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SILICATES (Compounds mad* up of silicon, oxygen, and on* or mar* metals with or without hydrogen. These dusts cout nonspecific dust reactions, but generally do not interfere with pulmonary function or result in disability.! Fuller's earth Kaolin Mien Portland cement Silicon enrbida (Carborsindum) Talc Varmicufito A hydrated silica--alumina compound, associated with ferric ox-de. Used as a filter medium and as a catalyst ond catalyst carrier and in cosmetics and insecticides. A type of day composed of mixed silicates and used for refractories, ceramics, tile, ond stoneware. A large group of silicates of varying composition, but similar in physicol proper* ties. All have excellent deavege and can be split into very thin sheers. Used in electrical insulation. Fine powder containing compounds of lime, alumina, silica, ond iron oxide. Used as construction material. Bluish-black, very hard crystols. Used as abrasive and refractory material. 50 mppeft 50 mppeft 20 mppeft 50 mppeft 50 mppeft A hydrous magnesium silicate used in ceramics, cosmetics, paint, and pharmoceulicals. and as a filler in soap, putty, and plaster. An expanded mica (hydrated mognetrummluminum-inon silicate). Used in lightweight aggregates, insulation, fertiliser, and sail conditioners, as a filler in rubber and paints, and as a catalyst carrier. 20 mppeft 50 mppeft IThreshold limits given for substances its "Silicates' group are for compounds containing teu than I per cent crystalline silica. For compounds containing more than I per cent silica, calculate threshold limit from formula: 250 . * SiO- + 5 Int anthrar spores or wood bark or (rain dust containing parasitic Aingi. L 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 producting 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 Ihe 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 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 a* foun dries, giass 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 as 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 not adequate. Engi neering control is still the baisic meaTi? of preventing this disease, and dust conuoi equipment and proce dures must be carefully maintained. 38. Definition. Silicosis has been defined as "a disease due to breath ing air containing silica (SiO-..) 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 ail 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. Report (Joint) of ihe Committee on Pneumoconiosis and ihe Commune on Standard Practices in Compensation of Occupational Diseases." Ytat Soot. 19!3. American Public Health Association. 1790 Broadway, New York 19 p 100. Substance Ta&LE III. SELECTED TCXlC DUSTS AND FUmES (Csnnnved) Description and Effects Threshold Limit in Milligrams per Cubic Meter of Air* Mongonese Pentochforpphenol Phosphorus (yellow) Pkric ocid Slflium compounds Sodium hydroside Tellurium Titanium dioside Trinitrotoluene Uranium Vanadium pentoxide Zinc oside fume Zirconium compounds Silvery grey metoJ. Hazardous from inhalation of fume* or duel. 5.0 0ark<otord Hokes. Hormful dust. Emits toxic fumes when heated. 0J (skin**) Poisonous moiniy by inhaiotion. Severe burn hozord from skin contact. 0.1 Yellow crystals or liquid. Explosive-- particularly metallic softs. Emits toxic fumes on decomposition. 0.1 (skin**) Toxicity varies somewhat according to ike solubility of tbe specific com* pound. Often couses contact dermatitis. White, deliquescent pieces or lumps. Has severe action upon oil body tissue. Similar to selenium chemically and m physiological effects. 0.1 2.0 0.1 White to block powder. Considered in 15.0 the nuisonce cotegory. Colorless to yellow monoclinic crystals. Emits toxic fumes of oxides ef nitrogen when heeted to decomposition. Highly poisonous explosive. 1_J (skin**) Highly toxic and 0 radiation hazard that requires special consideration. 0.05 (soluble com pounds) 0.25 (insoluble com pounds) Yeltow to red crystals. Acts chiefly as on irritant to the conjunctive and re* spirotory tract. 0.5 (dust) 0.1 (fume) Amorphous white or yellow powder. The powder is essentially nontoxic, but freshly generated fume may cause metal fume fever. 5.0 Most compounds are insoluble and have law toxicity. 5.0 `These threshold limit values were adopted by the American Conference of Cavernmental Industrial Hygienists in 1962. "The word "skin* in this table indicates that the substance can penetrate the skin to contribute to tbe 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 riderosis 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 trie 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 3nd 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 Ousts 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 111). 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 See the following Nuonal S-a fet > Council Data Sheet*: Ar.t.mony and In Compounds, <0S; Arsenic and In Inor ganic Compounds, <99; C-sdmmm 3 I 2. Lead, 4^3, Afagnesiu/n, <16. Munfunrj<. 