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PubMed2003

Chromium species behaviour in the activated sludge process.

The purpose of this research was to compare trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) removal by activated sludge and to investigate whether Cr(VI) reduction and/or Cr(III) oxidation occurs in a wastewater treatment system. Chromium removal by sludge harvested from sequencing batch reactors, determined by a series of batch experiments, generally followed a Freundlich isotherm model. Almost 90% of Cr(III) was adsorbed on the suspended solids while the rest was precipitated at pH 7.0. On the contrary, removal of Cr(VI) was minor and did not exceed 15% in all experiments under the same conditions. Increase of sludge age reduces Cr(III) removal, possibly because of Cr(III) sorption on slime polymers. Moreover, the decrease of suspended solids concentration and the acclimatization of biomass to Cr(VI) reduced the removal efficiency of Cr(III). Batch experiments showed that Cr(III) cannot be oxidized to Cr(VI) by activated sludge. On the contrary, Cr(VI) reduction is possible and is affected mainly by the initial concentration of organic substrate, which acts as electron donor for Cr(VI) reduction. Initial organic substrate concentration equal to or higher than 1000 mgl(-1) chemical oxygen demand permitted the nearly complete reduction of 5 mgl(-1) Cr(VI) in a 24-h batch experiment. Moreover, higher Cr(VI) reduction rates were obtained with higher Cr(VI) initial concentrations, expressed in mg Cr(VI) g(-1) VSS, while decrease of suspended solids concentration enhanced the specific Cr(VI) reduction rate.

Adsorption↗
PubMed2003

Cadmium, chromium and lead contamination of Athene noctua, the little owl, of Bologna and Parma, Italy.

A study was conducted to determine cadmium, chromium and lead concentrations in liver and brain of 52 little owls (Athene noctua) from two provinces of Emilia Romagna region, with the aim of furnishing indirect information concerning contamination of their habitat, also considering possible environmental dispersion of the metals. Metal analysis was performed by atomic absorption spectrophotometry with graphite furnace. Variance analysis with sampling area, gender and age shows that no statistical difference was found for gender, while a significant difference (P<0.05) was found for cadmium and lead, but not for chromium, when sampling areas and age were of concern. For all metals highest mean concentrations were found in liver (170 ppb for cadmium, 297 ppb for chromium and 312 ppb for lead). These levels can be considered as indicative of chronic exposure to low and "background" amounts of pollutants and they are of no toxicological concern, as they are always well below the toxic thresholds defined for each metal. The present study can be considered as a starting point for further analyses, aimed to the definition of any possible subtle effect (e.g. effects on enzymes activity) and of any possible correlation between levels of pollutants and appearance of possible adverse effects. It also furnished useful data for diagnostic cases and potentially for monitoring local contamination.

Animals↗
PubMed1998

The simulation of hexavalent chromium formation under various incineration conditions.

The formation of hexavalent chromium Cr(VI) during waste incineration processes is of interested because its carcinogenic characteristic. The objective of this study is to simulate the formation of Cr(VI) species under various operating temperatures and input waste compositions during incineration by a thermodynamic model. The results show that the major hexavalent chromium species are CrO2Cl2(g) and CrO3(g). Chlorine and oxygen can increase the formation of Cr(VI) species; while hydrogen, sulfur, sodium, and calcium can inhibit. The input waste composition has greater effect on the formation of hexavalent chromium species than operating temperature.

Calcium↗
PubMed2003

The effect of frictional heating and forced cooling on the serum lubricant and wear of UHMW polyethylene cups against cobalt-chromium and zirconia balls.

Hip simulator tests of femoral balls of cobalt-chromium alloy or zirconia against acetabular cups of UHMW polyethylene were run with and without a coolant circulated inside the femoral balls. Without cooling, the wear of polyethylene against zirconia was about 48% lower than with cobalt-chromium alloy, but the steady-state temperature of the zirconia ball was higher (55 degrees C vs. 41 degrees C), and there was more precipitation of protein from the serum, which sometimes formed an adherent layer on the surface of the zirconia. Circulating coolant at 1-20 degrees C markedly reduced the bearing temperatures and the protein precipitation. With coolant at 4 degrees C, wear of the polyethylene against cobalt-chromium alloy was about 26% lower than against zirconia, but the macroscopic and microscopic appearance of the worn polyethylene surfaces were unlike that typically generated in vivo. With or without coolant, the morphology of the polyethylene wear debris was comparable to that generated in vivo, but the ratio of fibrillar to granular debris was higher at the reduced temperature. These results suggested that circulating coolant at an appropriate temperature could avoid overheating (due to non-stop running of the simulator), preventing excessive protein precipitation while providing wear surfaces and wear debris with morphologies closely comparable to those generated in vivo.

