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FILE NAME: Insulation Contractors & Distributors (ICD) DATE: 1944 June DOC#: ICD043 DOCUMENT DESCRIPTION: Trade Journal Article - Dust as an Industrial Health Hazard - Heating and Ventilating A O K T ttT hxqazive re* laro co irn e * erro fui trowcaonoD with eoK xrn cuii. u d d it r u u . aito n rn m m e w A L i Pl-AINTIFF s f EXHIBIT .HEATING V_ _ e n t ila AHV . t in g r coxrunio wua. ArnuocaAno*. rtrara. xsArnra. tdtttlatto [ PhLI Um THE in d u st r ia l p r e ss PresidsM ROBERT B. LUCHARS Vice-President ond Treosurer EDGAR A. BECKER Socretory ERIK OBERG td iia 'w al Is ia lfr Eo'.tor CLIFPORD STROCK Anociote Editor N. N. WOLPERT ^luAirUf DrJxyuna&H HEATING AND VENTILATING is published mon`hly by The Industriol Press at KB Lafoyet+e Street. New York 13. N. Y. Yearly sub scription in the United States. Spain. South America. Mexico, ond Conodo. 52.00: in all other coun tries. $3.00. Single copies 30 cents. Entered as second closs motter, April 18. 1925. at the Post Office. New York. N. y ,, under the oct of Mc*eh 3. 1879. fc&oAM&nltxiUuA. Eostem Representatives DWIGHT COOK HARRY J. TWINE M8 Lafayette Street New York 13. N. Y. Western Representative GEORGE G. TURNER 228 North Lo Salle Street Chljoao I. HI. CONTENTS F O R J U N E . 1 9 4 4 V O L U M E 41 NUMBER 6 Dut C ollectin g System In Gunstock Plant ................................................ 51 S. Xtilin G rinding W heel Q uality Improved by Controlled A ir ............................ 55 . C. *itr ** - Duet a t an Induetrlal Health H azard . ............................... . 57 F. H\ JftUiMnm V entilation tor W elding Booth ___ l .......... r .,4. . 1 . :C-d/t................. 52 U . . Rntgmist 1 V entilation for Radium Dial Storage . . .v ................................... , .......... 6d Off A gain, On A gain ........................................ ................................................. $4 /* J. U'tellnjt* Blueprint of R ett-W ar R e a litie s-- Coal for Heating and Steam Generation ......................................................................................... 55 tnrm R. Rttmtn Serna Note* on R adiant Heating ................................................................. 81 7. W. R t y l d , W eather Observer Have OlffSeultl* ......................................................... 81 Central Plant Heata 45 Building ................................................................. 82 F. S . B>lUtrm~tk Bu ilding B ra zil ................................................................................................ *. 84 W aih in gto n New ............................................................................................. 86 Ltrmt F. Otomrm New of th t Month ............................................................................................ 88 B rie f Review* ..................................................................................................... go New of Equipm ent and M aterials ............................................................. 82 Degree-Day* for A p ril, 1944 ............................................................................ ioo W ith the M anufacturer .................................................................................. S04 Reference Data 271-272 .................................................................................... 104 Personal* and Personnel .................................................................................. 107 Getting P e n o n a l ................................................................................................ 110 A rm y-N avy " E " A w ards .................................................................................. n o New Catalogs ..................................................................................................... 111 In d u rtrlal D egree-D ayi for A p ril, 1944 ........ .*........................................... 113 Com ing Event .................................................................................................... 113 C c o y r ig h t . 194-4. b y The Industriol Press MEMBER Adil 6g ,,u el Gi/cutel'or l Ai>oeina tuiintn P*p>* . NEXT MONTH'S ISSUE Process |Mi>:nc Is a subject that rene.hes out into many Industrie. Siarun c v. 1th our July issue Harry D. Unwin, of Albert Kbo A*soita"-l Architects t Engineers. Inc., will prerent tbe first of a ri-ric >. articles on -lcsicn ami layout of process plploc In* >w- .es the i heat; corn- mainnes. andled operatited by ount ot as the T ^__om latino Dusi as an Industrial Health Hazard F. W. HUTCHINSON Aasim nt ^(u er Meh*n(cal Im jlnssrino. U n l v . r , ^ Catiftrflla, B*ek*|t y, Calif. THE health problem arising from dust in indus try it one o{ increasing seriousness. Socially, economically and legally it hat become evident that immediate tteps mutt be taken to combat the hazard repretented by wholetale