Document LaxEz4ZaQ3R4rKB6yngp21a3

o 3 ; ' Industrial Dust* ~ ^ ' "lime "*"dust" and '"abnormal' condi- 1. The literature ^on hazardous . ef fects of dust is so extensive that no at tempt has been made here to cover the subject in all of its' ramifications, but to assemble only the outstanding data on several of its aspects. This pam phlet is intended for employers, plant safety engineers, personnel managers, and supervisors generally. The subject has been approached from the prevention - This pamphlet is one of more than 150 Safe Practices .and Health Practices Pamphlets. It'is a compilation of experi ence in,cadent prevention from many sources^' If should not be assumed, how ever, that it' includes every' acceptable procedure in.'the field covered. It must not be confused with American Standard safety codes; federal laws; insurance re quirements; state laws, rules and regula tions; and municipal ordinances. ..Addi tional copies of this pamphlet are available. Member price, 35 cents each. Quan tity and non-member prices on request. _ Uon." _The present generaBy^accepted - meaning of the word involves the con- cept merely of "dusted lung.^The kind 'ofdust3hhaled determines'uie" type" of injury noted in. the lungs. However, there is' one pathological process which underlies lung disease caused by dust. Ibis consists of a fibrosis Vr' a*replace ment of the elastic tissue'of the lungs by an impervious scar tisstie.^.^- ^^i, 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. ` Physiological Effects of Dust 2. The inhalation of dust may pro duce different types of reactions in hu man beings: ' ;v a. Pneumoconioses (silicosis and asbestosis) which result in specific lung pathology. . , . 2a. Silicosis increases susceptibility to , tuberculosis. x; / of (Usability. *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 by such dusts as lime and chromium compounds. * 1......... Pneumoconiosis 5. Zenker applied the name "pneu* monoconiosis" to the various changes in the lungs caused by the inhalation of dust. The term has now been shortened to "pneumoconiosis." It represents .. 6r Research on pneumoconioses has been carried on in the Nortlf American -continent more actively in-l.the. past decade than in' any other period. ..The hysteria with regard to silicosis and other occupational diseases has now largely subsided, and the subject U be ing more carefully considered'and more soberly judged.' .. .v 'SJvji- 1 The Problem - v.- :.v 7. Modem manufacturing methods are, in many instances, creating consid erable dust. Much of this dust is often released in the immediate area where men or women are working, and this fact compels a practical solution of the problem. .. b. The systemic reaction caused by such three words from the Greek, which mean toxic dusts as lead, radium, man : : 'r~~" ' ' 8. The first step in the prevention of ganese, cadmium and mercury com pounds, when either breathed or ^swallowed or possibly absorbed through the skin. c. A transient disorder loiown as metal . fume fever, from. the inhalation of finely divided metallic dust or fume particles such as zinc oxide. injury to health by dust is the control of its concentration so that workers will not be exposed 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 <L 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-producing dust .i'-such.as coal, emery,Jimestone, marble. . and amounts of dust to which workers are exposed. ,V> Origin and Properties '*3. In each of'the above cases, the Inhalation of dust can be the sole cause Figure 1. Dun counting by standard .._-<i. ; light field methods. . ................. ... -* ,tf 9: Dust is formed by reducing solid inaterials to small sizes. Processes like X&opyright, 1929, 1939, National Safety Council, Inc. All rights reserved. Printed in U. S. A. TX TINER RHC0022761 . " - -.'oils fuels--coal, on," wio^ : tai_n_sj_d_r_o_p_le_ts_a.tst. i_. -"of a motor car burning gasoline contain- Tobacco, for instance, smoke composed lets. The particle is about 0.25 microns. .... ., . ... . make-up of the dust are'the deciding " 11. When a solid is broken into fine- factors in determining its" injurious y-.y : .ly. divided particles and released in the properties. It has been shown that sfii-" . air, one of the important changes that con dioxide (free silica) in the form of :take place is that the space occupied quartz may produce a disabling fibrosis, by the broken material and also the sur- "whereas little.or no fibrosis'.is produced face areas are increased many times by the equally hard and. sharp cornered from that of the original mass. For ex-~ aluminum itriA* /pmurv^ ample, if one cc. (.061 cu. in.) of quartz is'- crushed into particles one cubic in'size, there will be lO^Jl.OOO,- _ Xie^^^fdlowing' classification" of .000,000,000 or one "'trillion)`'`particles " V .with total surface areas of; six square. ' -r meters (9300 sq. in.) as'compared with six square centimeters (.930 sq. in.) for , . the original block. If we assume a dust .