Document QgdmJ7jG9ZMoZO0zg1JNmj8D6

A NATIONAL SAFETY COUNCIL TECHNICAL SERVICE PLAINTIFF'S EXHIBIT GF-2346 DATA SHEET 531 r<763 DUSTS, FUMES, AND MISTS IN INDUSTRY c Copies of Ms data Meet will be available for purchase within 30 days. Subscribers to the Coundts data sheet maintenance service will receive a copy in the next quarterly mailing. C NUCH01143 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 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 britatins air contaminants encountered in industry, it does not include a discussion of the explosive properties of such air borne particulate matter. National Safety News, Jtmt 1943 This data sheet is one of o 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 sheaf should not be con fused with American Safety Stand ards, federal laws, insurance re quirements, state laws, rules, reg ulations or municipal 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, bow the dust, fume, or mist is dispersed. 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 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. fi - 0709 89 however, both ingestion and skin contact are of relatively minor impor tance in industrial poisoning inso far as dints, fumes, and mists are con cerned. 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 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 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 nth 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 die dust formed (Figure 1). r 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 0J micron in size. In some cases, the hot material reacts with the air to form an oxide. Examples are lead oxide fame 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 b the oil mbt 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 b 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. flger* 1 Dw*f from foundry wad b paiwlad *****9 hokm call of costings Tt* wcfcnnifJ oedon of IW ihqfro not mockimm flginn dost. Potfa (oka* by tW dm* peridot on drown Into da* hood dan tW offirioiacy f fW UcoJ ooKoaii* ijrvfom. (Coomay Aaorkao haiiifyu'i torfoty) Magnitude of particle] 16. When a solid b broken into finely divided panicles, its surface area b 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 10i: (1,000,000,000,000 or one trillion) panicles 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 b broken into, finely divided particles, the volume occupied by the mass b slso in creased because of the voids between the panicles. A dust concentration of 50 million phnides per cubic foot-of air (mppcf), resulting from I cubic centimeter of material reduced to panicles 1 cubic micron in size, will occupy an air space of 20.000 cubic feet. 18. Even smaller amounts of toxic dusts, fumes, and mists, will make a workroom atmosphere hazardous. For example, the threshold limit value for lead, as adopted by the American Conference of Govern mental Industrial, Hygienists, is 0.2 milligram, per cubic meter of air (mg/eu m), which b 0.0000002 ounce per cubic foot. Therefore, the dispersion of only 0.002 ounce of bad will be enough to give the threshold limit value of 0.2 me/cu m of dust or fume in an air space of 10,000 cubic feet (280 cubic me ters). The concentrations that may be present in the workroom without harm to health are different for differ ent substances. 19. A person with normal eye- ' sight can detect dust particles as small as 50 microns in diameter. Smaller air-borne panicles can be detected individually by the naked eye only when strong light b reflected from them. Dust of respirable size (below 10 microns) cannot be seen without the aid of a microscope. 20. Most industrial dusts consul of particles that vary widely in size, with the small particles greatly out numbering the large ones. Conse quently, with few exceptions, when dust b .noticeable in the air around an operation, probably more invis ible dust partides than visible ones are present. Separation in air-bamo dust 21. Dust in the air may or may not have the same composition as its parqnt material. The determining factors are the particle size and density of each component in the original mixture, and die hardness of the materials (hard materials will resist the pulverizing action of a mechanical device.) 22i' For example, foundry mold ing sand contains a large percentage of free silica (quartz) with a lower percentage of days. Most of the clays consbt of fi"p particles that can be air-borne, but most of die 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 of clays and a much . lower percentage of free silica. digestive tract before they are elimi 23. Dust panicles are, of course, nated. Hence the Anal 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 their size, density, and shape. Mi tant dusts can cause immediate effects croscopically small particles settle out in the upper respiratory system. 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 of their being in can cause hay fever from its action^ fluenced by Brownian movement in the upper respiratory system. Th& Mineral particles larger than 10 mi type of dust and other allergenic crons will settle out relatively fast types, as well as bacterial apd The estimated settling rates for silica irritant dusts, can cause difficulty dusts in su'll air are given in Table 1. even in the larger air-borne sizes. 