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By J. Gray, J. Peck

As the turn of the century approaches, traditional open pit mining methodologies and processes are being modified through the introduction and use of new technologies. As in other industries, the personal computer is dramatically changing the traditionally conservative mining industry by allowing mines of varying size and capacity to increase their productivity and efficiency through the use of easy to use, office software. Computer-based monitoring and control systems are also being used more frequently to measure and optimize, in real-time, the performances of operating equipment. When communicated to an end-user, this information can provide accurate and timely answers to questions of how much, where, when, and by whom. This capability forms the foundation of a more comprehensive, proactive management and planning facility where, ultimately, information acquired from the producing equipment will be used to optimize and control machine and human activities. As these technologies mature and become essential tools in a mine, they will eventually serve as the basis for more robotic and autonomous mining operations.

Jan 1, 1999

By Robert Cook, Valeria Zarate, Jason Hallowell

The long hole open stoping (LHOS) method is widely used in underground mining. While methods to predict stable stope geometries are well established, the ability to maintain a stable back often assumes effective ground support across the full stope span. The efficacy of the support strategy is dependent on rock jointing, quality, density, top cut width and height, and the type, amount, and orientations of bolts installed. However, it is becoming increasingly common for operators to assume narrow top cuts in service of wider stope spans with minimal bolting coverage. Failure to account for the required top cut drift size and support requirements can ultimately lead to raveling type instabilities along stope shoulders that result in back collapse. A new method has been developed to evaluate the minimum top cut dimension necessary to accommodate wider stope spans with various rock bolting configurations. Due to the economic impacts of top cut development and support, this is a critical consideration in the accurate costing and scheduling of a LHOS operation. Tables 1 lists the acronyms are used throughout this paper.

Feb 1, 2025

By AIME AIME

THE Petroleum Division will hold its first fall meeting in Tulsa, Okla., Thursday and Friday,' Oct. 2 and 3, preceding the. International Petroleum Exposition that opens there on Oct. 4. Headquarters will be at the Hotel Mayo, and members planning to attend should make reservations promptly because of the large attendance expected at the Exposition. The program for Thursday will feature production engineering problems and that for Friday the unit operation of oil pools. The principal papers planned for the various sessions are as follows:

Jan 1, 1930

By C. Nesbit, N. Duru

During the cyanide leaching process of gold and silver, ores that come from the transition zones which typically con-tains low levels of sulfide may produce one or more of the following reduced sulfur species: sulfide (HS ), polysulfides (Sn ), thiocyanate (SCN ), thiosulfate (S2O3 ), trithionate (S3O6 ), tetrathionate (S4O6 ), pentathionate (S5O6 ) and hexathionate (S6O6 ). The actual speciation of the reduced sulfur species in the circuits will primarily depend on the re-dox potential, pH, cyanide levels and existing sulfur species in recycled process water, as well as the presence of other reac-tive metal species. Development of an accurate analytical method for sul-fur species in cyanide leaching units of gold ores where sul-fur speciation occurs has an important role in explaining the metal recovery deviations. This study presents the speciation of sulfur species and development of an ion chromatography method to analyze the reduced sulfur species thiocyanate, thio-sulfate, trithionate and tetrathionate in cyanide leaching circuits for gold ores. The method developed has resulted in the precise quantification of target sulfur species in leach solutions.

Jun 1, 2024

"Coupon testing has been used to investigate stress corrosion cracking (SCC) of rockbolts in a laboratory based experimental program. This program has focused on the use of ASTM G39 three- and four-point bent beam coupon specimens, immersed in an acidified sodium chloride test solution containing hydrogen sulfide. The specimens were loaded to a range of stresses from zero, to just above the materials yield strength. It was found that only specimens above an applied stress of 580MPa failed by means of SCC, showing that rockbolts loaded to near their yield strength may be susceptible to SCC in-situ.INTRODUCTIONStress corrosion cracking (SCC) is a failure mechanism that affects material through the growth of hairline cracks when exposed to a corrosive medium while under stress (Jones and Ricker, 1999). SCC has been found to affect rockbolts in the Australian underground coal mining industry and has the capacity to cause the catastrophic failure of ground support systems, potentially leading to falls of ground in underground excavations, injury or death to mine personnel, damage or loss of equipment, and loss of productivity through the loss of roadway access (Crosky et al, 2002).Coupon testing utilises small scale samples that are intended to be indicative of the behaviour exhibited by a material in-situ (ASTM G39). The small scale, and usually high surface area to volume ratio of coupon specimens mean that they corrode at faster rate proportional to their mass, greatly reducing testing times. The small scale of the specimens allows them to be more easily prepared and handled, loaning them to mass manufacturing techniques.A previous study conducted by Vandermaat et al (2012b) into the use of three- and four-point coupon testing in-situ in an underground coal mine failed to result in SCC of the specimens. This paper serves as a follow up laboratory investigation in order to understand why these specimens did not fail. Previous studies into the SCC in rockbolts carried out by Gamboa and Atrens (2003) determined that rockbolt steel has a critical stress threshold of approximately 90% of the material ultimate tensile strength (800-900MPa). This study will focus on this critical stress threshold as a possible explanation for the lack of failure in the in-situ specimens (Vandermaat, 2012b)."

