Document V30ydzY5Z3YRXQVp3YKY4QgQ4
FILE NAME: RT Vanderbilt (RTV)
DATE: 1973 Aug 27
DOC#: RTV177
DOCUMENT DESCRIPTION: Memo Re Petrographic Calculation of Chrysotile & Thremolite Fibers in Talcs [...]
Internai Correspond tK^S*
CONFIDENTIAL LIMITED DISTRIBUTION
Johns-Manyille
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4
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To; R* S* Lamar, R&D Canter ' oi August , 21 1973
0
f (m V. E. Wolkodoff, R&D Cancer
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Copie;
Subject;
PETROGRAPHIC CALCU: TION OF CHRYSOTILE AMD TREMOLITE FIBER! IN TALCS BY FOOD GRADE TALC SPECIFICATIONS TO BE PROPOSED BY FDA, AUGUST 20, 1973, AS A GOOD MANUFACTURING PRACTICE
i. The petrographic method is outlined by Schulze and Eiaenberg of t.Ke U.S. FDA, Washington, D.C., dated February 1, 1973. The method was followed with only two exceptions as
follows: a. 500X magnification was used rather than the 400X recommended since 400X cannot be employed for direct visual examination on the Leit* Orthoplan, b. Square cover slips, 18 by 18 mm, were used rather than'circular cover slips with a diameter of 18 mm. '
2. An proposed by FDA, the maximum pertnissabla number of
fibers are:
. .
Tremolate
-
1,000 fibers/mg
Chrysotile
' 100 fibers/mg
3. The method requires precisely 1 mg of material on a slide for examination. For a frame of reference, the total number of particles in 1 mg of J-M Reeves Jet-Milled`talc is 6,720,000.
4. The results are as follows:
Chrysotile Tremolite
Fibers
Fibers
Material
'
Per mg
Per mg
a. J-M Cyclo-Fil, . Standard 70-34
0
47,040
b. J-M Cyclo-Sorb, .Standard 70-33
168
16,464
c. United Sierra Mistron Vapor Talc No. C-104
0
0
d. J-M Reeves Talc, Jet -
504
336
Milled Kazan.Concentrate
RD-73201-1
t P'! '-V'-I.
CRMC-HT-TALC-000103
Page 2
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R. s. Lamar
August 27, 1573
5. Ip the near future you will be receiving a report oh /lihrysotile fibers in 14 commercial talcs as studied by transmission electron microscope, only two talc$, Englehard Emfcal 599 and Charles P f i z e r w e r e fou^a to be free of chrysot'lo and tremolite. The others
1 contain chrysotile in amounts by volume ranging from about one-tent^ of one pexfcent (Yellowstone Talc) up to three-tenths of one perpent (Italian Talc e Grafite Val Chisone). Johnson and. Johnson Baby Powder contains approximately one-tenth of one pejlcent. If TEM is ever introduced as part of the PDA microscopical procedure,
then indeed only a very small percentage of talcs could qualify by the proposed new standards. Please keep in mind that the lowest level of particle size that can be determined with reasonable certainty by optical petrographic method is on the order of 0.5 micron/although theoretically it can be read down to 0,25 micron/whereas by TEM chrysotile fibrils of approximately.250$ in dia meter can be easily detected and characterized.
6. To the layman, the maximum permissible number of fibers may sound generous. It is not. For example an investi gator may settle on 20 fields of view to characterize the microscopical slide (there are at least 40,000 par ticles in 20 fields) and if one chrysotile fiber" is found then by calculation the number of chrysotile fibers per mg is well over 100.
7 x You requested my opinion on the microscopical procedure as outlined by Schulze and Eisenberg. There are many drawbacks and weak frames from viewpoints of mineralogy and petrography. , The work is .essentially a liferaryN (j_i
. search^but many of the references are outdated, e.g.^, nine references-are listed for the alpha index of refraction:for, chrysotile and these range from 1.493 up to 1.559, Technically the paper is correct but weak;
also, naive.
;*/ 8. It may be coincidence, but the first draft by Schulze and
Eisenberg is dated February 1, 1973. At about this time Johnson and Johnson had fJJfpnded a program at the Colorado School of Mines Research Institute to detect very small percentages of asbestos in cosmetic grade talc. We have learned that the program was successful and-that asbestos down to one part per million could easily be detected and it is my understanding, without benefit of TEM.
\j, l/\J
V. Wolkodoff^
rr 3ee Distribution on; Reverse Side
CRMC-HT-TALC- 000104