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PubMed2003

Variation of pH, conductivity and potential values in chromium (VI) removal by wool.

Variation of pH, conductivity and potential values in chromium (VI) removal by wool was investigated in this study. In addition to chromium (VI) concentrations, pH, conductivity and potential values were also traced during the experimental studies. After applying linear regression to experimental data, it was seen that there was a relationship between pH, conductivity, potential values and chromium (VI) concentrations in the aqueous solution after treatment with wool. This relationship was evaluated in the light of the analyses of the linear regression. Kinetic data and adsorption isotherms for chromium (VI) adsorption by wool were also determined.

Adsorption↗
PubMed2004

A study on the reduction of hexavalent chromium in aqueous solutions by vinasse.

Hexavalent chromium introduced to the water ecosystem is an important issue due to the toxic effect it poses. The first step of conventional treatment of wastewaters containing hexavalent chromium is its reduction to chromium (III) which is less toxic. The use of industrial waste material for the reduction of chromium (VI) may be a new cost-effective alternative. In this study, Cr(VI) reduction characteristics of vinasse which is a waste material of alcohol production from sugar beet molasses was investigated. The parameters of pH, temperature, concentrations of initial Cr(VI) and vinasse on the reduction of Cr(VI) were examined as a function of time by applying batch tests. Cr(VI) was almost completely reduced within about 270 min in the concentrations of Cr(VI) and vinasse of 80 mg l(-1) and 200 ml l(-1), respectively, at pH 3.0 and 25 degrees C. The results showed that reduction time can be shortened by increasing acidity and vinasse concentration or decreasing Cr(VI) initial concentration. Cr(VI) reduction process was found be obey first order kinetic model of homogenous phase reactions. The temperature was found to have a positive effect on the reduction process and the activation energy of process was calculated as 46.07 kJ mol(-1). Although the detoxification of wastewaters containing Cr(VI) via reducing it to Cr(III) by using vinasse seems to be cost-effective, the resulting effluent to be produced necessitates a further treatment to reduce organic pollution.

Carcinogens, Environmental↗
PubMed2006

Toxicity and carcinogenicity of chromium compounds in humans.

Chromium is a human carcinogen primarily by inhalation exposure in occupational settings. Although lung cancer has been established as a consequence of hexavalent chromium exposure in smokers and nonsmokers, some cancers of other tissues of the gastrointestinal and central nervous systems have also been noted. Except for a few reports from China, little is known about the health risks of environmental exposures to chromium. Likewise, there has been a lack of epidemiological studies of human exposure to hexavalent Cr by drinking water or ingestion, and it has been suggested that humans can perhaps tolerate hexavalent Cr at higher levels than the current drinking water standard of 50 ppb. This review highlights the most recent data on the induction of skin tumors in mice by chronic drinking-water exposure to hexavalent chromium in combination with solar ultraviolet light. This experimental system represents an important new animal model for chromate-induced cancers by ingestion of drinking water, and it suggests by extrapolation that chromate can likely be considered a human carcinogen by ingestion as well. The potential use of this animal model for future risk assessment is discussed.

Animals↗
PubMedDate not supplied

Cancer hazards caused by nickel and chromium exposure.

An increased risk of cancer associated with nickel refining and with chromate production has been known for some decades. The occupational exposure pattern of both nickel and chromium is very complex. Even though nickel carbonyl is an experimental carcinogen, there are no data supporting its carcinogenicity in humans. Nickel subsulfide may be the most potent carcinogen among the different nickel compounds. A correlation between lung cancer and exposure to chromates has been shown in several studies. As yet, there are no epidemiologic data indicating carcinogenicity of chromium(III) salts. Hexavalent chromium, however, has been suggested as the causative carcinogen among platers and ferrochromium workers. There is an urgent need for careful dose registration before a quantitative cancer risk analysis can be performed for the nickel and chromium industry.

Chromium↗
PubMed1984

Effect of chromium and manganese particles on the interferon system.

Mammalian (LLC-MK2) cell monolayers pretreated with either chromium or manganese particles depressed viral induction of IFN by approximately 50% but the presence of metal particles did not prevent exogenous IFN from conferring antiviral cellular resistance. Manganese particles were more detrimental to viral IFN induction than chromium particles in that almost tenfold less of the former achieved a comparable magnitude of IFN inhibition. Although rates of influenza virus multiplication in either chromium or manganese-treated and control cell cultures were similar, virus attained a level of growth almost twofold higher in metal-treated cells than in controls. This was related to suppression of viral IFN induction by metal particles. Neuraminidase treatment of cell surface salioglycoproteins or pretreatment of chromium or manganese particles with sialic acid abrogated the adverse activity of metal particles on viral IFN induction. These findings suggest that the receptivity and interaction of cell membrane-bound sialic acid residues with metal particles are involved in the altered cellular protective response described.

