Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CHROMIUM”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,261 records · Page 70Linked to original sources
PubMed2000

In vitro and in vivo corrosion evaluation of nickel-chromium- and copper-aluminum-based alloys.

STATEMENT OF PROBLEM: The low resistance to corrosion is the major problem related to the use of copper-aluminum alloys. PURPOSE: This in vitro and in vivo study evaluated the corrosion of 2 copper-aluminum alloys (Cu-Al and Cu-Al-Zn) compared with a nickel-chromium alloy. MATERIAL AND METHODS: For the in vitro test, specimens were immersed in the following 3 corrosion solutions: artificial saliva, 0.9% sodium chloride, and 1.0% sodium sulfide. For the in vivo test, specimens were embedded in complete dentures, so that one surface was left exposed. The 3 testing sites were (1) close to the oral mucosa (partial self-cleaning site), (2) surface exposed to the oral cavity (self-cleaning site), and (3) specimen bottom surface exposed to the saliva by means of a tunnel-shaped perforation (non-self-cleaning site). RESULTS: Almost no corrosion occurred with the nickel-chromium alloy, for either the in vitro or in vivo test. On the other hand, the 2 copper-aluminum-based alloys exhibited high corrosion in the sulfide solution. These same alloys also underwent high corrosion in non-self-cleaning sites for the in vivo test, although minimal attack was observed in self-cleaning sites. CONCLUSION: The nickel-chromium alloy presented high resistance to corrosion. Both copper-aluminum alloys showed considerable corrosion in the sulfide solution and clinically in the non-self-cleaning site. However, in self-cleaning sites these 2 alloys did not show substantial corrosion.

Aluminum↗
PubMed2003

Bioremediation of chromium by the yeast Pichia guilliermondii: toxicity and accumulation of Cr (III) and Cr (VI) and the influence of riboflavin on Cr tolerance.

A comparative study has been made on the sensitivity of the yeast Pichia guilliermondii to Cr (III) and Cr (VI) as well as on the Cr uptake potential at growth-inhibitory concentrations of chromium. The strains used in the study were either isolated from natural sources or obtained from a laboratory strain collection. The results show that most of the natural strains were more tolerant to chromium and were able to grow in the presence of 5 mM Cr (III) or 0.5 mM Cr (VI), that is at concentrations which substantially inhibited the growth of laboratory strains. The cellular Cr content after treatment was similar for both strain types and ranged from 1.2-4.0 mg/g d.w. and 0.4-0.9 mg/g d.w., for Cr (III) and Cr (VI) forms, respectively, however, in one case of a natural strain it reached the value of 10 mg Cr (III)/g dry mass. Natural-source strains were grouped into four groups based on the yeasts' differential response to Cr (III) and Cr (VI). Hexavalent Cr-resistant mutants of a P. giuilliermondii laboratory strain, which revealed markedly changed capabilities of chromium accumulation, were obtained by means of UV-induced mutagenesis. Cr (VI) treatment triggered oversynthesis of riboflavin and the addition of exogenous riboflavin increased P. guilliermondii resistance to both Cr (III) and Cr (VI). Electrophoretic protein profiles revealed the induction and/or suppression of several proteins in response to toxic Cr (VI) levels.

Adaptation, Physiological↗
PubMedDate not supplied

Reduced IL-6 levels among individuals in Hudson County, New Jersey, an area contaminated with chromium.

Hudson County, New Jersey, was a major center for the processing of chromium ore. After processing, some of the ore residue that contained low concentrations of chromium became distributed in population centers throughout the county. There now exists concern in the county about possible health effects from chromium exposure. Our previous research suggested that immune-function assays would make useful biomarkers for chromate exposure in humans. Blood samples were drawn from 46 individuals who lived and/or worked in Hudson County and from 47 controls. Only one of the immune-associated assays performed on these samples showed any statistically significant differences between the Hudson County and control groups. The mean level of IL-6 produced by pokeweed mitogen-stimulated mononuclear cells isolated from the Hudson County group was 64% of the control value--a highly significant decrease (p<.001). There was also a significant correlation between the proliferative responses of the mononuclear cells to pokeweed mitogen and the levels of IL-6 produced by these cells. No differences were detected in the IL-6 responses that resulted from age, gender, or smoking status. The reliability of the IL-6 assay was found to be 90%. To our knowledge, there have been no reports, until now, that describe reduced production of any cytokine in individuals who are exposed to chromate.

