Document 71QBVzepeXmG2M8mKGz9y1oNo

FILE NAME: Carrier (CAR) DATE: 1944 June DOC#: CAR004 DOCUMENT DESCRIPTION: Trade Journal Article - Dust as an Industrial Health Hazard V Heating Ventilating a w iim r masazipe reii i i a i m t i i i jars eeirnuecToita coucoarxs with . :r "i-r commsmcul. arovm tua juts w u m m o * . * cowomoimra, xaraaoumoM , psrara. u r n , ro m u m sir ii OuJduktA THE IN D USTRIAL PRESS CONTENTS F O R J U N E , 1 9 4 4 President ROBERT B. LU C H A R S V O L U M E 41 NUMBER 6 1 Vice-President ond Treosurer EDGAR A . BECKER Secretory Du*t Collecting System In Gunstoek Plant ................................................ 51 Benjemin J. Utlin Grinding Wheel Quiltty Improved by Controlled A i r ............................ 55 /. C. Baker ~ , ERIK OBERG Duet as an Industrial Health Hazard F, B'. ftntekm m ...............................'. A .. . \ ^ , .. 57 H M taiial S ta ll Ventilation for Welding Booth* . . . . ( .......... >. .V. i(t4 1. . * 62 Editor CLIFFORD STROCK Associate Editor U . E. Xn.rovia \ ` ''+V 1 i Ventilation for Radium Dial Storage ^ .v..................................... , .......... 1I Off Again, On A g a in ...................................T. . . .'.T......................................... 6 lokn J. tt'oelftndtn ' ' N, N. WOLPERT Blueprint of Pott-War Realltlea--Coal for Heating and Steam Generation ........................................................................................... 65 publuiw tq $nl>unaiia*i Irwin X. Batmen Some Note on Radiant Heating .................................................................. 81 H E A T IN G A N D V E N T IL A T IN G is T. W. Xeynetdi l published mon`hly by The Industrial Press of 148 Lafayette Street, Weather Obaervert Have Dlffleultle ........................................................... 81 New York 13, N . Y. Yearly sub Central Plant Heat 45 B u ild in g................ .................................................. 82 scription in the United States, F. ti. BeUinitwertk Spo>n. South Am erica, Mexico, and Building Brasil .......................................................................................................... 84 C anada, $2.00: in all other coun tries, $3.00. Single copies 30 cents. Entered as second class m atter, April 18. 1925. a t the Post Office, New York, N , Y,, under the a c t of Mc-ch 3, 1879. Waahlngton New .................................................. 86 Larint F. Overmen New of th Month ............................................................................................. 8$ Brief Revlewa ............................................................... ; ..................................... 90 New of Equipment and Material! ............................................................... 92 Degree-Day for April, 1944 ............................................................................. 100 Aiue'U U ixq (iApAM M iatiuei With th Manufacturer .............................. 104 Eostem Representatives D W IG H T COOK HARRY J. TW INE 148 Lafayette Street New York 13. N . Y. Reference Data 271-272 ..................................................................................... 104 Personal and Personnel .................................................. 107 Getting Personal ........ 110 Army-Navy "E" Award .......................................................... 110 New Catalog .................................................................. Ill Western Representative GEORGE G . TURNER Industrial Dgree-Day for April, 1844 ........ .*............................................ 113 Coming Event .................................... 113 228 North Lo Salle Street Chicoao l, HI, Ccoyrighf. I944, by The Industriol Press f- NEXT MONTH'S ISSUE Process piping 1 a subject that reaches out into many industries. Startinc v. ith our Ju ly issue Harry D. Unwin, of Albert Kahn AKaocia'.-rl Architects & Engineers. Inc., will present the first of a m u ' articles on ilcslcn and layout of process piping In stallation jlhe : storage which is mount of governed : Mitmet thermois *et to ssor and mit. The maintain mpressor. sor funcsatisfied, tssot con come on. itrolled in heat. / is main- erates the ; on heat* ates com ace, main1 times. .ir handled tor operatctuated by amount of me as the nt for 38F to protect stem from VTILATING Dust as an Industrial Health F. W. HUTCHINSON Assistant Prefcxor *f Maehanleal Engineering, University #f Celifernte, Berkeley, Calif. Hazard THE health problem arising from dust in indus try is one of increasing seriousness. Socially, economically and legally it has become evident that immediate steps must be taken to combat the hazard represented by wholesale industrial exposure to the pneumoconiosis-producing