28. When dust-laden air is' in haled, some of the larger particles are TABU I. SETTLING RATES FOR StUCA DUSTS . trapped by the hairs jn the nose. Other dust particles are removed from the air as it passes over the Size in Microns Tima to Foil 1 Foot (minutes) moist mucous membranes of the nose, throat, and other portions of the 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, bairlike 1.00 544) cilia or microscopic whiplashes, 2.00 14J 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 24. Most of the particles in air borne industrial dusts are small. Be cause of air currents, the fine parti cles in dust clouds at an operation will remain suspended in the work 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. room air for relatively long periods Retention of dust of time. The smaller dust particles, 30. Many studies have been made moreover, will travel farther away in an effort to determine the amount 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 percentage of small par the size of the dust particles, the ticles it contains. rate of respiration, the density of Inhalation of Dusts, Fumes, and Mists 25. With the exception of such fibrous materials as asbestos, dust the dust in the air, the efficiency of the dust-catching mechanism, and probably many other factors are in volved. particles must usually be smaller than . Sizes of particles inhaled 5 microns in order to enter the alveoli 31. Although an occasional dust or inner recesses 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 microns in size may enter the lungs diameter are the most likely to do so occasionally, nearly 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, bronchi, from which they are expec dust particles under 3 microns greatly torated or swallowed into the diges outnumber larger ones, and many tive tram. panicles are less than 1 micron. 26. When larger particles of cer 32. In the case of very fine tain toxic dusts are trapped in the fibrous asbestos dust, an exception 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 in the nasal passages and in the long have been found in the lungs. figure 2. *WMl nMEnd by Mm Seal at aM- Iftg tetar cm^wmi t* form a fwN. On tfau hinrii inrtalifian, fawn ar raawvad I that* paiat mi arifin by a prapariy located local aohaatf ImtoHation. (Caartvty Aowricoa Fawndrywaa' 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 offsets 33. The physiological reactions caused by the inhalation of air borne particulate matter Mil 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 eases, 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- Notlnnol Safety News, June 19&3 MICH01145 91 Substance TABU 11. SELECTED INDUSTRIAL MINERAL DUSTS DescripHoc and Urns CRYSTALLINE FREE SILICA (SO}, including mlcreerystellinu . r-> forms) y* Threshold Limit in Million Particles per Cubic Foot of Air* Otolendony Own Cristobofito i Rinl Jasper Quartz THdyniti Tripoli (Ronensrone) ' A hoot lUilstowt, chcmkaKy Inoct form of picroctystcdlirvp^quortx. A Jecuiatire BMMriflL lots fat industry. A mkrocrysialNne form of iBes. An irapuvo form of flint usod In obretfos. A' erystalTme form of free sffica, extremely hard and Inert diemimlyt vary lasisionl to heat. Quoits In tefrectory brido and amorphous .Rica in iCnlamo. enow tailfa am abatad to cristaboBm whan exposed to high leeiperaturat (col* dnad). Cristobait. Is aatoiuhfoly used in pmdrlon costing by the hot won process, dental laboratory work, and certain specialty ceramics. A mteracrystafline form of native quart], moro opoquo and granular than dtolcsdowy. Usod as on abrasive and to commies. A mkrecrysfaflbw impure form of silica similar la chan. Used for dueomtive purposes. Rom in industry. Vitreous, hard chaasesfly msislont free sBka, the mast common form In nature. The main constituent In sandstone. Igneous redo, and common sands. Vitreous, colorless form of free ifcti, Fanned whan quarts b healed ro >70 C (UTS a A porous, siliceous rode, owlHng from tho docomposiflon of ehun or sfliceous iimostono. Usod os o bos* to soup and scouring powders, in matal polahmg, os o filtering agent, and in wood ond point fOtors. A cryptocrystalline form of free silica. Coleriato from formula:** 250 % SiO, -p 5 Diotomoceous earth SBtea gal AMORPHOUS FREE SlUCA. (NoncrystoJUne) A soft, gritty amorphous dies composed of minute siltcoous skeletons of small aquatic plants. Used to filtration ond doeolortoation of liquids, insulation, filler to dynamite, wax, textiles, plastics, paint, ond rubber. Calcined end flux-cal cined dtofomoceous earth contains appreciable amounts of erhrobofite. end dust levels should be the same os for crisfebaltte. A regenerotive absorbent consisting of the amorphous tSica manufactured by the action of HCI on sodium sflkcto. Hard, glassy, qvam-llke in appearance. Usod to dehydrating ond to drying ond as a catalyst carrier. Amorphenrs s 20 mppcf Calcined as us# formula: 250 %SiOj -H E 20 mppcf Asbestos Cloys Feldspar SILICATES (Compounds mod* up of *33con, oxygon, ond ono or moro metols with or without hydrogen. Thoso dusts couso nonspecific dust reactions, but gonorofly do not interfere wfth pulmonary function -or rosuil in dbobiliryj ( A hydrated magnesium sBkote to fibrous form. The ffoers ore believed to be the more hazardous component of asbestos dust. A great variety o* alumfount--rsiHcote bearing rocks, plastic when wet, hard when dry. Used in pottery, stoneware, tfte, bricks, cements, fillers, ond abra sives. Kaolin b one type of day. Seme day deposits may todudo appreciable quartz. Commercial grades of days mey contain up to 20 per eem quartz. Mast abundant group of raaturiab,'composed sf dBcatai of aluminum whh sodium, potassium, cofdum, and rarely barium. Atom economically Important mineral. Used for ceramics, glass, abrasive wheels, cements, insulation, and fertilizer. 