• Journal of Korean Society for Atmospheric Environment
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• v.19 no.3
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• pp.325-331
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• 2003

A biofilter study was conducted by changing inlet concentration and residence time for the removal of gaseous benzene and ethylene. In addition, carbon dioxide produced from the biofilters was investigated. Over 96% of benzene was removed at the residence times of 2 and 4.3 min, and inlet benzene concentrations of 220∼300 ppm. The ethylene biofilter was capable of achieving ethylene removal efficiency as much as 100％ at a residence time of 14 min, and inlet concentrations of 99∼290 ppm. At a steady state, the carbon dioxide of 409∼611 ppm was produced with an ethylene inlet concentration of 290 ppm. Most of benzene and ethylene were degraded at lower part of the biofilters where more microbial activity occurred.

• Microbiology and Biotechnology Letters
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• v.16 no.5
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• pp.374-378
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• 1988

Treatability and maximum no inhibitory effect concentration of benzene were measured in the synthetic wastewater medium by the activated sludge in the continuous activated sludge reactor. The maximum no inhibitory effect concentration was 1, 600mg per liter. Benzene concentration over 500mg per liter inhibited the growth of microorganims by the measurment of E/BOD, and the treatability of benzene at the maximum no inhibitory effect concentration was over 95%.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.83-87
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• 2000

Combustion characteristics of immobilized benzene and toluene in sands were studied. Experiments were performed by burning benzene and toluene immobilized on sands(particle size 0.1~0.5mm) to measure combustion rate and combustion temperature. The longer time from ignition to extinguishment was resulted from the larger particle size exhibited the higher mass burning rate. Of aromatic compounds tested the relative magnitude of facilitation of combustion was benzene and toluene. Combustion temperature of benzene and toluene without regard to the types of benzene and toluene was not increased with smaller sand. However, with larger sands, combustion temperature of benzene and toluene were increased by 50~$100^{\circ}C$ and the highest combustion temperature was obtained with larger sands.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.206-211
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• 2001

This article describes identification and quantification of benzene in the casting process. Air samples around the casting process were taken by using personal air sampler attached charcoal tube and desorbed by carbon disulfide. The identification and quantitative analysis of benzene have been performed by GC-MS and GC-FID. Calibration range of standard solutions for benzene was prepared in range from 0.1 to 2 times of TLVs concentrations($1.4{\sim}28{\mu}g/1m{\ell}$ CS2) and the limit of detection was $0.11{\pm}0.002{\mu}g/1m{\ell}$ CS2. Benzene detected in airborne was ranged in 4.0ppb~104.7ppb.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.10 no.1
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• pp.58-73
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• 2000

Objectives : This study was performed to evaluate BTEX exposure to gas station service attendants and the critical affect of benzene and MtBE airborne concentration. Methods : the degree of exposure to airborne BTEX and MtBE was examined in the service attendants at seven gas stations across the country during a summer season. The TWAs(time-weighted averages) of atmospheric concentration of substances in personal and area samples, were calculated. The component ratio of BTEX and MtBE in the samples of bulk gasoline from each station studied was also measured. Results : The airborne concentrations of BTEX and MtBE showed a lognormal distribution and The TWA concentrations of benzene in personal samples from each station were 0.089 ppm - 0.18 ppm, and those of toluene were 0.097 ppm - 0.2 ppm. The average TWA concentrations of xylene and ethyl benzene was 0.03 ppm and 0.001 ppm, respectively. The TWA concentrations of MtBE were 0.4 ppm - 1.3 ppm. The volume concentrations of MtBE, toluene, ethyl benzene and xylene in the bulk gasoline samples were 3 - 7.4 %, 3 - 12 %, 0.64 % and 1.5 - 10 %, respectively. Conclusions : The benzene concentration was detected to exceed the ACGIH threshold benzene level of 0.5 ppm, in one of 74 personal and area samples. MtBE, a substitute for aromatic compounds such as benzene in gasoline, was found to bring about a greater chance of exposure to carcinogen, due to its high vapor pressure and carcinogenicity.

• 대한예방의학회:학술대회논문집
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• 1994.02a
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• pp.681-691
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• 1994

The American Conference of Governmental Industrial Hygienists (ACGIH) has proposed a threshold limit value (TLV) for benzene of 0.1 ppm. Individuals representing the American Petroleum Institute (API)and the Chemical Manufacturers Association (CMA) have argued that 1) the risk assessment by Rinsky .et al. which ACGIH partially relied upon for its proposed TLV overestimates the risk; however, at the exposures levels of interest - (e.g., 0.1 to 1.0 ppm) for establishing a benzene TLV, the Rinsky et al. assessment provides lower estimates of leukemia risk than most others; 2) ACGIH should not use the Dow study for direct observational evidence of leukemia risk associated with low-level benzene exposure because of confounding exposure; however, it is unlikely that confounding exposures played a role in the excess of leukemia demonstrated in the study, and the Dow cohort was exposed to an average benzene concentration of about 5.5 ppm benzene for 7.11 years (31:1.5 ppm-years), while some of the individuals in the study who died from leukemia were exposed to an average of only 1.0 ppm without the opportunity for highpeak exposures; 3) the Occupational Safety and Health Administration (OSHA) established an 8-hour time-weighted average (TWA) of 1.0 ppm in 1987, and there is no new evidence that would justify reducing the TWA below that level; however, the OSHA TWA of 1.0 ppm was based on economic feasibility and the level of excess risk remaining at 1.0 ppm, i.e., 10 excess leukemia deaths per 1000 workers over an occupational lifetime (45 years) according to OSHA's preferred estimate leaves behind I risk considered significant by OSHA. In addition, chromosomal studies among workers and in animals exposed to benzene indicate that low-level exposure, i.e., 1.0 ppm, is associated with elevated Cytogenetic damage. On the basis of adverse health effects data alone, in this author's opinion, it would be poor science and poor public health policy to establish a benzene TLV greater than 0.1 ppm.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.96-100
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• 1998

