In vitro-Screening von Gefahrstoffen in der Arbeits- und Umweltmedizin

Chromium, especially the metal and its trivalent and hexavalent compounds, are of great industrial interest. As a matter of fact, chromium workers have an occupational risk. While trivalent chromium compounds are of low toxicity, the hexavalent compounds are strong oxidants which cause not only a direct tissue damage (=acute toxicity), but also possess a carcinogenic, mutagenic and teratogenic potential (=chronic toxicity). Since the kidney is the main target organ after oral and/or dermal uptake of hexavalent chromium is the kidney, tubular necrosis might be the result of an acute toxification. This report presents anin vitro assay with cultured renal epithelial cells which allows the evaluation of the acute toxicity not only of trivalent and hexavalent chromium compounds, but also of various hazardous substances used in industrial production process. As shown here, an acute toxic effect was not detectable for the trivalent chromium (chromium (III)-chloridehexahydrate) within 24 h of exposure to concentrations as high as 200 μmol/l. In contrast, renal epithelial cells which were exposed to hexavalent chromium (potassium chromate) for the same time period exhibited marked signs of toxicity such as a rounding and detachment of the cells from the floor of the culture plates, an elongation and perinuclear development of vacuoles in the vital cells which were still attached, as well as a cells swelling and cellular fragments caused as a result of necrotic cell death and subsequent lysis. This toxic effect was already observed at concentrations above 5 μmol/l. In conclusion, thein vitro assay might be a good tool for the screening of hazardous substances in industrial medicine. More-over, by using additional tests, the chronic toxicity of such substances can also be examined. The selection of specific cell strains such as hepatocytes, neural cells etc. also allows the evaluation of toxic effects in individual organs. Thein vitro assay can not only be applied for the investigation of basic mechanisms of toxification and detoxification of specific compounds, but also delivers a basis for the screening of the reactivity of individual hazardous substances. Finally, the assay would allow a reduction in animal experiments as well as the simultaneous testing of a reactivity to multiple, hazardous substances.     

Assessment of the role of thymol in combating chromium (VI)-induced oxidative stress in isolated rat erythrocytes in vitro

Thymol, the main phenolic compound in Thymus vulgaris, has been shown to have various biological effects. The main objective of this study was to investigate the efficacy of thymol on counteracting hexavalent chromium-induced oxidative damage in rat erythrocytes in vitro. The radical scavenging activity of thymol was examined using the 1, 1-diphenyl-2-picrylhydrazyl assay. Erythrocytes resistance to oxidative damage, lipid peroxidation, osmotic pressure, hemolysis as well as morphological alterations were evaluated in the presence of 2.5 µg thymol mL^?1 with or without 5 µmol hexavalent chromium mL^?1 of the incubation media. Results from the 1,1-diphenyl-2-picrylhydrazyl assay denoted good radical scavenging activity of thymol. Thymol caused a significant increase in superoxide dismutase and catalase activities and reduced glutathione content in erythrocytes intoxicated with hexavalent chromium. In contrast, the presence of thymol resulted in markedly less-elevated malondialdehyde levels, hemolysis, and destabilization of erythrocytes exposed to hexavalent chromium. Microscopically, thymol markedly reduced hexavalent chromium-induced morphological alterations in rat red blood cells. Conclusively, thymol counteracted hexavalent chromium-induced oxidative damage in rat erythrocytes.     

Preparation of amphiphilic composite and removal of oil and hexavalent chromium from wastewater

A new composite for water treatment was prepared by melt blend for oil and hexavalent chromium absorption. Ethylene Propylene Diene Monomer (EPDM) was the matrix, calcinatory Fe₂O₃ and anion-exchange resin 201×7 were the fillers. This composite can suspend in water–oil contact (WOC) and absorb oils and hexavalent chromium in wastewater simultaneously. The absorbencies of composites changed greatly with various ratios of calcinatory Fe₂O₃ and anion-exchange resin 201×7. The results showed that the oil absorbencies increased continuously and hexavalent chromium absorbencies were step-down as calcinatory Fe₂O₃ loadings from 13 to 19%. The composite can adsorb oils and hexavalent chromium simultaneously. The optimized proportion of calcinatory Fe₂O₃ and anion-exchange resin 201×7 in composite was found when the absorbencies of oils and hexavalent chromium reaching the maximum simultaneously. This composite is an inexpensive, convenient and high efficiency material for removing oils and hexavalent chromium from wastewater.     

