Document 85raXQpNMeDjYYKV0DnwXrjba

FILE NAME: Packings and Gaskets (PAG) DATE: 1932 July DOC#: PAG031 DOCUMENT DESCRIPTION: Memo on Silicosis & Asbestosis HOME OFFICE July, 1932 MEMORANDUM ON THE INDUSTRIAL DISEASES OF SILICOSIS AND ASBESTOSIS I'd Cvoivn Copyright Reserved LONDON P R IN T E D A N D P U B L IS H E D BY H IS M A JE S T Y 'S S T A T IO N E R Y O F F IC E To be y , purchased directly from H.M . STA TIO N ERY O F F IC E a t the following addresses A d astral H o u se. K in g sw ay , London, W .C .a; tao, G eorge S treet, E dinburgh York S tre e t, M an ch ester; t, St. Andrew's C rescent, Cardiff . f . i j , Donegall Square West, Belfast . ; - or through any Bookseller ' .. .V * r'^ss . 5 -.-A CONTENTS. 1. in tro d u c tio n 2. The o rig in an d developm ent of silicosis 3. in d u stries an d processes in which silicosis occurs 4. M eans of p re v e n tio n :-- (i) d u s t suppression (ii) exhaust ventilation (iii) other methods ... (iv) in itia l an d periodic medical ex am in atio n s 5. P rovision fo r com pensation 6. Medical a rra n g e m e n ts for ex am inatio n an d certificatio n of cases . 7. N ote on asbestosis ... APPENDICES. I. Bibliography II. L ist of Com pensation Schemes and processes to which they apply III. L ist of P anels of Silicosis and Asbostosis M edical Board ... IV. Fees payable for exam inations ami certificates by Medical Board QCT 2 9 1932 Division or r.oc.i.avvt; f| i ' ! ^ 1.--Introduction. T h e disease of the lungs now known as silicosis was rec '^V in tins country in very early times as a trade disease those who worked on certain kinds of stone. I t occurred ; Nmasons working with sandstone, and was called " stone \phthisis " ; in later times it was found in those employed in ; 'Tmetuls on sandstone wheels, and was called " grinders' r appeared too in potters, who worked with ground dint, ; called " [jotters' asthm a." and amongst miners in lead, gold mines, it was known as " miners' phthisis." All the^ indicate the same disease, silicosis, which luav be accomp; tuberculosis. It has been found to occur in many indust processes, ail of which have one characteristic in common--t of the workers to the inhalation of silica dust. T he incidence of silicosis continues to be serious and witf as is shown by the following figures of cases in which comjr has been paid under the special dehemes made under so of the W orkm en's Compensation Act, 192.>. During the 1; years there have been 30 cases, including 30 deaths, among men employed in gamster mines and silica brick works; D including do deaths, in the getting and manipulation of at quarries or on premises worked in conjunction rherewi e a s e s . including 37 deaths, in the [lottery industry; 31 cases ing 32 deaths, in the metal industries, including metal ; and sandblasting; and 91 cases, including 20 deaths, in coa The object of this Memorandum is to set out briefly u disease is. how and w here it is produced, the means whirl taken to prevent it, the provision made for compensation, arrangem ents for the medical examination and certifies workmen. Within recent years it has been found that asbestos dust a fibrosis of the hmgo (known as asbestosis) winch resent cosis in many ways. A note on this disease is included. 2.--The origin and development of Silicosis. Silicosis is produced by the action of minute particles of ; kind of dust which have been inhaled m the act of breathm: particles make their way into the deepest recesses of tl where some of them remain and produce a slow' in flat process which eventually destroys the lungs. This dust is silica (dioxide of silicon, S i O .j , the main cor of many rocks such as quartz, sandstone, flint and chert, to produce silicosis the dust must be in the form of minute j so small as to be invisible to the eye, except that in a sunlight they may appear as a cloud, like smoke. This produced when any of these rocks are broken, crushed, gr cut with a chisel or drill, or when any ground silica is mai Dress 1574* 4 These minute particles of silica float. in the air and a hen iniialed, pass through the bronchial tubes to the finest branches which end in the expanded balloon-like air sacs which constitute the respiratory tissue of the lungs. Many of the dust particles are caught on the moist lining of the bronchial tubes, and these are readily removed with the mucous secretion by the action of the muscular wall of the tubes and the special mechanism of their lining m em brane; but those particles which find their way to the inner surface of the air sacs which constitute the actual tissue of the lungs cannot be removed in this way. They are attacked by living ceils from the lung tissue, which surround the panicles and convey them either outward to the opening of the bronchial tubes, or. passing through the wails of the air sacs, move along the drainage channels and spaces of the lung. If the quantity of dust is small the cells will lie able to deal with it successfully, but if it be excessive they will be unable to remove it and the dust laden cells will accumulate giving rise to an inflammatory process. Once this process