Document O3n0y3Kd0dKa3O70Dab4wZq4v

FILE NAME: Metropolitan Life (ML) DATE: 1939-1940 DOC#: ML221 DOCUMENT DESCRIPTION: Dr. Lanza Publication on Dust Risk and Underwriting 1412 J2 ~ e W eekly Underwriter Life Insurance Department JU N E 8, 19-10 Underwriting A sp ects of the Industrial lite Dust Hazard - By A . J . Lanza, M.D.; Assistant Medical Director, and R. J. Vane, Statistical Bureau, Metropolitan Life AddressBefore Medical Section of American Life Convention, Colorado Springs, Colo., June 6 Otions U R knowledge of health hazards re sulting from exposure to various -kinds of dust"in industrial .'occupa is based, on .observation and clinical studies of workmen exposed to these dusts, and upon noting .the'results of the acdon of these same dusts upon experimentalanimals. The former me'thod goes back for centuries and our earliest'conceptions o f the harmful properties of dust .were based, on first hand 'observation. Many pi these conceptions were erroneous. It is only in the past twenty, years that any thing like a comprehensive knowledge of dust diseases has been attained-^due first to the perfection of the -X-ray as a means of diagnosis, and the development o f successful laboratory technique for conducting tests on experimental animals. . . . ... 1N ow we have arrived at a point where in tensive studies, both clinical _ and experi mental, conducted in this :country and in other countries, have resulted in a crystaliza- tion of our ideas. In the English speaking world, the outstanding contributions to our knowledge have come from the South African .Institute for Medical Research-.and the Miner's Phthisis Prevention Committee in.Johannesburg; from various official agen cies in England and Australia,. in Ontario, Canada, and in this country, especially the United States Public Health .Service, the - United States- -Bureau, of Mines, and the .Saranac Laboratory. In presenting this discussion of industrial dusts, their effects oh workmen'exposed to them, and the bearing that this subject has on life insurance underwriting, we. have at tempted to summarize what should be the insurance attitude, based on the present state o f our knowledge.. Briefly, the present con cept regarding industrial dust'hazards-is'as follow s: Orjranic dusts, of which the dust arising in textile operation* is an .mramnle. do not cause'any-IpiCiflfi pulmonary disease. There is no clinical 'nor. ikpiflfHenCST evi dence to the contrary. Winds- u Sufor- gamcTU&SUnu,' is considered in connection with mineral dusts.. Organic dusts at times may cause an allergic reaction and also irrita tion of the upper air passages. They do not cause protracted disability nor death. In this classification may be included cotton, wool, silk, sugar, flour, starch, wood, tobacco, and leather. It is true that some occupations in which is involved exposure to organic dusts mani fest a tuberculosis mortality .rate higher, than the average. Formerly, it was thought that this undue prevalence of tuberculosis was due to the occupational dusts but the dust studies of recent years have demonvstrated that, mosdy, organic particles are too large to penetrate' to the pulmonary, tissue and when they do, they are absorbed without producing any specific inflammatory reaction. Nor is much credence given nowadays to the idea that organic dust particles convey tub ercle bacilli :to the lungs and thus, cause tuberculosis. M etallic'D usts Here the situation is not unlike that of organic dusts. The prevalence of pulmonary disease among workers in certain occupa tions exposed to metallic dusts gave rise to the theory that metallic dust was a fruitful souree of tuberculosis. Such diseases as "grinder's rot" were recognized clinically, long before the era of modem diagnosis and laboratory research. Metallic particles in the form of fumes may cause such reactions as zinc chills or brass founder's ague, which . are more in the nature of an allergic reac tion. The .-pulmonary disease which afflicts grinders and- buffers is silicosis and not in any way a result of exposure to metallic dust Metallic dust particles are mostly large and heavy (that is, comparatively speaking), consequently do not penetrate to the lung, in many.instances, and when they do they are either absorbed or -remain fixed and inert in ., the tissues. From' an underwriting stand point then, the hazard of'metal dust is the hazard of- such silica dust as may be asso ciated with i t . . . Coal For many-years there has been a belief that coal miners had less, tuberculosis than the average for wage, earners and, on the other hand, miner's asthma has been recog nized as an occupational disease of coal miners. Here again, recent studies have clarified the situation to a considerable' ex tent. Bituminous or sort coat miners do not have an occuptional pneumoconiosis of a disabling quality. Their lungs bccotrfc pigmented ireta coal dust but they do not develop a true, fibrosis. For anthracite miners, the pictsre is quite different and the reason is that an- thracite mining includes exposure not coir to coal dust but also to silica. Disabling miner's asthma was shown by the Unites States Public Health Service study of 1935 to be a type of silicosis, to -which the'term, anthraco-silicosis is properly applied. Anth racite seams are often found in country rode which' contains a considerable'amount of free silica and, as in other silica dust ex-' posures, the development o f pulmonary fibrosis was found to 'be proportionate to tlx amount of silica m the coal dust and the length of exposure The incidence of tuber- . culosis among anthracite miners is very high. , Qinical .pulmonary tuberculosis was found in. .J IS per cent of those with early anthraca-silicosis and in 43 per cent of those with advanced anthraco-silicosis. Service upwards of twenty to twenty-five years was asso- 'ciated with a tuberculosis rate of 14 per tent . -among regular miners and 37 per cent among those with a number of years as rock work-, ers. Animal experimentation, with both bituminous and anthracite coal dust, free from associated silica, produced no specific reaction. Non-Siliceous Minerals There is no evidence that non-stliceous minerals produce any pulmonary lii'w v . Gardner, at the Saranac Laboratory, tested upon animals such substances as diamond, aluminum oxide, rutile, marble, gypsum, ga-> lena, chalcopyrite. iron sulphide, zinc sul phate, fluorite, and dolomite. The sulphides and dolomite proved toxie but this affect is outside of our present discussion. Non-silice.ous minerals proved inactive in animals and there is no clinical evidence of specific dis ease among workers exposed to this tvpe of dust Artificial Abrasives Experiments with artificial abrasives demonstrated the incorrectness of earlier ideas that dust caused injury to the lungs, proportionate to the hardness and sharpness' of the particles. Artificial abrasives, ireamong the hardest substances known. Neither silicon carbide nor aluminum oxide produced any reaction resembling silicosis in experi- fri *tu 25 Toc Sc far Svt > '*sc *-ti f*Cl "S* . KSl & pr. L? r.D 1 *p `.de c ' 'c ~ t "i?t ri-T 1 j. i t 7 'i ? c i-.t : li:* ' PLAINTIFF'S EXHIBIT S & U k ). w .1 .>..! i 't '.--- ''r'S - 5 . / . C - t r l G H T L&v. iTt.f. *.v coof' tuta-t**. .N i. J un e- 8, 1940 1413 mental animals nor co workmen exposed to asbestosis. but most ot the atai cases have though eases wiii be seen occasionally that these dusts show any clinical symptoms or X-ray appearances suggestive o i silicosis. been complicated by other disease such as cancer and diabetes so that the extent to proceed to a fatal ter--'.nation without infec tion. which the asbestosis was responsible for Exposure to moderate amounts ot silica Silicates death is not clear. dust where the parttci: counts are in excess A considerable number oi silicate, dusts The pathology ar.d X-ray appearance of ot ten million docs not occur frequently at have been studied and their effects upon ex asbestosis arc entirely different from silicosis the present time, though it is cniy in the as: perimental animals, both by inhalation and and in the absence of a definite history of tew years that siiica industries have en injection, noted. They produce little or no exposure over a considerable period of time deavored to cope with their dust problem and reaction in the body tissues and what little . to asbestos dust, the diagnosis is difficult. A effectively reduce the amount. Such ex reaction some ot them do produce does not great deal ot success has been attained in posures produce definitely disease in from tend to progress. An exception should be controlling dusts in the plants where asbestos eight or ten to twenty or more years, in pro noted here regarding asbestos, which is con is fabricated so that it is not likely that as portion to the actual quantity of dust. The sidered separately. bestosis will ever become an important in incidence of tuberculosis is high and of those Nor is occupational exposure to silicate dustrial disease, as far as the number of who die of their puimonary condition, 7a per dusts accompanied by any such clinical pic cases is concerned. cent are tuberculous. ture o i disability and death as is. found in The scarcity of clinical data on asbestosis It is also possible to find degrees of silica silica dust exposures. The Public Health makes the prognosis doubtful. We have had exposure which, white producing definite siii- Service studied some talc mines in 193S. a small group of cases under observation for cosis evident on X-rays, will r.ot produce dis Only 66 men were exposed. Tuberculosis about ten years ar.d.some of these show a ability or death in an average working life morbidity and mortality rates were very high definite but slow progression, as far as can time. Mortality statistics are not broken in the county where the mines were located be judged from the X-ray films. However, down by industry to an extent sufficient to and the dust exposure was.'exceedingly se what the outcome may be remains to be seen. make available definite figures by degree of vere, running into hundreds of millions of These men are all working and showing no exposure. We must rely then on the clinical particles. Eight men showed advanced pneu ' signs of any disability. results obtained in industrial investigations moconiosis but tuberculosis was also present in most of them. It is conceivable that ex Silicosis which are conclusive enough for those indus tries studied. Our own impression is that posure to tremendous quantities of any min It may be said that there is a very general, even where the silica hazard is oi a miid eral dust, regardless of silica contest, might accord among the leading investigators and . type, the incidence of tuberculosis will be so overwhelm" the lungs that they could r.ot research authorities in the opinions and con higher than the average. It has been stated deal with the invading substance. Irrita clusions presented in the international con that where siiica dust contains caustic alkalies tion, inflammation, and probably infection ferences on silicosis. Such differences of also, the action of the silica is intensified would follow with disability in proportion. opinion as .may be ex pressed, from time to very considerably. The evidence here is Such isolated instances do not invalidate the time do not seriously affect the general meager. ' Other substances apparently have conclusions stated in the previous paragraph. agreement on the basic factors affecting the some inhibiting effeet upon the action of Asbestos cause, incidence, effects, and prognosis of silicosis. silica, affecting the pathological as wcil as the clinical picture. * Asbestos is the only dust of combined The effect of silica upon the lungs depends silica which is known to cause a definite on the nature and extent of exposure. That Prognosis m3.:. pulmonary fibrosis which may result in dis is to say, upon the quantity* of dust in the The prognosis is fair for a silicotic whose ability and death. Most of the asbestos fab air breathed by workmen, the amount o f