Document KGgoo3a6G4GbE40weZxXVgBJ6

FILE NAME: Johnson & Johnson (JAJ) DATE: 1998 Apr 23 DOC#: JAJ 136 DOCUMENT DESCRIPTION: Letter to Mehaffy & Weber Law Firm from Alice Blount with Attached Articles Alice M. Blount, Ph.D. Mineralogist Q^ April 23, 1998 M. Raymond Hatcher MEHAFFY & WEBER 2615 Calder Avenue P.0. Box 16 Beaumont, Texas 77704 Dear Mr. Hatcher: APR 2 7 E ft MEHAFFY b WEBER BEAUMONT, TEXAS According to your letter of March 31, 1998,1 have written and enclosed a report on the occurrence, regulation and up-to-date scientific view of asbestos, amphiboles and "intermediate" fibers. I have also enclosed copies of my 1990 and 1991 papers, one o f which I am sure that you already have. The 1991 paper was written because I became aware that it was a common opinion among industrial hygienists that industrial talcs were better than pharmaceutical and cosmetic talcs because there was a regulation for the former and not for the latter. I knew that this was not the case and wanted to set the record straight. Although my papers report an improved method for analysis, the determinations for the sample labeled I (Johnson & Johnson's Vermont talc) have been done by the traditional methods as well (see Table 2, page 567 in the 1990 paper). As I told you, I believe that Johnson & Johnson's Vermont talc contains trace amounts of asbestos which arc well below those specified by OSHA. It should be noted that the proposed FDA regulation, which was never finalized, also specified the same 0.1% limit for amphibole asbestos as OSHA. I may be away for short periods during the coming weeks, but I do check for messages on my work phone at the number you have been using. Sincerely yours, Alice M. Blount, Ph.D. Box 3437 Rutland, VT 0 5 7 0 1 Phone: 802-747-4857 e-mail: amblount@together.net Protected Docum ent-Subject to Protective Order J&J-0049150 JNJNL61 000052427 Withheld for Privilege JNJNL61 000052428 PROCESS { i(s MINERALOGY IX: i 1 Applications to Mineral Beneficiation, i (l M etallurgy.Gold, Diamonds, c Ceramics, Environment and Health I Proceedings of International Symposium on Applied Mineralogy (MAC-ICAM- r CAM) held at Montreal, Quebec, Canada on May 14 to 17,1989, and of the Process f Mineralogy Symposium held at Las Vegas, Nevada, February 27 to March 2,1989. * The MAC-ICAM-CAM symposium was held during the annual meeting of the Geological Association of Canada and Mineralogical Association of Canada, and the Process Mineralogy symposium was held during the annual meeting of the Metal lurgical Sodety of the American Institute of Mining and Metallurgical Engineers. Edited by William Petruk l CANMET, Department of Energy Mines and Resources Ottawa, Ontario, Canada Richard D. Hagni Department of Geology and Geophysics I University of Missouri-Rolla Rolla, MO t Susanne Fignolet-Brandom Mineral Resources Research Center University of Minnesota Minneapolis, MN $ Donald M. Hausen 4 Newmont Metallurgical Services Salt Lake City, UT i A Publication of TIRfilS Protected Docum ent-Subject to Protective Order J&J-0049167 JNJNL61 000052429 DETECTION AND QUANTIFICATION OF ASBESTOS AND OTHER TRACE MINERALS IN POWDERED INDUSTRIAL-MINERAL SAMPLES A. M . Blount The Newark M useum, P .0 . Box 540, Newark, NJ 07101 and Department of Geological Sciences. Rutgers University. Newark. NJ 07102 Abstract In 1983. a final ruling of the U .S. Occupational Health and Safety Administration (OSHA) specified that chemicals containing >0.1% of a carcinogenic substance or >1% of a substance hazardous to health must be labelled. Am phi boles of the fibrous o r Bsbestos-type m ust be quantified at levels of 0 . 1% whereas the status of non-fibrous types is not finally determined at this tim e. Trcmoiite and actinolite can possibly be measured to 0.1% by XRD, but snthophyilite cannot be so measured. Recently the International Agency for Cancer Research (IARC) has designated quartz as a suspected carcinogen, and its quantity must be measured to the 0.1% level. T hus, it has become increasingly important to be able to detect and quantify m inerals in bulk samples down to low o r 'tr a c e ' levels. It has been found that m inerals needing to be quantified can often be concentrated by microcentrlfuge and counted by means of polarized-light microscopy. For example, amphiboles in talc samples can be separated by using a heavy liquid (thallium fcrmate-malonate) of density 2.810. Talc floats, and amphiboles sink. After centrifuging, the denser panicles are removed from the