risks recognition methods such as HZAOP and consequence analysis may have an effective role in recognition of the possible major events. Also by classification of release scenarios in CCPS emergency levels, we can select the best pattern for emergency conditions managements

Application of microwave irradiation for the treatment of adsorbed volatile organic compounds on granular activated carbon

The purpose of this laboratory scale experimental research was to investigate the application of integrated microwave irradiation and granular activated carbon adsorption for removing volatile organic compounds [VOCs] from emissions released from industrial processes and considered major pollutants of the environment. A stream containing 300 ppm toluene was supplied and passed through the granular activated carbon [GAC]. The saturated adsorbent was placed in a quartz glass reactor and treated by microwave [MW] irradiation at heating frequency of 2450 MHz at different power levels. Adsorption capacity was evaluated through breakthrough curves and the residue analyzed by gas chromatography. Breakthrough results showed that the high relative humidity of the inlet gaseous stream could lead to decreased GAC adsorption capacity. We found that GAC could absorb microwave irradiation and dissipate heating energy increasing its temperature up to 600 Degree C in a short time mainly depending on the microwave power level. Our experimental results indicated that most of the toluene vapor passed over GAC was decomposed under 900 watt microwave irradiation after around 10 minutes. The addition of water vapor in the inlet stream slightly decreased pollutant removal rate over the GAC while the overall oxidation removal remain the same compared to stream with low content of water vapor. Adsorption isotherms showed that GAC surface area and porosity values increased slightly under microwave irradiation. We concluded that simultaneous application of GAC and microwave irradiation may be an effective approach for removing VOCs from gaseous stream

[Removal of xylene fromwaste air stream using catalytic ozonation process]

Volatile organic compounds [VOCs] are one of the common groups of contaminants encountered in the industrial activities, emitted through air stream into the atmosphere. To prevent the human and environmental health from the adverse effects of VOCs, air streams containing VOCs need to be treated before discharging to environment. This study was aimed at investigating the catalytic ozonation process for removing xylene from a contaminated air stream. In the present work, a bench scale experimental setup was constructed and used for catalytic ozonation of xylene. The performance of catalytic ozonation process was compared with that of single adsorption and ozonation in removal of several concentration of xylene under the similar experimental conditions. The results indicated that the efficiency of catalytic ozonation was higher than that of single adsorption and ozonation in removal of xylene. The emerging time and elimination capacity of xylene for inlet concentration of 300 ppm was 1.4 and 5.8 times of those in adsorption system. The activated carbon acted as catalyst in the presence of ozone and thus attaining the synergistic effect for xylene degradation. Catalytic ozonation process is an efficient technique the treatment of air streams containing high concentrations of xylene. The adsorption systems can also be simply retrofitted to catalytic ozonation process and thereby improving their performance for treating VOCs

[Effect of simultaneous noise and carbon monoxide exposure on rabbits' auditory brain stem response]

Background: Noise induced hearing loss [NIHL] is one of the most important occupational diseases worldwide. NIHL has been found to be potentiated by some of air pollutants. Exposure to noise plus carbon monoxide is common in occupational and environmental settings. This study was performed to evaluate the effect of noise and carbon monoxide exposure simultaneously on rabbits' hearing system by Auditory Brain stem Response [ABR] assessment

Materials and Methods: In this experimental study, 24 male adult white rabbits were divided to four groups: control group, noise exposure group, noise plus carbon monoxide exposure group and carbon monoxide exposure group. Auditory Brain stem Responses of the four groups were determined: before exposure, 1 hour after exposure and 14 days after exposure by click and tone burst stimulus

Results: The latency mean time of V wave in the ABR test for the group exposed to noise plus carbon monoxide, 1 hour after exposure at 1, 2, 4 and 8 KHz frequency were respectively 5.43+/-0.08, 5.50+/-0.07, 5.71+/-0.07 and 5.75+/-0.07 millisecond. These values were significantly more than the same values in the other groups

Conclusion: NIHL may be potentiated by carbon monoxide in the simultaneous exposure. Thus, it seems occupational and environmental exposure to noise plus carbon monoxide may increases hearing loss risk

[Investigating the effect of gas flow rate, inlet ozone concentration and relative humidity on the efficacy of catalytic ozonation process in the removal of xylene from waste airstream]