Jan 1, 2015

By Johan PEERS, François DUMORTIER

Today, solutions to optimize Capital Expenditure (CAPEX) & Operational Expenditure (OPEX) for small capacity Cold Rolling Mills (CRM) as well as for high capacity CRM are available, as extensively described by various Original Equipment Manufacturers (OEMs) & steel makers. A suitable solution for small capacity CRM is to start with a single stand reversing mill (up to 400 ktpy, depending on product mix), which can then be expanded into a twin stand mill (up to 900 ktpy, depending on product mix). The main drawbacks in conventional practice are the off-gauge length in single stand set-up and the long downtime of the mill during the erection of the second stand. For higher productions CRM, it is common practice to directly select a new Pickling Line Tandem Cold Mill (PLTCM), with a high CAPEX. Is there an in-between solution that would allow to start with limited output and CAPEX, without jeopardizing the ultimate expansion goal (1.2 to 2 mtpy), for which PLTCM is the best techno-economical choice? In the absence of a solution, JOHN COCKERILL developed an integrated solution that limits the CAPEX in the first phase of development, without crippling affecting future endeavors through an easy and economically sustainable expansion into a PLTCM, without long production downtime. The solution consists of first installing a twin stand mill, expandable into a tandem mill thanks to a smart design of the line. It is therefore possible to limit the production to 900 ktpy in the first phase of the project and then convert the mill into PLTCM in the second phase to increase the production from 1.2 to 2 mtpy, depending on the market trends and financial capabilities. In summary, JOHN COCKERILL has developed a smart new layout in reversing phase combined with a brand new rolling strategy to optimize productivity and limit off-gauge, compared to conventional solutions (patents pending). In addition the layout enables an easy conversion to tandem mill without high over investments, which is more sustainable financially than the initial purchase of a PLTCM. Long downtimes to allow for capacity extension, detrimental to this phase-by-phase approach, are also avoided. Technical and process description of the new layouts and rolling strategies, together with CAPEX & OPEX descriptions of the phases are detailed in this paper.

Oct 1, 2019

By J. M. Réjean Gagnon

"Quebec Cartier Mining Company is currently mining a low-grade iron ore deposit in northeastern Quebec. The Company is producing some 8,000,000 dry gross tons of concentrates per year, grading about 66 per cent iron. The pit, which is located on the keel or hinge line of a fold, will eventually be about 1,000 feet deep with a surface area of 8,000 by 2,600 feet. The most significant structural discontinuities in the mine are the natural bedding planes and secondary perpendicular joints. The exposed walls are subjected to a sub-Arctic climate and heavy blasting occurs approximately six times a month.QCM utilizes design and operating techniques to control rock fall. Steps are also being taken to analyze the ultimate over-all pit slope stability."

Jan 1, 1968

By John A. THOMPSON, Pazcl D. Torrey, Frank Breayster

DISCOVERY of natural gas in the Dundee field of New York in February, 1930, and the subsequent discovery in Tioga in September of that year, focused the attention of the natural-gas industry on the enormous possibilities of production and distribution in - the most populous area of the United States-New York and New England. Prior to 1926 the natural-gas industry in New York State had settled into a definite and limited policy, with the distributing companies controlling the output from its discovery to the ultimate consumer. Production amounted to between G and 7 thousand mil- lion cubic feet a year, with another 10,000 million feet imported from Pennsylvania for distribution in New York State. This gas was primarily from the Medina sand stone in. the western part of the state.

