Document qmgqxRVRV0228kxNed8Mer7yG
FILE NAME: RT Vanderbilt (RTV)
DATE: 1973 Aug 31
DOC#: RTV182 DOCUMENT DESCRIPTION: J-M Memo RE FDA Proposed Talc Regulation; More Number Exercises; Hope for Reeves?
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UK P. A. Martinson, 2 West A c..;: R. S. Lamar, R&D Center
-j; August 31, 1973
FDA PROPOSED TALC REGULATION; MORE NUMBER EXERCIZES; HOPE FOR REEVES? .
The FDA regulation calls for talc purities of 99.99 percent and 99.9 percent in- term's of chrysotile and tremolite, respectively. Their proposed test method, which is com pletely incompatible with these percent purity data, call for maximum counts of,100. for chrysotile,and 1,000 for tremolite in 1 mg of talc. The FDA. test method calls. for an optical method o*f counting at 40OX. The FDA requirement states further than only fibers 5 microns or greater in length and having an aspect ratio of 3/1 or greater will be counted.
At a magnification of 400X the lower limit of resolution with an optical microscope using heterochromatic light is 1 x 2 microns. In other words, no particles below this, size would be seen or counted by this method. Even at 5 rnicrons petrographic identification ,is very difficult. Positive petrographic identification becomes more possible at 10 microns and above. The FDA test requires that a petrographic identification be made.
h most significant point here is that the numbers of particles per unit of weight increases enormously as the size of the particles is reduced.
In his report of August 27, 1973, to R. S. Lamar, V. E. Wolkodoff states that J-M Reeves talc, jet-milled Hazen Concentrate RD^-73201-1 contains 6,720,000 particles per milligram by direct microscopic count. At- 500X with the optical microscope it is most likely that the greatest numbers ,of particles (b.elow 1 x 2 microns) are not seen and not counted.
This same sample was counted .using the Coulter Counter. This is a well recognized procedure now used in most, if not all hospitals and clinical laboratories for bloodcounts (in place of the older direct microscopic count),
CRMC-HT-TALC-000086
Page 7 P, A. Martinson
' August 31/ 1973
Using the Coulter Counter to count Reeves RD-73201-1 down to 1.19 microns we have determined that 1 mg of this sample has 92/000,000 particles.
Even at 1.19 microns lower limit of detectability the Coulter Counter is ignoring the greater numbers of particles actually present.
Another way of calculating the total number of particles of all sites down to the very smallest is to work back math ematically from the surface mean.diameter. This was determined by air permeability to be 0,50 microns for Reeves RD-73201-1. By this method we estimate that l m g of this talc contains 554,000,000-particles. (See memo R.' S. Lamar to S. Spoil August 29, 1973.) This number is probe,blv closer to the truth than the other two values reported above.-
In V. 2. Wolkodoff's memo of August 27,.. 1973, he reports 504 particles of chrysotile and 336 particles of tremolite in Reeves.
It is difficult but very important to put" these da ta in correct perspective.
On the basis of all. three counting methods, these calculate as follows;
Counting Method
Total Particles Percent
Percent
per mg
Tremolite Chrysotile
Optical; FDA Coulter Counter
6,720,000 52,000,000
0.005 0.00037
0.0075 - 0.0005
Surface Mean Diameter (by air permeability)
554,000,000
0.00006
0.00003
Talc purity by the -three methods would be as follows:
Counting Method Optical; FDA Coulter `Counter Surface Mean Diameter
Percent Talc Purity
For Tremolite
For Chrysotile
99.995
99.9525
99.99963
99.9995
99.99994
99.99991
CRMC-HT-TALC-000087
Page 3 P. A. Martinson
August 31, 1973 "'
Even under the most difficult counting procedure (optical; PDA), we are talking about purities of 99.995 percent and y9.9.925 percent for tremolite and chx/sotile in Reeves. This is pretty pure material by any rational standard'.
These numbers put this perspective. Does i j
\2 \
a-- i? ,s -- - i i i
matter sanity
in a more rational, sane yet remain in Washington,
D.C?
R . S . Lamar
rr
cc:
W. L. VanDerbeek ~ 2 West
J. M. Sharratt - 2 West
I. R. Keefe
- 2 .West
F. L. Pundsack - r s d Center
S. Speil w. c. Streib
~ R&D Center - R&D Center
R. P. Carter
- 5 West
G. E. Parker
- 5 West
F. 3 . Solon
- 1 West
CRMC-HT-TALC-000088