-' .'toncentration of 100 million particles to i, . . each cubic foot of air, the one. cc. of * material will occupy an air space of- 10,000 cubic feet toim U.'V L_ With the exception_ of such fi-v..,,3 '.bfous material as asbestos, the. dust par- tides must be smaller than. 10^microns ' -y.y\r (one micron equals one'ft 4 -' ' - ;.cnh... - ;'y '-^^3 These are of mineraL'cngm not re-" quiring a living organism^tp^produce ' titem. "Many dusts notc!asscd_asjbxic'^' '*%; come under this classification.^Classified under inorganic are toxic and/or irritant, fibrosis-producing and 'hoa-fibrosis-pr- oxic and/orlfi?far^-^Xbcse are . inherently toxic when .tilled/ingi^<f or otherwise absorbed. rAmong them'are ' ) the dusts from heavy "metals and 'their . compounds, such as~^gjd^.m<^cury, ' arsenic, cadmium, zmc. *_ ^SSV^*.?5K*,s\ - *W^Xe"i * J TX TINER RMC00 2 27 62 Wvc?" . tfreSSfcfc*::''"- afsS^.r:r` > - >v a ''m^NWsTRiA^wsr: w ~3;*?..2,rFibrosis r rrqi\ ^kytrr^aim^re vid"By:'vmeans*"bflfdust ^valves- inm...o.s..t. importan.t....... ...... gpeytesy5whidi'tng^^lie dusVpair ganic, slightly solliljlfcHusts,,wg^jpat^e "~j and 'ca^tii&rto'^system of,fine' . fibrosis in the"limgvoT^hlcli qirnm jj^_j -'` the outstanding _;. .. s:mid%b'; */ Non -Fibrosi?kl'f4'<iuaKgil^buiif.^\ tiiCtKg.- c^3?-:andftheirxontents "are;' `-These are' inert, `ai^by^llhgnsehfes'-sC^.-iU ^^iSed^iSnugii these c^nals'ttTsectr* :jdom if ever cause' fibcpu^'tiaue^Jnit;may lie free, in i.thg ..tissccs* oftibg^b'sorbc^T.3,^ . Included are ^ummacT'o^ade^'"''^ ~ corundum,. emery, '1 marble, plaster pans rff-l&Strw ages, on the walls of wluch dust p^tides will stick. Also, thejiose contains hairs which catch some ddst ^'However, "the respiratory system can Become ' over loaded with dust, and when this hap-; pens, the dust catching mechanism functions poorly. u>' '........ 18. C. E. Brown has estimated the average amount of dust a normal man will retain. Breathing at 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 dust. It is estimated roughly that the reten tion 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 that 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 h minute. This is supposed ly due to the higher retention 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. ' ^ .. '. i;: : T<; 19. The way in which dust particles 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 keep in time with each other. This tends to push any foreign particles of dust up ward in the direction in which the <*iHa bend, so that the particles may be ex pectorated. Dust particles which reach the inner recesses of the lungs are also. ^___ / they must be small" enough '`'^2;<1^efiner partidcs^i^dust re^ afloat about in\the air or becamed ' mhih'suspended in a stillatmbsphere for by'air currents'; ft has been shown by relatively long periods of time.. Their research* that dust particles must'be: chances of being inhaled are/ therefore, smalts than 3 'microns in diameter to ' greatly increased. The smaller dust par- cause 'silicosis: Howeverj since 'all at-'l5*tfcies also travel farther awayrfrom their 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 7Gper cent of the particles in sili cotic lungs "were found 'to be less than one micron and that the largest particles point of origin, and inasmuch'as the larger particles settle out very quickly, the farther away from the dust source, the greater will be the percentage of smaller particles. '-- .V * ..... ,:->> -/y . r24. Neither upper nor lower size limits have been suggested for toxic sub did not exceed 10.5 microns in their stances, as lead, etc. It is the opinion greatest dimensions. Results since ob of Drinker and Hatch thatjmo physio tained by other investigators have logical size limits exist for^these sub served to substantiate this comparative stances. ly early statement. . ' -- :.. . *22. In silicotic lungs, dust particles . V,. Silicosis' ' under 3 microns greatly outnumber those 25. Undoubtedly the most important of. larger dimensions. Some have be kind 6f lung disease caused.by the in lieved that the human respiratory halation of dust is that which has been mechanism is responsible for this size named "silicosis." ^ , , . grading. It must be realized, however, that considerable size grading is done in the air before the dust comes into con Definition ,, '.