Document 2RGJ4gYRxd31Ee7wzpbxDjqNg

Fundamentals of Industrial Hygiene 3-PNEUMOCONIOSIS-PRODUCING DUSTS Free silica is the term commonly applied to crystallized silicon dioxide (SiO=), which most commonly occurs as sand, but is also widely distrib uted in hard rocks and minerals. The percentage of crystalline SiO; in a mineral dust mixture is the usual basis for evaluating the hazards asso ciated with the breathing of the mixture. See Table 3-A. TABLE 3-A CRYSTALLINE SIO: IN VARIOUS MATERIALS Material Sormal Range Crystalline SiOt--% Foundry molding sand Pottery ware body Brick and tile compositions 8uffing wheel dressings Road rock Limestone (agricultural) Feldspar Clay Mica Talc Slate and shale 50-90 15-25 10-35 0-60 0-80 0-3 12-25 0-40 0-10 0-5 5-15 Another kind of pneumoconiosis, involving specific lung changes, is called asbestosis caused bv the inhalation of asbestos dust. There are several other lung diseases caused by specific mineral dusts, but thev occur rarelv because exposure to the offending dust is uncom mon. Long exposure to very high concentrations of mineral dusts that do not produce specific lung changes can still be expected to result in some degree of pneumoconiosis even though symptoms may not be noticed. Those responsible for the protection of the health and safety of work men employed in the dusty trades must first find a means of evaluating the dust exposures, and must then apply the best available control measures to keep exposures within acceptable recommended safe limits. The solution of each of these parts of the problem frequently requires the assistance of specialists. To evaluate the exposures, it is first necessary to determine the compo sition of the dust that remains suspended in the air workmen breathe. Operations that involve crushing, grinding, or polishing of minerals or mineral mixtures frequen composition as that of ti primarily concerned wit suSpended with other dm In many mineral miv balance of the mixture produce air-borne dust v found in the original i ing operation involves reversed. In pulverized materia larger particle size than the handling of pulveriz ,)sre of the softer compoi handling methods. These factors make i borne dust, and to anah evaluating the hazard a The extremely small s cal methods of analvsis. the various components analysis (using a polar techniques are usually dures not commonly foi the normal range of cn and industrial composit Measurement The measurement of a which admittedly does In this country, eva made on the basis of t! when relating harmfu technique must be use< The safety professio particles in units kno' thousandth of a millin of an inch.) The sta> tions does not collect micron, and it can rt 96 BCC-S80 LAM021530 6113 18226 3-PNEUMOCONIOSIS-PRODUCING OUSTS exposure. So. that an exposure can be properly evaluated, the percent age of uncombined silica must be determined by petrographic analysu using a polarizing microscope or, preferably, by X-ray diffraction ana lyses and special analytical chemical procedures. With the exception of asbestos 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 can be tolerated. In many industries, men have worked with silicate dusts that contained no free silica without development of disability or of nodulation in the lungs. The X ray mav show shadows indicating dust deposits in the lungs, but the pneumoconiosis is essentially harmless. Disabling pneumoconioses from exposure to abnormally high concen trations of mica, tremolite talc, and kaolin dusts have been described in the literature. The clinical signs are not the same for these silicate dusts as for free silica. The body does not have adequate defense against indiscriminate amounts of dust of anv kind. Therefore, although specific symptoms have not been described for many mineral dusts, the general experience would indicate that dust levels should be kept below the threshold limit values shown in Table 3-C. Asbestosis Asbestos is a general term applied to several minerals having a fibrous character. These asbestos minerals are hydrated silicates of magnesium with variable amounts of iron, calcium, sodium, potassium, and alumi num present as impurities. Asbestos when inhaled produces 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 reaction or a relatively mild reaction, but not the severe reaction of fibrous asbestos dust. These facts lead to the conclusion that asbestosis is mainly the result of physical irritation of the lung tissue 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. Anthracosilicosis Anthracosilicosis, a complex form of pneumoconiosis, is a chronic disease caused by breathing air containing dust that has free silica as one (Text continues on page 116.) 