306. \4f*curx, 203. Titanium. Zmt and Zinc Oxide, 267, Zirconium Fodder 312. fifmrm 4. Sm4 lhl grmdtf ! vwd mi vmritf # pmilimmm, tfc (*( <hw* iy> 1mm mvtt b# wtf|vtbU. TK flnibi* dwtf (A) ptfMh wotiiMirt m4 Kwrt had (B) * (C*rf*y iiMricai Fundr)riM*'i *- ofy) nevertheless, should not be con sidered as a universal substitute for adequate local exhaust re moval, elimination of the Con taminant, or containment. 129. Many states and municipal ities have dust control codes or or dinances with which employers must comply. In a few states, for instance, written approval of plans must be obtained before a local exlrast system- is installed. Each employer should therefore know his state and municipal dust control re- uirements. 130. Each type of exposure must be considered separately. For ex ample. a local exhaust system suit able for welding or cutting of steel might not be satisfactory for weld ing or cutting steel coated with red lead. local exhaust systems 131. A local exhaust system for the control of an industrial dust or fume traps the air contaminant near its source so that an operator standing at the process is not ex posed to harmful concentrations. The system should be designed to enclose the process as completely as possible. This method usually is preferred to general ventilation, but should be used only when the contaminant cannot be controlled by isolation, process revision, or substitution of less harmful mate rials. Even though a process has been isolated, it may still require a local exhaust system. 132. A local exhaust system con sists of four principal parts: a. Hoods or other inlets, into which the air-borne contaminant is drawn. b. Duels, to cany u`ie cor.cainmaied air to a central point, e. 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 are the nat ural air currents in the room and other exhausts or windows in the area. 135. The hood should be shaped to conform to the shape of the area of dust production so as to secure reasonably uniform air velocity over this area. A hood which does not en close the process should be placed with its opening as dose 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 pan of it, should be located so as to re ceive directly dust that is thrown off along a weQ-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- dent 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 Sow from areas where oo dust is produced; that is. air-flow contours should be controlled. 13S. Egh nr 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 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, 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 J. T* ck;*** A# ptmfhtf w^dHnfy. ffc# ft cm fa* <** * mi mt p*m*cmA. $*<h by it ps.bU iwipa-d4 fr M Brtkf Shmm C*4 (Cwry ri-.a.ld r.ot be u.orico'ied. The -periodic medical examinations provide a good opportunity for in struction of employees Ln various personal hygiene measures. 157. Good washing facilities, clean lunchrooms, and clean work clothes can help prevent additional, even though minor, exposure to toxic materials. Also, contaminated work clothes should not be taken borne where a toxic dust could contaminate the home or expose other members of the family. These recommendations become manda tory where such materials as beryl lium and radioisotopes are handled. fifwr* 7. I* ffcit favadry, local tihivil koodl ara intlattad avar rack Italian ka-inp a tknll.-ialdinf macfcioo and glwa pru. Adequate matf-wp a it i twppiied from -ennlatmg duel wtvaled between maldinq machines and prosoot. (Cevreaty American Peendrymen'i Society) lltllOGIAFHY Accident Prevention Manual for Industrial Operations. National Safety Council, 425 N. Michigan Ave., Chi cago 11. Anthracosilicosis 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 Its 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 and Zinc Oxide No. 382, Zirconium Powder Inor Dreesen, W. C.. Dalla Valle, J. M.. Edwards, T. I., Miller, J. W., and Say ers, R. R., A. Study of Asbestosis In the Asbestos Textile Industry, U. S. Public Health Bulletin No. 241. U. S. 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 St.. New York 36. 1954. Elkios. H. B., Chemistry of Indus trial Toxicology. 2nd Edition. John Wiley and Sons. Inc., 440 4th Ave., New York 21. 1959. Hunter. Donald. The Diseases of Occupations. 2nd Edition. Little Brown and Company. 34 Beacon St.. Boston. 1957. Hygienic Guide Series. American Industrial Hygiene Association. 14125 Prevost. 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 Asbes tosis. Oxford University Press, New York. 1938. Patty, F. A., editor. Industrial Hy giene and Toxicology, Volume I, 2nd Edition, 1958, and Volume II. 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.1* 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. ackmowudqment The teat of this dau sheet, which re places Health Practices Pamphlet No. 4. was prepared by the Health Committee of the Cherrucal Section. National Safety Council. The content has been extensively reviewed by members of (he 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.