Animals↗
PubMed1978

The effect of glucose loading on urinary excretion of chromium in normal adults, in individuals from diabetic families and in diabetics.

This study was designed to investigate the effect of oral glucose tolerance tests (OGTT) on urinary chromium excretion in normal individuals, in individuals belonging to diabetic families, and in diabetics. The results can be summarized as: 1) eight of the 10 normal adults showed a significant increase both in terms of chromium per minute and chromium/creatinine (Cr/Cre) ratio after OGTT, and the difference between the mean values before and after OGTT was significant, 2) Of the 13 individuals from diabetic families, only five increased their chromium excretion and chromium/creatinine ratio after the glucose challenge (39%). However, the mean values for the group before and after OGTT remained statistically unchanged, 3) three of eight overt diabetic subjects (38%) showed moderate increase the chromium excretion and Cr/Cre ratio after OGTT, but the mean values were not effected. The creatinine values in urine remained constant before and after OGTT in all groups. These results suggest that a positive Cr/Cre response is more likely to occur in groups of normals than in groups of diabetics, and in individuals from diabetic families.

Adolescent↗
PubMed1980

Longitudinal study of chromium in human milk.

Using low temperature ashing and graphite furnace atomic absorption, the concentration of chromium in breast milk samples of 10 breast-feeding mothers was measured and the chromium intake of their totally breast-fed infants was evaluated. Ten samples were collected during 8 to 18 days and five samples during 47 to 54 days and 128 to 159 days of lactation. The milk samples represented every feed during a period of 24 hr and contained foremilk and hindmilk in equal proportions. The mean chromium concentration in the breast milk was 0.39 (SD 0.15) ng/ml and the intake 0.27 (SD 0.11) microgram/day. The mean chromium concentration, or intake in the breast milk did not significantly change with advancing stages of lactation.

Breast Feeding↗
PubMed1981

Urinary chromium excretion during pregnancy and its relationship with intravenous glucose loading.

This study was conducted to investigate the changes in urinary chromium excretion in the different stages of pregnancy and the effect of intravenous glucose tolerance test on urinary excretion of chromium in late pregnancy. Urine samples were collected from pregnant women cross-sectionally and longitudinally in different stages of pregnancy. Urinary chromium excretion before and after intravenous glucose tolerance test was also determined in nine women in their 3rd trimester of pregnancy. The results can be summarized as: 1) mean chromium/creatinine ratio in urine increased significantly with advancing pregnancy, 2) in late pregnancy, with the exception of one subject, urinary chromium/creatinine ratio showed a decrease after intravenous glucose tolerance test. The results obtained in this study have led us to conclude that the habitual dietary intake does not meet the increased chromium requirement and that prophylaxis may be of benefit and appears to be advisable in pregnancy.

Adolescent↗
PubMed1982

Chromium and insulin in young subjects with normal glucose tolerance.

In a group of 20 college subjects, the fasting serum chromium level was found to correlate with the fasting serum insulin level (r = 0.512, p less than 0.05), with the percentage of ideal body weight (r = 0.637, p less than 0.01), and with the triceps skinfold thickness (r = 0.525, p less than 0.02). The relative chromium response at insulin peak was inversely correlated with the total insulin (r = -0.451, p less than 0.05) as well as with the ratio of the total insulin to the total glucose (r = -0.554, p less than 0.02). In order to examine the close relationship between chromium and insulin, the 20 subjects were divided into age- and sex-matched lower insulin secretors and higher insulin secretors based on individuals' total insulin levels calculated as the sum of six measurements in microunits/ml during a 3-h oral glucose tolerance test. The 10 subjects in LI had total insulin levels less than 500, and the 10 subjects in HI had total insulin levels equal to or greater than 500. The means (+/- SEM) of total insulin for LI and HI were 354 +/- 39 and 740 +/- 46, respectively (p less than 0.001). The relative chromium response was significantly higher in LI than that in HI (198.0 +/- 31.0% and 76.2 +/- 18.0%, respectively; p less than 0.005); and the ratio of the total insulin to the total glucose was significantly lower in LI than that in HI (0.585 +/- 0.067 and 1.286 +/- 0.094, respectively; p less than 0.001).

Adolescent↗
PubMed1984

The uptake and excretion of chromium by the elderly.

