• Proceedings of the Korean Society of Toxicology Conference
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• 2001.10a
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• pp.121-122
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• 2001

According to the epidemiological studies in chromium workers, hexavalent chromium is associated with the risk of lung cancer. Genotoxicity such as chromosome aberration, and cellular oxidative damages by reactive oxygen species produced by hexavalent chromium exposure may play an important role in the carcinogenesis process. We investigated the availabilities of several kinds of biological markers to assess the genotoxicity and oxidative damages from chromium exposure in Korean chromium plating workers.(omitted)

• 월간산업보건
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• s.356
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• pp.16-25
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• 2017

Chromium exists at various valences, including elemental, trivalent, and hexavalent chromium, and undergoes reduction-oxidation reactions in the environment. Since hexavalent chromium is known as a human carcinogen, it is most important to evaluate the oxidationreduction characteristics of the hexavalent chromium species. Although hexavalent chromium can be reduced to trivalent state, the detailed information on this in workplace environments is limited. The purpose of this study was to investigate hexavalent chromium reduction in time in various conditions. A pilot chrome plating operation was prepared and operated in a laboratory for this study. There was evidence that the hexavalent chromium was reduced by time after mist generation. The percentage ratio (with 95% confidence intervals in parentheses) of hexavalent chromium to total chromium was almost 100% (99.1 ; 102.3) immediately after mist generation, and was reduced to 87.4% (84.8 ; 89.9) at 1 hour and 81.0% (78.3 ; 83.5) at 2 hours, respectively. Another test indicated that hexavalent chromium collected on PVC filters was also reduced by time after sampling. Hexavalent chromium was reduced to 90.8% (88.2 ; 93.3) at 2 hours after sampling. It also was found that hexavalent chromium was reduced during storage in air. It is recommended that air samples of hexavalent chromium be protected against reduction during storage.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.590-598
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• 2005

An adequate method to identify chromium separation, Cr(III) and Cr(VI), in water samples were studied by using High Performance Liquid Chromatography(HPLC) coupled with Inductively Coupled Plasma Mass Spectometer(ICP-MS) equipped with Dynamic Reaction Cell(DRC). The characteristic distribution of Cr(III) and Cr(VI) in the raw water taken at the six water intake stations in Seoul, was analyzed by the method developed by the authors. The chromium species separated by HPLC was isocratically conducted by using tetrabutylammonium phosphate monobasic(1.0 mM TBAP), ethylenediaminetetraacetic acid(0.6 mM EDTA) and 2% v/v methanol as the mobile phase. 5% v/v methanol was used as flushing solvent. A reactive ammonia($NH_3$) gas was used to eliminate the potential interference of $ArC^+$. Several Parameters such as solvent ratio, pH, flow rate and sample injection volume were optimized for the successful separation and reproducibility. Although it has been reported thai the separation sensitivity of Cr(III) is superior to that of Cr(VI), the authors observed Cr(VI) was more sensitive than Cr(III) when ammonia($NH_3$) gas was used as the reaction gas. It took less than 3 minutes to analyze chromium species with this method and the estimated detection limits were $0.061\;{\mu}g/L$ for Cr(III) and $0.052\;{\mu}g/L$, for Cr(VI). According to the results from the analysis on chromium species in the raw water of the six intake stations, the concentrations of Cr(III) ranged from 0.048 to $0.064\;{\mu}g/L$(ave. $0.054\;{\mu}g/L$) while that of Cr(VI) ranged from 0.014 to $0.023\;{\mu}g/L$(ave. $0.019\;{\mu}g/L$). Recovery ratio was very high($90.1{\sim}94.1%$). There were two or three times more Cr(III) than Cr(VI) in the raw water.