-* - '26. Dr. Gardner's definition of sili tact with the respiratory organs. An cosis is as follows: "Silicosis is a chronic excess of small particles may be found r|jgasg of the lungs resulting from pro in the lungs simply because smaller par longed inhalation of fine particulate sil ticles remain suspended longer and in ica. It is manifested anatomically by greater amounts. Particles above five formation of sharply defined fibrous microns will not remain floating in the nodules not over four to sixjnm. in di air for any great length of time. The ameter, which in most cases'are uniform air cells of the lungs are large enough to ly distributed throughout alf portions of admit particles possibly up to 200 mi both lungs; and clinically by a paucity crons in length. However, according to of - symptoms and physical 'signs tba Clark and Drinker, the most represen usually appear only in the late stage tative particle size in the lungs of men of the disease and by a tendency to be who have died of silicosis is one micron. come complicated by tuberculosis. In ' .f2a...Fme asbestos dust particles have Joeen shown to produce only the inert reaction on the lungs characterise some cases, nodulation is concentrated in certain parts of the lungs^ in which raze* symptoms may be marked." tics of other silicate dusts. It is, con ^27. The International Silicosis Con sequently, believed that the asbestos ference in 1930 defined silicosis as a PC 3^ OX o O >-3 N> l-l N) Z -i n o\ ?d co . : >>. . on Silicosis' m 1935 &te3 that,J`From the viewpoint of" etiology, tte! harmful ness 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 c_ontains." complete^ocCTipational and medical his- on theTungs'Is as follows:*\vhere quartz* tory 'of the employee* should be dust is inhaled and is passb^i^cough'thi^ 7uUy e-raluated'and r^atedVihe X:ray''*`i5^^P^ory^tract,''`|^^es/jtl^^ Factors of Inffllunepnnc,,e ' 'Vj-c4 ' ' hidings before a*~condusion is reached, terminal air sacs of the limgs^where the TX TINER *v ' R M C 0 0 2 2 T 6 4 2 S. Silicos-iUs becomes noticeable oafftte-r widely differing periods of exposure to silica dust, apparently depending on: a. The amount of dust inhaled. b. The percentage of free silica con tained therein. c. The size frequency, or fineness of the particles inhaled. ;>!". *' d. The nature and source of such other substances (including vapors and gases) as may be inhaled simultane ously or otherwise. c. The powers.of resistance of the indi vidual concerned. . f. The presence or absence of a compli cation by an infective process. g- The presence of complicating condi tions such as high temperatures or humidity, and unfavorable postures. Physiological Effects 29. In earlier years it was believed that the physiological action of quartz on the lungs was caused by the hardness of the material. In fact, it was claimed 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 Dr. 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. '' 30. Silicosis is considered in three separate stages by medical authorities: First Stage: The disease here pro duces no disability and does no apprecia. ble harm. The affected man can carry on his operations as well as ever. Second Stage: Respiration is affected. The victim may be bothered by labored breathing. r, V . Third Stage: This stage may develop -c. :-------- _ --' ^ **' "-a(rVafeW plana ""`At this" pnin>t' aq'the ' Tigure 5. An automatic bag loader han dling finely powdered silica dust An effective local exhaust system is in oper ation. 32. From most industrial experience 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 yet known and in its advanced stages is frequently complicated by tuberculosis or other infections, the importance of prevention is apparent. Also, in many industries, new developments have greatly increased the dust output. In granite stone cutting, for instance, and in rock drilling, dust production increased tremendously with the introduc tion of pneumatic tools* 34. Men with early first stage sili- dust' isl'aTforeign*matter, it'.is'ingested'1 by what are known as "scavenger" cells which carry 'it. through 'the walls of the air'sacs to'the lymph drainage canals located outside the air sacs." This re sults in a rapid increase'of.tissue cells which narrows the lymphatic. channel, hampering elimination, asT ituis. along these canals that foreign substances are removed. Also, when silica W'being re moved, the particle may kill the scaven ger cell by which it is being transported, with the result that all dust particles are not removed from the lung.' Instead, they may remain along the course of the drainage canal. Apparently,"these small particles of silica dust are'toxic in this location and the tissue cells in the im mediate vicinity are altered ' and re placed by what is known as scar or fibrous tissue. The ultimate .result is larger areas of tissue or lung volumes in which capillary action is definitely re duced-- through which a'normal ex change of gases between the blood and inhaled air cannot take place. - ,,V 36. As the inhalation of silica con tinues, the amount of fibrous tissue will, 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. . Free Silica vs. Silicates *~ % /< 37. With the exception of asbestosis, the silicate dusts have not been shown to cause a disabling lung condition such a"s i1s5 pFrodjucecdu fbyy. flrVe~e Js3-1ilica,, . Exp^e1r*im"ts. ""?"fted both by .causing ammals to inhale dust over a tong period of time and by injecting dust in their peritoneal tissues have shown that sili- ; Jv ~wmmm :<~.j;*yc .rtS&- ion proflubecL,._. )*TatmrTaf '% wvce^Qsed^^ lo-tree*silica ^ *numbeV*of'. it 5rtunity. for' 3 ^i.noSiiflar* ^ rance'on'lliCx^^anct t|ie actual. **on^h^llun^^^^^hici are ^ usThave not been ^^en^posur^^s^Jeen limited J- ^StSl^p^x^^^^r^stated'that * ** a*vrvumAr^J "W.it .