free lungs are not extensively damaged ana who ricated in the United States comes from the or uncombined silica in the dust, the size is free of infection. Such persons have an mines, in Quebec Asbestosis. however, is _. of the dust particles; the presence of other increased susceptibility to infection and if not`found among asbestos miners, most o t . substances in the dust, which may modify brought into intimate contact with a case whdar~work" in 0frea~quames~~or pits, nor the action of silica, and the length of time of tuberculosis arc very apt to become tuber among men engaged in mining operations or duration o f exposure. ' The individual culous also. The outlook for the tuberculo- whereby* the asbestos is prepared for ship himself must also be considered. Previously silicotic is poor. Many cases are essentially ment and bagged, but among workers i n existing disease of the lungs, especially a chronic and may live for years. Others show fabricating plants. Only recently has an ex- ' tubercle infection, will influence his reaction . rapid, progression and die in from one to two plaualiuu IxuroiTetetl 16t tills anomaly. It to inhaled silica.. There may be other phases years--aiter-their- infection becomes active. would appear that not only is asbestos an of susceptibility about which we know little The importance of tuberculous infection exception in that it diners from other sili or nothing but in the main, it may be stated among persons exposed to silica oust brings cate dusts in its ability to cause- structural that individual susceptibility to the action of up a very important underwriting considera changes in the lungs but its action appears to silica dust is an acquired rather than a con tion, that is, where the worker in a siiica be mechanical and not chemical like the ac genital condition. . , occupation is in contact in his home with an tion of silica. If asbestos is crushed to fine In industry we find different types of silica open case of tuberculosis. particles, it will not cause asbestosis in cx- hazards. The severity of a silica hazard is The question is frequently asked whether p irin u nral i n i n l n f t r will athi-efne prndurc estimated on the amount, of dust in the air men who had worked ir. silica dust at cue any reaction elsewtltfe man in the lun g s ~ I f and this is expressed in millions of particles time but later changed to a job in which 'i its action wu i 111 OR nature ot sdica. the per cubic foot. The particles counted, are there was no exposure to silica might be ft effect would be more pronounced with smaller those under ten microns in size, though the considered, standard risks for life insurance ; pclaurdtiecslethsaitzetsh.e rCeloantisveeqluye.nlotnlyg, sGpiacrudlneserofcoans ptwreeseenntonope-inhiaolnf ais mthicartonit aisndthtehrpeaertmicilcer,obnes iefxatmheinyatpioanss.edWthheileustuhaelreinasruerannoceinpshuyrasinccael bestos produce their effect because the lungs that is mostly responsible for causing the statistics to prove the point one way or the are never at rest and the constant.movement disease. ..... other, there is every reason to believe that O provokes the fibrous reaction. Exposure to excessive quantities of pure a group of such men will not give a stand Like silicosis, asbestosis develops slowly, silica dust, that is, where the dust count is s ' mortality. T'ne usual type ot physical presenting the characteristic .symptom of in the hundreds of millions of particles per examination will not detect silicosis. The shortness of- breath. The number of cases cubic foot, is now rare. Isolated instances only way to be sure is to secure X-rays of of asbestosis. that have come! to autopsy is may be found as. in the case of a sand-' the lungs of such applicants and have them ' small but there are several cases on record blaster improperly protected. Such exposure interpreted by some one who has specialized in which death .was due entirely to the as produces a severe type of silicosis in upwards in reading films of this kind. bestos and not to any associated infection or of five years, even sooner in extreme cases. Silicosis is gradually coming under control. other condition! There does not seem to be With such extensive silica- damage to the T he aggravated cases seen twenty years ago any pronounced tendency to tuberculosis in lungs, tubercle infection is almost inevitable. ( Continued on Page 1417) V -si *TiA*-.* .Vr: S j f. s' iv is 3jl ji" iii :jT ?/J 'isS S 753 75~ fm JIStl S5 !<] 53 an 111 ns ZMl 10.1 ;0: sia tJ *0 ids ;OW| 51 30 9** 2A Wune-8," 1940 . i f --. L;. `SU R PL U S F U N D S Ji, M etropolian ............... 5309, ,717.567 l-4!.'Prudential! ..................309 392.460 *J, New York L ire........... 135 ,639.023 fc'E quiuble. N. Y........... .762.655 [frlcka . Hancock............... .961.337 ^IrTraytler* ...................... .902.795 K N trthyrestsru M u tu a l.. ,186.343 Mutual Lite* N, Y .. . ,852.202 F .t. A cuu U te .................... .855.402 f i t Pena M utual ................ #v,.944,720 l i t Mutual Benefit ............ 30.314.767 >U.`W jtem 4e S o u th e rn .. 25.383.923 U/Uasa. M utual ............. 27,,050.794 ;|C Providern M utual . . . . 19.374.230 New En f land M utual. 19.010.803 IlC Ufe In s . Co. of V a ... .956.930 IfcAser. N at'l. T e x . . . . . .533.244 It Coon. G e n e r a l........... .423.637 *ISC*Cona. M u t u a l ................ .020.498 l i t Union Central L ife .. .348.155 l i t ' Bankers Life, l a ......... ,599.738 :2L*:2iatioaal Life. V i . . . . ,224.492 | f `M w U s U 2t,Q 1.620 continenty re- 23. National Life & A c s... 24. Lincoln N a tio n a l......... 25. Equitable Life. l a . . . . 26. State M utual ............... 27. Phoemx M utuai ......... 23. Southwestern Life . . . 29. Kansas -City L ife......... 30. Fidelity M utual ......... 31. Jeiferson Standard . . . 32. Bankers Lite. N e b .... 33. Pacific M utual .a........... 34. Northwestern National 35. Guardian Life ............. 36. Reliance Life. Pa........ 37. Great Southern #........... 33. Monumental Life . . . . 39. Home Life. N.# Y .. .. 4 0 . Occidental. C a l if ...... 4 1 . Life & Casualty........... 4 2 . Continental. HI.............. 43. Central Life, la .......... 44. Columbian National . . 4$. Acacia M utual ........... 46...Calif. W estern Slates. 47. " Provident Life 5: Ace. 48. M utual T ru st ............. 0.431,570 5,941.165 5.777.602 3.625.3S 7.544.962 7.340.000 7,205,93* 6.468.839 6.300.000 5,799.129 5.672.956 5.457.913 5.269.459 5.171.696 4,733.020 4.569.137 4J00.63S 4.152.034 4.077.235 3.922.44J 3.373.551 3.529.063 3,412.797 3.295.000 3.233.576 3,231,713 49. Wash. N a tio n a l........... 50. Minnesota M utual . . . 51. Sun L ilt, M d............... 52. ColiitrioUs M utual, O .. 51. Ohio National ............. 5*. Guarantee M utuai . . . $5. Midland M utuai ......... 56. Amer. United. I n d , .. . 57. North Amer. ftcaaaur. 3$. Commonweal ........... 59. W estern Lite. M one... 60. Home Sencncial . . . . 61. Continental Amer. . . . 62. Mass. Sav. Bank......... 63. Pilot Lite. N . C-......... 6*. PanAmerean L i f e .. . 65. Generai A merican . . . 66. Old Line. W is............... 67. Baltimore L ife ^ ............ 63. Ohio State L ife............ 69. Presbyterian M in. . . . 70. Alliance Life . . . . . . . 71. Berkshire L i t e .............. 72. Farm ers & B a n k e rs ... 71. Business M en's. M o ... 74. New W orld L ife............ 3,253.323 2.066.703 3.045.994 2.703.393 2.672.773 2.373.074 2.570.341 2.500.000 2.413.961 2.333.353 2.350.000 2.348.435 2.321.712 2.293.596 2.235.976 2J44.S24 2.2*4.449 2.21I.27S 2.154.77t 2.074.617 1.363.971 1.359.775 I.340.9IS 1.334.663 1.303.9*9 1.799,790 75. Amer. Mutuai. la ........ 76. Cosomat L.fe ............... 77. Industrial L. \ it.. Ga. 7S. Protective Lite. A la... 79. Country Life. IV........... SO. American tannarci . . . 31. indunauoiis Lite . . . . 32. Amtcaoic Life ............. 3.1. Paul Revere Life......... 3*. FranUir. L . .^2 .:........ S3. Casual Life. Caio........ 36. Union La or L i t e . .. . 37. Orcson Mutual ........... S3. Monarch Lite. M ats.. S9. Loyal Protective . . . . . 90. Soutaiand U fe ........... 91, National Reserve . . . . 92. Illinois Bankers ......... 95. Volunteer aiate ......... 9*. Atlantic U te . V a .. .. . 95. Girard U fe. ?............. 9ft. Great Amer., T e x a s.. 97. United Life,Jr A c s... 93. Northern Life ............. 99. Mass. Protettive ......... tOO. Lutheran Mutual . . . . 1417 :.7:?.-;05 .i i i . -2a* l .55 7.717 11 it 1.5-5!.14 j 1.5 *. 7.225 l.*;2.2C6 1.470.457 1.44Q.42 5 i *9 nnj J7 2.US 1.544.325 l . 313.523 1.229.12* 1.501.507 :.3 0 i.:s 7 .2C0.577 .27*.233 ;.;57.:75 ;J 5 5 .7 2 1.242.220 1.-74.225 1.093.117 l . 332.501 1.263.910 1.232.765 ' INDUSTRIAL DUST H A ZA RD {Continued from-Page 1413) rarely seen now and the clinical picture .has changed with the .progress of dust-con ic;trol measures. The' trend is towards a t'-lessened-incidence of-new cases of silicosis. This improvement- depends upon the main-tenance o f constant vigilance in detecting un.juspected hazards and in supervising the efficiency of dust control methods aiter they have -been put into effect. It cannot be exrVeeted that this improvement will be reflected : m insurance mortality until a considerable ."period of time has elapsed. ---------------------..-..The conclusion seems warranted from l.c'inical and laboratory experience, then, that the only dusts which of themselves might fhave sufficient effect on the mortality of i workers exposed to them, so great as to require an extra premium charge for life in; sunnee, are silica and possibly, asbestos. Life insurance men naturally will turn to Synortility statistics for- confirmation of a ,Vinding so at variance-with the common bev: -lief, -long held, that exposure to all kinds of .-dusts is productive of a.high incidence of respiratory tuberculosis. To .the-layman it 5"seems only reasonable to suppose that the '^difficulty in breathing he experiences when ~texposed to large quantities of dust must -.tin some way affect his health, and that filling tfjthe lungs 'with foreign particles' must have "Injurious effects on them. The writings of V"eminent students of occupational mortality .statistics have served to strengthen this beHief.. Nearly all such statistics, show the ^mortality from respiratory tuberculosis among workers exposed to a wide variety of dusts `to be well above the average for all workers ^'included n the study. But, when these fig*;|ures are refined so far as is practicable to V.'tnake allowance for. factors other than dust, ,,'which may influence the - mortality from "tuberculosis of men employed in these oecu"pations, the importance of many, dusts as a-.causative factors becomes less evident. \ .,,"There is-a surprisingly large number of ' '.factors, other than dust,, any one of which .may be responsible for the high mortality "from tuberculosis among men in dusty trades. ' 'Some dusty occupations are carried on by "men recruited from the lower income classes, ; -among whom it is now known that apart en7*' :tirely from exposure to a specific occupP-;'" .tibnal hazard,"the death rate from tuber culosis,- is considerably higher than among persons in the higher income groups. The selection of certain kinds of work by the less robust workers is reflected in the high mor tality from tuberculosis of men in other callings. Racial and nationality groups tend to enter certain occupations, with the result that the peculiar susceptibility or relative immunity to tuberculosis of these stocks, colors the mortality picture of men in such occupations. These arc but a few of the many circumstances for which allowance must be made before conclusions can be drawn as to whether a particular dust is or -is not the responsible agent in the high mor tality found among men in a dusty trade. " Unfortunately there is, for the United States, no considerable body of mortality statistics sufficiently detailed to permit of evaluating separately some of even the most important-conditions affecting the mortality of men. in. specific