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FILE NAME: National Safety Council (NSC) DATE: 1963 June DOC#: NSC040 DOCUMENT DESCRIPTION: NSC - National Safety News - Dust, Fumes, and Mists in Industry Val. 87, W;>. 6 6 Poor F obert's Almanack-- Robert D. Gidel 20 Tool 7 rend 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 he Hard Way 38 Epidemic (Diary of a Safety Engineer)-- Bill Andrews 89 Dusts, Fumes, and Mists in Industry-- Data Sheet 531 4 Voice ( : the Reader 6 Accideit Barometer 8 News t "iefs 10 Safety v'alvc 14 Coming Events 30 Ideas 7 hat Worked 40 Wire fiom Washington 44 Off the Job 46 Fire T ps 47 Consultation Corner 49 Personals 64 Library 71 Deeping Posted 82 For Distinguished Service 85 President's Medal 106 New Safety Equipment 108 Buyers' Guide 109 Reader Service Card 17 Product Literature 1IS Advertisers' Index. Director: Ralph Moses Cover: William Wendland Photographer: James B. Lehman Statements and opinions advanced in signed av tid es and advertisem ents arc personal expressio of the authors and advertisers, not necessary those of the National Safety C o uncil. . N a t io n a l Sa f e t y N ew s is published montni> by National Safety Council. Copyright 1963 to National Safety C ouncil. Printed in U .S .A . ond class postage paid at Chicago, Illino is,. additional mailing offices. Subscription rat" / $7,10 a year. Single copies S I, 10. A ll prices su - jeet to 10 per cent discount to N atio nal Sate - Co uncil members. Quantity prices fo r yearly su scriptions and single issues on request. Memo A udit Bureau o[ Circulation. 33,500 copies of this issue were prin ted A N A T I O N A L S A F E T Y COUNCIL TECHNICAL SERVICE DATA SHEET S 3 ! DUSTS, FUMES, AND MISTS IN INDUSTRY Copies of this data sheet will be available for purchase, within 30 days. Subscribers to the Council's data sheet maintenance service will receive a copy in the next quarterly mailing. Introduction 1. Industrial dusts, mists, and fumes, their hazards and their con trol, are discussed in this data sheet.* The general principles presented can be applied to evaluate most in dustrial situations involving these air contaminar ts 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 hygimist. Such help may be obtained from his own company, insurance carrier, private consul tants, or state health or labor agency. ' 3. To proif ct the health of em ployees who work where a dust, fume, or mist treated 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 properlies of the specific dust, fume, or mist and' its possible physiologic;! effects on employees must be ascertained. "This data sheet covers toxic and irri tating air contaminants encountered in industry. It doe; not include a discussion of the exploshe. properties of such air borne particulate matter. This d ata sheet is one of a series published by the N atio nal Safety Co uncil, reflecting exp erien ce from many sources. Not every accept a b le s a fe ty p ro ce d u re in this fie ld Is n e c e s s a rily in clu d e d . This d ata sheet should not be con fused with A m erican S a fe ty Stand ards, fed eral law s, insurance re quirem ents, state law s, rules, reg ulations or m unicipal ordinances. b. The particular exposure must be evaluated by dust counts or- by chemical analyses of air 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 operation 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 absorbedin 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, National Safety News, June 1963 m however, both ingestion and' skin contact are of rela' iveiy minor impor tance in industrial poisoning inso far as dusts, fumes, and mists are con cerned. Origin and F'roperfies of Particulate Matter 9. The dust ntrmally 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 oe harmful because either the dust rray be nontoxic or body mechanisms capture, remove and eliminate or isolate the small amounts of dust mapped 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 dus' may remain in the lungs. Sources JO, The term dust as used in in dustry is generally applied to air borne solid particles that range in size from 0.1 micron to 25 microns (one micron = 1/10,000 centimeter -- 1/25,000 inch). Process dusts below 0.5 xnicrc n in size are rare. Dusts above 5 microns, in size usually will not stay air-borne long enough to present an inb. slation problem. , 11. Dust ma) 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 Fig ure 1. Dusi from fo und ry sand is generated during the shake-out of castings, The m echanical action of the shake-out m achine disperses the dust. Path taken by the dust particles as they are draw n into the nood shows the efficiency of the local exhaust system. (Courtesy Am erican Foundrymen's Saciet,') 90 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 c u b ic ''^ 9 H |^ H ^ 'l o w e r pi air (mppcf), resulting from j 'y l l l B B B f'-' 23. 1 centimeter of material reduced' attractei particles 1 cubic micron in size W ulIslK ' rate tar occupy an air space of 2 d,0Qg ^ ^ K ," their si. 1 8 . Even smaller amounts of dusts, fumes, and mists, will make Wjj l l l workroom atmosphere hazard o u si^^ B For example, the threshold limi-' ai value for lead, as adopted by American Conference of G overn-t^^S mental Industrial Hygienists, is 0 .2 9 8 1 milligram per cubic meter of aifjpll (m g/cu m), which is 0.00000021 ounce per cubic foot. Therefor the dispersion of only 0.002 ounL.,, of lead will be enough to give threshold limit value of 0.2 mg/c of dust or fume in an air spac 10,000 cubic feet (280 cubic-jp ters). The concentrations th a t)m il be present in the workroom.w it harm to health are different fo rd i ent substances. 19. A person with normal sight can detect dust particles assn cl;'/ as 50 microns in diameter. Smallest air-borne particles can be detected individually by the naked eye only when strong light is reflected from? them. Dust of respirable size (below| 10 microns) cannot be seen withou| the aid of a microscope. 20. Most industrial dusts consist)! of particles that vary widely in si: with the small particles greatly out numbering the large ones. Conse quently, with few exceptions, -wha| dust is noticeable in the air around an operation, probably more mvjt sible dust particles, than visible, ong are.present. Separation in air-borne dust 21. Dust in the air may or maj not have the same composition -asg its parent material. The determining factors are the particle size and density of each component in the original mixture, and the hardness'^ of the materials (hard materials will/tj resist the pulverizing action of A mechanical device.) 22. For example, foundry mold-.:|| :mg sand contains a large percentage m of free silica (quartz) with a lower .