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Substance Chofcedony Chert ' Cristobolite Flint Jaiper Qvcrtr Tridymiie Tripoli (Rettcnttone) TABLE II. SELECTED INDUSTRIAL MINERAL OUSTS Description ond Uses CRYSTALLINE FREE SUICA (SiOj. including mkrocrysfelline forms) A heat-resitrant, chemJcotfy inert form of microcrysfal/trte quartz. A decorative material. Rare in industry. A mkrocrystalline tarns ol silko. An impure form of flint used In abrasives. ^ A* crystalline form of free silko. extremely bond ond Inert chemically] vary mislont to heat. Quartz in refractory bricks ond amorphous silko in diatoms* ceout earth are ottered to crlstobolite whan exposed to high temperatures (col* cined). Cristobglite it extensively used in precision costing by the hot wax process, dentol laboratory work, ond certain specialty ceramics. - A micracrystolline form of native quarts, more opoque end gronwtor tharf cholcedony. Used os on abrasive ond In ceramics. A microcrystaftine impure form of silko similor to chert. Used for decorative purposes. Rare In industry. Vitreous, herd chemkolfy resistant free silica, the moil common form In nature.. The mein constituent In sondstone, Igneous rocks, ond common sends. Vitreous, colorless form of free s3ko. Formed when qvortx *m heated to 670 C (1.398 F). A porous, siliceous rock, resulting from the decomposition of chert or silkeous limestone. Used ot o base in soap ond scouring powders, in metol polishing, os o filtering ogent, ond in wood ond point fillers. A cryptocryUolline form of free silko. Threshold Limit in Million Particlesper Cubk.Foot of Air* ColevJote from formula.-** 220 \ S0, + 3 Diatamoceous earth Silko get AMORPHOUS FREE SUICA (Noacryslolline), A soft, gritty amorphous silica composed of minuft silkeous skeletons of small aquotk plants. Used in filtration ond decolorUotion of liqutdi, Insulotion, filler in dynomite, wax, textiles, plastics, point, ond rubber. Calcined and flux*col* cined diatomoceous earth contoins appreciable amounts of crlstobolite, ond dust levels should be the some os for crisiobolite. A regenerative absorbent consisting of the amorphous silko manufactured by the oction of HCI on sodium silkoti. Hord, glossy, qvartz<4ike In appeoronce. Used in.dehydrating ond in drying and os o catalyst carrier. Amorphorut = 20 mppcf Colored r: use. formula: 220 % SiOj + 3 20 mppcf Asbestos Cloys Fetdspor SILICATES (Compounds mode up of tRkOfl, oxygen, ond one or more metols with Or without hydrogen. These dusts cause nonspecific dust reactions, but generally do not interfere with pulmonory function or result tn disability.) A hydrated magnesium silicate In fibrous form. The fibers ore believed to be the more hazardous component of asbestos dust. A greet variety of aluminum'--silicate bearing rocks, plostic when wet, hord when dry. Used in pottery, slonewore, tde. bricks, cements, fillers, ond abro* slvei. Koolin Is one type of cloy. Some cloy deposits moy include appreciable Qvertj. Commercial grades of cloys moy contain up to 30 per cent quartz. Most abundant group of materiols. composed of silicates of olumlnum with sodium, potassium, calcium, and rarely barium. Most economically important mineral. Used for ceramks. glass, abrasive wheels, cements, insulation, and fertilizer. 3 rpppeft * 30 mppcft 30 mppeft These threshold limit values were adopted by the American Conference of Governmental industrial Hygienists in 1962. `Threshold limit values obtained from formula apply to all thc'xuStances in "Crystalline Free Sitka" group. Threshold limits given for substances in "Silicates** group are for compounds containing tru than I per cent crystalline silica. For compounds containing more than I per cent silica, calculate threshold limit from formula; 2JG % SID. + 5 92 Notional Safety News, June 1962 TASLE II. SELECTED INDUSTRIAL MINERAL OUSTS (Continued) SILICATES (Compounds mod* up of silicon, oxygon, ond ono or more meiofs with or without hydrogen. These dusts cause nonspecific dust reactions, but generally do not interfere with pulmonary function or result In disability.) fuller's eorth Koolin Mica Portlond cement Silicon ' carbide. (Carborundum) Tale VermScutlt* A hydrated silko--alumina compound, associated with ferric oxide. Used as o fitter medium end . at e catalyst end cofdysl .carrier end in emmetks ond insecticides. A type of day composed of mixed silksres and used for refractories, ceramics, tile.'and stoneware. - A large group of sRkotes of varying composition, but simOcr in physkal proper* ties. All have excellent deovage ond can be split into very thin sheen. Used In electrical Insulation, Fire powder containing compounds of lime, alumino, silica, end iron oxide. Used as construction mdterlol. BluhMjlock, very hord crystols.* Used ot abrasive and refractory material. SO mppeft 50 mppeft 20 mppeft SO mppcf) 30 mppeft A hydrous magnesium tftcofe | used In ceramics, canneries, pcinf, end phot. meceutkals, ond os a filler in soap, putty, ond piaster. _ An expanded mice (hydrated moqnesivnxtumlnvnvlran silkate). Used in light, weight aggregates, insulation, fertilizer, ond soil conditioners, as a filler in rubber end paints, end as a catalyst carrier. 90 mppeft SO mppeft tThreshold limits given for substances in "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; 230 f- SiOa + 3 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. Pneumotoniose* - 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 kin\l 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 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 harm. Silicosis 36. The most important lung dis ease caused by the inhalation of mineral dust is jtl/cwij--well-knownin 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 quart2 (see Table fl). 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 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 oodulation 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 6} 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. * e. The form of the silica. d. The size of the particles inhaled. e. The duration of the exposure. -Continued on page 9S ?"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 too. Nations! Safety Newt. June 1962 92