occupations. Perhaps the .best statistical demonstration of the effect of different, types of dust on mortality from "tuberculosis is supplied .by two British au thorities. Dr. Edgar -L. Collis and G. Udhey Yule. These authors selected for study, from the occupations reported upon in "the -Registrar:.General .of England and Wales', report on Occupational Mortality covering the years 1921-1923, two groups of occupa tions--one exposed to silica dust, and the other to non-silica inorganic dust. The groups were so chosen that each had, as far "as possible, the same amount of dust ex"posure, physical effort, exposure to heat or to weather, or any underground environment. Part of the authors' comment on the results as regards respiratory tuberculosis is quoted: "For all ages (20.to 65) the comparative mortality figure (this figure is defined as the number of deaths that would have occurred in the Standard Population at the rates rul ing in the occupation) of the Silica Group is no less than 5922 against 163.5 for the Standard Population, i. e., the mortality is "more than three and a half times the normal. For the- Non-silica- Group, the Comparative Mortality Figure, although actually slightly higher than normal, at first sight hardly seems to differ significantly from the normal; nor would one's judgment be much affected if, instead of making comparison with the Standard Population, one had used the Social Groups III and IV, for which the re spective Comparative Mortality Figures are 159.8 and 164.2. But the summary figures conceal interesting changes with age. A glance at the figures (shown on Table 4 of their study), shows that in the Silica Group the ratio of mortality to the normal, theugh greater than unity even in the lowest age group, rapidly increases as age advances. In the Non-silica Group, the comparative mor tality is actually below normal up to age 35: it rises just above normal in the following age group: but as ages over 45. it is con spicuously above normal." The facts regarding tuberculosis were nor published in this report for each of the six silica occupational classes included in the study. We have, however, determined by reference to the report of the Registrar Gen eral, that each of the silica occupations had over twice the expected number of deaths. The extraordinary Iti.ch ratio of 1.150 per cent was recorded for tin and copper miners, while sandstone masons, cutters, and dressers had a ratio of 441 per cent. On the other hand, only the limestone masons, cutters, and dressers of the five occupations considered in the non-silica group exhibited a high ratio. 191 per cent. Like the English tin and copper miners. American- mctaL miners are exposed to a: serious silica hazard and have an'inordinate mortality from respirator/ tuberculosis as will be seen by reference to Table 1. In this table are given the ratios of actual to ex pected deaths from tuberculosis tor a num ber of occupations exposed to dust and re ported upon in the Joint Occupation Study. 1928, and in the Occupational Study, 1937. both published by the Actuarial Society of America and the Association of Life Insur ance Medical Directors. In the period 19131926, the number of deaths from respirator/ tuberculosis among metal miners was over eight times the number expected on the oasis of death rates by ages prevailing among standard ordinary lives in the same years. In the latter study covering the years 1923 tc 1936. the ratios were even higher--over 11 times' as' many deaths were recorded for metal miners as were expected on the basis of death rates among standard lives in these years. While the actual number of -deaths for each separate metal mining class was rather small in both investigations, ar.d consequently the ratios are subject to a large margin of {Continued on Pagt 1420) U-r'-rO 1420 INDUSTRIAL DUST HAZARD (Continued from Page 1417) error, nevertheless it is interesting to ob serve that they were quite uniformly high for copper .miners, gold and silver miners, and lead and zinc miners. The situation as regards iron miners is interesting because it was thought for a long time that they had little or no exposure to .silica. More recent studies show that there is. actually a moderate degree of silica hazard w hich'. produces silicosis in upwards of twenty years. However,: in both insurance studies there were too few deaths from respi ratory tuberculosis to permit definite quan titative conclusions therefrom. A great many-workers in raining occupa tions, it must be borne in mind, are common laborers-among"yvhora we should expect a much higher, mortality from tuberculosis thaw among standard ordinary policyholders. From the limited data available for unskilled workers, from-these studies it would appear . that the tuberculosis' death rate for this class o f workers runs between two and three times the. rate of standard ordinary business. Thus it is clear that even when-allowance is made for-the important factor of social-economic class; the death rates.for the metal miners are extremely high. . 'Coal, miners' in. different' sections of the country present an' interesting contrast. Among the bituminous miners, exclusive of the Pennsylvania miners, the mortality from tuberculosis was over V/i times that on standard ordinary miners, a low ratio for this-type of worker. .Pennsylvania miners, on'"the other hand, most of whom were em ployed in'.the anthracite field, had a very high'-ratio-of: actual' to expected deaths-- 'well-over 300 per cent. Anthracite miners, as we have stated, are exposed to an appre ciable amount of' silica dust, which accounts for. their relatively unfavorable position. No dusty trade has received more careful .' U nderw riters, . . 1 agency managers, r home-office men: - For.the first tune, the whole subject of safeguarding life insurance proceeds .has been reduced to readable form and . . substance for easy assimilation and ., practical application. - . -Safeguarding .; '. L IFE INSURANCE PROCEEDS By W.' J. TFheeler and T. L. Todd .. Here. - in simple fashion, are ex plained the desirable:objectives to be ! attained by safeguarding life insurance estates; as well as approved practical ' plans of distribution-of insurance pro- ' ceeds. '. I - la tk* k w a t 1 U H lr.-auT-nk. m -- dial! J. Imtm tUnpl* UtlUai iltMt kittk wpUk tk* IwBf am MJ -- lUte t*. Alikmk . a iJ--k*k, It U pk*4 4tk p*r<aJi Ultf Idoai for ov+rf to ak*rb ! kl# mI* S2.50 PoitpoM Vp)C E S ttfelp THnlitrtDrtlxr ' 80 Maiden la n e New York The W eekly Underwriter study in the United states than that oi granite cutting. Long recognized as a dan gerous trade, it has beer, found time and again to take a heavy toil in deaths from tuberculosis. The amount of free silica in the dust breathed by these workers is very large. In the years 1925 to 1936, the mor tality trem tubercuiosis among granite and sandstone cutters was the highest recorded is indicated by the higher mortality tuberculosis among exposed workers . ' age 45. About ail that car. be said c point irem the united American ii:"e , ancc company experience, is that the tu^.cuiosis death rates ter grinders, metal pciisl'.crs, ar.c butters who are exposed to borganic dusts, most of which co net cectax a large percentage of silica, are act high, for any oi the -groups of insured lives having in mir.d the ccor.omic status of that- studied. There were more than 25 times as workers as compared with the average ore;, many deaths from tuberculosis as expected; nary policyholder. Lime, cement, anc a.-tii- whereas in the earlier years, there were eiai stor.e workers had a quite favorable nearly ten times as many deaths as expected, mortality. Tac very high ratio for march based on a small exposure. Marble and lime and limestone cutters, however, may be sug stone cutters did not show anything like as gestive o f some untoward infiuer.ee. Dr. high a ratio as the granite and sandstone cut L. U. Gardner a: Saranac Lake, found tbu ters. There were ten deaths where one was animals dusted with marble dust by inhala expected in the years 1925 to 1936. tion, developed little reaction,. but became It can be but regtetted that there are so few mortality statistics ior occupations ex posed to dusts other than silica. Grinders temporarily more susceptible to infest:: with tuberculosis. The increased susceptibil ity was not marked. of metals, most of whom for many years have been using composition wheels in place of the old sandstone wheels, and consequently have had a little or no exposure to free silica, experienced a relatively low extra mortality from tuberculosis in both studies, based, however, on a small exposure. An interesting point to be noted here is that this occupation also offers exposure to- metallic dust. It would appear that neither the dust from the composition wheels ncr the metal dust has produced excessively high death rates- from tuberculosis. Buffers and pol ishers, a somewhat similar group, also ap peared to have a low extra mortality from tuberculosis in the years 191S to 1926. .. Cement and Lime Workers The three occupations in which there is exposure to organic dust had from two to two and or.e-half times the number oi tuber culosis deaths expected.. Even allowing ter the economic position ot these groups as compared with ordinary policyholders j s erally, the mortality is nigh. It is dimes: to see in the light o i present clinical knowl edge, how it is possible to account for the excess mortality on the score o f damage a the lungs caused by such dust. Mortality findings, then, are still cot b complete harmony with clinical and labora tory findings. But from a practical under writing standpoint, it may be said thr.t r,hi only dust which ot itself might 5-, the total mortality, by increasing Cement, lime,- and.artificial stone workers dence of tuberculosis, as to require an vU i 'were reported upon in both the Joint Occu premium charge for life insurance, is fret pation Study and the Occupational Study, silica. W e have no mortality data for as but the number o f deaths from tuberculosis ' bestos workers but, it may well be that ex was in each instance less than the number posure to asbestos dust m large quantitier required for separate tabulation. This fact will also be found to produce a high me.-- in itself is significant although it does not tality. I mean-necessarily that the death rate from ' tuberculosis w as below the average.. Never theless, from the facts presented, in these studies, it is quite evident that the tuber culosis death rate for'this occupational class was comparatively low. Baldwin' s 1 N ew Y ork Insurance Law Annotated Three groups of male workers exposed to organic dusts are included in the table-- "Perpetual Revision Edition" upholsterers, cotton- mill operatives, and is the one authority on New York woolen mill operatives. The ratios for all of these classes run about 2CO-per cent, based on small exposures. It must be admitted that these occupational Insurance Law. It contains: The Insurance Law mortality, statistics are meagre and do not permit of very definite conclusions regarding the effects of specific dusts. So far as they go, they fully substantiate clinical and labora tory findings regarding the injurious charf acter of silica dust. The death rates from respiratory tuberculosis for men in occupa A ll miscellaneous statutes relating to Insurance Exhaustive annotations Insurance Department rulings Attorney General opinions " Common-Sense" index tions where there is a serious exposure to silica dust are so high as to leave no room K ept to date for doubt that silica is the offending agency. Price S 2 0 " Contrary to clinical and laboratory find Including -1940 Supplement ings, however, the mortality statistics, pre sented by Cottis and Yule, suggest that long continued exposure to non-sillceous inorganic dust has an-injurious effect on the lungs as <EfjetSSUeklp IHnberb':vip 80 Maiden Lane New. - ' - t ' i * A '' Vjr~* *** i'i 1 ' j i ~ flu mfi a i. - aV IB UXDLRW7UTIXC ASTECTS - DUST HAZARD * . 