Document GK7rZoVZE6zpRpdkRyMYvj2a4

PLAINTIFF'S EXHIBIT i COUNCIL Vol. 87, No. 6 JUNE 1963 16 Poor Robert's Almanack--Robert D. Gidel 20 Tool Trend Is Toward Built-in Safety 22 Is Safety in Your Annual Report? 26 How To Fly in Space 28 Why They Hire the Handicapped--Robert G Belknap 32 Proof the Hard Way 38 Epidemic (Diary of a Safety Engineer)--Bill Andrews 89 Dusts, Fumes, and Mists in Industry--Data Sheet 531 DHPATTMeMTS 4 Voice of the Reader 6 Accident Barometer 8 News Briefs 10 Safety Valve 14 Coming Events 30 Ideas That Worked 40 Wire from Washington 44 Off the Job 46 Fire Tips 47 Consultation Corner 49 Personals 64 Library 71 Keeping Posted S2 For Distinguished Service 85 President's Medal 106 New Safety Equipment 108 Buyers' Guide 109 Reader Service Card 117 Product Literature 118 Advertisers' index HQM&QFHCE 425 Horlii Michigan Avanu*, Chicago Now York Offices: Field Service and General Information, 270 Madison Ave, New Yodc 16 Public Service Fund, 639-40 Chrysler I New York 17 San Francisco Offices 703 Market St, San Francisco 3 Editor: James D. Saul Associate Editor: Stuart K. Hopkin* Assistant Editor: Bernard Schukraft' Technical Director: Roy Benson Contributing Editors: R. G. Belknap Carman Fish A. S. Kelly M. E. Petersen H. N. RosenfieML. C. Smith Jennie Spadafor* Lois Zearing Editorial Director: Robert L- Meyer Publications Dept. Manager: Jack Homer Director: Ralph Moses Cover: 'William Wendlani Photographer* James B Lehman Statements and opinions advanced m signed *? tides and advertisements are personal expression of the authors and advertisers, not necessanu those of the National Safety Council. Nation*!. Safety News is published monuur by National Safety Council. Copyright 1961 bt National Safety Council. Printed m U.SA. ond class postage paid at Chicago Illinois, ana** additional mailing offices Subscription xl" S7.10 a year Single copies SI 10 AU prices $u jeet to 10 per cent discount to National> aaiew Council members Quantity prices for yearjy5u_ scnptions and single issues on request. Mem*** Audit Bureau of Circulation j 38.500 c opies of this is\ue were printed He ve ' 3 ;i sc 1C m at m bi A NATIONAL SAFETY COUNCIL TECHNICAL SERVICE DATA SHEET 531 DUSTS, FUMES, AND MISTS IN INDUSTRY Copies of this data sheet will be available for purchase within 30 days. Subscribers to the CouncWs data sheet maintenance service will receive a copy in the neat quarterly mailing. Introduction 1. Industrial dusts, mists, and fumes, their hazards and their con-ol, are discussed in this data sheet.* ihe general principles presented can be applied to evaluate most in dustrial situations involving these air contaminants and to determine the need for controls. This data sheet is intended to guide employers, plant safety engineers, personnel man agers, and supervisors. 2. A plant manager-who believes that he has a toxic or irritating dust problem should consult a competent industrial hygienist Such help may be obtained from his own company, insurance carrier, private consul tants, or state health or labor agency. 3. To protect the health of em ployees who work where a dust fume, or mist created by a manufac turing process is released into the at mosphere, a control program may be required. In such a case, three steps must be taken: a. The properties of the specific dust, fume, or mist and its possible physiological effects on employees must be ascertained. 'This data sheet covers toxic and irri tating air contaminants encountered in industry. It does not include a discussion of the explosive properties of such air borne particulate matter. This data sheet is one of a series published by the National Safety Council, reflecting experience from many sources. Not every accept able safety procedure In this field is necessarily included. This data sheet should not be Con fused with American Safety Stand ards, federal laws, insurance re quirements, state laws, rules, reg ulations qr municipal ordinances. b. The particular exposure must be evaluated by dust counts or by chemical analyses of atr samples, and a step-by-step analysis of the operations must be made to find the areas where employees are ex posed to hazardous amounts of the material. The operational anal ysis also should determine how the dust, fume, or mist is dispersed. c. Appropriate methods of control must be provided where indicated. The type and extent of controls will depend upon the physical, chemical, and toxic properties of the dust, fume, or mist, the evalua tion made of the exposure, and the operauon that disperses the con taminant. The extensive controls needed for lead oxide dust, for example, would not be needed for limestone dust, since much greater quantities of limestone dust can be tolerated. 4. Except for the skin diseases, most occupational diseases are ac quired by inhalation of material. Lung tissue is by far the most efficient medium the body possesses for ab sorbing materials. In addition, the surface area of this lung tissue aver ages 55 square meters or about 590 square feet 5. Certain dusts that reach the lungs can pass directly into the blood stream and be absorbed over a long period of time. Others may stay in the_ lungs and set up local irritant or dam aging action. 6. Toxic and irritant dusts can also be ingested in amounts that may cause trouble. If toxic dust swal lowed with food or saliva is not sol uble in body fluids, it is eliminated directly through the intestinal tract Toxic materials that are readily sol uble in body fluids can be absorbed in the digestive system and picked up by the blood. 7. A third way in which toxic and irritant substances may enter the system is skin absorption. Many or ganic compounds, such as TNT, cy anides, and most aromatic amines, amides, and phenols, can produce systemic poisoning by direct contact with the skin. Contact of toxic and irritant dusts with the skin also may result in skin irritation. 8. As compared to inhalation. Mationol Safety News, June 1963 89 however, both ingestion and- skin contact are of relatively minor impor tance in industrial poisoning inso far as dusts, fumes, and mists are con ned. Origin and Properties of Particulate Matter 9. The dust normally present in the atmosphere has a beneficial effect in screening out some of the harmful rays of the sun. Inhalation of this dust may not be harmful because either the dust may be nontoxic or body mechanisms capture, remove and eliminate or isolate the small amounts of dust trapped in the lungs. Air pollution, radioactive fallout, pollens, and similar conditions may have an adverse effect on some indi viduals. Also, when the air breathed contains excessive amounts of dust, the body has difficulty in handling the load and dust may remain in the lungs. Sources 10. The term dust as used in in dustry is generally applied to air borne solid particles that cange in size from 0.1 micron to 25 microns ' me micron = 1/10,000 centimeter 1/25,000 inch). Process dusts below 0.5 micron in size are rare. Dusts above 5 microns in size usually will not stay air-borne long enough to present an inhalation problem. , 11. Dust may enter the air from various sources. It may be dispersed when a dusty material is handled, such as when lead oxide is dumped into a mixer or a product is dusted jre 1- Dwst from foundry sand is generated during the shake out of castings. The mechanical action of the shake-out machine disperses the dust. Path taken by the dust particles as they are drawn into the hood shows the efficiency of the local exhaust system. (Courtesy American Foundrymen's Society) with talc. Dust may be formed and dispersed when solid materials are reduced to small sizes in processes such as grinding, crushing, blasting, shaking, and drilling. In these proc esses, the mechanical action of the grinding or shaking device supplies a source of energy to disperse the dust formed (Figure 1). 12. When a solid such as a metal is heated to a temperature high enough to volatilize it, the volati lized matter later condenses in cooler air to form a fume (Figure 2). The solid particles that make up a fume are extremely fine, usually less than 0.5 micron in size. In some cases, the hot material reacts with the air to form an oxide. Examples are lead oxide fume from smelting and iron oxide fume from arc welding. Also, a fume can be formed when a material such as magnesium metal is burned or when welding or gas cutting is done on galvanized metal. 13. A mist is formed when a finely divided liquid is suspended in air. An example is the oil mist pro duced during cutting and grinding operations. 14. Smoke may be formed by the incomplete combustion of organic materials. Smoke generally contains droplets as well as dry particles. Tobacco, for instance, produces a wet smoke composed of minute tarry droplets. The size of the particles contained in tobacco smoke is about 0.25 micron. 15. Radioactive dust may be dis persed in the same ways as other in dustrial dusts. Radium, thorium, and other radioactive elements are pres ent in extremely minute amounts in the atmosphere. Magnitude of particles 16. When a solid is broken into finely divided particles, its surface area is increased many times. For ex ample, 1 cubic centimeter (0.061 cubic inch) of quartz in the form of a cube when crushed into 1-micron cubes will give 1012 (1,000,000,000,000 or one trillion) particles with a total surface area of 6 square meters (9,300 square inches), as compared with 6 square centimeters (0.930 square inch) for the original cube. 17. When a solid is broken into finely divided particles, the volume occupied by the mass is also in creased because of the voids between the particles. A dust concentration of 50 million particles per cubit! air (mppcf), resulting from 1 centimeter of material redui particles 1 cubic micron in size occupy an air space of 201 cubic feet. 18. Even smaller amounts of to' dusts, fumes, and mists, will makt^ workroom atmosphere hazari For example, the threshold value for lead, as adopted by th American Conference of Coven mental Industrial Hygienists, is 0 milligram per cubic meter of an (mg/cu m), which is 0.000000^ ounce per cubic foot. Therefoi the dispersion of only 0.002 o of lead will be enough to give threshold limit value of 0.2 mg/aiy of dust or fume in an air s; 10,000 cubic feet (280 cubic ters). The concentrations that be present in the workroom harm to health are different fon ent substances. 19. A person with normal \ sight can detect dust particles as as 50 microns in diameter. Sm; air-borne particles can be detecti individually by the naked eye on! when strong light is reflected from them. Dust of respirable size (belo1 10 microns) cannot be seen with' the aid of a microscope. 