底泥铬污染的纳米铁粉修复及其土壤酶活性动态

采用纳米铁粉修复Cr(Ⅵ)不同程度污染底泥,通过测定底泥中4种土壤酶活性,分析纳米铁粉修复对Cr(Ⅵ)污染底泥土壤酶活性的恢复情况.结果表明,纳米铁粉修复对底泥Cr(Ⅵ)有很好的去除效果,添加底泥干质量1%的纳米铁粉在16 d内对底泥30～100 mg·kg-1的Cr(Ⅵ)的去除率均高于99.7%.Cr(Ⅵ)污染显著降低了底泥多酚氧化酶、过氧化氢酶、蛋白酶和脲酶的活性.其中多酚氧化酶对Cr(Ⅵ)污染有很好的线性响应,可用于0～100 mg·kg-1底泥Cr(Ⅵ)污染评价.经过16 d的纳米铁粉修复,Cr(Ⅵ)污染底泥的脲酶活性恢复至未污染对照水平,过氧化氢酶活性的恢复效果不明显,多酚氧化酶和蛋白酶活性有待进一步恢复.     

Biochemical speciation in chromium genotoxicity

The biochemical speciation of chromium compounds in mammalian cells is discussed with respect to uptake, metabolism, DNA binding and damaging. Whereas soluble hexavalent chromium is taken up rapidly and accumulated intracellularly after its reduction, compounds of trivalent chromium penetrate biomembranes about three orders of magnitude slower. Cr(VI) after its uptake is metabolised by electron donating compounds via Cr(V) to Cr(III) compounds. Chromium from various Cr(III) compounds, but not chromate, binds to chromatin in isolated cell nuclei. The DNA‐protein crosslinks and DNA strand breaks observed in rat liver and kidney after chromate administration are also found in vitro, when Cr(III) compounds (but not chromate) interacts with isolated nuclei. In the Chinese Hamster cell HGPRT mutation assay, three out of four tested Cr(III) complexes were found to be mutagenic. In a direct DNA strand break assay with supercoiled bacteriophage PM 2 DNA, neither chromate nor the four Cr(III) compounds tested caused nicks. However, the combined action of chromate plus glutathione as well as the isolated complex of pentavalent chromium, Na₄Cr(glutathione)₄, did cause DNA breaks. Reactive oxygen species are inferred to be the ultimate DNA nicking agents in this assay. In conclusion there appear to be two mechanisms of chromate genotoxicity; one with direct DNA damage caused by Cr(V) species and one via DNA‐protein crosslinks formed with Cr(III), the final reduction state of chromate.     

Effects of phosphorus concentration on Cr（VI） sorption onto phosphorus-rich sludge biochar

To investigate effects of phosphorus content on Cr（VI） sorption onto phosphorus-rich biochar, sewage sludge of different phosphorus concentrations from 4 to 60 mg.g-1 by dry weight were prepared and carbonized to make biochar for batch sorption experiments. Test results revealed that different phosphorous concentration of raw sludge had respective impacts on surface area, pore surface area, average pore diameter and pH value of derived biochar. The adsorption kinetics of phosphorus-rich biochar could be described by the pseudo-second-order model. The sorption isotherm data followed Langmiur model better than Freundlich model. Biochar produced from sludge with phosphorus concentration of 20 mg. gl gave the largest chromium sorption capacity, which could be attributed to its largest surface area and pores surface area comparing with those of＇biochars from sludge with other phosphorus concentrations. The chromium loaded biochar was analyzed using Fourier Transform Infrared Spectroscopy and X-ray Diffraction measurement. The results indicated that chemical functional groups hydroxyl and methyl on surface of biochar were involved in Cr（VI） binding and its reducing to Cr（III）. Then, a portion of Cr （III） in form of various phosphate precipitates was bound onto biochar surface and the rest was released into the solution. The experimental results suggested that phos- phorus played an important role in pore and surface area development of sludge biochar during pyrolytic process. It also could react with Cr（III） on the biochar surface that impacted on capacity of Cr（VI） removal from solution by sludge biochar. Therefore, phosphorus concentration in sludge should be considered when sludge pyrolytic residue would be reused for heavy metals sorbing.     