| percentage of clays. Most of the clays consist of fine particles that can be JJ 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'; M ..............Rational Safety News, June 1963 U J more si cause 0 ty and fitience: Miners' crons v The est dusts in TA borne : cause c cles in will rer room 2 of time moreor from _tl the lar them dgreater tides it Inha Nationa lower percentage o: free silica. digestive tract before they are elimi 23. Dust partices are, of cournsea,ted. Hence the final toxic effects attracted by gravity. Their settling of larger dust particles may be de rate through still air will vary with layed. The larger panicles of irri heir size, density and shape. Mi- tant dusts can cause immediate effects ! croscopically small particles settle out in the upper respiratory system. I more slowly than larger particles be- 27. Ragweed pollen, which var cause of their relatively minor densi- ies from 18 to 25 microns in diameter | ty and because ci their being in- can cause hay fever from its action I fiuenced by Brownian movement. in the upper respiratory system. This Mineral particles larger than 10 mi- type of dust and other allergenic j crons will settle out relatively fast, types, as well as bacterial and j The estimated sett :ng rates for silica irritant dusts, can cause difficulty ji dusts in still air arc given in Table I. even in the larger air-borne sizes. 28. When dust-laden air is in haled, some of-the larger particles are TABLE 1, S E'T U N G RATES FOR SILICA DUSTS 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, Tim e to throat, and other portions of the Size in Microns Fall 1 Foot (minutes) upper respiratory system. 29. The bronchi and other re 0.25 590.0 spiratory passages are covered with 0.50 187.0 a large number of tiny, hairlike 1.00 54.0 cilia or microscopic whiplashes, 2.00 14.5 which aid in the removal of dust 5.00 2.5 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 24. Most of the particles in aairc-tion tends to push mucous and j! borne industrial dusts are small. Be- deposited dust upward to the mouth i ause of air currents, the fine parti- so that the particles can be ex | cles in dust clou is at an operation pectorated or swallowed. L will remain suspended in the work room air for relatively long periods Retention of dust F of time. The smaller dust particles, 30. Many studies have been made i moreover, will ravel farther away in an effort to determine the amount J from their point of origin than will of dust that is retained-in the lungs,- the larger particles so that the far but there is no simple answer to this ther dust is from its source, the question. It has been shown that greater the perce ttage of small par- the size of the dust particles, the I tides it contains. I 5 Inhalation ol Dusts, Fumes, \ and Mists | ' 25. With the exception of such 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. fibrous materials as asbestos, dust :jj particles must usually be smaller than Sizes of particles inhaled ] 5 microns in order to enter the alveoli 31. Although an occasional dust I or inner recesse: of the lungs. Al- particle of larger size will enter the | though a few particles up to 10 lungs, particles less than 3 microns in I microns in size r a y enter the lungs diameter are the-most likely to do so I occasionally, ne trly all the larger and thus have the greatest oppor particles are trapped in the nasal tunity to cause a physiological re passages, throat, larynx, trachea, and action. In silicotic lungs, for example, I bronchi, from which they are expec dust particles under 3 microns greatly torated or swalk wed into the diges- outnumber larger ones, and many I tive tract. particles are less than 1 micron. I 26. When lamer particles of cer- 32. In the case of very fine f Piin toxic dusts are trapped in the fibrous asbestos dust, an exception j, upper respiratory passages, they occurs in the size of particles in | can be absorbed by the body fluids haled. Many Fibers up to 100 microns j in the nasal passages and in the long have been found in the lungs Figure 2. M etal vo la tilized by the boat o f w eld ing later condenses to' form a fum e. On this bench-welding in sta lla tio n , fumes are removed al th eir point of origin b y a p ro p e rly located local exhaust installation. (Courtesy Am erican Foundrymen's Society) of asbestos workers a.t 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 effects 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. Meta! 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 Nevtfs, Jun 1963 91 Substance C h a lc e d o n y Chert C ris fo b a liie Flint Jasper . Quartz Tridym ite Tripoli (Roftensfone) TABLE II. SELECTED IN DUSTRIAL M INERAL DUSTS Description and Uses CRYSTALLIN E FREE SILICA (Si02, including m icro crystallin e forms) A heat-resistant, ch em ically inert form of m icrocrystalline q u artz. A d ecorative m ate rial. Rare in industry. A m icrocrystalline form of silica. An impure form of flint used in ab rasive s. A crystalline form of free silica, extrem ely hard and inert chem ically; very resistant to heat. Q.uartz in refracto ry bricks and amorphous' silica in diatomaceous earth are altered to cristobalite when exposed to high tem peratures (c a l cin e d ). C risfo b aliie is exten sively used in precision casting by the hot w ax process, dental laboratory work, and certain specialty ceramics. A m icrocrystalline form of native quartz, more opaque and g ranular than ch alce d o n y. Used as an a b rasiv e and In ceram ics. A m icrocrystalline im pure form of silica sim ilar to chert. Used fo r decorative purposes. Rare in industry. Vitreous, hard ch e m ically resistant free silic a , the most common form in nature. The m ain constituent in sandstone, igneous rocks, and common sands. V itreo u s, colorless form of free silica. Formed when q u artz is heated to 870 C (1 ,5 9 8 F). A porous, siliceous rock, resulting from the decomposition of chert or siliceous lim estone. Used as a b ase in soap and scouring pow ders, in metal polishing, as a filtering ag en t, and in wood and p ain t fille rs. A cryp to crystaiiin e form of free silica. Threshold Lim iP in Million P article s per Cubic Foot of A ir* - ' Calculate from fo rm u la :*- 250 ` % S !0 2~ + ~ 5 Diatom aceous ear h Silica ge! AM ORPHOUS FREE SILICA (N o n c rysta llin e ) A soft, gritty am orphous silica composed of minute siliceous skeleton.; of small aq u atic plants. Used in filtration and decolorization of liquids, insulation, filler in dyn am ite, w a x , textile s, plastics, p ain t, and ru b b er. C alcin e d and flu x-cal cined diatomaceous earth contains ap preciab le amounts of cristobalite, and dust levels should be the same as for cristobalite. A regenerative absorbent consisting of the amorphous' silica m anufactured by the action of HCi on sodium silicate. H ard , glossy, q u artz-like in a p p e a ra n ce . Used in d eh yd rating and in drying and as a ca ta lyst ca rrie r. Amorphorus ~ 20 mppcPCalcined -- use formulae 250 S ILIC A T ES (Com pounds m ade up of silicon, o xyg e n , and one o r more m etals with or without h yd ro gen . These dusts cause nonspecific dust reaction s, but g en e rally do not in terfere with p ulm onary function or result in d isa b ility.) Asbestos Clays Feldspar A h yd rated magnesium silicate in fibrous form . The fib e rs a re b elieved to be the more hazardous component of asbestos dust, A great variety of alu m inum -silicate bearing rocks, plastic when wet, hard when d ry . Used in pottery, stoneware, tile , b ricks, cem ents, fille rs, and a b ra sives. K aolin is one type of d a y . Some d a y deposits m ay include a p p re ciab le q u a rtz. Com m ercial grad es of clays m ay co ntain up to 20 per cent q u a rtz. Mos t a b u n d an t group of m aterials, composed of silicates of alum inum with sodium, potassium, calcium , and rarely barium . Most econom ically important m ineral. Used for ceram ics, glass, abrasive wheels, cements, insulation, and fertilizer. 