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At least 1,225 records · Page 68Linked to original sources
PubMed2006

Electrical discharge machining: occupational hygienic characterization using emission-based monitoring.

Hazardous potential in industrial environments is normally assessed by means of immission-based sampling and analyses. This approach is not adequate, if effects of specific technical adjustments at machine tools or working processes on hygienic parameters should be assessed. This work has focused on the optimization of a manufacturing process (electrical discharge machining, EDM), with regard to risk reduction assessment. It is based on emission analyses rather than immision analyses. Several technical EDM parameters have been examined for their influence on air-based emissions. Worktools and workpieces used have a strong influence on aliphatic compounds and metals but not on volatile organic compounds (benzene, toluene, ethylene-benzene and xylene (BTEX)) and polycyclic aromatic hydrocarbons (PAHs) in air emissions. Increasing the dielectric (mineral oil) level above processing location decreases BTEX, chromium, nickel and PAH emissions. Aliphatic compounds, in contrast, increase in air emissions. EDM current used has a positive relationship with all substances analyzed in air emissions. Indicative immission concentrations, as can be expected under EDM conditions, are estimated in a predictive scenario. The results of this characterization give rise to an important conclusion in that risk assessment so far has been using incorrect parameters: total aliphatic compounds. Maximum level of chromium is reached long before limit values of aliphatic compounds are exceeded. Because of the fact that metals, like chromium, also have a higher hazardous potential, metal analysis should be introduced in future risk assessment. This experimental approach, that captures total emission of the electrical discharge machine, and is not solely based on immission values, has lead to a better understanding of the production process. This information is used to extract recommendations regarding monitoring aspects and protection measures.

Air Pollutants, Occupational↗
PubMed1997

Genotoxicity of selected metal compounds in the SOS chromotest.

Knowledge concerning the genotoxicity of inorganic metal compounds in the SOS chromotest is limited. Up to now, only Cr(VI), Sn(II) and the platinum antitumor compound cisplatin(II) were shown to be genotoxic in this test system. However, for Cr(VI) and Sn(II), a positive reaction could only be achieved in cytotoxic dose ranges. The aim of the present study was to provide additional data concerning metal salt genotoxicity in the SOS chromotest. Therefore, 14 metal/metalloid salt compounds of platinum, palladium, rhodium, arsenic, antimony and chromium were tested. Four platinum salts, K2PtCl4, cis-Pt(NH3)2Cl2 (cisplatin), trans-Pt(NH3)2Cl2 (transplatin) and PtCl4 as well as two rhodium compounds tested, K2RhCl5 and (NH4)3RhCl6, could be shown to be genotoxic in the chromotest using the tester strain Escherichia coli PQ37. A moderate genotoxicity was shown by the two Cr(VI) compounds K2CrO4 and K2Cr2O7. All palladium compounds and all the other metal salts tested were unable to induce a significant SOS response.

Alkaline Phosphatase↗
PubMed2001

An electrochemical coupling of organic halide with aldehydes, catalytic in chromium and nickel salts. the Nozaki-Hiyama-Kishi reaction.

[reaction: see text] Electrochemical arylation of arenecarboxaldehydes using an iron sacrificial anode in the presence of chromium and nickel catalysts afforded the corresponding arylated secondary alcohols in moderate to good yields. The chromium and nickel salts as catalysts are obtained by oxidation of a stainless steel rod during a preelectrolysis in 7% and 3%, respectively. The process was also applied to the addition of vinyl halide, allyl acetate, or alpha-chloroester to aromatic aldehydes.

Aldehydes↗
PubMed2002

Hard X-ray microprobe studies of chromium(VI)-treated V79 Chinese hamster lung cells: intracellular mapping of the biotransformation products of a chromium carcinogen.

The uptake of carcinogenic and mutagenic Cr compounds and the intracellular distribution of their biotransformation products in V79 Chinese hamster lung cells were studied by synchrotron-radiation-induced X-ray emission (SRIXE). SRIXE analysis was performed on whole cells that had been treated with either Cr(III) or Cr(V) 1,10-phenanthroline complexes, or Cr(VI). The high spatial resolution (0.3 microm) and elemental sensitivity (~10(-15) g Cr/cell) of the technique provided detailed maps of Cr and other cellular elements in thin sections prepared from Cr(VI)-treated cells. The Cr carcinogen concentrated in P-rich regions corresponding to the nucleus, as well as other areas of the cell that are likely to correspond to organelles. This is the first study that has enabled the determination of the localization of the biotransformation products of Cr(VI) carcinogens in a target lung cell.

Animals↗
PubMed1992

Nephrotoxic and hepatotoxic effects of trivalent and hexavalent chromium in a teleost fish Anabas scandens: enzymological and biochemical changes.