Jan 1, 1932

By Xihuai Gong, Hongshuang Di, Jianping Li, Ning Yan

In this work, we investigated the effect of the rolling process (warm-rolled or cold-rolled) on microstructure evolution and mechanical properties of 9Mn steel. After intercritical annealing at 670°C for 10min, both cold-rolled and warm-rolled microstructures are composed of ultra-fined austenite and intercritical ferrite. The austenite in warm-rolled sample includes two types of morphology, namely equiaxed and lamellar, which exhibits a wide distribution of grain-size. The incomplete recrystallization or recovery behavior of ferrite in warm-rolled and annealed sample results in higher yield strength and shorter yield point elongation. Moreover, the warm-rolled and annealed sample extends the TRIP-related work hardening over a broad strain range, resulting in a better combination of ultimate tensile strength and total elongation.

Oct 1, 2019

By Frank D. Lamb, Lloyg H. Baning

"The crushed-stone industry has long been troubled with the problem of producing a more or less cubical product for use as concrete aggregate. Its seriousness varies widely for each producer, depending upon the character of the rock employed for raw material and the ultimate use of the crushed stone. For many construction uses, such as the macadam or bituminous-concrete- type road, flat pieces are not objectionable and may even be preferable to more cubical rock. However, most specifications for concrete require that the stone must be reasonably free from flat and elongated pieces.The rigid specifications set by many contractors have resulted in the rejection of coarse aggregate that, except for the presence of an excessive amount of flat and elongated pieces, would be entirely acceptable. In many instances, if an efficient, economical method of removing flat and elongated pieces were available, local producers could meet the requirements of the contractor and thus eliminate the necessity for importing more cubical material.A brief investigation of the problem of removal of flat and elongated pieces from crushed aggregate, carried out at the Eastern Experiment Station of the Bureau of Mines, indicated that it is mechanically possible to remove flat pieces from crushed rock.TEST EQUIPMENTA number of mechanical devices are used by the coal industry for separating slate from coal; these depend upon the difference in shape of the crushed slate as compared with the coal. Such devices as shutter screens, spiral separators, and the Norman picker would be suitable for removing flat pieces from crushed rock in the same manner as they are used by the coal industry. None of these devices was immediately available for testing purposes, so an attempt was made to construct a simple device that could be used in commercial operations."

Sep 1, 1944

By Sevinc Yildirim, Cigdem Oruclus

"Metal-Porous Silicon (PS) based structures dipped in water show the direct hydrogen fuel cell behavior. The effect of the thickness of the cupper (Cu) film on the electrical properties of direct hydrogen fuel cell is studied by fabricating Cu/Porous Silicon/n-Silicon/Indium structures. PS samples were produced electrochemical etching of n-type single crystalline silicon with a resistivity of 1,25 Ocm and (111) orientation. The thin films of Cu with different thickness between 200 and 600 nm were deposited on PS surface by electron-beam technique. Investigation of the effect of Cu layer on the performance of the structure indicates that the performance parameters such as open circuit voltage (Voc) and short circuit current (Isc) strongly depend on the Cu layer thickness. It was observed that the divice with an 350 nm Cu layer exhibits the highest open circuit voltage (0,5 V), short circuit current (0,01 mA) and power density (10 W.m-2).IntroductionHydrogen is the most attractive and ultimate candidate for a future fuel and an energy carrier. Hydrogen is recognized as the environmentally desirable clean fuel of the future since it can be used directly in different types of hydrogen fuel cells [1]. In the past years, the rise in portable electronics requires the development of miniature fuel cells compatible with standard silicon micro fabrication technology. Most silicon micro-fuel cells have used the polyperfluo-rosulfonic acid membranes (Nafion R) as a proton exchange membranes (PEM) that is not really integrated with standard micro fabrication techniques [2-5]. The composite materials such as inorganicorganic hybrid materials (Nafion-silica, Nafion-borosiloxane etc) are next generation of proton conducting membrane [4-8]. But, fuel cells run on pure hydrogen gas, which can be produced with other energy resources. Hydrogen smallest atom and thus the H2 gas can leak easiliy. The application of hydrogen for power sources has been greatly restrained due to the lack of safe and convenient generation and storage methods.A kind of hydrogen fuel cells Metal-PS-Si structures used as an energy water directly. There is no need pure hydrogen. Cu-PS-Si Schottky-type fuel cells with as proton-conducting membrane and the thin-film cupper catalist and water as fuel, which are interesting for fabrication of lowcost miniature fuel cells. Generation of the open-circuit voltage and short-circuit current has been observed by Cu-PS-Si structure dipping in different hydrogen-containing solution."

