Document GKGrd6gnNkM1B3GZaNwOyZNvY

FILE NAME: Garlock (GAR) DATE: 1939 DOC#: GAR034 DOCUMENT DESCRIPTION: National Safety Council Report - Industrial Dust Health P ractice* Pamphlet No. 4 Industrial Dust Published by N ational Safety Council, I n c 20 N orth W acker Drive, Chicago 6 Industrial Dust This pamphlet is one of more than ISO 1. The literature on hazardous Seaff-e Practices and Health Practices ' feet* of dust is so extensive that no at Pamphlets. It is a compilatioo of experi tempt has been made here to cover the ence in accident prevention from many sources. It should not be assumed, how subject in all of its ramifications; -but ever, that it includes even- acceptable to' assemble only the outstanding data procedure in the field covered. Is must bn several of its aspects. This pam not be confused with American Standard safety codes; federal laws: insurance re phlet is intended for employers, plant quirements; state laws, mica and regula safety engineers, personnel managers, tions; and municipal ordinances. Add*. and supervisors generally. The subject lionet {pits # / Ibis pempblet re em itable. Member p rist, i f cents teeb. a m has been approached from the prevention Ik y ad non-member p titrt me request. angle, giving general information on oc cupational diseases caused by dust and on methods of control. No reference is made to the economic and legal aspects - of dust diseases in industry and none *.of the uncommon dusts as, for instance, * might be found in the pharmaceutical * industry, are discussed. There is a short section on dust explosibility. of disability. With the toxic dusts, trouble may result from swallowing or more rarely from skin absorption, as well as from inhalation. Inhalation, how ever, is by far the most important means of absorption of industrial dusts.' 4. Irritation and ulceration of skin and mucous membranes may be caused Physiological Effects o f D ust by such dusts as Cme and chromium 2. T he inhalation of dust may procompounds. duce different types of reactions in hu man bongs: a. Pneumoconioses (sQcosts and asbestosb) which result in specific lung pathology.. 2*. Silicosis increases su scep tib ility to - tuberculosis. b. The systemic reaction caused hy such toxic dusts as lead, radium, man ganese. cadmium and mercury com pounds, when either breathed or swallowed or possibly a b s o r b e d through the skin. Pneumoconiosis 5. Zenker applied the name "poeumonocotdosb" to the various change b the lungs caused by the inhalation of d u st' The te rn has now been shortened to "pneumoconiosis." I t represents three words b o o the Greek, which mean e. A transient disorder known as metal fume fever, from the inhalation of finely divided metallic dust or fume .-particles such as sine oxide d. A reaction,' allergic in nature, caused by breathing organic dusts such as pollen, flour, certain pulverized woods. e. An increase in bronchitis and other acute respiratory infections by breath ing inert, non-fibrosis-prudneing dust such as coal, emery, limestone, ourble. 3. In each of the above cases, the erw^nhalation of dust can be the sole cause Figure t. Our counting by ecaodard light field oMthodi. 1 "lung," "dust" and "abnormal condi tion." The present generally accepted meaning of the word involves the con cept merely of "dusted lung." Tbe kind of dust inhaled determines the type of injury noted in the lungs. However, there is one pathological process which underlies lung disease caused by dust. This consists of a fibrosis or a replace ment of tbe elastic tissue of the lungs by an impervious scar tissue. 6. Research on ji been carried on b the North American continent more actively b the past decade than b any other period. The hysteria with regard to silicosis and other occupational diseases has now largely subsided, and the subject is be ing more carefully considered and more soberly judged. The Problem 7. Modem manufacturing methods are, b many bstanors, creating consid erable dust. Much of this dust is often released b tbe twwwfar area where o* women are working, and this b e t compels a practical solution of the problem. g. The first step b the prevention of injury to health by dust is the control of its concentration so that workers will not be fyp*d to injurious amounts. In order to obtain wide spread control of dust throughout industry, it is necessary that information be developed and dis seminated on the effect of various kinds and amounts of dust to which workers are exposed. Origin and Properties Physical 9. Dust is formed by reducing solid materials to small sizes. Processes like nhr 19?9 19t National Safety Council. Ine. sill rikts reserved. Printell in L io H.r.i'.-J HEALTH I'KACTICES I'Ahi PH LET NO. 4 a nuisance rather than a serious health hazard. Occupational diseases have come to mean so much to industry in medical costs and compensation as well as the health of workers, that there is ample justification for extensive research and investigation in the development of the best possible design in control equip ment. 75. To maintain a safe concentration of dust in the vicinity of dust generating equipment it is necessary to introduce sufficient dean air from the outside to dilute the dust-filled atmosphere to the degree necessary for safety. In the util ization of general ventilation systems, care must be taken to avoid excessive exposure of workers as dust is removed from its source. Especially where local dust systems are being supplemented by general ventilation, it should be seen that eddy currents are not set up to in terfere with proper functioning of the local exhaust. 76. Undoubtedly, the best method of ventilation is the control of contami nated air a t its source. T o do this, there must be sufficient movement of air toward the exhaust opening to counter act any tendency of the dust-laden air to escape into the surrounding atmos phere. Proper hood design will make this possible with the least possible flow of kxhaust air. T he object of an ex haust system is to trap the contaminated air and not to remove the harmful dusts from it. I t Is suggested that the scat tering of large particles may be pre vented by the erection of suitable bar riers or, of course, b y causing them to flow into the collecting duct. For effi cient operation of dust collecting equip ment, all air motion around the source of dust production must be under ab solute control. 77. Proper design and location of the suiionojtening and the rate of air flow into it is a matter of utmost importance. Laws governing the flow of air into ex haust openings have been given in " In dustrial Dusts" by Drinker and Hatch: ' t. Enclose (he process as complete!' as possible and provide internal baf fles to guide the air flow where it is most needed. 