-*.. * ^t :r-t, r <;.**> [ 'v 'Hi gca LU .result uuui CAjAsauics iu biu* ^^Sts^(oIblr~tEan"asbestos), there jther an unsuspected presence of free ^^in-the! dust,"the. victim has had gugyiqus undisclosed, exposure to free ifcaidust, or there has been inadequate ..iterpretation of:'the x-ray. On the ofiier hand, Dreeson et al. have reported ^pneumoconiosis in workers exposed to ffigh concentrations (ISO million par^M^'per cubic-foot of: air) of clean *^ied'mica.^'Greenburg.and his co- Jounf hbrosis ''associated with ^pfon5'as 'dyspnea and chronic _(Pirtii,4:S1%^of'/22 ltremolite talc a rjers^.and jnfllers.' These men were ^employees of TO or more years ex- jfposure and the reported dust concentra- $'lions are^ as high as 1300 million parfct'ticles 'per' cubic foot of air. In two l^mnes in this area, Gardner had found '.quartz ranging from 12 to 20 per cent, ^ _ but in the mills, where all rock is mixed & and crushed, the dust showed low quartz :< percentages both in Gardner's studies *" and those of Greenburg. This subject . of fhe possible action of silicate dust . on^the lung tissue is being further in- > aad any indications that certain, silicate dusts may be causing a ^^J-jdisabling lung condition should be givm'thorough study before conclusions are reached. Mixed Dusts ^y^j^Jvvj'37a. Where free silica is mixed with f,v^pther dust, the greater the percentage - ' of-free silica, the less the dust exposure ! >"^3: required to cause silicosis. Since some ts such as gypsum have an inhibit- ^ ^ ing^effect, there is an' increasing tend- ency .to evaluate ' the extent of the hazard presented by mixed dust on the ' of individual dust exposure. ; .^^:^fre data are constantly being ac- ^i^.^mulated on the actual effects of vari- - ' .'^^- ous types of mixed dusts. * -i... .*rr7i. -- ,, - . Figure 6.' A tumbling barrel used foj finishing small castings. The barrel is an oper"arrration, but note the absence of dust aue to a good exhaust system." -** ., : Asbestosis % -i.s-r, v.'feto be avoided. The use of a.stahdard 38. Asbestos is the only silicate at based on the cumber of fine particles present recognized as causing pathology, result from the use of dust determina and even its reaction is definitely differ tion technique developed for the' study ent from that due to silica alone (Drink of silica dust exposures. Although fu er) . Its behavior is the exception to the ture research will undoubtedly set up a rule that silicates are inert, at least in standard based on the number of as uninfected tissues. Asbestos, when in bestos fibers in air, keeping the fine haled, produces fibrous tissues in the dust at less than the suggested standard lungs of both men and animals. As will keep the concentration of injurious bestos is made up of hydrated silicates fibers within safe limits. . v j.:. > of magnesium with variable amounts of iron, calcium, sodium, potassium, and Infection aluminum replacing portions of the mag 40. In the opinion of most investi nesium. The property common to all gators, the factor of infection is most of this group is the fibrous structure. important. It has been observed in It has been shown that the presence of guinea pigs with chronic pneumonia fibers of asbestos are necessary for the that in an infected area which developed production of asbestosis and this fact, before exposure to dust, 'the local coupled with the observation that fine branches of the lymphatic system were asbestos dust is analogous in its inert not so efficient as those in the rest of the reaction on the lungs to that of other lung. Silica inhaled into tissue thus silicate dusts leads to the conclusion damaged appeared to accumulate in un that asbestosis is the result of physical irritation of the lung tissue and not of chemical action as in the case of sili cosis. usual amounts. 