铬在小鼠体内的蓄积效应与毒性

铬的工业用途很广,主要用于金属加工、电镀、制革等行业,这些行业排放的三废导致了环境铬污染,对环境生态和人体健康造成危害。为探究铬对动物的毒性作用,选择昆明种纯系小白鼠作为受试生物,研究六价铬在小鼠体内的蓄积效应及毒性。结果显示,饮用水中一定浓度的六价铬(15~70 mg·L-1)可抑制小鼠体重的正常增长,染毒30 d后,小鼠肝脏和肾脏脏器系数下降,脾脏和脑的脏器系数提高;总铬含量在心脏和脾脏中增高,其他脏器中无明显蓄积效应;铬染毒组小鼠骨髓细胞活性氧水平提高,骨髓嗜多染红细胞微核率显著增高。结果表明,通过饮水摄入六价铬可造成小鼠肝肾损伤,心脏和脾脏内铬蓄积,并通过活性氧损伤效应破坏机体的遗传稳定性。     

Chromium sorption on grape stalks encapsulated in calcium alginate beads

A novel sorbent based on 2% grape stalk wastes encapsulated in calcium alginate beads was investigated for the removal of Cr(VI) and Cr(III) from aqueous solutions. The sorbent proved to be efficient for chromium removal in both hexavalent and trivalent forms from aqueous solution at pH 3.0. In binary mixtures, the presence in solution of one of the forms enhances the sorption of the other which results in an increase of the amount of total chromium removed. This study suggests that the proposed sorbent can be used for the removal of chromium from wastewaters through a cost-effective and environmentally friendly process.     

Chromium Concentrations in Geobotanical Samples from West Pokot District, Kenya

The study analyses chromium concentration in plants growing around an area of chromite mineralisation, and proposes that the availability of chromium in plants could have adverse health effects when ingested by domestic animals and ultimately by the human population. This geoepidemiological attribute of geobotany has been observed in the form of chromium eczema in humans. The study was undertaken in the Sekerr Sub-location West Pokot District, which is located in the humid tropical region of the Republic of Kenya. As well as having natural vegetation cover, there are no sources of airborne pollutants in the area, which would vitiate trace element analysis in geobotanical research. The assay results show that the species Satureja abyssinica, Protea kilimandischarica, Ficus sycomorus, and Maerua subcordata have high chromium concentrations. These plants are generally browsed by domestic animals and are in turn eaten by humans. It is, therefore, proposed that a detailed analysis of chromium concentration in blood samples of both domestic animals and the human population be undertaken in order to assess its concentration levels in the population living in this geochemical environment.     

Chromium binding by calf thymus nuclei and effects on chromatin

1. No binding of chromium was detected after incubation of calf thymus nuclei with hexavalent chromium up to 0.5 mM.

2. Chromium was readily taken up and tightly bound after incubation with trivalent chromium.

3. In a DNA‐filter binding assay, increasing amounts of chromium and DNA were bound with increasing chromium trichloride concentrations incubated with the nuclei.

4. Treatment with proteinase K abolished the increase in DNA retention induced by trivalent chromium.

5. It is concluded that trivalent chromium is the ultimate genetoxic agent after chromate uptake by living cells.

     

Biosorption potential of Cr(VI) by Kocuria sp. ASB107, a radio-resistant bacterium isolated from Ramsar,Iran

Heavy metal pollution in soil and wastewater is a worldwide environmental issue in which microorganisms play a significant role for its removal. In the present study, biosorption of Cr(VI) by the live and dead cells of Kocuria sp. ASB107, a radio-resistant bacterium, was investigated. The effect of contact time, solution pH, initial hexavalent chromium concentration and adsorbent dose on biosorption efficiency was studied. Also, live cells were further immobilised on various matrices by different techniques and then were examined for tolerance to chromium biosorption. Experimental results indicated that the removal efficiency of chromium increased with decrease in pH, initial Cr(VI) concentration, and also increase in adsorbent dose and the contact time. The maximum removal efficiency of live and dead cells at acidic pH of 4–4.5, contact time of 24 hours, adsorbent dose 1.6?g/100?mL and initial chromium concentration 25?mg/L were 82.4% and 69.2%, respectively. The adsorption data was described well by Langmuir isotherm model. Among all immobilisation techniques tested, cross-linking showed the highest biosorption of Cr(VI). Results indicated that live cells of Kocuria sp. ASB107 were better than dead ones.     