• Environmental Analysis Health and Toxicology
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• v.21 no.4 s.55
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• pp.357-363
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• 2006

Chromium compounds are widely used in diverse industries including pigment manufacturing, painting, metal plating and leather tanning. With the wide uses of chromium, various adverse effects of the compounds on the environment and human health have been reported. Among them, hexavalent chromium [Cr (VI)], which is a carcinogenic heavy metal, has been widely studies. Epidemiological investigations have shown that respiratory cancers had been found in workers who had been occupationally exposed to Cr (VI). In this study, cell toxicity and induction of reactive oxygen species (ROS) by Cr (VI) (1, 2, 4, $8{\mu}M$) in cultured human bronchial epithelial cells were investigated. Exposure of the cells to Cr (VI) led to cell death, ROS increase, and cytosolic caspase-3 activation. The ROS increase was related with the decreased level of GSH. Chromatin condensation and fragmentation were occurred by Cr (VI) when evaluated by DAPI staining or agarose gel electrophoresis of the extracted DNA. Expression of ROS related genes including glutathione S-transferase, heme oxygenase-1, metallothionein were significantly induced in Cr (VI) treated cells. This result suggests the toxicity in cultured cells by Cr (VI) was expressed through the apoptotic process with ROS induction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.2
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• pp.161-166
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• 2012

The estuarine Gobiidae $Tridentiger$ $trigonocephalus$, $Chasmichthys$ $dolichognathus$ and $Favonigobius$ $gymnauchen$ were exposed to various heavy metals. As a measure of acute toxicity, the 96h-$LC_{50}$ in the three species exposed to copper, lead, zinc and chromium was 740-990, 1,660-1,980, 6,180-8,490 and 8,830-11,296 ${\mu}gL^{-1}$, respectively. In order of toxicity, the heavy metals were ranked copper>lead>zinc>chromium. The Gobiidae $C.$ $dolichognathus$ was more sensitive to heavy metals than $T.$ $trigonocephalus$ and $F.$ $gymnauchen$.

• Journal of the korean society of oceanography
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• v.34 no.2
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• pp.122-131
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• 1999

This study examined the relationship between the sediment pollution and the occurrence of polychaetes in a heavily polluted saltwater lake, Lake Shihwa on the west coast of Korea, separated from the sea by a dike in 1994. The species composition of polychaete assemblage was compared with that found off the lake in Kyeonggi Bay. Environmental variables investigated both in and off the lake were the grain size distribution, chemical oxygen demand(COD) and metal concentrations (Al, Fe, Mn, V, Co, As, Pb, Cr and Cu) in the sediment. We sampled sediments at 10 stations in the lake and 25 stations in Kyeonggi Bay using a modified van Veen grab. The levels of COD, chromium, and copper in sediments were much higher in Lake Shihwa than in Kyeonggi Bay. Differences in the species composition were found along the pollution gradient. An azoic zone was observed in the most heavily polluted area at the upper reach of the lake and the Polydora ligni zone in the center of the lake. Bottom fauna were diverse in Kyeonggi Bay; however, Heteromastus filiformis predominated in the organically enriched sediment. The density of dominant species differed along the pollution gradient. The highest density or H. filiformis was round at the COD level or around 5.8 mg/g. The COD level in the sediment where P. ligni predominated was tow-fold higher than that where H. filiformis occurred in large numbers. The chromium and copper contents at which P. ligni showed a maximum abundance were 120 mg/kg and 127 mg/kg, respectively. The density of H. filiformis was highest at concentrations of 56 mg/kg chromium and 13 mg/kg copper.

• Proceedings of the Korean Society of Toxicology Conference
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• 2001.05a
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• pp.151-151
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• 2001

According to the epidemiological studies in chromium workers, hexavalent chromium is associated with the risk of lung cancer. Reactive oxygen species produced by hexavalent chromium exposure may play an important role in the carcinogenesis process. We measured one kind of oxidative DNA damages, 8-hydroxydeoxyguanosine (8-OHdG) and its repair activities as an indicators of cellular oxidative stress in rat lungs by the repeated inhalation exposure to sodium chromate.(omitted)

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.663-669
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• 1992

Chromium oxide/zirconia catalysts were prepared by dry impregnation of $Zr(OH)_4$ powder with aqueous solution of $(NH_4)_2CrO_4$ followed by calcining in air. The redox behavior of prepared catalysts were investigated by reacting cumene as test material over catalysts. As a result it was found that $Cr^{6+}$ species(as chromate) on the surface of catalyst was responsible for the formation of strong acid site and the catalytic activity for the dealkylation of cumene. However, much of the $Cr^{6+}$ species was reduced to $Cr^{3+}$ species by $H_2$ formed during the catalytic reaction of cumene and the reduced $Cr^{3+}$ species was an active site for dehydrogenation of cumene to form ${\alpha}$-methyl styrene. The reduced $Cr^{3+}$ species was also reoxidized to a $Cr^{6+}$ species after treatment with $O_2$ and consequently the deoxidized catalyst exhibited catalytic activity for the dealkylation reaction of cumene.