induttrial exposure to the pneumoconiosis-producing dustt. Pneumoconiotis, in many of its forms, it incurable. Thus consideration of the problem which it represents is based largely cs methods of dust reduction and removal and is therefore as much a responsibility of the engineer at it is of the physician. Fortunately, medical knowledge and engineering equipment have progressed to such a point that recognition of hazardous conditions and availability of methods for correcting them will now permit a complete, practical and economical solution of the problem. Unfortunately, prejudice and fear have surrounded the entire subject with such an aura of suspicion and distrust that neither workmen nor em ployers have until recently been willing to acknowl edge the hazard or recognize the need for preventive measures. In addition, the slow action of the disease coupled with failure on the pan of many physicians to acquaint themselves with the proper diagnostic methods has made it difficult for the worker to es tablish his claim for compensation in the event of lung injury and equally difficult for the employer to defend himself against fraudulent claims; it has been said that silicosis claims constitute one of the most widespread of legal rackets. Workmen have bitterly opposed adoption of the exacting employment qualifications and periodical physical examinations of those exposed to dust which ire essential to medical control. Yet, it is essential that persons having a predisposition to tuberculosis or a low nasal filtering efficiency be excluded from the dusty trades. Similarly, protection of the worker demands that he be removed from exposure at the first indication of lung damage. Employers, on the other hand, have adopted the point of viewthat most claims of silicosis are unfair and in unscrupulous attempt to take advantage of them. The explanation behind an employer's unwillingness to acknowledge the hazard is not unreasonable. The dust diseases are almost invariably of long duration ind frequently are not discovered until many years after exposure has ceased. Thus many employers ire now in the difficult and alarming position of fac ing claims for disease which is a result of exposure to conditions that existed in their plants 10 or 15 years ago; at that time they were unaware of the health hazard associated with dusty atmospheres Jnd consequently, though they might have had every desire to furnish their employees with full protection from occupational injury, they did not take the " pedal care" which it now known to be necessary. Wilson tates: " Most well-intentioned employers may be aid to have used `reasonable care* in past years and---considering their lack of knowledge-- this it now their best defense in damage suits. How ever, from now on, with the spread o f . . . available know ledge... only `special care' will safeguard the interests of employer and workman alike." Recent interest in dust diseases has built up an extensive literature; theories have been confirmed with experimental evidence and innumerable case histories of individuals and of entire groups are available. In contrast to the widespread ignorance of ten years ago, it would probably be difficult at the present time to find a worker in the dusty industries who has not it least heard of silicosis, or an employ er who is unaware of the crippling damage suits which will face him if his employees, through failure on his pan to take the necessary preventive mea sures, contract the disease. The cost of dust control is often far less than the cost of ope damage suit. Jury awards in silicosis cases of $1G,000, $17,000, $22,500, $25,000 and like sums are matters of record. In the St. Louis area alone there were, some time ago, over 2000 suits pending. A Missouri mining company, as another example, faced claims aggregating $5,000,000 and spent $500,000 in out-of-court settlements of a few of them. The purpose of this article is to review the liter ature on the physiological effects of some of the haz ardous industrial dusts and to summarize presentday criteria acceptable as a basis for the design of dust control systems. Silicosis Silicosis is a disease of the lungs caused by the inhalation of dust containing free silica. Some authorities believe, but this fact has not been estab lished, that the inhalation of silicates is also a caus ative factor. incurable and Progressive. The important facts about this disease are that, for practical purposes, it is progressive and incurable. The qualification " for practical purposes" is necessary' because recent in vestigations suggest that uncomplicated silicosis is not progressive; however, the continued existence of a case of silicosis without the onset of complications is so rare that, from the standpoint of social conse quences. the disease can in itself be regarded as pro gressive. In the medical literature the "progressive" h U T | N G A N D V E N T I L A T I N G . J U N E . 