has commenced nothing can stop its progress, and it [uoceeds. more or less slowly, producing a kind of scar tissue (fibrosisi which ulti mately replaces the lung substance, at first in small -pots or nodules which may become joined up to form larger areas. The extent of lung tissue involved will depend on the concentration of silica dust in the atmosphere and the p'-nod of rime over which exposure has taken place. W h e n silica dust- is inhaled, even in injurious amount, it pro duces no immediate effects, because it dues not irritate the nose or throat. Sooner or later, however, the effects begin to lie felt. W hen ilie fibrosis of the lung has advanced to a certain extent shortness of breath appears and increases, it may he to such a degree as to render the worker incapable of continuing at work. Moreover, a person in such a condition is much more liable to serious chest trouble from infections such as common colds, in fluenza, and tuberculosis titan one with healthy lungs, and at any time in the course of its development silicosis may become com plicated by one or other of these infections. It is possible to determine the concentration of panicles of dust in the atmosphere of any workplace by means of instruments of several kinds. Samples of the dust can he collected and the particles counted and measured by microscopic examination. Such examinations of the atmosphere have been made in mmiv in dustrial processes and it has been found that the concentration of dust varies within wide limits of less than 100 particles to more thari 10.000 particles in a cubic centimetre of air. W hen it is remembered that a man during ordinary quiet breathing inhales 500 cubic centimetres of air with each breath and breathes 16 times a m inute, it will be seen that the num ber of particles which can reach the lungs during a working day will be enormous. . It has not yet been possible to determine for all industries the limit within which a concentration of dust may be considered aaf Aia&ijfc JR!' 5 A ttem pts have been made to determine the limit i'or special 1 dustries earned on under uniform conditions, as in the Unit States granite industry, the South Africa gold mining industry, ai .tunnelling iu sandstone in Sydney, Australia. While su standards are of value in estimating the relative elficiency methods of dust suppression within a single industry, it would n be possible to uipply any of these standards as a criterion of t purity in which it would be safe to work under different conditio and in different industries. Research is going on under the direction of a Committee appoint by the Medical Research Council with a view to extending the kno' ledge and understanding of silicosis and other industrial diseas duo to dust inhalation, particularly in regard to the concentratk of dust capable of causing injury, the conditions of exposure to Ju which influence the progress of the disease, the mode of action silica on the lung tissues, and the influence of infections on t course of the disease. 3.--Industries and processes in which silicosis occurs. Silica is widely distributed in nature and occurs as the chief co stituent of many rocks such as quartz, quartzite, gainst.a\ gr stone, sandstone, chert, flint, in the natural quartzose sand and many of tile igneous rocks, including granite. The chief arc where sedimentary silica rocks are found are Yorkshire, Laucasiiu Northumberland and Durham, Derbyshire, Cheshire, and Nor Wales, South Wales, Somerset, and Gloucestershire, and parts Scotland, including Angus, Ayrshire, Dumfriesshire, Fifeshii L a n a rk . Midlothian, Morayshire and Stirling. Granite and ori: igneous rocks are found principally in Cornwall and Devon, pai of Leicestershire and North Wales, the Lake District, and in t West and North of Scotland. Certain natural deposits of silica occur as the remains of anin and vegetable life, the best known of these deposits being periin kieselguhr. All processes which involve the manipulation of any of tht materials in the dry state in such a way that the silica is brok up into minute particles and inhaled, are liable to give rise silicosis. Chief among these are :-- mining or quarrying of quartz, quartzite, ganister, sandstoi gritstone or chert; drilling and blasting in these rocks; breaking, crushing and grinding of such rocks, or of dr quartzose sand or dry deposits or dry residues of silica, and t manipulation of the crushed or ground material in the dry stai m ason's work on sandstone or g r a n i t e ; manufacture of ganister or silica bricks and other refract! materials ; Breaking, crushing or grinding of flint, and processes in i * A pottery industry m j p j v j n y ^ u ^ ^ ^ -------__________ ___ ... _________ _____ _ _ A it fi grinding of metals by means of gnndscones natural o r artificial sandstone; fettling of steel castings ; and sandblasting if done by means of compressed of quartzose sand or crushed silica rock or flint. composed of air with use j . 4.