Cell Division↗
PubMed2001

Effect of chromium supplementation and exercise on body composition, resting metabolic rate and selected biochemical parameters in moderately obese women following an exercise program.

OBJECTIVE: To investigate the effect of chromium picolinate (CP) supplementation on body composition, resting metabolic rate (RMR), selected biochemical parameters and iron and zinc status in moderately obese women participating in a 12-week exercise program. METHODS: Forty-four women, 27 to 51 years of age, were randomly assigned to two groups based on their body mass index. Subjects received either 400 microg/day of chromium as a CP supplement or a placebo in double-blind fashion and participated in a supervised weight-training and walking program two days per week for 12 weeks. Body composition and RMR were measured at baseline, 6 and 12 weeks. Selected biochemical parameters and iron and zinc status were measured at baseline and 12 weeks. RESULTS: Body composition and RMR were not significantly changed by CP supplementation. No significant differences in fasting plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or in iron and zinc indices were found between the two groups over time. Serum total cholesterol concentration significantly decreased (p = 0.0016) over time for all subjects combined, probably as a result of the exercise training. Exercise training significantly reduced total iron binding capacity (TIBC) by 3% for all subjects combined (p = 0.001 1). CONCLUSIONS: Twelve weeks of 400 microg/day of chromium as a CP supplement did not significantly affect body composition, RMR, plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or iron and zinc indices in moderately obese women placed on an exercise program. The changes in serum total cholesterol levels and TIBC were a result of the exercise program.

Adult↗
PubMed1997

Biokinetics and dosimetry of chromium, cobalt, hydrogen, iron and zinc radionuclides in male reproductive tissues of the rat.

Following intravenous administration to male rats, the uptake and retention by reproductive tissues of chromium-51, cobalt-57, iron-59, zinc-65 and tritium has been studied for up to 28 days. Chromium-51, 57Co, 59Fe and 3H were not or only transiently accumulated in gonads or accessory sex glands at concentrations greater than whole body concentrations. However, 65Zn was concentrated in the dorsolateral region of the prostate gland and autoradiography showed preferential uptake by epithelial cells and lumen of glands. When combined with other information available from the literature, this data would suggest that current models adequately describe the biokinetics of chromium, cobalt, iron and tritium in the prostate and testes and zinc in the testes. Uptake of zinc by the prostate would appear to be best described by an average value of 0.1% and a conservative value of 0.5%. Allowing for greater uptake of zinc (0.5%) by the prostate, after inhalation of 65Zn in a soluble form increases prostate dose by about 3 fold compared to current models. The pessimistic assumptions of a higher relative biological effectiveness (20) for all Auger emissions from 65Zn in cell nuclei and a heterogeneous distribution of 65Zn to sensitive cells in the prostate increases prostate dose by a further factor of 9. Even on the basis of these cautions estimates, occupational exposures to radioisotopes of these elements do not explain the excess of prostate cancer reported amongst some nuclear workers.

Animals↗
PubMed2005

[Conceptuel model of transport of trace metals (chromium and nickel) in the Sebou River--Morocco].

This paper examines trace metals' behavior, mainly chromium and nickel, in Sebou River in the level located between Sidi Harazem upstream and Azib Soltane downstream. The studied level is the most exposed to pollution with heavy metals rejected by Fès stream. This often condemns tens of kilometers of Sebou and leads to a threat and an important handicap for some catches of water located downstream of the town of Fès. The purpose is then to develop a physicochemical model simulating trace metals' behavior (Cr and Ni) in Sebou River. This model combines transport phenomena (advection and dispersion) with physical and chemical processes studied in the two compartments of the river: water column and sediment as sorption, diffusion, deposition, resuspension and burial. These processes are grouped under a conceptual model diagram and converted into an equations system solved by numeric methods. The model calibration uses a data of suspended matter, nickel and chromium concentrations measured in water column and sediment. Results shown in this paper are related to model development and calibration. They are consistent with the possibility of simulating the evolution for nickel, chromium and the suspended matter concentrations along the Sebou River.