1 the me physician, tbit II was rnposslble to come lo any definite cn - elusion id ay, "this min died of asbestosis," when bis' previous disability certificates showed fiat be bid myocarditis or high blood pressure or canter or diabetes ar pulmonary .tuberculosis. The pathology and X-ray appearance of asbestosis art entirely different from silicosis and In .absence of a definite birtory of exposuft 'eve/ a considerable peced of time to asbestos dun, thr diaf- * difficult./A~Tre3t deal of success bas been attained in candusts in'the plants wriere asbestos is fabricated so that it is dy that asbestosis will ever become an important industrial as far as the number tf cases is concerned. T scarcity of clinical ra on asbestosis mates tie prognosis doubtful.- "We base bad a xmal group of cases under observation for about ten yean -- there were riginally, I think, some sixty odd men . j in this group and we 'nill ban fifty of them where we can get at them -- and some of these shor a definite but jJow progression as far j as can be judged Irons the X<ay films. However, what the outcome may be remains to be seen. These men are ail working and show xso signs of any disability. In the meantime tbt plana have been cleaned up so that these men are not exposed now to hordinate quantities of asbestos dust, so it is difficult to say what would have bee: - the progress of their disease had their working cnndiio&s remained the same. SILICOSIS It may be said that them is a very general accord among the - leading investigators and research authorities in the opinions and con clusions presented at the international.canftsencts on sfficosia. (Johan-.. " nesburg, Avgust,"1930; Cearva,`'August,and-;Septmber, 193SJ Such differences of'opircion as may ce expressed from time to time do not seriously affect the general agreement on the basic factors affecting the cause, incidence, effects, aai prognosis of silicosis. j The effect of silica upon the Junp depends on the nature ir.d j - len t of exposure.' That is to say, vpoa the quaatity of dust in the I air breathed by workmen, the amount of free o? uncombined silica i . in (he dust, (be size of the durt panicles, the presence of other sub stances in the'dust which mar modify the action of silica, and the length of time or duration of eposure. The individual himself must also be considered. Previously existing disease of the lungs, especially a tubercle infection, will influrare his reaction to inhaled silica. There * may be other phases of susceptibility about which we know little or 4 y ^T X( * J . JLJL, r " ! V' I , * I HI imnF.ltWRlTtNO ASPKCTi.DUST HAr.ARD font particles of one (o two and three microns In their largest diameter1, that those partirles h*d no physic! characteristics In the ordinary true In which we opply them. Artificial abrasives are among the hardest miniantes known, Neither tilicoo carbide nnr aluminum oxide pro durrd any reaction resembling silicosis In experimental animals nor do woikmen exposed to these dusts show any clinical'symptoms or X-ray I'pearancrs suggestive of silicosis. ` / SfLI CATES A considerable number of silicate dusts bate been studied and their effects upon experimental animals, both by Inhalation and Jnjec* lion, noted. They prodocclillle nr no reaction in ll*e body tissues and what little fraction some of them lo produce does not tenet to ptogrrss. An exception should be noted here regarding asbestos, which Is con* shirred separately. Nor Is ncrnpallona! exposure. In silicate dusls accompanied by any such clinical picture of disability *M death as Is found In silica dust . esf>osmes. The Public llrahli Service studied some talc ndnrs In I9JS. Only 66 men were ei|octl. Tuhcrtulnds morbidity and mortality tatrs were very high In the county where'the mines were tocaltd and the dust exposure was exceedingly xevrrc, running -Inin hundreds of millions nf particles. Eight men showed advancer! pnrumoconlosls hut tuberculosis was nlso present In most of them. It ft conceivable that expo,re to tremendous quantities at any mineral dust, regardless of silica-content, might so oveewhelm the lungs that they could not rleal with the Invading mh.xtmwe. Irritation, Inflammation, and prohaldy Infection would follow with disalrilily In projection. Such Isolated Instances do not Invalidate the ranehtsinns slated In the previous paragraph. ASDESTOS Asbestos Is the only dust of combines! silica which Is known to cause a definite pulmonary fibrosis which may resid In disability and death. Let me make that point cf^xr. When we talk of silicosis nod the types of dust that produce Mtimsts, we mean dusls that contain ilica In a free or tincnmblnrd stale, FIOi. When the silica Is In the form n| silienn carbide <<f magnesium silicate or Iron silicate that Is Vh.it wr mean by rotnlilited filiea. The combined silicate Shuts, as t have just mentioned, do not produce any pulmonary disra-.r, with one exception, ami that one exception Is asbestos, which Is a li*dr.itri| noeric.'itim silicate mixture, with a little Iron In ft. .'foil uf tl>r vhritns fabricated in the United Sla'ts comes from the ndnes In  >- . . . . * 1 ##\ ' . v * A. J. LAKZA, ll.D . ft It. J. VANK .s;.>* . "'* . \ Qurbtc Asbcstosls, however, Ij not found among a?t*jtoj in ii.-i\ most * of whbm woik in open quarries or niii, nor imnn? mm nacc<f"tlf mrHtff| operations wlKarcby lire asbestos Is prepared for shipmenT and tnrpflttt, but nnwmg wotfccrii In fabricating plants. Fabrication, you wlH~* understand, being In the nature of a textile process. Only recently has in explanation t>cn offered for this anomaly. It would appear that hot only* Is asbestos an exception In that It differs from ulhrr sili cate dusts In Its ability to cause structural changes In the lungs but Its action appears'to be mechanical and not chemical like the action of silica. II asbestos Is crushed to fine particles, It will not cause ashes- tosls In est>erin>enUl animals nor will nsbestus produce any reaction elsewhere than in the lungs. II its action were in ll>c nature nl silica, the etirci would be more pronounced with smaller particle sires, in other words, Gardner established that the Intensity of a silica reaction upon animals depended upon the smallness nf the silica particles, 1*. rause, lo sum it up lAlefly, the finer the silica particles, the greater Is *lhc surface exposure which ads trjton the pulmonary tissue.* Aslrestos particles, below a certain sire, do not produce any effect tin e*|erlnirntal animals. Furthermore, you can procure a silicotic fraction, the typical sillcellc nodule, In any organ by Injecting pre-. pared silica. You car) gel silicosis of 0 liver or of the spleen or dscwheie. Ftnt you cannot produce any reaction In animals with asbcslus anywhere rarept In the lungs, ami then only If ymir par ticles are sufliclrnlly.large. Consequently, Gardner cnnchulrs that the relatively long spicules of asbestos produce their effect brcau<e the luog.s arr never at rest and the constant movement provokes the fibrous tcactlon. * i Like silicosis, asbeslosls develops slowly, present big the charac teristic symptom of shortness of breath. The number of cases of ashes- tosls that have come lo autopsy Is small .but there ate several cases on record In which death was due entirely to the asbestos and not lo any asaaciated Infection of other condition. There does not seem to be aoy pronounced tendency to tutierculosls In ashestnsts, but mcsl of the fatal cases have been complicated by other disease surh as cancrr and diabetes so that the c'atrnt lo which the aslreslosis was tcjponslble lor death Is not clear. ( made a mlhrr exhaustive atudy I few years ago of all ihe Insurance certificates that I could find In which aslv-stns was given as the cause ol death ami then followed up Ihe previous history uf ihc>e prople and got their mrdirnl certificates when they wrre ou dhahiiity. Tin* diagnosis given on the disability certificates was usually so at variance with ' the diagnosis given " \on the death certifi'stcs, uftrn f>Y * PROCEEDINGS - . * OF THE " t h ir t ie t h a n n u a l m eetin g OF THE . . MEDICAL SECTION ' OF THE MERICAN LIFEj CONVENTION * . *3? *S k * ` 1940 OFFICERS ' MEDICAL SECTION . C h a ir m a n -- E h _ A- J. R o m n s o n , Medical Director, Connecticut General Life Insurance opipan} Hartford, Connecticut. a m n e n --D*- W. T. BuACtrrotD, Medical Director, Commonwealth Life Insurance Com' pany, Louisville, Kentucky. . , Secretary--Dru B. F. Btxd, Medical Ditectot, National Life fit Accident lmurar.ee Company, Nashville, Tennessee.' Memfcrr o f Board o f Managers--D x .T . H. D ic k so n , Medical Director, Minnesota Mutual Life Insut' ance Company, S - FauL Minnesota. Prorom OETLdh^DJupTTVIN?^'rsT0N Medical Directe), Mrdrai Life'Assurante Go. of Canada* > > T} *1 t r i - 'r 4 i \ t 4 > i iI* r t k.* ! . Id* `V J. - * % / li: - I; T j- \ t . h* PLAINTIFF'S EXHIBIT irU c - PLA IN TIFFS EXH IBIT I f i S T O O M L -H n b Z . \ 438 A. J. LANZA AND R. J. VANE (28) Iron foundry workers show highest percentage of deaths from pneumonia, Statistical Bulletin, Metropolitan Life Insurance Co., March, 1928, 9 ,3 . (29) Bloomfield, J. J.: Engineering aspects of industrial epidemiology, Indust. Med., 1938, 7, 7. (30) . Kibbey, C. H.: Pneumonia and tuberculosis among industrial workers, Am. J. Pub. Health, 1937, 2 7 ,6 . (31) H aythorn, S. R ., and M eller, H. B.: Pneumonia, Ibid., 1938, 2 8 ,483. (32) T hompson, L. R ., Brundage, D.' K ., R ussell, A. E., and Bloomfield, J. J.: The - health of workers in dusty trades. I. Health of workers in a Portland Cement ' Plant, Pub. Health Bull. 176, U. S. Pub. Health Service, April, 1928. (33) R ussell, A. E., Britten, R. H., T hompson, L. R ., and Bloomfield, J. J.: The health of workers in dusty trades. II. Exposure to siliceous dust (granite industry), Pub. Health Bull. 187, U . S. Pub. Health Service, July, 1929. t :; w INDUSTRIAL DUSTS 437 (4) Whitney, J essamine S.: Death rates by occupation, Natl. Tuberc. Assn., June, 1934. (5) Registrar-General's Decennial Supplement: England and Wales 1921, Part II , Occupa tional mortality, H. M. Stat. OS., London, 1927. (6) Joint Occupation Study, Actuarial Society of America and The Association of Life Insurance Medical Directors, 1929. (7) Occupation Study, Actuarial Society of America and The Association of Life Insurance Medical Directors; 1938. (8) Sayers, R . R ., Chairman: Report of the Committee on the Prevention of Silicosis through Medical Control, U. S. Dept. Lab., November, 1936. (9) Sayers, R . R., Bloomfield, J. J., D allavalle, J. M;, J ones, R. R ., D reessen, W. C., Brundage, D. K., and Britten, R. H.: Anthraco-silicosis among hard coal, miners, Pub. Health BulL 221, U. S. Pub. Health Service, 1936, p. 85. (10) National Tuberculosis Association: Framingham community health and tuberculosis. demonstration, Framingham Monograph No. 10, July, 1924, p. 69. (11) Sydenstricker, E., and Britten, R.. H.: The physical impairments of adult life, Am. J. Hyg., 1930,11 ,89,100. (12) Britten, R. H., and T hompson, L. R.: A health study, of ten thousand male industrial workers, Pub. Health Bull. 162,1926, p. 161. (13) Gardner, L. U.: Reaction of the living body to different types of mineral dusts with and without complicating infection, Tech. Pub. No. 929, Am. Inst. Min. & Met. Eng., May, 1938. (14) P edley, F. G.: Asbestosis, Canad. J. Pub. Health, November, 1930. (15) M iller, J . W., and Sayers, R. R.: The physiological responses of the peritoneal tissue to dusts introduced as foreign bodies, Pub. Health Repts. 