20. Most industrial dusts coi of particles that vary widely in with the small particles greatly oi numbering the large ones. Coi quently, with few exceptions, dust is noticeable in the air aroi an operation, probably more in1 sible dust particles than visible, are present. Separation in air-bome dust 21. Dust in the air may or not have the same composition its parent material. The determininj factors are the particle size an density of each component in tbeg original mixture, and the hardness of the materials (hard materials will resist the pulverizing action of a mechanical device.) 22. For example, foundry mold ing sand contains a large percentage of free silica (quartz) with a lower percentage of clays. Most of the clays consist of fine particles that can be air-borne, but most of the quartz particles are too large to be air borne. The air-borne dust, there fore, as compared with the "original mixture, may contain a much higher percentage of clays and a much 90 Notional Safety News, June 1963 3 lower pi 23. I attract* rate thi their si croscop more si cause o ty and fluencet Miners crons v The est dusts ir TA Size in < 24. borne i cause c cles in will rei room a of time moreor fromjl the lar ther_d greater tides it Inha 25. fibrous particle 5 micri or inm though micron occasic particl' passag branch toratec tive tre 26. tain tc upper can be in the Natione .ftrUm ft. [? lower percentage of free silica. 23. Dust particles are, of course, attracted by gravity. Their settling rate through still air will vary with their size, density, and shape. Mi- scopically small particles settle out more slowly than larger particles be cause of their relatively minor densi ty and because of their being in fluenced by Brownian movement. Mineral particles larger than 10 mi crons will settle out relatively fast. The estimated settling rates for silica dusts in still air are given in Table I. TABLE 1. SETTLING RATES FOR SILICA DUSTS Size in Microns 0.25 0.50 1.00 2.00 5.00 Time to Fall T Foot (minutes) 590.0 187.0 54.0 14.5 2.5 24. Most of the particles in airu me industrial dusts are small. Be- ae of air currents, the fine parti cles in dust clouds at an operation will remain suspended in the work room air for relatively long periods of time. The smaller dust particles, moreover, will travel farther away from their point of origin than will the larger particles so that the far ther dust is from its source, the greater the percentage of small par ticles it contains. Inhalation of Dusts, Fumes, and Mists 25. With the exception of such fibrous materials as asbestos, dust particles must usually be smaller than 5 microns in order to enter the alveoli or inner recesses of the lungs. Al though a few particles up to 10 microns in size may enter the lungs occasionally, nearly all the larger particles are trapped in the nasal passages, throat, larynx, trachea, and bronchi, from which they are expec torated or swallowed into the diges tive tract. `6. When larger particles of cer...,i toxic dusts are trapped in the upper respiratory passages, they can be absorbed by the body fluids in the nasa! passages and in the digestive tract before they are elimi nated. Hence the final toxic effects of larger dust particles may be de layed. The larger particles of irri tant dusts can cause immediate effects in the upper respiratory system. 27. Ragweed pollen, which var ies from 18 to 25 microns in diameter can cause hay fever from its action in the upper respiratory system. This type of dust and other allergenic types, as well as bacterial and irritant dusts, can cause difficulty even in the larger air-borne sizes. 28. When dust-laden air is in haled, some of the larger particles are trapped by the hairs in the nose. Other dust particles are removed from the air as it passes over the moist mucous membranes of the nose, throat, and other portions of the upper respiratory system 29. The bronchi and other re spiratory passages are covered with a large number of tiny, hairlike cilia or microscopic whiplashes, which aid in the removal of dust trapped on these moist surfaces. The cilia, all bending in one direction, make a fast stroke toward the mouth and a slower return stroke. This action tends to push mucous and deposited dust upward to the mouth so that the particles can be ex pectorated or swallowed. Retention of dust 30. Many studies have been made in an effort to determine the amount of dust that is retained-in the lungs, but there is no simple answer to this question. It has been shown that the size of the dust particles, the rate of respiration, the density of the dust in the air, the efficiency of the dust-catching mechanism, and probably many other factors are in volved. Sizes of particles inhaled 31. Although an occasional dust particle of larger size will enter the lungs, particles less than 3 microns in diameter are the most likely to do so and thus have the greatest oppor tunity to cause a physiological re action. In silicotic lungs, for example, dust particles under 3 microns greatly outnumber larger ones, and many particles are less than 1 micron. 32. In the case of very fine fibrous asbestos dust, an exception occurs in the size of particles in haled. Many fibers up to 100 microns long have been found m the lungs Figure 2. Metal volatilized by the boat of weld ing later condenses to' form a fume. On this bendi'weJdlng installation, fumes one removed at their point af origin by o properly located loco! exhaust installation. (Courtesy American Foundrymen's Society) of asbestos workers at autopsy. A typical fibrosis caused by asbestos is produced by fibers ranging from 20 to 50 microns in length, but only a few microns wide. Physiological affects \. 33. The physiological reactions caused by the inhalation of air borne particulate matter will vary with different types of dusts, fumes, and mists. The reactions include: a. The cardiopulmonary reaction which consists of the pneumoco nioses, such as silicosis and asbestosis. In certain cases, specific types of lung pathology result, and the heart may be affected (cor pul monale) when the fibrosis is ad vanced. In other cases, there is mainly just an accumulation of a relatively inert dust in the lungs. b. The systemic reactions which are caused by toxic dusts of such ele ments as lead, manganese, cad mium, and mercury, by their com pounds, and by certain organic compounds. c. Metal fume fever which results from the inhalation of finely divid ed and freshly generated fume of zinc or possibly of magnesium or of their oxides. This is a transient condition d. Allergic and sensitization reactions which may be caused by inhala tion of, or skin contact with, such materials as organic dusts from flour, grains, and some woods and dusts of a few organic and inor ganic chemicals. e. Bacterial and -fungus infections which occur from inhalation of dusts containing active organisms, such as wool or fur dust contain- National Safety News, June 1963 91 Substance Chalcedony Chert Cmtobalite Flint Jasper Quartz Tridyimte Tripoli (Rotfenstone) TABLE II. SELECTED INDUSTRIAL MINERAL DUSTS Description and Uses CRYSTALLINE FREE SILICA (St02, including microcrystalline forms) A heat-resistant, chemically inert form of microcrystalline quartz. A decorative material. Rare in industry. A microcrystalline form of silica. An impure form of flint used in abrasives. A crystalline form of free silica, extremely hard and inert chemically; very resistant to heat. Quartz in refractory brides and amorphous silica in diatomaceous earth are altered to cristobalite when exposed to high temperatures (cab cined). Cristobalite is extensively used in precision casting by the hot wax process, dental laboratory work, and certain specialty ceramics. A microcrystalline form of native quartz, more opaque and granular than chalcedony. Used as an abrasive and in ceramics. A mieroerystalline impure form of silica similar to chert. Used for decorative purposes. Rare in industry. Vitreous, hard chemically resistant free silica, the most common form in nature. The main constituent in sandstone, igneous rocks, and common sands. Vitreous, colorless form of free silica. Formed when quartz is heated to 870 C 0,598 F>. A porous, siliceous rode, resulting from the decomposition of chert or siliceous limestone. Used as a base in soap and scouring powders, in metal polishing, as a filtering agent, and in wood and paint fillers. A cryptocrystalline form of free silica. ihrwhold Litnft in Million Partidej j per Cubic Fool of Ah'- Calculate from formula;*' 250 4 Si02 + 5 sv 1 Dkrtomaceous earth i Silica gel Asbestos Clays Feldspar AMORPHOUS FREE SIUCA (NoncrystaJIine) .- A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic plants. Used in fdtration and decolorization of liquids, insulation, filler in dynamite, wax, textiles, plastia, paint, and rubber. Calcined ond fiux-caleined diatomaceous earth contains appreciable amounts of cristobalite, and dust levels should be the same as for cristobalite. A- regenerative absorbent consisting of the amorphous silica manufactured by the action of HCI on sodium silicate. Hard, glossy, quartz-like in appearance. Used in dehydrating and in drying and as a catalyst carrier. Amorphorus = 20 mppcf Calcined = use formula; 250 % sio2 + 5 -a 20 mppcf 3 SILICATES (Compounds made up of silicon, oxygen, and one or more metals with or without hydrogen. These dusts cause nonspecific dust reactions, but generally do not interfere with pulmonary function or result in disability 1 i ' A hydrated magnesium silicate in fibrous form. The fibers are believed to be the more hazardous component of asbestos dust. A great variety of aluminum--silicate bearing rocks, plastic when wet, herd when dry. Used in pottery, stoneware, tile, bricks, cements, fillers, and abra sives. Kaolin is one type of clay. Some clay deposits may include appreciable quartz. Commercial grades of days may contain up to 20 per cent quartz. Mast abundant group of materials, composed of silicates of aluminum with sodium, potassium, caldum, and rarely barium. Most economically important mineral. Used for ceramics, glass, abrasive wheels, cements, insulation, and fertilizer. 