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PubMed2003

A comparative study of two chelating ion-exchange resins for the removal of chromium(III) from aqueous solution.

Macroporous resins containing iminodiacetic acid (IDA) groups (Lewatit TP 207 and Chelex-100) were investigated as a function of concentration, temperature and pH for their sorption properties towards chromium(III). The chromium(III) ions sorbed onto the resin and in the equilibrium concentration were determined by inductively coupled plasma spectrophotometer. The maximum sorption for chromium ions was observed at pH 4.5. Solution pH had a strong effect on the equilibrium constant of Cr(III). The equilibrium constants were 320 and 7 at pH value 4.5 for Lewatit TP 207 and Chelex-100 resin, respectively. The Langmuir isotherm was used to describe observed sorption phenomena. Both the sorbents had high bonding constants with Lewatit TP 207 showing stronger binding. The equilibrium related to adsorption capacity and energy of adsorption was obtained by using plots of Langmuir adsorption isotherm. It was observed that the maximum adsorption capacity of 0.288 mmol of Cr(III)/g for Chelex-100 and 0.341 mmol of Cr(III)/g for Lewatit TP 207 was achieved at pH of 4.5. The rise in temperature caused a slight increase in the value of the equilibrium constant (K(c)) for the sorption of chromium(III) ion.

Chelating Agents↗
PubMed1996

Ovarian dysfunction in mice following chromium (VI) exposure.

Chromium (VI) was given through drinking water in two sets of adult Swiss albino female mice in three doses; 250 ppm, 500 ppm and 750 ppm for 20 days in set 1 and 0.05 ppm, 0.5 ppm and 5.0 ppm in set II for 90 days. At the termination of the treatment, the animals of both the sets were euthanized for histopathology, follicle counting, counting of the superovulated ova, duration of estrus cycle and for ultrastructural studies. Ovaries of the highest dose group (750 ppm) showed large numbers of atretic follicles and congestion in stromal tissue compared to the rest of the treated groups. Also, there was a dose-dependent reduction in the number of follicles at different stages of their maturation. The number of ova recovered from superovulated chromium (VI)-treated animals showed significant decreases in the 500 and 750 ppm dosed groups compared to lower dosed (250 ppm) and control groups. The duration of estrus cycle increased in highest dosed (750 ppm) group. A dose-dependent increase in blood chromium level was also seen in treated mice. Ultrastructural observations revealed disintegrated cell membranes of two layered follicular cells and altered villiform mitochondria in thecal cells of 5 ppm dosed group. From the study it was concluded that ovarian physiology and rate of ovulation might be altered if females are exposed to sufficiently high chromium through oral route.

Administration, Oral↗
PubMed1998

Embryo and fetotoxicity of hexavalent chromium: a long-term study.

Ingestion of chromium(VI) (250, 500 or 750 ppm as potassium dichromate, K2Cr2O7) through drinking water by female rats for 3 months prior to gestation was toxic to embryo and fetus. There was a significant reduction in number of implantations and number of fetuses and an increase in number of resorptions and pre-implantation and post-implantation losses. No significant visceral abnormality was found. The increase in the number of subdermal hemorrhagic patches on the thorax and abdomen was significant. Skeletal abnormality in the form of reduced ossification in parietal, interparietal and caudal bones was observed in fetuses. Chromium levels in the blood of mothers, placenta and fetuses showed a significant increase. Duration of the estrous cycle was also increased significantly. The study revealed that long-term chromium exposure in rats did not cause embryo and fetotoxicity in a duration-dependent manner compared to short-term treatment as observed earlier. A possible explanation could be that, in the 90-day study, the female rats did not mate for three estrous cycles, thus giving time for clearance of a sizable amount of chromium from their bodies.

Abnormalities, Drug-Induced↗
PubMed2003

On-line preconcentration and determination of chromium in parenteral solutions by flow injection-flame atomic absorption spectrometry.

An on-line chromium preconcentration and determination system implemented with flame atomic absorption spectrometry (FAAS) associated to flow injection (FI) was studied. For the retention of chromium, 4-(2-Thiazolylazo)-resorcinol (TAR) and Amberlite XAD-16 were used, at pH 5.0. The Cr-TAR complex was removed from the micro-column with ethanol. An enrichment factor of 50 was obtained for the preconcentration of 50 ml of sample solution. The detection limit value for the preconcentration of 50 ml of aqueous solution of Cr was 20 ng l(-1). The precision for ten replicate determinations at the 5 microg l(-1) Cr levels was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for chromium was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 microg l(-1). The method was successfully applied to the determination of chromium in parenteral solution samples.

