Document pmx8VLN75Y0nyz9yy7dnO1bdE

FILE NAME: RT Vanderbilt (RTV) DATE: 1970 DOC#: RTV138 DOCUMENT DESCRIPTION: Unpublished Report-Talc, FibrousTremolite ; im , ; ALC,.TOW - W S M im - * (5 fib ere/m l > J ji in length) The fibrous v a riety o f ta lc , as w e ll as that o f I ts associated . amphibolas, trem ollte and anthophyllita. contain fib er s which are c ia a s ifled as asb estos. Fibrous ta lc has been shown to be o f greater physio lo g ic a l sig n ific a n c e than the non-fibrous v a r iety in a number o f environ mental and c lin ic a l atudiee related to wc"kers exposed to ta le d u sts. A proper evaluation of the mineral dust hazard requires a d ifferen tia tio n in the threshold lim it values for the fibrous and non-fibrous forms, * Perro, Patton and Hobbs (1 ), on the b a sis o f 15 cases with 5 p o st mortem examinations, reported that aabeatotic bodies are almost invariably present in the fib r o tic areas in cases o f t le o s le and noted a degree o f s im ila r ity between asb estoais and pneumoconiosis due to ta lc . S leg a l and a sso c ia te s (2) found an advanced fib r o s is incidence rate .'of 1^,5" per cent in a study covering 221 trem ollte ta lc miners and m ille r s . The dust to which these workers Vera exposed was la rg ely fibrous and th is ph ysical ch aracteristic wis considered to be tesporisible for the pathology of^the lung le s ic s , particular!' because of i t s resemblance to aab a sto sis, Find ings by McLaughlin and coworkers (3 ) indicated that'jtale pneumoconiosis could ha caused only by the fibrous v a r ie tie s o f ta lc . Asbestos was con sidered .. fee more a c tiv e ly fibroganic, p o ssib ly due to the higher propor tio n Of fib ers in a sb esto s,;; In postmortem examinations on 8 ta lc industry workers, Schepara and Darken (ft) found h is to lo g ic a l features which suggested CRMC-HT-TALC-000109 W O *2 - . .. that trem olit* was the main pachogonio agent i r provoking fcha ch a r a cter istic Calc lung le s io n . There was reason to suspect that tha fibrous ampbibolea ' might cauas a taaction o f tha aabaatoeie type. In studying the e ffe c ts o f , ta lc duet on animal' tissu e , the same authors (5) found that the degree to which the fib r o s is supervenes depend on the length of the fib er s rather than on th eir chemical composition, K lein feld e t a l , (6 ) reported postmortem ? ^ f in d in g s on 6 ta lc industry workers in which the bodies found In respiratory ' r `bronchioles or imbedded in fibrous tis s u e ware in d istin g u ish a b le from asbestos bodies a seen in a sb e sto s is , Because o f the str ik in g s im ila r ity in the fib r o tic reaction produced by ta lc and asbestos fib er s, the suggested threshold lim it o f 5 fib ers, exceeding 5 microns in length, per m i l l i l i t e r o f a ir , i s recommended for talc. Reference1 1. Porr, p,W,, Patton, J ,R ,, Hobbs, A .A .:,A n. J, 'Roentgenol, 507 (19*12), 2 . S leg a i, W., Smith, `AR, Greenburg, L, : Am. J, Roentgenol. h<J, 11 (1943). 3 . McLaughlin, A .I,G ., Rogers;. E ., Dunham, K.C: E r it. J , Ind, Med, 6, 18k I W ) . ' vi . ' h, Schepers, G,W.H., Durkajn, T.M. : Arch, Ind, Hlth, 12, 102 (1955)* . .. -i ' i-. 5. : ib id . J Arch, Ind, H lth .jlg , 317 (1335). 6* K leinfeld, M*, G iel, C.P., Majeranowakl, S .F ., M esslte, J ,: Arch, Environ, Hlth, % 101 (1963). I TM *C -H T -TALC-000,,,