bottom with a Pasteur pipette and placed in a clean centrifuge tube. Distilled water is added to the tube containing the denser minerals and the tube centrifuged again. After several washings with distilled water, the sample is removed along with a drop of water to a clean glass slide. A drop of 1.584 refractive index liquid and a cover glass are placed over the dried sample. The slide is scanned for particles greater than 5 tin in length and having ao aspect ratio greater than 1:3. These are checked for refractive index, sign of elongation and extinction angle to differentiate them from talc particles on edge and other minerals. Amphiboles have all indices greater than 1.584. and talc has all indices equal to or lower than this value. Alternately the heavies at the bottom of the centrifuge tube can be filtered through a nucleopore niter. After the filter has been washed with distilled water and dried, a 1.584 refractive index liquid renders the niter transparent in two o f the four extinction positions so that a count of amphibole panicles can be made directly on the Filter. T he refractive index-density method which is so useful for talc powders should be equally useful for other nonsoluble industrial minerals. fVoeew Mineralogy DC Edited by W illiam fttm k . R ichard D. Ragni, Suaanae Pignolet-Brundom. and Donald M. H ausen Tho M ineral, Metal & M aterial Society, 1990 557 Protected Docum ent-Subject to Protective Order J&J-0049168 JNJNL61_000052430 Introduction By the late 60 s and early 70 s the health community became firmly convinced of the danger of asbestos to workers involved in mining and manufacturing, and the United States government agencies moved to regulate this substance in the workplace. T h e airborne fiber limit was first set at 5 fibers/cm3 in 1972. then at 2 fibers/cm3 in 1976. and finally to 0 .2 fibers/cm3 in 1986 (I). In addition, bulk minerals and chemicals were subject to a "H azard Communication" regulation, which specified that b substance must be labeled if it contains > 1 % of a chemical hazardous to health or >0.1% of a carcinogenic substance (2). Asbestos, tremolite. actinolite and anthophyllite are regulated at 0.1% according to the 1986 OSHA regulation. This has proven to be a problem in industrial minerals, such as talc, because this limit is below present detection levels by X-ray diffraction. It may be possible with very tim e-consum ing step-scans to detect tremolite to this level, but this is not possible with anthophyllite. In addition, tremolite. actinolite and anthophyllite occur'in fibrous and non-fibrous forms, and X-ray diffraction does not distinguish between these forms. At the time of this w riting there is a court stay on the part of the Final Rule of 1986 covering non-fibrous tremolite. actinolite and anthophyllite (3). In addition in 1987, the International Agency for Research on Cancer (1ARC) determined silica (quartz, tridymite and cristobalite) to be a suspected human carcinogen (4). This automatically triggered the provisions of the 1983 Hazard Communication, and all industrial minerals containing >0.1% of free silica must be labeled as containing a carcinogenic substance. From this brief outline, the increasing importance of detection and measurement of minerals at trace levels is apparent. The writer considers these to be "trace m inerals' as they are analogous to "trace elements." Under present government regulations, several hundred or less particles are counted in a million particles. A method to do this has been developed and is presented here. It consists of standard techniques of optical and X-ray analysis in com bination with heavy liquid separations. W hereas an individual mineral species has variable density because of chemical substitutions, it is often possible to find a density which will effectively separate minerals of interest. Fig. I shows that talc has a distinctly different density from the amphibole m inerals o f concern. The major pari of our effort hBS been devoted to experimentation with talc containing amphibole. This paper will discuss experimentation with talc and amphibole mixtures although the method is applicable to other powdered industrial minerals. Cum m ingtonite > I Riebecfeite -- > I T rem olite I I AnlKophlyllite * | I ^ A e t t r lo lit e ^ iwwaMOMWMCMacaawMMwvywvvvw 1 2 .7 2.8 2.9 3.0 3.1 3.2 3.3 34 Figure 1 - Chart showing range of density for talc and amphibole minerals (10). 