Jan 1, 2014

By Tristan Worsey, John Henchion, Nathan Rouse, Yannick Lauras

"This paper presents an approach used to plan and evaluate drill and blast trials for a mine that currently mechanically excavates in-situ rock. The document presents the approach used to plan the trials, the key performance indicators (KPIs) that were necessary to evaluate the mining methods, the test matrix used during the trials, and the results of the trials. The trials, which occurred as part of an overall drill to mill optimization project at this site, helped to evaluate various blast designs using fragmentation results,drilling and blasting costs, and downstream costs. This project was unique in that (1) drill and blast methods were trialed on multiple rock types and various bench heights using a range of blasthole diameters and powder factors and (2) the load and haul costs were evaluated using a range of loading equipment, from 66 tonne (73 ton) excavators up to 250 tonne (276 ton) excavators. A ten year net cost financial evaluation of the material extraction alternatives was also prepared for the site management. Ultimately, the process of evaluating the drill and blast trials helped the management decide whether to continue extracting using mechanical methods or to introduce drill and blast methods to extract the rock."

Jan 1, 2017

By John D. Lupton

This paper will discuss the benefits and advantages of using 3D survey data in stope analysis. Obtaining detailed 3D survey data of underground mine progress and production is a challenge. It is almost impossible to ?see? around corners, underneath overhangs, or deep into dark, dusty, humid underground voids. Thus, valuable ore can remain permanently encased in backfill. Without the benefit of 3D survey data, underground mines have the difficult task of meeting grade quotas without the benefit of knowing exactly what has been mined. Lack of this data usually results in unfavorable month end Reconciliation factors, where grades must be adjusted to match grades assessed by the Mill.

Apr 1, 2005

By C. A. Alien

The increasing activity in oil shale has had a tendency to direct the attention of the industry to any substance from which gasoline or other oils can be secured . Cannel coal for many years has been known, as a source of oil and formerly it was the only substance from which kerosene was obtained . The name of coal oil was given to kerosene because it was derived from cannel coal before any flowing wells were brought in in the United States . In an isolated region in Southern Utah there is an unusually thick and clean bed of cannel coal which laboratory experiments indicate can be made to yield about seventy gallons of oil to the ton . This coal was first described in Bulletin 341 of the United States Geological Survey under the title of Colob coal field . This field lies at the western and southern base of the Colcb plateau and extends from the town of Cedar City southward to Kanarra and then southeastward to the town of Mount Carmel . Cedar City is 35 miles south of east from Lund on the Los Angeles and Salt Lake Railroad which is the nearest railroad point . Mount Carmel is about 90 miles south of Marysvale , on the Denver and Rio Grande Railroad , which is the nearest railroad point from the eastern end of the field . The Colob coal occurs in Lower Cretaceous rocks and a number of wagon mines have been opened on the seam in the vicinity of Cedar City , Kanarra , and Mt. Carmel , but between these places the field has been very little prospected . The cannel coal , so far as known at present , is limited to a small area on the head waters of the north fork of the Virgin River in Township 39 and 40 South , Range 9 East . In this region it occurs as a bed 5-1 /2 feet thick over which lies a layer of bituminous coal 2 feet and 5 inches thick .

Feb 1, 1921

By K Banerjee, C Dube

Veolia Water Technologies was contracted by a global coal mining company to design a retrofit acid mine drainage treatment facility using DenseSludge™ technology on a former coal refuse disposal site. The project constraint was to reuse current facilities in order to reduce additional capital work cost and avoid additional footprint requirements while improving treatment performance and reducing sludge production and chemical consumption. The initial installation of 454 m3/h served as a pilot plant to demonstrate the benefits of the process and ultimately provided design criteria for the new facility. The pilot demonstrated the benefit of the technology by reducing sludge volume by 90 per cent compared to conventional processes currently in use. The sludge that is reinjected into the mine contains less water, which reduces the volume of water that returns to the mine pool for treatment and mine water balance. Furthermore, the pilot plant reduced lime usage compared to conventional processes by operating at a lower pH set point, demonstrating steady pH control and stoichiometric lime utilisation.CITATION:Dube, C and Banerjee, K, 2015. Sludge conditioning technology to reduce sludge and the cost of acid mine drainage treatment, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 105–110 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

The arbitration process, and its drawbacks: Any time you have taken part in a major arbitration, and the decision, when it comes out, is not what you thought it would be (which is bound to happen occasionally), the normal reaction is something like æthe arbitrator got it wrongÆ. Again normally, when you have cooled down a bit, and you look in more detail at the decision, you can see, probably, æwhere he got it wrongÆ (it is only male arbitrators who get it wrong). Ultimately, when reason prevails, and you reflect on it, you can see that what really happened was that you failed to get the arbitrator to see what you were getting at in the point or points concerned. This is doubly frustrating, when you consider what has been involved in getting to this point, having been through it all at least twice. An alternative to this process may be the dispute review board.