dusts. Pneumoconiosis, in many of its forms, is incurable. Thus consideration of the problem which it represents is based largely on methods of dust reduction and removal and is therefore as much a responsibility of the engineer as 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 part 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 are 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 pant of viewthat most claims of silicosis are unfair and an 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 and frequently are not discovered until many years after exposure has ceased. Thus many employers are 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 and consequently, though they might have had every HEATING AND V E N T IL A T IN G , JUNE, 1944 desire to furnish their employees with full protection from occupational injury, they did not take the "special care" which is now known to be necessary. Wilson states: "Most well-intentioned employers may be said to have used `reasonable care' in past years and--considering their lack of knowledge-- this is now their best defense in damage suits. How ever, from now on, with the spread o f . . . available knowledge. . . 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 at 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 part to take the necessary preventive mea sures, contract the disease. The cost of dust control is often far less than the cost of one damage suit. Jury awards in silicosis cases of *10,000, *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" 57 viewpoint is the one which has been most widely adopted but the possible future significance of the recent findings is promising. With reference t:The "incurability" of silicosis, recent work has also indicated the possibility of a solution but it is as yet too soon to hold out hbpe for satisfactory medical treatment. One, promising method consists in the administration of thyroxene; the investigators report that: "Thyroid therapy may possibly not only prevent the development of silicosis, but may also arrest its further progress and possibly reduce to some extent the degree of fibrosis already existing." The above remarks on the "progressiveness and incurability" of silicosis have been included because they show how very far the medical profession has yet to go to achieve a solution of the silicosis prob lem. In terms of concrete present-day gain, the sum total of the best that medicine can now offer is not of much value. When dealing with contagious dis eases such as smallpox and Spanish influenza, it has been possible to achieve a satisfactory treatment as a first step toward the elimination of the disease itself; in the case of silicosis, a son-contagious dis ease, the only advance of real significance which is possible is an advance which must be brought about by the application of basic engineering principles-- ' the reduction of dust concentrations at the breathing zone to a point such that a health hazard no longer exists; only in this way can silicosis be eradicated. If permitted to run its course without complica tion, silicosis will lead to death by suffocation--the lungs becoming incapable of maintaining a gas trans fer sufficient to sustain life. Usually, however, ter mination occurs as a result of complications such as tuberculosis or heart disease; a definite correlation has been established between silicosis and tubercu losis, but an explanation is, as yet, tacking. With reference to tuberculosis a study of axe grinders and polishers showed a death rate of 1,900 per 100,000 from tuberculosis as contrasted with 150 per 100,000 for the general population of the same state. In this study the death rate of all workers in the dusty trades investigated was used. More strik ing figures and more significant ones were obtained from a Massachusetts investigation in which the tuberculosis death rate of 961 silicotic quarry work ers was compared with that for the general popula tion and found to be forty times as great. Background and Extent. The name silicosis is of relatively recent origin, but the existence of the health hazard associated with dusty work has been recognized by medical men for many centuries. From the literature of the period we find that the Ptolemies knew of it. Pliny the Elder leferred to the "stone cutters' disease" and devised a crude respirator for the protection of miners; Aristotle warned Greek workmen against the inhalation of dust. Hippocrates, three centuries before Christ, noticed that his surgical knives were dulled by dust in the lungs of stone workers. In the 16th century Georges Agricola, a mining engineer, wrote "De Re O Meullica" and, with reference to dust, warned his readers to beware because