49, January 19,1934. (16) Collis, E. L., and Yule, G. U.: The mortality experience of an occupational group exposed to silica dust, compared with that of the general population and a n , occupational group exposed to dust not containing silica, J. Indust. Hyg., 1933, 75,395. (17) M acklin, E. L., and M iddleton, E. L.: Report on the grinding of metals and cleaning of castings with special reference to the effects of dust inhalation upon the workers,-' U. K. Home Off., H. M . Stat. Off., 1923. (18) Collis, E. L.: Industrial pneumoconiosis with special reference to dust phthisis, Milroy Lectures, 1915; reprinted by H. M. Stat: Off., 1919. (19) D rinker, P.: Causation of pneumoconiosis, Harvard School of Public Health, 1937. (20) Carleton, H . M .: The effects produced by the inhalation of hematite and iron dusts in guinea pigs, J. Hyg., 1927, 26, 227. (21) Health protection in welding, Industrial Health Section, Metropolitan Life Insurance Co., (b) 513 LAV. (22) D oig, A. T ., and M cL aughlin, A. I. G.: X-ray appearances of the lungs of electric arc welders, Lancet, London, 1936,230, 771. (23) E nzer, N ., and Sander, O. A.: Chronic lung changes in electric arc welders, J. Indust. Hyg. & Toxicol., 1938, 2 0 ,337. (24) Landis, H. R. M.: The relation of organic dust to pneumokoniosis, J. Indust. Hyg., 1925,7, 1. (25) Sayers, R. R., and M eriwether, F. V.: Miliary calcifications of the lungs due to unknown cause, Reprint 1431 from Pub. Health Repts. 45, December, 1930. (26) F awcitt, R.: Fungoid conditions of the lung, Part I, Brit. J. Radiol., New Series No. 99, March, 1936; Part II, Brit. J. Radiol., New Series No. 102, June, 1936. (27) D ickson, E. C.: Coccidioides infection, Arch. Int. Med., 1937, SO, 1029. < ia li Vi ' & i ; 436 A. J. LANZA AND R. J . VANE far exceed those found for men in other pursuits, as to leave little room for doubt th at silica is implicated. W ith regard to silicate and other inorganic dusts not containing free silica, American m ortality d ata are very meagre. The relatively low death rate from tuberculosis among grinders in the small American insur ance experience suggests th at the effects of aluminum oxide, silicon car bide and other substances used in m anufactured wheels are slight. British data, much more complete, show lower than average tuberculosis mor tality up to age thirty-five, but substantially higher m ortality after age forty-five for a group of men exposed to inorganic dusts other than silica dust. W hether this unfavorable situation later in life is due to the cummulative effect of such dusts with duration of exposure or whether it is due to the inclusion in these occupational groups of a substantial num ber of m en who had been exposed also to silica dust, is n o t clear. There are no m ortality data for men exposed solely to metallic dusts. Recent statistical studies, like the earlier ones, show higher than aver age death rates from tuberculosis among men employed in certain occupations or industries in which organic dust is generated. In no in stance, however, does the rate for a group of this kind approach in mag nitude the extremely high rates found among men employed in some of the occupations in which there is exposure to silica of clinical knowedge, is.it possible to account for the excessjffiffigPy on the score of damage to the lung tissue caused by dust. t - The relationship between dust inhalation- and 'hcute pulinon^P fS S ase remains a field for further investigation. A splendid contribution to our knowledge of this subject has already been made by the U nited States Public H ealth Service in their bulletins on The Health of Workers in ifusty Trades (32, 33). A greater volume of d a ta of this kind and more detailed studies of occupational m ortality are vitally needed to guide the work of industrial physicians and hygienists in this field. REFERENCES (1) H offman, F. L.: The mortality from consumption in the dusty trades, Bull. 79, U. S. Bur. Lab., November, 1908. (2) H offman, F . L .: The mortality from respiratory diseases in the dusty trades, Bull. 231, U. S. Bur. Lab. Stat., 1918. (3) HoFFMAfT, F. L., Chairman: Preliminary report of Committee on Mortality from Tuberculosis in Dusty Trades, Working Conditions Service, U. S. Dept. Lab., 1919. Second preliminary report of Committee on Mortality from Tuberculosis in Dusty Trades, Natl. Tuberc. Assn., 1919. INDUSTRIAL DUSTS 435 an unusually high m ortality from pneum onia (28) and the same is true of certain occupations in the steel industry (29, 30). Exposure to dust is associated w ith some of these occupations and usually extremes of tem perature are also encountered with such other conditions as would tend to cause dampness and chilling. So far as silica is concerned, a high m ortality from pneumonia is associated with the silica trades, both in this country and abroad. W hether silica acts as a predisposing cause of pneumonia or due to the accompanying lung damage the prognosis is more unfavorable, cannot be shown from the figures available. For some years, a series of interesting studies has been carried on in Pittsburgh by H aythom and Meller and their associates in an endeavor to establish any possible connection between the prevailing high mor tality rate from pneumonia in th a t city and atmospheric pollution. These reports are interesting and suggestive b u t not entirely conclusive. The following quotation is from a recently published report of these authors (31). I t is further seen . . . that during the years from 1932 to 1935 when the de pression was a t its height, when air pollution from industrial flues was greatly decreased and when economic and living conditions were a t their worst, there was a great decrease in the number of deaths from pneumonia. However, the decrease occurred in females as well as males so that the change cannot be attributed to conditions within the plants, such as overheating and rapid chilling of the employees. SUMMARY Early occupational m ortality studies focussed attention on the im portance of dust as a cause'of respiratory diseases. Virtually all kinds of dusts were implicated. Present day clinical and laboratory studies point to the serious damage, to the lung tissue caused by a few dusts, notably silica and asbestos, and to the relatively little damage to the lung tissue caused by many other dusts. The m ost complete recent m ortality studies have been examined in the light of this clinical and laboratory knowledge. These m ortality data, while yielding highly suggestive information, are very incomplete and perm it only quali fied general conclusions regarding the effects of du st exposure on the incidence, of respiratory diseases for even the broad classes of dust with one exception--silica dust. The death rates from tuberculosis among men in occupations in which there is exposure to free silica so 434 A. J. LANZA AND R. J. VANE In the American insurance experience, covering the years 19151926 (6), also, the ratio of actual to expected deaths was above average for several occupational groups exposed to organic dust. The ratios of actual to expected deaths for the more im portant of these were: cotton mill operatives, 176 per cent; woolen mill operatives, 134 per cent; upholsterers, 225 per cent; cigar m akers and tobacco factory operatives, 174 per cent. The occupations discussed here have been traditionally classified among the dusty trades. One m ay well question, however, the inclusion in such a list of boot and shoe and of tobacco factory workers. The great bulk of workers in these industries cannot be said to be exposed to appreciable quantities of dust. B ut taking the list as it stands, there is obviously no resemblance between the tuberculosis ratios for these oc cupations and the very high ratios for occupations with exposure to silica dust. Some condition connected with the work of persons in these trades obviously is associated with the above-average incidence of tuber culosis. I t m ay be th a t the less robust workers are attracted to them. W hatever m ay be the explanation, clinical findings would suggesT dust is not an im portant factor in the high incidence of tuberculosis ii these trades. FUNGUS DISEASES OF THE LUNGS D ust may convey to the respiratory tract various types of fungi. Some of these apparently have no clinical significance. Others are pathogenic and may produce either acute or chronic disease. The constantly increasing use of the roentgen-ray in diagnosis and in routine physical examinations has served to awaken interest in fungoid diseases about which too little is known and which are not uncommonly diagnosed as tuberculosis (25). Our knowledge of the subject is very incomplete but it is recognized th at these fungus diseases are frequently occupational in origin and associated with dust inhalation and may result fatally. M ortality statistics are entirely lacking, b u t the reports of F aw citt (26) and the recent studies of coccidioidal infection in California (27) indicate th at such pulmonary diseases may be quite important. PNEUMONIA The effect of dust inhalation upon the incidence of and m ortality from pneumonia has been the subject of much study w ithout any clear-cut picture of the rle of dust resulting (32, 33). The foundry industry has nwF INDUSTRIAL DUSTS 433 of textile plants and he stated th at there was no evidence of organic dust causing pulm onary diseases (24). The m ortality picture as regards organic dust and tuberculosis is confused. In the Registrar-General's R eport (5), out of thirteen classes of textile workers, six had above average death rates from tuberculosis but in only one class--wool, worsted, card, comb or frame (not spinning frame) tenters--was-the rate as m uch as 59 per cent above average. No TABLE 4 Standardized mortality (comparative mortality figures) from respiratory tuberculosis of males ages 20 to 65 years in occupations exposed to organic dust compared with that of all occupied and retired civilian males taken as 1,000, England and Wales, 1921-1923* 1IOXTALITY RATIO All occupied and retired civilian males ^............ ............................ .. Wool sorters........................................................ ...................................... .......... Cotton blow room operatives--skilled......... ................................................. Rag grinders, wool willowers, etc..................................................................... Cotton card and frame (not spinning frame) tenters...... ............................ Wool, worsted card, comb, or frame (not spinning frame) tenters........... Cotton strippers and grinders and card room jobbers................................. Cotton spinners and piecers............................................................................. Wool and worsted spinnera and piece...................................................... Cotton--double, windera, warpers, beamers, etc....................................... Wool and wonted--double, windera, warpers, beamers, etc.................... Cotton w eave.................................................................................................... Woolen and worsted w eave............................................... .: ........................ Weavers of other textiles.............................................................. .................... Boot and shoe clickere and c u tte .................................................................. Skilled boot and shoe operatives, not clickers or c u tte ............................ Bakers and pastry cooks................ ................................................................... Tobacco factory operatives............................................................................... Upholsterers, coach trimmers, and bedding m ake................ .................... Drafters and brush m ake................................................................................ * Compiled from Registrar-General's Decennial Supplement, England and Wales, 1921, Fart II. Occupational Mortality. other class showed more than 16 per cent excess, while in several classes the rate was quite low. On the other hand, boot and shoe factory workers showed an 82 per cent excess; tobacco factory operatives had 100 per cent excess m ortality, and brush m akers and drafters, 138 per cent excess. T h e rate for upholsterers, coach trimm ers, bedding m akers was 26 per cent above the average. Table 4 gives the Standardized M ortality for the principal occupations exposed to organic dust. 432 A. J. LANZA AND R. J. VANE dust was injected into the peritoneal cavity of animals, the reaction was inert. In the process of welding, m etals and metallic oxides are volatilized and inhaled into the lungs in a very finely divided state. Reports have been made of roentgen-ray films, taken during the physical examination of welders, which showed an appearance of nodulation resembling fine silicosis. This has given rise to the question as to whether silicosis m ight be contracted from welding (21, 22), although all these cases were symp tom free. One of the cases reported by Sander came to autopsy following an accidental death. No fibrous tissue was found and it was concluded th at the nodular shadows on the film were causecL.by collections of iron and carbon pigment in the lymph channels of the lung (21, 23). No satisfactory statistics are available on the m ortality of men ex posed solely to m etallic dust. Perhaps there is as much dust of this character throw n off in grinding as in any other process and the comments regarding the. m ortality of grinders and of buffers and polishers, given $ under inorganic dust, are pertinent here. These mixed m etal an^ dusts from the composition wheels do not seem to have produced mo! tality rates from tuberculosis comparable in any way w ith those where,, the sihca hazard is severe. .......... . ORGANIC DUSTS Until the action of various kinds of dusts upon the lungs was made the subject of experimental studies, the organic dusts, rising from industrial processes, were considered to be responsible for tuberculosis. Knowledge resulting from the extensive studies of silicosis has tended to minimize the possible action of organic dust, both on account of the large average size of the particles and their small numbers when compared with the concentration of inorganic dust particles found in various industries. The presence of pulmonary fibrosis or other structural change caused by organic dust and associated with infection has not been demonstrated among industrial workers. Nor is there evident, in connection with in dustrial processes involving exposure to organic dust, a clinical picture which could be compared w ith th a t associated with silica. The late Doctor Landis of Philadelphia was one of a group of physi cians who were among the first in this country to study tuberculosis i among industrial workers. His studies included employees of a num ber * INDUSTRIAL DUSTS 431 m ight have been expected and 18 deaths from influenza and pneumonia where 11 were expected. In the 1925-1936 study (7) there were 10 deaths from tuberculosis among limestone and marble cutters where one was expected. Here again, as in the case of the British limestone masons, cutters and dressers, the question is raised as to whether some of these men had not worked on granite and other stones as well. G ranite and sandstone cutters in the American insurance experience, as we have shown, had more than twenty-six times as many deaths from tuberculosis as expected. American iron miners apparently have a different type of exposure from the British. W e have included them in table 1, somewhat ar bitrarily, w ith the occupations exposed to silica dust. There were 12 deaths from tuberculosis among them where only 1.4 were expected, or a ratio of 857 per cent. This very high ratio suggests th a t, in some Arner-. ican mines, there may be a greater silica hazard than had been thought. The num ber of deaths was small, however, and the result cannot be considered conclusive. METALLIC DUSTS Hoffman (2), in Bulletin 231, emphasized the danger of exposure to metallic dusts (pages 51-161), b u t the experience of recent years has not borne out his conclusions. There has not. been defined in the various industries in which exposure to metallic dust occurs any definite or specific pulm onary disease resulting therefrom. All the indications are that, where pulmonary disease has been described in conjunction with metallic dust, the blam e m ust be placed.on coincidental exposure to silica dust. M acklin and M iddleton (17), reporting in 1923, point out th a t silicosis is associated w ith the use of natural grindstones and not artificial grindstones and make no mention of ill effects from m etal dust. Collis (18) had stated the same general conclusion in his well known M ilroy Lecture in 1915 and stated further th a t the percentage of free silica is the index of harmfulness. D rinker (19) states th a t there are no d ata to indicate th a t iron in the absence of silica caused pathology in any way comparable to silicosis. Carleton (20) states th a t hem atite is relatively harm less compared w ith flint and other silica dusts; if inhaled over long periods of time, it might cause fibrosis and tuberculosis b u t further evidence is needed. Under experimental conditions, it is a relatively harmless dust. In a series of experiments by M iller and Sayers (15), when iron oxide 430 A. J. LANZA AND R. J. VANE deaths. T he extraordinarily high ratio of 1,150 per cent was recorded for tin and copper miners, while sandstone masons, cutters and dressers had a ratio of 441 per cent. On the other hand, only the limestone masons, cutters, and dressers in the nonsilica group exhibited' a high ratio, 191 per cent. W hy these m en should have so high a ratio is not clear. I t m ay be th at m any of them had carried on their trade, a t one time or another, in districts where granite or sandstone were cut and, consequently, had been exposed to silica dust. So far as the occupations exposed to silica dust are concerned, as we have mentioned, these findings are in agreement with American insurance experience. Unfortunately, there are only a few occupations exposed to inorganic dust, other than those discussed under silica and coal dust, included in the American insurance experience and none of these is entirely free from complicating exposure to silica. In the 1915-1926 Medico-Actuarial Study (6), a small group of grinders of metals had twice the expected number of deaths from tuberculosis, while in a some w hat larger exposure in the period 1925-1936 (7), the number of deaths from tuberculosis was about one and a half times the number expected. In recent years, sandstone grinding wheels have largely beem-re . by composition wheels throughout industry. I t is a fair assum ption^ therefore, th at m ost of the grinders were exposed to dust from composi tion wheels, silicon carbide, aluminum oxide, etc., althougb-undtmbtF some grinders were employed where sandstone wheels are still in user This comparatively favorable-result is a t variance with the result for grinders in-England and W ales (5) who had a ratio of actual to expected deaths of 368 per cent. T h a t study covered the years 1921 to 1923, and the proportion of workers using sandstone wheels may have been greater than in the later American insurance experience. The report of the Registrar-General brings out the im portant fact th at grinders in the cutlery industry, where the sandstone wheel is much in use, have a much higher m ortality than do other grinders. We have determined from the facts presented in this report th at among the cutlery grinders there were over seven and a half times as many deaths from respiratory tuberculosis as expected, whereas among other grinders actual deaths were somewhat fewer than three times the expected. Buffers and polishers of metal, a somewhat similar group, were repre sented in the 1915-1926 American insurance study (6) by 17,000 life years of exposure. There were 10 deaths from tuberculosis where 7 INDUSTRIAL DUSTS 429 rapidly increases as age advances. In the Non-silica Group, the comparative mortality is actually below normal up to age 35; it rises just above normal in the following age-group; but a t ages over 45, it is conspicuously above normal. The report does not give the facts regarding the m ortality from re spiratory tuberculosis separately for each of the eleven occupations in cluded in either the silica or the nonsilica group. Because of our special TABLE 3 Ratio of actual to expected deaths from respiratory tuberculosis among males ages 20 to 65 years, exposed to specified kinds of dusts, England and Wales, 1921-1923* ACTUAL DEATHS EXPECTED DEATHS 2A T I0 PEE CENT Silica Dust All selected occupations........................................................... 654 Tin and copper mine--underground workers, not super- intending staff........................................................................... 92 Potters' mill workers; slip makers; potters.............................. 105 Earthenware, china, etc., kiln and oven men, and kiln set- ters and placers.................... ; ................................................... 50 Metal grinders.............................................................................. 221 Sandstone miners and quartiere.......... ..................................... 36 Sandstone masons, cutters, and dressers.................................. 150 1 7 9 ..... 8 37 23. 60 17 34 365 1,150 284 217 368 212 441 Nonsilica Dust- All selected occupations............................................................... 162 150.3. 108 Brick and plain, tile makers, moulders, etc., furnace and crucible pot makers,................................................................ 34 33.7 101 Brick, tile, etc., kiln and oven men........................................... 15 22 68 Iron ore mine--underground workers, not superintending staff (Staffordshire and North Riding of Yorkshire).......... 13 24 54 Limestone miners and quartiere............................................... 39 38.6 101 Limestone masons, cutters; and dressers.................................. 61 32 191 * Compiled from: Registrar-General's Decennial Supplement, England and Woles, 1921, Part II. Occupational Mortality. interest in the facts for this particular disease, we have calculated, from the original report of the Registrar-General (5), for each of the selected occupations, the number of deaths from respiratory tuberculosis which m ight have been expected on the basis of death rates prevailing among all occupied and retired civilian males between the ages of tw enty and sixty-five. These results, together with the numbers of deaths which actually occurred, are presented in table 3. Each of the silica occupations had over twice the average num ber of 1<!' I 1 428 A. J. LANZA AND R . J . VANE INORGANIC DUSTS OTHER THAN SILICA, ASBESTOS AND COAL DUST M any industrial dusts contain silicain combined form, as distinguished from free silica, such as combinations with magnesium, iron and alum inum. The effect of silicate dusts upon the lungs, with one exception (asbestos), is problematical. Where exposure to silicate dusts occurs in industrial establishments, under circumstances which m ight be thought hazardous, one does not see the clinical picture which is presented where free silica is involved nor is there evidence of disability and tendency to infection. Extensive animal experimentation with silicates, both by inhalation and intraperitoneal injection (15), fails to produce any disease akin to silicosis o r other evidence of definite disease. I t is doubtful whether there is a definite disease to which the term silicatosis can be applied, although such a term has been devised. Certainly, the last word has not been said with respect to silicate dusts. Similarly the dusts of aluminum oxide and some other artificial abra sives, of.hem atite, and of other inorganic dusts have not been shown to be the cause of marked pulmonary damage. M ortality statisi emphasize the distinction between the effects of dusts containir and other inorganic dusts. This is very strikingly brough study, based on the occupational m ortality d ata of the_Regit of England and W ales (5), by Collis and Yule (16). Th< selected for study two groups of occupations--one exposed to silica dust and the other to nonsilica--so chosen th a t each had as far. as possible the same am ount of dust exposure, physical effort, exposure to heat or to weather, or any underground environment. P art of the authors' com m ent on the results as regards respiratory tuberculosis is quoted: For all ages (20 to 65) the C.M.F.5 of the Silica