1*44 57 ^ i j i?r in ti; j viewpoint !i the one which has been most widely M eullica" and, with reference to dust, warned hi; adopted but the possible future significance of the recent findings is promising. i*| readers to beware because it "penetrates into the windpipe--eats away the lungs--implants consump With re/ereoce t$,lhe "incurability" of silicosis, tion in the body." He called attention to the fact recent work has also indicated the possibility of a that the death rate among Carpathian miners wj solution but it is as yet too soon to hold out hope so great that a wife could often outlive six husbands. for satisfactory medical treatment. One.promising Thn passage of time has done little to alleviate the method consists in the administration of thyioxene; hazard. The development of pneumatic tools has led the investigators report that: to a great increase in the dust concentrations at "Thyroid therapy may possibly not only prevent tending the grinding, polishing and cutting of stone. the development of silicosis, but may also arrest The death rate among Barte granite cutters, for ex its further progress and possibly reduce to some ample, increased from 1.5 per 1,000 in the year 1890 extent the degree of fibrosis already existing." to 19.6 per 1,000 in 1924, an increase attributable to The above remarks on the " progressiveness and the introduction of pneumatic equipment. When one incurability" of silicosis have been included because realizes that a threshold concentration of 5 million they show how very far the medical profession has panicles per cubic foot is required to constitute a yet to go to achieve a solution of the silicosis prob silicosis hazard (for dust made up of 100% free lem. In terms of concrete present-day gain, the sum silica), it is then evident that there are many indus total of the best that medicine can now offer is not trial operations today which represent health haz of much value. When dealing with contagious dis ards that did not exist prior to the introduction of eases such as smallpox and Spanish influenza, it mechanical equipment. has been possible to achieve a satisfactory treatment Many estimates have been made of the number as a first step toward the elimination of the disease of persons exposed to hazardous concentrations of itself; in the case of silicosis, a non-contagious dis silica dust, but such estimates are usually based only ease, the only advance of real significance which is on industrial exposure. When account is taken of possible is an advance which must be brought about the fact that 60% of the earth's crust consists of by the application of basic engineering principles-- silica the likelihood seems great that such estimates 'the reduction of dust concentrations at the breathing are conservative. Lanza and Vane estimated that 2one to a point such that a health hazard no longer the number of industrial workers exposed to the exists; only in this way can silicosis be eradicated. silica dust hazard is in excess of half a million in If permitted to run its course without complica those industries in which the processing or handling tion, silicosis will lead to death by suffocation--the of siliceous material is of basic importance; this esti lungs becoming incapable of maintaining a gas trans mate does not take account of the many workers fer sufficient to sustain life. Usually, however, ter exposed as a result of the industrial use of silica as mination occurs as a result of complications such as a filtering agent. tuberculosis or heart disease; a definite correlation In one other respect the silicosis hazard has not has been established between silicosis and tubercu yet been evaluated. As already mentioned there it losis, but an explanation is, as yet, lacking. a definite relationship between silicosis and tubercu With reference to tuberculosis a study of axe losis. This fact leads to the probability that in any grinders and polishers showed a death rate of 1,900 community in which there is a large number of sili- per 100,000 from tuberculosis as contrasted with ISO cotics there will be a decided familial tuberculosis per 100,000 for the general population of the same hazard. Fortunately, however, this danger is some state. In this study the death rate of all workers in what lessened as a result of the long incubation the dusty trades investigated was used. More strik period which is found with silicosis--by the time a ing figures and more significant ones were obtained workman's lungs have reached the stage at which from a Massachusetts investigation in which the tuberculosis is most likely to set in it is more than tuberculosis death rate of 961 silicotic quarry work probable that his children will have grown past the ers was compared with that for the general popula age at which the danger of their contracting the dis tion and found to be forty times as great. ease