Chromium↗
PubMed2005

Effect of MnSO4 on the chromium removal from the leather industry wastewater.

Chromium (VI) is one of the heavy metals in water and wastewater that has the most toxic characteristic. Consequently, it is dangerous for human and environmental health. Various methods are used for removal of the chromium from wastewater, and new methods have been developed in recent years. Recent studies and investigations on the removal of environmental pollution selected methods that were economical, of optimum efficiently and could be carried out easily. In this study, the removal of Cr6+ in the leather industry wastewater is investigated using MnSO4 that was used easily and economically. Experimental studies are performed in two phases. In the first phase, the optimum MnSO4 dose for removal of Cr6+ was determined. In the second phase, the optimum pH was studied. About 96% removal of chromium was launched with 530 mg l(-1) MnSO4 dose at pH value 9 in the wastewater sample.

Animals↗
PubMed1997

Airborne hexavalent chromium in southwestern Ontario.

This study reports the first field measurements of airborne hexavalent chromium (Cr(vi)) in southwestern Ontario. Hexavalent chromium was identified as an inhalation carcinogen and an air toxic of concern during the 1991-93 Windsor Air Quality Study. The results of that study indicated that approximately 20% of the routinely monitored ambient airborne chromium (Cr) was in the hexavalent form. In addition, the range of carcinogenic health risks attributable to airborne Cr(vi) was determined to be between 1.4 x 10(-5) and 3.0 x 10(-4) for people living in the Windsor area. During the summer of 1993, analyses of concurrent indoor and outdoor 24-hour air quality samples taken at 33 residences in Hamilton resulted in geometric mean Cr(vi) concentrations of 0.20 ng/m3 and 0.55 ng/m3, respectively, and little or no relationship between the indoor and outdoor sample sets. During the summer of 1994, an airborne Cr(vi) size-fraction study was conducted in Hamilton, the results of which suggested that the majority of the Cr(vi) was in the inhalable fraction.

Air Pollutants↗
PubMedDate not supplied

Chromium toxic effect monitoring using ozonation method.

The hexavalent chromium toxicity (in vitro) to plasma, erythrocytes, and semen lipids was evaluated. The ozonation technique is suggested to realize the rapid measurements of the lipid peroxidation (LPO) by means of the double bond indexes (DB-index and DB(cell)-index) calculation. The obtained experimental results permit to conclude that it is possible to detect the chromium effect on LPO by ozonation. The DB-index and DB(cell)-index determination in the plasma, erythrocytes, and sperm can be considered as a measure of this effect. Ozonation, suggested in this work, can provide the useful preliminary information for specialists and is a quantitative, fast, inexpensive, and simple method. In view of these comments, we conclude that the suggested ozonation method can be considered as the acceptable modern technique for the chromium toxic effect monitoring in vitro.

Adolescent↗
PubMed2006

Factors affecting the adsorption of chromium (VI) on activated carbon.

The aim of this investigation was to determine the adsorption behavior of chromium (VI) on two different activated carbon samples produced from Tuncbilek lignite. The effects of the initial chromium (VI) concentration (250-1000 mg/L), temperature (297-323 K) and pH (2.0-9.5) on adsorption were investigated systematically. The effectiveness of the parameters on chromium adsorption was found to be in the order of pH, the initial Cr(VI) concentration and the temperature. Increasing the pH from 2.0 to 9.5 caused a decrease in adsorption. However, the adsorption was increased by increasing the initial Cr(VI) concentration and temperature. The multilinear mathematical model was also developed to predict the Cr(VI) adsorption on activated carbon samples within the experimental conditions.

Adsorption↗
PubMed2003

Human health risk and exposure assessment of chromium (VI) in tap water.