1' ' ... y-:.i- I---''- '41. Since men with silicosis are more susceptible to tuberculosis than are normal men, there is often ah excessive 39. Following a study by The incidence of tuberculosis among such United States Public Health Service of workers. Usually disability and death the asbestos textile industry, it has been of a silicotic, when due to pulmonary recommended that the dust concentra conditions, results from the'complicat tion be kept at less than S million par ing tuberculosis. For this reason, it is ticles per cubic foot of air if asbestosis especially important to have' a re-erri- X 3 *3 OX o O >-3 fO y* to Z PI cn "X <_n culosis 1^.;!? s'-geahrlffiE^OO''million, pariides -ti&iTB-ejv'jreMfto0fni.4s-iel*aa,1ano^. Aa*l.5embnr/.<pv-oi.-romn tyoea. rtshaatg"of.o-fcmoerdpmroasryi ^Mn.iaurme pfatior'nfroSmO*: ~per investigators have noticed that hopeless...,tSnicosf^Ai'` brought under controf^TWvti^e. k'not ^ far distant when Sangerous^concentra- ^from '"f^iratiTry^tuEercSlosis^is'about do not 'develop slliaisis't^Se tions of silica dust*WflI no longer be ' vgree."'`lt is'possible for on? milted m American industries. t Periodic examinations of those already employed be' an^arlyrvictim,' while . "mg beside him ~remains^co| 4 * will detect new infections in', persons free^JThis angle of Jtke. problem now silicotic. Prompt ^'institution of^ treatment will eliminate" most of' the _1 hopeless cases of silico-tuberculosis. Preemployment examinations will insure ^ placement of men in positions that they can fill without damage to'their health." .. !\; i\ \ . dates a"need for further research**3 ' - iv :? -s-50. ' It is . well, sider all coal mining as involving a r to some degree, depending upon' the type of rock being drilled. While the hazard may not be as severe as' in most metal Coal Mining 43. Anthraco-silicosis is a term used for a form of pneumoconiosis commonly called "miners' asthma."1 According to Public Health Bulletin No. 221, "An- thraco-Silicosis Among Hard Coal Min ers," it is a chronic disease 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 ra^s 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 an thraco-silicosis among the entire group of employees was found to be about 23 per cent. Among all except rock work ers, less 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 the prevalence of anthraco-silicosis va- Figure 7. A method of receiving dust into trucks and auxiliary collecting equip- - mem.. ... * * .' .-V!.' ?: *<? A1/* times the rate for general manufac turing. The pneumonia rate is less than one-third of general manufacturing. Bronchitis, however, is a rather common complaint. .. 47. S. L. Cummins and S. F. Sladden conducted an examination of a large number of coal miners' lungs in South Wales. As a result, they made the statement--"Coal is retained in large amounts only when there is a really high silica content." They added, "We be lieve that in the absence of the silica factor, there would be, under modem mining conditions, no serious degree of anthracosis." E. L. Collins and J. C. Gilchrist have claimed that workers who have had considerable exposure in trim ming coal ships where there is practi cally no silica exposure, but nevertheless a very heavy dust condition, showed some fibrosis which, however, was not considered disabling. 48. A study of 2500 post-mortem examinations made in Pittsburgh hos pitals shows that dty air which may contain an unusually large amount of coal dust may cause lungs to become darkly pigmented but yet produce no pathology of importance other than per haps a predisposition to' colds, pneu- mining"operations, it is of importance at least because of the number of work men concerned. 'vyf;-V . j l --."s^* --!!*. i -t- ;.? 51. The hazard of silicosis seems to be practically absent in the manufacture' of cement. A recently completed survey of .2000 cement plant employees in all sections of the country ,by . Dr. LeRoy U. Gardner and staff of. the Saranac Laboratory for the Study ofTubercuIo- sis, has failed to demonstrate^that the inhalation of cement planter'quarry dust has a significant effect on,the res piratory tract Neither did it appear that men who had spent their industrial lives in such atmospheres were unusu ally susceptible to respiratory infection. The incidence of influenza, disabling colds and pneumonia was not high. No cases of clinical tuberculosis were dis covered, and the incidence of healed or latent foci as revealed in the roentgeno grams is the same as that found in the general adult population; namely, 4.5 to 5 per cent. Dr. Gardner has stated: "Although the medical examinations re veal no evidence of respiratory injury from cement plant dust, even after pe riods of long exposure, maximum con centrations in dusty areas should be re duced to 100 million particles per' cubic foot (light field count, impinger tech nique) as rapidly as economically feasi ble. High concentrations may not be dangerous, but they are not compatible with good housekeeping standards. ` "An exception to the general rule is indicated by the discovery of two cases of . non-clinical dust reaction in this group of 2,000 persons. ..These men had been exposed to quartz dust (usu ally in the form of sandstone) used in the manufacture of "special 'cement. While possible inhibitory 'effects of . . :vS . . . >si-e*r;<-',**; -,n . 