is greatest. Background and Extent. The name silicosis is of That silicosis is definitely related to a particular relatively recent origin, but the existence of the kind of occupational risk is demonstrated by the health hazard associated with dusty work has been data from examinations (X-ray) o{ 2500 workmen recognized by medical men for many centuries. from all departments of a typical "heavy industry" ; From the literature of the period we find that the 5.8% had silicosis, but 90.0% of those affected were Ptolemies knew of it. Pliny the Elder 'eferred to foundry workers. The great importance of the silica the ``stone cutters' disease" and devised a crude hazard is clearly indicated from the fallowing com respirator for tiac protection of m in e rs; AnSlOtlc parative mortality figures (from a 1933 publication warned Greek workmen against the inhalation of of Hollis and Y ule): dust. Hippocrates, three centuries before Christ, noticed that his surgical knives were dulled by dust 1000 for standard population (all causes for ages 20-65) t .\ in the lunes of stone workers. In the 16th century Georges Agricola, a mining engineer, wrote "De Re 1984 for silica group 967 for non-silica group Tfcc tUica group (above) showed only three causes 0{ death (diabetes, appendicitis, digestive diseases) vhich did not differ significantly from the general yroup. The significance of these figures is at once ipparent when it is considered that an estimated 110,000 workers in the United States have silicosis is some degree. Development of the Dvease, The time required for incapacitation due to silicosis has been the sub ject cf a great deal of attention, but as yet no gen erally accepted conclusions have been reached. Ap parently the period of exposure preceding contrac tion of the disease is a function of the dust concen tration, nature of the dust, nature of the work and individual physical idiosyncrasies. From a study of 9,BOOstone-cutters in the Ruhr it is concluded that 13 years exposure are required to show slight sili cosis and 20 years to cause incapacitation. This same study reveals that 63 7 of the deaths among silicotics occur from tuberculosis complications. In porcelain workers silicosis develops slowly but pro gressively: the second stage is usually not reached until after 10 years. Among sandstone workers the ainimal exposure has been found to be 11 years while for iron miners in exposure of 4 to 5 years may be responsible for the appearance of lung changes 4 to 8 years after the exposure has ceased. In contrast to the above relatively long incubation periods are those found among workers engaged in sand-blasting and in the manufacture of abrasive soaps; in these occupations only 3 or 4 years may precede the onset of the disease. Likewise, an exam ination of 175 men engaged in rock drilling showed that 507* were affected in less than one year. There is a good reason for believing that under particularly heavy dust concentrations silicosis takes an acute form and may appear after an exposure of only a few months. Not soon forgotten will be the case of the Hawk's Nest Hydro Plant on the New River. Some 4000 workers, mostly negroes, were employed for wages of $3.00 for a 13-hour day; !n a relatively short time after completion of the tunnel work 475 of them were dead and an estimated 1500 others incurably ill. This case was investigated by a committee in the House of Representatives before vhom witnesses testified that, "In the tunnel 10 drills were in operation at once and you could not set ten feet ahead of you even with the headlight of the donkey engine" . Workmen were so thoroughly covered with a silica dust that "you could not tell a white man from a colored man, 15 feet away" . It vat this case that a senator from West Virginia deKribed as "the most horrible industrial disaster in the history of the world" . It was of this case that Representative Marcantonio of New York charged that 169 workers had been buried unidentified be cause the undertaker had "lost" his records. On the basis of a',1 evidence which has yet been brought for ward it would seem to the impartial investigator that the Hawk's Nest Tunnel should remain a tragic ;imjcder to the engineer of the need for consider ation of human values in the solution of engineering problems. The above case is only one of a number of similar but less sensational cases which have shown that there is a real possibility of contracting an acute form of silicosis if work is in an atmosphere having an extremely high concentration of siliceous dust. Experimentally the possibility of acute silicosis has been demonstrated by laboratory tests on animals; for exposures of eight hours a day to concentrations of 200 million particles per cubic foot or more it has been shown that the last stage of silicosis may be expected in a relatively short time. Size of Hazardous Dust. The importance of par ticle size in determining