Jan 1, 1999

By Nina Bianco, Diana Drinkwater

MetSkill is a professional development program for metallurgical engineers that integrates with normal duties in their first one or two years of service. Graduates work together on a structured technical project, facilitated by specialists and supported by formal learning, and ultimately reported to their technical managers. The program enables graduates to “fill the gaps” in their undergraduate education, which is increasingly pertinent as engineering degrees become more general. Participants report that they enjoy the focus on more challenging (rewarding) aspects of their jobs and feel more confident about problem solving. Sponsor companies add that the relationships developed with external technical specialists enhances opportunities for innovation and development. MetSkill was delivered to two major resource companies in Australia in 2012. This paper provides an outline of the program and the reasons for its success, and demonstrates how the learning model could be applied to groups of graduates in other engineering disciplines.

Jan 1, 2014

By C. J. Johnson, C. J. Bise

"As the US coal industry moves into the next century, it is becoming more apparent that the effective application of new technology is the only way it can remain competitive in the energy marketplace. Examples of this emphasis are with us today in such diverse areas as face-ventilation and excavation-equipment applications. The focus of this new technology is directed toward improvements in health and safety, cost control, and productivity.Room-and-pillar mining accounts for approximately 68% of the nations underground coal production; this percentage is not expected to decrease markedly in the near future. As such, this paper analyzes the impacts of the changing technological climate on future room-mid-pillar operations by comparing a base-case section (current) to three scenarios incorporating new or emerging technology. A microcomputer-based comparative analysis will reflect the changes in section production and costs.IntroductionThe ultimate goal for any coal mining company is to effectively use its human and financial resources to maximize its profits through the extraction of its reserves. Although recent workforce reductions in the industry have resulted in a more efficient use of labor and increased productivity, there comes a point in time when further reductions in the numbers of workers in each operating section are impossible with existing equipment. For example, Farinelli and Bise (1987) found that labor cost constituted 62% - 73% of the cost per ton of coal at the mining section, with a minimum crew size. Thereafter, efforts to increase productivity must focus on more efficient mine plans and technology.The fact that an increase in productivity can be realized by reducing non-productive time (change-out and tram time) and converting it to productive time has been known and demonstrated for quite some time. What has not been demonstrated frequently is the quantification of the potential productivity increase of currently emerging technology or ""add-on"" equipment. It is one thing to be able to say that a piece of equipment will make an operation more productive, but it is another thing to be able to quantify the productivity increase that will justify the purchase of the new equipment. Not only is a financial benefit possible in room-and-pillar mining with an increase in productivity, but a decrease in the time necessary to develop a longwall panel can also occur.The purpose of this paper is an analyze the impacts of a changing technological climate on future room-and-pillar operations by comparing a base-case section (current) to several scenarios incorporating emerging technology. To do this, four cases will be developed. A base case, consisting of the typical manner in which continuous-miner sections are currently operating, is compared to three layouts incorporating: (1) flooded-bed scrubbers on radio remote-controlled continuous miners, (2)a continuous miner with side-mounted roofbolters, and (3) a continuous miner with side-mounted roofbolters used in conjunction with a continuous-haulage system."