--Means of Prevention. T h e most im portant m eans for prevention include (i) suppression of d u s t : (ii) ventilation; (iii) other methods of preventing the in halation of d u s t ; (iv) medical examinations. (i) Suppression of dust includes all measures which prevent the dust from being produced It is sometimes successfully accomplished by the use of water, but to he effective the supply of water m ust be sufficient to keep all surfaces of the material wet during the whuie process. In some cases, as in grinding of metals, effectual dust suppression is only attained by the complete immersion of the metal being ground. (ii) E x h a u st Ventilation.--One of the most widely applied means of prevention is by localised exhaust ventilation which to be effective should be applied at or as near as possible to the point of origin of the dust and so arranged with reference to the a ir inlets and .genera! ventilation of the room as to prevent the dust from entering be atmosphere of the work place. W here the dust is produced over a large surface, as in crushing machinery, conveyors, or mechanical sieves, it ts usually necessary to enclose the machine as completely as possible and to apply exhaust draught to the inside of he hous ing. sufficient ro maintain a slight negative pressure and pre vent escape of dust from apertures. In the case of silica dust, where the particles are -o minute, considerable care and experience are required in de.-ianiim the dust collecting plant. It is also necessary to prevent ibe du-r from the exhaust plant entering the atmosphere where any persons are working and for this reason systems of iocali-ed exhaust ventilation must be provided with dust collecting appliances. The percussive drills worked bv compressed air. which are largely used at mines and quarries and produce largo quanti ties of fine dust, can now he provided with a " dust trap " which gives the workmen efficient protection. A considerable number of these dust traps are now in use. T he principle in these drills has been adapted to pneumatic tools for stone dressing by n device the working of which is demonstrated at the Home Office Industrial Museum.* I n the H om e Office Industrial Museum th ere are also exhibited a series of photographs of the chief processes in the pottery, metal grinding, and refractories industries, and the protective measures required, as well as specimens of the ' A t lio fseferry R *d, W estminster, S .W .l. .Open on every y eek -d a y ; l<i .m. to 1 p.m. r e a d 2 to 4 p.m. TAdmission - ..... -.... -- ------'ni. *.-> -.r: ^ r ;- ' 7 materials giving rise to silica dust, microf holographs i counts of the dust content of the atmosphere of th places, and X-ray photographs of the lungs of workers by silicosis due to work in these industries. (in) Other preventive measures.-- W earing a L> apparatus consisting of a helmet or closely fitting f provided witli an air supply drawn through a tube iron source ali'ords protection for workmen employed itt | carried on occasionally only or for short periods and gatory for sandblasting' under the Grinding of Jietals laneous Industries; Regulations. Respirators can never he regarded as a substitute haust ventilation hut for processes which are outside t! of mechanical ventilation an efficient respirator is di The only respirators with a filtering medium of fibre o which are at present available. alVord insufficient pr against fine dusts, hut investigations are being made Department of Scientific and Industrial Research i efficiency of various types of respirators. Consideral gross has been made and it is hoped that before" long a tor possessing the necessary properties will he prodaici. The cllecrual separation if dusty processes. <o as to workers employed in iinn-du.-iy processes from ;iiuu exposure to dust, should he adopted wherever practica is required, for example, in racing grindstones nn Grinding of Cutlery and Kdgo Tools Regulations The. success or failure of preventive measures dope only on the satisfactory design and installation of the ventilation system, hut to an even greater extent proper maintenance of the apparatus or plant prnvid this connection there devolves a responsibility on the u as well as on the management, and the various codes of rious which have been issued 'see below) m ake it <*1 on the workmen employed to make full and proper us appliances provided and to report forthwith to the man; any defect in the same. Regulations to safeguard the workman against the in of silica dust are now in force for the grinding of me cleaning of castings,* the manufacture of cutlery a tools,f handling, moving, breaking, crushing, grinding ing of refractory material, and the manufacture bricks." and certain processes in the m anufacture of j For the detailed requirements regarding each indust ence should be made to the particular code of Regulat; * The G rin d in g of M etals (Miscellaneous Industries) Regulat; (S .R . A 0 . 1925, No. 904). t The G rin d in g of C utlery and Edge Tools R eg u lations, 1925 1925, No. 1089). . jig' . j ' 1 T he R efracto ry M aterials Regulations, 1931 (S.R. A O. 1931, N :.g3X>.-..