Differential Pulse Polarographic Analysis of Lead and Chromium Content in Louisiana Waters

In this investigation, polarographic analyses of water, sediment, and animal samples from Devil's Swamp near Baton Rouge, Louisiana, have been conducted. The focus of this work has been on detection of lead and chromium levels. Lead has been found to be relatively uniformly distributed among the various size fractions of the sediment and is present at a mean level of 18.7 µg g^-1. In the water the concentration is about 15 µg L^-1 of which 75% is bound in suspended particulates and the remainder is dissolved. Preliminary results indicate that more chromium than lead is present in bone and muscle of bullfrogs, and, for each metal, there is a higher concentration in muscle than bone. The mean lead muscle tissue concentration is 550 µg kg^-1, which suggests that bioaccumulation of this metal is occurring, assuming that water contact or ingestion are the main routes of exposure. An important aspect of this research has been optimizing polarographic methodology for performing chromium speciation studies. Methods for determining the amounts of hexavalent and trivalent chromium in mixtures containing the two have been developed.     

Stabilization of hexavalent chromium with pretreatment and high temperature sintering in highly contaminated soil

• Separate reduction and sintering cannot be effective for Cr stabilization. • Combined treatment of reduction and sintering is effective for Cr stabilization. • Almost all the Cr in the reduced soil is residual form after sintering at 1000°C. This study explored the effectiveness and mechanisms of high temperature sintering following pre-reduction with ferric sulfate (FeSO₄), sodium sulfide (Na₂S), or citric acid (C₆H₈O₇) in stabilizing hexavalent chromium (Cr(VI)) in highly contaminated soil. The soil samples had an initial total Cr leaching of 1768.83 mg/L, and Cr(VI) leaching of 1745.13 mg/L. When FeSO₄ or C₆H₈O₇ reduction was followed by sintering at 1000°C, the Cr leaching was reduced enough to meet the Safety Landfill Standards regarding general industrial solid waste. This combined treatment greatly improved the stabilization efficiency of chromium because the reduction of Cr(VI) into Cr(III) decreased the mobility of chromium and made it more easily encapsulated in minerals during sintering. SEM, XRD, TG-DSC, and speciation analysis indicated that when the sintering temperature reached 1000°C, almost all the chromium in soils that had the pre-reduction treatment was transformed into the residual form. At 1000°C, the soil melted and promoted the mineralization of Cr and the formation of new Cr-containing compounds, which significantly decreased subsequent leaching of chromium from the soil. However, without reduction treatment, chromium continued to leach from the soil even after being sintered at 1000°C, possibly because the soil did not fully fuse and because Cr(VI) does not bind with soil as easily as Cr(III).     

Removal of chromium (VI) from water streams: a thermodynamic study

The chemical speciation of water solutions containing chromium oxyanions in various ratios is calculated (with the aid of available computer code Mineql Plus, Geochemist Workbench and Visual Minteq) and discussed. The effect of solution pH, total concentration of each species studied, and the presence of other species in solution are calculated and presented in the form of thermodynamic speciation diagrams. Electrochemical diagram (correlating pH to Eh) has been calculated as well. The conditions of Cr(VI) reduction to Cr(III) and the subsequent solid phase precipitation are given as a function of redox potential and pH. Surface reactions that might occur between the chromate ions in the solution and redox couples as Fe²⁺/Fe³⁺ on the surface of sorbents are also discussed. Moreover, experimental sorption data of hexavalent chromium onto synthetic magnetite are presented and discussed with the aid of the calculated diagrams. A mechanism is elucidated for the efficient removal of Cr(VI) from water streams at low pH values, and zeta potential data of synthetic magnetite with and without Cr(VI) are presented, which agree well with the mechanism proposed.     