the hazard associated with dusts has received a great deal of attention. Par ticles 25 to 30 microns in size will usually settle out rapidly and are therefore not likely to be breathed in quantities sufficient to constitute a hazard. How ever, particles of this magnitude (such as pollen of the Giant Ragweed or wood dust in carpenter shops) may be responsible for hay fever or for various types of asthma. In general, particles greater than 10 mi crons are caught in the trachea, large bronchi and mucous membrane. Particles around 5 microns go to the respiratory tract, but few of them reach the alveoli where the 1 micron particles are most numer ous. Policard made a detailed examination of the lungs of two silicotic miners and found that 50% of the particles were less than .4 micron and 75% less than 1 micron; his findings should be used with care, however, because it is very probable that the dust distribution in the lungs is a function of the distribu tion of particle size in the inhaled dust--thus Poli- card's findings may be applicable only for the con ditions under which the men whose lungs he examined had worked. The smaller particles are obviously the most dangerous since, on a weight basis, they offer a much larger surface than do the larger ones. For this reason dust counts are of more value in evaluating the hazard associated with a dusty environment than are gravimetric dust de terminations. The dust particles that are most effective in the causation of silicosis are of a magnitude so small that they are not perceptible to the human eye. A micron is 1/1000 of a millimeter or about 1/25,000 of an inch. As has been shown, the particles most important in silicosis arc in the neighborhood of .5 micron or 1/50,000 of an inch--this represents a di mension of the same order of magnitude as the wave length of that form of radiant energy which we recognize as light. If one cubic inch of quartz were broken into cubes .5 micron on a tide enough par ticles would be formed to create a silicosis hazard in a 250,000 cubic foot space. The determination of mean dust tizes was the purpose of a series of comprehensive studies con ducted by the U. S. Public Health Service: examina tion of 18,000 outdoor dust particles showed the median size to be .5 micron--nearly all were less BATING A N D V E N T I L A T I N G , J U N E , 1&44 59 than 1.0 micron; in contrast, only 21% of 6,000 in- dmtrixJ du*t pirtidei were leu than 1.0 micTon, the tnajoriry being between 1 and 3 microns and the mean 1.5 microns. Hatch and Moke investigated foundry dusts and found that composition is a function of partide size: the proportion of combustible matter and add sol uble iron, carbonates, etc., increase with decreasing m e ; the proportion of day and other silicates varies without a definite trend with size; the quartz be comes less as the size decreases and for particles un der 2 microns (which comprises 90% of the total number) it is from 1/S to 1/25 of that found in the particles greater than 10 microns. These findings emphasize the necessity of taking dust samples di rectly from the contaminated air and not utilizing " rafter" or any other kind of settlement sample which does not contain a representative size distri bution. Hatardovs Concentration. Permissible concentra tions of dust vary with size, composition, and the dust retention characteristics of the individual. The latter factor is one which offers some hope from the standpoint of preventive medirine. Practically all that is known of the dust retaining characteristics of the human nose is attributable to the work of one man--G. Lehmann. This experimenter has shown that the dust fixation in the nose varies from 2% to 75 % and is almost completely independent of such factors as the condition of the nasal secretion, the rate of air currents, the degree of concentration or chemical composition of the dust, the width or narrowness of the nasal passages; seemingly, fixa tion is a function of the vortex formation and re bound after passage through a restriction. A correlation between fixation and silicosis would seem to follow from the following tests: Of 46 stone cutters with fixations above 40% only two were found to have silicosis; of 31 stone cutters with fixa tions less than 29% only 2 were healthy. After ex amining the above data Lehmann concludes that, "applicants for work with poor dust fixation capacity should not be allowed to work where a menace of silicosis exists" . As a result of 418 experiments with magnesium oxide and calcium carbonate, Carlton E. Brown gives the following relationships between dust re tention and other factors: Per Cent Retention is inversely proportional to 1. Respiration rate for rates below 20 per minute. An increase above 20 per minute is apparently followed by no changes in per cent retention. 2. Minute-volume of air breathed. This prob ably results from increase in respiration rate with minute-volume. Per Cent Retention is unaffected by 1. Volume per respiration. 