558 Protected Docum ent-Subject to Protective Order I Description of Analytical Methods for Talc-Amphibole Detection of amphiboles in powdered talcs is very difficult. Attempts were made to measure tremolite to 0.1 % by using X -ray step diffraction scans with long counting times on each step. Since very low counts are obtained and since the intensity o f the X-ray diffraction peak is dependent upon slight changes o f chemistry due to substitutions of elements in the mineral structure and to the fibrous or nonfibrous condition o f the m ineral (5). this method was found to be unsatisfactory. F o r anthophyllite. the major peaks have such low X -ray intensities that the method was not attempted. T h e only viable method of analysis has been an optical particle count such as that proposed in 1973 by the Food and Drug Administration (6). Although the original method proposed analyzing an entire I mg sample, most users of the method scan 100 fields of view (f.o.v.). T he procedure Is stated below: "Weigh out 1 milligram of a representative portion of talc on each of two microscope slides. Mix the talc with a needle on one slide with a drop of 1.574 refractive index liquid, and then the other with 1.590 liquid, and place on each a square or rectangular cover glass sufficiently large so (hat the liquid will not ru n out from the edge (ca. 18 mm square) and will provide a uniform particle distribution. Fibers counted by this method should meet the following criteria: (i) Length to width ratio of 3 or greater (ii) length of 5 /m or greater (iii) width of 5 pm or less. Count and record the number of asbestos fibers found in each I milligram as determined from a scan of both slides with a polarizing microscope at a magnification of approximately 400X. In the 1.574 refractive index liquid, chrysotile fibers with indices less than 1.574 in both extinction positions may be present; in the 1.590 refractive index liquid, the other five amphibole types o f asbestos fibers with indices exceeding 1.590 in both extinction positions may be present. Check the extinction and sign of elongation for tentative identification. For specific identification of asbestos fibers, make additional mounts in appropiate refractive index liquids, and refer to the optical crystallographic data in the table. A count of not more than 1000 am phibole types of asbestos and not more than 100 chrysotile asbestos fibers per milligram -slide constitutes the maximum limit for the presence of these asbestos fibers in talc. These limits assure a purity of talc at least 99.9 percent free of amphibole types of asbestos fibers and at least 99.99 percent free of chrysotile asbestos fib ers." A major difficulty with this method is that very many talc flakes are on edge o r at such an great angle that the edge of the flake is seen. These particles then show an aspect ratio greater than 3:1 and must be tested for refractive index by checking the Becke line often in both extinction positions. The procedure is very lim e-consum ing for 100 f.o.v. Using a standard petrographic cover glass there are generally about 10000 f.o.v. per immersion mount (I mg of sample). Thus to be sure that less than 0 . 1% amphibole v'as present the count needed to be 5 particles o r less (5 plus two standard deviations = 9.47) in 100 f.o.v. Several investigators have pointed out the utility of using density along with other optical properties for identification of unknown minerals using the polarizing microscope (7 . 8, 9 , 10) T heir approach is to observe the sink or float characteristics of particles in im m ersion liquids under the microscope. The approach used in this study was to separate the particles of interest using heavy liquids and a microccntrifugc. Selection of Heavy Liquid and Density M any heavy liquids are available to the mineralogist. W hereas there is som e risk associated with such substances ( I I . 12. 13. 