Jan 1, 1989

By R. T. Swinderman

"Virtually every article you read on safety has a statement to the effect: “It’s obvious that safety pays”. If it is so obvious, why is it so hard to answer these questions? • How does the Maintenance or Operations Manager convince the Plant Manager to spend money from the annual budget for safety improvements? • How does the Plant Manager influence Corporate to prioritize safety improvements? • How does an engineering firm persuade the owner to spend more on design and equipment up front to reduce risk? There are many cultural and structural reasons why it is so difficult to prove the obvious. In my opinion the main culprits are: the almost universally used ‘Low Bid’ process, variations in reporting incident statistics between industries and countries, and, the Generally Accepted Accounting procedures (GAAP) [or International Financial Reporting Standards (IFRS)]. Conventional wisdom is it’s smart not to spend more than you need to meet the minimum regulations and maximize production. But buying on price alone often harms people, degrades the environment, and reduces the company’s bottom line. How can this be? You met the minimum safety requirements and saved money by buying on price. Don’t those savings go right to the bottom line? When you buy on price you get minimum quality, minimum compliance and are often backed corner with no reasonable options to rectify the problems that arise from buying on price instead of buying on long term life cycle cost. Culturally few companies actually ‘walk the talk’. It is trendy to have giant billboards at plant entrances proclaiming world class compliance with quality and safety standards. Annual reports are embellished with safety slogans and sustainability statements. Behind the front gates and the glossy annual reports the message is clear: produce or be replaced. Only a few companies go beyond the window dressing and actually endorse, from the top down, continuously improving their safety culture. Those that do embrace safety, show significant performance advantages over their competition that are reflected in their safety, productivity and environmental records and, ultimately their financial statements and share price. Current accounting (and reward) systems make it unlikely financial managers will accept non-conventional approaches to justifying expenditures on safety because they are driven to report “hard” numbers that can be documented and are within the “GAAP or IFRS Rules.” But in reality, accountants quantify soft or intangible costs all the time in their financial statements. Justifying safety investments is greatly enhanced by quantifying what most financial managers would call intangible costs. Government agencies have no problem assigning intangible costs to justify regulations to improve safety. How many times have you heard that the regulation is justified because the cost to industry is X while the benefit to the society is 2 or 3X? How can they say that without including intangible costs? We find it hard to believe these government claims of benefits to society because we have been trained to think about saving hard direct costs to justify investments."

Jan 1, 2017

By N. S. Dalal, Xianglin Shi

"INTRODUCTIONEpidemiologic studies of workers in chromate-ore related industries, 1-3 and stainless steel welding and related occupations4 have shown that they have about 20-40 times higher risk of throat or respiratory track cancer than controls. Although the actual carcinogenic substances were not identified in these statistical studies, Cr(VI) compounds (for example, calcium chromate, zinc chromate, and lead chromate) were implicated as the causative agents, whereas Cr(III) compounds were not suspected as carcinogens. s These suggestions were supporte4 by laboratory studies wherein many Cr(VI) compounds produced sarcomas at the implant or injection sites.1,5 Squamous cell carcinomas and adenocarcinomas closely resembling human lung cancer were induced by intrabronchial implants of calcium chromate in rats, 6·7 whereas Cr(DI) oxide and Cr(lll) sulfate did not induce any tumor formation.6,7While the mechanism of the chromate-induced carcinogenicity is not fully understood, it is generally thought8 that it involves some damage to DNA. Specifically, it has been reported that: a) the chromate ion, henceforth referred to as chromate, can pass through the cell membrane and enter the cell while CR(DI) does not, 9 b) chromate does not interact with either native or denatured DNA 10 while Cr(III) does, 11 and c) the final Cr-DNA complex isolated from cellular reactions of chromate is Cr(III)-DNA, with Cr(III) binding to the phosphate groups.12,13 Thus the important question is: since Cr(DI) cannot pass through the membranes, how does Cr(III)-DNA complex form? For this to happen, Cr(VI) must be reduced to its lower oxidation states, 14 ultimately to Cr(III), by some reductants in the cellular environment. Unless this reduction occurs, the DNA would not be damaged and therefore no chromate carcinogenicity would ensue. Thus the reduction of chromate to its lower oxidation states seems to be a key step in the chromate carcinogenicity .1s One of the major reductants in cellular environments is thought to be glutathione (GSH), both outside and inside the cells.16-lB Some evidence for the role of GSH in the chromate toxicity was provided by recent studies showing that exposure of hamster cells to non-toxic levels of added selemite increases the levels of GSH as well as the Cr(VI)-induced DNA strand breaks,19 and that such DNA strand breaks in hepatocytes also change in direct proportion to the GSH content. 20,21 These observations were interpreted as implying that the reduction of chromate by GSH to some reactive intennediate is an important step in the chromate carcinogenicity. 20.21 In · the present undenaking22 we have used electron spin resonance (ESR) and spin-trap methodology to investigate the reduction of chromate by GSH and find evidence for the involvement of the glutathionyl radical (GS ·) as well as Cr(V)-intermediates."

Jan 1, 1990