5 mppeff 50 mppeff SO mppeff There threshold limit values were adopted by the American Conference of Governmental Industrial Hygienoa in 1962. "Threshold limit values obtained from formula apply to all the substances in "Crystalline Free 50ica" group. tThreshold limits given for substances in "Silicates" group are for compounds containing lea than l^per cent crystalline silica. For compounds containing more than 1 per cent silica, calculate threshold limit from formula: 2J0 *SiOj + S n MICH01146 -* TABLE II. SELECTED INDUSTRIAL MINERAL OUSTS (Continu'd) SILICATES (Compounds mode up of silicon, oxygen, and one or more metals with or without hydrogen. These dusts cause nonspecific dust reactions, but generolir do not interfere with pulmonary function or resuit rn daobilrtyj Fuller's earth Kaolin Mies Portiorwf cement S3icon carbide (Carborundum) Tele Vermiculfte A hydrated silica1 alumina compound, associated with ferric oxide. Used as o filter medium and as a catalyst and* eatdysf corner end in cosmetics end h-cHcUm. / A type of day compos'd of mind sOicotas and uwd for rofrectories, ceramics, dt, and stoneware. A large group of silicates of scrying composition, but similar in physical proper" ties. Ail have excellent cleavage and can be split Into very thin sheets. Used In electrical insulation. Bne powder containing compounds of bn*, alumina, silica, and Iran outdo. Used at construction material. '- Bluish-block, very hard crystals. Used as abrasive and refractal y material. 30 mppeft 30 mppeft 20 mppeft \ SO mppeft 50 mppeft A hydrous magnesium sffieafe wed in ceramic:, cosnwfia, paint, and phar. maeeutfcols, and os a fifler in seep, putty, and plaster. An expanded mica (hydrated magnesium ohnninunwron sBkote). Used in light* weight aggregates, insulation, fertitor, and soil conditioners, as o filler in rubber end points, and as a catalyst carrier. 30 mppeft 30 mppeft tThreshold limiu given for substances in' "Silicates" group are for compounds containing leu than I per cent crystalline silica. For compounds containing more than I per cent silica, calculate threshold limit from formula; ISO 9c SiO- + 5 ing anthrax spores or wood bark or grain dust containing parasitic fungi. f. Irritation of the nose and throat, which is caused by acid, alkali, 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 internal tissues, which may result from inhaled radioac tive materials such as radium and its daughter products and from other radioisotopes that emit highly ionizing radiation. 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 injury. A number of organic dusts are capable of productiug lung dis eases, but not all these diseases are classified as pneumoconioses be cause they are not all a "dusty con dition" of the lung. 35. In very rare cases, enough dust had been inhaled to cause mechanical blockage of the air spaces. Flour dust has been known to cause this condition. Some dusts may be essentially inert and remain in the lungs indefinitely with no recognizable irritation, and a few like limestone dust may be gradually dissolved and eliminated without barm. 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 dust from crystalline free silica, us ually quartz (see Table II). 37. Although considerable prog ress has been made in dust control in industry, men still develop sili cosis in plants and on jobs where dust control is sot adequate. Engi neering control is still the basic means of preventing this disease, and dust control equipment and proce dures must be carefully maintained 38. Definition. Silicosis has been defined as "a disease due to breath ing air containing silica (Si02) 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 tained in the dust. c. The form of the silica. d. The .size of the particles inhaled. e. The duration of the exposure. --Continued on page 95 "-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. Notional Safety News, Jane 1963 MICH01147 93 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 far trademarks. 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 giving Wausau its name. This Wisconsin community is an integral part of the operating phi losophy of Employers Mutuals of Wausau, just as it baa been 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 la evident in our rela tionship with policyholders every where. We do business in all the principal cities ofthe nation through 145 offices. We are one of the largest and most experienced underwriters oscu *. ON UAOM CA*S in the field of workmen's compensa tion. We write group health and accident, fidelity bonds, and all forms offire 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. "Good 'people to do business with' Employers Mutuals of Wausau f. -The powers of resistance of the individual concerned.. g. The presence or absence of a com' " piicating process such as infection. 40. Many theories have been ad vanced 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 stDl 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 stages by medical authorities. More sophisticated dassificadons 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 carry 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 in 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 progress of the disease will be slow^ er without condnued dust exposure. Breathing may become severely labored. The worker is far below nor mal physically and is suscepdble to respiratory diseases. Chest X-rays a result, the available functional may show an enlarged heart as a re volume of the lung is reduced. sult of the body's attempts to over come the resistance of restricted 51. In some advanced cases, the fibrous tissue will slow down or blood vessels in the lungs. Pulmonary even prevent the diffusion of oxy tuberculosis is a frequent complica gen from the lung to the blood in the tion and occasionally results in death. capillaries, and the blood in the 46. Detection and development. area will not be completely oxy Silicosis may be detected