112 o I co UJ = t<a cr>o QZ QUJ (5 LU LU co BCC-881 rz 3 E O < m V* LAM021537 6113 18227 3-PNEUMOCONIOSIS-PRODUCING dusts Q. E E 5 lO j-t- " !3 jo Sh"'55 -OC -QU ,1' So' 'oE E <o c QQ.. 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T3 O I r W tC O -- *co -a ' -<>C.o Ti3"3 oo 114 J3 ft < BGC-382 17--LUNGS: ANATOMY, HAZARDS, MONITORING, AND PROTECTION Pleurisy is caused when the outer lung lining (the visceral pleura) and the chest cavity's inner lining (the parietal pleura) lose their lubricating properties. The resultant friction causes irritation and pain. Lung cancer. No doubt exists that certain aerosols predispose the lungs to cancer. This disease, like emphysema, is on the increase. Pneumoconiosis (dusty lung). This is a catchall word for various pulmonary manifestations of dust inhalation, whether the dust is harmful or not. Two common forms of pneumoconiosis are silicosis and asbestosis. The typical pathological condition in harmful pneumoconiosis is the existence of fibrotic (stringy) tissue in the alveolar sacs, at the "Y" branches in the small bronchi leading to the alveolar sacs, or at lymph nodes in the lungs. This fibrotic tissue, caused by some dust particles, reduces the efficiency of the lungs by making them less resilient, and bv reducing the effective working surface for gaseous exchange. A simple benign pneumoconiosis with little disturbance of pulmonary function can also predispose to such diseases as pneumonia and tuberculosis. Contaminant effects Inhaled contaminants that adversely affect the lungs fall into three general categories: Aerosols, which, when deposited in the lungs, may produce either tissue damage, tissue reaction, disease, or physical plugging. Toxic gases that produce adverse reaction in the tissue of the lungs themselves. Toxic aerosols or gases that do not affect the lung tissue, but are passed from the lung into the blood stream, where thev are carried to other bodv organs, or have adverse effects on the oxygen-carrying capacity of the bloodstream itself. (See Chapter 11, "Toxicology.") An example of the first tvpe is asbestos fiber, which causes fibrotic growth in the alveolar tissue, plugging the ducts or limiting the effective area of the alveolar lining. Other harmful aerosols are certain fungi found in sugar cane residues, producing bagassosis. Hydrogen fluoride is a gas that directly affects lung tissue. It is a primary irritant of mucous membranes, causing chemical bums. Inhalation of this gas will cause pulmonary edema, and direct interfer ence with the gas transfer function of the alveoli lining. 606 E0C2383 Typical of the It without itself beir passes through th corpuscles so the\ Cyanide gas has . oxygen by cells. Sometimes sev mining operation These impair th associated with t Aerosol deposit In the case ot will be nearly th- With aerosols microns, will b gravity and imp In the sacs, Bro' diffusion. Since the ver to reach the alv important area potentially mor fallacy of using the very particl Monitoring i There are a m In emergen< fainted. The will only give Areas when entry. It is r verifv the assi Sampling ft Sampling ti Monitoring LAM021533 6113 18229 17--LUNGS: ANATOMY, HAZARDS, MONITORING, AND PROTECTION as. protection against (a) pneumoconiosis-producing dusts and mists (such as silica and asbestos); (b) toxic dusts, metallic fumes, and mists not significantly more toxic than lead (zinc dust, lead fume, and chromic acid mist are examples); and (c) radionuclides and highly toxic dusts fumes, and mists--significantly more toxic than lead (such as all radio nuclides and beryllium). This third classification is subdivided into three groups, with a differ, ent type of dispersoid respirator for each: half-mask respirators are suggested for use in contaminant concentrations up to 10 times the threshold limit value, full facepieces up to 100 times the TLV, and positive-pressure dispersoid respirators up to 1000 times the TLV. Nuisance dusts and mists are included with silica and asbestos in the first class (a), above. U.S. Bureau of Mines approved respirators should be used even for nuisance materials such as coal, sawdust, and