Buffers↗
PubMedDate not supplied

Semen quality of Indian welders occupationally exposed to nickel and chromium.

The semen quality of 57 workers from a welding plant in South India and 57 controls was monitored. Blood nickel and chromium concentrations were determined by ICP-MS. Analysis of semen samples was performed in accordance with World Health Organization criteria. The blood level of nickel and chromium for the 28 exposed workers was 123.3 +/- 35.2 and 131.0 +/- 52.6 microg/l, resepctively, which was significantly higher than the 16.7 +/- 5.8 and 17.4 +/- 8.9 microg/l for the control group (n=27). Sperm concentrations of exposed workers were 14.5 +/- 24.0 millions/ml and those of the control group were 62.8 +/- 43.7 millions/ml. Rapid linear sperm motility was decreased in exposed workers compared to controls. There was a significant positive correlation between the percentage of tail defects and blood nickel concentration in exposed workers. The sperm concentration showed a negative correlation with blood chromium content in workers. More abnormal characteristics were found in the semen of exposed workers. Semen abnormalities correlated with the number of years of exposure to welding fumes containing nickel and chromium.

Adult↗
PubMed2003

Various cells of the immune system and intestine differ in their capacity to reduce hexavalent chromium.

The cells of the immune system form a strong line of defence against foreign substances. The present study was undertaken to investigate the capacity of different cells of Wistar rats to reduce potentially carcinogenic hexavalent chromium (Cr-VI) into less toxic trivalent chromium in vitro. 5 x 10(6) cells were incubated with 10 or 25 microg ml(-1) of Cr (VI) in the form of K2Cr2O7 at 37 degrees C in the presence of 5% CO2 in air. At various time periods the remaining amount of Cr (VI) was measured and the percentage of Cr (VI) reduced was calculated. Among the single cell suspensions from the splenic cells a peak reduction of 55% was observed with the total spleen cells, 40% with the B-lymphocyte-enriched subpopulation, 10% with T-lymphocytes and 24% with the macrophages. The reduction by splenic and peritoneal macrophages was similar. Total thymocytes reduced 54% of the Cr (VI). Since the most common route of entry of chromium is through drinking water and food, intestinal cells were also investigated. Among the intestinal cells the maximum reduction of 100% (of 10 microg ml(-1)) was observed with the upper villus cells and 72% with the middle villus cells while reduction was the least (4%) with the crypt cells. The reduction in the intestinal loop in situ was 100%. The time taken by each cell type for the peak reduction to Cr (VI) was markedly different. The findings thus show that the capacity of different cells in the body differs vastly in their capacity and time taken to reduce hexavalent chromium. The most efficient handling of Cr (VI) by the intestine, due to the presence of a variety of cells and bacteria, protects the body from its adverse effects.

Animals↗
PubMed2001

Effects of the type of sintering atmosphere on the chromium leachability of thermal-treated municipal solid waste incinerator fly ash.

The sintering process offers an opportunity to combine detoxification and resource recovery for the treatment of municipal solid waste (MSW) incinerator fly ash. However, the chromium (Cr) in the sintered fly ash becomes more readily leachable with increasing sintering time and temperature, thus posing severe threats to the environment and human health when the sintered ash is recycled or reused. This study investigated the enhanced leachability of fly ash containing Cr, by heating the chromium (III) oxide (Cr2O3)-spiked fly ash to 800 degrees C in atmospheres containing air, nitrogen gas (N2), and 5% H2 + 95% N2, respectively. The results indicated that trivalent chromium was converted to its soluble hexavalent form during sintering in the air atmosphere; whereas sintering in a nitrogen atmosphere significantly reduced the leachability of Cr due to lack of oxygen (O2) to oxidize. The effects of the sintering temperature on the total chromium content and the leaching concentration in the toxicity characteristic leaching procedure (TCLP) extract are also discussed.

Air Pollutants↗
PubMed2003

Environmental evaluation of different variants of the chromium compound production model using chromic waste.

