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PubMed2006

Oral chromium(VI) does not affect the frequency of micronuclei in hematopoietic cells of adult mice and of transplacentally exposed fetuses.

Chromium(VI) compounds are genotoxic in a variety of cellular systems. Their potential carcinogenicity is affected by toxicokinetic patterns restricting bioavailability to certain targets, and by metabolic pathways affecting interaction of chromate-derived reactive species with DNA. Epidemiological data indicate that chromium(VI) can be carcinogenic to the human respiratory tract following inhalation at doses that are only achieved in certain occupational settings. However, concern has been raised that adverse effects may also result from oral intake. In order to further explore this issue, we performed studies in BDF1 and Swiss mice of both genders and various age. Sodium dichromate dihydrate and potassium dichromate were administered either with the drinking water, up to a concentration of 500 mg chromium(VI)/l for up to 210 consecutive days, or in a single intragastric dose of 17.7 mg/kg body weight. Under these conditions, no increase of the micronucleus frequency was observed in either bone marrow or peripheral blood erythrocytes. Conversely, the same compounds induced a clastogenic damage following intraperitoneal injection, which by-passes detoxification mechanisms. In addition, due to the hypothesis that susceptibility may be increased during the period of embryogenesis, we treated pregnant mice, up to a concentration of 10mg chromium(VI)/l drinking water. There was no effect on the numbers of fetuses/dam and on body weight of fetuses. Again, no toxic or genotoxic effect was observed either in bone marrow of pregnant mice or in liver and peripheral blood of their fetuses. Thus, even at doses that largely exceed drinking water standards (up to 10,000 times) or by massive intragastric administration, chromium(VI) is not genotoxic to hematopoietic cells of either adult mice or transplacentally exposed fetuses. These conclusions are consistent with the poor toxicity and lack of carcinogenicity of oral chromium(VI), and are mechanistically explained by the high efficiency of chromium(VI) detoxification processes in the gastrointestinal tract.

Administration, Oral↗
PubMed2006

Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its ion-association complex with cetyltrimethylammoniumbromide on an alumina column.

A simple approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its ion-association complex with cetyltrimethylammoniumbromide (CTABr) on an alumina column. The effect of various parameters such as acidity, stability of the column, sample volume, effect of diverse ions, etc. have been studied in detail. The adsorbed complex could be eluted using sodium hydroxide and the concentration of chromium has been established using visible spectrophotometry after complexation with diphenyl carbazide. The calibration graph was linear in the range 0-0.5 microg mL(-1) chromium(VI) with a detection limit of 5 microg L(-1). A highest preconcentration factor of 25 could be obtained for 250 mL sample volume. The data from the column studies were also studied using the Thomas model of adsorption. The experimental results obtained were correlated with the proposed model of adsorption. The Thomas rate constant k was found to be 0.0025 L/min mg and the maximum adsorption capacity q(o) was found to be 0.36 mgCr/g alumina at an initial chromium(VI) concentration of 1 mg L(-1). The validity of the method has been checked by applying it to study the recovery of chromium in spiked water samples and electroplating wastewater.

Adsorption↗
PubMed1989

Mutagenicity and disposition of chromium.

Hexavalent chromium was administered to rats at doses of 20-240 mumol kg-1 for several periods of time, from 2 to 14 days. Lung, liver and blood contained the highest amounts of chromium, as detected by atomic absorption or by ICP, 24 h after cessation of treatment. A maximum of 40% of the dose was recoverable in organs along with feces and urine at this same time period, and chromium in soil (5.6% Cr) was absorbed better than equimolar amounts of the hexavalent chromates of calcium or sodium. The contaminated chromium-containing soil was found to have 30-35% of the chromium in the hexavalent state. The mutagenicity of chromium as tested in the bacterial strain of Salmonella typhimurium (strain TA 104) was decreased when tested without metabolic activation with the addition of leachate (of inexact analysis) from a waste site. When studied by alkaline elution, chromium (5-20 microM) caused single strand breaks as well as DNA-protein crosslinks in A549 lung cells, while with L1210 mouse leukemia cells, only DNA-protein crosslinks were found. Chromium(III) compounds caused no damage to DNA.

Animals↗
PubMed2006

Biochemical study on the protective role of folic acid in rabbits treated with chromium (VI).