The effects of trivalent and hexavalent chromium (Cr3+ and Cr6+) compounds on renal and hepatic respiratory enzymes and metabolites of a freshwater fish, Anabas scandens, were studied. In a subchronic exposure of 30 days, both forms of chromium inhibited the activities of lactate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, and isocitrate dehydrogenase, whereas the hexavalent form induced greater effects. The levels of pyruvate and lactate are not exactly reflected in lactate dehydrogenase activity.

Animals↗
PubMed1996

Lesions associated with mineral deposition in the lymph node and lung of the dog.

This report includes details of the clinical and pathologic features of 31 dogs with a range of systemic illness and granulomatous lymphadenopathy associated with the presence of birefringent crystalline material within lymph nodes. Similar crystalline material was found in the lymph nodes of dogs with lymphoma (n = 9) and as an incidental finding within the canine lung (n = 9). The mineral content of these crystals was determined by electron microprobe analysis and interpreted in light of the composition of known geological or human-made compounds. A wide range of elements was identified including silicon, sulfur, copper, calcium, and aluminium, with lesser proportions of phosphorus, sodium, potassium, iron, magnesium, titanium, nickel, and chromium. Many of these compounds may have originated from exogenous natural and human-made sources, but some compounds (notably phosphates and sulfates) are uncommon or not found in nature and may have been formed within the tissues of the body (biomineralization). The inflammatory response induced by the presence of these minerals within lymphoid tissue may trigger altered immunoregulation, accounting for the spectrum of disease observed.

Aluminum↗
PubMed2006

Simultaneous photocatalytic reduction of Cr(VI) and oxidation of bisphenol A induced by Fe(III)-OH complexes in water.

Simultaneously photocatalytic reduction of Cr(VI) and oxidation of bisphenol A (BPA) in aqueous solution in the presence of Fe(III)-OH complexes were investigated under a 250 W metal halide lamp (lambda>or=365 nm). Synergy effect of the simultaneous photocatalytic oxidation and reduction of both pollutants was achieved. The effects of initial pH value, initial concentration of BPA, Cr(VI) and Fe(III) were preliminarily investigated. The results showed that both photocatalytic reduction of Cr(VI) and degradation of BPA could occur simultaneously in the Fe(III)/Cr(VI)/BPA ternary system, and the rates of photocatalytic reduction of Cr(VI) and the oxidation of BPA were more rapid at a low pH range of 2.0-3.0. The increase of the initial concentration of Fe(III) was favorable to both photocatalytic reduction of Cr(VI) and oxidation of BPA. The reduction efficiency of Cr(VI) decreased with increasing initial concentrations of Cr(VI) and BPA, but the degradation efficiency of BPA was not changed obviously at different Cr(VI) concentrations.

Benzhydryl Compounds↗
PubMed2003

Evidence of hexavalent chromium ingestion.

We describe the application of histochemical demonstration of chromium in a case of fatal ingestion of potassium dichromate in a suicide attempt. Using 2-(8-quinolylazo)-4,5-di-p-tolylimidazole (QTI), we could demonstrate chromium in the erythrocyte of the victim, in situ. This finding provides a means of proving the hexavalent chromium ingestion.

Azo Compounds↗
PubMed2005

Effect of surface reaction layer on grindability of cast titanium alloys.

OBJECTIVE: The purpose of this study was to investigate the effect of the cast surface reaction layer on the grindability of titanium alloys, including free-machining titanium alloy (DT2F), and to compare the results with the grindability of two dental casting alloys (gold and Co-Cr). METHODS: All titanium specimens (pure Ti, Ti-6Al-4V and DT2F) were cast using a centrifugal casting machine in magnesia-based investment molds. Two specimen sizes were used to cast the titanium metals so that the larger castings would be the same size as the smaller gold and Co-Cr alloy specimens after removal of the surface reaction layer (alpha-case). Grindability was measured as volume loss ground from a specimen for 1 min using a handpiece engine with a SiC abrasive wheel at 0.1 kgf and four circumferential wheel speeds. RESULTS: For the titanium and gold alloys, grindability increased as the rotational speed increased. There was no statistical difference (p>0.05) in grindability for all titanium specimens either with or without the alpha-case. Of the titanium metals tested, Ti-6 Al-4V had the greatest grindability at higher speeds, followed by DT2F and CP Ti. The grindability of the gold alloy was similar to that of Ti-6 Al-4V, whereas the Co-Cr alloy had the lowest grindability. SIGNIFICANCE: The results of this study indicated that the alpha-case did not significantly affect the grindability of the titanium alloys. The free-machining titanium alloy had improved grindability compared to CP Ti.

Alloys↗
PubMed1982

Nonciliated bronchiolar epithelial (Clara) cell necrosis induced by organometallic carbonyl compounds.