This work presents research results on the evaluation of environmental effects of utilizing chromic waste in chromium compound production processes. The comprehensive evaluation of three chromium compound production models takes into consideration the total cumulated hazard coefficients. The implementation of the new chromium compound production model into industrial practice in 1999 allows the hazard to the natural environment to decrease by 75% in relation to the hazard caused by the old production model used until 1995. The coefficient of the target chromium compound production model was 199%, much higher than 100%. This results from the negative values of the total cumulated hazard coefficients for those cases where the sodium chromate production unit could be a big "consumer" of chromic waste.

Chromium↗
PubMed2003

Removal of hexavalent chromium using distillery sludge.

Batch mode experiments were conducted to study the removal of hexavalent chromium from aqueous and industrial effluent using distillery sludge. Effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(VI) were studied. The data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity was found to be 5.7 mg/g. Freundlich constants K(f) and n were 2.05 [mg/g(L/mg)(n)] and 3.9, respectively. Desorption studies indicated the removal of 82% of the hexavalent chromium. The efficiency of adsorbent towards the removal of chromium was also tested using chromium-plating wastewater.

Adsorption↗
PubMed2001

K-ras mutations in mouse lung tumors of extreme age: independent of paternal preconceptional exposure to chromium(III) but significantly more frequent in carcinomas than adenomas.

Preconceptional exposure of male NIH Swiss mice to chromium(III) chloride resulted in increased incidence of neoplastic and non-neoplastic changes in their progeny, including lung tumors in females [Toxicol. Appl. Pharmacol. 158 (1999) 161-176]. Since mutations in the K-ras protooncogene are frequent, early changes in mouse lung tumors, we investigated possible mutational activation of this gene as a mechanism for preconceptional carcinogenesis by chromium(III). These offspring had lived until natural death at advanced ages (average 816+/-175 days for controls, 904+/-164 for progeny of chromium-treated fathers). Mutations of K-ras, analyzed by single-strand conformation polymorphism and sequencing, were, in codon 12, wild type GGT (glycine), to GAT (aspartic acid); to GTT (valine); and to CGT (arginine); and in codon 61, wild-type CAA (glutamine), to CGA (arginine). K-ras mutation frequencies in lung tumors were very similar in control progeny (4/14) and in progeny of chromium-treated fathers (5/15). Thus, germline mutation or tendency to spontaneous mutation in K-ras does not seem to be part of the mechanism of preconceptional carcinogenesis here. However, an additional interesting observation was that K-ras mutations were much more frequent in lung carcinomas (8/16) than in adenomas (1/13) (P=0.02), for all progeny combined. This was not related to age of the tumor-bearing mice or the size of the tumors. K-ras mutations may contribute to malignant tumor progression during aging, of possible relevance to the putative association of such mutations with poor prognosis of human lung adenocarcinomas.

Adenoma↗
PubMed2001

Effect of chlorophyllin on chromium trioxide-induced micronuclei in polychromatic erythrocytes in mouse peripheral blood.

The effect of chlorophyllin on micronucleated polychromatic erythrocytes (MN-PCE) induction by chromium trioxide (CrO(3)) exposure in peripheral blood of mice was studied. Animals were treated with a single intraperitoneal dose of chlorophyllin (CHL) (20mg/kg), CrO(3) (20mg/kg), and CHL (20mg/kg) 4h before (CHL-CrO(3)) or 4h before and 20h after chromium treatments (20mg/kg; CHL-CrO(3)-CHL). Peripheral blood samples were drawn from the caudal vein at 0, 12 and 48h, and analyzed by the acridine orange (AO) technique. The results obtained in present study shown that CHL injection did not modify the number of MN-PCE. CrO(3) treatment resulted in a significantly increases 12 and 48h after the injection, reaching a four-fold increase 48h after CrO(3) administration. Whereas treatment with 20mg/kg of CHL prior to chromium, decreased the MN frequency induced by chromium in the 12h samples. When the samples were analyzed 48h after CrO(3) injection, no significant differences between CHL-CrO(3) and CHL-CrO(3)-CHL in comparison with CrO(3) treatment, were observed. These results indicate that increase of MN-PCE by CrO(3) is CHL-blocked in both protocols used (CHL-CrO(3) and CHL-CrO(3)-CHL) at 12h after treatment, but it was unable to modify the frequency of MN-PCE measured 48h after CrO(3) injection. The absence of a protective effect by CHL in the MN-PCE induction by CrO(3) at 48h, show that CHL has action only on one of the times of MN induction and suggests the possible action of CrO(3) by two different mechanisms, and not by CHL time-limited in vivo.

