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PubMed1997

Effects of chromium on lymphocyte subsets and immunoglobulins from normal population and exposed workers.

Blood lymphocyte subsets and serum immunoglobulins were studied in 15 men (mean age: 35 years), not exposed to toxic agents, and in 15 healthy men, exposed to dust containing several compounds (including lead chromate), working in a factory producing plastic materials. Worker blood lead and urine chromium (Cr) levels were significantly higher than controls, while serum Cr concentration was unchanged. In the worker blood, CD4+ helper-inducer (mainly CD4+-CD45RO- "virgin"), CD5--CD19+ B, CD3--CD25+ activated B and CD3--HLA-DR+ activated B and natural killer (NK) lymphocytes were significantly reduced (about 30-50 %). The investigated workers were exposed to hexavalent Cr, as lead chromate, whereas normal population (control group) was mainly exposed to trivalent Cr. In the control group, urinary Cr showed a significant positive correlation with CD16+-56+ NK, CD5+-CD19+ B and HLA-DR+ activated T, B and NK lymphocytes and a negative correlation with serum IgA immunoglobulins; moreover, serum Cr was significantly correlated with all blood lymphocytes and HLA-DR+, CD3--HLA--DR+ and CD3--CD25+ lymphocyte subsets. These data suggest that trivalent Cr may be involved in mechanisms regulating the immune response in humans.

Adult↗
PubMed1994

Human exposure to urban air pollution.

This study deals with some methods of making human exposure estimates, aimed at describing the human exposure for selected air pollutants in Sweden that are suspected carcinogens. Nitrogen oxides (NOx) have been chosen as an indicator substance for estimating the concentration of the urban plume. Earlier investigations have shown that the traffic in Swedish cities contributes around 85% to the measured NOx concentrations, and that most of the mutagenicity in urban air originates from traffic. The first section of this paper describes measurements in Stockholm of some unregulated light hydrocarbons, such as ethene, ethyne, propane, propene, butane, and isobutane. In addition, measurements of some volatile aromatic hydrocarbons are presented. Simultaneous measurements of carbon monoxide (CO) were made. The ratios between CO and the individual specific compounds were determined by linear regression analysis. By analysis of relationships between CO and NOx, NOx concentrations can be used as a tracer to describe the exposure for these specific compounds. NOx are considered to be a better tracer than CO, because NOx or NO2 values exist for many places over a long time, while CO is measured mostly in streets with high concentrations. At low concentrations, instruments that measure normal CO levels give no detectable signals. Through use of atmospheric dispersion models and models that describe how people live and work in urban areas it has been possible to describe the average exposure to NOx in cities of different sizes. The exposure to NOx for people living in the countryside has also been estimated. In this way, it has been possible to calculate the average exposure dose for NOx for the Swedish population. This figure is 23 micrograms/m3. By use of the relationships between NOx and specific compounds the average dose has been calculated for the following compounds: polyaromatic compounds (PAH); ethene, propene, and butadiene; benzene, toluene, and xylene; formaldehyde and actaldehyde; nickel, chromium (VI), arsenic, and cadmium; asbestos; and silicon.

Air Pollution↗
PubMed1980

Rec assay and mutagenicity studies on metal compounds.

We carried out rec assays on 127 metal compounds with Bacillus subtilis to check their DNA-damaging capacity and mutagenicity. Certain compounds of beryllium, cobalt, cesium, iridium, osmium, platinum, rhodium, antimony, tellurium, thallium and vanadium were newly found to be positive in addition to those of known positive metals such as arsenic, cadmium, chromium, mercury, molybdenum and selenium. Reverse mutation assays with Escherichia coli and Salmonella strains showed that compounds of rhodium (RhCl3), tellurium (Na2H4TeO6, Na2TeO3) and platinum (PtCl4, (NH4)2PtCl6) are potent mutagens.

Bacillus subtilis↗
PubMed1988

[Evaluation of intraocular metallic foreign bodies by multi-element neutron activation analysis].

Multi-element neutron activation analysis method was applied to the determination of metallic foreign bodies which penetrated into the eyes of workers while engaged in grinding and cutting work. A total of 23 small pieces ranging in size from 1 to 10(2) mg were surgically obtained and then analyzed non-destructively with only simple washing treatment. The components of 21 samples were mainly iron and the others were hard pieces of wolfram compound. Elements determined in samples over one weight percent were iron, manganese, chromium, wolfram, and cobalt. All the samples were divided into five classes according to their own elemental composition. It was considered that foreign bodies were composed of carbon steel, steel alloy, and tungsten carbide. These results are regarded to be useful in studying the mechanism of accidents and their effects on eyes.