5 mppcf+ 50 m ppeff 50 m p pcfj *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, compounds containing more than 1 per cent silica, calculate threshold limit from formula: 250 % Si02 -f 5 92 National Safety News, June 1963 Fuiier's Kaolin Mvrcc Partien T a lc Verm ic tTh: COJTiDC TABLE II. SELECTED IN DUSTRIAL M INERAL DUSTS (Continued) S ILIC A T ES (Compounds made up of silicon, oxyg en, and one or more metals with or without h yd ro g e n . These dusts cause nonspecific dust reactions, but g en e rally do not In terfere with p ulm onary function or result in d isab ility.) F u lle r 's earfh K a o lin M ica Portland cement s Silicon r carbide (C arb oru n du m ) T a lc V erm iculite A hydrated silica-alum ina compound, filte r medium and as a catalyst and insecticides. associated with ferric catalyst carrier and oxide. Used as a in cosmetics and A type of clay composed of mixed silicates and used for refractories, ceramics, tile, and stoneware, A larg e group of silicates of va ryin g composition, but sim ilar in p hysical properties. A ll have excellen t cle avag e and can be split info very thin sheets. Used in ele ctrical insulation. Fine powder containing compounds of lime, alu m in a, silica, and iron oxide. Used as construction m aterial. Bluish-black, very hard crystals. Used as ab rasive and refractory m aterial. 50 mppcft 50 mppcft 20 mppcft 50 mppcft 50 mppcff A hydrous magnesium silicate used in ceram ics, cosmetics, p ain t, and pharm ace u ficals, and as a fille r in so ap , putty, and p laster. An expanded mica (hydrated magnesium-alurninum-iron silicate). w eight a g g re g ate s, insulation, fe rtilize r, and soil conditioners, rubber and paints, and as a catalyst carrier. Used as in lightfille r in 20 mppcft 50 mppcff Threshold limit: giver, 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 ^TsiO niT i;i ing anthrax stores or wood bark may be essentially inert and remain 38. Definition. Silicosis has been or grain dust containing parasitic in the lungs indefinitely with no defined as "a disease due to breath fungi. f. Irritation of the nose and throat, which is caust d by acid, alkaii, or 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 irternal tissues, which may result from inhaled radioac tive materials such as radium and its daughter products and from other radioisotopes that emit highly ionizing radia1ion. Pneumoconioses 34. Pneumoconiosis comes from 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 determines the type of condition or recognizable irritation, and a few like limestone dust may be gradually dissolved and eliminated without harm. Silicosis 36. The most important lung dis ease caused by the inhalation of mineral dust is silicosis--well-known in industries where crystalline free silica dust is present, such as foun dries, glass manufacturing, granite cutting, mining, and tunneling in quartz rock, It is found throughout the world, and in the past it has had 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 all these names, and it is caused by ing air containing silica (S i02) characterized anatomically by gener alized fibrotic changes and the de 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 of which symptoms may be present), and by characteristic X-ray find ings." * 39. Factors of influence. Sili cosis has been known to manifest itself after widely differing periods of exposure to silica dust. Appar ently, development of the disease depends upon: a. The amount and kind of dust in haled. b. The percentage of free silica con injury. A numrer of organic dusts dust from crystalline free silica, us tained in the dust. are capable of producting lung dis ually quartz (see Table I I ) . c. The form of the silica. . eases, but no' 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. cosis in plants and on jobs where 35. In very rare cases, enough dust had been inhaled to cause mechanical blockage of the air spaces. Flour dust has been known dust control is not adequate. Engi neering control is still the basic means of preventing this disease, and dust control equipment and proce '"'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 to cause this condition. Some dusts dures must be carefully maintained. Broadway, New York 19. p 100. National Safety Nows, June 1963 93 li How one of the world's m o st Wfgl| important insurance companies chose th is sym bol... and why Sure, Wausau has landmarks more impressive than this depot. And as for trademarks, Employers M utuals' handsome of ice in Wausau would be a far betr-er reflection of our coast to coast operations and our $325 million assets. But there's another dimension to Employers M utuals of Wausau. And when we set out to define it and describe it, we find the depot does it best. Back in 18''4, the first train puffed its way throe gh the Wisconsin timberlands, sum m oned n o rth to Wausau by tae thriving lumber in dustry. From then on, the depot stood as proc f th a t this community was no longer the "faraway place," as the earlj Chippewas had de- 94 scribed it in giving Wausau its name. This Wisconsin community is an integral part of the operating phi losophy of Employers M utuals of Wausau, just as it has been through out the 52 years since this mutual insurance company was founded. Call this neighborly concern or "Main Street" friendliness and co operation. I t 's a way of doing busi ness our policyholders seem to like and we don't want to lose. Employers M utuals 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 of the nation through 145 offices. We are one of the largest and most experienced underwriters CIRCLE 40 ON READER CARD in the field of workmen's compensation. We w rite group h ealth andaccident, fidelity bonds, and all forms of fire and casualty insurance, including automobile. We write only nonassessable policies. We're proud of our unbroken record of dividendsavings. And, as a mutual company, we're dedicated to the prevention of loss. I Employers "Good 1 people to i Mutuals do business || with" I of Wausau The powers cf resistance of the individual cone erned. 'The presence cr absence of a com plicating process such as infection. 40. Many theories have been ad vanced over ths years to explain why crystalline free silica acts as it does in the lui as. Theories have been based on trie hardness of the material and tie 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 oi sharpness of the particles, but m a combination of slight solubility with a physiochemicai 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 developmem of silicosis is still ping on in vinous parts of the world. If the precise mechanism of silicosis could b ; determined, better medical prevent.ve measures might be developed and possibly a cure could be found. 