2. An exhaust hood which docs not enclose the process should be placed with its opening as close as possible to the point of dust generation since the air velocity in the zone of hood influence decreases approximately with the square of the distance front the face of the hood. 5. Shape the hood to conform with the shape of the area of dust pro duction so as to secure reasonably uniform air velocity over this area. For a given required air velocity at the point of dust generation, the velocity at the hood opening should be as low as possible. This is con trary to the common idea that the hood suction should be high. 4. Provide flanges wherever possible to reduce the air flow from inef fective areas where no dust is pro duced. 5. Locate the hood opening, or part of it, so as to receive directly antdust that is thrown off along a welldefined path, thus utilizing the di rectional energy of the material for its own capture. "Design of Exhaust Hoods (or Dust-Control Systems" by Theo dore Hatch. Harvard Graduate School of Engineering and School of Public Health, Busiou. Ifass. The Journal of Industrial Hygiene and Toxicology. November, 1936. Figure t4. Sweeping with the use of oiled sawdust to alii' dust. Wet vs. Dr)- Drilling 78. On the matter of drilling, H ar rington says: "Dry drilling is. .si course, very much more of a dust producer than wet drill ing--possibly in the ratio of 10 to 1. Wet drilling produces some dust, but if reasonable precautions are taken with wet drilling, and suitable precautions arc also taken as to ventilation, as to the wetting of tbe muck pile, as to the lime in which blasting is done, as to tbe precautions which are taken after going back to the face after blasting . . . there need be no particular harm to workers in those places, as far as dust diseases are concerned." 79. Prof. Philip Drinker, in com menting on the adoption of tbe New York State Code governing dustiness in rock drilling, stated: "This code divides all r<ck formation into two classes, class I being those with less than 10 per cent free silica, by weight, and class 2 Iteing those with more than 10 per cent free silica. If drilling is done in class 1 rock, dust counts must be below 100 million per cubic foot, and below 10 million par ticles if the rock falls in class 2. 2--H.P.P.-4 HEALTH PRACTICES PAMPHLET NO. 4 Figure 2. Left: Operator in monument shed using pneumatic banket. Neither dust control nor respirator has been pro vided. Right: The same operation with goggles and dust-control bood in use. grinding, crushing, blasting and drilling produce dust particles of sizes from the microscopic to the visible, their composi tion being the same as that of the parent materials if not altered chemically dur ing the subdivision. Frequently the percentage of some h ard mineral such as quartz in the fine d u st may be less than th at in the parent material. Common examples are the .mineral or inorganic dusts derived from th e disintegration of rode and the organic dusts Eke wheat and flour. 10. Smoke from burning carbonace ous fuels-- coal, ofl, wood, etc.--con tains droplets as well as dry particles. Tobacco, for instance, produces a wet smoke composed of minute tarty drop lets. T he p artid e size of tobacco smoke b about 0.25 microns. 11. When a solid is broken into fine ly divided particles an d released in the air, one of the important changes that take place is th a t th e space occupied by the broken material and also the sur face areas are increased many times from that of the original mass. For ex ample, if one c c (.061 cu. in.) of quartz is crushed into panicles one cubic micron in size, there will be 10" (1,000,000,000,000 or one trillion) particles with total surface areas of six square meters (9300 sq. in.) as compared with six square centimeters (.930 sq. in.) for the original block. If we assume a dust concentration of 100 million particles to each cubic foot of air, the one c c of naterial will occupy an air space of 10,000 cubic feet. thousandth of an inch) in their longest dimensions in order to enter the inner recesses of the lungs where the damage is caused. It was formerly believed that the hardness and sharpness of quartz particles were deciding factors in the injurious properties of dust, but this view has been generally disproved. (See paragraphs 20 and 29). Hay fever and other allergic types of disease from or ganic dusts or larger particle sizes can be caused by breathing particles into the nose and not having them reach the lungs at all. Ragweed pollen is from 18 to 25 microns in diameter. 13. By comparison a healthy red blood cell is about 7.8 inches, and a white cell up to about 16 microns. A person with normal eyes can see an ob ject SO microns in diameter. However, the reflection of light from a shiny par ticle of quartz may be seen when the particle is as smalt as 20 microns in di ameter. It b to be realized, therefore, that individual dust particles small enough to reach hmg tissue are essen tially invisible to the naked eye. 14. Fumes may result from any of several chemical or physico-chemical changes such as zinc oxide, formed when burning zinc vapors arise from molten brass, or lead occurring in the exhaust of a motor car burning gasoline contain ing tetra-ethyl lead. Chemical 15. The chemical and ranenlogical make-up of the dust are the deciding factors in determining its injurious properties. It has been shown that sili con dioxide (free silica) in the form of quartz may produce a disabling fibrosis, whereas tittle or no fibrosis b produced by the equally hard and sharp cornered aluminum oxide (emery). Classification o f D usts 16. The following classification of 12. .With the exception of such fi brous material as asbestos, the dust par- smaller than 10 microns (one enierno equals one twenty-fifth dusts, according to their physical char acteristics and physiological effects has been arranged by Dr. R. R. Sayers: ^ ORGANIC DUSTS A. Non-Living Organic Dusts As the name implies, these are com prised o i non-viable particles which may or may not be cither toxic or irritant, but nevertheless have effect on the human organism. 1. Toxic or Irritant Quite. These are organic dusts which produce un toward symptoms either systemic or lo cal. Those producing local symptoms are described as irritants, while those producing general symptoms are termed toxic. A dust may be both toxic and irri tant. 2. .AUrrgir. (See paragraph 59.) B. Living Organic Dusts These dusts contain particles capable of reproduction or multiplication, such as bacteria and fungi. They are usually found in low concentrations and asso ciated with non-living dusts in the air. 1. Bacteria. One of the most im portant is the anthrax bacillus, which is found m the dasts from slant, furs, wool, and animal hair, horns, hoofs, bones, etc. Diphtheria, tuberculosis, typhoid and other bacillus-produced diseases may result . from exposure to infected dusts. Bac- J terial-sensitized dust can also be the -j cause of allergic diseases, as asthma, hay fever, cctema, migraine headaches, etc. 2. Fungi Dusts containing parasitic fungi may cause annoyance and discom fort. Xiould on straw, hay, grass, vege table debris n typical of this type of dust. C Inorganic Dusts These are of mineral