2. Vital capacity. 3. Relative humidity. The same investigator found that the percentage of tnig^ieiium oxide retained during normal breathy while at rest varied little from about 60% lt 4 castration of 10 mg. Above 10 mg. the m eat changed but little, but at the concentration droppe below 10 mg. the retention rapidly appro**. 100% . The relation between dust concentration and incidence of silicosis has been studied by many veatigators, but no general empirical relationship hat as yet been established. One commonly ustc rule (proposed by Drinker) recommends the acctp. tance of 5 million particles per cubic foot as tht minimal permissible dust concentration for pun; silica and 50 million particles per cubic foot for dum that are very low in silica. Some evidence sugguu that this rule is unduly conservative for dusts which contain little silica and an alternative which is widely used is to limit the total dust count to a value such that the product of the dust concentration by tit percentage of silica be less than 5,000,000; this rule gives 100,000,000 particles per cubic foot as the minimal concentration for non-siliceous dusts. Physiological Effect. The lung condition known as silicosis results only from the inhalation of silica bearing dusts. Why silica possesses the ability to bring about this condition has been the subject of much investigation and theories of silicosis are at present responsible for considerable controversy. Physiologically--excluding the effect of complica tions--tilicosis affects the normal functioning of the body in the tame way that the formation of scale affects the efficiency of a heat transfer device. In the heat exchanger the hot and cold fluids are sepa rated by an exchange surface and the deposit of scale on this surface reduces its effectiveness as an exchange medium. If the scale becomes sufficiently heavy it will be impossible to secure the transfer of enough heat to accomplish the purpose for which the exchanger was installed; similarly, the lung is a sur face through which oxygen is transferred from the air to the blood. The formation of scar tissue re duces the effective transfer area and eventually the lung is unable to accomplish its purpose-- death from suffocation is the Tesuh. Aibwstosis Asbestos dust is second only to free silica in the magnitude of health hazard which it represents. Asbestos is a fibrous material of varying composi tion, but is usually made up of approximately 43% magnesia, 40% silica and 14% water. Oxide of iron is frequently present and appears as dark particles among the translucent fibers--the fibers are of such length and fineness that cloth weighing less than 8 oz. per square yard has been made from them. The lung condition resulting from the inhalation of this dust is known at askestosis and rcicmb!cs silicosis in its main clinical aspects, but differs due to the enhanced rate of development. Under average industrial conditions the length of employment in fatal cases is only about one-half that which i* usual 60 J U N E r tm , HEATING AND VENTILATING far olicoaia. It it eatimated that there are in the 1 bruth^ lined Sutci approximately 10,000 men cxpoaed to to hazard at a result of work in the insulating, - pt6 ubettos doth, and similar industries. At it true of & silicosis expoaure esumates, this figure does not r'roicbftj ultimo account the number of periont expoted as , retell of employment in the procett induttriet and ^ ' many a . ciatiooihip aonly used here iibeitoa finds use,under various trade names, sit filter aid. In one respect asbestocis it lets dead lythan silicosis--that is, there it seemingly a lower susceptibility to the supervention of pulmonary tu the acctp. at ti, for purt berculosis. The danger of contracting the disease it ipparently not influenced by either age or sex. Like silicosis, it is incurable and progressive; a cite it re >t for duita ported of a patient who wit exposed to atbestos dust :e tul8 u lot one year and whose tputuro showed the presence usts which 1 oftibestosis bodies fourteen years later. h is videly Very few data are available on the relation of dust Millie uch concentration to the inddence of the disease. No on by tlx minimal safe concentrations have yet been set up '! this rult ot as tit usts. on known i of silica* ability to subject of and information it scant as to the conditions in those pilots where a hazard is known to exist. It has been actermined, however, that the asbestos dust en countered in fabricating plants is free of silica when lir is floated at the breathing level and that the dinger of the dust increases as the quality or length of the fibers increases. sis are at V* atroveny. oomplica* Hiseallarxout Siliceous Dusts r r Many siliceous dusts other than quaru and asbes Jcale ar tos have been carefully investigated. Talc--a sili In cate