Artifacts↗
PubMed2005

[Chromium-induced vasculitis-like purpuric allergic contact dermatitis].

INTRODUCTION: Purpuric allergic contact dermatitis is a rare and poorly understood condition. CASE REPORT: A 27-year-old male patient with a personal history of atopic dermatitis since childhood consulted for chronic papular-purpuric rash present for 7 years. Moderate pruritus was seen. Profuse lesions were observed on the palms and soles and on the upper and lower limbs, with sparing of the trunk. These lesions consisted of purpuric papules, in some cases with crusts, forming large plaques. The clinical picture was initially suggestive of vasculitis, but this diagnosis was ruled out by histological examination and laboratory tests. Skin patch tests were evocative of chromium-induced contact dermatitis. Retrospective directed history-taking confirmed the relevance of the latter test since it revealed regular wearing of leather clothing. Lasting cure was achieved following eradication of the allergen. DISCUSSION: Reports of contact purpuric dermatitis are rare. This condition has been described principally for allergens consisting of rubber or dyes used in clothing. Our case was notable on account of the severity of the lesions, mimicking vasculitis, as well as the novelty of the incriminated allergen, chromium, found in leather garments. It underlines the value of routine skin patch tests in the event of chronic non-specific dermatitis. To our knowledge, this is the first reported case of chromium-induced purpuric allergic contact dermatitis.

Adult↗
PubMed1982

Kinetics of chromium nucleotide isomer interconversion.

The rates of chromium nucleotide isomer interconversion were studied as a function of pH, ionic strength, and temperature. Nucleotide isomers were separated using high voltage electrophoresis and gel filtration chromatography. The rate of conversion of monodentate adenosine 5'-monophosphate-chromium salt (CrADP) to the bidentate complex increased with increasing pH, temperature, and ionic strength. Optimal stability for CrADP complexes was found to be at pH 3.5 with a temperature of 4 degrees C. It was found that at pH values above 7.0, the chromium complexes rapidly decomposed even at 4 degrees C. It was found that the conversion of monodentate CrADP to binentate CrADP required the removal of one proton by the solvent. The activation energy for the conversion was found to be 7.3 kcal/mol at pH 6.5. The kinetics of the isomer interconversion are described in terms of possible conversion mechanisms.

Adenine Nucleotides↗
PubMed2001

Kinetics of chromium (VI) reduction by a type strain Shewanella alga under different growth conditions.

We conducted kinetic batch experiments to determine the reduction of Chromium(VI) by a type strain of Shewanella alga (BrY-MT) ATCC 55627. Chromium(VI) was reduced to Chromium(III) by BrY-MT grown in three different substrates: BHIB (brain heart infusion broth), TSB (tryptic soy broth), and M9 (minimum broth). Four different Cr(VI) concentrations 4.836, 10.00, 37.125, and 260.00 mg l-1 were reduced at different rates by BrY-MT in both aerobic and anaerobic conditions. BrY-MT grown in BHIB reduced the maximum amount of Cr(VI) followed by TSB and M9. Carbondioxide produced from bacterial respiration varied with and without Cr(VI) under both aerobic and anaerobic conditions. The Cr(VI) reduction data under anaerobic condition was fitted by a monod model to determine the bacterial kinetic parameters. The kinetic parameters determined by fitting the anaerobic experimental data were used to run a forward simulation for experiments conducted under aerobic conditions. The monod model was modified to account for an inhibition parameter for the Cr(VI) experiment at 260 mg l-1. All the parameters varied within a narrow range, and were distinct for different substrates. Our studies show that, successful in situ bioremediation of Cr(VI) is depended on the type of substrates (electron donors) and the concentration of Cr(VI) in geologic medium.

Aerobiosis↗
PubMed2002

Photochemical reduction of hexavalent chromium in glycerol-containing solutions.