it "penetrates into the windpipe--eats away the lungs--implants consump tion in the bpdy." He called attention to the fact that the death rate among Carpathian miners was so great that a wife could often outlive six husbands. The passage of time has done little to alleviate the hazard. The development of pneumatic tools has led to a great increase in the dust concentrations at tending the grinding, polishing and cutting of stone. The death rate among Barre granite cutters, for ex ample, increased from 1.5 per 1,000 in the year 1890 to 19.6 per 1,000 in 1924, an increase attributable to the introduction of pneumatic equipment. When one realizes that a threshold concentration of 5 million particles per cubic foot is required to constitute a silicosis hazard (for dust made up of 100% free silica), it is then evident that there are many indus trial operations today which represent health haz ards that did not exist prior to the introduction of mechanical equipment. Many estimates have been made of the number of persons exposed to hazardous concentrations of silica dust, but such estimates are usually based only on industrial exposure. When account is taken of the fact that 60% of the earth's crust consists of silica the likelihood seems great that such estimates are conservative. Lanza and Vane estimated that the number of industrial workers exposed to the silica dust hazard is in excess of half a million in those industries in which the processing or handling of siliceous material is of basic importance; this esti mate does not take account of the many workers exposed as a result of the industrial use of silica as a filtering agent. In one other respect the silicosis hazard has not yet been evaluated. As already mentioned there it a definite relationship between silicosis and tubercu losis. This fact leads to the probability that in any community in which there is a large number of silicotics there will be a decided familial tuberculosis hazard. Fortunately, however, this danger is some what lessened as a result of the long incubation period which is found with silicosis--by the time a workman's lungs have reached the stage at which tuberculosis is most likely to set in it is more than probable that his children will have grown past the age at which the danger of their contracting the dis ease is greatest. That silicosis is definitely related to a particular kind of occupational risk is demonstrated by the data from examinations (X-ray) of 2500 workmen from all departments of a typical "heavy industry"; 5.8% had silicosis, but 90.0% of those affected were foundry workers. The great importance of the silica hazard is clearly indicated from the following com parative mortality figures (from a 1933 publication of Hollis and Y ule): 1000 for standard population (all causes for ages 20-65) 1984 for silica group 967 for non-silica group JU N E, 1944, H E A T IN G AND V E N T ILA TIN G n I the sfisp- a was ads. * the s led s tone. t ex1890 de to sone IHion ate a free dushazx t of The silica group (above) showed only three causes 0{death (diabetes, appendicitis, digestive diseases) which did not differ significantly from the general group- The significance of these figures is at once jpparent when it is considered that an estimated lJO,000 workers in the United States have silicosis in some degree. Development of the Disease. The time required for incapacitation due to silicosis has been the sub ject of 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 9,800 stone-cutters in the Ruhr it is concluded that 13 years exposure are required to how slight sili cosis and 20 years to cause incapacitation. This tame study reveals that 63% of the deaths among ailicotics occur from tuberculosis complications. In 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 tjiat 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 porcelain workers silicosis develops slowly but pro the Giant Ragweed or wood dust in carpenter shops) i, mber gressively; the second stage is usually not reached may be responsible for hay fever or for various types * ns of until after 10 years. Among sandstone workers the of asthma. In general, particles greater than 10 mi only minimal exposure has been found to be l l years crons are caught in the trachea, large bronchi and :n of while for iron miners an exposure of 4 to S years mucous membrane. Particles around 5 microns go ts of nay be responsible for the appearance of lung to the respiratory tract, but few of them reach the nates changes 4 to 8 years after the exposure has ceased. alveoli where the I micron particles are most numer that Id contrast to the above relatively long incubation ous. Policard made a detailed examination of the a the periods are those