The catalytic ozonation is an efficient process for the degradation of volatile organic compounds from contaminated air stream. This study was aimed at investigating the efficacy of catalytic ozonation process in removal of xylene from the polluted air stream and the influence of retention time [gas flow rate], inlet ozone dose and relative humidity on this performance. the catalytic ozonation of xylene was conducted using a bench scale set-up consisted of a syringe pump, an air pump, an ozone generator, and a glass reactor packed with activated carbon. Several experimental run was defined to investigate the influence of the selected operational variables. The results indicated that the efficiency of catalytic ozonation was greater than that of single adsorption in removal of xylene under similar inlet concentration and relative humidity. We found a significant catalytic effect for activated carbon when used in combination with ozonation process, leading to improvement of xylene removal percentage. In addition, the elimination capacity of the system improved with the increase of inlet ozone dose as well as gas flow rate. The relative humidity showed a positive effect of the xylene removal at the range of 5 to 50%, while the higher humidity [more than 50%] resulted in reduction of the performance. The findings of the present work revealed that the catalytic ozonation process can be an efficient technique for treating the air streams containing industrial concentrations of xylene. Furthermore, there is a practical potential to retrofit the present adsorption systems into the catalytic ozonation simply by coupling them with the ozonation system

[Degradation of transformer oils by photolysis in order to reduce occupational and environmental hazards]

Polychlorinated biphenyls [PCBs] are toxic, persistent, bio-accumulate and pose a risk of causing adverse effects on human health and to the environment. PCB compounds exert varios impacts on human depending upon age, route of entry, intensity and frequency of exposure. This study was conducted to determine the effect of UV-C, hydrogen peroxide and solvent on the photodegradation of PCBs. The photochemical reactor was of annular geometry [500 ml volume] with a cylindrical low-pressure mercury lamp emitting at 254 nm. The power emitted by the lamp was 6 W. The whole lamp was immersed into a reactor with temperature of 32 +/- 2 C. The PCBs were analyzed by GC/ECD equipment. The degradation of total PCBs in terms of one, two and three lamps was 77.5%, 82.9% and 85.2% respectively. The degradation of total PCBs in terms of not using of H[2]O[2] and using 10% and 20% of H[2]O[2] were 74.5%, 79% and 94.5% respectively. The results of this experiments showed that UVC-photolysis of H[2]O[2] leads to a degradation efficiency of PCBs only in the presence of ethanol

Evaluation of knowledge, attitude and behavior of workers towards occupational health and safety

Studies show that about 90% of accidents occur because of unsafe behavior and human errors. Even if workers do not have the right knowledge, attitude and behavior toward safety measures in a safe workplace, all efforts for an accident-free workplace will be in vain. This study aims to determine the level of knowledge, attitude and behavior of workers toward occupational health and safety. This descriptive cross-sectional study was carried out on workers in Mahshahr Razy Petrochemical Complexm Ahwaz, Iran. A sample size of 210 was randomly selected. Data collection tool was a researcher-made questionnaire. Questionnaire's validity was gained by content-validity and its reliability was validated by Kronbach's alpha. Data was analyzed using SPSS 13. Mean age of workers was 31.1 years. The mean of their knowledge, attitude and behavior was reported 26.02, 153.18 and 36, respectively. 52.9% of workers had low, 36.7% moderate and 10.5% high level of knowledge. In addition, 75.7% of the subjects had a positive attitude towards occupational health and safety; 30% of workers had low safety behavior and 70% had safe behavior. The mean of knowledge grade shows a significant relationship with education level. A same relationship was reported for the mean of attitudes and behavior with age. Managers should design and implement educational interventions to promote knowledge, attitude and safe behaviors of workers

[Consequence analysis of toxic chemicals release from petrochemical feed and product pipelines network]