5 mppcf+ 50 mppeff 50 mppeft These threshold limit values were adopted by the American Conference of Governmental Industrial Hygienists in 1962 Threshold limit values obtained from formula apply to all the substances in "Crystalline Free Silica" group tThreshold limits given for substances in "Silicates" group are for compounds containing less than 1 per cent crystalline silica. For compounds containing more than 1 per cent silica, calculate threshold limit from formula: 250 SlO. *f- 5 92 National Safety News, June 1963 -j Fuller's Portion triii compo tng or fun f. Irri wh oth dus dus nas g. Da ma tivi its oth ion 34. three "dust The mean lung.' deten injury arc c eases are cl cause ditior 35 dust mech space to ca Natior ! TABLE II. SELECTED INDUSTRIAL MINERAL DUSTS (Continued) SILICATES (Compounds made up of silicon, oxygen, and one or more metals with or without hydrogen. These dusts cause nonspecific dust reactions, but generally do not Interfere with pulmonary function or result In disability.) Fuller's earth Kaolin Mica Portland cement Silicon carbide (Carborundum) Talc Vermicvlite A hydrated silica--alumina compound, associated with feme oxide. Used as a filter medium and as a catalyst and catalyst carrier and in cosmetics and insecticides. A type of day composed of mixed silicates and used for refractories, ceramics, tile, and stoneware. A large group of silicates of varying composition, but similar in physical proper* ties. All have excellent cleavage and can be spirt into very thin sheets. Used in electrical insulation. Fine powder containing compounds of lime, alumina, silica, and Iron oxide. Used as construction material. Bluish-black, very hard crystals. Used as abrasive and refractory material. 50 mppeft 50 mppeft 20 mppeft 50 mppeft 50 mppeft A hydrous magnesium silicate used in ceramics, cosmetics, paint, and phar maceuticals, and as a tiller in soap, putty, and plaster. An expanded mica (hydrated magnesium-aluminum-iron silicate). Used in light weight aggregates, insulation, fertilizer, and soil conditioners, as a filler in rubber and paints, and as a catalyst carrier. 20 mppeft 50 mppeft [Threshold limits given for substances m "Silicates" group are for compounds containing less than 1 per cent crystalline silica. Tor compounds containing more than 1 per cent silica, calculate threshold limit from formula- 250 % StO- + 5 i ing anthrax spores or wood bark may be essentially inert and remain 38. Definition. Silicosis has been or gram dust containing parasitic in the lungs indefinitely with no defined as "a disease due to breath fungi. recognizable irritation, and a few ing air containing silica (SiO) 1 f. Irritation of the nose and throat, which is caused by acid, alkali, or like limestone dust may be gradually dissolved and eliminated without characterized anatomically by gener alized fibrotic changes and the de other irritating dusts or mists. Some dusts such as soluble chromate dusts may cause ulceration of the nasal passages or even lung cancer, g Damage to internal tissues, which may result from inhaled radioac tive materials such as radium and harm. Silicosis 36. The most important lung dis ease caused by the inhalation of mineral dust is silicosis--well-known velopment of miliary nodulation in both lungs, and clinically by short ness of breath, decreased chest ex pansion, lessened capacity for work, absence of fever, increased suscep tibility to tuberculosis (some or all its daughter products and from in industries where crystalline free of which symptoms may be present), other radioisojopes that emit highly silica dust is present, such as foun and by characteristic X-ray find ionizing radiation. Pneumoconioses dries, glass manufacturing, granite cutting, mining, and tunneling in quartz rock. It is found throughout ings."* 39. Factors of influence. Sili cosis has been known to manifest 34. Pneumoconiosis comes from the world, and in the past it has had itself after widely differing periods three Greek words that mean "lung," "dust," and "abnormal condition." The present generally accepted meaning of the word is merely "dusty lung." The kind of dust inhaled many names, such miner's asth ma, grinder's consumption, miner's phthisis, potter's rot, and stone mason's disease. The same occupa tional disease, however, is meant by of exposure to silica dust Appar ently, development of the disease depends upon: a. The amount and kind of dust in haled. determines the type of condition or all these names, and it is caused by b. The percentage of free silica con injury. A number of organic dusts dust from crystalline free silica, us tained in the dust. are capable of producting lung dis ually quartz (see Table II). c. The form of the silica. eases, but not all these diseases are classified as pneumoconioses be cause they are not all a "dusty con 37. Although considerable prog ress has been made in dust control in industry, men still develop sili d The size of the particles inhaled, e. The duration of the exposure. --Continued on page 95 dition" of the lung. 35 In very rare cases, enough oust had been inhaled to cause mechanical blockage of the air spaces. Flour dust has been known to cause this condition. Some dusts cosis in plants and on jobs where dust control is not adequate. Engi neering control is still the basic means of preventing this disease, and dust control equipment and proce dures must be carefully maintained. "Report (Joint) of the Committee on Pneumoconiosis and the Committee on Standard Practices' in Compensation of Occupational Diseases." Year Book, 1933, American Public Health Association. 1790 Broadway, New York 19. p 100. National Safety News, June 1963 93 docs ~ bn (TtatCT edges --- ttXJCfli and ii 41 fibros ' the 1 panic slight 3 cal i t How one of the world's most important insurance companies chose this symbol...and why Sure, Wausau has landmarks more impressive than this depot. And as fortrademarks. Employers Mutuals' handsome office in Wausau would be a far better reflection of our coast to coast operations and our $325 million assets. But there's another dimension to Employers Mutuals of Wausau. And when we set out to define it and describe it, we find the depot does it best. Back in 1874, the first train puffed its way through the Wisconsin timberlands, summoned north to Wausau by the thriving lumber in dustry. From then on, the depot stood as proof that this community was no longer the "faraway place," as the early Chippewas had de 94 scribed it in givingWausau its name. This Wisconsin community is an integral part of the operating phi losophy of Employers Mutuals of Wausau, just as it hasbeen through out the 52 years since this mutual insurance company was founded. Call this neighborly concern or "Main Street" friendliness and co operation. It's a way of doing busi ness our policyholders seem to like and we don't want to lose. Employers Mutuals of Wausau is a large company now, but the Wausau Way is evident in our rela tionship with policyholders every where. We do business in all the principal cities ofthe nation through 145 offices. We axe one of the largest and most experienced underwriters CIROE OH READER CARD in the field of workmen's compensa-J tion. We write group health and accident, fidelity bonds, and all forms of fire and casualty insurance, including automobile. Wewriteonly nonassessable policies. We're proud ofour unbroken record of dividendsavings. And, as a mutual company, we're dedicated to the prevention of loss. "Good people to do business with" Employers Mutuals of Wausau 42 eralh stage soph timestage ease, the i dowi 4: ease affec as v divi< is v only a ch expc 4tion but brea is n may 4 afte indi post proj er \ Bre !ab< mal Hoti The powers of resistance of the individual concerned. ' g. The presence or absence of a com plicating process such as infection. 40. Many theories have been adweed over the years to explain why crystalline free silica acts as it does in the lungs. Theories have been based on the hardness of the material and the effect of sharp edges, solubility phenomena, elec trochemical action of the crystals, and immunological reactions. 41. It is believed now that the fibrosis produced is caused not by the hardness or sharpness of the particles, but by a combination of slight solubility with a physiochemical effect and an immunological effect--but no one is certain of the exact mechanism of the disease. Ex perimental work on the reasons for the development of silicosis is still going on in various parts of the world. If the precise mechanism of silicosis could be determined, better medical preventive measures might be developed and possibly a cure could be found. 42. Three stages. Silicosis is gen erally classified in three separate 'ages by medical authorities. More ^phisticated classifications are some times used for the various X-ray stages and complications of the dis ease, but for a basic understanding the three stages give a good break down. 43. The first stage of the dis ease - produces no disability. The affected man can cany on his work as well-as ever. Frequently, the in dividual is not aware that anything is wrong, and the disease is revealed only by opaque nodular shadows on a chest X-ray coupled with a known exposure to crystalline free silica. 44. In the second stage, respira tion may be affected in some persons but not m all by any means. Labored breathing on heavy exertion usually is noted first, and a dry cough also may be present. 45. The third stage can develop after the second stage even though the individual has been removed from ex posure to silica dust. However, the 'ogress of the disease will be slow. without continued dust exposure. Breathing may become severely labored. The worker is far below nor mal physically and is susceptible to respiratory diseases. Chest X-rays may show an enlarged heart as a re sult of the body's attempts to overcome the resistance of restricted blood vessels in the lungs. Pulmonary tuberculosis is a frequent complica tion and occasionally results in death. 46. Detection and development. Silicosis may be detected by chest X-rays in each of the three stages However, X-rays alone are not sufficient for a positive diagnosis, for the shadows may be due to a variety of other conditions, includ ing infection or another type of pneumoconiosis. The individual must have had a definite exposure to free silica, because only it can cause sil icosis. The complete occupational and medical history of the employee must therefore be evaluated before a conclusion can be reached. The cor relation of chest X-ray findings and physical disability may be poor in many cases. 47. From most industrial expe rience, silicosis seldom develops in less than five years and in many cases may take 20 years or longer to become disabling. 1 48. The development of silicosis in its earliest stage is not perceived by the individual. The disease cannot be cured by any means yet known. Tuberculosis is more prevalent in persons with silicosis, but the inci dence is decreasing, as it is in the general population. 