Document qzdKDyqD3nGejaKLB9E2BkVR

DO 0 8 3 9 5 2 CO NFIDENTIAL C A m^RLED SEP 2 2 1993 . niNG k ,,rACKAGE SEE OFFICE PROFESSIONAL!! THE DOW CHEMICAL COMPANY MIDLAND, Michigan March 17, 1972 ,, RL i:,Ti j " ~1572 GAFETY DEPT. V. R. Jackson R&D, Plaquemine Louisiana Division cc: J. A. Granier, Louisiana Division E. J. Brown, Louisiana Division A, M. Paradiso, Louisiana Division H. L. Gordon, M.D., Corp. Me<k., 2&30 Bldg. CPE 2-537 We finally have some results on your talc sample CPE 2-537. Enclosed is a copy of the Microscopy Laboratory report and several photomicrographs at various magnifications. Looking at the photomicrographs at low magnifications (160X and 475X), the sample appears to have an abundance of fibrous particles. However, when the particles are seen at higher magnifications (1900X and 9500X) they no longer show the same structure that characterizes an asbestos fiber (seen at the same magnification). Using stereophotomicrography, the Microscopy Laboratory has concluded that the particles are predominantly of a platelet structure. The fibrous appearing particles are actually some of the platelets standing on edge. Several stereo photomicrographs, along with a viewer, are enclosed to give you an idea of this phenomenon. Commercial talc studies reported in the literature dif ferentiate between the following minerals: Mineral Structure Chemical Formula Talc Tremolite Anthophy11ite Platelet Prismatic Prismatic to fibrous H Mg (SiO.) H,Ca Mg (SiO ) Hj(Mg,Fe) (SiO ) DO 083953 DONFrOENTlAL V, R. Jackson 2 March 17, 1972 Tremolite and anthophyllite are the components generally referred to as fibrous talc, while the platelet structure is the nonfibrous form. Some commercial talcs also con tain the asbestos mineral, serpentine. The reported commercial talc studies have indicated that the asbestos-like problems were caused by tremolite and anthophyllite. The Threshold Limit Values (TLV's) in the Occupational Safety & Health Act reflect these findings: Material . Threshold Limit Value mppcf* fibers/ml of air Asbestos Fibrous talc Nonfibrous talc Nuisance dust 20 30 5 5 X-ray diffraction analysis of your sample showed that the major component was talc with a trace of dolomite (MgO-CaO). Any tremolite, anthophyllite or serpentine content was below the detection level of the method. The quartz content was below the detection level of both the microscopy and X-ray diffraction techniques. From our findings, I can see a problem you might have in evaluating exposures to Mistron Vapor talc. Strict adherence to the standard procedure (as would be expected from an OSHA inspector) for counting asbestos and asbestosform fibers without detailed analysis of the fiber-like particles might indicate a health hazard where one does not exist. The Mistron Vapor talc particles would have to be examined carefully to differentiate between a platelet edge and an actual fiber. Based on the microscopy and X-ray diffraction analyses, our conclusion is that the Mistron Vapor talc sample can be classified as the nonfibrous form. In this case, the TLV of 20 mppcf can be applied (standard light-field counting procedure enclosed) to evaluate the dust exposures. million particles per cubic foot of air DO 083954 CONFIDENTIAL V. R, Jackson 3 March 17/ 1972 I wonder if you can send me some information for our files. Do you know the source of the Mistron Vapor talc and what treatment procedures are used? The material is relatively pure compared to other commercial talcs and appears to be the variety mined in Texas. I hope we have answered your question. If you need more information, give me a call. Best regards 1701 Building 517 636 2880 GHF:s j1/enclosures DO 083955 CONFIDENTIAL 7 z~- 0 'T'iU- Ttf F f// - ^. ftrr <'C4*-Q- C**Zs* * (&7) *h--^ ^-o- - /T 7~t-^7='"->- ^^t<--7 . & 30 (^t~y 7^ * Ct*^*,--- ^^tt~; O. 2 fjf^y^ *iF~fhisC{ -THF 77f V^t-6 7~/7 7* 7**^~~*. DO 083957 CONFIDENTIAL X* . *4MKO A* L<i.r.r (r -. !] /t.~ <L*^< TKS CCW CMSaiCAU CC~?ANY WUIOtAKA BIVIBIGM r.^r.^mn+l /--* /)/) nRporrr or ^`'*-yp,, $^(3_?ci.{1 BaPERCUCt fi^f ./`l^-'iffil. ./x/<-- .a / - /-, ~ 0ww'??/? ..... -- ..... ........... ........ ....... Kfclocifytfccxt&00/l CA. Vtioci'^ '!siStsVARIOUS H&astmej) rrMPUSanji 0 6 a-' (f PK\\ . UvrA Srno ic<. Tbxic Vdociki Ciy^T/vmi/vA/vtr j^XPf\rrx/VDtO (Jterr\} 6 3<fS^ iTV ^.J parrs i SCI-/St) 6.- 'ESi /2 11 170 t/oV JiuJAls^ /vr--*'1' r /S-//V. 1 foil 1rv\r 1 Vu'OcL . t l i ... j ! 76 ^ -- //s > -* <: onJ 0 ft rw - IbCffr^ 8O-/00 70-60c TLV >IO&pp<r) . hv^ *w 6k._____^iA * Ole o-- mv Sr^t^TfJ A'c'Pe*. _ Clojl , 1 DO 08 3959 CONFID ENT TAL