origin not re quiring a firing organism to produce them, Many dusts not classed as toxic come under tins classification. Classified under inorganic are tone and/or irritant, fibrosis-producing and non-fibrosis-produang dusts. t. Toxic and/or Irritant. These arc inherently tome when inhaled, ingested or otherwise absorbed. Among them are the dusts from heavy metals and their compounds, such as lead, mercury, arsenic, cadmium, zinc. industrial dust 2. F tbrons - Producing Dusts. The moil important of these are the inor ganic. slightly soluble dusts, which cause sbrnsu in the lungs, o f which quartz is Ihe outstanding example. J .Von - Fibre t it - Producing Dusts These arc inert, and by themselves sel dom ti ever cause fibrous tissue, but may lie tree m the tissues or be absorbed. Included arc aluminum oxide, coal, corundum, emery, limestone, magnetite, marble, plaster paris, polish o f rouge, etc. The Respiratory System Retention of Dust 17. In the human respiratory sys tem, there are complicated moist pass ages, on the walls of which dust particles will suck. Also, the nose contains hairs which catch some dust. However, the respiratory system can become over loaded with dust, and when this hap pens, the dust catching mechanism functions poorly. 18. C E. Brown has estimated the average amount of dust a normal man will retain. Breathing a t the rate of 20 respirations a minute, for example, he will inhale about 10 liters a minute and retain 60 per cent of the inspired d u st It is estimated roughly th a t the reten- sn of common silica dust is about 50 per cent, but the way this dust may be divided between the upper and lower respiratory passages has not been clear ly defined. Drinker has observed in the case of metal fume fever th at slow, deep breathing, possibly five or six breaths a minute, is much more likely to produce a fever than the normal rate of about 15 breaths a minute. T his is supposed ly due to the higher retendon of dust re sulting from deep breathing. However, we cannot select by any known exami nation the men best suited to dust ex posure, although some men show them selves obviously unfitted for dusty at mospheres. 19. The way in which dust panicles are removed from the respiratory tract has been described by Dr. A. E. Barclay, British specialist on X-ray. The bronchi or respiratory passages, are covered with a number of tiny, hairlike cilia or mi croscopic whip lashes. These cilia make a fast stroke in one direction and a slower return stroke. They cover the passages leading to the lungs, and all eep in Ume with each other. This tends j push any foreign particles of dust up ward in the direction in which the cilia bend, so that the particles may be ex pectorated. Dust particles which reach the inner recesses of the lungs are also removed by means of dust valves (phagocytes) which ingest the dust par ticles and carry them to a system of fine drainage canals called the lymphatics. Both the cells and their contents are transported through these canals to sed imentary reservoirs known as lymph nodes, r- Saes of Particles 20. Microscopic dust particles are, of course, attracted by gravity, but be cause of the high resistance of the air, the smaller dust particles settle out more slowly. The settling motion of a dust particle through still air win vary with the size and shape of the particle. 21. In order that dust particles be inhaled, they must be small enough to float about in the air or be carried by air currents. I t has been shown by research that dust particles must be smaller than 5 microns in diameter to cause silicosis. However, nee all at mospheric dusts include a majority of particles smaller than this size, the par ticle size distribution of dust in the air is of little significance. McCrae showed that 70 per cent of the partides in sili cotic lungs were found to be less than one micron and that the largest partides did not exceed 10J microns in their greatest dimensions. Results since ob tained by other investigators have served to substantiate this comparative ly early statement. 22. In silicotic lungs, dust particles under 3 microns greatly outnumber those of larger dimensions- Some have be lieved that the human respiratory mechanism is responsible for this size grading. I t must be realised, however, that considerable size grading fa done in the air before the dost comes into con tact with the respiratory organs. An excess of m a ll partides may be found in the lungs simply because smaller partides remain suspended longer and in greater amounts. Particles above five microns will not remain floating in the air for any great length of time. The air cells of the lungs are large enough to admit partides possibly up to 200 mi crons in length. However, according to G ark and Drinker, the most represen tative particle size in the lungs of men who have died of silicosis is one micron. 22a. Fine asbestos dust particles have been shown to produce only the inert reaction on the lungs characteris tics of other silicate dusts. It is. con sequently, believed that the asbestos Fipire 4. Ground silica dumped onto the apron of a conveyor. Nou ebe en closed conveyor cxbaust bood and die use of an approved respirator by tbc operator. fibers are the cause of the physical irri tation resulting in asbestosfa. 25. T b e ' ftner partides7of dust re-'main stspehded'ih a stillatmosphere for relatively long periods of^tupe. Their chances of being inhaled a^^ h erefo re, greatly Increased.ThenrriaBerdujt par ticles also travel farther sway from.their point of origin, and kasuwdF as the larger particles settle out-very quickly, th e farther away from the'dosraoerce, th e greater wflj be the percentage of ' smaller partides. 24. Neither upper nor lower size limits have been suggested for toxic sub stances, as lead, etc It fa the opinion of Drinker and Hatch that no physio logical size limits exist for these sub stances. Silicosis 25: Undoubtedly the most important kind of lung disease caused by the in halation of dust fa that which has been named "silicosis." Definition 26. Dr. Gardner's definition of sili cosis fa as follows: "Sificosfa fa a chronic disease of the lungs resulting from pro longed inhalation of fine particulate sil ica. It fa manifested anatomically by formation of sharply defined fibrous nodules not over four to six mm. in di ameter, which in most cases are uniform ly distributed throughout all portions of both lungs; and dinically by a paucity of symptoms and physical signs that usually appear only in the late stages of the disease and by a tendency to be come complicated by tuberculosis. In some cases, nodulatioo fa concentrated in certain parts of tbc lungs, in which cases symptoms may be marked." 