Consequence analysis of toxic chemicals releases has important influence on emergency response planning and reduction of fatalities. To determine consequences of toxic chemicals releases in petrochemical feed and product pipelines network. This was a cross-sectional study performed in Mahshahr Petrochemical Special Economic Zone [Petzone, Iran] during 2006-2007. Initially, a total number of 60 pipelines were evaluated using the chemical exposure index and the most hazardous chemicals selected for further analysis. Later, the lethal concentrations of chemicals were calculated by probit equation and local meteorological data assessed. In the end, the toxic release dispersion modeling was performed using of areal location of hazardous atmospheric program, and the fatal length for emergency response planning offered. Butadiene pipeline showed the highest chemical exposure index value however, the chlorine pipeline was found to have the most hazard distance based on life-threatening health effects of emergency response planning guideline [ERPG-3]. The LC1, LC50 and LC99 in F condition were about 703m, 413m and 248m, respectively. Determination of hazard distance and emergency response planning for chlorine pipeline based on LC1 and in F condition will supply the lowest level of fatality and highest margin of safety in areas adjacent to petrochemical feed and product pipelines network

[Survey the possibility of biodegradability of methyl tert-butyl ether [MTBE] by isolated microorganisms of activated sludges in the aqueous solutions and effects of stimulator substances on biodegradation]

Introduction: Methyl tert-butyl ether [MTBE] has been incorporated in reformulated gasoline at concentrations up to 15% [vol] to replace lead tetraethyl in order to comply with the octane index and to reduce the polluting emissions in exhaust gases. This compound is water soluble [48,000 mg/L] and one of the most common pollutants of ground water and surface water. Because of its undesirable effects on drinking water and ecologically harmful effects, MTBE removal has become a public health and environmental concern

Objective: Evaluatin of biodegradability of MTBE by isolated microorganisms from activated sludge

Materials and Methods: In this study a microbial consortium that efficiently degraded methyl tert-butyl ether was obtained by Isolated microorganisms of Activated Sludges in the Aqueous Solutions. Microorganisms were isolated from a variety of sources, generally from petroleum or chemical and urban wastewater treatment plants. All experiments were conducted at a constant temperature of 25°C. Vials of 50 ml and 125 ml volume sealed with Teflon-lined Mini-Nert caps were used for microcosm experiments. In all experiments 1% sodium azide were used as controls. Cultures were incubated at 25°C in the dark on an orbital shaker [rotation speed of 150 rpm]. The mineral medium was used for batch cultures. Samples of bacterial cultures that metabolize MTBE have been analysed for both MTBE and its metabolite TBA by direct GC analysis using FID. Cultures able to metabolize MTBE have been found in activated sludge and soils. Microbial consortium were plated on agar with MTBE vapor as the carbon source. After three weeks growth to saturation, independent clones were diluted into fresh mineral medium. This microorganisms, was a gram-positive bacterium. An aerobic microbial consortium able to biodegrade methyl tert-butyl ether [MTBE] was enriched in laboratory for four months

Results: MTBE has been shown to biodegrade under aerobic conditions and cometabolic conditions. Clearly, aerobic biodegradation of MTBE is demonstrable. In our laboratory, a microbial consortium was isolated from activated sludges based on its ability to grow on MTBE and was identified as cocobacillus. The capacity of this microbial consortium to degrade and grow on MTBE as a sole carbon and energy source is described in this paper. No biomass aggregates were observed during all the batch cultures, but the attached biomass was observed [the concentration of the initial attached biomass was about 0.11 g/ L of dry weight]. 500 mg of yeast extract per liter and 20 mg of Peat humic support growth of microbial consortium, it clearly had a stimulatory effect on consumption upper than 20%. Consortium was capable of degrading concentration as great as 1000 mg/l MTBE, whereas concentrations of 1000 mg/l MTBE and higher was not degraded

Conclusion: MTBE in low concenteration is biodegradable and biodegradability of MTBE enhanced by stimulator substances

Photochemical oxidation of reactive blue 19 dye [RB19] in textile wastewater by UV/K[2]S[2]O[8] process