Deleterious effects of chromium (VI) compounds are diversified affecting almost all the organ systems in a wide variety of animals. Therefore, the present study was carried out to determine the effectiveness of folic acid (FA) in alleviating the toxicity of chromium (VI) on certain biochemical parameters, lipid peroxidation, and enzyme activities of male New Zealand white rabbits. Six rabbits per group were assigned to one of four treatment groups: 0 mg FA and 0 mg Cr(VI)/kg BW (control); 8.3 microg FA/kg BW; 5 mg Cr(VI)/kg BW; 5 mg Cr(VI) plus 8.3 microg FA/kg BW, respectively. Rabbits were orally administered their respective doses every day for 10 weeks. Results obtained showed that Cr(VI) significantly (P < 0.05) increased the levels of free radicals and the activity of glutathione S-transferase (GST), and decreased the content of sulfhydryl groups (SH groups) in liver, testes, brain, kidney, and lung. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AlP), acid phosphatase (AcP), and lactate dehydrogenase (LDH) were significantly decreased in liver and testes due to Cr(VI) administration. Also, AlP and AcP activities were significantly decreased in kidney and lung. The activity of acetylcholinesterase (AChE) was significantly decreased in brain and plasma. Contrariwise, the activities of AST and ALT were significantly increased in plasma, while AlP and AcP decreased. Chromium (VI) treatment caused a significant decrease in plasma total protein (TP) and globulin, and increased total lipids (TL), cholesterol, glucose, urea, creatinine, and bilirubin concentrations. Folic acid alone significantly decreased the levels of free radicals in liver, brain, and kidney, and increased the content of SH-group. The activities of AST, ALT, and LDH in liver; AST, ALT, AlP, AcP, and LDH in testes; AcP in kidney; AlP and AcP in lung, and LDH in brain were significantly increased. Plasma TP and albumin were increased, while urea and creatinine were decreased. The presence of FA with Cr(VI) restored the changes in enzyme activities and biochemical parameters. In conclusion, folic acid could be effective in the protection of chromium-induced toxicity.

Administration, Oral↗
PubMed2005

Semen quality of industrial workers occupationally exposed to chromium.

A total of sixty-one subjects occupationally exposed to chromium in an industry which manufactures chromium sulphate and fifteen control subjects from a nearby industry which does not manufacture any chromium related compounds were studied. The history of each subject was recorded on pre-designed form through interview and a routine medical examination was carried out. Blood samples (5-6 ml) were collected for the estimation of chromium and semen samples were collected for semen analysis and the determination of copper and zinc levels in the seminal plasma. Clinical examination revealed nasal perforation in 10 subjects (out of 61) in the exposed group as compared to none in the control group. A significantly higher level of chromium was observed in the blood of the exposed workers as compared to the control. The concentration of zinc in seminal plasma was lower while the level of copper was higher in the exposed group as compared to the control. However, these changes were not statistically significant. Statistically significant higher numbers of morphologically abnormal sperms were noticed in the exposed group with respect to the control. Further analysis of the data indicated that about 53% of the exposed subjects showed less than 30% normal forms as compared to 10% in control subjects. However, no significant alterations in semen volume, liquefaction time, mean pH value, sperm viability, concentration or motility, were noticed between chromium exposed and unexposed workers. The data also indicates that exposure to chromium has some effect on human sperm as a significant positive correlation (r=0.301) was observed between percentages of abnormal sperm morphology and blood chromium levels (p=0.016) after pooling all the data of the control and exposure groups.

Adult↗
PubMed2006

An unusual local reaction after microsclerotherapy with chromated glycerin.

A case of papular itching lesions after microsclerotherapy with chromated glycerin (CG) at a 72% concentration for telangiectases of the thighs is reported. Patch-test results were strongly positive for nickel sulfate (+++/+++) and thimerosal (++/++) whereas results were negative for the sclerosing agent CG 72% and glycerol (control). Intradermal injection of CG 72% in the thigh and intravascular injection of CG 72% into telangiectases of the knee produced erythematous papular itching lesions in about 5 to 6 hours. As a negative control, glycerol and sodium chloride 0.9% injected intradermically on the thigh did not cause any reaction. CG can elicit allergic reactions in patients who are sensitive to chromium and can cause new sensitizations to chromium. In our case, no positivity to potassium dichromate was observed.

Alum Compounds↗
PubMedDate not supplied

Light-catalyzed chromium(VI) reduction by organic compounds and soil minerals.