42. Three stages. Silicosis is gen erally classified in three separate stages by medical authorities. More sophisticated classifications are some &W- times used for the various X-ray stages and complications of the dis ease, but for a basic understanding `he three stages give a good break down. 43. The first stage of the dis ease . produces no disability. The affected man can carry on his work is well-as ever. Frequently, the in dividual is not aware that anything is wrong, and the disease is revealed only by opaque nodular shadow's 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 in all toy any means. Labored breathing on heavy exertion usually is noted first, a id a dry cough also may be present. 45. The thirl stage can develop after the second stage even though the individual has been removed from ex posure to silica dust. However, the progress of the disease will be slow er 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 over come 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. 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 oj 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 silic-a 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-microcrystalline. ) 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 cristobalite. 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 National Safety Mews, June 1963 95 physiological effects of these prod very high concentrations of certain asbestos textile industry A it w ucts have not been well defined. silicate dusts. recommended that the dust c o n c e i t Until mote experience with human 62. Disabling pneumoconioses tration be kept at less than 5 mPPcf beings is available, it is beiieved from exposure to abnormally high to prevent asbestosis. Evaluation of these products should be handled concentrations of mica, tremolite an exposure to abestos dust is based with care. talc, and kaolin dusts have been de on the total amount o f dust because 57. Fne silica and silicates. Free scribed in the literature. The clinical it has proved out in practice 'that silica is uicombined silicon dioxide signs are not the same for these sili if the fine dust is kept below th' (SiO.j). Silicates contain silicon cate dusts as for free silica, but the suggested threshold limit, the concen and oxygei combined with other ele symptoms can be marked. tration of injurious fibers will also ments in i more complex molecule, 63. The body does not have ade be kept within safe limits. Analyses o: minerals, particularly in quate defense against indiscrimi geological reports, are sometimes re nate amounts of dust of any kind. Talcosis ported as percentages of oxides, Therefore, although specific symp 69. As used in industry, "talc" which may include Si02, A120;,, toms have not been described for is a very general term. To the geolo K2Q, Fe._,U,. The Si02 reported in many mineral dusts, the general ex gist, talc is a hydrous magnesium sili such chemical analyses is the total perience would indicate that dust cate, which may be a relatively pure of the silk on dioxide present, both levels should be kept within thresh mineral or may be mixed with tremo the free si ica (if present), and the old limit values or below (Table II). lite or with dolomite depending upon silica combined in the mineral. Such where it is mined. The term "talc" is analyses aie not reliable indications Asbestosis applied commercially to carbonate X of the si icosis potential of the 64. Asbestos is a general term ap mixtures that have the same general '-5 material. plied to several minerals having a feel and physical properties; it als&ip&i 58. It is uncombined or free silica that is mo t: important in industrial dust expos ire. So that an exposure can be prcperly evaluated, the per centage. of uncombined silica must be determined by petrographic analysis using a polarizing microscope or, preferably, by X-ray diffraction analyses ind special analytical chemical procedures. 59. Theie has been some experi mental evidence that some dusts may tend to inhbit the action of silica on the body, but this inhibiting action is so sligh. and uncertain that it must be di mounted in practice. In fact, there ilso is evidence that the nonsiliceous components of a dust mixture containing free silica may provoke a c.isabling condition more severe than that caused by the silica acting alone fibrous character. These asbestos is applied to pyrophyllite, a hydrous*' minerals are hydrated silicates of aluminum silicate, which frequently magnesium with variable amounts of is mixed with a high percentage of iron, calcium, sodium, potassium, quartz. The free silica generally and aluminum present as impurities. found with pyrophyllite can cause 65. Asbestos when inhaled pro duces fibrous tissue in the lungs of both men and animals. It has been shown that fibers of asbestos must silicosis. It is therefore essential to know which talc is being used in order to evaluate a specific dust ex posure. be present for the production of 70. Talcosis is usually associ ti asbestosis. Other silicate minerals of the same chemical composition but ated with tremolite talc. This disease ,Tfj produces changes in the lungs and'''-SB t: nonfibrous in form produce no re symptoms similar to those of as- , O! action or a relatively mild reaction, bestosis. d: but not the severe reaction of fibrous ' asbestos dust. Anthracosilicosis CC 66. These facts lead to the con 71. Anthracosilicosis, a complex jy ? a: clusion that asbestosis is mainly the form of pneumoconiosis, is a chzonic P- result of physical irritation of the ' disease caused by breathing air con- j lung tisssue and not of a chemical taining dust that has free silica asyw j be action, which is thought to be one of one of its components and that is ` w; the causes of silicosis. It is suspected generated in the various processes Wi that lung cancer may be induced by involved in mining and preparing----^ ch 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. 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 anthracite (hard coal)** and, to a - ijj jUl lesser degree, bituminous coal. - Ja] OD 72. The disease is characterized | we anatomically by generalized fibrotic | changes throughout both lungs and | by the presence of excessive amounts of hai 61. in many industries, men have to form "asbestos bodies" where the W: worked with silicate dusts that con fibers are encapsulated. This diffuse -`Dreesen, W. C,, Dalla Valle, J. M., Edwards, T. I., Miller, J. W,, and Sayers. of tained no free silica without devel fibrosis probably begins as a "collar" R. R., A Study of Asbestosis in the As pe opment of disability or of nodulation about the terminal bronchioles. bestos Textile Industry, U. S. Public in the lungs. The X-ray may show There is evidence that other min Health Bulletin No. 241, U. S. Public sisi shadow's indicating dust deposits in erals having a fibrous character can Health Service, Washington 25, D. C. exp the lungs, but the pneumoconiosis is produce a reaction similar to that 1938. ver: essentially harmless. However, par of asbestos. Fiber glass, however, I!,!Anthracosilicosis among H a rd - C o a l non tially disabling pneumoconioses have does not produce such a reaction. Miners. U. S. Public Health Bulletin No. endi been reported where men have 68. Following a study by the 221, Li. S. Public Health Service, Wash witr worked for long periods of time in U. S. Public Health Service of the ington 25, 'D. C., 1935. exp( 96 National Safety News, June (19W Natiu-.