Eye Foreign Bodies↗
PubMed1982

[Investigations of the pathogenesis of lung cancer observed among chromate factory workers].

In order to clarify the relationship between the chromate compound and occurrence of lung cancer, the author studied the characteristics of patients with lung cancer among workers of chromate factory and measured the chromium contents of each tissues obtained from 14 patients at surgery and autopsy. The incidence of the chromate lung cancer was 413 per 100,000 population, which was 16 times that of the general population. All were male. The age ranged from 26 to 74 year old (average 53). The histological type was mostly squamous and small cell carcinoma. Location of carcinoma occurrence was mainly limited to the large bronchi. The average total labor period of patients with lung cancer was 258 months and the latent period was 305 months. The working history of the patients in hexavalent-chromium producing process was longer than that of the control group. Patients with small cell carcinoma was mainly engaged in the monochromate producing process. The labor and latent period of patients with squamous cell carcinoma was longer than those of small cell carcinoma. Measurement of chromium contents in the respiratory system of chromate workers revealed much higher chromium content than in control group. The chromium content of tissues in the non-respiratory system was a little higher than that of the control group. High chromium content itself did not have any relation with the occurrence of lung cancer because the primary location of chromate lung cancer was limited to the large bronchi, not to the peripheral lungs which contained the highest chromium content. The longer was the exposure period, the higher was chromium content in the lung. Chromium content in the upper lobe was higher than that in the lower lobe. From these studies, the author concluded that hexavalent-chromate compound might be the compound responsible for lung cancer occurrence.

Adenocarcinoma↗
PubMedDate not supplied

Effects of local cooling rate and processing variables on leucite in dental porcelain.

PURPOSE: This research determined whether there is a measurable effect of local geometry factors on leucite content of dental porcelain in fixed partial dentures (FPD). MATERIALS AND METHODS: Four-unit FPD frameworks (n = 36) were fabricated using a nickel-chromium alloy (Rexillium III). Body porcelain (Crystar, shade A2) was applied in one increment and subjected to two simulated body firings, followed by a simulated glaze firing to achieve a thickness of 1.5 to 2.0 mm. The completed FPD specimens were randomly assigned to three groups of 12 specimens each: (1) simulated post-soldering, (2) multiple firing, and (3) control. The FPDs from each test group were sectioned into individual units: canine retainer, premolar pontic, molar pontic, and molar retainer. The porcelain was removed from each unit, and the leucite content was measured via quantitative x-ray diffraction. RESULTS: Porcelain cracking indicated that the soldering simulation had successfully reproduced conditions in the dental laboratory that result in porcelain cracking during soldering. The leucite content was not significantly different between the retainer and pontic units for either the soldering simulation or control FPDs, although the canine retainer units did have a slightly lower leucite content than the pooled values of the other units. Comparison of the pooled data for the three groups indicated statistically significant differences among the leucite contents. CONCLUSION: Compared to the control, the simulated post-soldering procedure produced a significant increase in leucite, and the multiple firing group exhibited a significant decrease in leucite. Increases in leucite weight fraction during post-soldering operations-and the larger thermally induced stresses that accompany these leucite increases-are responsible for the cracking that occurs.

Aluminum Silicates↗
PubMed2007

Linkage effects of chromium(III) acetylacetonato units on chiral induction of liquid crystal phases.

The linkage effects of polynuclear metal complexes on chiral induction have been studied by application of the chiral oligomers of acetylacetonato chromium(III) units as a dopant, inducing chiral nematic phases. The compounds were prepared by reacting [Cr(acac)(3)] (acac = acetylacetonato) and 1,1,2,2-tetraacetylethane (taetH(2)) in solid phase at 160 degrees C. Binuclear diastereomers were separated on a silica gel column, followed by chromatographic resolution on a chiral column packed with an ion-exchange adduct of Delta-[Ru(phen)(3)](2+) (phen = 1,10-phenanthroline) and synthetic hectorite. An enantiomeric pair (DeltaDelta- and LambdaLambda-[Cr(acac)(2)(taet)Cr-(acac)(2)]) and a meso species (DeltaLambda-[Cr(acac)(2)(taet)Cr(acac)(2)]) were identified. The binuclear enantiomers were doped into a room-temperature nematic liquid crystal, N-methoxybenzylidene-4-n-butylaniline. Helical twisting power (beta(M)) was found to be +97.9 and -88.9 microm(-1) for LambdaLambda- and DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)], respectively. The values were compared with beta(M) for the monomeric enantiomers (+99.5 and -91.0 microm(-1) for Lambda- and Delta-[Cr(acac)(3)], respectively). The results are interpreted on the basis of the surface chirality model. DeltaDelta-[Cr(acac)(2)(taet)Cr(acac)(2)] was found to photoisomerize both in a hexane solution and in a liquid crystal phase of ZLI-1132. The quantum yield of photoisomerization in a liquid crystal phase was lowered to ca. 30% of that in a hexane solution.