14). with proper care they can be handled safely. An advantage of the method used here is that only small quantities of the liquid are used. An im portant consideration in selecting the heavy liquid used in this investigation was the desire to be able to remove the liquid from the particles by washing with distilled water. Clerici solution (thallium formate-malonate) and K lein's solution (cadmium borotungstate) diluted with water were selected. Both proved satisfactory 559 Protected Docum ent-Subject to Protective Order J&J-0049170 JNJNL61_000052432 I > but Clerici solution is less expensive. To determine mineral densities, talc and amphiboles were obtained from all the major talc producing regions of the United States and tested. T h e lowest density at which talc floated was determined by slowly increasing the density of Clerici solution by adding, drop-by-drop, more dense liquid to a less dense liquid which contained talc. At th e point at which the talc floated, the index of refraction of the liquid was determined using an Abbe Refractomeler. The density was determined using a density-refractive index chart (IS) (Fig.2). A sim ilar procedure was followed for amphiboles except that the proper density for the amphiboie to sink was determined. These tests indicated that the best | density for a heavy liquid to separate talc from amphiboie was 2.810. Figure 2 - Density-refractive index graph for Clerici solution at 23* C (15). To avoid having to continuously use the refractometer to adjust the density, commercially produced density standards adjusted to 2.800. 2.810 and 2.820 were purchased. The liquid could then be conveniently adjusted to 2.810. The adjustment is easier if "stock solutions" are made up. one with slightly higher density and one with slightly lower density. Using such solutions eliminates the rapid change of density that occurs with the addition of a single drop of distilled water or very heavy liquid. It is important that the solution is well mixed after each addition of m ore o r less dense liquid. i If not well mixed, density stratification occurs. j iI I 560 Protected Docum ent-Subject to Protective Order J& J-0049171 JNJNL61 000052433 Selection of Centrifuge Once the proper density heavy liquid has been selected, the mineral particles are separated by means of n centrifuge. Several points need to be considered when selecting a centrifuge. These are: (1) In order to separate very small particles in liquids which differ from them only slightly in density, it Is important for the particles to move through a short colum n of liquid or the centrifuge time will be impractically long. A microccntrifuge with 1.5 ml tubes was. therefore, selected. (2) The centrifuge must have a variable speed setting on the spin. T he reason for this requirem ent is that microcentrifuges are designed to handle low-density liquids ( < 1 .2 g/m l). Heavy liquids at high spin speeds exert forces which are great enough to break the centrifuge tubes and tube holders which causes major damage. W hen using a variable speed centrifuge it is important not to run the machine at top speed while using heavy liquids. The maximum safe speed can be determined using the following approximation (16): RPM mBX = rated rpm* V l-2 /D information supplied with centrifuge and dependent upon tube type and capacity D is density of heavy liquid For the present work: RPM = 13.250** Vl 2/2 810 Sample Preparation 8.659 * 1.5 ml polypropylene tube 60 to 100 mg of talc are weighed into a disposable centrifuge tube. About 1.2 ml of heavy liquid adjusted to 2.810 is added, and the sample with liquid is mixed by shaking. T h e tube is then placed in a bell ja r which is evacuated with a vacuum pump for three minutes. T his removes air bubbles adhering to the particles. T he charged tubes are placed in a centrifuge and spun for 8 minutes at a speed of 7000 rpm. The amphiboles should sink leaving the talc floating, so that the particles that have sunk are of interest. The liquid and particles lying at the bottom arc removed with a micropipette and transferred to a syringe. The syringe is attached to a filter holder, and the liquid with heavies is' filtered using a Nuclepore filter (pore size I .Ojtm ) w hich is held in a plastic filter holder. About 40-50 ml of distilled water is washed through the filter to remove the heavy liquid. The filler (plus residue) is then carefully transferred to a clean glass slide with a tweezers and permitted to dry. The amphiboles can be examined without removing them from the filter because the N udeopore filter has an index of refraction of 1.584 in two of the four extinction positions. T his is the proper index of refraction to distinguish between talc and amhiboles. Talc has indices less than or equal to 1.584. whereas amphiboles have indices greater than this value. A drop of 1.584 refractive index liquid renders the Nuclepore filter transparent when scanned in the matching extinction position. The fields are scanned for particles having an aspect ratio > 3:1. These can then be checked for sign of elongation and relative index of refraction in the usual way. The determination of extinction position is slightly different when looking at panicles on an anisotropic filter. 