Animals↗
PubMed2003

Determination of chromium in urine samples by complexation-supercritical fluid extraction and liquid or gas chromatography.

A method was developed for the determination of chromium as the Cr(acac)(3) complex in urine using SFE and chromatography. Quantitative extractions were achieved when the experiments were carried out under 3000 p.s.i. of pressure, at a temperature of 120 degrees C, with 2.0 ml of methanol, 30 min of static extraction and 5 min of dynamic extraction. The chromium was quantified by GC-FID detection. The calibration graph of Cr(acac)(3) solutions was linear between 0.50 and 43.0 microg ml(-1) of chromium (DL 0.18 microg ml(-1), R=0.9994). The same extracts were quantified by HPLC-340 nm detection. The calibration curve of the Cr(acac)(3) solutions was linear over a range of 0.013 to 60.0 microg ml(-1) (DL 0.02 microg ml(-1), R=0.9999). This method was applied to urine samples from 60 diabetic patients and 21 healthy volunteers. Chromium concentration ranges were 2.5-29.5 microg l(-1) for the diabetics and 5.9-12.3 microg l(-1) for the normal subjects.

Adult↗
PubMed1990

Determination of chromium in urine by stable isotope dilution gas chromatography/mass spectrometry using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent.

An isotope dilution gas chromatography/mass spectrometry method using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described for the determination of chromium in urine. A wet digestion procedure with HNO3-H2O2 is used for oxidizing the organic matter associated with urine samples. The isotope ratios are measured by selected ion monitoring in a general-purpose mass spectrometer using a 10-m fused silica capillary column. Memory effect, in sequential analyses of samples with different isotope ratios, was evaluated by preparing a series of synthetic mixtures and was found to be negligible. The accuracy of the method was verified by quantitation of chromium in the NIST freeze-dried urine reference material, SRM-2670, with a recommended chromium concentration of 13 micrograms/L in the normal level and certified chromium concentration of 85 +/- 6 micrograms/L in the elevated level.

Chelating Agents↗
PubMed1999

Field method for the determination of hexavalent chromium by ultrasonication and strong anion-exchange solid-phase extraction.

A simple, fast, sensitive, and economical field method was developed and evaluated for the determination of hexavalent chromium (CrVI) in environmental and workplace air samples. By means of ultrasonic extraction in combination with a strong anion-exchange solid-phase extraction (SAE-SPE) technique, the filtration, isolation, and determination of CrVI in the presence of trivalent chromium (CrIII) and potential interferents was achieved. The method entails (1) ultrasonication in basic ammonium buffer solution to extract CrVI from environmental matrixes; (2) SAE-SPE to separate CrVI from CrIII and interferences; (3) elution/acidification of the eluate; (4) complexation of chromium with 1,5-diphenylcarbazide; and (5) spectrophotometric determination of the colored chromium-diphenylcarbazone complex. Several critical parameters were optimized in order to effect the extraction of both soluble (K2CrO4) and insoluble (PbCrO4) forms of CrVI without inducing CrIII oxidation or CrVI reduction. The method allowed for the dissolution and purification of CrVI from environmental and workplace air sample matrixes for up to 24 samples simultaneously in less than 90 min (including ultrasonication). The results demonstrated that the method was simple, fast, quantitative, and sufficiently sensitive for the determination of occupational exposures of CrVI. The method is applicable for on-site monitoring of CrVI in environmental and industrial hygiene samples.

Air Pollutants, Occupational↗
PubMed1996

A biologically active form of chromium may activate a membrane phosphotyrosine phosphatase (PTP).

Chromium is essential for proper carbohydrate and lipid metabolism in mammals, although the mechanism of this action has previously proved elusive. Low-molecular-weight chromium-binding protein (LMWCr), a biologically active form of chromium in mammals, potentiates the effect of insulin on the conversion of glucose into lipid and into carbon dioxide in isolated adipocytes. Kinetics studies indicate that LMWCr isolated from bovine liver activates phosphotyrosine phosphatase (PTP) activity in adipocyte membranes while having no intrinsic phosphatase activity. This activation is directly proportional to the amount of added LMWCr. The pattern of inhibition of this activity in the presence of a number of known phosphatase inhibitors suggests the involvement of a membrane phosphotyrosine phosphatase similar to PTP1A' or PTP1B. We propose that chromium plays a biological role in the activation of a membrane phosphotyrosine phosphatase.