49. Men with early signs of sili cosis are able to perform their duties and are not a menace to other em ployees, for it is not a contagious disease. A perceptible X-ray change is not grounds for assuming disability because most people show chest changes with advance in age even without exposure to dust. Where there is a known exposure to silica dust, however, men with early signs of silicosis should be seen periodi cally by a physician. 50. Action of silica on the lungs. At the points in the lung where silica dust is deposited and accumu lated, a fibrous tissue develops and grows around the particles. This fibrous tissue is tough like scar tissue. It is not as elastic as normal lung tissue, does not permit the ready passage of oxygen and carbon diox ide, and as it proliferates, cuts down the amount of normal lung tissue. As a result, the available functional volume of the lung is reduced. 51. In some advanced cases, the fibrous tissue will slow down or even prevent the diffusion of oxy gen from the lung to the blood in the capillaries, and the blood in the area will not be completely oxy genated. The fibrous tissue can also affect the blood vessels by oblitera ting them or cutting down the flow of blood. All these effects tend to limit the rate at which oxygen is supplied to the body tissues. Emphy sema is the most obvious symptom. 52. As the inhalation of silica continues over the years, the amount of fibrous tissue will, of course, in crease, with the ultimate result that the lungs will not readily oxygenate sufficient blood for the body's needs. Then when the oxygen demand of the body is increased by exertion, the individual will feel distress with shortness of breath. 53. Amorphous free silica differs from crystalline free silica in physical structure and in physiological effects. In the amorphous state, molecules of silica exist in random. orientation, which may be caused by natural forc es to form opal and diatomaceous earth (kieselguhr). Amorphous silica may be converted by artificial proc esses into such forms as silica gel, silica fume, and fused silica or quartz. 54. If amorphous silica is heated' to a high temperature, as in calcining, forms of crystalline free silica called cristobalite and tridymite result: " These intermediate forms of amor phous silica are known as cryptocrystalline (ultra-raicrocrystalline.) Inhalation of these crystalline forms can readily cause diatomite pneu moconiosis. 55. When diatomaceous earth is calcined, particularly in the pres ence of a trace of alkaline flux, appreciable quantities are converted to cnstobalite. As a result of studies made by the U. S. Public Health Service, it has been recommended that the threshold limit value for crude or amorphous diatomite be placed at 20 mppcf (see Table II), but that the atmospheric concentra tion for dust containing cristobalite be kept under 5 mppcf. 56. Various commercial products containing particles of silica under 1 micron in size are available. The Notional Safety News, June 1963 95 physiological effects of these prod ucts have not been well defined. Until more experience with human beings is available, it is believed these products should be handled with care. 57. Free silica and silicates. Free silica is uncombined silicon dioxide (SiOo). Silicates contain silicon and oxygen combined with other ele ments in a more complex molecule. Analyses of minerals, particularly in geological reports, are sometimes re ported as percentages of oxides, which may include SiOa, AL.O.,, KoO, Fc;,0.t. The SiO-. reported in such chemical analyses is the total of the silicon dioxide present, both the free silica (if present), and the silica combined in the mineral. Such analyses are not reliable indications of the silicosis potential of the material. 58. It is uncombined or free silica that is most important in industrial dust exposure. So that an exposure can be properly evaluated, the per centage of uncombined silica must be determined by petrographic analysis using a polarizing microscope or, preferably, by X-ray diffraction analyses and special analytical chemical procedures. 59. There has been some expenmental evidence that some dusts may tend to inhibit the action of silica on the body, but this inhibiting action is so slight and uncertain that it must be discounted m practice. In fact, there also is evidence that the nonsiliceous components of a dust mixture containing Free silica may provoke a disabling condition more severe than that caused by the silica acting alone. 60. With the exception of asbes tos and some talcs, the silicate dusts do not ordinarily cause a serious disabling lung condition such as is produced by free silica Much higher levels of silicate dusts than of free silica dust can be tolerated. 61. In many industries, men have worked with silicate dusts that con tained no free silica without devel opment of disability or of nodulation in the lungs. The X-ray may show shadows indicating dust deposits in the lungs, but the pneumoconiosis is essentially harmless. However, par tially disabling pneumoconioses have been reported where men have worked for long periods of time in very high concentrations of certain silicate dusts. 62. Disabling pneumoconioses from exposure to abnormally high concentrations of mica, tremolite talc, and kaolin dusts have been de scribed in the literature. The clinical signs are not the same For these sili cate dusts as for free silica, but the symptoms can be marked. 63. The body does not have ade quate defense against indiscrimi nate amounts of dust of any kind. Therefore, although specific symp toms have not been described for many mineral dusts, the general ex perience would indicate that dust levels should be kept within thresh old limit values or below (Table II). Asbestosis 64. Asbestos is a general term ap plied to several minerals having a fibrous character. These asbestos minerals are hydrated silicates of magnesium with variable amounts of iron, calcium, sodium, potassium, and aluminum present as impurities. 65. Asbestos when inhaled produoes fibrous tissue m the lungs of both men and animals. It has been shown that fibers of asbestos must be present for the production of asbestosis. Other silicate minerals of the same chemical composition but nonfibrous in form produce no re action or a relatively mild reaction, but not the severe reaction of fibrous asbestos dust. 66. These facts lead to the con clusion that asbestosis is mainly the result of physical irritation of the lung tisssue and not of a chemical action, which is thought to be one of the causes of silicosis. It is suspected that lung cancer may be induced by asbestos. However, there is no im pressive amount of evidence to sup port this assumption. 67. The fine air-borne fibers of asbestos can pass through the upper respiratory tract to the lower parts of the lungs to cause irritation and to form "asbestos bodies" where the fibers are encapsulated. This diffuse fibrosis probably begins as a "collar" about the terminal bronchioles. There is evidence that other min erals having a fibrous character can produce a reaction similar to that of asbestos. Fiber glass, however, does not produce such a reaction. 68 Following a study by the U S. Public Health Service of the asbestos textile industry * recommended that the dust gunccf, tration be kept at less thm 5 tnoZ to prevent asbestosis. Evaluation ^ an exposure to abestos dust is baw on the total amount of dust because it has proved out m practice that if the fine dust is kept below the suggested threshold limit, the concen tration of injurious fibers will also be kept within safe limits Toicasis 69. As used in industry. "talc~ is a very general term. To the geolo gist, talc is a hydrous magnesium silj. cate, which may be a relatively purc mineral or may be mixed wnh tremolite or with dolomite depending upon where it is mined. The term "talc" is ^ applied commercially to carbonate^ mixtures that have the same ge: feel and physical properties; it is applied to pyrophyHite, a hydrous^ aluminum silicate, which frequently is mixed with a high percentage of ~ quartz. The free silica generally found with pyrophyllite can cause silicosis It is therefore essential to know which talc is being used in order to evaluate a specific dust ex posure. 70. Talcosis is usually associ- . ated with tremolite talc. This disease produces changes in the lungs and"' symptoms similar to those of as- bestosis. Anthracosilicosis -m 71. Anthracosilicosis, a compfex^H form of pneumoconiosis, is a chronicS disease caused by breathing air co53g taming dust that has free silica Wrg: one of its components and that generated in the various processes - involved in mining and preparing -- anthracite (hard coal)** and, to lesser degree, bituminous coal. __,i_ 72. The disease is characterized anatomically by generalized fibrotic changes throughout both lungs and by the presence of excessive amounts *Dreesen, W. C-, Dalla Valle. J. Mdwards. T I.. Miller. J. W. and Sayers. I, R, A Study of Asbestosis m the Asiestos Textile Industry, 0. S Pubhc iealth Bulletin No. 241, V. S. Public iealth Service. Washington 25, D- C- **Anthracosilicosis among Hard-Cod Miners V S. Public Health Bulletin No221. U. S. Public Health Service. Wasnington 25, D C-. 1935. 96 National Safety News, June 1963 Jfz i ( I / f C F c r* tl c. tl ot d> e? cc ai Pr be wl W ch lui oc< we as of hai Wl of per erei exp ver* non end* witf exp< Nafic of carbonaceous and siliceous ma terial Such lungs on autopsy are coal black. 71. Symptoms found in early st ' of the disease are shortness of oreath, cough with a coal-black sputum, pain in the chest, and in some cases physical weakness. In the advanced stages, there are loss of weight and decreased capacity for work, partly caused by pulmonary infection (frequently bronchitis), and in some cases there may be heart failure. 74. Experiments with animals showed that mixtures of coal and quartz produced more fibrosis than did quartz alone. The harmful effects of coal dust do not come only from the silica in the dust. Coal dust alone in very heavy concentrations over a period of many years can cause breathlessness and ventila tory impairment. Miscellaneous pneumoconioses 75. Even though a dust is classi fied as harmless, excessive amounts of it can lead to trouble by causing ^ pneumoconiosis or simply by mech-'uically irritating the walls of the r atory system. Moreover, even though there is no chemical or physi cal irritation, mechanical plugging of the lungs and interference with their ordinary processes can result. Mica dust and kaolin dust are two good examples of dusts that ordinarily are considered benign but in excessive amounts can cause a troublesome pneumoconiosis. 