27. The International Silicosis Con ference in 1910 defined silicosis as a industrial dust cate dusts are inert and do not cause the characteristic nodulation produced ~ rby free silica. In addition to the animal experimentation, men who are exposed to silicate dusts containing no tree silica have been x-rayed, and in a number oi cases there has been opportunity for examination of their lungs. The nodular appearance on the x-ray and the actual nodules on the lungs, both of which are characteristic of silicosis, have not been found when exposure has been limited to silicates. Gardner has stated that evidence so far available indicate that, where a disabling lung condition is alleged to result from exposures to sili cate dusts (other than asbestos), there is either an unsuspected presence of free silica in the dust, the victim has had a previous undisclosed exposure to free silica dust, or there has been inadequate interpretation of the x-ray. On the other hand, Dreeson et al. have reported pneumoconiosis in workers exposed to high concentrations (150 million par ticles per cubic foot of air) of dean washed mica. Greenburg and his co workers found fibrosis associated with such symptoms as dyspnea and chronic ycough in 14.5% of 221 tremolite talc Asbestosis miners and millers. These men were 38. Asbestos is the only silicate at all employees of 10 o r more years ex present recognized as causing pathology, posure and the reported dust concentra and even its reaction is definitdy differ tions are as high as 1300 million par- ent from that due to silica alone (Drink tid es per cubic foot of air. In two er). Its behavior is the exception to the mines in this area, Gardner had found rule that silicates are inert, at least in quarts ranging from 12 to 20 per cent, uninfected tissues. Asbestos, when in- but in the mills, where all rock is mixed halid, produces fibrous tissues m the and crushed, the dust showed low quartz lungs of both men and animals As percentages both in Gardner's studies bestos is made up of hydrated silicates and those of Greenburg. This subject of magnesium with variable amounts of of the possible action of silicate dust iron, calcium, sodium, potassium, and on the lung tissue is being further in aluminum replacing portions of the mag vestigated, and any indications that nesium. The property common to all certain silicate dusts m ay be causing a of this group is the fibrous structure. disabling lung condition should be It has been shown that the presence of given thorough study before condusions fibers of asbestos are necessary for the are reached. production of asbestosis and this fact, coupled with the observation that fine Mixed Dusts 37a. Where free silica is mixed with other dust, the greater the percentage of free silica, the less the dust exposure required to cause silicosis. Since some dusts such as gypsum have an inhibit ing effect, there is an increasing tend- asbestos dust is analogous in its inert reaction on the lungs lo that of other silicate dusts leads to the conclusion that asbestosis is the result of physical irritation of the lung tissue and not of chemical action as in the case of sili cosis. \ ency to evaluate the extent of the 39. Following a stu d y by The hazard presented by mixed dust on the United States Public Health Service of basis of the individual dust exposure. the asbestos textile industry, it has been More data are constantly being ac recommended that the dust concentra cumulated on the actual effects of vari tion be kept at les- than > million par- ous types of mixed dusts. kk tides |rr cubic n>( of air if is to be avoided. The use of a standard based on the number of fine particles result from the use of dust determina tion technique developed for the study of silica dust exposures. Although fu ture research will undoubtedly set up a standard based on' the number of as bestos fibers in air, keeping the fine dust at less than the suggested standard will keep the concentration of injurious fibers within safe limits. Infection 40. In the opinion of most investi gators, the factor of infection is most important It has been observed in guinea pigs with chronic pneumonia that in an infected area which developed before exposure to dust, the local broaches of the lymphatic system were not so effirient as those in the rest of the lung. Silica inhaled into tissue thus damaged appeared to accumulate in un usual amounts. 41.. Since men with silicosis are more susceptible to tuberculosis than are normal men. there is often an excessive Incidence of tuberculosis among such workers. Usually disability and death of a silicotic, tvben due to pulmonary conditions, results from the complicat ing tuberculosis. For this reason, it is especially important to have a re-em- 4 H.r.j\-< uiLu.rn / am< //< y..i /.i.w///v./.y n o . 4 "pathological conditioa oi the lungs due .0 the inhalation of free silica (SiO})." Other authorities have given various definitions. That given by the American Public Health Association includes the following the 'Ct'Oitd lacr n o ; n tlx vietim ha* Jeen removed f r<im tin- <hi*iv atmosphere Her e labored breathing hecome* -c v rr r and the injitrrii jT*nn i> susceptible !< pulmonar\ tril-rmilr*.. frequctuU with fatal re>nu> The v.ork cosis, in the opinion of the Saranac Sili cosis Symposium, are not disabled and are not a menace to their fellow em- r1 plovees. The fact that barely percepti- \ ble X-ray change is visible is not statement that silicosis is "a disease due to breathing air containing silica." Say t r is nw far belo* tonnai. blc victim t respiratory 4 jw.vo. grounds (or assuming disability, since most persons over 40 show some chest ers and Jones at the Saranac Symposium on Silicosis in 1935 stated that, "From the viewpoint of etiology, the harmfulness of a given dust containing free sil ica Is directly influenced by the number of particles of free silica less than 10 microns in diameter that it contains." 31. Silicosis may be detected b> X--changes regardless of dust inhalation. ray in each of the three stages. How Action of Silica on the Luogs ever, X-ray appearances alone are not sufficient for a diagnosis of silicosis. The 35. The theory of the action of silica complete occupational and medical his on the lungs is as follows: Where quartz tory of the employee should be care dust is inhaled and is passed through the fully evaluated and related to the X-ray upper respiratory tract, it reaches the Factors of Influence findings before a conclusion is reached. terminal air sacs of the lungs where the exchange of gases between the blood and 28. Silicosis becomes noticeable after air takes place. At this point, as the widely differing periods of exposure to dust is a foreign matter, it is ingested silica dust, apparently depending on: by what are known as "scavenger" cells a. The amount of dust inhaled, h. The percentage of free silica con tained therein. which carry it through the walls of the air sacs to the lymph drainage canals located outside the air sacs. This re c. The site frequency, or fineness of the particles inhaled. <L Tltc nature and source of such other substances (including vapors and gases) as may be inhaled simultane ously or otherwise. e. The powers of resistance of the indi vidual concerned. sults in a rapid