Detoxification of Cr(VI) through reduction has been considered an effective method for reclaiming Cr-contaminated soil, sediment, and waste water. Organic matter is widely distributed in soil and aquatic systems; however, low Cr(VI) reduction rates inhibit the adoption of Cr reduction technologies by industry. Scientists have been aware of Cr(VI) reduction catalyzed by soil minerals; however, most of the studies focused on using semiconductors as catalysts with UV irradiation to accelerate the redox reactions. The objective of this study was to evaluate the rates of Cr(VI) reduction by fluorescence light in the presence of organic materials with or without specific soil minerals. Experimental results showed that dissolved organic compounds reduced Cr(VI) slowly under laboratory light; however, Cr(VI) reduction was greatly enhanced when growth chamber light was applied. Low photon flux (i.e., laboratory light) only enhanced Cr(VI) reduction by organics when Fe(III) was also present, because the Fe(II)-Fe(III) redox couple accelerated electron transfer and decreased electrostatic repulsion between reactants. Laboratory light was required to initiate Cr(VI) reduction catalyzed by TiO2; nonetheless, light-catalyzed Cr(VI) reduction by smectite and ferrihydrite could occur only when greater light energy was provided with a growth chamber light. Our results suggest a potential pathway for Cr(VI) reduction using naturally occurring organic compounds and colloids in acidic water systems or in surface soils when light is available.

Catalysis↗
PubMed2003

Sialoglycoprotein and carbohydrate complexes in chromium toxicity.

Chromium(VI) compounds are amongst the most widely encountered industrial carcinogens and are of increasing concern with respect to environmental exposure. Sialoglycoproteins and carbohydrates play a crucial role in stabilizing oxoCr(V) intermediates, which are produced by extracellular and intracellular reduction of chromium(VI). Recent research has addressed the molecular characterization of oxoCr(V)-sialoglycoprotein and -carbohydrate complexes and the roles that these species may play in Cr(VI) metabolism and carcinogenesis. Particular highlights include the role of oxoCr(V) complexes of extracellular sialoglycoproteins, intracellular D-glucose, and related species and their potential roles in Cr(VI)-induced genotoxicity.

Animals↗
PubMed2002

The dermal toxicity of cement.

Cement and concrete are products used widely in the construction sector, with a traditional perception that any hazards that they have are limited to dermatitis in a small number of workers. In some cases, employers and builders do not think that concrete is a chemical. However, contact dermatitis is one of the most frequently reported health problems among construction workers. A review of the available literature suggests that cement has constituents that produce both irritant contact dermatitis and corrosive effects (from alkaline ingredients such as lime) and sensitization, leading to allergic contact dermatitis (from ingredients such as chromium). These findings indicate that cement and concrete should be treated as hazardous materials, and that workers handling such products should reduce exposure wherever possible. Initiatives to reduce the chromium content of cement have been shown to be successful in reducing the incidence of allergic dermatitis, although the irritant form remains.

Calcium Compounds↗
PubMed2004

Electron transfer reaction of oxo(salen)chromium(V) ion with anilines.

The kinetics of oxidation of 16 meta-, ortho-, and para-substituted anilines with nine oxo(salen)chromium(V) ions have been studied by spectrophotometric, ESIMS, and EPR techniques. During the course of the reaction, two new peaks with lambda(max) at 470 and 730 nm appear in the absorption spectrum, and these peaks are due to the formation of emeraldine forms of oligomers of aniline supported by the ESIMS peaks with m/z values 274 and 365 (for the trimer and tetramer of aniline). The rate of the reaction is highly sensitive to the change of substituents in the aryl moiety of aniline and in the salen ligand of chromium(V) complexes. Application of the Hammett equation to analyze kinetic data yields a rho value of -3.8 for the substituent variation in aniline and +2.2 for the substituent variation in the salen ligand of the metal complex. On the basis of the spectral, kinetic, and product analysis studies, a mechanism involving an electron transfer from the nitrogen of aniline to the metal complex in the rate controlling step has been proposed. The Marcus equation has been successfully applied to this system, and the calculated values are compliant with the measured values.

Acrylonitrile↗
PubMed1994

Bond strength of adhesive resin to three nickel-chromium alloys with varying chromium content.