不同价态铬在不同水分条件下的生物有效性及其对水稻的毒性

氧化还原过程在铬的形态转化中起了重要作用,而铬形态的转化能够影响其生物有效性及毒性。通过温室土培试验研究了六价铬(Cr(Ⅵ))与三价铬(Cr(Ⅲ))在淹水与不淹水条件下在土壤溶液中的动态变化及水稻对其吸收的变化。结果表明,土壤中添加Cr(Ⅲ)时,土壤溶液中检测不出Cr;而随着土壤中添加Cr(Ⅵ)浓度的增加,土壤溶液中Cr(Ⅵ)的浓度增加,但是溶液中检测不出Cr(Ⅲ);淹水处理总体上降低了土壤溶液中Cr(Ⅵ)的浓度。而土壤添加Cr(Ⅲ)、Cr(Ⅵ)和水分处理对土壤溶液p H没有显著影响,p H在7.08.0之间变动。土壤添加Cr(Ⅵ)处理的水稻中,只有90 mg·kg-1Cr(Ⅵ)淹水处理的水稻成活,而其余处理水稻没有成活。土壤中添加Cr(Ⅲ)处理,水稻幼苗生物量随Cr(Ⅲ)浓度的增加而显著降低;除了200mg·kg-1Cr(Ⅲ)处理外,其余淹水处理的水稻幼苗生物量明显高于不淹水处理的。土壤添加Cr(Ⅲ)处理的水稻,在不淹水条件下水稻空壳率比较高,淹水条件下,随着土壤中添加Cr(Ⅲ)浓度水平的增加,水稻各部位Cr含量有增加的趋势,但增加不显著,秸秆最高Cr含量达到33.80 mg·kg-1,籽粒中Cr含量最高0.30 mg·kg-1。土壤固定Cr(Ⅲ)的能力远强于Cr(Ⅵ),添加Cr(Ⅵ)处理的土壤溶液中Cr(Ⅵ)的浓度很高,对水稻表现出较强的生长抑制。     

In-situ monitoring of chromium cytotoxicity in sugarcane

The potential of in-situ monitoring of cytotoxic effects of chromium through root-tip assay was studied in a sugarcane cultivar CoLk 8102 (Saccharum spp. hybrid). Sugarcane setts supplied with graded concentrations of chromium (VI), exhibited a reduction of 85.92 and 95.10 % in mean root length at 40 and 80 ppm Cr dosages along with 61.25 and 82.50% reduction in mean root number/node respectively. Mitotic index of root tip cells of treated setts declined and the frequency of aberrant mitotic phases increased pari passu to the increasing chromium concentration. To compare and quantify the effect of graded chromium dosages on frequency of chromosome aberrations vis-à-vis inhibition of mitotic activity, a 'Decretion factor' (D.F.) has been used for the first time. The value of DF increased with the increase in the chromium dosages. The increase in chromosome aberration frequency was low at low chromium dosages (1 or 2 ppm), but the high Cr dosages (40 and 80 ppm), induced sharp reduction in mitotic efficiency of root system along with anomalies in the process of cell division and induced chromosome aberrations in sugarcane root meristem, which in turn affected the over all plant growth.     

不同pH条件下Cr6+对3种藻的毒性效应(The Toxicological Effects of Cr6+ on Chlorella Vulgaris, Scenedesmus Obliquus and Microcystis Aeruginosa at Different pH Values)

目前我国水质量生态基准的研究较为零星、分散.研究了不同pH条件下Cr6+对3种藻的毒性效应,以期为我国水生态基准的科学制定以及基准的相关研究工作提供参考.选取小球藻、斜生栅藻和铜绿微囊藻3种典型的藻种,在pH为7.0,8.0和9.0三个条件下,依据OECD-201藻类生长抑制实验指南,以72h藻生物量为测试终点,计算3种藻的比生长率,以及Cr6+对3种藻产生毒性效应的NOEC、LOEC、EC10和EC20值.结果表明,在本实验条件下,在不同pH条件下藻种生长不同,小球藻的最适pH值为7.0,斜生栅藻和铜绿微囊藻的最适pH值为9.0;在不同pH条件下,Cr6+对小球藻、斜生栅藻和铜绿微囊藻的毒性作用不同,Cr6+对小球藻在pH=7.0时毒性最小,对斜生栅藻和铜绿微囊藻在pH=9.0时的毒性最小.在藻最适生长的pH条件下,Cr6+的毒性可以达到最小程度;铜绿微囊藻对Cr6+比斜生栅藻和小球藻更加敏感.     