found among workers engaged in lungs of two silicotic miners and found that 50% of os is sand-blasting and in the manufacture of abrasive the panicles were less than .4 micron and 75% less idling soaps; in these occupations only 3 or 4 years may than 1 micron; his findings should be used with care, ; esti- precede the onset of the disease. Likewise, an exam however, because it 6 very probable that the dust r <rkm ination of 175 men engaged in rock drilling showed distribution in the lungs is a function of the distribu ca as that 50% were affected in less than one year. tion of particle size in the inhaled dust--thus Poll- i s not paTrthiceurelarilsy ahegaovoyddruesatsoconncfoerntbraetliioenvsinsgilitchoastis utnakdeesr cdaitridon'ssfinudnidnegrs mwahyichbe tahpeplicmaebnle ownhloyseforluthngescohne i\-, ere is an acute form and may appear after an exposure of examined had worked. The smaller particles are ercu- only a few months. Not soon forgotten will be the obviously the most dangerous since, on a weight n any case of the Hawk's Nest Hydro Plant on the New basis, they offer a much larger surface than do the if *ili- River. Some 4000 workers, mostly negroes, were larger ones. For this reason dust counts are of more j ulotis employed for wages of $3.00 for a 13-bour day; in value in evaluating the hazard associated with a somejatioo a relatively short time after completion of the tunnel dusty environment than are gravimetric dust de 1 ime a work 475 of them were dead and an estimated 1500 terminations. i which others incurably ill. This case was investigated by The dust particles that are most effective in the thaD a committee in the House of Representatives before causation of silicosis are of a magnitude so small st the whom witnesses testified that, "In the tunnel 10 that they are not perceptible to the human eye. A e dis- drills were in operation at once and you could not micron is 1/1000 of a millimeter or about 1/25,000 see ten feet ahead of you even with the headlight of of an inch. As has been shown, the particles most icular y the -imen stry"; l were i silica eom- } cation the donkey engine". Workmen were $o thoroughly covered with a silica dust that "you could not tell a white man from a colored man, IS feet away". It as this case that a senator from West Virginia de scribed as "the most horrible industrial disaster in the history of the world". I t was of this case that Representative Marcantonio of New York charged shat 169 workers had been buried unidentified be muse the undertaker had "lost" his records. On the important in silicosis are 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 side enough par ticles would be formed to create a silicosis hazard in a 250,000 cubic foot space. The determination of mean dust sizes was the basis of all evidence which has yet been brought for purpose o f a series of comprehensive studies con ward it would seem to the impartial investigator ducted by the U. S. Public Health Service: examina that the Hawk's Nest Tunnel should remain a tragic tion of 18,000 outdoor dust particles showed the reminder to the engineer of the need for consider- median size to be .5 micron--nearly all were less ATING HEATING AND V E N T IL A T IN G , JU N E , 1944 59 than 1.0 micron; in contrast, only 21 % of 6,000 in magnesium oxide retained during normal breathing dustrial dust particles were less than 1.0 micron, the while at rest varied little from about 60% at a con majority being between 1 and 3 microns and the centration of 10 mg. Above 10 mg. the retention mean 1.5 microns. ' changed but little, but as the concentration dropped Hatch and Moke investigated foundry dusts and below 10 mg. the. retention rapidly approached found that composition is a function of particle size: 100%. the proportion of combustible matter and acid sol The relation between dust concentration and the uble iron, carbonates, etc., increase with decreasing incidence of silicosis has been studied by many in size; the proportion of clay and other silicates varies vestigators, but no general empirical relationship without a definite trend with size; the quartz be has as yet been established. One commonly used comes less as the size decreases and-for particles un rule (proposed by Drinker) recommends the accep der 2 microns (which comprises 90% of the total tance of 5 million particles per cubic foot as the number) it is from 1/5 to 1/25 of that found in'the minimal permissible dust concentration for pure particles greater than 10 microns. These findings silica and 50 million particles per cubic foot for dusts emphasize the necessity of taking dust samples di- that are very low in silica. Some evidence suggests rectly from the contaminated air and not utilizing