Metabolic balance studies for chromium have been carried out on 22 apparently healthy elderly people and one subject with impaired glucose tolerance. All subjects were aged between 69.7 and 85.5 yr, ate self-chosen diets, and lived in their own homes during the study. The mean daily intake of chromium for the healthy subjects was 471 nmol (24.5 micrograms) with a mean retention of 3 nmol (0.2 microgram). The subject with a raised plasma glucose was in positive balance for chromium. Although the daily chromium intake was below the lower limit of the estimated safe and adequate daily dietary intake proposed by the American Food and Nutrition Board it appeared to be adequate for these subjects.

Aged↗
PubMed1990

Urinary chromium excretion and insulinogenic properties of carbohydrates.

Eleven male and nine female adult subjects were given one of the following five carbohydrate-drink combinations (per kg body wt) on five mornings separated by greater than or equal to 2 wk: 1) 1.0 g glucose, 2) 0.9 g uncooked cornstarch, 3) 1.0 g glucose followed 20 min later by 1.75 g fructose, 4) 0.9 g uncooked cornstarch followed 20 min later by 1.75 g fructose, and 5) water followed 20 min later by 1.75 g fructose. Glucose plus fructose was the most insulinogenic followed by glucose alone, starch plus fructose, starch alone, and water plus fructose. The urinary losses of chromium followed a similar pattern. Subjects with the highest concentrations of circulating insulin displayed decreased ability to mobilize chromium on the basis of urinary chromium excretion. Therefore, urinary chromium losses are related to the insulinogenic properties of carbohydrates.

Adult↗
PubMed1992

Occupational exposure to chromium, copper and arsenic during work with impregnated wood in joinery shops.

CCA-impregnated timber contains copper, chromium and arsenic (CCA), and occupational exposure to wood dust as well as the CCA compounds may occur in work with such timber. Dust from commercially available impregnated wood has been found to contain hexavalent chromium, which is regarded as a carcinogen. Apart from determinations of the total amounts of the CCA compounds, specific determination of hexavalent chromium is therefore essential. Selective methods have been applied for control of the work environment in six joinery shops. The mean exposure to wood dust was found to be below 1 mg m-3. The mean airborne concentration of arsenic around various types of joinery machines was in the range from 0.54 to 3.1 micrograms m-3. No hexavalent chromium was detected in any samples and no increased concentrations of arsenic were found in urine from the workers. The presence of arsenic in the work-room air must be considered for appropriate assessment of the occupational environment in joinery shops.

Air Pollutants, Occupational↗
PubMed1989

Molecular interaction of different chromium species with nucleotides and nucleic acids.

The interaction of chromium(III) and chromium(VI) with the phosphate groups of di- and triphosphate nucleotides were examined by 31P-NMR spectroscopy. Chemical shifts of the phosphate groups, indicating the formation of Cr-nucleotide complexes, could only be detected with Cr(III). When Cr(III) was generated from Cr(VI) by reduction with an excess of glutathione, nearly the same chemical shifts could be observed. This indicates that glutathione is not capable of trapping Cr(VI) by reduction with subsequent formation of stable Cr-GSH complexes, thus preventing the binding of chromium to important target molecules as DNA or nucleotides. Using radioactively-labelled chromium no 51Cr(VI) bound to any nucleic acid, whereas 51Cr(III) bound in increasing order to poly(A).poly(U), calf thymus DNA and poly(G).poly(C). Furthermore, the melting temperature of nucleic acids increased in the same order only in the presence of Cr(III). Possible genotoxic consequences in vivo of the presented data in vitro concerning the binding of Cr(III) to sensitive molecular targets are discussed in detail.

Chromium↗
PubMed1991

Complexing of actin and other nuclear proteins to DNA by cis-diamminedichloroplatinum(II) and chromium compounds.

Actin was found to be the major protein crosslinked to the DNA of intact Chinese hamster ovary cells that were treated with either potassium chromate (hexavalent) or cis-diamminedichloroplatinum(II) (cis-platinum). This protein was identified as actin by its mol. wt (45 kd), its isoelectric point (pI = 5.4), positive reactivity with an actin antibody, and by protease mapping. Additionally, a purified actin standard migrated to the same location in a two-dimensional gel system as p45. Actin comprised approximately 20% of the protein component in chromate-induced DNA-protein crosslinks. In addition, to actin, several other major proteins (e.g. 53 kd, pI = 5.2, 50 kd, pI = 9) were crosslinked to DNA following exposure to cis-platinum or chromate. These proteins were abundant in the nuclear matrix fraction. Hexavalent chromate is the toxicologically active form because it is readily taken up into cells by an anion transport system. In contrast, trivalent chromium is considerably less toxic because it cannot enter the cell; however, most of the hexavalent form is eventually reduced to the trivalent form inside the cell. Previous studies have suggested that the trivalent form of chromium participates in complexing DNA with proteins. DNA-protein crosslinks were formed in isolated nuclei or in mixtures of purified DNA and protein incubated with trivalent chromium. However, the formation of these complexes required at least 16 h of incubation to exchange the parent compound ligands. Hexavalent chromate did not form these complexes in vitro under similar conditions. Incubation of trivalent chromium with purified actin and DNA resulted in DNA-actin crosslinks as detected by an electrophoretic mobility different from that of either free actin or DNA when the complex was transferred from a gel to nitrocellulose and stained for protein. These studies describe a new technique for detecting DNA-protein complexes and demonstrate that actin-DNA structures in intact cells create sites that selectively react with metal DNA-protein crosslinking agents.