Changes in glucose uptake rate and in the energy status of PC-12 cells acutely exposed to hexavalent chromium,an established human carcinogen

In the 1920s, Otto Warburg reported a striking metabolic shift in solid tumors: contrary to their normal counter parts, which exhibited a nearly pure respiratory metabolism, where cancer cells relied strongly on lactic fermentation for energy production, even in the presence of ample oxygen. This metabolic shift, later named the Warburg effect, is now viewed as a nearly universal cancer phenotype. To investigate whether it is operating in hexavalent chromium (Cr(VI))-induced carcinogenesis, PC-12 cells were exposed to low Cr(VI) concentrations and effects determined on the rates of glucose uptake, lactate production and oxygen consumption, critical indicators of the type of energy metabolism adopted by the cells. Further, the influence on the cells’ energy charge, an important parameter in the evaluation of the cellular physiological state was assessed. In the presence of ample oxygen, concentration-dependent, statistically significant decreases in the energy charge were detected, which were accompanied by an increased glucose uptake rate. This enhanced uptake may constitute the first step in a compensatory mechanism aimed at counteracting the decrease in energy charge. Although these changes may be too small to exert an impact in the cellular functions, they may provide insight into the initial steps of Cr(VI)-induced carcinogenesis.     

Uptake,distribution and loss of Cr in the crab Xantho hydrophilus

Uptake of ⁵¹Cr(III) is faster than uptake of ⁵¹Cr(VI), but it occurs mainly on the surface of the animals. Steady state is attained after 28 d. The resulting concentration factor is about 200. Although the uptake of ⁵¹Cr(VI) is slower, it is more intensively distributed into the organs and tissues of the animals. Steady state was not attained during the experiments (35 d); the highest concentration factor reached was about 10. The uptake of both ⁵¹Cr(III) and ⁵¹Cr(VI) seems to be passive. For both chemical forms of chromium, the loss rate is inversely proportional to the exposure time. When the uptake lasted longer, owing to the distribution of Cr(VI) into the organs and tissues, the loss rate of Cr(III) is somewhat faster relative to the loss rate of ⁵¹Cr(VI). The opposite is the case when the uptake of both forms lasts only two days. On the basis of the distribution and loss experiments, we argue that hexavalent chromium in living organisms is reduced to the trivalent form and then complexed with organic molecules.     

Equilibrium,kinetics and thermodynamics of hexavalent chromium biosorption on pristine and zinc chloride activated Senna siamea seed pods

Hexavalent chromium contamination in water is an issue of huge concern due to its use at a high scale, toxicity and non-biodegradability. Biosorption is a cost effective and unconventional strategy for the elimination of Cr(VI). Here, a novel biosorbent Senna siamea seed pod biomass and its chemically activated form have been investigated for the elimination of hexavalent chromium from aqueous solution. The biosorbent was characterized by using BET, FTIR, FESEM-EDX and TGA techniques. Parameters controlling the biosorption process were optimized as pH 2.0, temperature 30°C, initial Cr(VI) concentration 500?mg/L, biosorbent dose 0.5?g/L. Optimized contact time was 210 and 180 min for pristine biomass and activated carbon, respectively. Langmuir isotherm correlated well with experimental data revealing that the biosorption occurred in monolayer pattern. Maximum biosorption capacity calculated by Langmuir biosorption isotherm was 119.18 and 139.86?mg/g for S. siamea pristine biomass and activated carbon, respectively. Pseudo-second order kinetic model correlated well with experimental data. Thermodynamic studies suggested that the biosorption process occurs in a non-spontaneous, stable and endothermic manner. These interesting findings on Cr(VI) biosorption by S. siamea seed pod biomass and S. siamea zinc chloride activated carbon vouches for its potential application as an unconventional biosorbent.