76. Mica pneumoconiosis has been observed in grinding operations where mica dust, but no free silica was present. There were marked changes in the X-ray pictures of the lungs and some disability. The cases occurred where the dust exposures were massive over many years. 77. Kuohnosis has been described as a condition induced by inhalation of dust released in the grinding and handling of kaolin (china clay). Where the cases occurred, dust levels of several hundred million particles per cubic foot of air were common. 78. Aluminum dust is not consid ered to be harmful except where sures are massive. Without adVv-ae effects, aluminum dust inhala tion has been used as part of an endeavor to prevent silicosis. Also without adverse effects, extensive exposures to aluminum dust have oc curred in the grinding of aluminum parts and castings. It can therefore be concluded that reasonably good control will prevent harm from alu minum dust. 79 Bauxite pneumoconiosis (Sha ver's disease) has been found only in workers exposed to fumes contain ing aluminum oxide and minute or ultramicroscopic silica particles aris ing from smelting bauxite in the manufacture of corundum, an im pure form of aluminum oxide. It is essentially a diffuse interstitial fi brosis and marked associated em physema, with a complete absence of any nodular fibrosis. It definitely does not occur from the use of cor undum grinding wheels or from other forms of aluminum oxide. 80. Some pneumoconioses may show marked shadows on an X-ray film; these shadows, without the nec essary information on the exposure of the individual, may be alarming in a general X-ray screening pro gram. On clinical examination of in dividuals showing the X-ray mark ings, however, often no disability or symptom can be found. 81 These shadows are frequently encountered when the dusts contain atoms of relatively high molecular weight because the heavier atoms are fairly opaque to X-rays. Insoluble barium dusts and tin oxide dusts, for example, can show very marked shadows on X-ray films without pro ducing signs of significant pathology (barium dust that is soluble in the body fluids can give a toxic reaction). 82. Iron oxide, particularly ex cessive fume from welding opera tions, may produce siderosis with a pigmentation of the lungs (black in welders and red in iron ore miners) without disability. The X-ray shad ows produced by the iron oxide in tne lungs are somewhat similar to the shadows from silicosis. Because of this similarity, differential diagnosis is often difficult, and heavy exposures to iron oxide dust and fume may lead to medicolegal problems. It is there fore important to control iron oxide exposures even though siderosis is not disabling. 83. Limestone, marble, lime, gyp sum, and portland cement dusts ap parently have no serious effect even after long exposures. Also, many sili cates and other minerals have not caused impairment in individuals in haling the dusts, and the resulting pneumoconioses are generally classed as benign. Toxic Dusts and Fumes 84. Systemic reactions are caused by toxic dusts and fumes of various elements and their compounds and by certain organic compounds. AH metallic fumes are irritating, especi ally when freshly generated. Indus trially important metals and their compounds that can have a toxic effect when the dust or fume is in haled include arsenic* antimony, cad mium, chromium, lead, manganese, mercury, selenium, tellurium, thall ium, uranium, and a few others.* 85. The effect of some metals, such as magnesium and zinc, appears to be transient. Only limited data are available on the exotic and rare earth metals. 86 Although the dusts and fumes from metals with low toxicity do not need as much attention as the dusts and fumes from highly toxic metals, they should not be neglected of disregarded. The metals with low toxicity are controlled more readily because greater amounts can be tol erated, but their dusts and fumes should be kept at reasonable levels since excessive amounts of any of them can be harmful (Table III). Lead poisoning 87. Although extremely severe cases of lead poisoning are rare in industry today, lead exposures must be controlled to prevent even the moderate symptoms, which can be troublesome. Inhalation of the dust of lead compounds is the most com mon mode of entry of lead into the system. Ingestion of lead compounds can add to the problem if personal hygiene is poor Workers should therefore be encouraged to wash thoroughly before eating, and lunch rooms should be segregated from work areas. 88. It should be recognized that lead is a normal constituent of plants 3nd animals. People ingest and ex crete lead daily even though they are not exposed to lead in their daily work. The body can handle *See the following National Safety Council Data Sheets Antimony and Its Compounds, 408; Arsenic and Its Inor ganic Compounds, 499, Cadmium, 312; Lead, 443, Magnesium, 426, Manganese, 306; Mercury, 203, Titanium, 485; Zinc and Zinc Oxide, 267; Zirconium Powder, 382. National Safety News, June 1963 97 and eliminate small amounts without harm. When intake rates exceed the normal excretion level, build-up oc curs in the body. There is a safe level of absorption, and if the conf 'ntration of lead dust in the air -i work areas is kept below the threshold limit, there should be no difficulty. 89. The importance of maintain ing the concentration of air-borne lead at a very low value stems from lead's high toxicity and its tendency, in small amounts, to accumulate in the human system. When lead ab sorption in the body reaches a suf ficient degree, symptoms of poison ing or intoxication appear. Beryllium intoxication 90. Beryllium intoxication is a severe systemic disease that can re sult from the inhalation of massive doses of dust of metallic beryllium, beryllium oxide, and some soluble beryllium compounds. There are two forms of the disease. One is an acute form of chemical pneumonitis with cough, pain, difficulty in breathing, cyanosis, and loss of weight. In the chronic type, lenown as berylliosis, there may be loss of appetite and tight, weakness, cough, extreme fficulty in breathing, cyanosis, and cardiac failure. Mortality is high in' chronic beryllium intoxication, and many who survive suffer from pul monary distress. ' 91. Individual susceptibility ap parently is an important factor in the development of the disease. In many instances, one employee has devel oped the severe symptoms while oth er employees-doing the same work have shown no signs of disability. 92. Beryllium intoxication has never been demonstrated in individ uals mining or handling ore only. There is no evidence of intoxication from the ingestion of beryllium oxide, beryllium metal, or any of the beryl lium alloys. Only the inhalation of beryllium dust produces systemic disease. 93. Because of the severe nature of the disease and because there is no way of predicting who will de velop it, extreme care must be taken to control the dust and fume that se in the handling of beryllium, alloys, and its compounds. Beryl lium is toxic in such small quantity as to be considered the most toxic of all elements yet investigated. TA8LE III. SELECTED TOXIC DUSTS AND FUMES Substance Antimony Arsenic Barium (soluble compounds) Beryllium Chromic acid and Chromates Cyanide (os CN) Dinitrobenzene Fluorides Hydroquinone Iron oxide fume Lead Lead arsenate Magnesium oxide fume Description and Effects Threshold in Milligrams Cubic Meter of Air1 Gray metal often associated with lead and arsenic. Ha-ardous from inhala tion and ingestion. Soluble salts may cause dermatitis. 03 Silvery brittle crystalline metal. Haz ardous from Inhalation and ingestion. Usually encountered as arsenic tri oxide. 03 Soluble barium chloride and sulfide are toxic when taken by mouth. 03 Light weight, gray metal. The metal, low-fired oxides, soluble salts, and some alloys are toxic by inhalation. 0.002 Red, brown, or blade crystals. Caustic action an mucous membranes Or skin. 0.1 Nonvolatile cyanides are ingestion haz ards. Cyanides inhibit tissue oxidation upon inhalation and cause death. 5.0 (skin**) Yellowish crystal. Hazardous from skin absorption, inhalation, and ingestion. 1.0 (skin**) Inorganic fluorides are highly irntanl and toxic. 23 Colorless hexagonal crystals Contact with the skin may cause sensitization and irritation. Excessive exposure to dust may cause corneal injury. 2.0 Major sources are cutting and welding. 15.0 lead fumes and lead compounds cause poisoning after prolonged exposure. Most important means of entry into body is inhalation. Skin absorption is of significance o'hly from such organic compounds as lead tetraethyl. 0.2 White crystals--highly toxic. 0.15 White powder. Inhalation of freshly generated fume may cause metal fume fever. T5.0 Titanium Trinitroto Uranium Vanadiur Zinc oxid fume Zlrconiuir compo These threshold limit values were adopted by the American Conference of Govern-^ mental Industrial Hygienists in 1962. The mental I The contribut 94. When the soluble salts of beryllium, especially beryllium fluo ride, come in contact with cuts or abrasions on the skin, deep ulcers may be formed that heal very slowly. Complete surgical excision of the ul cer is sometimes required in order to effect healing. Metal fume fever 95. Metal fume fever is an acute condition of short duration caused by a brief high exposure to the freshly generated fumes of metals such as tine or magnesium or their jH oxides. Symptoms appear from four S to twelve hours after exposure and M consist of fever and shaking chills. j* There is complete recovery usually ^ within one day, and ordinarily the || employee can return to the same job % without recurrence. However, after M a period in which there has been no 'S contact with the fume, for example, a j, js lively 95 1 heavy c requirec mOSt c caused from mr 0th been re 0CCl 0}ddes i 96 Notional Safety News, June 1963 National Substance TABLE III. SELECTED TOXIC DUSTS AND FUMES (Continued) Description and Effects Threshold limit in Milligrams per Cubic Meter of Air* Manganese pentochloropheno! Phosphorus (yettow) Picric ocid Selenium compounds Sodium hydroxide Tellurium Titanium dioxide Trinitrotoluene i 1 \im Vanadium pentoxkfe Zinc oxide fume Zirconium compounds Silvery gray metof. Hazardous from inhalation of fumes or dust. SO Dark-colored flakes. Harmful dust. Emits toxic fumes when heated. 0.5 (skin**) Poisonous mainly by Inhalation. Severe burn hazard from skin contact 01 Yellow crystals or liquid. Explosive-* particularly metallic salts. Emits toxic fumes on decomposition. 