5ince the filter is anisotropic it will change colors on rotation. The extinction positon of a particle is the angle at which it matches the color of the filter. Occasionally a particle will appear dark or the sam e color at all rotations. This simply indicates that the extinction position of the particle and the filter are the same. 561 Protected Docum ent-Subject to Protective Order J&J-0049172 JNJNL61 000052434 Two comments should be made. F irst, it is easier to do an optical count if the carbonate minerals ore removed from the tale by acid treatment before analysis. Calcite will float In 2 .810 liquid but magnesite and dolomite will sink. Second, the heavy liquids that are left in the centrifuge tubes can be reused by filtering them through a filter with 0 .4 /m pores using a syringe and plastic filter holder as used before. Also heavy liquids if left standing for a period of time crystallize and get cloudy. The crystals can be removed in the same way as the heavy m inerals. Analytical Results To determine the level o f amphibole contamination of a sample the efficiency of the spin-down for the amphibole particles and the num ber of talc particles in our sample must be known. Before examining results from actual processed talc samples, these two factors are considered. Efficiency of Spin-down In order to determine the percentage of total amphibole that would be brought down during a single centrifuge run. talc-dolomite samples were analyzed. Dolomite has a density of 2.86 which is comparable to that of the amphlboles (see Fig. I). Mixtures of talc plus dolomite at various percentage concentrations could be spun down, tranferred to a filter as previously described and the filter plus sample weighed. After putting the filter (plus sample) back in the holder and washing with Bcid followed by distilled water, the sample plus filter is reweighed. The weight difference Indicates the am ount of dolomite brought down. Fig. 3 shows the results of these analyses. The bottom line on the graph shows the values obtained when a micropipette removing 0 .(5 ml was used and the top when 0.6 ml was removed. The top line shows more scatter in the data, so most of the results reported in this paper are obtained with a 0.15 ml sample and using an efficiency factor of 14%. T h e efficiency results of 14% and 33% show thal the proposed method could be improved by finding a better method of removing the sample from the centrifuge tube. Several investigators have used liquid nitrogen to freeze the tube contents partly (17) or completely (18). These methods were not tested: however. It was found to be advantageous in some cases to put the heavies from two tubes onto a single filter to get a higher fiber count. oc SAMPLE Figure 3- Graph showing the percentage of dolomite caught on the filter under two different experimental conditions. See text for further explanation. 562 Protected Docum ent-Subject to Protective Order J&J-0049173 JNJNL61 000052435 Number of Amphibolc Panicles in O ne Milligram The 1973 Food and D rug Administration's proposed method is based on the assumption that a one milligram sample of talc contains one million particles. 1000 equals 0.1% 1000/.001 *> 1 x 106 particles A quick calculation using weight and volume shows that one million particles per milligram is probably a conservative estimate. In OSHA's regulations for airborne dusts where limits are in M ppcf (million particles per cubic foot) and in Mg/M-* (milligrams per cubic meter), the two values when equated show that a one milligram sample is considered to contain from 5 million to 200 million particles depending upon the substance. W hile one may think of dusts as having very small particles, respirable dust is. for the most part, greater than 5 jim (19). It is different from processed talc, however, in lacking the large particles > 1 0 n m which represent a disproportions!ly large percentage by weight of processed talcs. Since one million particles per 1 mg sample is considered conservative, percentages of Fibrous particles will calculate on the high side rather than the low side, so this value is used. ppmg = Fibrous particles per mg = .(number of Fibers countcd)/(num ber of f.o.v.) x 5740 f.o.v.