Group is no less than 592.2 against 163.5 for the Standard Population, i.e., the mortality is more than three and a half times the normal. For the Non-silica Group, the C.M.F., although actually slightly higher than normal, a t first sight hardly seems to differ significantly from the normal; nor would one's judgment be much af fected, if instead of making comparison with the Standard Population, one had used the Social Groups I I I and IV, for which the respective C.M.F.'s are 159.8 and 164.2. But the summary figures conceal interesting changes with age. A glance a t the figures shows th at in the Silica Group, the ratio of mor tality to the normal, though greater than unity even in the lowest age-group, 'Comparative Mortality Figure: This figure is defined as the number of deaths that would have occurred in the Standard Population at the rates ruling in the occupation. S { INDUSTRIAL DUSTS '427 employees; a t ages 45 to 54, in 10 per cent; and a t ages 55 to 64, in 20 per cent. No such rise with age occurred in any general population group for which com parable data are available. The prevalence of tuberculosis was greatest among the rock workers. The next to the highest rate occurred among anthracite workers who had changed more than five years previously from very dusty to relatively non-dusty oc cupations in the industry. The third highest rate was exhibited among per sons who had had appreciable exposure to harmful dusts in other industries. Among the regular miners working a t the face, the rate was definitely higher than in the control group (men whose dust exposure averaged less than 5 million particles per cubic foot) which showed a prevalence rate of less than 1 per cent. When the term of service exceeded 20 years, more than 2 or 3 of which in volved exposure to heavy concentrations of rock dust, about 37 per cent of such employees [classified as rock workers] showed evidence of pulmonary tuberculosis. Service of 25 to 34 years was associated with a. tuberculosis rate of 8 per cent among non-rock workers employed in the haulageways, of 14 per cent among the regular miners, but with a rate under 2 per cent among men exposed to less than 5 million dust particles per cubic foot of air. Asbestos: Exposure to asbestos dust m ay produce a pulmonary fibrosis which, like silicosis, m ay cause disability and death b u t which does not appear to carry with it a predisposition to tubercle infection and which has a pathology quite distinct from silicosis. The circumstances under which asbestosis will occur are not too clearly defined and undoubtedly^ there has been a tendency to classify as asbestosis cases in which the causal relationship of asbestos to the condition present has been assumed rather than proved. Our knowledge of asbestosis is based on individual reported cases. The actual num ber of fatal cases of asbestosis, supported by postm ortem examination, is too few to have any statistical weight b u t the disease itself and its pathology have been clearly dem onstrated. G ardner (13) believes th at the action of asbestos dust, unlike silica, m ay be mechanical and not chemical. If this is so, it would well explain some of the con fusing aspects of this disease. The cases described have originated in textile and other asbestos fabricating plants and not in connection with the mining of asbestos. Pedley (14) found th a t the tuberculosis mor tality rate in Thetford M ines (whence 80 per cent of the asbestos used in the United States is derived) did not differ materially from the rate of the Province of Quebec as a whole. 426 A. J. LANZA AND R. J. VANE ard lives. Compared with the death rate for laboring groups generally, therefore, the tuberculosis rate for bituminous miners is quite low, whereas the rate for anthracite miners is as high, if not actually higher, than the average for this class of workers. The num ber of deaths and the ratio of actual to expected deaths for coal miners is given in table 2. The following quotation from the Public H ealth Service report (9), previously referred to, is of interest in showing the incidence of clinical tuberculosis among anthracite miners: Several surveys have shown that tuberculosis of the lungs occurs among 1 to 2^ per cent of the general adult white male population of the country. In a TABLE 2 .............................. Number of deaths and ratio of actual to expected deathsfrom tuberculosis of the respiratory system Ordinary Department Mortality Experience of American Life Insurance Companies* Coal Miners 1915-192 1925-1936 OCCUPATION Actual death Ratio . per cent actual to expected i! II Ratio -e|tggcgnt- expccBBjg Operatives not underground............. ...................... 14 Operatives underground ^ .VS,. Total..................................... .................................. 125 Pennsylvania (mostly anthracite).................. t Other localities (bituminous)........................... t 159 157 . -- --- . t -" 'T " 35 115 334 20 lfrl * Compiled from: Joint Occupation Study, Actuarial Society of America and The Asso ciation of Life Insurance Medical Directors, 1929; and Occupation Study, Actuarial Society of America and The Association of Life Insurance Medical Directors, 1938. f Data not available. study of tuberculosis in Framingham, Massachusetts (10), it was found that about 1 per cent were suffering from the disease in an active form, and another 1 per cent were classified as having arrested tuberculosis. Physical examina tion of 100,924 adult white males made by the Life Extension Institute (11) indicated a prevalence rate of about 1J per cent when suspected cases were included. A somewhat higher percentage, namely 2 per cent, was found by the Public Health Service (12) from the examination of 10,000 male industrial workers. Among the anthracite workers examined, the clinical tuberculosis rate was below normal in the younger adult ages, but a t ages 35 to 44 clinical pul monary tuberculosis was diagnosed in about 5 percent of the hard coal mining INDUSTRIAL DUSTS 425 high among certain groups of miners while among others the death rate from tuberculosis has been consistently low. Recent investigations have cleared up m any points about the hazard of coal dust and have indicated certain differences between anthracite coal and bitum inous coal. I t is desirable, therefore, in studying the effects of coal dust to consider these two types of exposure separately. In 1934, the Public H ealth Service (9) m ade a report on an investiga tion of pulmonary disease among anthracite miners. This report stated w hat had previously been suspected, namely, th at anthracite mining had, under certain conditions, a silica hazard and m any anthracite miners were exposed to the effects of coal and silica dust. The evidence tends to show th a t disabling miners' asthm a is, in effect, silicosis, a silicosis modified by coal dust b u t nevertheless a silicosis. Turning to the m ortality record of coal miners, we find th a t the M edico-Actuarial Occupation Study (7) shows for the Pennsylvania miners (nearly all anthracite) the following figures, based on 144,535 life years, for the twelve-year period 1925-1936: There were 1,699 actual deaths where 613 were expected, giving a ratio of actual to expected deaths of 277 per cent. Of this excess, 37 per cent was due to accidents; and 63 per cent to disease. T he pneumonia and influenza death rate was five tim es the norm al; tuberculosis, over three times the normal; and accidents, five times the normal. Miners elsewhere (bituminous) presented the following figures: There were 52,522 life years and 330 actual deaths against 187 expected, a m ortality ratio o f,176 per cent, b u t of this excess m ortality, 84 per cent was due to accidents hnd 16 per cent to disease. T he death rate from accidents was five times the normal; the pneumonia death rate was norm al; and the tuberculosis death rate, 61 per cent in excess of normal. I n the insurance occupation study (6, 7), as we have pointed out, the death rates for each occupation are compared with the rate for standard ordinary policy holders, a rigorous standard as compared with the rate for all occupied males. W hen considering the m ortality of m en employed in mining operations many of which are carried on by unskilled workers, it is especially necessary to bear this fact in mind. A part from any specific occupational influence conducive to a high incidence of tubercu losis, we should expect a greater than average m ortality from tubercculosis among them because of their economic status. Insured common laborers outside of the mining industry, it should be mentioned, have a death rate from tuberculosis about three times as great as th a t of Stand- 424 A. J. LANZA AND R. J. VANE miners, b u t in the earlier study (6), covering the years 1915-1926, there were 11 deaths from tuberculosis in this group or eighteen tim es as m any as expected. T he ratio for iron miners, 857 per cent, is unexpectedly high inasmuch as it is thought th a t m ost of these workers are exposed to only moderate amounts of silica dust, except for a limited number who are working in hard rock. I t might have been expected th at their mor tality would more closely approximate th a t of coal miners. The num ber of deaths is small,, however, and the difference m ay be more apparent than real. Among cutters of granite and sandstone, there were 38 deaths from tuberculosis in an exposure of 5,944 life years, compared w ith 1.4 ex pected, or more than twenty-six times as many as the expected number of deaths. Chippers of. m etal (exclusive of ship chippers) had 16 deaths from tuberculosis where only one was expected. - I t will be observed th a t the ratio of actual to expected deaths from tuberculosis for each of the silica occupations is higher in the period 1925-1936 than in the period 1915-1926. The reason for this apparently lies in the difference in the trend of the death rates for men in these oc cupations and the rate for insured persons generally. While the figures are too small on which to base broad conclusions, they s u g p s ^ i ^ ^ ^ ^ in silica occupations have n o t shared in the general decline in the iSb JBs rate from tuberculosis. . I t may be th at there was actually . a i t j ^ n in the rates for the period 1925-1936over th at forthgperibd"19l^jW ffli Interesting confirmation of these high ratios by English d ata is pre sented in table 3. English tin and copper miners had a death rate from tuberculosis eleven and one-half times the average; sandstone masons, cutters and dressers, nearly four and one-half times the average; and m etal grinders, about three and two-thirds times the average. Ratios such as these cannot be explained away on the ground of differing social classes or the selection of the occupation by physically weaker types of workers. This evidence is in agreement w ith reports of silicosis studies from South Africa, Australia, Canada, and Great B ritain as well as the United States and is supported by clinical experience of physicians in many parts of the world whose practice has been among workers exposed to silica dust. Coal dust: I t has long been known th a t coal miners are subject to chronic pulmonary disease characterized by dyspnoea and usually termed "m iners' asthm a," also th a t the death rate from respiratory diseases is INDUSTRIAL DUSTS 423 No useful purpose would be served by quoting extensively from the impressive volume of m ortality d a ta available to show the influence of silica dust on the incidence of tuberculosis. Virtually every one of the m any studies is in agreement in showing extraordinarily high m ortality rates from tuberculosis for industries and occupations in which large numbers of men are known to be exposed to a real silica hazard. These rates are so high, in fact, as to leave no room for doubt of the causeand-effect relationship between the hazard and the high m ortality. A few figures from the insurance investigations (6, 7) m ay be quoted. Table 1 shows the ratio of actual to expected deaths for the chief occupa tions exposed to silica dust. TABLE 1 Number of eallis and ratio of actual to expected deathsfrom tuberculosis of the respiratory system Ordinary Department Mortality Experience of American Life Insurance Companies* Occupations exposed to silica dust 1915-1926 1925-1936 O C C U PA T IO N Aduli deaths Ratio percent actual to expected Actual deaths Ratio per cent actual to expected Stonecutters--granite and sandstone.................... 