-. i JJ])i(IfiHI!f VfifrWWlfM41MT4et<lirtrW<STrfxh u .-V.ilrrriUKAx:. of carbonaceous and siliceous ma terial. Such lungs on autopsy are coal black. "3. Symptoms found in early radges of the disease are shortness of breath, cough w in a coal-black sputum, pain in the chest, and in some ctases physical weakness. In the advanced stages, there are loss of weight and decrease! 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 mixtuns of coal and quartz produced mere 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. M iscellaneous pneumoconioses 75. Even though a dust is classi fied as harmless, excessive amounts of it can lead to trouble by causing a pneumoconiosis or simply by me chanically irritating the walls of the piratory system. Moreover, even -jough there is no chemical or physi cal irritation, mechanical plugging of the lungs and interference with their ordinary processes tan result. Mica dust and kaolin dust are two good examples of dusts that ordinarily are considered benign cut in excessive amounts can cause a troublesome pneumoconiosis. 76. Mica pneumoconiosis has been observed in gr.nding operations where, mica dust, tu t 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. Kaolinosis 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 exposures are massive. Without ad- erse effects, aluminum dust inhalaon has been used as part of an endeavor to prevent silicosis. Also without adverse effects, extensive exposures to aluminum dust have oc Nationol Safety News June 1963 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 genera] 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 the 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. All 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 or disregarded. The metals with lowtoxicity 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 I I I ) . 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 woric areas. 88. It should be recognized that lead is a normal constituent of plants and 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. 97 and eliminate smal amounts without harm. When intake rates exceed the normal excretion kvel, build-up oc curs in the body. There is a safe level of absorption, and if the con centration of leac dust in the air ,of work areas is kepi 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 ioxiciq 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 dsease that can re sult from the inh illation 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 lost of weight. In the chronic type, known as berylliosis, there may be loss of appetite and weight, weakness, cough, extreme difficulty 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 sq ns 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 ingestior of beryllium oxide, beryllium metal, or any of the beryl lium alloys. Only the inhalation of beryllium dust produces systemic disease. 93. Because c 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 oust and fume that arise in the handling of beryllium, its alloys, and its compounds. Beryl lium is toxic in such small quantity as to be considered the most toxic of all elements yet i ivestigated. TA B LE III. S ELE C T E D T O X IC D U STS A N D FUMES': Substance Aniirr Arsenic Barium (soluble compounds) Beryllium Chromic acid and Chromates Cyanide (as CN) D in itro b e n ze n e Fluorides Hydroquinone Iron oxide fume Lead Lead arsenate Magnesium oxide fume Description and Effects Threshold [m f| In M illigram s p a . Cubic Meter of A ir * : c G ra y metal often associated with lead and arsenic. Hazardous from inhala tion and ingestion. Soluble salts may cause dermatitis. Silvery brittle crystalline metal. H az ardous from inhalation and ingestion. Usually encountered as arsen ic trio x id e . Soluble barium chloride and sulfide are toxic when taken by mouth. Light weight, gray metal. The metal, low-fired oxides, soluble salts, and some alloys are toxic by inhalation. Red, brown, or black crystals. Caustic action on mucous membranes or skin. N onvolatile cyanides are ingestion h az ard s. C yan id e s inhibit tissue oxid ation upon inhalation and cause death. Yellow ish crystal. H azard o u s from skin absorption, inhalation, and ingestion. Inorganic fluorides are highly irritant and toxic. Colorless hexagonal crystals. Contact with the skin m ay cause sensitization an d irritatio n . Excessive exposure to dust may cause corneal injury. M ajor sources are cutting and weiding,, Lead fumes and lead compounds cause poisoning after prolonged exposure. Most im portant means of en try into b od y is in h alatio n . Skin absorption is of significance only from such organic compounds as lead tetraethyl. W hite crystals--highly toxic. W hite powder. Inhalation of freshly generated fume m ay cause metal fume fever. 0.5 0.5 0.5 0.002 0.! 5 .0 (skin * *) 1.0 (skin1 2 .5 2.0 15.0 0.2 0 .1 5 15.0 Trinitrotc Uranium V anaaiu: * ' 1 Zinc oxic fume Zircaniurr compo "These threshold limit values were adopted by the American Conference of Govern-^ mental Industrial Hygienists in 1962. 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. Mefol 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 zinc or magnesium or their oxides. Symptoms appear from four to twelve hours after exposure and consist of fever and shaking chills. There is complete recovery usually within one day, and ordinarily the employee can return to the same job without recurrence. However, after a period in which there has been no contact with the fume, for example, The mental 1; `The contribu airsr a j 98 National Safety News, June 1963 bstance TABLE III. SELECTED T O X IC DUSTS AN D FUMES (Continued) Description and Effects Threshold Limit in M illigram s per Cubic Meter of Air* M anganese penfachlorophenai Phosphorus iyetiow) picric acid Sefenium comoounas Sodium hydroxide Tellurium Titanium dioxide Trinitrotoluene mium V anadium pentoxide Zinc oxide fume Zirconium compounds Silvery g ray metal. H azardous from s.o inhalation of fumes or dust. Dark-colored flakes. Harmful Emits toxic fumes when heated. dust. 0.5 (skin **) Poisonous m ainly by in h alatio n . Severe 0.1 burn h a za rd from skin contact, Yello w crystals or liq uid. particularly metallic salts. fumes on decom position, E x p lo siv e -- Emits toxic 0.1 (s k in **) T o xicity va rie s som ew hat acco rd in g to 0.1 the solubility of the specific com pound. Often causes contact dermatitis. W hite, deliquescent pieces or lumps. 2.0 Has severe action upon a il body tissue. S im ila r fa selenium chem ically and in 0.1 physiological effects. W h ite to b lack pow der. Considered in 15.0 the nuisance category. Colorless to yeflow m onoclinic crystals. Emits toxic fumes of oxides of nitrogen v/hen heated to decom position. H ighly poisonous explosive. 