* 0.14 x (number of mg of sample) num ber o f Fields of view needed to cover entire filter Percent Fiber then can be determined: % fiber = (ppmg/1 x I06) x 100% T he results in this paper are generally given in ppmg (particles per milligram). C ounts'of total talc particles per milligram can be made on the actual sample. This is done by preparing a standard one milligram sample on a glass slide. O ne drop of distilled water or methanol is added to the powder (not on top but along side), and the liquid and powder mixed with a small spatula. The mixture is smeared evenly over the glass slide and permitted to dry. T he slide Is left uncovered so that the talc particles stand out in high relief relative to air. Counts are usually done o f particles in a part o f the field of view using a grid eyepiece to define the area. Results of counts as just described have shown that processed talcs generally contain 0.9-20 x 106 particles/mg in the optical size range. The only exceptions are some baby/body powders with very large particles. These are often very difficult to count because the flakes are very thin and tend to lie on top of o r overlap other flakes making it necessary to exercise some judgem ent as to whether one is observing separate particles o r a step on the surface of a single panicle. Obviously some particles would be covered completely by others and not seen at all. Values on these talcs are 0.4-0.8 x I0 6 particles/mg. Analytical Results Obtained with M ixtures A num ber of problems w ere encountered in testing the proposed method. Foremost is the question of whether pure starting material would adequately represent the minerals in actual processed talc samples. In addition is the problem of how to mix samples so that the very small percentage o f particles representing the contaminant arc randomly distributed in the sample. Toavoid these problem s, an actual processed talc known to contain amphibolc was chosen and a talc without such m inerals. The percent amphibolc was determined in the former by performing standard I mg -100 f.o.v. counts using traditional methods on eight separate preparations. This yielded a value 2 . 19 0 .9 7 % . M ixtures 563 Protected Docum ent-Subject to Protective Order J& J-0049174 JNJNL61 000052436 were then prepared by first weighing pure talc powder in the centrifuge tube and then adding a small amount of 2.2% talc. T he procedures described in the section "Sample Preparation' then w ere followed. 20 fields of view were counted. The results are indicated in T able I. Except for samples e and h. all are within 2 standard deviations of the actual value. It should be noted that actual unknowns are generally spun-down and analyzed in triplicate, so that any discrepancies can be detected. Discrepancies can be caused by preparation problems such as the gaskets not being tight on the filter holders so lhat part of the sample escapes. Fortunately this is generally obvious before reaching the counting stage. In this test, the samples were not run in triplicate because of the difficulty of mixing a sam ple to put into three centrifuge tubes. If differences had been found during such an experiment it would have been more likely due to mixing problems than to counting procedures. Table 1. Mixtures o f talc contain 2.2% tremolite with pure taic. No. actual measured (a) a 0.06 % 0.04 % (0.01) b 0.06 0.04 ( 0 .0 1 ) c 0.07 0.05 (0 .0 1 ) d 0.15 0.18 (0 .0 4 ) c 0.15 0 .0 7 (0 .0 2 ) f 0.24 0.20 (0.04) g 0.37 h 0.47 i 0.73 0 .3 0 0.34 0 .7 0 (0 .0 5 ) (0 .0 6 ) (0 .1 0 ) j 0.74 k 1.03 0 .9 4 0. 86 (0 .1 6 ) (0 .0 9 ) Actual Commercial Talc Samples A sample o f commercial talc known to contain very small quantities of am phibole was tested with the traditional 1 mg-100 f.o.v. technique and the centrifuge technique. Ten 100 f.o.v. counts on separately prepared mounts were counted. The results indicated 259 ppmg (range for 95% confidence is 0-573 ppmg). T he results obtained using the centrifuge are shown on Table 2. The standard deviation for particle counts can be calculated using P oisson's distribution o = (N)0 -1 (20). The standard deviations listed under the centrifuge method in the Table are calculated in this way. Poisson's distribution is the best that can be achieved if the variation is due to random panicle distribution on the slide and there is no other systematic sources of error. Fig. 4 shows the appearance of a typical amphibole in the talc from which the results shown in Table 2 were obtained. It is made up of fibrils. Note that the photographs in this paper generally show very large panicles. This is due simply to the fact that they are easier to photograph and