In textile industry, advanced oxidation processes are used for degrading and removing color from dye baths which allow wastewater reuse. In this study, photochemical oxidation processes [UV-A/K2S2O8, UV-C/K2S2O8] and chemical oxidation process [dark/K2S2O8], were investigated in a laboratory scale photoreactor for decolorization of the Reactive blue 19 [RB19] dye from synthetic textile wastewater. The effects of operating parameters such as potassium persulphate dosage, pH, reaction time and UV source, on decolorization have been evaluated. The results of direct chemical oxidation showed that 50% of the dye was been removed using K2S2O8 in dark condition after 5h reaction time and photochemical oxidation showed that UV-C irradiation is more effective than UV-A for RB19 dye removal. The RB19 solution was completely decolorized under optimal potassium persulphate dosage of 5mmol/L and low-pressure mercury UV-C lamps [15w] in less than 30min. UV/K2S2O8 experiments showed higher color removal performance under acidic conditions [pH=3], and in this condition with 5mmol/L of potassium persulphate, 78.5% COD has been removed after 3h irradiation time. The decolorization rate fitted to pseudo-first order kinetics with respect of dye concentration. The reaction rate constants for photochemical degradation of RB19 were 0.014 and 0.237 for UV-A/K2S2O8 and UV-C/K2S2O8 processes respectively

Application of impregnated almond shell activated carbon by zinc and zinc sulfate for nitrate removal from water

In this study impregnated almond shell activated carbon by Zn° and ZnSO[4] were used as adsorbent with a particle size of 10-20 mesh. The objective of this research was to determine the ability of impregnated activated carbon in nitrate removal. The modified activated carbon had 1mm effective size, with a uniformity coefficient of 1.18. Potassium nitrate solution was used in batch adsorption experiments for nitrate removal from water. The effects of nitrate concentration, activated carbon dosage and time of contact were studied. Experimental data showed that modified activated carbon by Zn° and ZnSO[4] was more effective than virgin almond activated carbon for nitrate removal. The maximum nitrate removal was 64%-80% and 5%-42% for modified activated carbon and virgin activated carbon, respectively. While virgin activated carbon used, nitrate-N decreased from 20 to 15mg/L in 30min reaction. The final nitrate concentration was not in the standard range of WHO recommendations for water quality; while impregnated activated carbons were used, nitrate drcreased to <10mg/L. Maximum removal was over 16-17mg nitrate-N per 1g activated carbon for impregnated activated carbon. The experiments were conducted at pH=6.2, 20°C and initial concentrations of 20mg/L nitrate-N. Increase in modified activated carbon dosage increased the nitrate removal efficiency. The equilibrium time was found to be 45min for modified activated carbon

Photocatalytic decomposition of gaseous toluene by TIO[2] nanoparticles coated on activated carbon

Volatile organic compounds are considered as a group of major environmental pollutants and toluene is recognized as one of the representatives. In this research, the photocatalytic activity for toluene removal was studied over TiO2 nanoparticles embeded on activated carbon. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with 4 w and 8 w UV lamps [peak wavelength at 365 nm] to determine the oxidation rates of toluene. The photocatalyst was extensively characterized by means of X-ray diffraction and scan electronmicroscopy. Experiments were conducted under general laboratory temperature [25°C +/- 2] while the irradiation was provided by the UV lamps. The dependence of the reaction rate on light intensity as well as the deactivation of the catalyst were determined. The results indicated that the rate of the photocatalytic process increased with increasing the intensity of UV irradiation. Using the UV-A lamps, the decomposition rate of toluene was 98%. The stabilized photocatalyst presented remarkable stability [no deactivation and excellent repeatability]. The catalyst could be regenerated by UV irradiation in the absence of gas phase. The control experiments confirmed that the photocatalytic effects of toluene onto the TiO2/activated carbon catalysts in the dark conditions were negligible. Reproducibility tests proved that the photocatalytic activity of the photocatalyst remains intact even after several experiments of new added toluene quantities. The study demonstrated that the TiO2/activated carbon catalyst may be a practical and promising way to degrade the toluene under ultraviolet irradiation

[ effect of microwave radiation on rabbit's hearing]

Regarding the rapid development in technology of mobile communication and increasing growth in number of users, the radiation of these waves has become as one of the concerns of today's society. The aim of this study was to assess the potential changes in auditory system of rabbit following exposure to microwave. This was an experimental study carried out at two auditory centers of Tarbiat Modaress University and Iran University of Medical Sciences in Tehran [Iran] in 2005. White Newsealand male rabbits were the experimental animals used in our study and the Auditory Brainstem Response [ABR] as the method to evaluate the possible changes following exposure to radiation. The latency time of the fifth wave of ABR was measured and recorded pre- and post-exposure using two stimuli [Click and Tone burst] at different frequencies and two intensities of 70 and 100 dB. The latency time of wave V was increased for different frequencies used in our experiment. An increase of more than 0.2 ms was noticed especially at two frequencies of 2000 and 8000 Hz. Statistical analysis of results was indicative of no significant change between latency times of wave V [ms] pre- and post-exposure. The results of audiometry provided evidences regarding the effect of microwave radiation at the levels produced by mobile phones on rabbit's auditory system. Our data suggest the prudent use of mobile phones