increase of tissue cells which narrows the lymphatic channel, hampering elimination, as it is along these canals that foreign substances are removed. Abo, when silica b bring re moved, the panicle may kill the scaven ger cell by which it is being transported, f. The presence or absence of a compli cation by an infective process. C- The presence of complicating condi tions such as high temperatures or humidity, and unfavorable postures. Figure I. An automatic bag loader han dling finely powdered silica dust. An effective local exhaust system is in oper ation. with the result that all dust panides are not removed from the hmg. Instead, f they may remain along the course of the drainage canal. Apparently, these small partides of silica dust are toxic in this Physiological Effects 29. In earlier years it was believed that the physiological action of quartz on the lungs was caused by the hantnose of the material. In fact, it was dvinwi that men who worked on sandstone were harmed not only by the silica particles, but also by sharp bits of steel These ideas were contradicted by D r. L. U. Gardner, of Saranac Laboratory, who showed that silicon carbide and fused aluminum oxide, both of which are harder than quartz, had practically neg ative physiological effects when inhaled. Dr. Gardner also showed that dust from the diamond, the hardest substance known, was practically inert when in haled. 32. From most industrial exjwrience the development of silicosis may not be anticipated short of five years. A few cases have been claimed to develop in as short a period as one and one-half years, but these were under extreme and un usual conditions. There has been evi dence that alkaline materials, such as soap powder, accelerate the develop ment of silicosis, but this has not been substantiated in recent experience. 33. Silicosis is a disease of which the victim may be unaware in the early stages. Its development is usually slow and unperceived. Inasmuch as silicosis cannot be cured by any means ve: known and in its advanced stages is frequently complicated by tuberculosis location and the tissue celb in the im mediate vicinity are altered and re placed by what b known as scar or fibrous tissue. The ultimate result is larger areas of tissue or hmg volumes in which capillary action b definitely re duced-- through which a normal ex change of p v * between the blood and inhaled air cannot take place. 36. As the inhihtion of shea con tinues, the amount of fibrous tissue wOl, of course, increase, with the ultimate re sult that the lungs will not readily oxy genate sufficient blood for the. body need. This produces a shortness of breath in the affected individual in pro portion to the amount of scar tissue in his lungs. 30. Silicosis is considered in three separate stages by medical authorities: First Stage: The diseare here produces r*o dtMbiiitv and doc; no apprccii* We harm. The affected man can carry on hU operations as well as ever. Second Stage: Respiration is affected. The victim may be bothered by labored breathing. 'Third Stage : Tl< <tage may develop or other infections, the importance of Free- Silica vs. Silicates prevention is apparent. Also, in many 37. With the exception of asbestos!, industries, new developments have the silicate dusts have not been shown greatly increased the dust output In to cause a disabling lung condition such granite stone cutting, for instance, and as is produced by free silica. Experi- ^ in rock drilling, dust production in ments conducted both by causing ani- creased tremendously with the introduc..... mab to inhale dust over a long period tion o.f pneumatic tools. ^ * S f time and bv injecting dust in their 34 M e n w i t h e a r l v first StaiM peritoneal tissue have shown that sili o t h e r c o m p o n e n t s of ce m e n t null Just seem to h jv e p ro tected all other p e r sons similarly exposed, these isolated imJtviduAU app.'trctitty reacted In com e I u l t n ONi l . t l 11 M. ^ j M. ' l l i l . t f ( l l l r l l l k i Alihom:* *i Wii*.n 111a t | . r . . u i i i \ c actio I ' i u i m c ' k** i t c c ti\c a* the relativ e a n n . t i n t s <! ilu.a in the diiAt in c re a se , th e l i m i ts <i t o le r a tio n havf not been defined. Therefore, the limit f o r silica particle. lc<* t h a n 10 m ic r o n s in d i a m e t e r at t h e b r e a t h i n g /m- was a rh itra rilv set at five m ilium particle per cubic font of air a* determ ined by the L'niu-il S ta te s Public Hralili S v f ,ir<* t a n d a r d licit! field c'auii.** T oxic Dusts .Breathing vs. Swallowing 52. Generally, workers may be poi soned by toxic dusts much more quickly through inhaling them than by swallowing them. Dust swallowed with food goes into the stomach from which the major part of it is directly eliminated. Some may be picked up in the blood cir culation and then moved on to the liver. The liver, however, is an effective filter and detoxifier, and it is only the poison that gets beyond this point that enters general circulation. On the other hand, dusts that reach the lungs can pass di rectly into the blood stream, to the heart and then to all parts of the body. 53. Alice Hamilton, in " Industrial Toxicology" (Macmillan Company) points out the distinction between the two ways in which poisonous dust can be taken into the body in the following paragraph--"A great deal of money has been wasted by well-meaning em ployers who sought to protect lead fur- Figure 8. View in an iron (ounjrv .howinic hen.h uruulir. jMgi&'Sxttou, IN D USTRIAL DUST nacemen, white lead grinders, etc., against poisoning, by providing bath and lunch rooms, clean overalls, mouth ahes, and such, instead of preventing the esca|>e of lead intu the air the men were obliged to breathe. Unfortunately this has sometimes been done under a physician's advice. It must never be forgotten that the great majority of in dustrial poisons enter the body with the inspired air and that while a workman eats only three times a day, he breathes 16 times a minute during the eight or ten hours of the working day." 54. Numerous aulhorides give evi dence that there b far more danger of being poisoned by inhaling toxic dusts than by eating them with food or taking them in liquids. But all precautions should be taken to prevent toxic dusts from entering or even coming into direct contact with the body. Lead 55. The practical problem in con nection with lead poisoning is the pre vention of serious lead exposure. The problem consists of two phases: one, the determination of the Unfits of safe ex posure, (see paragraph 68) and, two, the reduction of lead exposure below these limits. 