are selectively chosen for this reason. Another talc known to contain amphibole is shown in Fig. 5. It displays the reason for evaluating tale optically rather than using X-ray diffraction. The volume of the amphibole panicles in this talc is much greater than the volume of amphibole in the talc of Fig. 4. and XRD would yield a much larger value even if it contained the same number of am phibole particles as the previous example. The particles shown in Figures 6-9 are from talcs which, although periodically analyzed by SEM . were not believed to contain amphiboles. Amphibole panicle counts are extremely low and generally there is no indication of panicles being made up of fibrils. The figures show typical panicle shapes for each talc type shown. No amphibole panicles were found in the talc shown in Figures 8 and 9 during a count of 20 random fields o f view; however, panicles were noted during a quick scan 564 Protected Docum ent-Subject to Protective Order Figure 6 - Amphibole particle (length 63 /tin) in talc which measured 88 ppmg ( 2 4 ). Figure 7 - Amphibole particle (40 /vm in length) in talc which measures 25 ppmg ( 2 8 ). I i 565 Protected Docum ent-Subject to Protective Order J&J-0049176 JNJNL61 000052438 I Figure 8 - This talc showed no amphibole particles during a standard 20 f.o.v. scan. This indicates < 2 5 ppmg. Particles could be found by a quick scan or filter. This one is 22 pm in length. Figure 9 Similar to the talc shown in F igure 8. no amphibole particles were detected d u rin g a routine scan. This indicates < 10 ppmg. The particle shown has a length of 66 pm . r j*. -* it Figure 10 - Amphiboie counted on a Nucleopore filter. The count is 102 ppmg ( 1 0 2 ). Length of panicle is 133 pm . Figure 11 - Same talc as Figure 10. The amphibole is counted on a glass slide without a filter as described in the text. T he count is 62 ppmg ( 8 7 ). The panicle length is 34 p m . I 566 Protected Docum ent-Subject to Protective Order J&J-0049177 JNJNL61 000052439 continues. T he density-refractive index chart (Fig. 1) is presented for the convenience of those wishing to apply the method to other mineral associations. Discussion T he method proposed in this paper permits one to find amphibole particles and to view their shape much more easily and rapidly than standard optical methods. It was found that talc contains < 0 .1 % amphibole if less than 20 particles are observed in 20Ttelds of view. On the other hand, using the traditional I mg procedure, less than 5 panicles in 100 fields of view would indicate < 0 .1 % . It is much easier to fmd the amphibole panicles by optical methods after concentrating them with heavy liquids because there is less interference by talc panicles. In the I mg count many talc panicles are seen on edge thereby needing to be tested for refractive index. Although the standard deviations are quite high, the proposed method permits one to routinely analyze industrial mineral samples where it was impractical to do so. It Is not known whether talc that passes the 0.1% Hazard Communication regulation will it pass the airborne asbestos regulation (2 M g/M 3) (21). Unfortunately, one cannot conclude anything about whether or not a talc powder will pass the fiber regulation if it is below the talc dust limit because the mandated analytical procedure is phase contrast which bears little to no relationship to true fiber content where mixed mineral dusts are involved (22). An additional problem as indicated previously Is that the coarser particles of a bulk powder will not become airborne so that a different portion of the sample will be present in the air as compared with the bulk powder. On the other hand, if we consider true fibers greater than 5jim in length it would appear that ihe 2M g/M 3 would offer a good certainity that ihe airborne level'would be less than 0.2 fibers/ctn3. The only way it could be higher would be if only 1/100 of each milligram of talc could become airborne and if all the fibers were in that 11100 of the sample. Since this is very unlikely, it appears that the dust limit for talc is sufficiently stringent for fiber as well. The Hazard Communication regulation generally assumes that percent is either by weight or volume. If percent by weight is used, samples containing stubby particles such as that shown in Fig. 5 would seem to be more dangerous then those samples containing an equal num ber of long narrow particles sim ilar in shape to ihose in Fig. 4 because the weight percent