The effects of electron acceptors and acclimation of inoculum on the anaerobic degradation of benzene, toluene, and m-xylene (BTX) were investigated to enhance the rate of degradation by estuarine sediment inoculum. With the fresh sediment inocula, degradation of BTX ensued after a 10-week acclimation period, and 37~61% of benzene and 57~61% of toluene were degraded after 16 weeks. Sediments from heavily contaminated sites showed higher degradation rates of BTX. After a 6-month of acclimation, degradation onset rapidly from the time of BTX addition and no difference was found among the sediment inocula. Single compound of BTX was slowly degraded in the methanogenic conditions, however, the degradation of BTX mixture was slow in the denitrifying conditions. Although the degradation rate of m-xylene was the fastest among the components of BTX mixture, longer acclimation enhanced the degradation rate of BTX, especially that of benzene. When the culture fluids were tested with Microtox, anaerobic degradation of BTX reduced the toxicity of BTX as well.

• Toxicological Research
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• v.11 no.2
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• pp.205-213
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• 1995

This study was undertaken to investigate the effects of organic solvents on xenobiotic metabollzing enzyme system in vivo by meaas of experimental conditions i.e. (1) single group which was treated by benzene (B), toluene (T) and xylene (X), respectively, (2) combination group which was treated by mixture of benzene+toluene (BT), benzene+xylene (BX), and toluene+xylene (TX), respectively, (3) mixture group which was treated by benzene+ toluene+xylene mixture (M), and to interpreat the interaction between the organic solvents metabolizing enzymes. 1. The contents of cytochrome P-450 in liver microsomes were increased (p < 0.01) in organic solvents treated groups, and the contents of cytochrome P-450 were increased by following order of B < T < M < BT=BX < X < TX. 2. The activity of cytochrome P-450 dependent AHHase was significantly higher in organic solvents treated groups than in control group (p < 0.01), and the activity of AHHase was increased by following order of B < T < BT=BX=TX=xylene < M. 3. The activity of NADPH P-450 reductase was significantly higher in organic solvents treated groups than in control group (p < 0.01), and the order of M < combinated group < X < T

• Journal of Preventive Medicine and Public Health
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• v.20 no.2 s.22
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• pp.236-246
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• 1987

n-Hexane and benzene are organic compounds which have been widely used as industrial solvents. However, they are also increasingly recognized as important pollutants in working environment. The purpose of this study is tp analyze neurotoxicity of benzene and n-hexane. In this study, tibial nerve of Sprague-Dawley rats were observed after exposing them to two different concentrations of these compounds (6000 ppm of n-hexane and 2000 ppm of benzene) which were known to be the levels to cause subacute toxicity for the three different periods; two weeks, four weeks, and six weeks. The following results were obtained from the analysis of variance, Duncan's multiple comparison test, and regression analysis: 1) Myelin sheath thickness of nerve fiber for two n-hexane exposed groups (four weeks and six weeks) were both reduced compared with the control group and the benzene exposed group. 2) There were positive relationships between nerve fiber diameter and myelin sheath thickness for both exposed and control groups. 3) There was no significant difference in myelin sheath thickness from equal diameter nerve fibers between benzene exposed group and control group, but the greater number of thin myelin sheath were observed for n-hexane exposed group compared with control group. Thus, it is concluded that n-hexane tends to reduce the rate of growth of nerve fiber more than the benzene and control group. While these results shed light on understanding the effects of benzene and n-hexane, the duration of exposure was not long enough to apply these results to real working environments. In addition, to further understand the mechanims of nerve degeneration caused by organic solvents, both epidemiological and biochemical studies should accompanied by this kind of study.

• Korean Journal of Microbiology
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• v.37 no.1
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• pp.85-91
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• 2001

Biological treatment of benzene and toluene contaminated soil was investigated in laboratory microcosm of 16 different types for degrading benzene and toluene by indigenous bacteria. At the experimental conditions of the microcosms fast degrading benzene and toluene, moisture contents were 30% and 60% in a soil gap and content of powdered-activated carbon(PCA) for adhesion of benzene and toluene-degrading bacteria was 1% in total soil mass. At the conclusion of the shifted bacteria community, Case 6 and case 7 were operated until 10 days, and then the total cell number and the number of benzene and toluene degrading bacteria were investigated. The total cell number of Case 6 and Case 7 increased 488 fold and 308 fold of total indigenous cell, respectively. The number of benzene and toluene degrading bacteria increased and maintained the percentages occupied in pre-operating microcosm. Species of benzene and toluene degrading bacteria in microcosm changed from species of Gram negative bacteria to Gram positive bacterial species after soil exposed to benzene and toluene.