56. We must recognize however that lead b a normal constituent of a living animal and that there is a level of lead absorption which is safe. Lead intoxi cation and lead absorption can be pre vented by engineering methods. (See Health Practices Pamphlet No. 3 and Safety Instruction Card No. 116 on thb subject.) Metal-Fume Fever 57. Metal-fume fever may be one of ibe results of breathing dust from metal sources. T h b malady usually follows contact with a heavy concentration of magnesium oxide, copper oxide, lead, zinc oxide, and possibly lead oxide and manganese dioxide. SS. The symptoms are chills fol lowed by a malaria-like fever which usu ally passes off within 24 hours, allowing the worker to return to hb job on the following day. The first attack usually immunizes the victim so that attacks are not experienced consecutively. How ever. after a lay-off or an absence from contact with the dust, a further attack is likely. Slow, deep breathing, accord ing to Drinker and Hatch, seems to bring about the symptoms more quickly. H.P.P --- Allergic Diseases 59. Conditions arising from allergic disturbances of an occupational origin are coming more into prominence, from the compensation point of view. 60. Persons said to be allergic are those who are particularly susceptible to certain substance with which they come in contact These substance may in clude foods, drugs, and vapors and dusts of various kinds. A wide variety of substance may, therefore, be responsi ble for allergic reactions in various in dividuals, which substance may have no effect on others or, in some cases, may even be of positive benefit The ty p e of reactions experienced by affected in dividuals to given substance may also vary greatly'both in nature and in de gree. A single substance may, in one case, cause intetinal dbturbance, in another case develop asthmatic attacks, and in a third case cause a skin eruption. Still another person may be affected in all three ways. 61. Dusts of various kinds sometime cause attacks of asthma. Asthma may be suffered by stablemen from exposure to horse dander and by furriers from exposure to fur dust. Other persons cannot work near animals or, in fact, keep pets or sleep on feather pillows without suffering acute attacks. Hay fever b another type of reaction to dust on the part of certain individuals. These dusts are frequently in the nature of pollen, as from plants. Hay fever, it is claimed, however, may also be caused by other types of dust. In any event, the precise manner in which an allergic in dividual may react to a substance to which he has become sensitized cannot be predicted 62. Many believe that allergic in dividuals are horn wjth their particular , 6--H.P.P.-4 HEALTH PRACTICES PAMPHLET NO. 4 ployment and periodic x-ray program among workers exposed to silica dust. 42. Gardner states as follows: "At the present time the treatment of tuber culosis in silicotic subjects is comparable to that for ordinary consumption SO years ago. The prospects are far from hopeless. Silicosis Is gradually being brought under control. The time is not far distant when dangerous concentra tions of silica dust will no longer be per mitted in American industries. Periodic examinations of those already employed will detect new infections in persons now silicotic Prompt- institution of treatment will eliminate 'most of the hopeless cases of silioo-tuberculosis. Pre employment examinations will insure placement of men in positions that they can fill without damage to their health." Coal Mining 43. Anthraco-silicosis is a term used for a form of pneumoconiosis commonly called " miners' asthm a." According to Public Health Bulletin No. 221, "Anthraco-Sncosis Among H ard Coal Min ers," it is a chronic divase due to breathing air containing dust generated in the various processes involved in mining and preparing anthracite coal. It is characterized anatomically by gen eralized fibrotic changes throughout both lungs and with the presence of ex cessive amounts of carbonaceous and siliceous materials. 44. Symptoms found in early stages are shortness of breath, cough, pain in the chest, and possibly physical weak ness. In the advanced stages of the disease there is loss of weight and de creased capacity for work, due partly to pulmonary infection. 45. In studies conducted by the United States Public Health Service in Pennsylvania, no cases of anthracosilicosis were found in the controlled group of hard coal mining employees whose dust exposure averaged less than five million particles per cubic foot of air. However, the prevalence of anthraco-silicosis among the entire group of employees was found to be about 23 per cent. Among all except rock work er*. les< than two per cent of the men were affected when the duration of em ployment was less than 15 years, regard less of the amount of dust in the air. Among rock workers, who were exposed to dust averaging 35 per cent free silica ried from 10 to 72 per cent depending monia, bronenitis and similar physical on length of exposure and dust concen ailments. tration--the higher percentages of in cidence being found among workers ex posed more than 25 years to concentra tions greater than 300 million panicles per cubic foot of air. 49. Also, Dr. Greentjurg reminds us( that there is an important factor o th e r' than the one of environment, which is that of individual susceptibility. In vestigators have noticed that men work- 46. According to A. E. Russell, the ing in the same plant, at the same task disability rate among anthracite miners and in the same work place, frequently from respiratory tuberculosa b about do not develop silicosb to the same de gree. It is possible for one worker to be an early victim, while the man work ing beside him remains comparatively free. T hb angle of the problem indi cates a need for further research. 50. It is well, nevertheless, to con sider all coal mining as involving a risk to some degree, depending upon the type of rock being drilled. While the hazard may not be as severe as in most metal mining operations, it b of importance at least because of the number of work men concerned. 51. The hazard of silicosb seems to be practically absent b the manufacture of cement A recently completed survey Figure 7. A method of receiving dust into trucks and auxiliary collecting equip ment. of 2000 cement plant employees in all sections of Use country by Dr. LeRoy U. Gardner and staff of the Saranac / 4J4 times the rate for general manufac turing. The pneumonia rate b less than one-third of general manufacturing. Bronchitis, however, b a rather common complaint Laboratory for the Study of Tuberculo- V sis, has failed to demonstrate that the inhalation of cement plant or quarry dust has a significant effect on the res piratory tra c t Neither did it appear that men who had spent their industrial 47. S. L. Cummins and S. F. Sladden lives in suds atmospheres were unusu conducted an examination of a large ally susceptible to respiratory infection. number of coal miners' lungs in South The incidence of influenza, disabling Wales. As a result, they made the colds and pneumonia was not high. No statement--"Coal b retained in large n w of dinks] tuberculosa were db- amounts only when there b a really high covered, and the inddence of healed or silica content" They added, "We be latent foti as revealed in the roentgeno lieve that in the absence of the silica grams b the o n * as that found b the factor, there would be, under modern general adult population; namely, 4.5 to mining conditions, no serious degree of 5 per cent. Dr. Gardner has stated: anthracosis." E. L. Collins and J. C. Gilchrist have claimed that workers who "Although the medical examinations re veal no evidence of respiratory injury have had considerable exposure in trim ming coal ships where there is practi cally no siiica exposure, but nevertheless a verv heavy dust condition, showed some fibrosb which, however, was not considered disabling. 