33 s^ ax o O *-3 to <-* to Z -J <T> W O i>B6tectnre'l:ilhi __ . c-;as.' `th^^ s$caf:)ijjjthe duij: _____ JoRtoleration, have Inei^T^erefor'e,' the limit' aartfSfesTta'th'an 10 micron? \}OX nSfe^Cf^h'^weatHins^ione was.Tdi ited: ?hFffef<F'count/ :&Cl ^SiA ^gnidcrs, "etc.* --- .d^n^pYerallSj^mputlr aci preventing' air]ffie men' ww^wAfortunate ^tungs'Eeg^one^im'd^ majority, of ______ tbody with the ^aCwhile a wor&nan .e-rs--t'.a-v'cd-aitVhyve]. feieigbrea*t?h' e?7 re- collector-unity mounted. .Jjij'.; ba the rci" "" ` by tbxic"dusts much more quickly jugh inhaling them than by swallow* a^.them. Bust swallowed with food joes^mtd thb stomach from which the ("major part of it is directly eliminated. PSome may be picked up in thejilood drfbulation and then moved on to the liver. _fie fiver, however, is an effective filter ;and detoxifier^and it is only] the poison /.that.`gets beyond this point that enters Jfeenefal circulation. On the other hand, ^dusts'that reach the lungs cari_pass di- from Mitering or even coming contact with .the body. . . v ] *' -/ 7(60. Persons said to be^allergic are V. . /those who are particularly susceptible to tead^ J ri'certain substances with which they come ' The'`practical problem in ron*'v''u contact "These sufcetanceTmay in- detenhinatiqnTpf the limits of safe ex* posure, Tsee paragraph 68) and, two, the .-^Toxicology'' (Macmillan `Company) v: points out the distinction between the / two ways in which poisonous dust can be taken into the body m the following paragraph--"A great deal of money has been wasted by well-meaning em ployers who sought to protect lead fur- recognize lead is 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 this subject.) dividuals to given substances may also vary greatly both in nature and in de gree. A single substance may, in one case, cause intestinal disturbances, 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. . , Metal-Fume Fever '4 7 57. Metal-fume fever may be one of the results of breathing dust from metal sources. This malady usually follows contact with' a heavy concentration of magnesium oxide, copper oxide, lead, zinc oxide, and possibly lead oxide and. manganese dioxide. . 58. 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 his job on the following day. ' The first attack usually immunizes the victim so that attacks are not experienced consecutively. How ever,* after a layoff or an absence from contact with the dust, a further attack Js'likely. Slow, deep breathing, accord- Fnigure 8. Vview in zn iron foundry snhow*- ^ ingv to'Drinker "a*n*"d Hatch, seem~s to mg bench grinders with' exhaust hoods. ; bring about the symptoms more quickly, -: , ' ;X\,. - , ' 61. Dusts of various kinds sometimes 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 3* fever is another type of reaction to dust o* on the part of certain individuals. These S* dusts are frequently in. the nature c* pollen, as from plants. Hay fever, it claimed, however, may also be caused b ss -J p &? other types of dust. In any event, th precise manner in which an allergic in dividual may react to- a substance t which he has become sensitized canno be predicted. v' vr. .*? * v . v ... *^ f ** " 6~~2. -M--a--njy . believe,, th,at, alle-rgic ,in dividuals are bom with their particulai T - " Xx _"*-4 , it 8--* h- jpj..4-4-7-.,--- &3e . tSEALTH p'jiACTlCl MfBLET N0.4\K!,, .......... .... a fe*BU cbl^told.that ttg^maintenance -/degrees of airrieanliness re~ ^bfet^k^wiTpraSiai'^^ ^&jrs^dards^utct^*^. -A^Sue'/o^a'smgle*Industry tent conditions and in* or rthere would be a'question Mmpw%* J^65.;u^tne. result of .jx .`years o7/ ^practicaPexperience in'dust ifroion South Africari'stahdard." 4/In5l934, G. Irvine stated that no miner^who had^ ottered the industry since th& low con- 4 centration had been maintained had, as' ~ yet, Figure 10. portable industrial vacuum cleaner. types of hyper-sensitivity. While this is probably so, according to Dr. May R. Mayers, individuals do not become sen sitive to substances which later cause the trouble until they have had sufficient contact to become sensitized. When a person who is hyper-sensitive first comes in contact with the substance, he is not aware of his condition. An "incubation period" is required, during which time repeated contacts perhaps sensitize him to a point where subsequent contacts may result in immediate allergic reac tion. This waiting period may vary from a week or two to several months or even years. However, the allergic tendency must have been in the indi vidual to begin with, and then there must be continuous or intermittent con tacts with the substance in question in order that the latent allergic tendency