-> r ; pijg p 0tto r y (Silicosis) R egulations, 1932 (S.R. A O. 1932, N o ,3 8 broadly they consist of the elective enclosure of the apparatus with provision of efficient localised exhaust ventilation, and an approved system of mechanical general ventilation, the pro vision of a steam or water spray, the segregation of the dusty processes ; and general measures for securing greater cleanli ness of the premises and appliances. In factories and workshops to which special ^Regulations do not apply the powers given in section 74 of the Factory and Workshop Act to require the provision of localised exhaust ventilation or other mechanical means for removing dust for any process in which dust is generated to an injurious extent can be, and generally are. exercised to prevent exposure to silica dust. Section 78 of the Coal Mines Act. 11)11, requires generally that mechanical drills used for drilling in highly siliceous rocks shall be provided anti used with an efficient means to prevent the escape of dust into the air. Coder the same Act general Regulations' have been made for ganister mines, and under the Metalliferous Mines and loumes Acts, special ruics have been establi.-hed in tin mines and in many quarries where ganister. sandstone and other silica rocks arc worked. (iv) Initial and periodic medical examinations.-- I n certain industries or processes it is now required that workers shall be examined medically before they are engaged, and shall also be medically examined at intervals during their employment, f The object of the initial examination is to prevent workmen whose respiratory physique is defective and who, if not more liable to contract silicosis, mu much greater danger if silicosis develops, from entering the industry. The periodic medical examinations which are carried out at the works should he of great \alue as a preventive measure. They enable cases of sili cosis to be detected at an early stage, and if the workman is then excluded from, or voluntarily gives up. further employ ment in the dusty processes, the development of the disease nmv he arrested. They also enable persons found to he suffer ing from pulmonary tuberculosis, who not only expose them selves to additional risk by remaining in the dusty industries but are also a possible source of infection to their fellow workers, to be eliminated ; and they provide cumulative evi dence as to the changes in the workman's condition which is of the greatest assistance tn diagnosis when the question arises of certification for purposes of compensation. F u rth e r, they indicate where the conditions are still giving rise to the disease, f&i v * B.R. de O. 1920, No. 873. t See the Silicosis and Asbestos is (M edical Arrangements! Scheme, 19:11. : paragraphs 12 and 13. The industries and processes to which these require- V manta apply t n th e Refractories and Sandstone^Industries and certain processes in th e P o ttery In d u s try ,^ . l e J f e t a r t t a i ' * :-AkM s 9 and may thus be of material assistance in enabling the n< sary precautions to be taken. 5.--Provision ior compensation. Com pen sat ion iu cases where death or disablement is cnu.se silicosis or silicosis accompanied by tuberculosis contracted di employment is now payable in all the industries where a sei risk of the disease exists. Owing to the nature of the disea special compensation procedure different from the ordinary visions of the W orkm en's Compensation Acts has had to he dev > Special Compensation Schemes have been made by the Horne l under the powers given by Parliament for the purpose, a li which, and the processes to which they apply, is given in A[ dix II. Before making any claim to compensation or-annlvu the Medical Board for a Certificate (see below) a careful ; should be made of the Compensation Schemes, and parta-nlat tiie processes specified in paragraph 2 of the Schemes. | 6.--Medical Arrangements for examination and certificate cases. ` Any w orkm an desiring to make a Haim to -ompensurinu obtain a certificate from the Medical Board appointed by he 1 Office unless his employer agrees that he is liable to pay i-dc sarion. without- such certificate. This Medical Board, consisting of a Chief Medical Omee: eiulit Medical (Officers, is divided up into four " panels " <> Medical Officers each, with centres at Bristol. Newcastle-on-' Sheffield an d Stoke-on-Trent. The Chief Medical Offic stationed at Sheffield. A list of the panels and the area assigi each is given in Appendix ITI to this Memorandum. The rem uneration and expenses of the Medical Board are pa of a general Medical Expenses i'n n d , which is maintained < fees payable by the employers and workers or their dopcm These fees, and the directions as to when and how they are paid, are set out in Appendix 1Y. The Medical Expenses Fund is administered by five T r t consisting of two employers' and two workers' rep re tives and one official representative. The present addrt f the Secretary of the F u n d is the Home Office, W hitehall, Li S.W .l. I Certificates of disablement.