flour, since no one can foretell the possible effects of breathing such materials, and the legal complications that may arise from unapproved nuisancedust respirators may be more costly and troublesome than the use of the approved respirator. Chemical-cartridge respirators are designed for use in low concentra tions of gases or vapors and are also frequently equipped with filters for protection against dusts and mists, during paint spraving. Employee training As is true with all protective equipment, respiratory protective devices will be effective only when acceptable to the worker. The best wav to achieve acceptance is to explain exactly why the respirator needs to be worn, and what might happen if the respirator were not worn. Where nonemergencv respirators are used, the wearer should be al lowed to try on several styles from various manufacturers to choose the one best suited to him. In addition to convincing a worker of the need for wearing a respirator, and providing him with a comfortable model, he must be trained to wear it correctly. Such training may vary from showing the user how to check the facepiece fit of a small dust respirator, to training sessions of several hours for the more complicated self-contained apparatus. During initial training, special emphasis should be placed upon facepiece fit. Several simple tests will disclose improper fit. The exhalation valve can be closed and the wearer exhales (a slight positive pressure should build up in the facepiece without leakage of air at the seal). Or 616 BGC-S84 the filter wearer u few seco allowing harmless Mainten The L disinfect a Is as fo and disir infectant detergen iiianufaci the wear clean far solution, following diluting < water; (> solving s< to 0.005 mat) clam Air dr' nccordim store in a vhere arsenic mav , two weeks after cposure and where * ths and sometimes f" xposure is terminate^ is excreted to a r.0r_ through the kidnev, tected in the un^ urs of the start 0f r a long time after. id BAL (2,3-dime,.. 0 was developed a arsenical gas pOKnT|. tive in prevention ,,( otherwise harmf,,i rsenic compounds ln he treatment of exist;oning, although cases ted in which BAL was uc hydride). Severe strial poisonings with v to be the result of rsine, often produced en hydrogen is generesence of a material arsenic. The gas has i the acid cleaning of the handling of wet it metals plant, in the cars which have held rochloric acids, in the ;s with an acid conirsenic, in the precipi;m with metallic zinc, (rations. ruses a characteristic issive hemolysis lead.ure. It is associated vomiting, diarrhea, color, disturbance of electrocardiographic ,hr)Ofn'a^' ant^' ^ver disfunction. the patient survives long enough, . uiitestations of chronic arsenic poiiin mav aPPear- After exposure, ' iteiit penod of 1 to 36 hours may ue Inhalation of 250 ppm is jutlv lethal. Exposures of 25-50 tor half an hour are lethal and ppi,jnil are lethal after long- er expo- The mean lethal dose (LD) . ae'i.iiknown in man, but in small ' i|Iimals is about 0.5 mg/kg. Arsine ' can be fixed by tissues other than "lood- 1* binds to the kidneys and , er and inhibits respiration of slices these tissues in vitro. In low connitration exposures, clearance of nine from plasma, where it dissolves I|I0 the erythrocyte, is rapid and eflicient- When high concentrations of ,rsine gas are suddenly dissolved in ,'usma, in large acute exposures, the niiount of circulating arsine may exceed the binding capacity of the -rxthrocvtes. and the gas may damr,e vital organs directly. This would explain death due to arsine poisoning iffore hemolvsis occurs. The possibility of arsine formation -hould always be considered when (here is freshly formed hydrogen round ores of the heavv metals, since .irsenic is widely distributed in small imounts and only a trace of it is re quired to produce enough arsine to be troublesome. Asbestos is a hydrated magnesium uiicate found in the minerals chrvsoule. amosite. crocidolite, and tremoiite. Practically all the commercial asbestos used in this country is chrysonle. It is used almost exclusively for heat insulation or for textiles which must resist high temperature, such as heat-resistant clothing and brake linings. Inhalation of excessive quantities of asbestos fiber can produce a fibrosis in the lungs similar to that found in silicosis but somewhat milder and usuallv not so rapidly progressive. Like silicosis, the condition