Adipocytes↗
PubMed1997

Chromium oligopeptide activates insulin receptor tyrosine kinase activity.

A possible new mechanism for the amplification of insulin receptor tyrosine kinase activity in response to insulin has been identified. The chromium-containing oligopeptide low molecular weight chromium-binding substance (LMWCr) does not effect the tyrosine protein kinase activity of rat adipocytic membrane fragments in the absence of insulin; however, insulin-stimulated kinase activity in the membrane fragments is increased up to 8-fold by the oligopeptide. Using isolated rat insulin receptor, LMWCr has been shown to bind to insulin-activated insulin receptor with a dissociation constant of circa 250 pM, resulting in the increase of its tyrosine protein kinase activity. The ability of LMWCr to stimulate insulin receptor tyrosine kinase activity is dependent on its chromium content. The results appear to explain the previously poorly understood relationship between chromium and adult-onset diabetes and cardiovascular disease.

Adipocytes↗
PubMed1998

Chromium(III) decreases the fidelity of human DNA polymerase beta.

Certain particulate compounds of hexavalent chromium are well-known occupational and environmental human carcinogens. Hexavalent chromium primarily enters the cells and undergoes metabolic reduction; however, the ultimate trivalent oxidation state of chromium, Cr(III), predominates within the cell. DNA-bound Cr(III) has been previously shown to decrease the fidelity of replication in the M13 phage mutation assay. This study was done to understand how Cr(III), in the presence of physiological concentrations of magnesium, affects the kinetic parameters of steady-state DNA synthesis in vitro across site-specific O6-methylguanine (m6dG) residues by DNA polymerase beta (pol beta). Cr(III) binds to the short oligomer templates in a dose-dependent manner and stimulates the activity of pol beta. Cr(III) stimulates the mutagenic incorporation of dTTP opposite m6dG more than the nonmutagenic incorporation of dCTP, and thereby Cr(III) further decreases the fidelity of DNA synthesis across m6dG by pol beta. In contrast, Cr(III) does not affect the fidelity of DNA synthesis across the normal template base, dG. Both the enhanced activity and the mutagenic lesion bypass in the presence of Cr(III) may be associated with Cr(III)-dependent stimulation of pol beta binding to DNA as reported here. This study shows some of the mechanisms by which mutagenic chromium affects DNA synthesis.

Binding Sites↗
PubMed2001

Behavior of hexavalent chromium in a polluted groundwater: redox processes and immobilization in soils.

This work describes the chemical mechanisms governing transport and reduction of hexavalent chromium in soils of a contaminated industrial waste landfill. Groundwater and soil analyses indicate that the main source of chromium is a slag heap essentially consisting of mill tailings. In the groundwater, downstream migration of Cr(IV) is limited thanks to a redox mechanism involving chromate ions and ferrous ions or Fe(II)-bearing minerals. High Fe2+ concentrations in the groundwater are a result of pyrite residues from old activities at the site. Analyses of soil samples reveal that chromium is preferentially located in the soil profile at the fluctuation of the groundwater level. Grain size fractionation of four soil samples was performed, and fraction analyses show that chromium is preferentially accumulated in the clay fraction (<2 microm) and more specifically associated with montmorillonite particles. This work is a demonstration of the reduction of Cr(VI) by Fe(II) studied previously in the laboratory (Buerge, I. J.; Hug, S. J. Environ. Sci. Technol. 1997, 31, 1426-1432; Fendorf, S. E.; Li, G. Environ. Sci. Technol. 1996, 30, 1614-1617; Sedlak, D. L.; Chan, P. G. Geochim. Cosmochim. Acta 1997, 11, 2185-2192) in a field setting. Cr(VI) migration into the groundwater is stopped vertically by the very thick green clay unit and horizontally by the presence of Fe(II) acting as a chemical barrier. The specific site conditions safely prevent any extension of the Cr pollution.

Carcinogens, Environmental↗