This in vitro study evaluated the influence of chromium content on bond strength and durability between nickel-chromium alloys and an adhesive resin that contained 4-methacryloxyethyl trimellitate anhydride. Three nickel-chromium alloys with different chromium content, as well as pure chromium and pure nickel metals, were bonded and tested for shear strength. After repeated thermocycling, shear bond strength decrease was lower in alloys containing high chromium content. Pure chromium metal demonstrated a 15.2% decrease, whereas pure nickel metal demonstrated the greatest (53.7%) decrease. The results suggest that nickel-chromium alloys with higher chromium content are desirable for 4-methacryloxy-ethyl trimellitate anhydride resin-bonded restorations.

Acrylic Resins↗
PubMed2005

Cellular chromium enhances activation of insulin receptor kinase.

Chromium has been recognized for decades as a nutritional factor that improves glucose tolerance by enhancing in vivo insulin action, but the molecular mechanism is unknown. Here we report pretreatment of CHO-IR cells with chromium enhances tyrosine phosphorylation of the insulin receptor. Different chromium(III) compounds were effective at enhancing insulin receptor phosphorylation in intact cells, but did not directly activate recombinant insulin receptor kinase. The level of insulin receptor phosphorylation in cells can be increased by inhibition of the opposing protein tyrosine phosphatase (PTP1B), a target for drug development. However, chromium did not inhibit recombinant human PTP1B using either p-nitrophenyl phosphate or the tyrosine-phosphorylated insulin receptor as the substrate. Chromium also did not alter reversible redox regulation of PTP1B. Purified plasma membranes exhibited insulin-dependent kinase activity in assays using substrate peptides mimicking sites of Tyr phosphorylation in the endogenous substrate IRS-1. Plasma membranes prepared from chromium-treated cells had higher specific activity of insulin-dependent kinase relative to controls. We conclude that cellular chromium potentiates insulin signaling by increasing insulin receptor kinase activity, separate from inhibition of PTPase. Our results suggest that nutritional and pharmacological therapies may complement one another to combat insulin resistance, a hallmark of type 2 diabetes.

Amino Acid Sequence↗
PubMed2000

Increased levels of oxidatively damaged DNA induced by chromium(III) and H2O2: protection by melatonin and related molecules.

Chromium (Cr) compounds are known occupational and environmental carcinogens. This trace element is found in the workplace primarily in the valence forms Cr(III) and Cr(VI). Cr(III), which was thought originally to be relatively nontoxic, was recently found to be more reactive toward purified DNA than was chromium(VI). Herein, we examined the ability of Cr(III) to induce oxidative DNA damage by measuring the formation of 8-hydroxydeoxyguanosine (8-OH-dG) in purified calf thymus DNA incubated with CrCl3 plus H2O2. In this system we observed that the Cr(III)-induced formation of 8-OH-dG in isolated DNA was both dose- and time-dependent. When melatonin and related molecules, including 6-methoxy-1,2,3,4-tetrahydro-beta-carboline (pinoline), N-acetylserotonin, 6-hydroxymelatonin and indole-3-propionic acid, were co-incubated with CrCl3 plus H2O2, the accumulations of 8-OH-dG in DNA samples were markedly inhibited in a concentration-dependent manner. The concentrations of each indole required to reduce DNA damage by 50%, i.e. the IC50 values, were 0.48, 0.51, 0.88, 1.00 and 3.08 microM for pinoline, melatonin, N-acetylserotonin, 6-hydroxymelatonin and indole-3-propionic acid, respectively. These results suggest that one of the mechanisms by which Cr(III) may induce cancer is via Fenton-type reactions which generate the hydroxyl radical (*OH). The findings also indicate that the protective effects of melatonin and related molecules against Cr(III)-induced carcinogenesis relate to their direct *OH scavenging ability which thereby reduces the formation of the damaged DNA product, 8-OH-dG.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1989

[Skin diseases and sensitization to metals in construction workers engaged in the production of pre-cast cellular concrete slabs].

The study involved 461 building workers exposed to ashes, cement and ash-cement mixtures in direct production and at auxiliary posts (fitters, welders, mechanics, electricians etc.). In addition, all those workers were exposed to lubricants ans machine oils, as well as anti-adhesive oils used to lubricate moulds. All the subjects underwent patch tests. Dermatitis was found in 18.9%, whereas oil acne in 7.4% of subjects, 23.0% exhibited chromium allergy, 15.2% - cobalt allergy and 5.0% - nickel allergy. Two workers were ++hypersensitive to zinc. No differences were found in the rates of dermatitis, oil acne and metal allergy between production workers and auxiliary ones. Airborne dust concentrations at those workplaces were similar. Cement and ashes contained compounds of chromium, cobalt and nickel.

