Document RpR63Vwd7dLna9GKb2847d54n

FILE NAME: Talc (TALC) DATE: 1970 DOC#: TALC409 DOCUMENT DESCRIPTION: Unpublished Internal Report-Talc, Fibrous - Tremolite ; fa L V7 ' V ; TALC.. P12R0U3 WU2M0MTB . (5 fibora/ml > 5 |A in length) The fibrous variety of talc, M ell a. that of it. ...oclatad . auphlboi.., tremollt. and anthophylllte, contain flbar. which ar. cla.si- fled a. aabaatoa. fibrous talc haa beau shown to bo of graatar physio- losical significance than the variety lo a nuad.er.of auvlron- mentaland clinical atudica related to ,,cvhora cnpoaod to.talc du.ta. a proper evaluation of the mineral dust haaard requires a differentiation in the threshold limit value, for the fibrous and non-fibroue forma, Porro, Patton and Hobba (1)# on the basis of 15 caaaa with 5 post mortem enamlnatlona, reported that a.be.totlc bodies are almoat invariably present in the fibrotlc areas in cases of talcoaia and noted a degree of similarity between asbeetosis and pneumoconiosis due to talc. Siegal and associete. (2) found an advanced fibrosis Incidence rate of ft.? P cent i,, , study covering 221 tremolite;talc miner, and millers. The dust to which these ,,orl|rs were exposed was largely fibrous and this physical c h .r a c te fi.tib was considered to be responsible for the pathology of .the lung le.it, particularly bepeuse of its ra.ombl.no. tq'asb.atoaia. Plnd- ing. by McLaughlin and ccwcikar. (3) indio.tad that'falo pneumoconiosis could k. caused only by the fibrous verieties of talc. Asb.sto. was oonsideraa . be ,,or. activelyiflbroganlo, posaibly duo to the higher propertlon Of fiber, in asbestos.I In postmortem ex.mln.tion. on 6 tele industry worhers, Soheper, end Purhsh (b) bund bl.tologlo.lf.atu. which suggested CRMC-HT-TALC-000109 f* ( tMO - 8 '.' t l ,, t .m o llt . v . th . m in p.thog.nlo t ' p r y i n g th. 0 h M .o t.rt.tU told lung lesio n . Them ..o n tn U .p .d t tht eh. ftbrou, .p h lio t ^ 8hc . . . . . . tsoio of oh. . . b . . t U t y p .. In studying Che a ffe c ts o f , M l c dust on nnlmsl' tissue, thd .nut uthor. (5) found thet the dogreo to , vhich the fibrosis supervene, depends on the length of the fibers rether r then on their cheslleel composition. Kleinfeld et *1. (6) reported, postmortem 7 .findings on 6 tele industry others in uhich the bodies found in respirntory t( `bronchioles or bedded in fibrous tissue vere indistinguisheble from asbestos bodies a seen in asbestosis. . . r< Because of the striking similarity in the fibrotic reaction produced by talc and asbestos fibers, the suggested threshold limit of 5 fibers, exceeding 5 microns in length, per milliliter of air, is recommended for talc, . ' _ References; ' . _ X. Porro, F.W., Patton, J.R.. Kobbs, A . A . : > . J* Roentgenol, . 507 (19^)- 2 . S ie g a l, W., SMth/AoRop Greenburg, L , : Am. J . Roentgenol. k & 11 ( ^ 3 ) * 5 . McLaughlin, A .I .G ., R ^ r r , . * , Dunham, K .C *: Z A t . J .^ n d . Med. 6, 18k : c w ) - ; t .. . r}:: . ; k. Schepera, Durka|, T.M.: Arch. Ind. Hlth. J2, 102 (1955) g, ibid,$ Arch, Ind, Hlth.J 12, 517 . : . . . xleinfeld, M ,, Giel, C.P., Majeranovakt, S.F.. Massite, J.: Arch, toviron. Hlcht % 101 (1963)- I crmc-ht-talc-000110