• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.356-363
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• 2006

To investigate the exposure effect of benzene, we measured airborne benzene as external doses, uninary tt-muconic acid as an internal dose of benzene exposure and analyzed the relationship between tt-muconic acid concentration and benzene exposure. The study population of eight businesses included 157 workers(87 workers in field; exposure group, 70 workers in board; control group) who produce or use benzene in petrochemical industry. The concentrations of airborne benzene were evaluated by personal samples and urine was sampled at the pre and end shift. Urinary t,t-muconic acid as internal dose was to analyze the relationship with airborne benzene. The geometric means(GM) of airborne benzene was 0.0231 ppm(range ND-1.0471 ppm) in exposure group and 0.0147 ppm(range ND-0.3162 ppm) in control group. The geometric means(GM) of urinary t,t-muconic acid at end-shift was $196.8{\pm}2.23{\mu}g/g$ creatinine in exposure group and $149.2{\pm}2.08{\mu}g/g$ creatinine in control group. There was significant correlation between the airborne concentration of benzene and the urinary concentration of t,t-muconic acid( r=0.711, p<0.01). From the results of stepwise multiple regression analysis about t,t-muconic acid at end-shift, significant independents was airborne benzene. In this study, there were significant correlation between the urinary concentration of t,t-muconic acid and the airborne concentration of benzene. More extensive studies ruling out healthy worker effect is needed.

• Journal of Preventive Medicine and Public Health
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• v.21 no.1 s.23
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• pp.152-162
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• 1988

Benzene and toluene, which are widely used aromatic hydrocarbons in workplace, are recently proved to cause health hazards due to their toxic effects. This study investigated the influence of toluene on the urinary excretion of benzene metabolite by administering short term exposure limit(STEL) of these compounds(i.e., 13.8mg/kg of benzene and 108.8 mg/kg of toluene) intraperitoneally into Sprague-Dawley rats. After administration, urinary phenol concentration of rat was measured by gas chromatography for every three hours. Data were analyzed by non-parametric statistical methods using Kruskal-Wallis multi-sample test and Mann-Whitney U test. The following results were obtained : 1. Administration of STEL-benzene increased urinary phenol concentration in lats. 2. Urinary phenol concentration was increased logarithmically according to the dosage of benzene. 3. Excretion of phenol in urine was decreased when benzene and toluene were administered simultaneously compared with administering benzene alone. In summary, these results reveal that administration of STEL of toluene has antagonistic effect of urinary excretion of benzene metabolite in rats.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.73-76
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• 2000

A novel, continuous bioreactor system combining a bubble column (absorption section) and a two-phase bioreactor (degradation section) has been designed to treat a gas stream containing benzene. The bubble column contained hexadecane as an absorbent for benzene, and was systemically chosen considering physical, biological, environmental, operational and economic factors. This solvent has infinite solubility for benzene and very low volatility. After absorbing benzene in the bubble column, the hexadecane served as the organic phase of the two-phase partitioning bioreactor, transferring benzene into the aqueous phase where it was degraded by Alcaligenes xylosoxidans Y234. The hexadecane was then continuously recirculated back to the absorber section for the removal of additional benzene. All mass transfer and biodegradation characteristics in this system were investigated prior to operation of the integrated unit, and these included: the mass transfer rate of benzene in the absorption column, the mass transfer rate of benzene from the organic phase into the aqueous phase in the two-phase bioreactor, the stripping rate of benzene out of the two-phase bioreactor, etc. All of these parameters were incorporated into model equations, which were used to investigate the effects of operating conditions on the performance of the system. Several experiments were conducted to show the feasibility of this system. This process is believed to be very practical for the treatment of high concentrations of gaseous pollutants.

• Journal of the Korean Society of Safety
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• v.24 no.5
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• pp.28-33
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• 2009

The thermochemical parameters for safe handling, storage, transport, operation and process design of flammable substances are explosion limit, flash point, autoignition temperatures(AITs), minimum oxygen concentration(MOC), heat of combustion etc.. Also it is necessary to know explosion limit at high temperature and pressure. For the safe handling of benzene, lower explosion limit(LEL) at $25^{\circ}C$, the temperature dependence of the explosion limits and flash point were investigated. And the AITs for benzene were experimented. By using the literatures data, the lower and upper explosion limits of benzene recommended 1.3 vol% and 8.0 vol%, respectively. This study measured relationship between the AITs and the ignition delay times by using ASTM E659-78 apparatus for benzene, and the experimental AIT of benzene was $583^{\circ}C$. The new equations for predicting the temperature dependence of the explosion limits of benzene is proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Carbon letters
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• v.1 no.3_4
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• pp.143-147
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• 2001

Under the irradiation of radiofrequency wave, the dipole materials vibrate as microwave phase changes. This causes friction between adjacent molecules and enables an unique characteristics of interior heating of the materials. Using this principle, when harmful material pass through anthracite- bed which play a role as a absorber of radiofrequency wave, the material can be easily decomposed by the microwave energy. To remove benzene vapour and other solvents in the process of industry, we examined decomposition of benzene in this manner. It was found that benzene was decomposed to the methane, ethane, propane and butane, etc. during passing through the carbon-bed under the microwave impingement and distribution of methane in the products reached about 85 vol.%. The decomposition rate of benzene was high within 5 minutes from start of reaction. For a lower concentration of benzene gas, general cases in the field of industry, almost complete decomposition of benzene is believed possible and this method is surely expected to be useful for the prevention of air pollution and improvement of ambient condition.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.441-446
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• 2002

