Document 5Lzer6NadN23w8aRvn30rNz0V

EXHstik i LQjIL. 2 1S29 the Ifetropolitar Ufa Insurance Coopaay was approached by firas representing the asbestos industry in the United States with the recueet that a hygienic study be aada of that industry. The officials representing these fims were lesiraus of ascertaining if aabaatsa dust was aa occupational hacari ia their establishments aad, if so, what waa the nature of this haaarr tzs.z iz.z'Lz. Z3 ic^3 zz :r -cc-rcl .z. % About this tisa several artisias had appeared ia English aedioal Journals describing a pneumoconiosis due to aabaatsa dust. Tails ia sae or tto isolated iaataacea the occurrence of this 177a of pneumoconiosis had beer, described'ia Aaarisar. Journals, the iaduatr7 itself appeared to be quite um- iaforaed sf the existence of any auch occupational disease. The hazard of silica dust with special reference to ths lur.gs has long been appreciated aad a great deal of study aad raaearth has been applied to the silisa dust problec, primarily ia the aetal naming industry, i- Great 3ritiaa, the Halted States, tha British Dominions, aa wail as ia other 'countries. The nature of ths effects of silica dust expressed ia the tera 'silicosis*, with the resultant extraordinary predisposition to pulmonary tuberculoaia, ia well knows. These effects ha-re been associated with the inhalation of dust contain ing free silica la varying aaouata. The effects upon the pulmonary tissue of dusts containing conbined silisa - silicates - are still a fertile field for investigation, but evidence is accumulating that certain of these dusts produce pathological results quite distinct from true silicosis. 3 ^e r.ane asbeatosis has- beer, applied to the pneunoeoniosis caused, by asbestos dust and it will be ao used in this raport. Chenically, the aabastcs of conneroa ia a hydrated sagnsai.ua silicata consisting prlaarily of. Silica 44.ii Uaraeaia 42. Tater La.Sjf wails fsrraua iron and nickel ars present ia anal! quantities. This csnnsrcial jvariety of aa'cestcs scat csencniy sncountersd ia designated aa carpsotils end iz :.-.a if :hs four Tanet:.9s tics ziusmi. aartaatias, _a wnicu -t usually occurs ia. 3eaas. It should be borne ia nind that silicosis (aad presumably aabeatcaia) develops very slowly, talcing fron fir# to fifteen aad even twenty or twenty- fire years to beccne established. This rate ofprogress ia influenced sairly by the dosage of silica which the lungs receire and this dosage, in turn, de pends upon three variables: the account of silica in the dual, the quantity of duat in the air, aad the extent of erpoaurs. Individual idiosyncrasy night be included aa a fourth variable; however, little ia known of the varia tions ia susceptibility ia those exposed to duat. liars does not appear to be present, in places where asbestos is ninsd or fabricated in iTorth Anarica, the clear-cut clinical, picture which is so (in escapable in coenunitiss with a true allicasi3 hazard, such aa hard rack ninirg ccnnur.itiaa. It night be thought that eoce of the aabeetos plants are of tso recent origin far the typical effects of a silicate dust to becoca nanifest, but this theory would not apply to the older nines or to all of the fabnctiinp plants. tie Industrial Health Service of the lietrouolitar. life Insurance Conpaa7 undertook the following lr.~e3tiatioa during the period froa October, 1323 to ;icuir7, 1321. Tils iuTsstiga Lor. included: A. A atud7 of dust ccadi* on.3 la asbestos ainea, aiLls, and fabricating plants. 3- Physical axaniaatisns of asbestos workers, including X-.-17 filas. C. A stud7 of dust eidaust S7steas designed to elininata ascsstcs 5 DOST STTSITH Apparatus and yetiods of Sampling: 3oth tie impinger (1) and tie electric precipitator (2) wars used for tie collection of air samples, far dU3t3, at the breathing levels and in close proximity is Che worJcnen. 3oth of these Toms of apparatus are adapted far tils tori, aa they ara transportable. easily set up and adjusted far tie taking of tie air samples at tie proper level, and are extremely effiaient. Tie impinger toilects tie oust by aspirating tie air ini tier, m- -<-- i. --a--e> - onto a flat surface covered by a liquid in a container. Tie liqui: used, was h* at tiled water, containing 50 perc.ent alaoiol to prevent tie solution of sene of tie dusts, particularly any silica which digit be present. Tie impinger was actuated by an electrically driven rotary purp and tie rate of air sampled was =ea3ured by nears of a resistance type of flow neter with an inclined sancoeter for measuring tie pressure difference. Saci sample repre- sents'tie dust collected from a volume