by chesty genated. The fibrous tissue can also X-rays in each of the three stages. affect the blood vessels by oblitera However, X-rays alone are not ting them or cutting down the flow of sufficient for a positive diagnosis, blood. AH these effects tend to for the shadows may be due to a variety of other conditions, includ ing infection or another type of limit the rate at which oxygen is supplied to the bodj^tissues. Emphy sema is the most obvious symptom. pneumoconiosis. The individual must 52. As the inhalation of silica have had a definite exposure to free continues over the years, the amount 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. of fibrous tissue win, 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 convened 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 50. Action of silica on the lungs. At the points in the lung where silica dust is deposited and accumu made by the U. S. Public Health Service, it has been recommended that thd threshold limit value for 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 crude or amorphous diatomite be placed at 20 mppcf (see Table II), but that the atmospheric concentra tion for dust containing cristobalite lung tissue, does not permit the ready be kept under 5 mppcf. passage of oxygen and carbon diox 56. Various commercial products ide, and as h proliferates, cuts down containing particles of silica under the amount of normal lung tissue. As ^ 1 micron in sire are available. The National Safety Nows, June 1963 MICH01149 95 physiological effects of these prod* ucts have not been wel] 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 (SiOj). Silicates contain silicon and oxygen combined with other ele ments in a'more complex molecule. Analyses of minerals, particularly in geological reports, ate sometimes re ported as percentages of oxides, which may include S10., AI.O*, K.O. Fe-da. The SO. 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 experi mental 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 h must be discounted in 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 ht the lungs, but the pneumoconiosis is essendally harmless. However, par tially disabling pneumoconioses have been reported where men have worked for long periods of time in 94 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, buFthe symptoms can be marked. 63. The body does not have ade quate defense against indiscrimi nate amounts of dust of any kind. Therefore, although spedfie symp toms have not beat 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 It). 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 pro duces fibrous tissue in 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 hing 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 UIPUM 4 5(1 asbestos textile industry,* it, was recommended that the dust concen tration be kept at less than 5 mppcf to prevent asbestosis. Evaluation of an exposure to abestos dust is based on the total amount of dust because it has proved out in. practice that if tbe fine dust is kept below the suggested threshold limit, the concen tration'of injurious fibers will also be kept within safe Emits. Talcosia . 69. As used in industry, "tale" is a very general term. To tbe geolo gist, talc is a hydrous magnesium sili cate, which may be a relatively pure mineral ormay be mixed with tremo lite or with dolomite depending upon where it is mined. Tbe term "talc" is applied commercially to carbonate mixtures that have the same general feel and physical properties; it also is appDed to pyrophyllite, a hydrous aluminum silicate, which frequently is mixed with a high percentage of quartz. The free silica generally found with pyrophyllite can cause sQicosis. It is therefore essential to know which tale is being used in order to evaluate a specific dust ex posure. 70. Talcosis is usually associ ated with tremoEte talc. This disease produces changes in the lungs and symptoms similar to those of as bestosis. Anthracosilieosii 71. Anthracoslicosis, a complex form of pneumoconiosis, is a chronic disease caused by breathing air con taining dust that has free silica as one of its components and that is generated in the various processes involved in mining and preparing anthracite (hard coal)** -and, to a lesser degree, bituminous coal. 72. The disease is characterized anatomically by generaEzed fibrotie changes throughout both lungs and by the presence of excessive amounts *Drccsen. W. C_ Dalla Valle. J. M,, Edwards. T. L. Miller. J. W,, and Sayers. R. R, A Study of Asbestosis In the As bestos Textile Industry, U. S. Public Health Bulletin No. 241, U. S. Public Health Service. Washington 25, D. C. .1938. 'AMthroeasilicosis among Hard-Coal Miners. V. S. Public Health Bulletin No. 221. U. S. Public Health Service, WashJ~don 25. D. C_ 1935. of- carbonaceous and siliceous ma terial. Such lungs os autopsy are coal black. 73. Symptoms found in early stages of the disease are shortness of breath, 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 dusL Coal dust alone in very heavy concentrations over a period of many years can cause breathlessness and ventila tory impairment Miscellaneous pneumoconioses 73. 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 respiratory 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. Kaolinosis has been described as a condition induced by inhalation of dust released in the grinding and handling of kaolin (china day). Where the cases occurred, dust levels of several hundred million panicles per cubic foot of air were common. 