Determining the effect of stress of threshold limit value of noise with shrill and bass frequencies on antioxidation and lipid peroxidation variations of liver tissue of rabbit

Background and Purpose: Noise, in high intensity, is one of the major physical stressors. The aim of this study was to determine the effect of stress of threshold limit value of noise with shrill and bass frequencies on antioxidation and lipid peroxidation variations of liver tissue of rabbit

Methods and Materials: This experimental study was carried out on 18 male white New Zealand rabbits at Tarbiat Modarres University in 2004. Rabbits were randomly divided into three groups: Control Group [unexposed to noise], Group 2 exposed to noise [85 dB SPL,< 250-3540Hz, 8 h/day, 96 h] and Group 3 exposed to noise [3540Hz-20kHz, 85 dB SPL, 8 h/day for 96h, 12 days]. The obtained data were analyzed in SPSS. One-way ANOVA and post hoc Tukey test were used for comparing means across the groups; differences at P<0.05 were considered statistically significant

Results: The findings indicated that Malondialdehyde [MDA] levels were 5.5, 5.54, and 5.71 in the groups 1, 2, and 3 respectively, and that the glutathione level was 0.131 g per micromol liver tissue across three groups. It was also found that the differences were not statistically significant [P=0<0.05]

Conclusion: According to the findings of the present study, despite limited variation in Malondialdehyde [MDA] levels induced by noise with 85dBA frequency, it does not induce significant changes in levels of Malondialdehyde [MDA] and glutathione in the liver tissue of rabbits

[Comparison of ethanol, methanol and succinate effects as carbon sources on effluent biological denitrification]

Increase of nitrate concentration in water sources is becoming a serious problem in many parts of the world. Nitrogen containing compounds released into environment can create serious problems, such as eutrophication of water sources and hazard potential to human health, because it has potency of causing methemoglubinemia disease and cancer. Between recommended methods, biological denitrification is an effective method to remove nitrate from water and wastewater. In this study, biological nitrogen removal process was evaluated using ethanol, methanol and succinate as different organic carbon sources in batch scale. The different parameters, carbon source, initial nitrate concentration, pH, and inoculated of bacteria were evaluated. The experimental results were showed that bacteria can not use methanol as carbon source. The dinitrifyers bacteria can dissimilate 200 mg/L No3-N, in the optimum condition: 28 °C, pH 7.2 and initial inoculation of 3x 10[8] CFU/ml, respectively. In the process, produced nitrate-N was less than 1 mg/I. The bacterium Pseudomonas stuizeri can use ethanol as carbon source for biological denitrification, but efficiency of succinate was better than ethanol

Assessment of bagging operators exposure to with PVC airborne particulates

Dust consists of tiny solid particles carried by air currents. These particles are formed by many different processes. One of these processes is polymerization of inert plastic such as Polyvinyl Chloride production plant. According to the Occupational Health and Safety Assessment Series requirements, section 4.4.6, occupational health and safety risks must be defined and controlled where needed. This field study was conducted to evaluate the occupational exposure of packaging operators to airborne polyvinyl chloride dust in order to health risk assessment and recommend feasible controlling methods. The mass concentration of polyvinyl chloride particulate was measured in two fractions according to the particle size that expressed as total and respirable particulates. The Air Sampling Methods, Methods for the Determination of Hazardous Substances 14/3, of Health and Safety Executive were used as a standard sampling protocol. The average mass concentrations for respirable and total particulates were measured 3.54 +/- 0.3 mg/m[3] and 11.89 +/- 0.8 mg/m[3] respectively. Also health risks of studied condition were estimated as significant level, category one, therefore the risk must be reduced below the standard level. According to the work requirements to reduce the emission rate and mitigate the health risk exposure, a local exhaust ventilation system design was recommended for bag-filters of hopper tank