develops and advances slowly and is equally resistant to treatment. There is also good evidence that inhaled asbestos causes lung cancer. Asphalt. Although asphalt itself is considered to be substantially non toxic, it mav cause inflammation or dermatitis on contact in some individ uals. Careful supervision of worker's personal cleanliness is essential in the prevention of dermatitis or other ill effects. Skin contact with the asphalt should be avoided--individuals work ing with asphalt should wear suitable protective equipment, including gog gles to protect the eyes. The effect of exposure to vapors from liquid or cutback asphalt depends on the par ticular solvent added to the asphalt. Steps should be taken to hold the solvent vapor concentration in the breathing zone below its threshold limit value. Where operations re quire heating or grinding asphalt in side a building, suitable ventilation should be provided. B Barium, in the form of its soluble salts, is toxic on both ingestion and inhalation and highlv caustic when applied to the skin. The carbonate 751 LAM021535 6113 18231 fining' : > coal . nUS CO; se of ; 'nhala cles of '"le^t hn, frorn in. 1 PcoHncts produrcrl llv a mol,| p saluting r<?tards 0r :r growth higher 0r. odv Rlohu. cally with roxins. ag. ar|d pre. `t >s found ' produced > the intro- a foreign that, when stimulates iodif. often asnic. Hazingestion rmatitis ind which oxidation, d and amn-ed to as i ranciditv rat-soluble ntioxidants motor lus to inhibit :le which art of the jrI,e mass but opposite electric ;;iari>e and magnetic properties (e.g., (0ton and anti-proton or neutron j anti-neutron), with complete an,dilation of both and production of n equivalent amount of radiation ,,ergv. The positron and its anti`urticle, the electron, annihilate each :,ther upon interaction and produce .a,nma rays. Antiseptic. A substance that preients or inhibits the growth of microjrpanisms; a substance used to kill siicroorganisms on animate surfaces, ,uch as skin. Aplastic anemia. A condition in which the bone marrow fails to pro duce an adequate number of red hlood corpuscles. Approved. Tested and listed as utisfactorv by an authority having ;urisdiction. such as U.S. Department ,( the Interior, Bureau of Mines, or f.S. Department of Agriculture. Arc welding. One form of electri cal welding using either uncoated or coated rods. Aromatic. Applied to a group of hydrocarbons and their derivatives characterized bv presence of the benzene nucleus (molecular ring structure). See also aliphatic. Arsenic. Silvery brittle crystalline metal. Hazardous from inhalation and ingestion. Usually encountered as arsenic trioxide. Artificial abrasive. Materials, wch as carborundum or emery, sub stituted for natural abrasive such as sandstone. Artificial radioactivity. That pro duced bv bombardment of a target clement with nuclear particles. Io dine-131 is an artificially produced radioactive substance. Asbestos. A hvdrated magnesium silicate in fibrous form. The fibers are believed to be the more hazard ous component of asbestos dust. Asbestosis. A disease of the lungs caused bv the inhalation of fine air borne fibers of asbestos. Asepsis. Clean and free of micro organisms. Aspect ratio. In air distribution outlets, the ratio of the width of the core of a grille, face, or register to its length. Asphyxia. Suffocation from lack of oxygen. Chemical asphyxia is produced bv a substance, such as carbon monoxide, that combines with hemoglobin to reduce the blood's ca pacity to transport oxygen. Simple asphyxia is the result of exposure to a substance, such as carbon dio e, that displaces oxygen. Asthma. Constriction of the bron chial tube muscles, in response to irritation, allergy, or other stimulus. Atmospheric pressure. The pres sure exerted by the weight of the atmosphere--about 14.7 pounds per square inch, which is equivalent to the pressure exerted bv a column of mercury (Hg) 760 mm high. See absolute pressure and gage pressure. Atom. All materials are made of atoms. The elements, such as iron, lead and sulfur, differ from each other because they contain different atoms. The word "atom" comes from the Greek word meaning indi visible. Now we know it can be split and consists of an inner core (nu cleus) surrounded by electrons which rotate around the nucleus like the planets around the sun. As a chemi cal unit, it remains unchanged during any chemical reaction, yet may un- 861 BCC2386