78. Aluminum dust is not consid ered to be harmful except where exposures are massive. Without ad verse effects, aluminum dust inhala tion has been used as pan 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 conduded that reasonably good control will prevent harm from alu minum dust 79. Bauxite pneumoconiosis (Sha ver's disease) has been found only m workers exposed to fumes contain ing aluminum oxide and minute'oty uhramicroscopic silica particles aris ing from smdting bauxite in the manufacture of corundum, an adpure form of aluminum oxide. It is essentially a diffuse interstitial fi brosis and marked assodated 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 tiie 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 pordand 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 arseni^, 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 fow 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 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 diem 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 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 followint National Safety Council Data Sheets: Antimony and its Compounds, 408: Arsenic end its inor ganic'Compounds. 499; Cadmium. 312; Lead, 443; Magnesium. 426: Manganese. 306; Mercury, 203; Titanium, 485; Zinc and Zinc Ozidd, 267; Zirconium Powder. 382. Notional Sofoty News. June 1963 M1CH01151 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 con centration of lead dust in the air of work areas is kept below the threshold limit, there should be no difficulty. 89. The importance of maintain ing the concentradon 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 sufI fident 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, 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 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 beryt. littm 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 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 ail elements yet investigated. *1 TABU III. SELECTED TOXIC DUSTS AMO FUMES Substance Description end Efforts Threshold Limit In MBItgrem* per Cubic Meter of Air" Anttaony Arimic Barium [soluble compounds) Bwyffiuw Chromic odd and Chromates Cyanide ( CM) Dteitrobenzene Fluwidas Hydroqwfcum Iron odd* fim Lead toed emanate Megnasium odda fumo Gray motai often aooetofed with load end orseejc, Hazardous from inhato* ton end mgeiton. Soluble tabs may cause dermatitis. 03 SSvery brittle. crystalline motel. Hex* erdous from toboloton end ingestion* Usually encountered as arsenic trioxide. Of \ Soluble barium chloride and sulfide dre tonic whan token by mouth. OJ light weight, gray metaL The metal, lowered oxides* soluble salts, and some alloys are toxic by inhalation. 0JD02 ftod, brown, or block crystals* Caustic 0.1 acton on mucous membranes or skin.. Nonvolatile cyanides ore ingestion haz* orris. Cyanides Inhibit tissue oxidation upon inhalation end cause death. JJDkin--) Yellowish crystal. Kqzordoe fram skin absorption* inhalation* and Ingestion. 1.0 Ukin--> inorganic fluorides are highly Irritant and toxic. 23 Colorless hexagonal crystals. Contact with the skin may cause sensitisation end irritation, besuhs exposure to dust may cause comeal injury. 2.0 Major sources ore cutting end welding. 15.0 Load fumes and lead compounds cause poisoning after prolonged exposure. Most important means of entry kite body a inhalation. Skin absorption b of sign*Beane* only from such organic compounds as lead tetraethyl. 02 White ityitab highly toxic. 0.15 White powder, inhalation of freshly generated fume may cause metal fume fever. 15j0 These threshold limit values were adopted by the American Conference of Governmental Industrial Hysicaisu in 1962. . 94. When the soluble salts of beryllium, especially beryllium fluo ride, come in. contact with cuts or abrasions on die 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 Motel fumo fovor 95. Metal fume fever is an acqte 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. . TABLE 111. SELECTED TOXIC DUSTS AND FUMES (Continued) Substance Description and Effects Threshold limit in Milligrams per Cubic Meter of Air* Monganese Penlodilotophenol Phosphorus (yellow) Picric odd Selenium compounds Sodium hydroxide Tellurium Titanium dioxide Trinitrotoluene Uranium Vanadium pentexide Zinc oxide fume Zirconium compounds Silvery gray metal. Hazardous from inheiotion of fumes or dust. 5.0 Dork-colored flakes. Harmful dust. Emits toxic fumes when hooted. 0-5 Ukin") Poisonous memJy by inhalation. Severs burn hazard from skin cootoct. 0.1 Yellow aystoil or liquid. Explosive-- particularly metallic salts. Emits toxic fumes on decomposition. 0.1 akin") Toxicity varies somewhat according to the solubility of the spedfk com* pound. Often causes conroa dermatitis. White* deliquescent pieces or lumps. Has severe oction upon oB body tissue. SfmUar to selenium chemically and Id physiological effects. 0.1 23) 0.1 White to block powder. Considered m 15.0 the nuisance category. Colorless to yellow monodmfc crystals. Emits toxic fumes of oxides of nitrogen when heated to decomposition. Highly poisonous explosive. 1.5 Likin") Highly toxic and o radiation hazard that requires specie! consideration. &Q5 (soluble com pounds) 0J25 (insoluble com pounds) Yellow to red crystals. Acts chiefly os an irritant to the conjunctiva and re spiratory tract. 0J (dust) 0.1 (fume) Amorphous white or yellow powder. The powder is essentially nontoxic, but freshly generated fume may cause metal fume fever. 5X1 Most compounds ore insoluble end hove low toxidty. 5.0 'These threshold limit values were adopted by the American Conference of Govern mental Industrial Hygienists in 1962. "The word "sitin'* in this table indicates that the substance can penetrate the sltin to contribute to the exposure. after a layoff, resumption of exposure is 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 from magnesium oxide, copper oxide, and 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 (nascentfume). 