can be brought out. :* 63. It has been claimed that once a person has become sensitized to a given substance, he may, more readily than before, become sensitive to other sub stances. Occasionally, too, it has been suggested certain individuals are capable of developing a certain degree of im munity as time goes on. However, from the viewpoint of prevention, it seems logical that workingmen who have be come allergic to certain substances in the course of their occupations should be encouraged to go into other lines of work, for in most cases the tendency is to become more sensitive as exposure continues. - > -i Permissible Dustiness 64. Generally, we lack data for de fining rigidly permissible dustiness. The point has not been reached where a man ufacturer can be told the exact concen trations at which, for instance, his men will start developing cases of silicosis, asbestosis, or lead poisoning. He can only ,,66;. It'-was stated by D. E.. Cum mings tri a paper presented at the Second Symposium on Silicosis ' at Sar: anac Lake-- 'r . . Information from.field stories ' made in many parts of the world indi- eated. that a normal man might work `in pure crystalline silica dust for many .years without impairing his'.health if _ , the concentration did not exceed five 2.1million particles per cubic f-oJtotAti o f< air." I.-- - 67. Dr. L. U. Gardner states, con cerning the permissible dustiness'where silica is present: , 1 "The evidence now available makes ... it seem improbable that a silica hazard is defined solely by the number and size of the silica particles in industrial atmospheres. The other components of a dust modify its action. Some may inhibit, others retard, and perhaps some will be found to prevent its in jurious effect. Because these possibil ities are recognized, it becomes diffi cult to set up definite standards of per missible dustiness in industrial atmos pheres. v - S Dr. Gardner continues fur.ther: .-Ii'\'..* ,, "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 existing dust concentrations rather than to in crease them by adding more dust, I would very strongly oppose the recom mendation that protector dust be used to attempt to prevent silicosis at the present time. But I do believe that we should attempt to discoverimore about their action. Some, like gypsum, seem to combine with silica in the atmos phere, forming clumps which are too heavy to remain suspended in air and too large to pass the barriers of the nose and upper respiratory tracts. With such information at hand, it.snay be . - JSUj /> ,' '. , TX TINER RMC00227 68 rk-And Blum _ Company ' V Zinc oxide--(P. Drinker, et ah) 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: .' * * , , u ' ,,.. , The American Public Health Associa tion Committee on Lead Poisoning state in 'duced to constitute an otherwise . safe condition. ,'v.`"y'-T .> 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- .'V. taming ho quartz, for wheels made 'from natural sandstone, which is " about 95 per cent quartz. ' wearing of special protective equip'``j'Vment by workers. This step is fre- ' quently the last resort and is used '^-r-only in an emergency* or for jobs of short duration, but it is never theless of considerable .importance. (See American Standard. Safety Code for the Protection: bf Heads, Eyes and Respiratory Organs.) . 71. In many localities codes or or v their comprehensive 1943 Report that " "when' the air of workrooms regularly ~ contains more than 1.5 milligrams of lead 'per 10 cubic meters of air, cases of dis- ' abling lead intoxication' do not occur among men who work regularly in such workrooms, and cases of, questionable or minor intoxication are rare.' In practice the attempt is made to maintain die lead t content of the air within such limits as 4. The substitution of'wet methods for original dry methods has exerted 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. dinances for the control. of-dustiness are in'effect which should'bet investigated and followed by employers" seeking, to improve working conditions. '-' Local Exhaust Systems .stvr-'. 72. Local exhaust ventilation for the will yield an average of not more than 1.5 milligrams of lead per 10 cubic meters throughout the working day, while pre venting 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.). ~ 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 \ be most effective. The air should ' be discharged'through a dust col lector to prevent, contamination of neighboring areas or return- of the dust through open windows into the plant control of industrial dusts'and fumes consists of four principal parts: - rj. it . . a. Exhaust hoods V. b. Piping or ducts c. Air cleaning plant d. Source of suction -< htf: 73. While each of these parts should be designed and installed to perform its 6. The routine recording of