1.5 (skin **) Highly toxic and a radiation hazard that requires special consideration. Ye llo w to red crystals. Acts ch iefly as an irritan t to the conjunctiva and re spiratory tract. 0 .0 5 0 .2 5 (soluble com pounds) (insoluble com pounds) 0.5 (dust) 0,1 (fume) Amorphous white or yellow powder. 5.0 The pow der is essentially nontoxic, but freshly generated fume may cause metal fume fever. Most compounds are insoluble and 5.0 h ave low toxicity. "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 i is likely to bring on an attack. I 96. To cause metal fume fever, ; heavy concentrations of fumes are i required. Zinc ox.de fume is the i most' common source, but cases . caused by the inhalation of fumes 1 from magnesium oxide, copper oxide, d other metallic oxides have also ^een 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 fum e). 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 in 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 tc 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 are required: a. A history of prior exposure to the material involved (sometimes not known by affected employees). b. A "challenge dose" of the m ate 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 significantly 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 W ttiihiiuii'hi ...................... :-- ' -- ' ' ' fections from toe inhalation of bac 110. Since radioisotopes are se 116. The currently recommenc teria and fungi exists in several in lectively taken up in individual or threshold limits of particular duf dustries. Pulmonary anthrax from gans, they may cause only localized can be found in the most recentffi-f 1 the inhalation cf dust containing an irradiation. The radiosensitivity of published ACGIH list, 0r thc~ 1 thrax spores has occurred among em the organ dictates the extent of the ACGIH can be consulted directly *" [ ployees engage: in the handling of hazard of a p articular radioactive Inform ation on threshold limits also " u wool and the cmshing of bones from infected animals. 105. Fungi (molds) growing on substance. Solubility and particle size determine how much of the ac tive material will gain access to and can be obtained from the National ...i Safety Council, state occupational I health agencies, the American Indus- I grain has been round in the sputum remain in the blood stream and var trial Hygiene Association, and com- - 1 of workmen shoveling the grain and ious organs. pensation insurance carriers. | are believed to be the cause of out 111. If radioactive air-borne con 117. No one knows the exact f breaks of respiratory disorders. tamination is known to be present, concentration at which men will start I Fungi found ir sugar cane residues control measures are mandatory. If to develop silicosis, asbestosis, or 1 (bagasse) are believed to be part the presence of contamination is un lead poisoning. With some toxic f of the cause cf bagassosis. Fungal known but suspected, sampling must dusts, however, experience has been !, spores formed under the bark of be done to determine whether or not wide enough to establish the present some trees have been blamed for air-borne concentrations of the ra threshold limits as fairly reliable. respiratory diflieu 1ties among em dioisotope are below the threshold 118. For example, if the level o f J g | ployees who dtbark dry logs. limit value. lead in a workroom is kept below'pTS 106. Although the incidence of 112. Good personal hygiene and 0.2 mg/cu m, experience has show ri^ft occupationally related bacterial and good operating techniques are much that cases of lead intoxication wiill fungal infections is found to be more important in the handling of not occur. Experience also ha!') relatively low, he respiratory effects radioactive materials than in the han shown that many men can toleratSI can be troublesome and, in the case dling of most other materials used in lead levels well above 0.2 mgj of pulmonary anthrax, even fatal. industry. cu m without signs of trouble. The basic methods of control are the 113. Engineering controls for same as those lor the pneumoconio radioactive dusts are similar to those Mineral dusts sis producing ousts, but sterilization for other dusts and depend primarily 119. In the United States, the and disinfectior must be added. upon capture at the point of genera threshold limits for mineral dusts - tion. The difference lies in the fact are expressed in millions of par- ( | Radioactive Dusts* that controls for radioactive dusts tides per cubic foot of air (mppcf). j The concentration of a mineral dust ^ 107. A rad oactive contaminant may offer a chtmical toxicity hazard must be extremely efficient. Thresh old limit values for radioactive par is determined by counting dust par in addition to an ionizing radiation ticulate matter are very low, and in some cases 100 per cent efficiency in ticles that are less than 10 microns in size in an aliquot sample aftert'iffl exposure, and it may be present as a gas, dust, furre, or mist. capture and retention is required. sampling a known volume of air. in a known volume of liquid. In 108; Radioactive contaminants some European countries, mlneral^ f e taken into the body may be deposited Permissible Dustiness ' dusts are weighed, and p e n n issib l^ p in various orgats where they consti 114. Threshold limit values of levels are expressed as milligrams; Nuisc tute sources cf internal radiation. mineral dusts and toxic dusts--that of dust per cubic meter of air (m g /| || 1s : The chemical tharacteristics of the is, time-weighted average concentra cu m ). In England and some othefi| const: radioactive contaminant or isotope tions considered permissible for ex areas, the number of particles not be determine the organ in which it will posures of eight hours per day, five cubic centimeter is the current basts jp? of a ; be deposited. The excretion rate is days per week--have been pub of measurement. its lex also dependenl upon the chemical lished by the American Conference 120. In comparing United States*'1' practf nature of the isotope, because the of Governmental Industrial Hygien and foreign dust counts, it is helpful the s; radioactive isotopes of an element ists. These values have been obtained to keep in mind that 100 particles desks follow the same metabolic process as from the experience of many groups per cubic centimeter'is equivalent io T T l I2t do the stable tsotopes of that ele in industry and from laboratory approximately 3 million particles -p-|j mppei ment. studies on animals. They are re per cubic foot. limit 109. If a radioisotope has been viewed annually and changed as nec 121. It is difficult to compare dusts, deposited in the body, the internal essary on the basis of experience. dust counts with results obtained on 7'T tice, t exposure is regarded as continuous 115. These values are set only the basis of weight. However, with to be until the isotope is lost by radiologi as guides for the best practice and either type of measurement, a thresh low it cal or biological decay. In some are not to be considered absolute old limit can be set as an objec fort cases, exposures may last a lifetime. values. There is reasonable assur tive. Experience has shown that olant 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 low these levels. On the other hand, resulted in. a great decrease in the activity and an extensive bibliography, see the chapter entitled "Ionizing Radia tion" in the Acci lent Prevention Manual lor huinstrial Operations, published by the National Safety Council. occupational disease is likely to de velop in some people if the recom mended levels are exceeded consis tently. incidence of occupational diseases. 