0 1 (skin**) Toxicity varies somewhat according to the solubility of the specific com pound. Often causes contact dermatitis. White, deliquescent pieces or lumps. Has severe action upon all body tissue. Similar to selenium chemically and in physiological effects. 0.1 2.0 01 White to blade powder. Considered in 15.0 the nuisance category Colorless to yellow monodinic crystals. Emits toxic fumes of oxides of nitrogen when heated to decomposition. Highly poisonous explosive. 1JS (skin**) Highly toxic and a radiation hazard that requires special consideration. 0 05 (soluble com pounds) 0.25 (insoluble com pounds) Yellow fa red crystals. Acts chiefly as an irritant to the conjunctiva and respiratory tract. 0.5 (dust) 0.1 (fume) Amorphous white or yellow powder The powder is essentially nontoxic, but freshly generated fume may cause metal fume fever. 5.0 Most compounds are insoluble and have low toxicity. 50 These threshold limit values were adopted by the American Conference of Govern mental Industrial Hygienists in 1962 The word "skin'* in this table indicates that the substance can penetrate the skin to contribute to the exposure. after a layoff, resumption of exposure ts likely to bring on an attack. 96. To cause metal fume fever, heavy concentrations of fumes are required. Zinc oxide fume is the most common source, but cases caused by the inhalation of fumes f magnesium oxide, copper oxide, ana other metallic oxides have also been reported. The condition does not occur from the handling of these oxides in powder form. Apparently, it results only from the inhalation of extremely fine particles freshly formed as fume (nascent fume). 97 Nickel, mercury, and other metals may also produce a fever fol lowed by the toxic effects of the element. Allergic Reactions 98. When in the form of dust, a large number of materials may cause various allergic reactions in suscep tible individuals. Examples of such agents are certain animal products. Foods, drugs, and chemicals. The bodily systems usually involved m allergic reactions, which may be quite severe, are the skin, respiratory sys tem, and gastrointestinal system. Oc casionally, two or more systems are involved. Some of the allergic reac tions are dermatitis, hay fever, asth ma, and hives. 99. Usually, the victim is subject ed to a series of exposures without any reactions during which sensiti zation is built up. These exposures may occur continuously for years. Then, at the end of the "incubation period," which varies according to the individual, a reaction is pro duced. 100. For a true allergic reac tion two factors arc required a. A history of prior exposure to the material involved (sometimes not known by affected employees), b A "challenge dose" of the mate rial, which provokes the allergic re action. 101. Continuous exposures may act as "desensitizing doses," and under these conditions an allergic individual may work without incident for long periods of time only to find that re-exposure after removal from the sensitizing material (such as after a vacation) causes an allergic re sponse to recur. 102. Medical and engineering rec ommendations to prevent allergic reactions are based on prevention of exposure by means of personal pro tective equipment, ventilation meth ods, or removal of sensitized individ uals from the exposure. Infections Infection and pneumoconiosis 103. The presence of pulmonary disease that significant^ interferes with the natural defenses against foreign particles may increase sus ceptibility to pneumoconiosis. Con versely, a pneumoconiotic lung is more prone to infection. For exam ple, tuberculosis occurs more fre quently among silicotics than among normal persons. Severe disability or death of a silicotic, when caused by pulmonary conditions, usually results from complicating tuberculosis either alone or combined with other infec tions Bacteria and fungi 104. The possibility of lung in- National Safety News, June 1963 99 L'WUJ-JU AJtr fecdons from the inhalation of bac teria and fungi exists in severai in dustries. Pulmonary anthrax from the inhalation of dust containing an 110. Since radioisotopes are se lectively taken up in individual or gans, they may cause only localized irradiation. The radiosensitivity of 116. The currently reco: threshold limits of particular can be found in the most tecem published ACGIH list, or .taut t costs must dons thrax spores has occurred among em the organ dictates the extent of the ACGIH can be consulted 5 pei ployees engaged in the handling of hazard of a particular radioactive Information on threshold limits afcw^ exceei wool and the crushing of bones from substance. Solubility and particle can be obtained from the National'1" foot infected animals size determine how much of the ac Safety Council, state occupatiQnaj dusts 105. Fungi (molds) growing on tive material will gam access to and health agencies, the American Indus- 50 pt grain has been found m the sputum remain m the blood stream and var trial Hygiene Association, and com- exceei of workmen shoveling the gram and ious organs. pensation insurance carriers. more are believed to be the cause of out 111. If radioactive air-borne con 117. No one knows the exact shouli breaks of respiratory disorders. tamination is known to be present, concentration at which men will start ti Fungi found in sugar cane residues (bagasse) are believed to be part control measures are mandatory. If the presence of contamination is un to develop silicosis, asbestosLs, 0r lead poisoning. With some toxic of the cause of bagassosis. Fungal known but suspected, sampling must dusts, however, experience has been below 12: mulat somet spores formed under the bark of be done to determine whether or not wide enough to establish the present ~ cases, some trees have been blamed for air-bome concentrations of the ra threshold limits as fairly reliable. i: respiratory difficulties among em dioisotope are below the threshold 118. For example, if the level of 1! ployees who debark dry logs. limit value. lead in a workroom is kept below; 106. Although the incidence of 112. Good personal hygiene and 0.2 mg/cu m, experience has shown occupationally related bacterial and good operating techniques are much that cases of lead intoxication fungal infections is found to be more important in the handling of not occur. Experience also relatively low, the respiratory effects radioactive materials than in the han shown that many men can to! the li protec vidua) has si stxingi to rai reasor can be troublesome and, in the case dling of most other materials used in lead levels well above 0.2 Toxic of pulmonary anthrax, even fatal. The basic methods of control are the same as those for the pneumoconio sis producing dusts, but sterilization and disinfection must be added. Radioactive Dusts* 107. A radioactive contaminant may offer a chemical toxicity hazard in addition to an ionizing radiation exposure, and it may be present as a gas, dust, fume, or mist. 108. Radioactive contaminants ' taken into the body may be deposited industry. 113. Engineering controls for radioactive dusts arc similar to those for other dusts and depend primarily upon capture at the point of genera tion. The difference lies in the fact that controls for radioactive dusts must be extremely efficient. Thresh old limit values for radioactive par ticulate matter are very low, and in some cases 100 per cent efficiency in capture and retention is required. Permissible Dustiness ' cu m without signs of trouble. \v Mineral dusts 119. In the United States, the threshold limits for mineral dusts are expressed in millions of par ticles per cubic foot of air (mppcf). The concentration of a mineral dust is determined by counting dust par-_ tides that are less than 10 microns in size in an aliquot sample afterifl sampling a known volume of air.c in a known volume of liquid. In ^ some European countries, mineral', dusts are weighed, and permissib^ 12* limits in m air. V levels gestec is ad toxic the sr the w be de unusu of oc from i in various organs where they consti tute sources of internal radiation. The chemical characteristics of the radioactive contaminant or isotope determine the organ in which it will be deposited. The excretion rate is also dependent upon the chemical nature of the isotope, because the radioactive isotopes of an element follow the same metabolic process as do the stable isotopes of that ele ment. 109. If a radioisotope has been deposited in the body, the internal exposure is regarded as continuous until the isotope is lost by radiologi cal or biological decay. In some cases, exposures may last a lifetime. 114. Threshold limit values of mineral dusts and toxic dusts--that is, time-weighted average concentra tions considered permissible for ex posures of eight hours per day, five days per week--have been pub lished by the American Conference of Governmental Industrial Hygien ists. These values have been obtained from the experience of many groups in industry and from laboratory studies on animals. They are re viewed annually and changed as nec essary on the basis of experience 115. These values are set only as guides for the best practice and are not to be considered absolute values. There is reasonable assur levels are expressed as mllli; of dust per cubic meter of air (m; cu m). In England and some othi areas, the number of partides cubic centimeter is the current of measurement. 120. In comparing United States'.2J and foreign dust counts, it is helpful jg to keep in mind that 100 particles^, per cubic centimeter is equivalent to approximately 3 million particles per cubic foot . 121. It is difficult to compare dust counts with results obtained on ^ the basis of weight. However, with = either type of measurement, a thresh- * old limit can be set as an objec- j tive. Experience has shown that -. Nuisc 12! co'nsic not bt of a its le\ praeti the s desira 12f tnppc! limit dusts, tice, t to be low ff fort plant ance that occupational disease will maintaining dust levels below the not occur if exposures are kept be recommended threshold limits has *For a detailed discussion of radio activity and an extensive bibliography, see the chapter entitled "`Ionizing Radia tion" in the At-udent Prevention Manual for Industrial Operations, published by the National Safety Council. low these levels. On the other hand, occupational disease is likely to de velop in some people if the recom mended levels are exceeded consis tently resulted in a great decrease in the incidence of occupational diseases. 122. Threshold limits are based on the percentage of free silica where this substance is the impor- . 