Document rpEoMmKLOVx0YjDJJZgZ5vrda

*> . t' n Oi ul r3H f H. CORWIN I-JIN5HAW, M. p., V Stanford University School cf Medicine Trofescor of Medicine l. henry garland, m. b., b. Ch. Stanford University School of Medicine ' JVy/cworiTMd\oiozy -A 63-1 ilhtMrnuons on Figures W.S. SAUNDERS COMPANY 1956 Philadelphia and London J>r-r ____ 6 *Ci -Ot/wT WHjt-l* /'U . *1,,^ I PLAINTIFF'S | EXHIBIT 1 5(\- VIA i UAUTii i*iU n US.j Diatomaceous earth (Infusorial earth) consists of the remnants of skeletons of uni cellular organisms deposited in great quantity during geologic times. In its pure form ;; 4 consists of silicon dioxide, bur the commercial material is often admixed with clay, It is used in the manufacture of insulating materials, in sugar refining, pottery glazing, the making of dynamite, metal polishes, paper, paint, dentifrices and for the filtration of many sub stances. It is often altered during commercial preparation by heat in the presence of soda ash. Considerable amounts of dust may be created when the material is in a finely divided form and when tt is transported by blowers. Industry has found it necessary to provide elaborate protcctive.cquipmcnt to insure the safety of workmen. . Diatomaeeous earth is capable of producing diffuse pulmonary fibrosis. The fibrous tissue is not necessarily formed into nodules as in other types of silicosis. Linear strands, at first fine but subsequently coarse and massive, may develop within o year or two if exposure is excessive. Others have worked in the material for many years without any evident pul monary disease. Dyspnea may be severe and some cases of bullous emphysema have de veloped spontaneous pneumothorax, similar to that observed in bauxite disease. Fibrosis associated with diatomaeeous earth inhalation probably has an unfavorable effect upon rubcrculous infection, similar to that noted for miners' silicosis. The record is not entirely clear on this point however. The complication of right heart strain and failure may occur'in very severe cases of diatomite fibrosis. . The rocntgcnographic findings arc-i^riaiiiii^nri Jiavc nor been well classified in relation to the type of material inlulcd, and the duration and-intensity of exposure. Often there is a mere acccnruation of the vascular markings but, in severe cases, massive linear fibrosis with or withouT nodulation is observed. "Conglomeration--of shadows probably indicates asso ciated infection. -- . GRAPHITE FIBROSIS . Graphite is crystallized ca^on bin often contains considerable amounts of other minerals including as much as 10% silicors-dicridc. Different opinions have been expressed as to the ( pathogenicity of graphite, sonic bonding it to be harmless if silica is absent, while others believe that graphite is capable of causing disabling pulmonary fibrosis.10 PNEUMOCONIOS S DUE TO SILICATES Silicates arc among The most abundant components of the earth's surface. They occur in hunGreds of different compounds, crystalline forms and combinations. When inhaled, most silicates are nonpathogcnic'but there are a few notable exceptions. Asbestosis . Asbestos is hydrated c?Jdum-magncsium silicate useful on account of its resistance to heat and its insulating properties. Its great industrial value lies in the fact that it is a silky fibrous mineral--the fibers b:i-g as long as six inches--which can be woven into fireproof fabrics. Asbestos textiles were used by the Egyptians and Romans for such purposes as lamp wicks and as cremation artire. A good quality of asbestos is that known as chrysolite and most of that used in the United States is derived from deposits in Quebec and, more recently, Vermont. 10 H. E. Harding and G. B. Oliver (Brit. J. Indust. Med., 6:91, 19-19), and L_ Dunner and D. J.T. Bagnall (Drit. J. Indust. Med., 7:100, 1 950) offer evidence thai crap hue is pathogenic. L- Par msggiani. % {Brit. J. Indust. Med., 7/42, 1950) emphasized ihe importance of the silica in graphiie. C. P. McCord (lndusi. Med. and Surg., J5/-183, 19-19) concluded that disability from graphiie had not been proved. uA'pi w * JO. OCCUPATIONAL PUwV.OKAUV DlSKASUS ;.ody is a fiber of the mineral surrounded by protein deposits. The ordinary stains used in histology do net demonstrate asbestos bodies well, bur the Prussian blue staining procedure may be helpful. Wnen seen in tissue sections or in sputum, these elongated fibers are recog nised by their beaded appearance and rounded bulbous ends which may resemble an elon gated dumbbell. The clinical manifestations of asbestosis include progressive shortness of breath on exertion, cough, weakness, weight loss and clubbing of the fingers. Emphysema, bronchiec tasis, and occasionally pulmonary tuberculosis, complete the clinical picture. While it is generally believed that asbestosis predisposes to tuberculosis the tendency is not so striking as in the ease of silicosis. It has also, been surmised that asbestosis may predispose to bronchogenic carcinoma--a hypothesis which has not been fully confirmed. ' The earliest radiographic signs of asbestosis arc those of a fine haziness in the lower lung fields due to a so-called reticular nerwork of shadows, creating a '`ground glass" appearance. Subsequently, there is increasing evidence of more extensive and coarser fibrosis with variable degrees of pleural thickening. A feature sometimes noted is a "shaggy" appearance of the cardiac silhouette resulting from the combination of parenchymal and pleural changes in inter stages. ' The*diagnosis-of asbestosis depends upon a radiographic appearance consistent with diffuse pulmonary fibrosis, a history of prolonged exposure (two years or more) to asbestos dusts, and the finding of asbestos bodies in the spurum. In obscure cases.diagnosis by lung biopsy may be advisable. There is no treatment known to be of value. Pat ients with early signs of asbestosis should be <runu*riJ fom such exposure, and it is probable that the disease will not progress sig nificantly after exposure is terminated. Patients with'asbestosis should-ovoid contact-with tuberculosis and should be nramirrrf 3c frequent intervals to detect the earliest sign of Tuberculous infection so that prompt and energetic specific antiruVurculosis treatment may be undertaken. . * Pneumoconiosis due to Mica - * f'-7"' . ' < . The micas arc a group of complex alumimrm-suicntc compounds of several types. A: least some of these are known to be capable of producing pulmonary' fibrosis if inhaled in finely divided form in high concsr.:rs:igrr over s prolonged period. An exposure of several years to ordinary industrial environment* containing these substances is necessary to pro dune disease. " The micas arc.used je^^.^nabufaeiurc of paper produets (especially that type of wall ;p-pcr which hasi-i^-f^ifdiit^jtuffacej, in the production of some paint products, as luori- combination with bits, and-for Insulating materials in electrical devices (condensors, dearies.1 heaters). # . A-sy^y by the United States 'Public Health Service revealed 10 casts of pneumo coniosis in a group of 57 workmen who had been exposed to mica dust which was free from silica.1 > Poiicard found that the inhalation of mica dust can produce pathologic changes in the lungs which he believed to be identical to those produced bv the inhalation of silica dust* ' Toic Pneumoconiosis Talc is a natural finely powdered hydrous magnesium silicate. Commercial talc is of variable composition and is often mixed with other mineral substances. Talc is widely used in industry in the manufacture of paint, rubber, paper, insecticides and ceramics as well as n Pub. Health Hull. Nu. 250, Wa*Uinpoi\, O. C., U. S. Public Health Service, 1940. JCJ. Jndust. Hyg., JG;U>Qt 1934. '