122. Threshold limits are based on the percentage of free silica where this substance is the impor- troliir. avail a where Nation; 100 Nationa! Safety News, June 1963 "Sit tant constituent of the dust. If silili cosis is to be prevented, these limits ] must not be exceed :d. Concentra| eons of dusts conta ning less than per cent free sil c.a should not | exceed 50 million paiticles per cubic } foot fmppcf). Cor centrations of | dusts containing from 5 per cent to ! 50 per cent free silica should not s exceed 20 mppcf. Dusts containing t more than 50 per tent free silica 1 should be kept at concentrations i below 5 mppcf. 1 123. As more exnerience accu] initiates, original tireshold limits \ sometimes can be modified. In some | cases, it has been necessary to lower j the limits, for the objective is to protect the more susceptible indiI viduals. In a few ctses, experience I has shown that the limits were too | stringent, and it ha; been possible | to raise the limits tc allow for more | reasonable controls. ill | Toxic dusts I 124. In all countries, threshold f limits for toxic dust; are expressed ! in milligrams per cubic meter of j air. With toxic duds, the average ; levels must be kept below the sugj gested threshold limits. In fact, it j T advisable to keep the levels of j tic dusts as low as practical in ;j tne specific circum; lances. Little in j the way of experieice or data will j be developed if the levels are kept . unusually low, but few if any cases of occupational di tease will occur from, these dusts. | Nuisance dusts j 125. Even thorn h a dust may be | considered generally innocuous and | not be recognized a; the direct cause | of a serious patho ogical condition, 1 its level should be kept as low as is ; practical. Dust levels well below j the suggested thre -mold limits are } desirable. t 126, A concentration of 50 ] mppcf is suggested as the threshold j limit for a numter of nuisance j dusts. With good tngineering pracI tice, there is no n ted for this level to be exceeded. Any reduction be low this level will ncrease the com fort of employe; s and improve plant housekeeping. Methods of Control 127. Various methods of cortofling dusts, mists, and fumes are available. Basic engineering dictates where possible an operation should Figure 3. Each of these grinding wheels is p a rtia lly enclosed by an exhaust hood. E fficient local exhaust is achieved by d raw ing the dust into the hoods, through branch ducts, and into a ce n tra l duct which leads to the collection point. (Courtesy A m erican R ou nd sm en 's Society) be made dustless 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. 12S. 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 in a foundry and the use of water in drilling. 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. 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. 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. The number of working hours at the particular exposure can be re duced. However, other methods of control are preferable. Use of respiratory protective equip ment approved for the exposure by the U.S. Bureau of Mines can rive excellent protection against til types of dust, but in most cases ihoulcl 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. N ational Safety News, June 1963 101 t""-------.--.-- ---- --.... . --- I--. . 'H & 4 'j'.aWEWWi;-. J Figure 4. Since this s ving-rram e g rin d er is used in o variety of posif ons, ibe oca) exhaust sys tem must be ad ju stab le. The fle xib le duct (A ) permits movement o the exhaust hood (B) as needed. (Courtesy A merican Foundrym en's Society) nevertheless, should not be con sidered as a universal substitute for adequate local exhaust re moval, elinrnation of the con taminant, or containment. 129. Many : tales 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 obta ned before a local exhaust system is installed. Each employer should therefore know his state and municipal dust control re quirements. 130. Each tape 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 stee] coated with red lead. local exhaust systems 131. A load 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 snould be designed to enclose the process as completely as possible. This method usually is preferred to general ventilation, but should bf used only when the contaminant cannot be controlled by isolation, process revision, or substitution cf 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 p'incipal parts: a. Hoods or ether 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 be 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 re 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 dose 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 (si plied to the room from the outside replace the air that is removetf:'S| the exhaust system. Otherwise's there will be interference with other . exhaust systems in the area or withSlh gas or oil flames in nearby furnaces-1".... Great difficulty has occurred where' an exhaust system caused a slightly negative pressure in a room con taining a gas furnace. As a result- air 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, but" larger exhausts may need a positive air supply (Figure 7). An adequate^ supply of make-up air, temper I when necessary, is one of the mi f frequently overlooked fundamental! of ventilation. Air always should ' supplied in quantities equal to (pi slightly in excess of the amouhtfg exhausted. (gj| 140. The size of the ducts, th || type and size of the dust collectors and the type and size of the fart* and motor (explosion-proof where~g necessary) are among the other fac tors which must be considered in the. a design of an exhaust system. P r e ^ g venting ignition of a combustible!'"""' contaD siderat subject beyoni an ex; should Figure 5. To achieve the p ro p e r exhaust a ,r>lnp) "til velocity, the hoods fo r these b a rre l furrroroqc,;,,* $ can be positioned as close to the furnace spa P os p ra ctica l, Such positioning is made possible, by mounting the hoods on a tro lle y suspend from an overhead track . (C o u rtesy Am eric ' T v Brake Shoe Co.) 102 National Safety News, June 1 9 ^ contaminant is a pr me safety con sideration, Since discussion of the subject of exhaust system design is eyond the scope of this data sheet, > ,,n experienced veniilation engineer t3i should be consulted. 