Hexavalent chromium [Cr(VI)] has been detected in groundwater across the United States due to industrial and military operations, including plating, painting, cooling-tower water, and chromate production. Because inhalation of Cr(VI) can cause lung cancer in some persons exposed to a sufficient airborne concentration, questions have been raised about the possible hazards associated with exposure to Cr(VI) in tap water via ingestion, inhalation, and dermal contact. Although ingested Cr(VI) is generally known to be converted to Cr(III) in the stomach following ingestion, prior to the mid-1980s a quantitative analysis of the reduction capacity of the human stomach had not been conducted. Thus, risk assessments of the human health hazard posed by contaminated drinking water contained some degree of uncertainty. This article presents the results of nine studies, including seven dose reconstruction or simulation studies involving human volunteers, that quantitatively characterize the absorbed dose of Cr(VI) following contact with tap water via all routes of exposure. The methodology used here illustrates an approach that permits one to understand, within a very narrow range, the possible intake of Cr(VI) and the associated health risks for situations where little is known about historical concentrations of Cr(VI). Using red blood cell uptake and sequestration of chromium as an in vivo metric of Cr(VI) absorption, the primary conclusions of these studies were that: (1) oral exposure to concentrations of Cr(VI) in water up to 10 mg/L (ppm) does not overwhelm the reductive capacity of the stomach and blood, (2) the inhaled dose of Cr(VI) associated with showering at concentrations up to 10 mg/L is so small as to pose a de minimis cancer hazard, and (3) dermal exposures to Cr(VI) in water at concentrations as high as 22 mg/L do not overwhelm the reductive capacity of the skin or blood. Because Cr(VI) in water appears yellow at approximately 1-2 mg/L, the studies represent conditions beyond the worst-case scenario for voluntary human exposure. Based on a physiologically based pharmacokinetic model for chromium derived from published studies, coupled with the dose reconstruction studies presented in this article, the available information clearly indicates that (1) Cr(VI) ingested in tap water at concentrations below 2 mg/L is rapidly reduced to Cr(III), and (2) even trace amounts of Cr(VI) are not systemically circulated. This assessment indicates that exposure to Cr(VI) in tap water via all plausible routes of exposure, at concentrations well in excess of the current U.S. Environmental Protection Agency (EPA) maximum contaminant level of 100 microg/L (ppb), and perhaps those as high as several parts per million, should not pose an acute or chronic health hazard to humans. These conclusions are consistent with those recently reached by a panel of experts convened by the State of California.

Air Pollution, Indoor↗
PubMed1987

Distribution and HPLC study of chromium-51 binding sites in Chinese hamster ovary cells.

Chinese hamster ovary cells were cultured with chromium-51 chromate to study the site of chromium interaction with cell biomolecules. After incubation, cells were homogenized and separated into nuclear, mitochondrial, microsomal, and cytosolic fractions. Greater than 75% of the radioactivity was found in the cytosolic fraction. The supernatant from the centrifuged cell homogenate, which contained greater than 90% of the chromium radioactivity, was subjected to chromatographic investigation. The combination of anion exchange and ion-pair high-performance liquid chromatography (HPLC) showed that at least three different molecular species interact with chromate or its reduced derivative, Cr(III). These species are glutathione, the nucleotides cytosine triphosphate, uridine triphosphate, guanine triphosphate, adenosine triphosphate, and adenosine diphosphate, plus an as yet unknown species of protein or peptide. Preliminary data for the specific activity of nucleoside triphosphates range from 6000 to 18,000 cpm/micrograms ribonucleoside triphosphate. The glutathione accounted for 50% of the observed radioactivity, the nucleotides for 30%, and the metalloprotein accounted for the remainder.

Animals↗
PubMed1992

Review of the allergic contact dermatitis hazard posed by chromium-contaminated soil: identifying a "safe" concentration.