-- A workm an desiring to ol> ' certificate of the Medical Board is advised in his own inter consult, iu th e first instance, liis Approved Society, who will a for him to be examined by the Regional Medical Officer app under the National Health Insurance Acts. This examinatic I * These a rra n g e m e n ts arc based on t-h recom m endations of a D opar Com m ittee ap p o in ted to advise as to th e m edical arrangem ents whit be made for th e diagnosis of silicosis. T he R ep o rt of th e Com m it t k i g . ' i v* published by ELM. S ta tio n e ry Office in 1929. P ric e 3 d. .. 10 be free of cost to the workman. If the Regional Medical Officer is satisfied that there is reasonable cause for suspecting the exist ence of silicosis lie will certify accordingly. On production of this certificate the workman will be entitled to examination by the Medical Board at a reduced fee. He should send the certificate, together with the prescribed fee, either to the chief officer of the Medical Board, or to the senior member of the panel for his area (see Appendix I I I > stating the Compensation Scheme under which the claim is made, the name and address of the works of the employer who last employed him in a process included in the Scheme, the nature and duration of the employment and the date when he left the employment. The Medical Board will then fix a time and place for the examination and will notify the workman accordingly. ' There is no appeal from the Medical Board's decision, and hence it is important that all material information and especially the employment history should be given to the Medical Board. If the workman fails to obtain the certificate from the Regional Medical Officer he may still decide to proceed with bis application for examination by the Medical Board, but in that case he will be reipiired to ilcp<>>it the full cost of the examination, pari of which will, however, be relmuled io him if the Medical Board issue a ci.-ri iticale. Before issuing any certificate the Medical Board send a notice to the employer, or, where a Compensation Fund has been estab lished under the Scheme, to the Fund, and consider any statement made or submitted to them in writing by or on behalf of the em ployer or the Fund within ten days of the date of the notice. Except in cases of death--see below-- the Medical Board are not required to issue a certificate unless the workman is found to Ik: suffering from silicosis or silicosis accompanied by tuberculosis but an intimation of the result of the examination F sent io the work man in every ease. If a workman who is abject to initial or periodic: medical exam ination is. is the result of such examination, excluded from employ ment on account of silicosis or silicosis accompanied by tuberculosis, he is given a certificate (for which no fee is payable!, entitling him to claim compensation in accordance with the provisions of the appropriate Compensation Scheme. Certificates of death.-- In cases of death from silicosis, compensa tion can only be claimed on a certificate given by the Medical Board. Save in exceptional cases where the deceased workman was entitled to weekly payments under a Compensation Scheme during life and the Medical Board are satisfied that a post mortem examina tion is unnecessary, this certificate will only be given after a post mortem examination. It is important, therefore, that when it is desired to claim compensation for the death of a workman, applica tion should be made without delay.to the,Medical Board, who will : VwWWcSgJ t a s o . v 1 II arrange fur the post mortem examination. The apphea be accompanied bv the fee prescribed by the Regulatiui formation as to the nature and duration of the deceased employment. In cases where inquests are held, Ii.M have been invited to consult with the Medical Board arrangements for the post mortem examination, and i Board an opportunity either of making or of being repi the examination. Disposal of certificate.-- If, as in the Refractories and Industries, a Joint Committee, representing both emp workers has been appointed for the settlement of claims, t Board will forward the certificate to the Secretary of Committee, who will communicate with the workman or 1 ants, as the case may be, in regard to the claim. In cases arising in other industries the certificate w to the workman or his dependants who should then claim to compensation direct to the employer. F nder th for these industries compensation is recoverable from tin. who last employed the workman in one or more of th. and the procedure for recovering compensation is su the same as that laid down in tile Act for recovering con for accidents or scheduled disease.-.* 7.--Asbestosis. Asbe.stosis is a disease of the lungs produced as a rm inhalation of a.