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- ^ able 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, aod 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 are required: a. A history of prior exposure to the materia] 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 far 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, of 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. Boctorio and fungi 104. The possibility of lung in- Natiaitol Saf.ty Ntwx, June 1963 MICH01153 99 factions from the inhalation of bac teria and fungi exists in several in dustries. Pulmonary anthrax from the inhalation of dust containing an thrax spores has occurred among em ployees engaged in the handling of wool and the crushing of bones from infected animals. 105. Fungi (molds) growing on grain has been found in the sputum of workmen shoveling the grain and are believed to be the cause of out breaks of respiratory disorders. Fungi found in sugar cane residues '(bagasse) are believed to be part of the cause of basassosh. Fungal j spores formed under the bark of - some trees have been blamed for respiratory difficulties among em ployees who debark dry logs. 106. Although the incidence of occupationally related bacterial and fungal infections is found to be relatively low, the respiratory effects can be troublesome and. in the ease 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 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. "For a detailed discussion of radio activity and an extensive bibliography, see the chapter entitled "Ionizing Radia tion" in the Accident Prevention Manual tor Industrial Operations, published by the National Safety Council. 110. Since radioisotopes are se lectively taken up in individual or gans, they may cause only localized irradiation. The radiosensitivity of the organ dictates the extent of the hazard of a particular radioactive substance. Solubility and particle size determine how much of-the ac tive material will gain access to/hnd remain in the blood stream and var ious organs. (. 111. If radioactive air-borne con tamination is known to be present, control measures are mandatory. If the presence of contamination is un known but suspected, sampling must be done to determine whether or not air-borne concentrations of the ra dioisotope are below the threshold limit value. 112. Good personal hygiene and good operating techniques are much more important in the handling of radioactive materials than in the han dling of most other materials used in industry. 113. Engineering controls for radioactive dusts are 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 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, live 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 ance that occupational disease wilt not occur if exposures are kept be 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. 116. The currently recommended threshold limits of particular dusts can be found in the most recently : published ACG1H list, or the ACGIH can be consulted directly. Information on threshold limits also can be obtained from the National Safety Council, state occupational health agencies, the American Indus trial Hygiene Association, and com pensation insurance carriers. 117. No one knows the exact concentration gt which men will start to develop silicosis, asbestosis. or lead poisoning. With some toxic dusts, however, experience has been wide enough to establish the present threshold limits as fairly reliable. 118. For example, if the level of lead in a workroom is kept below 0.2 mg'cu m. experience has shown that cases of lead intoxication will not occur. Experience also has shown that many men can tolerate lead levels well above 0.2 mg/ cu m without signs of trouble. 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 ticles that are less than 10 microns in size in an aliquot sample after sampling a known volume of air in a known volume of liquid. In some European countries, mineral dusts arc weighed, and permissible levels are expressed as milligrams of dust per cubic meter of air (mg/ cu m). In England and some other areas, the number of particles per cubic centimeter is the current basis of measurement. 120. In comparing United States and foreign dust counts, it is helpful to ktep 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 tive. Experience has shown that maintaining dust levels below the recommended threshold limits has resulted in a great decrease in the incidence of occupational diseases. 122. Threshold Emits are based on the 'percentage of free silica where this substance is the impor- 100 ant constituent of the dust. If sili cosis is to be prevented, these limits must not be exceeded. Concentra tions of dusts containing less than 2 per cent free silica should not exceed 50 million particles per cubic foot (mppcf). Concentrations of dusts containing from 5 per cent to 50 per cent free silica should not exceed 20 mppcf. Dusts conuining more than 50 per cent free silica should be kept at concentrations below S mppcf. 123. As more experience accu mulates, original threshold 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 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. 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. In fact, it is advisable to keep the levels of toxic dusts as low as practical in the specific circumstances. Little in the way of experience or data will be developed it 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 arc 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 127. Various methods of con trolling dusts, mists, and fumes are available. Basic engineering dicrates where possible an operation should 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. 