Study of factors related to accidents occuring during the construction phase of oil, gas and petrochemical projects

Construction phase in industries is a dynamic process that is naturally and intrinsically dangerous and as it becomes more complicated, the accidents rate also increases. One should note that without considering a model, one could not obtain useful and reliable information and method to prevent accidents. Therefore, to achieve useful methods for preventing accidents, it is desirable to consider a model. The general goal of this study was presentation of a model. A model is the reflection of a fact. In other words, it should be said that the model represents a system or process whose behavior can be predicted. Models are therefore used for understanding the behavior of actual terminals and show a theory in the way that covers important variables for describing phenomena and instead, ignore factors of low importance in the expression of those phenomena. This study was a research article conducted in 2004-2005 in the Assaluyeh region. Data was gathered from accident reports present in security and health records of the projects and also statistics present at the treatment centers. In this study, an analytical model [multi-regression] was presented to describe the impact of effective and deep factors on the possibility of an increase in accidents leading to death, through measurement of the effects of independent variables on the dependent variables. For this purpose, the structure of 50 accidents that led to death were studied along with another 2700 accidents, and after studying the accident reports and related documents, observing operations and equipment, counseling with accident observers and an expert team of managers, supervisors and engineers, and simulation of some accidents, unsafe conditions and functions, mismanagement and use of worn out and defective tools, equipment, devices and machinery were considered as the four independent variables and the job accidents leading to death were considered as dependent variables. The relationship between independent and dependent variables, evaluation of regression coefficients and the test of different models were based on multi-regression analytical model and analyzed using Eviews software program. The final findings of this study, while specifying the possibility of occurrence of accidents leading to death with the existence of any of the independent variables showed that among the independent variables, unsafe conditions and mismanagement have relatively more important roles to play in the occurrence of accidents leading to death such that in conclusion, these factors have been defined as root causes in the model. Since the adjusted coefficient determined for the model in this research was 0.99; that is, the specified model could describe 99 percent of changes related to the number of job accidents leading to death and it is only for one percent of other accidents that there was no justified answer. In another words, those causes were not seen in the model. Therefore, it could be concluded that this research as compared to similar researches gained more useful results. Thus, by omitting or lowering unsafe conditions and mismanagement factors, accidents resulting in deaths can be reduced

[ comparison of effects of toluene, especially noise and toluene along with noise per auditory brain stem response on rabbit]

An increase more than definite limit in sound pressure level is harmful for health mean while, organic solvents like toluene are used in industrial processes with noise widely. So, this study was going to investigate the relationship between toluene [1000ppm], noise and toluene along with noise [frequencies 4000 and 8000 Hz] per auditory Brain Stem response [ABR] on rabbits being exposed to these contaminants. This survey was done in experimental method on 48 three months old, male adult white New Zealand rabbits [1800 +/- 200 g body weight], in nine groups which were exposed to toluene [1000 ppm], noise [4000 Hz], 100 dB SPL, combination of toluene and noise conducted using click and tone burst stimuli in 110dB sound pressure level. Then the results of ABR test of groups exposed were analyzed by SPSS software. One-way variance [ANOVA] analysis was used to compare the groups and Turkey test was applied as a post hoc test for comparison among the groups. P values were obtained by Turkey test. t-test was conducted for comparison of ABR test results after and before exposing groups. Differences at the level of P<0.05 were considered statistically significant. The results of the study showed that Exposing rabbit's to combination of toluene and noise caused hearing impairment in all of frequencies auditory especially in frequencies 250, 500 and 1000Hz. So that, wave five in ABR test [tone burst stimuli] didn't formed in 250-1000 Hz 4.84 +/- 0.07 ms, group exposed to toluene 5.18 +/- 0.07ms, noise group [4000hz] 5.5 +/- 0.07 ms and in combination noise and toluene group [4000Hz] 5.79 +/- 0.07 ms. The mean of latency time of V wave in control was compared to that group noise group P=0.01, toluene group P=0.07 and combination noise and toluene group P=0.0001. According to the result of this study, both toluene and noise exposure caused the rabbits in hearing impairment but combination of toluene and noise exposure in frequencies of 4000Hz and 8000Hz was much worse than hearing impairment. So that, the ABR test on rabbits didn't formed V wave in low frequency