Hexavalent chromium [Cr(VI)] in the form of potassium dichromate was photochemically reduced to trivalent chromium [Cr(III)] in aqueous solutions containing glycerol. This reaction occurred rapidly during irradiation with either unfiltered sunlight or a UVA-emitting light source. Photochemical reduction of Cr(VI) was pH-dependent and did not occur in dilute solutions of sodium hydroxide. In acidified solutions, the reduction occurred at elevated rates and at lower concentrations of glycerol. This reaction was found to be dependent on the unsubstituted alcohol groups of glycerol since alpha-phosphoglycerol and beta-phosphoglycerol did not support the photochemical reduction of Cr(VI). These findings suggest that glycerol or related polyols can be used for the remediation of hexavalent (toxic) chromium at contaminated environmental sites.

Carcinogens, Environmental↗
PubMed2001

Nickel, cobalt and chromium-induced cytotoxicity and intracellular accumulation in human hacat keratinocytes.

Nickel, cobalt and chromium can induce allergic contact dermatitis (ACD) and may provoke irritant reactions in the skin. This study aimed at investigating cytotoxicity and cell viability along with intracellular metal accumulation in HaCaT human keratinocytes exposed to soluble forms of nickel, cobalt or chromium. The EC50 (24 h) values as detected by MTT test were 30 microM for sodium chromate (Na2CrO4), 475 microM for cobalt chloride (CoCl2) and 600 microM for nickel chloride (NiCl2). Chromium chloride (CrCl3) was not toxic up to 1 mM. No clear effects were observed after 4 h, but 24-h treatments with 1 mM CoCl2 or 10 microM Na2CrO(4) were found to almost completely abolish the ability of the cells to form colonies, whilst 1 mM NiCl2 reduced cellular survival to only 70% of control cultures. Intracellular accumulation of metals was evaluated by the use of radioisotopes at the EC50 value and at 1/10-1/5 of this concentration. Accumulation of Na2(51)CrO4 was linear with increasing dose. This was not the case for 63NiCl2 and 58CoCl2. All the metals were accumulated preferentially in the cytosols; 96% or more for 63NiCl2, approximately 90% for 58CoCl2 and 60-70% for Na2(51)CrO4. Finally, it was observed that HaCaT human keratinocytes can concentrate the metals present in the media up to 3.9 and 12.5 times for NiCl2 and CoCl2, respectively, and up to 167 for Na2CrO4. These striking metal intracellular accumulation patterns, which have not been earlier described in keratinocytes, highlight the relevance of searching for specific biomarkers of early cellular toxic effects, such as cytosolic proteins that bind the metals.

Cell Line↗
PubMed1997

Trivalent chromium and the diabetes prevention program.

The Diabetes Prevention Program is a new, 150 million dollar, NIH-sponsored study designed to determine whether non-insulin-dependent diabetes mellitus can be prevented or delayed in persons with impaired glucose tolerance. Four thousand subjects will be randomly assigned to one of four study groups and followed for 4.5 years. Study groups include intensive lifestyle intervention with diet and exercise; metformin (Glucophage) or troglitazone (an investigational drug) with standard diet and exercise; and a control group. Insulin resistance is an important pathogenic factor in impaired glucose tolerance. Trivalent chromium, a dietary supplement that potentiates the action of insulin, was not included in the program. Like metformin and troglitazone, trivalent chromium decreases insulin resistance and has an acceptable side-effect profile; furthermore, it is available at a fraction of their cost. Trivalent chromium should have been included in the Diabetes Prevention Program; it is unfortunate that it was omitted.

Chromans↗
PubMed1997

Salivary nickel and chromium in subjects with different types of fixed orthodontic appliances.

The aim was to investigate nickel and chromium concentrations in saliva of patients with different types of fixed appliances. Saliva samples were collected from 47 orthodontic patients, ages 8 to 30 years. Four samples from each subject were collected: (1) before insertion of the appliance, (2) 1 to 2 days after, (3) 1 week after, and (4) 1 month after insertion of the appliance. A considerable variation in the concentrations of both nickel and chromium was observed. No significant differences were found between the no-appliance samples and the samples obtained after insertion of the appliances. The results suggest that nickel and chromium concentrations of saliva are not significantly affected by fixed orthodontic appliances during the first month of treatment.

Adolescent↗
PubMed2002

Chromium(III)-induced apoptosis of lymphocytes: death decision by ROS and Src-family tyrosine kinases.