of 100 cubic feet of air. lie electric precipitator is designed upon tie Cottrell precipitator principle used far recovering dusts and fumes commercially. This principle depends on electrifying tie dust particles by naJcing tiem pass cirougi an electrostatic field and tius causing tiem to settle out upon a sheet of cellu loid. Tie electrostatic field is set up by means of a transformer operating from tie lighting lines on 120 volts, alternating current. Air is drawn through tie apparatus by means of a small rotary fan, run by a motor, the quantity being (1) Comparative Testa of Instruments for Tatemining Atmospheric Tusts" Public Health Bulletin Ho. 14-i, Treasury Teparcmenc, Tasiington, 3.C. (2) "Teteminaticn of Suspensaids by Aitematir.g-Curr er.t Precipitators*, SU * ` . Driver ir.i ?.oterz U. Tic^soz:, Joxirzs.1 of Industrial Hygiene, 7ol. VIZ, rr * < - , 192f . 3 I a filv l 10 - 11 - end also in the weaving departne.it where the re_ative humidity wa3 76 par cent, with, a dry bulb temperature of 69'5\ , as cocpared Tith a relative humidity of 4-t per oant. In tho weaving room of plant A. Aside from plant 3, which was unnecessarily dust7, it would appear that the dust hanard was not excessive except in the preparation rtcns of plants 3 and C. The dust counts are interesting too, when considered in the light of the permissible standard for siliceous dust, established by the United States Public Health Service,* namely 10 nillion particles '10 nicrtns and under' ter % cubic fcot. However, we are not Justified in assuring that because aa'cestosis is a aildsr disease, clinically, than silicosis, the threshold of perriasible dust oounta is higher. Asbestoais is pathologically different from silicosis, and the experience so far does not warrant an attempt to define an arbitrary standard of dustiness. _ - UPS? CCSP?.CL Tarious aeaaures, such as oiling, huaidlficaticn, and local exhausts, tended to reduce the dust. Heverthelsss, it was evident that they were only partially successful. It also is apparent that, if it la expected to control dustiness in these plants, final reliance rust rest upon properly constructed exhaust equipment. In plant C in one departaent an experimental installation was set up. In spite of some obvious faults, this equipment, on the basis of coaparative dust counts, reduced the dust by 50 per cent, and with further alterations will probably be 75 per cent, effective. 7or all practical purposes, this is quits satisfactory. It is neither practicable nor economically desirable to install such equipment as will mahe the air entirely dust free, even if this "Health of Torhsrs in lusty Trades (Granite Industry*, Public Health Bullstln So. 137, 3.3. Public Health Service, TTashington, 1.1., 1325. 12 13 - i zi t 1 i i I N is . :i i fj : i I: r: rr fit i I | i 3i .13 i: xi :i m C- 11 3 it 11 II it * M j, * J: ; t : : i ? a 1I! i tie i s ill i 3E :<<4 : I t!* i? ' t It 1 rcz a ^ ^aa i H- 1 2 i iI a ! li1 I i 1s 3 i ii Utmhj: true 3iliccsi3. Several of these classed as negative stated that they Ter; "short-winded".and were so recorded, but too such enphasis should not be placed on these statements of subjective symptoms. Table III shows the occurrence of dyspnoea and cough.* TAB I Positive Doubtful Negative Dyspnoea Cough Dot examined Total 40 15 3 39 20 10 320 67 39 20 The Incidence of tuberc ulos is (based upon X-ray fil-s',1 as revealed ile 17 Is both interesting and important. Tab12 17 Positive Doubtful Negative Tuberculosis (healed) Tuberculcels (active) Total Sxaalned 7 ! 67 0 39 2 \ 20 *Ir. Tables III. to XI, Inclusive, the division Into positive, dcubtful, negative refers to the cases so classified In Table II. This case was diagnosed as probably active on the X-ray findings. and 3 13 - 2C - procable thao these aen Tare tuberculous at the tine their eapioyaeut in the asbestos plant conaeaced. Of the eight disability claia oases, one wa3 oneonplioatad tuberculosis and tore were unccaplicatod as'oestosis who were put on disability because of a aistaken diagnosis of tuberculosis. Xr. this saae ccr.au,r.ity we know of one death due to unocaplioated asbestosis in an individual with aany rears eaployaent in the industry.* ccscius:;?T5 1. Prolonged exposure to asbestos dust causes a pulacnary fibrosis of a definite type distinct froa silicosis deacnstrable on X-ray filas. Clinically, it is of a type milder than silicosis. 2. There is associated with asbestosis in a large percentage of cases definite cardiac enlargement. Asbestosis does not involve an unusual tendency to pulaonary tuberculosis. personal ccaaunication. Xetails not yet published. I <4