12: trollm avails where too National Safety News, June 19^3 Nation taut constituent of the dust. If sili cosis is to be prevented, these limits must not be exceeded. Concentra tions of dusts containing less than 5 per cent free silica should not ;d 50 million particles per cubic (mppcf). Concentrations of dusts containing from 5 per cent to 50 per cent free silica should not exceed 20 mppcf. Dusts containing more than 50 per cent free silica should be kept at concentrations ; below 5 mppcf. I 123. As more experience accu- imulates, original threshold limits sometimes can be modified. In some ! cases, it has been necessary to lower the limits, for the objective is to protect the more susceptible indi viduals. In a few cases, experience has shown that the limits were too stringent, and it has been possible to raise the limits to allow for more reasonable controls. figure 3. Each of these grinding wheals is portiolly endosed by an **hvit hood* Efficient local exhaust is ochieved by drawing the dust into the hoods, through branch ducts, and into a centra) duct which leads to the collection point (Courtesy American Foundrymen's Society) Toxic dusts 124. In all countries, threshold limits for toxic dusts are expressed in milligrams per cubic meter of air. With toxic dusts, the average (levels must be kept below the sug gested threshold limits. Tn fact, it i- advisable to keep the levels of dusts as low as practical in the specific circumstances. Little in the way of experience or data will be developed if the levels are kept unusually low, but few if any cases of occupational disease will occur from these dusts. Nuisance dusts 125. Even though a dust may be considered generally innocuous and not be recognized as the direct cause of a serious pathological condition, its level should be kept as low as is practical. Dust levels well below the suggested threshold limits are desirable. 126. A concentration of 50 mppcf is suggested as the threshold limit for a number of nuisance dusts. With good engineering prac tice, there is no need for this level to be exceeded. Any reduction be low this level will increase the com fort of employees and improve plant housekeeping. Methods of Control 11 Various methods of con trolling dusts, mists, and fumes are available. Basic engineering dictates where possible an operation should be made dustiess through control at the source. This method is always the most effective, for it either com pletely prevents the contaminant from entering the workroom atmos phere or limits to safe levels the amounts that do escape In addi tion, this method is generally the least expensive. 128. When control at the source is not possible, other methods may have to be considered. Any one or a combination of the following types of dust control may be needed to limit the exposure, a. The dusty operation may be en closed, with or without a local exhaust system. An enclosed op eration generating large quantities of dust usually needs to be ex hausted, or the dust will leak into the surrounding atmosphere. Ex amples are sandblast cabinets or sandblast rooms and the dry boxes used to handle radioactive materials, b The dusty work may be performed in a separate building or may be isolated by partitions to reduce the number of employees exposed to the dust. The employees who are still being exposed should be pro tected by respiratory protective equipment. c. A less hazardous material may be substituted. For instance, steel shot may be used instead of silica sand in abrasive cleaning. d. Keeping the materials moist may be a practical means of control. Examples are the careful and prop er wetting down of aisles m a foundry and the use of water m drilling. e. Local exhaust systems may be in stalled with virtually full or partial enclosure. Examples are an ex haust hood on a grinding wheel (Figure 3) and an exhaust hood at a bagging or filling operation. f General room ventilation can be used to dilute the dust by adding large quantities of air and thus preventing build-up of dust con centrations. Examples of this meth od are roof fans and roof moni tor windows. But it generally is inefficient and expensive to attempt to control contaminants by dilu tion. g. The dusty work may be performed at night or on week-ends to reduce the number of employees exposed. Cleaning dust accumulations from overhead beams, for instance, is preferably done during a weekend. The employees who are exposed should wear appropriate type of respiratory protective equipment. h The number of working hours at the particular exposure can be re duced. However, other methods of control are preferable. i. Use of respiratory protective equip ment approved for the exposure by the U S. Bureau of Mines can give excellent protection against all types of dust, but in most cases should be considered as a tem porary control measure In a sandblast room, however, air-supplied helmets usually are required continuously during operations. Respiratory protective equipment. Notional Safety News, June 1963 101 Figure 4, Since this swing-frame grinder t> used in a variety of poiftioru, die local exhaust sys tem most be adjt/sfable. The flexible duet (A) permits movement of the exhaust hood (B) as needed. (Courtesy American foundrymen's So ciety) nevertheless, should not be con sidered as a universal substitute for adequate local exhaust re moval, elimination of the con taminant, or containment. 129. Many states and municipal ities have dust control codes or or dinances with which employers must comply. In a few states, for instance, written approval of plans must be obtained before a local exhaust system is installed. Each employer should therefore know his state and municipal dust control re quirements. 130. Each type of exposure must be considered separately. For ex ample, a local exhaust system suit able for welding or cutting of steel might not be satisfactory for weld ing or cutting steel coated with red lead. ; Local exhaust systems 131. A local exhaust system for the control of an industrial dust or fume traps the air contaminant near its source so that an operator standing at the process is not ex posed to harmful concentrations. The system should be designed to enclose the process as completely as possible. This method usually is preferred to general ventilation, but should be used only when the contaminant cannot be controlled by isolation, process revision, or substitution of less harmful mate rials. Even though a process has been isolated, it may still require a local exhaust system. 132. A local exhaust system con sists of four principal parts- a. Hoods or other inlets, into which the air-borne contaminant is drawn. b. Ducts, to carry the contaminated air to a central point. c. Dust and fume collectors, to clean the air before it is discharged. d. A fan and motor to keep the air moving through the system. 133. While each of these parts should he designed and installed to perform its required function with respect to the system as a whole, design of the exhaust hood demands the greatest care. The degree of control of dust at the point of gen eration or dispersion is determined by the shape of the hood or degree of enclosure, the location of the hood and its distance from the dust source, and the rate of flow of air into the hood. A poorly designed hood can make an exhaust system ineffective. 134. There is no standard hood. In every case, the hood must be designed to fit the specific opera tion and to make the exhaust effec tive without interfering with the operation (Figure 4). Among the factors to be considered are the nat ural air currents in the room and other exhausts or windows in the area. , 135. The hood should be shaped to conform to the shape of the area of dust production so as to secure reasonably uniform air velocity over this area. A hood which does not en close the process should be placed with its opening as close as possible to the point of generation of the dust or fume (Figure 5) because the velocity of the air in the zone of the hood influence is inversely proportional to the square of the distance from the face of the hood. 136. The hood opening, or part of it, should be located so as to re ceive directly dust that is thrown off along a well-designated path (Figure 6). The directional energy of the material can thus be used for its own capture. Air movement must always be past the employee, then over the dust source, and di rectly into the face of the hood. 137. The fan should be of suffi cient capacity to maintain the re quired air capture velocity at the point of generation of the dust. In ternal baffles should be installed to guide the air flow where it is most needed. Flanges should be provided wherever possible to reduce the air flow from areas where no dust is produced; that is, air-flow contours should be controlled. 138. Enough air must be. plied to the room from the outsii replace the air that is remow the exhaust system. Othe: there will be interference with other? exhaust systems in the area or witfi^ gas or oil flames in nearby furnaces/? Great difficulty has occurred where ^ an exhaust system caused a slightly negative pressure in a room con taining a gas furnace. As a resultair came down the furnace flue ~ and the area became contaminated with carbon monoxide from the fur nace. 139. With small exhaust systems, air that is removed usually can be replaced by infiltration flow, butf= larger exhausts may need a positive. -* air supply (Figure 7). An adeqi supply of make-up air, tern] when necessary, is one of the mi frequently overlooked fundamcm of ventilation. Air always should supplied in quantities equal toil slightly in excess of the amoun exhausted. 140. The size of the diiets, type and size of the dust colli and the type and size of the fan and motor (explosion-proof where necessary) are among the other fac tors which must be considered in the^c design of an exhaust system. Prer^ venting ignition of a combustibi L I Figure 5 To achieve the proper exhaust 1 velocity, the hoods for these barrel fumoevs^ can be positioned as dose to the fvmocti os practical. Such positioning is made by mounting the hoods on a trolley syspende^J from an overhead track. (Courtesy Brake Shoe Co.) contan sideral subjec beyorn an exi shoulc 14) secure licatio editioi A Mi lice, Conte trial chapti Syster Acda Indus the N Gene 14 practi tool c syster used It sh when used, job ti 14 the i from tamii level volu syste trol, fonr be c ham tanc sour and 1 supi stall inte ram not cen air gen air plie tha des imf pra air dill w< 102 National Safety Newt, June 19> Hal contaminant is a prime safety con sideration. Since discussion of the subject of exhaust system design is beyond the scope of this data sheet, / experienced ventilation engineer jld be consulted. 