containing 62 % silica--has been shown to be are sepa* responsible for a form of pneumoconiosis when in- eposit of tiled in large quantities. One group of investigators ess as an r report that 50% of the talc workers whom they exjfficiently imined were affected and about 12% had tubercu ansfer of lous. The same report shows that talc containing vhieh tit 10% tremollte is much more dangerous than talc is a sur- containing 40% tremolite, but an explanation is from the licking. issue re- The action of cement on the lungs is not definitely ually the bown. German investigators say that it produces ath from only an inert deposit in the lungs, but American re ports show that the frequency of disability from respiratory diseases in cement plants is about double that found among employees in non-dusty manu a in tie facturing plants; absence from work was alto twice ^resents. is frequent. Yet animal experiments show that ce :omposi- ment like limestone and gypsum produces an ad ;l>` <3% sorptive reaction; the dust disappears from the : of iron pentoneal cavity without the_ production of scar particles tissue. of such : Slate (1/3% quartz) in concentrations of 700 than 8 million particles per cubic foot produces a fibrosis m. and pneumoconiosis, but few cases have been known talation to progress seriously. On the other hand, there is 'on for believing that day and slate dusts are responsible for a high incidence of tuberculosis. Italian investigators have studied the dust hazard nent in is usual "t cotton spinning mills and report that the silicosis hazard is apparently negligible. Mineralogic analy- is of such dusts brought to light the interesting fact that their composition it similar to thst of the toil in which the cotton was grown. HoevSilicwoua Dusts Apparently there is a gTeat difference of opinion as to whether or not noo-tiliceous dusts are harmful either to normal or tubercular persons. The data are so scant that a review of the literature mutt con sist essentially of a catalogue of the few and scat tered investigations that have been made of particu lar dusts. General condusions can not be drawn and an extension of available data to dusts of even the same mineral family is hazardous. German investigators have studied a number of different carbon dusts and rate them in the order of hazard which they represent; lignite, coal, graphite, charcoal, soot. A statistical study of the health hazard in a large American company which manufactures artificial abrasives led to the condusion that persons who have bad pulmonary tuberculosis should not be al lowed to work where they will be exposed to dust from abrasives. The dust in this particular plant was aluminum oxide combined with silicon carbide and the inddence to tuberculosis was 1 1/2 times as great in the dusty departments as in the non-dusty. In this connection it is interesting to note that other investigators had previously reponed aluminum ox ide as not being a factor in the production of silicosis --thus a distinction must be drawn between the fibrosis-forming ability of a particular dust and its danger through increased susceptibility to pulmonary tuberculosis. This leads to the conclusion that the daim is unwarranted that a dust is not harmful merely because its reaction on lung tissue is inert. The U. S. Public Health Service has grouped dusts (siliceous as well as non-siliceous) in three classifi cations: 1. Those causing an inert reaction, the amount of dust in the peritoneal cavity remaining approxi mately constant: soapstone, carborundum, jewel er's rouge, anthracite coal, bituminous coal and precipitator ash. 2. Those causing a proliferative reaction, nod ules continuing to increase in size: quartz, chat and flint. 3. Those causing an absorptive reaction, dust disappears from the peritoneal cavity, but scar tissue is not formed: calcite limestone, precipitat ed calcium carbonate, gypsum and cement. A similar list of dusts has been prepared by Haynes who carried on a long series of animal ex periments. He arranges them in order of toxicity as follows: precipitated silica, flint, slate, hydroxide, precipitated chalk, magnesium carbonate, carborun dum, ealtpar, emery, colloidal coal (Q massive amounts). All of the respiratory disorders discussed above, together with many others which are caused by the inhalation of fibrosis-forming dusts, are grouped un der the one broad term Pneumoconiosis. A T 1NC BATIN G a n d VENTILATIN G , JUNE. 1H4 61 i ALPHABETICAL INDEX OF ADVERTISERS Penn Electric Switch Co................ Acme Industries ............................. <3 Air Conditioning Engineering Co. 116 Air-Maze Corporation .................... 40 General Controls Co........................ 107 General Electric Co......................... * Porter, H. W., & Co.. Inc.............. Ill Powers Regulator Co......................117 PropeUair, Inc..................................' Airterap Dir. Chrysler Corp...................4 A lrthem Mfg. Co............................. 10$ H AIco Valve Co...................................11-24 Allen Corporation........................... 