Document ByzmKNZkqogLn3Ya2kpjKz1yL

FILE NAME: Trade Publications (TR) DATE: 1938 July DOC#: TR034 DOCUMENT DESCRIPTION: Trade Journal Article - Inhalation of Dust and Control of Dust Hazards < iV bon ~b i:8 <g)ciB 3 9 H 3 3 Charter Member Associated Business Papers C o n c r e t e , with which has been com bined Cement Age, New York, and Concrete Engineering, Cleveland, is devoted to the Proper Use of Concrete and the Manufacture of Cement. Published Monthly by Concrete Publishing Corporation 400 West Madison Street Chicago, Illinois Telephone CENtral 8822 CEMENT MILL SECTION of Volume 46 Established 1904 July, 1938 Number 7 Norman M. S tineman, Editor J. C. Witt, Consulting Editor A. C. Bamberger, Assistant Editor Louis Brookraan, Jr.. Business Manager L Moeller, Circulation Manager Harold O. Hayes, Promotion Manager Representatives Now York City E. Macdonald Bacon 17 West 45th--Room 909 Longacre 3*5260 Detroit Parker &,Tarbell 419 Curtis Bldg.. 2842 W. Grand Blvd. Madison 1540 San Francisco: Don Htrway Room 1009, 155 Montgomery St. Exbrook 6029 Los Angeles: Don Harway & Co. 318 West Ninth Street Tucker 9706 The Cement MtU Edition o f Concrete The Cement Mill Edition of Concrete is edited exclusively for those interested in the manufacture of Portland cement and related products. Its pages are devoted to discussion of plant design, management, operation, production effi ciency. chemical research and control, quarry op eration. progress and news of the industry. The Cement Mill Edition also contains all the material published in the corresponding Regular Edition and so provides news of the uses and merchandising of the materials whose manufacture is discussed in the Mill Edition. The Regular Section furnishes mill operating officials and mill executives valuable points of con tact with the users of the materials they produce. The subscription price is $4.00 a year in the United States and its possessions, and Mexico. One dollar additional for postage in all other countries. Current copies, 50 cents each. Charter Member CONTENTS Direct Firin g of R otary KUna____ High-Alumina Cement la Japan _ Inhalation o( Duet and Control of Dust Koxard*-- By W. C. lames 200 How Japanese Cement Manufacturera Diversify Their Actiritie --By Kanichi M oroi____ ______________________________ 202 Lehigh to Complete Rehabilitation of Two Eastern P la n ts_____204 Combine Cement and Quarry Sections of Safety Council _ 204 Methods of Protection Against SlB coris______________________2QS Editorial 207 June Cam paigns Do Pay More Diversified Production Then the Accident Curve Dropped No Bids on Federal Cement for Ohio. Wet Virginia and New J e r s e y ____________________________________________ 208 Find High Degree of Accuracy la W agner Turbidimeter ______ 209 A rgentina'* Cement Production Expanded Beyond N ations N e e d s _________________________________ _____ -- 210 Mill Equipment Men and Mills _ Copyright. 1938. by Concrete Publishing Carp CONCRETE is indexed m INDUSTRIAL ARTS INDEX, which may be consul: ad m any Technical or Public Library. Audit Bureau of Circulations C O N C R E T E -- Cem ent Mill Section - -July, 1938 Page 197 EMENT MILL Inhalation o f Dust and Control of Dust Hazards By W. C. JAMES Sdiely Engineer Portland Cement Association C ONFUSION still seems to be the dominant keynote outside the re search laboratory in this question of oc cupational " dustylung" diseases. Terms such as pneumoconiosis, silicosis, siderosis, chalicosis and even silicatosis are bandied about indiscriminately and often without meaning. Usually, the mere mention of dust in a conversation in spires visions of high mortality, high sickness rates and a long trail of serious hazards. Confusion of Terms The term " pneumoconiosis" is often interpreted to mean a disease of the lungs, resulting from dust inhalation. Actually, it means simply "dusty lung." In the early history of lung disease it was thought that all dusts caused the same disease reaction, and this term was applied to that disease. Modern research has demonstrated that most dusts are harmless. The term "pneumoconiosis" therefore should assume its primary meaning, and when applied to an indi vidual it can rightly be interpreted only as indicating that the person has inhaled dust Dr Leroy U. Cardner, referring to non specific pneumoconiosis says, " Such changes have no clinical significance and produce neither symptoms nor interfer ence with working capacity. They are of no more importance than the callouses on the palms of the hands." Any person in any environment may develop this condition. Even office workers in large industrial communities may show X-ray evidence of having inhaled dust, but such evidence is meaningless as far as health is concerned. Of the various strictly industrial dusts, coal and iron ore are perhaps the most spectacular in their appearance in the lung. Early investigators--and by this I mean investigators in the first 16 or 17 centuries of the Christian era-- were so Paper read before the Q u a r r v S e ctio n o f the Ml Ohm Safety Co n p re -;. \fa> 1). 