Journal Article↗
PubMedDate not supplied

Metals and metal compounds in carcinogenesis.

Several metals and metal containing compounds are potent mutagens and carcinogens. The most often blamed are chromium, arsenic, nickel, vanadium, iron, copper and manganese. Although each of them has its own mechanism of action, it is believed that most of their mechanisms of action involve reactive oxygen species (ROS). Furthermore, nickel modulates gene expression by induction of DNA methylation and/or suppression of histone acetylation. Arsenic activity on cell metabolism is multiple; it seems that cell transformation is induced by long-term exposure to a low level of arsenic. The paradox of arsenic is that it has also a valuable therapeutic efficacy in cancer treatment. Manganese is known to cause DNA damage, although it does not represent a significant carcinogenic risk. Magnesium deficiency and iron excess are not exactly carcinogenetic, but certain concentrations of these metal ions are needed to prevent cancer.

Carcinogens↗
PubMed2004

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from catalytic and thermal oxidizers burning dilute chlorinated vapors.

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) have been found from 57 field tests on the oxidation of low (a few to a few hundred) parts per million levels of chlorinated and non-chlorinated volatile organic compounds (VOCs). The oxidation occurs in catalytic oxidizers with platinum, platinum/palladium or chromium(IV) oxide combustion catalysts, or in thermal oxidizers (without a catalyst). The catalyst inlet temperatures ranged from 293 to 573 degrees C. The thermal oxidizer operating temperatures (post-flame) were from 773 to 927 degrees C. Data of the toxic dioxin and furan isomers are reported and also weighted and expressed as international toxic equivalents (TEQ) of 2,3,7,8-tetrachlorodibenzo-p-dioxin. The maximum stack emissions, 1.07 ng/m3 TEQ, occurred at 293 degrees C. Salient results of this field study are: (1) TEQ levels in the stack exponentially increase with a decrease in operating temperature, an empirical equation is TEQ (ng/dscm)=8.4 exp(-0.0084T degrees C); (2) dioxin/furan production occurs at the combustion catalyst; (3) small variations in temperature cause large changes in the congener distribution of the dioxin and furan isomers; (4) molar TEQ yields from the parent compounds fed to the oxidizers are very small (10(-9)-10(-13)); (5) catalytic and thermal oxidizers may destroy dioxins fed from the ambient air; and (6) the oxidation of chlorinated VOCs with non-chlorinated VOCs reduces emissions of dioxins, likely due to the consumption of Cl in producing HCl. Laboratory investigations are needed to understand how dioxins are formed (and emitted) under conditions of this study.

Air Pollutants↗
PubMedDate not supplied

Chromium-induced genotoxicity and apoptosis: relationship to chromium carcinogenesis (review).

The adverse health effects linked with chromium (Cr) exposure, the role of solubility and chemical speciation of Cr compounds, and the diverse cellular and molecular effects of Cr make the study of Cr carcinogenesis and toxicology very interesting and complex. Certain Cr compounds are prominent metal carcinogens in both occupational and environmental settings. Inhaled particulate forms of hexavalent Cr [Cr(VI)] cause lung cancer as well as lung toxicity. Some of the important factors in determining the biological outcome of Cr exposure include the bioavailability, chemical speciation and solubility of Cr compounds, intracellular reduction, and interaction of Cr with DNA. The stable oxidation states of Cr found in nature are Cr(III) and Cr(VI). Cr(III) is unable to enter cells but Cr(VI) enters into cells through membrane anionic transporters. Intracellular Cr(VI) is metabolically reduced to the ultimate Cr(III). Cr(VI) does not react with macromolecules such as DNA, RNA, proteins and lipids. However, both Cr(III) and the reductional intermediate Cr(V) are capable of co-ordinate covalent interactions with macromolecules. At the genomic level, Cr genotoxicity manifests as gene mutations, several types of DNA lesions and inhibition of macromolecular synthesis. At the cellular level, Cr exposure may lead to cell cycle arrest, apoptosis, premature terminal growth arrest, or neoplastic transformation. Cr-induced DNA-DNA interstrand crosslinks (DDC), the tumor suppressor gene p53 and oxidative processes are some of the major factors that may play a significant role in determining the cellular outcome in response to Cr exposure. We have utilized cellular, molecular, pharmacological, and genetic approaches to understand the interrelationship between Cr-induced genotoxicity, apoptosis and carcinogenesis. This review is based on the results and inferences of this research. We hope this review will clarify existing concepts and also introduce novel perspectives in chromium carcinogenesis research.