Adult↗
PubMed2000

Risk of lung cancer in workers producing stainless steel and metallic alloys.

OBJECTIVES: The mortality of workers involved in the production of stainless and alloyed steel from 1968 to 1992 was studied, in order to investigate the risk of lung cancer due to exposure to metals, i.e. iron oxides, chromium and/or nickel compounds. METHODS: The study design was a historical cohort mortality study and a nested case-control study concerning lung cancer. Standardized mortality ratios (SMRs) were computed using regional mortality rates as an external reference for comparing observed and expected numbers of deaths, adjusting for age, sex and calendar time. Conditional logistic regression was used to estimate odds ratios (ORs). Occupational exposure was assessed through the complete job histories of cases and controls and a specific job-exposure matrix. RESULTS: The cohort comprised 4,288 male and 609 female workers. The observed overall mortality was significantly lower than expected [649 deaths; SMR = 0.91; 95% confidence interval (CI) 0.84-0.98]. No significant SMR was observed for mortality from lung cancer (54 deaths; SMR = 1.19; CI 0.88-1.55). The case-control study was based on 54 cases and 162 individually matched controls. Smoking habits were available for 71%. No lung cancer excess was observed for exposure to (1) metals and/or their compounds, i.e. iron (OR = 0.94, CI 0.48-1.86), chromium and/or nickel (OR = 1.18, CI 0.62-2.25), and cobalt (OR =0.64, CI 0.33-1.25), (2) acid mists (OR = 0.43, CI 0.17-1.10), and (3) asbestos (OR = 1.00, CI 0.54-1.86). With respect to exposure to polycyclic aromatic hydrocarbons (PAHs) and silica, which are often found together in workplaces, (1) high and statistically significant lung cancer excesses were observed, the ORs being 1.95 (CI 1.03-3.72) and 2.47 (CI 1.28-4.77) respectively, (2) quantitative exposure parameters revealed upward trends reaching statistical significance (P < 0.05), and (3) adjustments for tobacco consumption did not reveal any confounding factors from smoking. CONCLUSION: This study failed to detect any relationship between lung cancer and exposure to iron, chromium, nickel and/or their compounds. High and statistically significant relative risks, along with increasing trends, were observed for simultaneous exposure to PAHs and silica.

Aged↗
PubMed1993

The potential for bonding titanium restorations.

PURPOSE: The use of titanium for implants has shown the biological acceptance of the metal. Recently, methods of using titanium for restorations, crowns, and bridges have been introduced using both cast and spark erosion systems for fabrication. A potential also exists for using titanium for bonded (Maryland) bridges. MATERIALS AND METHODS: In this study, the potential for bonding titanium was investigated by cementing with various adhesives: (A) metal to metal, (B) metal to enamel, and (C) comparing with a known procedure of bonding nickel-chromium. Truncated cones of pure titanium were fabricated with a 5-mm circular face for bonding to a larger titanium disc embedded in a plastic ring. A special jig was used to pull the bonded cone from the disc on an Instron tensile testing machine (Instron Corporation, Canton, MA). The resin-metal adhesives used were: (1) Infinity, (2) Metabond, (3) All-Bond 2, and (4) Panavia. These were compared with (5) nickel-chromium cones sandblasted and bonded to nickel-chromium with Panavia. Titanium cones were also bonded to human enamel with (6) Panavia and (7) Metabond. The 10 samples in each group were subjected to tensile force, and point of fracture was recorded. The data were subjected to an analysis of variance with a Scheffe F test at the 95% level of significance. RESULTS: The results of tensile forces in MPa were (1) Infinity, 28.1 +/- 3.6; (2) Metabond, 28.1 +/- 1; (3) All-Bond 2, 49.5 +/- 4.3; (4) Panavia, 57.9 +/- 3.1; (5) Panavia to nickel-chromium, 42.9 +/- 6.6; (6) Panavia to enamel, 18.5 +/- 4.7; and (7) Metabond to enamel, 19.3 +/- 3.5. Titanium was most effectively bonded with All-Bond 2 and Panavia, with Panavia samples significantly better than Panavia to nickel-chromium samples. CONCLUSIONS: It was concluded that titanium bonded restorations with certain adhesive cements were a definite possibility.

Analysis of Variance↗