Apoptosis is an active process induced by a variety of physiological and external stimuli, in which elimination of damaged cells are effected through a genetically controlled process. In this study, we have examined the mechanism of chromium(III) [Cr(III)]-induced cytotoxicity with respect to its relationship to oxidative stress. Morphology, flow cytometry, and DNA fragmentation studies show that tris-(1,10-phenanthroline)chromium(III) [Cr(III)-phen], tris-(2,2'-bipyridyl)chromium(III) [Cr(III)-bpy], trans-diaqua[1,2-bis(salicylideneamino)ethanechromium(III)] [Cr(III)-salen], and trans-diaqua[1,3-bis(salicylideneamino)propanechromium(III)] [Cr(III)-salprn] induced apoptosis of lymphocytes. Pentaammineaquachromium(III) [Cr(III)-hpa] does not induce apoptosis. Apoptosis induced by these complexes involves the generation of reactive oxygen species (ROS) as seen by increased fluorescence of dichloroflourescein (DCF) observed through flow cytometry. Pretreatment of lymphocytes with antioxidants completely abrogate apoptosis. Cr(III) treatment also increased the expression and activation of Src-family tyrosine kinases viz. p56lck, p59fyn, and p53/56lyn, as seen by immunoblotting and immune complex kinase assay. PP2, a selective Src-family tyrosine kinase inhibitor, abolishes apoptosis, indicating that Src-family tyrosine kinases are directly involved in eliciting apoptosis. Interestingly, a one-to-one correlation between the expression of Src-family tyrosine kinases and ROS is observed, since antioxidants pretreatment inhibits the expression and the activation of these kinases. These results further indicate that Cr(III)-induced apoptosis is mediated through production of ROS, which in turn activates the Src-family tyrosine kinases. The increased activation of Src-family tyrosine kinases may be a mechanism involved in apoptosis of lymphocytes elicited by various other physiological stimuli that exploit ROS as a second messenger.

Adenosine Triphosphate↗
PubMed2002

Determination of chromium in cerebrospinal fluid using electrothermal atomisation atomic absorption spectrometry.

A rapid method to determine the chromium content of cerebrospinal fluid (CSF) samples using electrothermal atomization atomic absorption spectrometry (ETA-AAS) with deuterium-arc background correction is described. The chromium concentration in CSF was evaluated by the standard addition method. Sample dilution (1 + 1) with 0.25% (m/v) Triton X-100 and 4.5% (v/v) HNO3 gave the best combination of sensitivity, reproducibility, and low blank reading compared with dilution using other solvents. Within-batch reproducibility was 3.2% for 20 CSF samples, between-batch reproducibility was 4.7%. CSF samples from 43 healthy volunteers collected in a manner designed to avoid contamination yielded chromium concentrations of 14.6 +/- 6.3 ng mL(-1).

Calibration↗
PubMed2003

Removal of copper, chromium, and arsenic from CCA-C treated wood by EDTA extraction.

Ethylenediaminetetracetic acid (EDTA) is one of the most common chelators used to bind the metal ions in extremely stable complexes in heavy metal contaminated soils and thus to remediate such substrates. EDTA forms water soluble complexes with many metal ions and it is used to release the various metals. In this study, EDTA extraction of copper, chromium, and arsenic from chromated copper arsenate (CCA-C) treated wood was evaluated using batch leaching experiments. CCA-treated wood samples were extracted with eight different concentrations of EDTA for 4, 8, 18, and 24 h at room temperature. Exposing CCA-treated chips and sawdust to EDTA extraction enhanced removal of CCA components compared with extraction by deionized water. Grinding CCA-treated wood chips into 40-mesh sawdust provided greater access to and removal of CCA components. Extraction with 1% EDTA solution for 24 h removed 60% copper, 13% chromium, and 25% arsenic from treated chips. EDTA extraction of treated sawdust samples resulted in 93% copper, 36% chromium, and 38% arsenic removal. CCA leaching from treated wood blocks was also evaluated according to modified AWPA E11-99 standard test method of determining the leachability of wood preservatives. Leaching of CCA components from treated wood blocks with 1% EDTA solution for 14 days caused more copper leaching compared to leaching with deionized water. Leaching with 1% EDTA for 14 days removed 53% copper from the blocks whereas 14% copper was leached from the blocks with deionized water. The results suggest that EDTA extraction removes significant quantities of copper from CCA-treated wood. Thus, EDTA could be important in the remediation of wood waste treated with the newest formulations of organometalic copper compounds and other water-borne wood preservatives containing copper.