1038. impressed by the lung pigmentation of workers in iron ore and coal that they credited these substances with a promi nent part in the development of lung disease. Modern research has demon strated that this coloring of the lung tissue is, in itself, of no significance. Only two substances are now known to cause a definite lung disease-- namely, asbestos and uncombined silica. Inhalation o f free silicon dioxide (usually quartz! in excessive quantities over a long period of time causes the disease, silicosis. You will note particu larly that three factors are necessary to the causation of this disease: 1. Free silicon dioxide (usually quartz), in particles less than 10 microns in greatest diameter. 2. Excessive concentrations. 3. Long period of exposure. No Silicosis from Cement Dust Particular emphasis should be given to these limiting factors. First, " free silicon dioxide, less than 10 microns in greatest diameter." This means exactly what it says--not calcium carbonates, not iron oxides, not silicates, not even silicon carbide (which is carborundum), but free silicon dioxide. It seems prob able that no little confusion has arisen in the minds of plant superintendents and engineers because of the timehonored practice by industrial chemists of reporting an analysis in terms of the Oxides of the components. For example, a typical reported analysis of portland cement will show a total silica content of about 20 per cent. Actually, all of this silica is combined in the forms of en tirely harmless calcium silicates; and it has been conclusively demonstrated that it is utterly impossible to acquire silicosis from exposure to cement dust. It should be mentioned that quartz is not the only form of free silica, though it is appar ently the most dangerous, and certainlv the most common, form. The various W. C. JAMES amorphous forms of the compound, such as Hint, triooli and chert, may also pro duce the silicotic reaction in the lung, but they are known to be less severe in their effect. The limiting size of ten micron- is also of importance. Particles larger than this do not reach the lungs. Further more the percentage of quartz in a given material will vary greatly with the par ticle size. A petrographic examination of shale at Saranac Laboratory under Dr. L. U. Gardner's direction, recentlv re vealed 20 per cent quartz. In a special fraction containing only large p.irl'< h-s, 40 to 50 per cent quartz was found. Dr. Gardner writes, "this is obviously due to the fact that quartz is so hard it does not fracture into fine particles." It must, therefore, be emphasized that conclusions as to the hazard existent in a dusty operation can not be based with confidence on an analysis of the parent rock. Only an analysis of the dust in the breathing zone of the operator will give an accurate picture of conditions. Question of Concentration The second limiting factor is concen tration. The exact amount of air-borne quartz that constitutes a dangerous con centration in any particular industry is not easily determined, nor is there as vet any substantial agreement as !* " ' ia* limits of quartz content should he ob served. Dr. A. J. Lanza, assistant medical di rector of the Metropolitan Life Insur ance Company, an outstanding authority on the silicosis problem, gave an exce lent summary of what needs to be known about dust concentration in his paper presented before The American Iii-titut* Page 200 July, 1938 -- C O N C R E T E -- Cem ent Mill Section enrne on is . yet bat ob- dijurrity celjwn f* rutt of Mining and Metallurgical Engineers, in February, 1937. He said: "'In the present state of our knowl edge, it is not possible to establish permissible limits of dustiness for all dusty industries or processes, as the variation both in the dust content and in external modifying conditions is so extreme. In mining, however, work ing conditions are fairly constant and it would be extremely valuable to the industry if the various mining com panies that face a silica hazard would establish, with the help of the proper governmental authorities, tentative standards practicable and applicable for their own mines. Some have done so and it is a long step in the right direction." This recommendation might well be