We have presented the results of thermodynamic, structural and dynamic properties of liquid benzene, toluene, and p-xylene in canonical (NVT) ensemble at 293.15 K by molecular dynamics (MD) simulations. The molecular model adopted for these molecules is a combination of the rigid body treatment for the benzene ring and an atomistically detailed model for the methyl hydrogen atoms. The calculated pressures are too low in the NVT ensemble MD simulations. The various thermodynamic properties reflect that the intermolecular interactions become stronger as the number of methyl group attached into the benzene ring increases. The pronounced nearest neighbor peak in the center of mass g(r) of liquid benzene at 293.15 K, provides the interpretation that nearest neighbors tend to be perpendicular. Two self-diffusion coefficients of liquid benzene at 293.15 K calculated from MSD and VAC function are in excellent agreement with the experimental measures. The self-diffusion coefficients of liquid toluene also agree well with the experimental ones for toluene in benzene and for toluene in cyclohexane.

• Analytical Science and Technology
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• v.9 no.4
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• pp.392-398
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• 1996

Eleven organic chemical substances, tetrachloroethylene, ethyl benzene, p-xylene, o-xylene, isopropyl benzene, n-propyl benzene. 1,2,4-trimethyl benzene, 1,3,5-trimethyl benzene, p-isopropyl toluene. see-butyl benzene, and naphthalene, which have hazardously influenced to human, were extracted from untreated wastewater collected at 26 companies of 8 types industry in the basin of Kwangju stream. Their structures were elucidated by Gas Chromatography/Mass Spectrometry(GC/MS) and in comparison with each standard reagents.

• Applied Chemistry for Engineering
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• v.25 no.3
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• pp.237-241
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• 2014

Benzene is a hazardous air pollutant, classified as carcinogenic to humans, that requires special management. Benzene exists both indoors and outdoors and the control measure of indoor benzene is different from that of outdoor benzene. The removal of indoor benzene needs to be accomplished at low temperatures (normally below $100^{\circ}C$), while outdoor benzene is usually removed at much higher temperature ($300-400^{\circ}C$) by using catalytic oxidation. This review paper summarizes the recent trend in catalytic treatment of airborne benzene, focusing on catalytic oxidation and catalytic ozone oxidation. Particular attention is paid to Mn-based catalysts for low-temperature oxidation of benzene, which are more economical than the other noble-metal catalysts. Various methods are used to generate more efficient Mn-based catalysts for benzene removal. Ozone oxidation is attracting particularly significant attention because it can remove benzene effectively below $100^{\circ}C$, even at room temperature.

• Environmental Analysis Health and Toxicology
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• v.15 no.3
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• pp.81-91
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• 2000

Residents who live near petrochemical industrial areas are exposed to a variety of petrochemicals, including benzene or benzene-containing liquids. It is a serious concern because some VOCs are carcinogens naturally present in petroleum and gasoline. The aim of this study was to assess the exposure to VOCs, measured by personal/indoor/outdoor air sampling, and to estimate the relationship between the air samples and biological monitoring data. Through biological monitoring, we investigated VOCs in blood and s-phenylmercapturic acid (s-PMA) , minor urinary metabolites of benzene. The external benzene exposure of subjects was measured using passive dosimeters and urinary s-PMA and blood-benzene were determined by GC/MS. More than 80% of subjects were detected for m-xylene, ethylbenzene, and toluene in blood samples and not detected at all for chloroform, 1 , 1 , 1 -trichloroethylene, and tetrachloroethylene. The mean concentration of benzene in the breathing zone of residents was 6.3 $\mu\textrm{g}$/m$^3$, personal, indoor and outdoor concentrations were strongly correlated to each other. s-PMA detected in all subject samples was affected by personal exposure (p< 0.05) and the level was different by age (p< 0.01). Blood benzene was not affected by external benzene during these periods .

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.599-602
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• 1993

Micellization process of dodecyltrimethylammonium bromide (DTAB) was studied by using the aromatic probe (benzene) which dissolved in aqueous DTAB solutions. Proton NMR chemical shift measurements of DTAB and DTAB-benzene system showed that benzene molecules solubilized near the micelle-water interface and that the solubilization sites within the micelles are different as the DTAB concentration is passing through 32.0 mM (hereafter we refer this concentration as the second CMC). The change of solubilization sites is also confirmed by abrupt changes of the chemical shifts and relaxation rates of benzene protons in DATB-benzene system at this concentration. It was revealed from the electrical conductivity and viscosity measurements that the solubilization of benzene caused the DTAB micelles to swell out and that the micelles prepared after the second CMC had a greater swelling effect than those prepared before the second CMC. The transition point which reflects the saturation of benzene molecules on the solubilization sites of micelles was observed at one benzene/micellized DTAB mole ratio from the electrical conductivity measurements. Along the different concentration of DTAB solution, this transition point is appeared clearly after the second CMC. From these results it is suggested that the shapes and/or sizes of DTAB micelles of the spherical micelle region prepared after the second CMC are different from those prepared before the second CMC.