4S. A stutlv of 2500 |>o>t-mortein from cement plant dust, even after ie- riods of long exposure, maximum con centrations m dusty areas should be re duced to 100 million particles per cubic foot (light field count, impingcr tech nique) as rapidly as economically feasi ble. High concentrations may not be dangerous, but they are not roni|atihl<with good housekeeping sutubrds. examinations made in I'iit.-burgh hos pitals shows that city air which may contain an unusually large amount of coal dust may cause lungs to become darkly pigmented-but vet produce no*' pathology of importance other than per- "An exception to the general rule > indicated by the discovery of two cavc> . of non-clinical dust reaction in this \ group of 2,000 persons. These men had been exposed to quant dust (usu ally in the form of sandstone) used in the manufacture of special cement. possible to apply tlie knowledge in a practical manner." Iy DUSTRIAL DUST .Manganese: 50 mp. per cubic meter is safe (Drinker A Hatch). H I' 1' .i-- 68. Other threshold limits for spe cific dusts have been stated as follows: Asbestos--( Drecsscn, et al. United Slates Puhlie Health Service) five mil lion particles per cu. ft. Coal dust--( R. R. Sayers, et al.) 50.000.000 particles per cubic foot for coal dust containing not over 5% quartz. 10.000.000 to 15,000,000 particles for dust with 1.1% quartz, and 5,000.000 to 10.000.000 particles for hard rock workers exposed to dust containing 85% free silica. Lead--(Legge and Duckering) more than .5 mg. per cubic meter is hazar dous and (A. E. Russell et aL), less than .15 mg. per cubic meter is safe. Zinc oxide--(P. Drinker, et al.) 14 mgs. of zinc oxide per cubic meter for 8 hours of exposure or 45 mgs. for short exposures. 69. Of the metals, the following suggestions have been made: The American Public Health Associa tion Committee on Lead Poisoning state in tlietr comprehensive 1943 Report that "when the air of workrooms regularly contains more than 18 milligrams of lead |rfr 10 cubic meters of air, cases of dis abling lead intoxication do not occur among mm who work regularly in surli workroom, and cases of questionable or minor intoxication are rare. In practice the attempt is made to maintain the lead content of the air within such limits a< will yield an average of not more than 18 milligrams of lead per 10 cubic meters throughout the working day. while pre vailing the occurrence of materially higher concentrations (5 milligrams per 10 cubic meters or more)." Zinc Oxide: To avoid metal fume fever the concentration should be kept below 14 mg. per cubic meter for 8 hours' exposure or 48 mg. for short ex posures (P. Drinker et aL). Control of Dustiness 70. There are various ways in which dust diseases and annoyances may be Tvoided*: 1. The avoidance of exposure ftirnilic* the first and most important iktcnse against industrial disease. Jl> should be performed in clean air far as possible. It is not necessary, however, to prohibit al) exposure to a toxic substance, as the human sys tem can protect and cleanse itself to a certain degree. 2. Exposure can be limited by reduc ing working hours where dust con centrations cannot be sufficiently re duced to constitute an otherwise safe condition. 3. Safe processes may sometimes be substituted for those of an unsafe nature. An example of this is the substitution of abrasive wheels made from synthetic abrasives con taining no quartz, for wheels made from natural sandstone, which is about 95 per cent quartz. 4. The substitution of wet methods for original dry methods has ex erted considerable control over dusty atmospheres. Dry drilling is the cause of considerable dustiness in mining, which may be greatly re duced by wet drilling. This is also true in many construction and quarry jobs. 5. An effective method for preventing the escape of undesirable dust into the working atmosphere is the local exhaust hood. It should be placed close to the source of pollution to he most effective. The atr should he discharged through a dust col lector to prevent contamination of neighboring areas or return of the dust through open windows into the plant 6. The routine recording of dusty con centrations is a valuable check on the existing exposure. Periodical counts of air samples are a great help in showing whether or not there is need for further control. 7. In some cases, the application of general rather than local exhaust ventilation is desirable. There are instances where the source of pol luting materials is constantly chang ing position and local exhaust be comes difficult and impracticable. Here a general ventilating system may be the only answer. *Tb sight methods o( prevention given her# are listed In this order In "Industrial Medi cine" by Clark and Drinker, published by the National Mrdlral Bonk Company. Inc.. N-w Tork. N. T. Figure 14. C Jurteey. K irk and Blum M anufacturing Company Adjustable exhaust hoods for polishing wheels. 8. A final-method of protection is the wearing of special protective equip ment by workers. This step is fre quently the last resort and is used only in an em ergency o r for jobs of short duration, but it is never theless rf considerable importance. (See American Standard Safcty Code for the Protection of Heads, Eyes anil Respiratory Organs.) 71. In many localities codes or or dinances for the control of dustiness are in effect which should be investigated and followed by employers seeking to improve working conditions. Local Exhaust Systems 72. Local exhaust ventilation for the control of industrial dusts and fumes consists of four principal .parts: a. Exhaust hoods i. Piping or duels c. Atr cleaning plant d. Source of suction 73. While each of these parts should be designed and installed to perform its required function with respect to the system as a whole, the exhaust hood probably demands the most careful de sign, inasmuch as the degree of control secured depends to a larger extent upon the shape and location of the hood--and the rate of air flow to it--than upon any other single factor. 74. Hoods have to a considerable ex tent followed the design first employed in such industries as woodworking and metal grinding. However, as noted My Theodore Hatch, in recent years the in dustrial dust problem Ha.< assumed h y gienic and economic aspects entirely be yond the limitations of those indu-iriein which the ]irnluriii>n ui dust-ha-; hem 8- -H I' !' - HE A LT H /'AM( /7( 7-..