extended to other industries. More Knowledge Is Needed The National Silicosis Conference ten tatively established a maximum of five million particles per cubic foot as a safe quartz concentration in the case of highlv siliceous dusts. This standard is subject to modification as more data are devel oped by different industries. The N a tional Silicosis Conference report also says, " It is recommended that clinical and engineering studies be carried out as rapidly as possible to establish the neces sary scientific data upon which we ma\ base practical and effective regulatorsstandards." The report then states that knowledge of three factors is necessary for establishing safe concentrations of atmospheric dust: 1. The relative number and size of the free silica and the other particles suspended at breathing levels in the different parts o f the industrial at mosphere. 2. The proportion of the workmen's time actually spent in the various dust concentrations. 3. The effects of exposure to envir onment. as revealed by the occupa tional and medical histories of old em ployees, by physical examination and by the roentgenological appearance of their lungs. Through a knowledge o f these three factors, any industry can discover what, if any. hazard it has and what preventive measures are needed. For the past two years, under the direction of Dr. Lerov L . Gardner of the Saranac Laboratory for the Study of Tuberculosis, the ce ment industry has been making a care ful estimate of the health of its workers, according to the plan just outlined. Many of the statements in this paper regarding Dust amplio? at hstnmsr mills-- raw aa<4 the effect of mixed or non-siliceous dusts have been based on the findings of these studies. One of the outstanding conclusions a student of these researches in the cement industry will reach is that concentrations of free silica appreciably higher than the maximum specified by the Silicosis Con ference are safe if the silica constitutes a moderate proportion of the total dust. Apparently a mixture of silica with other minerals, if the other minerals are pre dominant. tends to inhibit the effect of the silica in the lung. It is not vet pos sible to recommend, without reservation, the dilution of silica with other dusts as a protective measure. It is far better to remove the dust from the atmosphere. Nevertheless, it is significant that in the portland cement industry, where a high concentration of raw material dust con taining up to 10 per cent of free silica is sometimes found, the X-rays and phys ical examinations reveal no pathological lung condition attributable to dust. The Practical Limit Although no agreement has been reached as to the maximum safe concen tration of free silica in the presence of harmless dusts, agreement as to good housekeeping limits is practically unan imous. Industries with a dusty process, even though dusts are harmless, should endeavor to reach a concentration in the neighborhood of 100 million particles per cubic foot of air in the breathing zone of the workers, in the interests of comfort and increased efficiency. The third factor in the development of silicosis is duration of exposure. The problem of exposure resolves itself into two parts. First, what proportion of the workers' time is actually spent in the dusty atmosphere? It is evident that a hazardous dust will not affect a man unless he is actually exposed to it and will not have as great an effect on a man who is exposed to it one hour a day as on a man continuously exposed, [Thr remaining part of this paper tiill discuss the effect of duration ot exposure, follotied by <s discussion of preventive measures.--Editor. ] Plan New Cement Plant for Turkey A c c o r d in g to a report to the l . s . Bureau of Foreign and Domestic Commerce from the office of the Ameri can Commercial Attache at Istanbul, the Turkish Government has awarded a con tract to a European equipment manufac turer for cement mill machinery to be installed in a new plant at Sivas. Installation of the machinery is ex pected to start in October of this year, and the plant should enter into operation in July, 1939. with a daily production capacity of 300 tons, or 90.000 tons per year. In view of the abundance of raw material in the surrounding district, it is hoped that the factory will soon be able to double its production. The quarries will be connected with the plant bv an aerial line of 3.100 meters, ft is antici pated that when this factors- enters into production the Eastern Vilayets and Cen tral Anatolia will be supplied with ce ment at considerablv lower prices. C O N C R E T E -- Cement Mill Section -- July. 1938 Page 201 ze-^nm n