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 he 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 arc the careful and prop er wetting down of aisles in a foundry and the use of water in 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 lilting 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 1 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-sup plied helmets usually arc required continuously during operations. Respiratory protective equipment. National Safety Nows, Jane 1963 MICH01155 101 figaia 4. Smm Mi tuiai (ran grlaJar k aaad 4a a rarfaty af gatMaac, ilia laeal aakaaUvya. taai aaat balrfl iilakta. Ika UaaiUa *ect |A> . gamin ................. af tfw aakaaal haarf () at | madid. (Caanaay Amrkaa Naadryea'i Sa` aatyl nevertheless. should not be coo- ' sidered as a universal substitute, for adequate local exhaust re moval. elimination of the con taminant. or containment. 129. Many states and municipal-, (ties have dust control codes or or dinances with which employers must comply. Is 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 pans: a. Hoods or other inlets, into which the air-borne contaminant is drawn. h. Duets, to carry the contaminated air to a central point . c. Dust and fume collectors, to clehn 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 frith respect to die system as a whole, design of the exhaust hood demands dte 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 die 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 mth its opening as dose as possible to the point of generadon 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 of! 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 die face of the hood. 137. The fan should be of suffi cient capacity, to maintain the re quired air capture velodty 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 sup plied to the room from the outside to replace the air that is removed by the exhaust system. Otherwise, there will be interference with other exhaust systems in the area or with 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 result air came down the furnace flue, and the area became contaminated with carbon monoxide from die 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, tempered when necessary, is one of the most frequently overlooked fundamentals of ventilation. Air' always should be supplied in quantities equal to or slightly in excess of the amounts exhausted. 140. The size of the ducts, the type and size of the dust collectors, 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 design of an exhaust system. Pre venting ignition of a combustible- br --Mug Mw kaaiit Ml trailer anpeadaJ from aa aaarkaad track. (Caartacy AaeHcae Irak# Uraa CaJ 102 . contaminant is a prime safety con sideration. Since discussion of the subject of exhaust system design is ' beyond the scope of this data sheet, an experienced ventilation engineer should 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 Prac tice, 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. Generalventilation 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 the introduction of enough clean air from 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 wQ] 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 practice to supply dean, tempered air to the work zone for controlled dilution. Wat 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 lot 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 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 indudq 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. 154. 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. Othor control measures 156. Although the most effective method of control is to prevent con tamination of workroom air and thus prevent inhalation of harmful Fiftir* d. TW cootrifogoJ lore* crnitd hy thi cow Ik* jfiwtoifd dif to trorol m m voti-dofmod polk. To pnvtnl dpo*' aioo of tko dU, tko oxkoost hood ii plocod d** roAty in tbo dmt ttroooi. dost to tH aovreo. {Coortosy A--tiw Fooodrymoo't Society) Motional Safsty Nsws, Jon* 1943 MICH01157 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 dean work clothes can help prevent additional, even though minor, exposure to toxic matria) Also, contaminated work clothes should not be taken borne where a toxic dust could contaminate die home or expose other members of die family. These . recommendations become manda- I tory where such materials as beryl lium and radioisotopes are bandied. AOCNOWlEMMfNT The text of this data sheet, which re places Health Practice* 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 National 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, Him 7. hi tiiij hmdiy, leal beN Wadi an humlUd avar aadi aalian tnW| a *--1 rnfifinu anddaa aad gloa pm. Adaqaaia wain ap air b aappBad ban duct bmatad banaan anMlap aaddaet aad pnuai. (Caartaiy Aaarieon faaadtyana't larialy) mUOGUPHY Accident Prevention Mamtol for Industrial Operations, National Safety Council, 425 N. Michigan Ave, Chi cago 11. AnthracosiUcosis Among Hard-Coal Minors, U. S. Public Health Bulletin No. 221, U. S. Public Health Service, Washington 25, D. C. 1935. Brandt, A. D, Industrial Health Engineering. John Wflev and Sons, Inc, 440 4th Ave, New York 21. 1948. Data Sheets, National 5a!ecy Coun cil: No. 408, Antimony and its Com pounds No. 499. Arsenic and Its Inor ganic Compounds Beryllium (in preparation) No. 312. Cadmium No. 443: Lead No. 426, Magnesium No. 306, Manganese No. 203, Mercury No. 485. Titanium No. 267. Zinc andEinc Oxide No. 382, Zirconium Pander Dreesen, W. C. Dalla Valle, J. M., Edwards, T. I, Miller, J. W,, and Say. era, R. R.. A Study of Asbestosis in the Asbestos Textile industry, U. S. Public Health Bulletin No. 241, U. S. K00LPADS cut the price you pay for sweat . 