\ rA Ml Tl EE T NO. 4 be told that the maintenance of certain degrees of air cleanliness represent? the best known practice. Moreover, while >uch standards would undoubtedly be o value for a single indu>n-v,'under differ ent conditions and in other industriethere would be a question of their appli cability. 65. As the result of many years-cpractical experience in dust control in the South African gold mines, a concen tration of one mg. of dust (>er cubic meter of air was accepted as standard and is now known commonly as "the South African standard." In 19.1-. I. G. Irvine stated that no miner who had entered, the industry since this low con centration had been maintained had. ayet, contracted silicosis. Figure 10. Portable M usirijl wttium *leaner. type# <ii hy|*rr-;ensitivity. \Vbile this is prob ab ly so. according to Dr. May R. Mayor.-, individuals do not become sen sitive t*j substances which later cause the trouble until they have had sufficient contact to l>ecvrne sensitized. When a person who i- h> |>er-sensitive first comes in com ae: with the substance, he is not aware 0 1 h i - condition. An " incubation period i- r. i;.::.-pd. durint; which time repealed acts perhap sensitize him to a wh.-re subsequent contao.- m ay rt-u!' r- :m:n<diaie allergic reac tion I h;- waning criod may vary from a week or two to several months or even However, the allergic tcmlcn. h:i\e lin n in the indi vidual [.. 7 . _-;n with. a n . I then there i m i - i !.e . i *.i: n i - ut i n i . niiuicni con- tit:- -uli-i a m e m i|-.iesuon in oriic-r i!'..r latent alleren lendenev can l.e lir.aieh; nut. !' i'a- ii. .-ii ila n iK .I that ..net a .-uh-tance. he may, more readily than Ik-iure. In-mmc sensitive t<< other sub stance#. Occasionally, t.o, it has been suggested certain individuals are ca|)able of developing a certain degree of im munity as time goes on. However, from the viewjxjint of prevention, it seems logical that workingmen who have be come allergic to certain substances in the C'.ur-e of their occupations should be i-n<otiraged t-> go int> other lines of >.,rk. ;..r in in..-t vase- the 'tr.dency is i.. ln.-i...nti iii..i<- i- i-\(s.-ure .niinue- I'vruiisMlrle D ustiness o- ( . i i . d h , kc 'ack data ior tle:>i n r : :1y | w-rmi--ill t du-utic*- The l-.in; ii.t- -. a Ix eti re.t hed In re a manuiaaure- can lie told the exact concen tration- at which, (or in-tama-, his men will -lari de eloping ca-c- >>( -ilicn-is, as1 .. .. i. .i,i i.i.,,n,n; H.-i an only 66. It was slated by l). E. Cum mings in a paper presented at the Second Symposium on Silicosis at Sar anac Lake-- . . Information from field studies made in many parts of the world indi cated that a normal man might work in pure crystalline silica dust lor manv years without impairing his health if the concentration did not exceed five million particles per cubic foot of air." 67. Dr. L. U. Gardner states, con cerning the permissible dustiness where silica is present: "The evidence now available make- it seem improbable that a silica hazard is defined solely by the number and size of the silica panicles in industrial atmospheres. The other components of a dust modify its action. Some mav inhibit. others retard, and perhaps tome will be found to prevent its injurious effect. Because these possibil ities are rccognixed. it becomes diffi cult to set up definite standards of per missible dustiness in industrial atmos pheres. Dr. Gardner continues further: "Not enough is known about the ac tion of protector substances to warrant the recommendation that they be em ployed to prevent silicosis in industry Our aim should be to reduce existinc dust concentrations rather than to in crease them by adding more dust. I would very strongly oppose the recom mendation that protector dust be use-: to attempt to prevent silicosis at tli> present time. But I do believe that w should attempt to discover more alx-wtheir action. Sm. tit* gypsum, sect to combine with silica in the atmophcrc, forming clumps which are toheavy to remain suspended in air an too iarge to pass the barriers of ti se and upper respiratory tracts. Wn such information at hand, it nia- 1 INDUSTRIAL DUST H.P.P.---- "This meant, in effect, that dry drill ing can only be used with local exItautta and adequate air cleaning. It happens, also, that wet drilling without ventilation will not achieve adequate air cleanliness in the case of the high quarta or class 2 rock." 80. T he situation is well summed^tp in an editorial th at appeared in "Chem ical Engineering and Mining Review" (M elbourne). "W hatever the ultimate findings as to the cause and development of pneu moconiosis, the task of the mining en gineer is indicated elearly: the first es sential is to minimize the formation of dust, and the second is to collect or remove unavoidable dust as rapidly as possible. In this latter respect, a logi cal forward step has been taken in the adoption of means to collect the dost at certain points of production instead of relying: upon the general ventilation carrent to dilute and transport the in jurious material. Small units are now being installed in some mines at load ing stations and orepass tipplers, the installation and maintenance costs of which are low and a high efficiency is developed. "More efficient rock drilling practice, an improved general standard of health, reduced working hours, provi sion of change house and other facili ties. and many minor but important factors can also contribute to `a reduc tion in the incidence of silicosis." ACKNO W LED G M ENT. This pamphlet teas prepared b y Warrat A. Cook, Division oj Industrial H y giene and Engineering Research, Zurich General Accident and Liability Insur ance Company, and reviewed by Floyd A. Van A tta, Industrial H ygienist, N a tional Safety C ouncil I t has been re viewed by the Safe Practices Conference Committee, the H ealth Advisory Com mittee, and approved by the Executive Committee of the National Safety Coun cil. In w riting th is pamphlet, th e au thors have reviewed carefully the litera ture already ht the field, and grateful acknowledgment is made to the numer ous publications. T he U nited States Deportment of Labor has contribu: many of the illustrations used here Appreciation is expressed also to others who reviewed and submitted sgestions for the improvement of teark. Outstanding among those ging the pamphlet their personal a ttc tion are: W . T . Cameron, United Stc. Department of Labor; A. J. R^Csert. Portland Cement Association; Phi. Drinker, Harvard University; Dr. L R oy U. Gardner, Saranac Laboratory j. the Study of Tuberculosis; Daniel He rington, United States Bureau of Minee D r. M. H. Kronenberg, Illinois Depar: m a tt of Public Health; Dr. A. J. L ent. Metropolitan li f e Insurance Company D r. Corey P. McCord, Chrysler Corpc ration; Dr. R. R. Saya s , United State Public Health Service; Dr. C. D . Selby C enaol Motors Corporation; R. C Stratton, Travelers Insurance Company and D r. C. E. A. Winslow, Yale Uni versity. Rep. tM-46~WHF