Actins↗
PubMed1991

The reduction of chromate is a prerequisite of chromium binding to cell nuclei.

Isolated calf thymus nuclei bound a chromium(III) glutathione complex in a time-dependent manner. In contrast chromium(VI) (sodium chromate) did not bind. However, when chromate was incubated with the nuclei in the presence of glutathione, chromium adducts were detected. These observations indicate that the reduction of chromate, by a reducing agent such as glutathione, is a prerequisite for the generation of bonds between the metal and constituents of the cell nuclei in vitro. Chromium adducts with nuclei are probably one cause of DNA lesions and mutations.

Animals↗
PubMed1994

The genotoxic carcinogen chromium(VI) alters the metal-inducible expression but not the basal expression of the metallothionein gene in vivo.

The ability of the carcinogen chromium(VI) to affect the basal and zinc-inducible expression of liver metallothionein was examined in 14- and 18-day chicken embryos in vivo. Metallothionein expression varied with the stage of embryo development, with basal steady-state mRNA levels being approximately three times lower in livers of 18-day versus 14-day chicken embryos. Chromium(VI) treatment had no effect on the basal steady-state levels of metallothionein mRNA and protein in either 14- or 18-day chicken embryo liver. Treatment of 14-day embryos with zinc(II) resulted in a 3- to 5-fold increase in steady-state levels of metallothionein mRNA in liver. Pre-treatment of 14-day embryos with chromium(VI) inhibited the zinc(II)-induced increase in steady-state levels of metallothionein mRNA and protein in liver by 30-50%. In contrast, chromium(VI) and/or zinc(II) treatments had no effect on steady-state levels of beta-actin mRNA.

Animals↗
PubMed1982

Cytotoxic, mutagenic and clastogenic effects of industrial chromium compounds.

Ten Cr(III) compounds, used in the leather tanning industry, and a Cr(III) compound, containing chromite and used as a pigment, were tested for cytotoxicity (inhibition of growth and survival of cultured hamster cells), mutagenicity (point mutations in S. typhimurium) and clastogenic activity (chromosomal aberrations and sister chromatid exchanges in hamster cells). Reference Cr compounds were potassium dichromate as Cr(VI), and chromium chloride and two different preparations of chromium nitrate as Cr(III). A contamination with Cr(VI) was detected in some of the Cr(III) tannins, chromite and one chromium nitrate. Cr(III) compounds were cytotoxic at concentrations of Cr(III) 100-500 times higher than Cr(VI), but contaminated Cr(III) compounds showed a significant cytotoxicity. Reference Cr(VI) but not Cr(III) was mutagenic: of the contaminated compounds only chromite and chromium nitrate, which contained higher levels of Cr(VI), were found to be mutagenic. The frequency of sister chromatid exchanges was significantly increased only by Cr(VI) and the more contaminated Cr(III) compounds. However, an increase of chromosomal aberrations was produced also by reference Cr(III) salts and the weakly contaminated industrial Cr(III) compounds. These results confirm the view that the active mutagenic agent in intact cell systems is Cr(VI), but indicate that industrial Cr(III) compounds cannot be considered genetically inert, as they can be contaminated by Cr(VI) and induce chromosomal aberrations.

Animals↗
PubMed1984

Chromium deficiency and cardiovascular risk.

Recent measurements have demonstrated that plasma chromium levels in patients with coronary artery disease are very much lower than in normal subjects. A review of the literature concerning the physiological functions of chromium (or GTF) shows it to be implicated in most of the known factors of cardiovascular risk, via its effect on insulin levels and activities. Chromium deficiency leads to impaired lipid and glucide metabolism and results in high circulating insulin levels, the probable consequences of which suggest that chromium deficiency may be a primary risk factor in cardiovascular disease.

Amino Acids↗