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 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.) HCOOIPAD5 pay for themselves in worker comfort, which contributes to increased production. KOOLPADS pay far themselves in re-use. (Rinse in seconds and use again and again.) , Write today for a free sample KOOLPAD STANDARD SAFETY EQUIPMENT COMPANY 431 NORTH QUCNTIN ROAS PALATINI, ILLINOIS 13 HEOCEl ST. ItUIVUU 7, N. J. MICH01158 12*31 W. WASHINGTON SI.VO. IOS ANGflES M. CAUf. ass CAST IS2jW STREET CUVELAND tO. OHIO CttCU 70 ON UASH .CARO .Public Health Service, Washington 25, D. C. 1938. ' Drinker, Philip, and Hatch, T. F-, > industrial Dust, 2nd Edition. Mc Graw-Hill Book Co,, Inc., 330 W. 42nd Sl, New York 36.T954. 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 Sl, Boston. 1957. Hygienic Guide Series. American Industrial Hygiene Association, 14125 PrevosL 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. 1960. Lanza, A. J-, Silicosis and Asbestosis. Oxford University Press, New York. 1938. Patty, P. A_ editor. Industrial Hy giene and Toxicology, Volume I, 2nd Edition, 1958, and Volume IL 2nd edition (in preparation). Inter science 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. CIXCII 45 ON . >n cass APEX Safety Hats & Caps Feathered center With buill 'n clearance .Three-point vertical und annular adjust ment for better fit Ej^tit-point liu&pcnsion for better impact dntribultan ' With Exclusive glpLV NEW Suspension Design ' vr Guarantees Maximum Select an APEX safely hat or cap Safety/Comfort/Economy Apex safety hats and caps meet or exceed government specifications for impact and penetration. They're ac cepted as a standard by every industry. in the style and color you need tor any application . . . Compare these advantages . . . and you'll choose Apex! Better fit -- greater comfort Lighter weight ALUMINUM ELECTRICAL Better impact distribution Quick size adjustment -- 6V to 8 Easier to clean for hygienic protection High resistance to abrasion Permanent moided-in colors Lower replacement and inventory costs--one suspension fits any APEX hat or cap FIBRE-CLASS WINTER LINERS Literature give futi aoeeiticationx. ' Write for tree (apexj copy today. & SAFETY PRODUCTS OMslon of WHITE Sewing Mmcnine Corporation -^7 WASHINGTON A ELM STREETS CLEVELAND 13, OHIO BERT Sweeper The Damp Sweep Tool has a dou ble steel swivel joining the brush and handle giving easy maneuverability. The tool sweeps under chairs, desks, and tables, and changes direction with out lifting from the floor. A 36-inch cleaning doth with reinforced center hole fits over the handle, and tucks under the brush. The cloth is damp ened with water or a liquid dust re mover. The device is available in 3 models, with oval, triangular, and rec tangular brushes. Available from Wal ter G. Leoge Co., Inc., New York. CIRCM U ON BSAOER CARD Vented Face 5hield \) Full facial protection against im pact without heat problems is the pur pose of the air-vented face shield in troduced by Chicago Eye Shield Co. The shield has .hundreds of holes (.070-inch diameter) in a 2 W-inch by 8-inch area at the mouth level. The resulting effect is a shield with the ventilation of wire screen and a mar lot gin of safety of a laminated multiply window .045 inches thick. The window is held in place by studs and spring clips and the face shield has a deeply molded fiber glass crown. The nylon headgear with a broadbearing cross strap has seven height adjustments. There is a ratchet friction adjustment for a full range of head sizes. ciacif ai on tsADU card Penetrating Primer A rapid-drying, penetrating primer called Myco Primatex. is designed to seal oil oil-soaked wood and concrete flooring. Manufactured by Masury-Young Co., Boston, the primer is said to pre vent oil, moisture, and most chemicals from bleeding to the surface. Traffic sealers and coatings may be applied within one hour after it is put down. A blend of modified resins and cel lulose derivatives dissolved in a com bination of alcohols and esters, the product covers 800 to 1200 square feet per gallon. cracii as on uadi* caid Welder's Filter Plate The Weld-Cool filter plate, manu factured by American Optical Com pany's Safety Products Div., Southbridge. Mass., is used in inert-gasshielded arc welding processes where excessive infrared radiation is presenL It provides visible light transmis sion in the blue region of the spec trum and absorbs the yellow flare associated with certain welding proc esses. The plate is available in shades 10 and 12 and is 2 by 4'/i inches. CIRCll a on rsaou' CARS Portable Radar Alarm Unit The Radar-Eye Minuteman, which provides protection through a radar field, is available from Pinkerton Electro-Security Corf.. Webster. Mass- a subsidiary of Pinkerton's Na tional Detective Agency. Designed for the small business or homeowner, the device weighs 14 pounds and operates off 110-120 volt house current. The turn of a key switches it on and off. Its circuitry sounds an alarm m the event of power or tube failure, tampering, or wire cutting. CWCU M ON UADR CARD MICH01160 Dry Box Gloves Dura-Sol dry box gloves are avail able from Charleston Rubber Co.. Charleston, S.C.. in the standard NeoSol, Buta-Sol, and Rad-Bar . types. Combining a film of synthetic elas tomers with butyl rubber for exam ple. is said to produce a glove with retaining low permeability character istics. The Dura-Sol gloves incorporate a feature that makes detection of dam age by visual inspection possible: The outer polymer film is compounded in ____I SI