that this rule is unduly conservative for dusts which "rafter" or any other kind of settlement sample contain little silica and an alternative which is widely which does not contain a representative size distri used is to limit the total dust count to a value such bution. . " Hazardous Concentration. Permissible concentra that the product of the dust concentration by the percentage of silica be less than 5,000,000; this rule tions of dust vary with size, composition, and the gives 100,000,000 particles per cubic foot as the dust retention characteristics of the individual. The minimal concentration for non-siliceous dusts. latter factor is one which offers some hope from the Physiological Effect. The lung condition known standpoint of preventive medicine. Practically all as silicosis results only from the inhalation of silica that is known of the dust retaining characteristics bearing dusts. Why silica possesses the ability to of the human nose is attributable to the work of one bring about this condition has been the subject of man--G, Lehmann. This experimenter has shown much investigation and theories of silicosis are at that the dust fixation in the nose varies from 2% present responsible for considerable controversy. to 75% and is almost completely independent of ' Physiologically--excluding the effect of complica such factors as the condition of the nasal secretion, tions'--silicosis affects the normal functioning of the the rate of air currents, the degree of concentration body in the same way that the formation of scale or chemical composition of the dust, the width or affects the efficiency of a heat transfer device. In narrowness of the nasal passages; seemingly, fixa the heat exchanger the hot and cold fluids are sepa tion is a function of the vortex formation and re rated by an exchange surface and the deposit of bound after passage through a restriction. scale on this surface reduces its effectiveness as an A correlation between fixation and silicosis would exchange medium. If the scale becomes sufficiently .seem to follow from the following tests: Of 46 stone heavy it will be impossible to secure the transfer of cutters with fixations above 40% only two were enough heat to accomplish the purpose for which the found to have silicosis; of 31 stone cutters with fixa exchanger was installed; similarly, the lung is a sur tions less than 29% only 2 were healthy. After ex face through which oxygen is transferred from the amining the above data Lehmann concludes that, air to the blood. The formation of scar tissue re "applicants for work with poor dust fixation capacity duces the effective transfer area and eventually the should not be allowed to work where a menace of lung is unable to accomplish its purpose--death from silicosis exists". - suffocation is the result. As a result of 418 experiments with magnesium V oxide and calcium carbonate, Carlton E. Brown Asbestosis - gives the following relationships between dust re tention and other factors: " Asbestos dust is second only to free silica in the magnitude.of health hazard which it represents. Per Cent Retention is inversely proportional to Asbestos is a fibrous material of varying composi 1. Respiration rate for rates below 20 p e r' . tion, but is usually made up of approximately 43 % minute. An increase above 20 per minute magnesia, 40% silica and 14% water. Oxide of iron . is apparently followed by no changes in is frequently present and appears as dark particles per cent retention. among the translucent fibers--the fibers are of such 2. Minute-volume of air breathed. Phis prob- length and fineness that doth weighing less than 8 ably results from increase in respiration ' oz. per square yard has been made from them. . rate with minute-volume. ' ' The lung condition resulting from the inhalation Per Cent Retention is unaffected by 1. Volume per respiration. 2. Vital capacity, of this dust is known as asbestosis and resembles silicosis in its main clinical aspects, but differs due to the enhanced rate of development. Under average' 3. Relative humidity. ' industrial conditions the length of employment in The same 'investigator found'that the percentage of fatal cases is only about one-half that which is usual 60 i ' ' JU N E, 1944; H EA TIN G AND V E N T IL A T IN G om ul brcitiuB.] 1 60% at a C06.I 8- tie Tetenticaj :tration dropp^j Sly approach I Oration and d* ;d by many j. relation^ ximmonly snds the accep. '>c foot at tit >tion for pnrt r foot for dutu idence suggetu :ot dusts which which is widely o a value such Tration by the ),000; this rule r foot as the us dusts, odition known ation of silica, the ability to the subject of ilicosis are at controversy, of complica`tioning of the ation of scale er device. In uids are sepahe deposit of iveness as an es sufficient!