dusty con- required function with respect to the ' .. centra lions is a valuable check on system as a whole, the eihaust "Sood ** <->v- the existing exposure. Periodical probably demands the most careful de V- .counts of air samples are a great sign, inasmuch as the degree^of control 'v;r.. help in showing whether or not' there is need for further control. , secured depends to a larger^extent upon * *V * . - 1 .. * - the shape and location of tBb^ood--and 7., In some cases, fhe application of the rate of air flow to it:^finupon any ' general rather than local exhaust , ventilation is desirable. There are other single factor. ' - ; instances where the source of pol luting materials is constantly chang- ;~/,ing position and local exhaust becomes difficult and impracticable. Here a' general ventilating system 74. Hoods have to a^cmuKerable ex tent followed the derign ntft employed in such industries as 'woodworking and metal grinding. Howevgg&'noted by v may be the only answer. -.-.v-. .Theodore Hatch, in receji-years the in- Figure V/--.S -- ** iW Courtesy, Kirk and Blum Manufacturing Company 11. Exhaust system for removal of lead dust and fumes. ,, . - - . .%<;y-:--dustrial dust problemjifgfa^sumed by- *Tka eight methods of prevention given here are listea in this order in "industrial Medi cine" by Clark and Drinker, published by the National Medical Book Company, Inc., New ___ York, N. T. , >>. .,S. giehic and economic as yond the limitations.o' in which the production Entirely beJndus tries ust has been ' ' V.' ; . , . * A -4 > ^ TX TINER RMC0022769 f '.-T^-r - 10-H.P.P.- :-Vapuincc_`ra_^ iU3^ea(th>*rb'f.-dust pri^u^on^E^f'b^^im^'ab- i ha^d/^ ~Qccu^ticff^^^sas^^ii^e'':^lute control cope medical costs and. condensation and investigation the best possible ment/' of dust in the viomtyordust generating S^fles to guide the'-air. flow Vhere* if." .. equipment it is necessary to introduce .^Skis most needed, " "'L:- sufficient clean air faiin.thh outside .to' ^`Xn eatowt*'h2id^M^^M^ot'^ 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 at its source. Tb 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 exhaust air. The object of an ex haust system is to trap the contaminated air and not to remove the harmful dusts from it. It is suggested that the scat tering of large particles may be pre vented by the erection of suitable bar riers or, of course, by causing them to flow into the collecting duct. For effi cient operation of dust collecting equip ment, all air motion around the source ^-^enclose the process should be placed ^;~;..with its opening as close as possible '/-.'' to the point of dust generation since :'C' Vthe air velocity in' the'zone of hood "influence decreases, approximately with the square 'of .the distance .Wet vs. Diy Drilling. .from the face of the hood/T' " - ;-78. _ On the matter of^drilling, Har- '3. Shape the hood to conform with ' rington says: "v ' the shape of the area of dust pro "Dry drilling is, of co&rse, very much duction so as to secure reasonably more of a dust producer than wet drill uniform air velocity over.this area. ing---possibly in the ratio of_10 to 1. . For a given required air velocity at Wet drilling produces some "dust, but the point of dust generation, the if reasonable precautions are .taken, with . velocity at the hood opening should wet drilling, and suitable precautions be as low as possible. This is con- are also taken as to ventilation, as to '-trary to the common idea that the . the wetting of the muck pile, as to the . 'hood suction should be high. .time in which blasting is done, as to the precautions which are'.taken after 4. Provide flanges wherever possible : going back to the face after blasting " to reduce the air flow from inef .. . . there need be no particular harm to fective areas where no dust is pro- .workers in those places,'.as far. as 7 . ' du ced. *' dust diseases are concerned." , ,i. - S. Locate the hood opening, or part of it, so as to receive directly any >.> `y-.y ' 79. Prof. Philip Drinker, in com dust that is thrown off along a well- menting on the adoption of the New defined path, thus utilizing the di York State Code governing dustiness in rectional energy of the material for its own capture. rock drilling, stated: "This code divides all rock formation into two classes, class 1 being those ``Design of Exhaust Hoods for with less than 10 per cent free silica, Dust-Control Systems" by Theo dore Hatch, Harvard Graduate by weight, and class 2 being those with more than 10 per cent free silica. If School of Engineering and School drilling is done in class 1 rock, dust of Public Health, Boston, Mass. counts must be below 100 million per The Journal of Industrial Hygiene cubic foot, and below 10 million par and Toxicology, November, 1936. ticles if the rock falls in class 2. <. ^. ,v. _ RMC002277