At least 200 sites in the United States contain soil with elevated levels of trivalent and hexavalent chromium [Cr(III) and Cr(VI)]. Although the potential cancer hazard posed by airborne Cr(VI) has been the primary concern for these sites, a soil cleanup standard based on the potential elicitation of allergic contact dermatitis has been proposed for sites in Hudson County, N.J. This paper describes the rationale for identifying a soil concentration of Cr(VI) that should not pose an allergic contact dermatitis hazard-even in sensitized persons. A literature review of eight published patch test studies that evaluated the allergic response to potassium dichromate was conducted. These studies were evaluated for clinical and statistical relevance in establishing a threshold dose of Cr(VI) to which no more than 10% of the subpopulation sensitized to chromium would respond, and that would protect at least 99.84% of the general population. Although each of the studies had certain methodological limitations when evaluated against current test methods, the data set proved useful for deriving an estimated threshold. Using computer data-fitting techniques based on truncated lognormal distributions, a weighted mean 10% threshold of approximately 150 ppm potassium dichromate or 54 ppm Cr(VI) was identified for the eight studies. Due to the types of limitations noted for these studies, this threshold is likely to be somewhat conservative. Test results have shown that between 5 and 10% of the Cr(VI) at concentrations less than about 500 ppm are released from a soil matrix into an isotonic saline solution simulating sweat. Using human sweat as the extractant, it has been shown that only 0.1% of the CR(VI) at concentrations of approximately 1,000 ppm are released from a soil matrix into sweat. Based on 10% solubilization of soil-bound Cr(VI) and the results of our statistical analysis of previous threshold studies, a concentration of approximately 350 to 500 ppm Cr(VI) in soil should be sufficiently low to protect virtually all exposed people, including children, from chromium-induced allergic contact dermatitis.

Chromium↗
PubMed1992

Field evaluation of a sampling and analytical method for environmental levels of airborne hexavalent chromium.

Hexavalent chromium, Cr(VI), has been classified as a human respiratory carcinogen. Airborne Cr(VI) emissions are associated with a number of industrial sources including metal plating, tanning, chromite ore processing, and spray painting operations; combustion sources such as automobiles and incinerators; and fugitive dusts from contaminated soil. There has been considerable interest within industry and the regulatory community to assess the potential cancer risks of workers exposed to Cr(VI) at levels substantially below the threshold limit value (TLV) of 50 micrograms/m3. To date, only the workplace sampling and analytical method (National Institute for Occupational Safety and Health [NIOSH] Method 7600) has been validated for measuring airborne Cr(VI), and it can accurately measure concentrations only as low as 500 ng/m3. This paper describes the field evaluation of a sampling and analytical method for the quantitation of airborne Cr(VI) at concentrations 5000 times lower than the current standard method (as low as 0.1 ng/m3). The collection method uses three 500-mL Greenberg-Smith impingers in series, operated at 15 Lpm for 24 hr. All three impingers are filled with 200 mL of a slightly alkaline (pH approximately 8) sodium bicarbonate buffer solution. The results of validation tests showed that both Cr(VI) and trivalent chromium, Cr(III), were stable in the collection medium and that samples may be stored for up to 100 days without appreciable loss of Cr(VI). Method precision based on the pooled coefficient of variation for replicate samples was 10.4%, and method accuracy based on the mean percent recovery of spiked samples was 94%. Both the precision and accuracy of the impinger method were within NIOSH criteria. This method could be used to measure ambient concentrations of Cr(VI) in the workplace caused by fugitive emissions from manufacturing processes or chromium-contaminated soils at workplace concentrations well below the current TLV (50 micrograms/m3) or permissible exposure limit (100 micrograms/m3).

Air Pollutants, Occupational↗
PubMed1985

Chromium intake, absorption and excretion of subjects consuming self-selected diets.

Chromium (Cr) content of the self-selected diets of 10 adult males and 22 females was determined. Each subject collected duplicate food and beverage samples on a daily basis for seven consecutive days. The 7-day average intake for males was 33 +/- 3 micrograms (mean +/- SEM), range 22-48 micrograms, and intake for females was 25 +/- 1, range 13-36. Mean Cr intake per 1000 cal was approximately 15 micrograms. Approximately 90% of the diets analyzed were below the minimum suggested safe and adequate daily intake for Cr of 50 micrograms. Chromium absorption was inversely related to dietary intake; absorption at a dietary Cr intake of 10 micrograms was approximately 2% and, with increasing intake to 40 micrograms, Cr absorption decreased to 0.5%. These data demonstrate that the average daily intake of chromium from self-selected diets is well below the minimum suggested safe and adequate intake and that Cr absorption, at levels found in typical US diets, is inversely related to dietary intake.