141. Also, information can be secured from several excellent pub lications, one of which is the current edition of Industrial Ventilation-- A Manual of Recommended Practice, published by the American Conference of Governmental Indus trial Hygienists. Another is the chapter entitled "Local Exhaust Systems and Ventilation" in the Accident Prevention Manual for Industrial Operations, published by the National Safety Council. General ventilation 142. Where it is impossible, im practical, or too expensive to con trol dust entirely by local exhaust systems, general ventilation must be used as a supplement or a substitute. It should be noted, however, that where local exhaust systems can be used, they will always do a better job than general ventilation. 143. General ventilation requires - introduction of enough clean air n the outside to dilute the con taminated atmosphere to a safe level. This method requires larger volumes of air than local exhaust systems to accomplish the same con trol, and will not be effective uni formly over a large room. It should be considered only when local ex haust systems require such assis tance. This is usually where the sources of dust are widely dispersed and each is small. 144. General room exhaust and supply fans must be carefully in stalled. Eddy currents, which will interfere with local exhaust systems, must be avoided. Employees must not be exposed to excessive con centrations of dust as the dust-laden air moves away from the point of generation, and sufficient makeup air from, the outside must be sup plied to the room to replace the air that is exhausted. The location and design of the source of supply are important. It is becoming common nractice to supply clean, tempered to the work zone for controlled dilution. Wet methods 145. Wet dust is not dispersed as readily as dry dust--advantage of this fact should be taken whenever possible. Carloads of dry minerals in some cases may be wetted down before they are unloaded. Aisles in foundries should be wetted down to prevent dispersal of the dust by traffic. Water sprays can be used at some operations. Wet drilling methods can be used for rock drill ing to wet the dust as it is formed. Personal protective equipment 146. Respirators of various de signs are available which will give protection against toxic and pneu moconiosis-producing dusts by Bi tering out the contaminant from the air. The U. S. Bureau of Mines has set up performance standards for dust respirators and gives approval to respirators that meet these stand ards. It is important that a respirator be used only for the particular dust exposure for which it has been approved. 147. Although approved respira tors will give excellent protection when properly fitted, they should be used only as supplements to other method* of control or for short or occasional exposures and not as primary controls. 148. Proper fitting of a mechani cal filter respirator to the face of the individual is most important because a small space between the facepiece and the face will permit dustladen air to bypass the filter. 149. Respirators must be in spected and cleaned daily. Filters should be replaced before they be come so plugged with dust as to seriously increase resistance to breathing. Proper filters for replace ment should be available. Medical program 150. An effective medical con trol program will help prevent cases of occupational disease. Such a program can also serve as a check on the engineering controls because symptoms of exposure in a group of workers will indicate a failure that must be corrected. The extent of the medical program will depend upon the seriousness of the expo sures. 151. An industrial hygiene pro gram should parallel the medical program. Both are essential to pro tect the health of employees. 152. The physical examination for new employees should include a thorough pre-employment history with the occupational background given in detail. Chest X-rays should be made of all new employees who win be working in dust exposures that could produce disabling pneu moconiosis. The examining physi cian should decide on placement of those who have pneumoconiosis, active or significant past tubercu losis, abnormally low timed vital capacity, or serious pulmonary dis eases. 153. Periodic physical examina tions, including chest X-rays, should be made of employees exposed to toxic dusts, fumes, and mists. Such checks can help find incipient cases of poisoning in which symptoms are slight, and the X-rays can pick up early symptoms of lung condi tions. Suitable preventive measures can then be taken. 154. Routine periodic clinical examinations, stipple cell counts, porphyrin determinations, and propperly evaluated blood and mine lead level measurements, are prac tical methods for checking em ployees exposed to lead. If unsafe exposures are found, further en vironmental control is mandatory. Affected employees should, of course, be given proper medical treatment. 155. Medical controls for em ployees who work with radioactive dusts must be more stringent than the medical controls for most dusts. An extensive bioassay sampling program is nearly always required. Other control measures 156. Although the most effective method of control is to prevent con tamination of workroom air and thus prevent inhalation of harmful Figure 6. The centrifugal farce created by this grinding wheel cause, the generated dust to travel in a well-defined path. To prevent disper sion of the dust, the exhaust hood is placed dfrecHy in the dust stream, dose to ill source.(Courtesy American Foundrymen's Society) National Safety News, June 1963 103 dusts, the importance of personal hygiene should not be overlooked. The periodic medical examinations provide a good opportunity for in struction of employees in various personal hygiene measures. 157. Good washing facilities, clean lunchrooms, and clean work clothes can help prevent additional, even though minor, exposure to toxic materials. Also, contaminated work clothes should not be taken home where a toxic dust could contaminate the home or expose other members of the family. These recommendations become manda tory where such materials as beryl lium and radioisotopes are handled. ACKNOWLEDGMENT The text of this data sheet, which re places Health Practices Pamphlet No. 4, was prepared by the Health Committee of the Chemical Section, National Safety Council. The content has been extensively reviewed by members of the Natippai Safety Council, representatives of chapters of the American Society of Safety Engi neers, medical authorities, and industrial hygienists. The data sheet has been ap proved for publication by the Publications Committee of the Industrial Conference, National Safety Council. f prink Imlustru Oraw-H 42nd St Elkintrial T< -- Wiley a New Yi Figure 7. In thi* foundry, local exhaust hoods are installed over each station having a -L-w . ..`s machine and glue press. Adequate moke-up air is supplied from ventilating duct situated molding machines and presses. (Courtesy Amertcun Foundrymen's Society) ** BIBLIOGRAPHY Accident Prevention Manual for Industrial Operations, National Safety Council, 425 N. Michigan Ave., Chi cago 11. Anthracostlicosis Among Hard-Coal Miners, U. S. Public Health Bulletin No. 221, U. S. Public Health Service, Washington 25, D. C. 1935. Brandt, A. D., Industrial Health Engineering. John Wiley and Sons, Inc., 440 4th Ave., New York 21. 1948 Data Sheets, National Safety Coun cil: No. 408, Antimony and Its Com pounds No. 499, Anentc and In Iriot^ game Compounds *; Beryllium (in preparation) No. 312, Cadmium No. 443, Lead _Z No. 426, Magnesium No. 306, Manganese No. 203, Mercury No. 485, Titanium No. 267, Zinc andZinc Oxide No. 382, Zirconium Powder Dreesen, W. C., Dalla Valle, J. Edwards, T. I., Miller, J. W, and, ers, R. R., A Study of Asbestosis'. the Asbestos Textile Industry, U.' Public Health Bulletin No 241, U. Hygi industr K00LPADS cut the price you pay for sweat Sweat is one of the most expensive luxuries in modern industry. Production slows as workers stop frequently to wipe glasses, mop brows and gain relief from sweat. Cellulose sponge StaSafe KOOLPADS soak up that sweat (up to six times their own weight, in fact). Some workers even dampen KOOLPADS in water for refreshing coolness. KOOLPADS pay for themselves in keeping men on the job. KOOLPADS pay for themselves in safety. (Help solve the problem of blurred glasses and sweat-stung eyes.) KOOLPADS pay for themselves in worker comfort, which contributes to increased production. KOOLPADS pay for themselves in re-use. (Rinse in seconds and use again and again.) Write today for a tree sample KOOLPAD STANDARD SAFETY EQUIPMENT COMPANY 431 NORTH QUENTIN ROAU RAIlATINE, ILLINOIS 13 HECXEl ST. BELLEVILLE 7. N. J. 12921 W. WASHINGTON SlVD. LOS ANGELES 66, CAUF. 104 855 EAST 152nd STREET CLEVELAND 10. OHIO CIRCLE 70 ON READER CARO National Safety News, June 2 963 j lie Health Service, Washington 25, .C. 1938. Drinker, Philip, and Hatch, T. F., Industrial Dust, 2nd Edition. Mc Graw-Hill Book Co., Inc., 330 W. 2nd St., New York 36. 1954. Elkins, H. B., Chemistry of Indus trial Toxicology, 2nd Edition. John Wiley and Sons, Inc., 440 4th Ave., New York 21. 1959. Hunter, Donald, The Diseases of Occupations, 2nd Edition. Little Brown and Company, 34 Beacon St., Boston. 1957. Hygienic Guide Senes. Amencan Industrial Hygiene Association, 14125 Provost, Detroit 27. Industrial Ventilation--A Manual of Recommended Practice, 7th Edition. American Conference of Governmen tal Industrial Hygienists, Committee on Industrial Ventilation, Box 453, Lansing, Michigan. 1962. Johnston, R. T.. and Miller, S. E., Occupational Diseases and Indus trial Medicine. W. B. Saunders Com pany, Philadelphia. I960. Lanza, A. I., Silicosis and Asbestosis. Oxford University Press, New York. 1938. Patty, F. A, editor, Industrial Hy'tene and Toxicology, Volume I, id Edition, 1958, and Volume II, 2nd edition (in preparation). Interscience Publishers, 250 Fifth Ave., New York 3. "Report (Joint) of the Committee on Pneumoconiosis and the Commit tee on Standard Practices in Com pensation of Occupational Diseases," Year. Book, American Public Health Association, 1790 Broadway, New York 19. 1933. Review of Literature on Dust, U. S. Department of the Interior, Bureau of Mines, Bulletin 478. U. S. Government Printing Office Office, Washington 25, D. C., 1950. 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