} he transfer of for which the lung is a sur fed from the :aT tissue rtventually the --death from silica in the ' represents, ng composimately 43 % 3xide of iron srk particles are of such less than 8 them. e inhalation d resembles differs due der average 'loymenx in rich is usual I* silicosis. It is estimated that there are in the Hiked Sutes approximately 10,000 men exposed to a hazard as a result of work in the insulating, jjfcettM doth, and similar industries. As is true of d* silicosis exposure estimates, this figure does not tjkt into account the number of persons exposed as , result of employment in the process industries rfatre asbestos finds use, under various trade names, filter aid. In one respect asbestosis is less dead er than silicosis--that is, there is seemingly a lower iscepribility to the supervention of pulmonary tu berculosis. The danger of contracting the disease is tppirently not influenced by either age or sex. Like silicosis, it is incurable and progressive; a case is re ported of a patient who was exposed to asbestos dust forone year and whose sputum showed the presence of asbestosis bodies fourteen years later. Very few data are available on the relation of dust concentration to the incidence of the disease. No minimal safe concentrations have yet been set up tad information is scant as to the conditions in those plants where a hazard is known to exist. It has been determined, however, that the asbestos dust en countered in fabricating plants is free of silica when air is floated at the breathing level and that the danger of the dust increases as the quality or length of the fibers increases. Miscellaneous Siliceous Dusts Many siliceous dusts other than quartz and asbes tos have been carefully investigated. Talc--a sili cate containing 62% silica--has been shown to be responsible for a form of pneumoconiosis when in haled in large quantities. One group of investigators report that 50% of the talc workers whom they ex amined were affected and about 12% had tubercu losis. The same report shows that talc containing 10% tremolite is much more dangerous than talc containing 40% tremolite, but an explanation is lacking. The action of cement on the lungs is not definitely known. German investigators say that it produces 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 facturing plants; absence from work was also twice a$ frequent. Yet animal experiments show that ce ment like limestone and gypsum produces an ad sorptive reaction; the dust disappears from the peritoneal cavity without the production of scar tissue. Slate (1/3% quartz) in concentrations of 700 million particles per cubic foot produces a fibrosis *nd pneumoconiosis, but few cases have been known to progress seriously. On the other hand, there is reason for believing that clay and slate dusts are responsible for a high incidence of tuberculosis. Italian investigators have studied the dust hazard mconon spinning mills and report that the silicosis hazard is apparently negligible. Mineralogic anaiy- V T IL A T IN G HEATING AN D V E N T IL A T IN G , JU N E, 1#44 sis of such dusts brought to light the interesting fact that their composition is similar to that of the soil in which the cotton was grown. Non-5ilie*out Dusts Apparently there is a great difference of opinion as to whether or not non-siliceous dusts are harmful either to normal or tubercular persons. The data are so scant that a review of the literature must con sist essentially of a catalogue of the few and scat tered investigations that have been made of particu lar dusts. General conclusions can not be drawn and an extension of available data to dusts of even the tame 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 conclusion that persons who have had 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 incidence 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 reported 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 claim 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, calspar, emery, colloidal coal (in 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. 61 Sir ALPHABETICAL INDEX OF ADVERTISERS $ J \4 Hi H * i i * i > 'll A Acme Industries .......................... 43 Air Conditioning Engineering Co. 116 Air-Maze Corporation .................. 40 Airtemp Div. Chrysler Corp........ 4 Airtherm Mfg. Co............................ 105 Aleo Valve Co................................11-24 Allen Corporation........................ 13 American Air Filter Co., Inc........ 27 American Blower Corp................. * American District Steam Co........ 119 American-Marsh Pumps, Inc........ American Rolling Mill Co............ 14 Armstrong Machine W orks......... 10 Automatic Products Co................. 10S B Badger Mlg. & Sales Co............... * Baldor Electric Co........................ 105 Barber-Colraan Co.................. 88 Bell & Gossett Qp.......................... 35 Bethlehem Steel Co...................... 97' Breidert, G. C., Co........................ Brooks Equipment Co................... 114 Bryant Healer Co.......................... 32 Buffalo Bolt Co............................. 7 Buffalo Forge Co........................... 45 Byers, A. M,, Co............................. C . Carey, Philip, Mfg. Co................... 34 ii.. Carrier Corporation ....................... 33 Cash, A. W., Valve Mlg. Corp. . . . 12 If Chrysler Corporation .................. 4 Classified Advertising .................. 116 Continental Steel Corp................. * % Crane Co........................................ 31 Crown Iron Works Co................... 115 i- Curtis Refrigerating Mch. Div. of . Curtis Mfg. Co............................ 42 r-I! ' * D Detroit Lubricator Co................... 6 * Detroit Stamping Co....................... 119 Dravo Corporation ....................... 93 Dunham, C. A., Co...........................103 i * 'I IIuJV r- F ill ' * E Economy Pumps, Inc..................... * Electric Auto-Lite Co............... 112 Elgo Shutter & Manufacturing Co. * Ellsworth Pipe & Supply Co........ 17 Emerson Electric Manufacturing Co............... .*.......................... * p - Freeman Stoker Dtv. Illinois Iron i' & Bolt Co. .................................. I l l 120. G General Controls Co...................... 107 General Electric Co...................... * H * Hays Corp...................................... 117 Henry Valve Co............................ * Holcomb & Hoke Mfg. Co............ 39 Howell Electric Motors Co., Inside Back Cover I Ilg Electric Ventilating Co........... * Illinois Engineering Co., Inc. . . . . * Illinois Testing Laboratories, Inc. 114 Iron Fireman Mfg Co................... 101 Penn Electric Switch Co.............. Porter, H. W.( & Co., Inc...............US Powers Regulator Co..................... U7 Propellair, Inc.............................. ' * R ' Reznor Manufacturing Co............ 1- Ric-wil Co. ............................. I S Sail Mountain Co........................'. * Sarco Company, Inc...................... * Sarcotherm Controls, Inc............. ti Smith, H. B., Co., Inc.................. Somers, H. J., Inc...................... Star Electric Motor Co................ 21 Superior Sheet Steel Co........... . * Johnson Fan & Blower Corp........ 36 Johnson Service Co. . . . . . . Back Cover Kewanee Boiler Corp.................... 8 Korfund Co., Inc.' .............. ......... 119 Ladish Drop Forge Co................... 29 Leland Electric Co........................ 23 Link-Belt Co................................... 16 M Marley Co.. Inc.............................. Mario Coll Co................................. 41 Marsh, Jas. P., Corp...................... 49 Mereold Corp................................. 37 McCord Radiator & Mfg.Co............ 117 McDonnell & Miller ..................... 35 Minneapolis-Honeywell Regulator Co...................... Inside Front Cover Modtne ManufacturingCo.............. 42 Mueller Brass Co......................... 26 - N Nash Engineering Co.................... 50 Nelson, Herman, Corp..................18-19 T Taylor Forge & Pipe Works...... E Thrush, H. A., & Co..................... U 1 Todd Shipyards Corp, (Combus tion Equipment Div.) ............. 24. Trane Co. . k.................................. 12 Trerlce, H. O., Co........................... US Tube-Turns, Inc............................... 2 Tuttle & Bailey, Inc....................... 4 V U. S. Machine Corp..................... United States Air Conditioning Corp. ........................................ * United States Radiator Corp....... g. W Wagner Electric Co........................1` Want Advertisements .................. Ilf Webster, Warren, & Co. ........... Weeks, B. H.............................. ^ Westinghouse Electric it Manu- . tacturing Co. ..................... 4MT White Rodgers Electric Co.......... ' Whitlock Manufacturing Co. ... Wing, L. J., Mfg. Co.................. Worthington Pump & Machinery Corp............................................ Owens-Coming Fiberglas Corp..; 99 P Pacific Steel Boilers ........... 5 Patterson-Kelley Co., Inc........... * Peerless Pump Div., Food Machin ery Corp...................................... 110 Y Yarnall-Waring Co............... 109-114-1U York Heat Div., York-Shipley, Inc. Young Radiator Co.....................:. IB ->i AdTni*c2nnt appeared io preceda* iicof.- JU NE, 1944, H EA TIN G AND VENTILATIHG