• Corrosion Science and Technology
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• v.9 no.1
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• pp.20-28
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• 2010

According to the bipolar model, ion selectivity of some species in the passive film is important factor to control the passivation. An increase of cation selectivity of outer layer of the passive film can stabilize the film and improves the corrosion resistance. Therefore, the formation and roles of ionic species in the passive film should be elucidated. In this work, two types of solution (hydrochloric or sulfuric acid) were used to test high N and Mo-bearing stainless steels. The objective of this work was to investigate the formation of oxyanions in the passive film and the roles of oxyanions in passivation of stainless steel. Nitrogen exists as atomic nitrogen, nitric oxide, nitro-oxyanions (${NO_x}^-$), and N-H species, not nitride in the passive film. Because of its high mobility, the enriched atomic nitrogen can act as a reservoir. The formation of N-H species buffers the film pH and facilitates the formation of oxyanions in the film. ${NO_x}^-$ species improve the cation selectivity of the film, increasing the oxide content and film density. ${NO_x}^-$ acts similar to a strong inhibitor both in the passive film and at active sites. This facilitates the formation of chromium oxide. Also, ${NO_x}^-$ can make more molybdate and nitric oxide by reacting with Mo. The role of Mo addition on the passivation characteristics of stainless steel may differ with the test environment. Mo exists as metallic molybdenum, molybdenum oxide, and molybdate and the latter facilitates the oxide formation. When nitrogen and molybdenum coexist in stainless steel, corrosion resistance in chloride solutions is drastically increased. This synergistic effect of N and Mo in a chloride solution is mainly due to the formation of nitro-oxyanions and molybdate ion. Oxyanions can be formed by a 'solid state reaction' in the passive film, resulting in the formation of more molybdate and nitric oxide. These oxyanions improve the cation selectivity of the outer layer and form more oxide and increase the amount of chromium oxide and the ratio of $Cr_2O_3/Cr(OH)_3$ and make the film stable and dense.

• Carbon letters
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• v.7 no.3
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• pp.171-179
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• 2006

A carbonaceous sorbent was prepared from rice husk via sulphuric acid treatment. After preparation and washing, the wet carbon with moisture content 85% was used in its wet status in this study due to its higher reactivity towards Cr(VI) than the dry carbon. The interaction of Cr(VI) and the carbon was studied and two processes were investigated in terms of kinetics and equilibrium namely Cr(VI) removal and chromium sorption. Cr(VI) removal and chromium sorption were studied at various initial pH (1.6-7), for initial Cr(VI) concentration (100 mg/l). At equilibrium, maximum Cr(VI) removal occurred at low initial pH (1.6-2) where, Cr(III) was the only available chromium species in solution. Cr(VI) removal, at such low pH, was related to the reduction to Cr(III). Maximum chromium sorption (60.5 mg/g) occurred at initial pH 2.8 and a rise in the final pH was recorded for all initial pH studied. For the kinetic experiments, approximate equilibrium was reached in 60-100 hr. Cr(VI) removal data, at initial pH 1.6-2.4, fit well pseudo first order model but did not fit pseudo second order model. At initial pH 2.6-7, Cr(VI) removal data did not fit, anymore, pseudo first order model, but fit well pseudo second order model instead. The change in the order of Cr(VI) removal process takes place in the pH range 2.4-2.6 under the experimental conditions. Other two models were tested for the kinetics of chromium sorption with the data fitting well pseudo second order model in the whole range of pH. An increase in cation exchange capacity, sorbent acidity and base neutralization capacity was recorded for the carbon sorbent after the interaction with acidified Cr(VI) indicating the oxidation processes on the carbon surface accompanying Cr(VI) reduction.