Animals↗
PubMed1989

Protection of gastric epithelial cell monolayers from a human cell line by omeprazole in vitro.

Omeprazole has an anti-ulcerogenic effect and protects rat gastric mucosa against drug-induced damage in vivo. We have evaluated omeprazole protection against damage induced by sodium taurocholate to gastric epithelial cell monolayers, an experimental model that completely excludes the influence of systemic factors. Furthermore, since our model consists of mucus-producing cells, the acid inhibitory effect of the drug in any protection is negligible. The role of prostaglandin and sulfhydryls in any such protection has also been evaluated. Monolayers of gastric cells from a well-differentiated human cell line were studied. A chromium-51 release assay was used to assess cell damage. Sodium taurocholate damaged cells dose-dependently (r = 0.97, p less than 0.01). Pretreatment with omeprazole significantly reduced the amount of cell damage brought about by sodium taurocholate (p less than 0.001). Indomethacin did not prevent the protection afforded by omeprazole, nor did incubation with omeprazole increase the amount of prostaglandin E2 produced by cultured cells. Omeprazole did not increase the amount of sulfhydryl compounds in cultured cells. These results indicate that omeprazole protects gastric cells independently of systemic factors and of inhibition of gastric acid secretion. This protection is not related to stimulation of prostaglandin synthesis nor is it associated with an increase of endogenous sulfhydryl compounds.

Cell Line↗
PubMed1993

Chromium in human nutrition: a review.

This review summarizes the results of 15 controlled studies supplementing defined Cr(III) compounds to subjects with impaired glucose tolerance. Three of these (3-4 mumol Cr/d for > 2 mo) produced no beneficial effects: serum glucose, insulin and lipid concentrations remained unchanged. The remaining 12 interventions improved the efficiency of insulin or the blood lipid profile of subjects (ranging from malnourished children and healthy middle-aged individuals to insulin-requiring diabetics). In addition, three cases of impaired glucose tolerance after long-term total parenteral alimentation responding to Cr supplementation have been reported. Chromium potentiates the action of insulin in vitro and in vivo; maximal in vitro activity requires a special chemical form, termed Glucose Tolerance Factor and tentatively identified as a Cr-nicotinic acid complex. Its complete structural identification is a major challenge to chromium research. The development and validation of a procedure to diagnose chromium status is the second challenge. Such a test would allow the assessment of incidence and severity of deficiency in the population and the selection of deficiency in the population and the selection of chromium-responsive individuals. The third challenge is the definition of chromium's mode of action on parameters of lipid metabolism that have been reported from some studies but not others. Future research along these lines might establish whether chromium deficiency is a factor in the much discussed "Syndrome X" of insulin resistance.

Animals↗
PubMed2005

Bioremediation potential of a perchlorate-enriched sewage sludge consortium.

The purpose of this work was to explore the reductive bioremediation potential of a perchlorate-enriched facultative anaerobic consortium. Rapid perchlorate reduction and bacterial growth were observed up to 1.84 g l(-1) of perchlorate, but not at 3.82 g l(-1) due to the toxicity. The specific growth rate of the mixed consortium was 0.1 h(-1). The consortium co-reduced perchlorate and nitrate with acetate as e- donor and carbon source. The presence of nitrate slowed down the perchlorate reduction rate. The other e- acceptors utilized include oxygen, chlorate, Cr(VI), and selenate. Over 95% of the 16 mg l(-1) of added Cr(VI) was reduced within 24 h of incubation with a high-density perchlorate-grown consortium. However, the consortium failed to couple growth with reduction of nitrite, sulfate, thiosulfate, and sulfite. During the search for autotrophic perchlorate reduction, many consortia from very diverse natural sources could not use sulfur compounds such as thiosulfate as e- donor.

Bacteria, Anaerobic↗