The administration of transition metal organometallic compounds such as manganese, chromium, and iron carbonyls by the i.p. route, and nickel by inhalation (mice) or intravenously (rats), resulted in selective necrosis of the nonciliated bronchiolar epithelial (Clara) cells and variable pulmonary parenchymal damage in BALB/c mice and Fischer-derived rats within 24 h of administration. The pulmonary toxicity of methylcyclopentadienyl manganese tricarbonyl (MMT), a representative of this group of compounds, was enhanced by pretreatment with piperonyl butoxide (PB), an inhibitor of the mixed-function oxidase system. This finding suggests that Clara cell necrosis can result from direct toxicity and that the specificity of toxic agents for Clara cells may not be related solely to the presence of the mixed-function oxidase system.

Animals↗
PubMed1983

High sensitivity of Salmonella TA102 in detecting hexavalent chromium mutagenicity and its reversal by liver and lung preparations.

The recently developed strain TA102, particularly suited to the detection of oxidative mutagens (Levin et al., 1983), was the most sensitive out of 9 strains of S. typhimurium his- in revealing the mutagenicity of Cr(VI) compounds (sodium dichromate, calcium chromate and chromium trioxide). The rank of sensitivity was the following: TA102, TA100, TA97, TA92, TA1978, TA98, TA1538 and TA1537, TA1535 being the only insensitive strain. Cr(III) compounds (chromic acetate, chromic nitrate and chromic potassium sulfate) were totally inactive with all strains. The direct mutagenicity of Cr(VI) was markedly decreased, through NADPH-requiring mechanisms, by rat-liver S9 fractions and, to a lower extent, by human lung S12 fractions, which supports the hypothesis of a metabolically regulated threshold in chromium pulmonary carcinogenicity.

Animals↗
PubMed1997

Health surveillance and biological effect monitoring for chromium-exposed workers.

Although workers may be exposed to chromium metal, Cr(III) compounds, and Cr(VI) compounds at the workplace, only Cr(VI) compounds are of primary concern in terms of possible health hazards. A special health surveillance program must focus on known health impairments and target organs. Medical surveillance in combination with biological monitoring can help to protect the workers' health. Biological monitoring for chromium exposure in urine, blood, and erythrocytes provides different types of information. Whereas chromium measurement in urine and whole blood or plasma is indicative of recent total chromium exposure, chromium detection in erythrocytes is attributable to Cr(VI) only and covers retrospectively a longer period of time due to the erythrocyte life span. Possibilities of biological effect monitoring are discussed.

Animals↗
PubMed2003

Tannery wastewater characterization and toxicity effects on Daphnia spp.

Tannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts. The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests. The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex. To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure. In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D. pulex (native species). Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840-27,600 mg L(-1)), chloride (1813-16,500 mg L(-1)), sulfate (230-35,200 mg L(-1)), and total solids (8600-87,100 mg L(-1)). All effluents showed extremely toxic effects on D. pulex, with 24-h mean lethal values (LC(50)) ranging from 0.36% to 3.61%. The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76%. The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%-74%). The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg N-NH(3) L(-1)) and chloride (11,300 mg Cl(-) L(-1)) contents.

Ammonia↗
PubMed1975

Epidemiology of contact dermatitis in Geneva (1000 cases).

Results concerning 1,000 cases of contact dermatitis with positive patch tests are presented. The allergens which are responsible for about 50% of our cases are: turpentine, nickel, hexavalent chromium and organic mercurial compounds. These results are compared with those of other countries. As in the industrial world there should be information given to the general public to reduce the incidence of contact dermatitis.

Chromium↗
PubMed1991

Properties of the tray adhesive of an addition polymerizing silicone to impression tray materials.

Adhesive bond strength studies for the tray adhesive of an addition vinyl polysiloxane (President) impression material were conducted with an acrylic resin, chromium-plated brass, and plastic trays. Tensile and shear stress studies were performed on the Instron Universal testing machine. Acrylic resin specimens roughened with 80-grit silicon carbide paper exhibited appreciably higher bond strengths compared with different types of tray material and methods of surface preparation.

Acrylic Resins↗
PubMed2005

[Study on the growth and spectral characteristics of Cr3+: Al2 (WO4)3 crystal].

Cr3+:Al2(WO4)3 Crystal was grown from the Na2WO4 solvent system by using the TSSG method. The absorption spectrum shows that there are two strong absorption wideband peaks and one we ak absorption peak belonging to Cr3+ ion in the crystal. The peak values of two strong absorption wideband peaks are at 422 and 595 nm, respectively. The values of two weak absorption peaks are at 684 and 663 nm, respectively. The fluorescence spectrum shows that one emission wideband peak ranging from 650 to 820 nm coexists with one stronger emission peak at 680 nm. The peak value of emission wideband is at 740 nm. The crystal field and Racah parameters were calculated, where Dq/B = 2.420 indicates that it has an intermediary crystal field. The result shows that Cr3+:Al2(WO4)3 crystal is promising for tunable laser because it not only has the spectral characteristics required for tunable laser crystal but also has the good physicochemical properties.

Algorithms↗