Adult↗
PubMed1985

Studies in human lactation: zinc, copper, manganese and chromium in human milk in the first month of lactation.

Zinc, copper, manganese and chromium were measured in a total of 259 samples of human milk from 11 women from day of delivery to 31 days postpartum. Milk intakes by their fully breast-fed infants were calculated from 24-h test-weighing measurements. Zinc was analyzed by flame atomic absorption spectrophotometry, and the other elements by graphite furnace atomic absorption. Mean (+/- SD) concentrations declined from a maximum of 11.5 +/- 4.7 micrograms/ml at 2 days to 2.98 +/- 0.78 micrograms/ml at 28 +/- 3 days. Changes in the other three elements were irregular. The average copper concentration declined from 0.6 +/- 0.12 micrograms/ml on day 5 to 0.41 +/- 0.04 micrograms/ml at 28 days. Manganese levels decreased from a mean of 5.4 +/- 1.6 ng/ml on day 1 to 2.7 +/- 1.6 ng/ml on day 5; from 8 to 28 days there was little change, the overall mean being 3.7 +/- 2.2 ng/ml. The average concentration of chromium over the whole period was 0.27 +/- 0.10 ng/ml. Average daily intakes of the elements, by the infants, over the one month period were: zinc, 2.0 mg; copper, 0.25 mg; manganese, 2.0 micrograms; chromium, 150 ng.

Adult↗
PubMed1992

Hair chromium content of women with gestational diabetes compared with nondiabetic pregnant women.

Hair chromium concentration (HCC) of normal and diabetic pregnant women was determined by atomic-absorption spectroscopy. For nondiabetic pregnant women the value from 68 hair samples was 472 +/- 61 ng/g (mean +/- 95% CI); for gestational diabetics it was 734 +/- 155 ng/g from 42 hair samples. The difference was highly significant (P less than 0.005). Intermediate hair chromium concentrations were observed in 20 pregnant women with pregestational, overt diabetes mellitus (mean: 575 +/- 182 ng/g). Fifty-two women had a second hair sample taken later during pregnancy that showed a significant decrease in HCC (P less than 0.05). However, this decrease was confirmed only for the diabetic pregnant group. Age and parity did not influence the HCC. The data suggest that impaired utilization of chromium may be a possible etiology for gestational diabetes mellitus.

Adult↗
PubMed2000

Magnesium, zinc, and chromium nutriture and physical activity.

Magnesium, zinc, and chromium are mineral elements required in modest amounts to maintain health and optimal physiologic function. For physically active persons, adequate amounts of these micronutrients are needed in the diet to ensure the capacity for increased energy expenditure and work performance. Most physically active individuals consume diets that provide amounts of magnesium and zinc sufficient to meet population standards. Women tend to consume less of these minerals than is recommended, in part because they eat less food than men. Inadequate intakes of magnesium and zinc have been reported for participants in activities requiring restriction of body weight. Dietary chromium is difficult to estimate because of a lack of appropriate reference databases. Acute, intense activity results in short-term increases in both urine and sweat losses of minerals that apparently diminish during recovery in the days after exercise. Supplemental magnesium and zinc apparently improve strength and muscle metabolism. However, evidence is lacking as to whether these observations relate to impaired nutritional status or a pharmacologic effect. Chromium supplementation of young men and women does not promote muscle accretion, fat loss, or gains in strength. Physically active individuals with concerns about meeting guidelines for nutrient intake should be counseled to select and consume foods with high nutrient densities rather than to rely on nutritional supplements. The indiscriminate use of mineral supplements can adversely affect physiologic function and impair health.

Adult↗