3 141. Also, information can be l secured from several excellent pub I lications, one of whi ;h is the current i edition of Industrial Ventilation-- A Manual of Recommended Prac tice, published by the American Conference of Governmental Indus trial Hygienists. Another is the chapter entitled ` Local Exhaust Systems and Ventilation" in the l Accident Preventkn Manual for \ Industrial Operations, published by the National Safety Council. G eneral ventilatior 142. Where it i; impossible, im practical, or too expensive to con I 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 'he introduction of enough clean air .rom the outside to dilute the con ti taminated atmosphere to a safe level. This metho J requires larger volumes of air than local exhaust h ` systems to accomp ish the same con ?: trol, and will not be effective uni formly over a larg: room. It should be considered only when local ex haust systems require such assis tance. This is usually where the sources of dust am widely dispersed and each is small. 144. General room exhaust and supply fans must be carefully in stalled. Eddy cut rents, which will interfere with local exhaust systems, must be avoided. Employees must not be exposed to excessive con centrations of dus: as the dust-laden air moves away Lom 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 practice to supply clean, tempered air to the work rone 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 fil 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 methods 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 wall 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 will 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. 1.54. Routine periodic clinical examinations, stipple cell counts, porphyrin determinations, and propperly evaluated blood and urine 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 rt l Figure 6. The cen trifug al force created by this g rinding wheel causes the g enerated dust to travel in a w ell-defined path. To prevent d isp er sion of the dust, the exhaust hood is p laced d i rectly in the dust stream , ciose to its source. (Courtesy American Foundrymen's Society) National Safety News, June 1963 103 dusts, the importance of personal hygiene shoul 1 not be overlooked, Tire periodic medical examinations provide a gocd opportunity for in struction of employees in various personal hygie re measures. 157, Good washing facilities, dean lunchrorms, 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 he home or expose other member ; of the family. These recommendat ons become manda tory where such materials as beryl lium and radioisotopes are handled. ACKNOWLEDGMENT The text of his data sheet, which re places Health I ractices Pamphlet No. 4, was prepared b; the Health Committee of the Chemical Section, National Safety Council. The ccntent has been extensively reviewed by n embers of the National Safety Council, representatives of chapters of the Amener n Society of Safety Engi neers, medical authorities, and industrial hygienists. The data sheet has been ap proved for publication by the Publications Committee of he Industrial Conference, National Safeit Council, Figure 7. In this foundry, loco! exhaust hoods ore i ristolled over each station having a shel|.motJu: m achine and glue press, A d eq uate make-up a ir is supplied from ventilating duct situated b n h w JI molding machines and presses, (Courtesy American jndrym en s Society) BIBLIOGRAPHY Accident Prevention Manual for Industrial Operations, National Safety Council, 425 N, Michigan Ave., Chi cago 11. Anthraco.silicosis 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, Arsenic and panic Compounds Beryllium (in preparation) No. 3 12, Cadmium No. 443, Lead No. 426, Magnesium No, 306, Manganese No. 203, Mercury No. 485, Titanium No. 267, Zinc and Zinc Oxide No. 382, Zirconium Powder Dreesen, W. C., Dalla Valle, J, Jvjfj Edwards, T. I., Miller, J. W., and I ers, R. R., A Study of Ashestosisi the Asbestos Textile Industry, U. Public Health Bulletin No. 24! 8C00LPADS cut the price you pay Sweat is one of the most expensive luxuries in modem industry. Production slows as workers stop frequently to wipe glasses mop brows and gain relief from sweat. Cellulose sponge StaSafe KOOLPADS soak up th at sweat (up to six times their own weight, in fact). Some workers ever dampen KOOLPADS in water for refreshing coolness. K O O LP A D S nay fo r th e m se lv e s in keeping men on the job. K O O L P A D S p a y fo r th em selves in safety. (Help solve the problem of blurred glasses and sweat-stung eyes.) K O O LP A D S p a y for th em selves in worker comfort, which contributes to increased production. KO O LPAD S p a y fo r th em selves in re-use. (Rinse in seconds and use ag ah and again.) W rite today fo r a free sam ple KQOLPAD STANDARD SAFETY EQUIPMENT COMPANY 431 NORTH Q U EN TIN ROAD " P A LA T IN E , ILL IN O IS 13 HECKEL ST. BELLEVILLE 7, N. J. 12921 W. WASH NGTQN BLVD. LOS ANGELE! 66, CAUF. 104 855 EAST 152nd STREET CLEVELAND 10, OHIO CIRCLE 70 ON READER CARD ^public Health Servi ;er Washington 25, f fD .C . 1938. : Drinker, Philip, B.nd Hatch, T. F., Industrial Dust, 2nd Edition. Mc Graw-Hill Book Co., Inc., 330 W. 42nd St., New York 36. 1954. Elkins, H. B,, Chemistry of Indus trial Toxicology, 2nd Edition. John Wiley and Sons, Ire., 440 4th Ave., New York 2!. 1955. Hunter, Donald The Diseases of Occupations, 2nd Edition. Little Brown and Company, 34 Beacon St., Boston. 1957. Hygienic Guide Series. American Industrial Hygiene Association, 14125 Prvost, 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. and Miller, S. E., Occupational Diseases and Indus trial Medicine. W B. Saunders Com pany, Philadelphia. 1960. Lanza, A. J., silicosis and Asbestosis. Oxford University Press, New York. 1938. Patty, F. A., elitor, Industrial Hy giene and Toxicology, Volume I, 2nd Edition, I9i 8, and Volume II; 2nd edition (in preparation). Inter science Publisher., 250 Fifth Ave., New York 3. "Report (Joint) of the Committee on Pneumoconio ;:s and the Commit tee on Standard Practices in Com pensation of Occupational Diseases," Year. Book. American Public Health Association, 175 0 Broadway, New York 19. 1933. Review of Literature on Dust,' U. S. Department of the- Interior, Bureau of Mine:, Bulletin 478. U. S. Government Pr nting Office Office, Washington 25, I). C., 1950. BERT CIRCLE 45 ON READER CARD Feathered center with built-in clearance Three-point vertical am! angular adjust* ment for better fit Eight-point suspension for better impact distribution Supersoft headband for day-long comfort H -# .. --;... ""v Guarantees Maximum Safety/Cam fort/Economy Apex safety hats and caps meat or exceed government specifications for impact and penetration. They're ac cepted as a standard by every industry. Compare these advantages . . . and you'll choose Apex! Better fit greater comfort Lighter weight Better impact distribution Quick size adjustment 6yz to 8 Easier to clean for hygienic protection High resistance to abrasion Permanent, molded-in colors Lower replacement and inventory costs---one suspension fits any-APEX hat or cap Select an A PEX safety hat or cap in the style and color you need for any application . . . ~ ALUM IN UM ELEC TR IC A L FIBRE-G LA SS W IN TER L IN E R S L itera ture gives fu ii specifications. Write for free ' copy today. Division o f WHITE Sewing Machine Corporation W ASH IN G TO N & ELM STREETS * C LEVELAN D 13, OHIO National Safety News, June 1963 1LC