13 American Air Filter Co., Inc..................27 Hays Corp.......................................... 117 Henry Valve Co............................... * Holcomb Hoke Mfg. Co............ 39 Reznor Manufacturing Co.............. 1 Ric-wil Co......................................... ) American Blower Corp................... American District Steam Co......... 119 Ameriean-Msrsh Pumps. Inc......... Howell Electric Motors Co., Inside Back Cover h S American Rolling Mill Co............. 14 Armstrong Machine W o rk s.......... 10 Automatic Products Co..................... 10S B m Badger Mfg. & Sales Co................. Baidor Electric Co.......................... 105 I Ug Electric Ventilating Co............. * Illinois Engineering Co., Inc......... * Illinois Testing Laboratories, Inc. 114 Iron Fireman Mfg. Co....................... 101 Sail Mountain Co.................................* , Sarco Company. Inc........................ Sarcotherm Controls. Inc.............. Ii* Smith, H. B.. Co., Inc...................... Somers, H. J.. Inc........................... Star Electric Motor Co.................. 21j Superior Sheet Steel Co................ Barber-Colman Co............................ 38 Bell A Gossett Co............................ 35 Bethlehem Steel Co......................... 97' Johnson Fan Blower Corp......... 36 Johnson Service Co............ Back Cover Breldert, G. C.. Co........................... * Taylor Forge Pipe W ork*....... 22' Brooks Equipment Co..................... 114 Bryant Heater Co............................ 32 Buffalo Bolt Co................................ 7 Buffalo Forge Co.............................. 45 yers. A. M., Co................................ * K Kewatiee Boiler Cotp...................... 8 Korfund Co., Inc.' ........................... 119 Thrush. H. A.. & Co. ..................... XX' Todd Shipyards Corp. (Combus tion Equipment Div.) . . . . ' ........ M Trane Co. . v................................. U} Trerice, H. O., Co................... 1UJ Tube-Turns. Inc............................... 91 VL *K Carey, Philip. Mfg. Co.................... 34 li-' Carrier Corporation ......................... 33 , Caah. A. W.. Valve Mfg. Corp. . . . 32 ir Chrysler Corporation ................... 4 ili1 Classified Advertising ................... 116 Continental Steel Corp................... * to Crane Co............................................ 31 i Crown Iron Works Co.......................US Curtis Refrigerating Mch. Div. of Curtis Mfg. Co.............................. <8 . Detroit Lubricator Co..................... 6 Detroit Stamping Co......................... 119 f Dravo Corporation ......................... 93 Dunham, C. A., Co........................... 303 Ladish Drop Forge Co.................... 29 Lelasd Electric Co.......................... 23 Link-Belt Co.......................- ............ 16 M Marley Co.. Inc................................... Mario Coil Co...................................... 41 Marsh. Jas. P., Corp.......................... 49 Mercoid Corp...................................... 37 McCord Radiator Mfg.Co............. 117 McDonnell M iller....................... 95 Minneapolis-Honeywell Regulator Co........................ Inside Front Cover Modine Manufacturing Co............. 42 Mueller Brass Co............................. 26 u Tuttle Bailey, Inc........................ U U. S. Machine Corp. United S u te s Air Conditioning Corp........................................... United States Radiator Corp. ... W m Wagner Electric Co..........................IK Want Advertisements .................... Ili Webster. Warren. Co Weeks. B. H.................................... Westinghouse Electric Manu factunng Co.................................4t-4X, White Rodgers Electric Co. Nash Engineering Co...................... 50 Whitlock Manufacturing Co. t Economy Pumps. Inc....................... * 1MTi EEllegcotrSihcuAttuetro-UtMe aCnou.f..a.c..t..u..r.i..n..g....C..o... 112* ;ti: Ellsworth Pipe Supply Co......... 17 Nelson, Herman. Corp...................18-19 Owens-Corning Fiberglas C o rp ... 99 Wing. L. J.. Mfg. Co. 1UV$ Worthington Pump Machinery Corp................................................ )Emerson Electric Manufacturing Co.................... ..................................... * ili 31:i. Freeman Stoker Div. Illinois Iron I Bolt Co............................................ I l l ti'.L io n Pacific Steel Boilers ..................... 5 Patterson-Kelley Co.. Inc............... * Peerless Pump Div., Food Machin ery Corp.......................................... 110 Yamall-Waring Co................ 109-114-Ui1 York Heat Div.. York-Shlpley, Inc. Young Radiator Co...................... ;. 1B\ --*AdttruA#**1* '-X J