-bestos dust usually over a period of sex, It is characterised by a special type of fibrosis of the 1 which resembles silicosis in its general features of cum development, but differs from it in some of its clinical t logical manifestations. The disease occurs in workers in occupations associ production of asbestos dust in a fine state of division : fui in the preparatory processes of crushing, disintegrating at of tlie crude asbestos; in blowing, mixing and carding in spinning yarn and weaving cloth and other asbest materials; and in the making of insulatin'.' mattresses or semions composed wholly or partly of asbestos. T h e characteristics of the dust which gives rise to tl differ in some ways from the silica particles which cans In the case of asbestos, owing to the fibrous charaet mineral, the free particles are usually extremely thin fibres. ` The change produced in the lungs is a gradually i fibrosis which spreads throughout the lungs. The no tribution of the fibrosis, so characteristic of silicosis, prominent feature in asbestosis. Tuberculosis may co apparently does not supervene so frequently as in sili 1 * See Home Office Memorandum on the Workmen'# Compeni 1925-1931. ^ H .M . Stationery Office, price Once the fibrous tissue change is established in the lungs, the disease becomes progressive. The first prominent symptom is usually shortness of breath and it remains the most prominent one throughout. Bronchitis, bronchiectasis and broncho-pneumonia are complications frequently met with. Industries and processes in which asbcstosis occurs.--Processes involving exposure to asbestos dust which are known to give rise to asbestosis or in which the conditions are such as to be liable to produce the disease, are the breaking, crushing, disintegrating, opening and grinding of asbestos and the mixing or sieving of asbestos or unv admixture of asbestos, the manufacture of asbestos textiles, the making of insulating slabs or sections and the making or repairing of insulating mattresses composed wholly or partly of asbestos, and the sawing, grinding and turning in the dry state of articles composed wholly or partly of asbestos such as motor car brake and clutch linings, electric conductors and packings and jointings. Means of prevention.-- As in the case of silicosis, suppression or cuiiuol of the dust is the chief m eans of preventing the disease. T h e principal methods <ff client mg this (now obliguloiy under the Asbestos Ludustrv Peculations'! are the substitution of wet methods for dry. effective enclosure of dust-producing machines, substitution of enclosed mechanical methods for hand convey ance and for dusty hand work generally, and application of ex haust draught at dust-producing point*. As in the silica industries, initial and periodic medical examina tions may be of great value as a means of preventing or arresting the development of asbestosis; and they have now been made obligatory + for workmen employed in the processes of breaking, crushing disintegrating, opening or grinding of asbestos, and the mixing or sieving of asbestos or any admixture of asbestos, and in the making of asbestos textiles and insulating mattresses. ['rocision for Compensation.--Compensation is pavuble m cases of death or disablement caused by asbestosis or asbestosis accom p a n i e d by tuberculosis under a special .Scheme. This Scheme applies to workmen employed in the processes, a list of which is eiven in Appendix I I , at any time on or after 1st May. 19-31. The compensation is recoverable from the last employer who employed the workman in the processes and the procedure for recovering compensation is substantially the same as that laid down in the Act for recovering compensation for accidents or scheduled diseases. Medical arrangements for examination and certification of cascs.-- The medical arrangem ents for the examination and certi fication of cases are identical with those described in the earlier pages of this M emorandum foi S ilico sis. _______ __________________ * S.R. * 0 . 1931, No 1140. V tt^Silicoei* and 4*beatoati (M edical Arrangements) 8cheme, 1931, paras. 12 0.1931, No. 841)s 13 A PP E N D IX I. Bibliography. (B Industrial Pneumonoconioses with ; P h th isis." By Dr. E. L. C o m a . H .M . Sta (2) " The A etiology of S ilico sis." By Tubercle, March, 1920. (3) " A Study of Pulm onary S ilicosis." Jo u r n a l ,,f Industri al H y g i en e , M arch, 1921. >i * iu-i\.3 itim V/Iiii in fu rn a ces, w ith special reference to th e etfe the W orkers." By IV. 3 yd* S mith H .M . sta tio n e r y Office 1917. (5) ` R eport on the G rinding of M etals and special reference to the effects of D ust lulu, Hffiee 1923. ^ Und D r` E ` L - Ml,: Id! " Report on the Occurrence o f S ilicosis t R.v Drs. C. G. S utherland an d 3 . Bi Office. 1929. . f, ) " Report ou the incidence of Silicosis rs C. L. S u th er la n d a n d S . B r y s o n . 1920. 4 * I\c|>oi`t on thp Occurrence o f Silicosis I>y Drs. C. L. S utherland S B ry so n S tation ery Office, 1930. 191 " The Bv D r. E. 1929. present position L. M iddleton of S ilico sis in Ii British ^[edical (19! " F irst Report of the Departmental C for Siiicosis dealing w ith the R efractories In 1919." H .M . Stationery Office, 1921. 111) " R eport of the D ep a rtm en ta l Commi Silicosis dealino " ith the Pottery Industry.' 1928. c (12) " R eport of the D ep artm en tal Comir A rrangem ents which could be made for th e Dii S ta tio n ery Office, 1929. (13) R eport on the In tern a tio n a l Confer Johannesburg in August, 1930." By Dr S tation ery Office, 1931. ' Suppression in the Asbestos Industry " Rv and Mr. C. W. P hice. H .M . S ta tio n e r y Offic A