Arsenic↗
PubMed2003

Towards zero discharge of chromium-containing leather waste through improved alkali hydrolysis.

The treatment of chromium-containing leather waste (CCLW), the major solid waste generated at the post-tanning operations of leather processing, has the potential to generate value-added leather chemicals. Various alkali and enzymatic hydrolysis were compared, and calcium oxide was found to be important for effective (but still incomplete) hydrolysis. Three possible reasons are given for the incomplete hydrolysis under alkaline conditions. Data for 19 amino acids are presented for four different treatment products. On the basis of the results, a novel three-step CCLW treatment process is proposed. The gelatin extracted in the first step is chemically modified to produce leather finishing agents. The collagen hydrolysates isolated in the second step are used as proteinic retanning agents by chemical modification. The remaining chrome cake is further hydrolyzed with acids in the third step, and the obtained chromium-containing protein hydrolysates could be used for the preparation of chromium-containing retanning agents for leather industry. The proposed three-step process provides a feasible zero discharge process for the treatment of CCLW.

Animals↗
PubMed2002

Biosorption of chromium(VI) from aqueous solution by cone biomass of Pinus sylvestris.

Biosorption of chromium(VI) on to cone biomass of Pinus sylvestris was studied with variation in the parameters of pH, initial metal ion concentration and agitation speed. The biosorption of Cr(VI) was increased when pH of the solution was decreased from 7.0 to 1.0. The maximum chromium biosorption occurred at 150 rpm agitation. An increase in chromium/biomass ratio caused a decrease in the biosorption efficiency. The adsorption constants were found from the Freundlich isotherm at 25 degrees C. The cone biomass, which is a readily available biosorbent, was found suitable for removing chromium from aqueous solution.

Adsorption↗
PubMed2002

Assessment of cytogenetic damage in lymphocytes and in exfoliated nasal cells of dental laboratory technicians exposed to chromium, cobalt, and nickel.

Dental laboratory technicians may be exposed to metal alloys that are used in the production of crowns, bridges and removable partial dentures. These alloys consist of 35-65% cobalt, 20-30% chromium, 0-30% nickel, and small amounts of molybdenum, silica, beryllium, boron and carbon. The aim of this study was to assess whether dental technicians are occupationally exposed to chromium, cobalt and nickel, by analyzing urinary excretion levels of these metals and to investigate the genotoxic effects of occupational exposure associated with dental prostheses production operations by analyzing cytokinesis-blocked micronucleus (CB-MN) frequencies in peripheral lymphocytes and micronucleus (MN) frequencies in exfoliated nasal cells from 27 dental laboratory technicians and 15 control subjects. The differences in the urinary excretion of metals between technicians and controls were statistically significant. The mean (+/-S.D.) CB-MN frequencies ( per thousand ) in peripheral lymphocytes were 4.00 (+/-2.98) among the dental technicians and 1.40 (+/-1.30) among the controls, a statistically significant difference (P<0.005). The mean (+/-S.D.) MN frequencies ( per thousand ) in nasal cells were 3.50 (+/-1.80) among the dental technicians and 1.19 (+/-0.53) among the controls, which was also a statistically significant difference (P<0.005). There was a significant correlation between duration of exposure and MN frequencies in lymphocytes (r=0.642, P<0.01), but not in nasal cells of technicians. Our data reveal that in vivo exposure to chromium, nickel and cobalt metals is evident and that this occupational exposure may contribute to the observed genotoxic damage in two types of cells, e.g. lymphocytes and exfoliated nasal cells. However, it cannot be determined which compound(s) are responsible for the genotoxic damage observed in this study.

Adolescent↗
PubMed2006

[Occupational asthma caused by chromium and nickel].

We report the case of a 40-year-old woman who developed occupational asthma following exposure to chromium and nickel in the nickel-plating section of a metalworks company. Skin prick tests for specific antibodies proved positive for nickel chloride at a concentration of 1 mg/mL and negative for potassium dichromate. The specific bronchial provocation test confirmed the diagnosis of occupational asthma due to exposure to chromium and nickel. The patient presented a late positive reaction to nickel chloride (0.1 mg/mL) and an immediate positive reaction to a 10 mg/mL solution of potassium dichromate. These results indicate a dual response to nickel and chromium in this patient.

Adult↗