16 Chippers of metal--(not shipbuilding)................ 8 Mine operatives--underground Copper mine operatives....................................... 24 Gold and silver mine operatives........................ 9 Iron mine operatives..................................... .. 4 Lead and zinc mine o p e r a t i v e s . ----- 11 Other and not specified mine operatives........... t 976 38 2,639 615 16 1,667 913 804 260 1,833 -- a * * '..' 11 12 3 10 1,381-- 940 857 -- 1,020 * Compiled from: Joint Occupation Study, Actuarial Society of America and The Asso ciation of Life Insurance Medical Directors, 1929; and Occupation Study, Actuarial Society of America and The Association of Life Insurance Medical Directors, 1938. t Data not available. Among a group of underground miners employed in mines other than coal mines, nearly all of whom were employed in m etal mines, there were 65 deaths from tuberculosis in the years 1925-1936 in an exposure of 25,000 life years where 6 were expected, or about eleven times as m any deaths as the expected num ber. There were 13 deaths from pneumonia where 5 were expected. Tuberculosis deaths were fourteen times the expected among copper rpiners, nine times the expected among gold and silver miners, and eight and a half times the expected among iron miners. In this experience, there was only a small representation of lead and zinc .421 A. J. LANZA AND R. J. VANE These are the Registrar-General's Decennial Supplem ent for England and W ales (5) and two studies m ade jointly by the A ctuarial Society of America and the Association of Life Insurance Medical D irectors (6, 7). In the English study, the tuberculosis death rate for men in a given occupation, ages 20 to 65 years, is compared with th a t for all occupied and retired civilian males of the same ages. . The method of analysis employed in the insurance studies was to compare the actual num ber of deaths which occurred among men engaged in a specific occupation with the expected number of deaths calculated on the basis of death rates by ages prevailing among standard lives, th a t is, persons who buy insurance on an annual basis in amounts of $1000 or more and who are not em ployed in hazardous occupations. Thus the insurance standard is a more rigorous one than th a t of "occupied males in the general popula tion" since those in the lowest social-economic class are excluded, as are men who are employed in occupations where there is a Serious exposure to dust, accident or other hazards. This should be kept in mind in interpreting the figures presented for insured lives in the following discussions. INORGANIC DUSTS Silica: Silica in the form of dust produces a definite^ disease of the lungs, namely silicosis, a progressive fibr< itself, m ay cause disability and death and which carriesj disposition to tuberculous infection, v Silicosis results from i of dust containing free or uncombined silica. Its pathology has been extensively studied, both clinically and in the experimental laboratory. I t has been established th at silica particles which penetrate the lungs are under ten micra in their largest diameter and are mostly from one to three micra. N ot only m ust the silica dust be in a state of such fine subdivision, but the particles m ust be present in large amounts and the exposure of the individual m ust be prolonged. When such conditions are fulfilled the natural defenses of the body against inhaled dust break down and silicosis results. T he precise nature of the action of silica dust upon body tissues is not definitely known b ut it appears to be a protoplasmic poison and pro duces its effect chemically and not mechanically. A given dust is dan gerous in proportion to the am ount of free silica which it contains. The nature of the relationship between silicosis and tubercle infection has not been determined, but the fact of such relationship is attested by overwhelming evidence both clinical and statistical (8). INDUSTRIAL DUSTS 421 There are reasons, obvious to us to-day, why these m ortality studies have not been an entirely accurate guide. For one thing, students of m ortality did not have the benefit of the clinical and laboratory knowl edge regarding dusts now available and, consequently, had to make their own classifications of dusts on a somewhat arbitrary basis. They were handicapped, too, by the fact th at the existing occupational codes often brought together all the men in a whole industry. This did not perm it of detailed studies of the m ortality of men exposed to a single type of dust. Occupational m ortality statistics still lose much, of their value because of this same lack of refinement in methods of classifying occupa tions. Then again, factors other than dust, which have a m arked in fluence upon the incidence of tuberculosis among men engaged in differ ent occupations, were not as well understood and were not given due consideration in interpreting the results of m ortality studies. There are pitfalls in reasoning from cause to effect, especially where tuberculosis is concerned, and the error of post hoc ergo propter hoc is particularly to be guarded against. A high incidence of tuberculosis or other respiratory disease among men in a given occupation does not necessarily indicate the existence in th at occupation of a definite oc cupational hazard. I t is well established th at people of the poorer economic classes, whether in industry or out of it, have a higher incidence ' of respiratory tuberculosis than do people better off financially. In Miss W hitney's (4) study of Death Rales by Occupation in Ten States in 1930, the standardized death rate for tuberculosis was over .twice as high among, unskilled workers as among all occupied males while in the Registrar-General of England and W ales' study (5), 1921-1923, the rate for unskilled workers was about two-fifths higher than the rate for all occupied and retired civilian males. Certain occupations, too, are more suited to the physically weak and are selected by them as a means of earning a livelihood. When the followers of an occupation are recruited from the ranks of either of these classes, it is to be expected th a t a high r incidence of tuberculosis m ortality will be found among them. Failure to take cognizance of these factors as possible explanations of a high tuberculosis incidence in certain callings has led to much m isinterpreta tion of the significance of m ortality findings. I t is not our purpose to reassess the older statistical m aterial to which reference has been made. We shall limit our discussion of statistics mainly to the results of the three m ost recent investigations in which tuberculosis death rates are obtainable for a number of occupations. 420 A. J. LANZA AND R. J. VANE In 1908, D r. Frederick Hoffman (1) wrote an article on the m ortality from consumption in. the dusty trades. T en years later, he produced the well known Bulletin 231, The Mortality from Respiratory Diseases in the Dusty Trades (2), an im portant milestone in the hygiene of industry. In 1919, appeared the first and second prelim inary reports of the Com m ittee on M ortality from Tuberculosis in the D usty Trades (3), of which Committee, Doctor Hoffman was Chairman. An indefatigable worker in m any fields of public health, D octor Hoffman's name is thus linked to the early authoritative publications in this country dealing with dust and pulmonary disease. The various reports of Governmental Com missions in South Africa, Australia, Great Britain and other countries have also stim ulated industrial studies and laboratory research into the effects of m any kinds of industrial dusts, especially those containing silica. A t the present time, while no one would state th at we have adequate information about the effects of the inhalation of industrial dusts, we do know a great deal more than we did tw enty years ago. Both clinical and laboratory studies have given us some knowledge of w hat kinds of dusts are dangerous, the circumstances under which they are dangerous, and the nature of their action upon the pulmonary tissue. We have-als learned a great deal about the prevention and control of the dust hazard by engineering m ethods. B u t when we seek evidence of the effects of dust inhalation in m ortality and morbidity, records, w e.findrtha& tk,statistical demonstration of m ortality and m orbidity due to the inhala tion of dusts is anything b u t satisfactory or complete. This situation is the more regrettable because comprehensive m ortality and m orbidity statistics would be of the greatest value in clearing up m any doubtful points regarding the effects of specific dusts and would bring to light occupations in which there m ight be a real, but unsuspected, exposure to injurious dusts. Early occupational m ortality studies, it m ust be adm itted, gave the first broad clues to the extent of the dust hazard in industry and to the kinds of dust which are m ost injurious. These earlier m ortality studies, valuable as they were, however, were in many instances misleading. Virtually all kinds of dusts were shown to be productive of tuberculosis rates higher than average, whereas recent clinical and laboratory experience points to the very considerable damage to the lung tissue produced by a few dusts, notably silica and asbestos, and to the relatively little evidence of harm done to the lung tissue by organic and many inorganic dusts. INDUSTRIAL DU STS AND T H E M ORTALITY FR O M PULM ONARY DISEASE1 A. J. LANZA and R. J. VANE* Air and w ater are the two immediate vital necessities of our lives. We take extraordinary precautions to guarantee for ourselves not only an ample supply of water but one of defined purity, and vast engineering water-supply projects, costing m any millions of dollars, are an accepted and commonplace fact in our times. W ith respect to the air we breathe, we are more complaisant. D ust arising from industrial processes pollutes the atmosphere of working places, in mine, factory and mill, and the products of combustion, both industrial and nonindustrial, are liberated into the atmosphere of our communities with little restraint. In recent years, particularly, in dustrial dusts have received much attention and much effort has been p u t forth by industrial firms of all kinds to control dusty processes in their establishments. Fortunately, nature has furnished us with a respiratory system which has not only a large margin of safety, b u t a fairly efficient protective, mechanism. When th at protective mechanism is subjected to severe stress for a sufficiently long period of time, it may fail. The extent to which such failure may be reflected in m ortality experience is, within certain limitations, the subject of this discussion. We are concerned here with industrial dusts other than those commonly recognized as poisonous. Lead, mercury, arsenic, manganese and other systemic poisons are excluded,, together with the chemical poisons. Those dusts with which we are concerned are both organic and inorganic, and the latter, in turn, may be subdivided into metallic and nonmetallic. There are m any possible subdivisions of these three classifications but for our purpose extensive subdivision, is unnecessary. Indeed, it is difficult to ge t sufficiently ample statistical m aterial to give us definite information under the general headings. 1 Read as part of the Symposium on Tuberculosis in Industry at the joint session of the Pathological, Clinical, Social \york and Administrative Sections at the 34th annual meeting of the National Tuberculosis Association, Los Angeles, California, June 23,1938. * Me ropolitan Life Insurance Company, New York City.