would be higher. For this reason percent by count was chosen. One can. however, determ ine weight o r volume percent by measuring amphibole particle dimensions during a count. This would no doubt be necessary in samples where grinding hBd to be done before analysis. In the course of this investigation, samples of talc have been found to contain amphibole which were not previously known to contain this mineral. In many cases periodic SEM analyses had been done. T he problem with SEM is that little is accomplished in going to sub-optical sizes unless there is also an increase in the ratio of amphibole to talc particles, and there is no indication that this occurs in bulk samples except possibly in the case o f "true asbestos" where the particles have broken into fibrils (23. 24, 25). It is possible that the centrifuge techique will be useful for concentrating and separating amphibole from talc for SEM work. This will require the use o f less viscous heavy liquids so that reasonable centrifuge times can be used for these very small particles. It should not be construed from comments in this paper that all talcs contain amphibole panicles. There certainly are amphibole-free talcs. There are others in which the amphiboles have not been previously recorded because of their low level. All U .S. cosmetic, pharmaceutial or high grade talcs that were analyzed during this study are in compliance with federal regulations, generally by a large margin. 568 Protected Docum ent-Subject to Protective Order J&J-0049178 JNJNL61 000052440 o f the slide. These shown in the photographs were found in this way. T he lower limit indicated assumes that the smallest num ber which could be found in 20 f.o.v. Is 1. O n samples with such low counts one might scan more fields of view, but no purpose was served by doing this in the present case. Table 2. Comparison of values obtained by traditional 1 mg-100 f.o.v. count with centrifuge method using various sample weights. (a) Standard I mg-100 f.o.v. counts Sample fibers/mg a b c d c f g h 1 j average 216 392 234 351 113 376 94 309 0 505 259 157 (b) Centrifuge method (20 f.o.v.) Sample Sample size fibers/m g cr PI 47 mg 253 146 P2 115 277 98 P3 59 296 64 PPI 308 275 108 PP2 60 341 108 60 291 305 98 60 283 100 Application to O ther Problems The results and photographs presented to this point were obtained with particles collected on a Nuclepore filter (1.0 (Jtn pore size). There may be times, however, when one may wish to separate minerals by density but examine them with refractive index liquid other than 1.584. This can easily be done by modifying the procedure slightly in this way. After the sample has been spun, th e mnterinl on the bonom of the tube is transferred to a second centrifuge tube by micropipettc. If the heavies are of interest, distilled water is added to this second tube. If the float is of interest the distilled water is added to the original tube. O nce the heavy liquid is mixed with distilled water the density is lower | than the minerals, either float or heavies, so that the sample can be spun down in the centrifuge. The i liquid is removed with a micropipette and fresh water added. After spining down in distilled water five or six times, the sample is transferred with a drop of water to a glass slide. After it is dry. any refractive index liquid may be used. Figures 10 and 11 show an example of the same sample prepared on a filter and on glass. The counts are essentially the same. This procedure has been used for concentrating quartz from talc samples and for obtaining tremolite counts on acid insoluble residues of carbonate rocks. Work on these and other applications 567 Protected Docum ent-Subject to Protective Order J&J-0049179 JN JNL61 000052441 References 1. Occupational Safety and Health Administration. Occupational Exposure to Asbestos. Trcm olitc. Anthophyllitc and Actinolltc. Final Rules 29CFR Parts 1910 & 1926 (1972, 1976, 1986). 2. Occuplional Safety and Health A dm inistration, Hazard Com m unication. Final Rule 29 CFR Part i 1910 (1983). 3. Occupational Safety and Health Administration, Stay of Final Rule, Federal Register, Oct. 17. 1986. April 30. 1987 & July 20. 1988. 4. International Agency for Research on Cancer. ' Silica and Silicates." 1ARC M onograph. 42 (1987). 0-289. 5. L. B. M cCronc, "Analysis o f Talc by X-ray Diffraction and Polarized Light Microscopy" (NIOSH Report - Contract CDC 210-75-0063, 1977). ( M l. 6. Food and D rug Administration. Asbestos Particles in Food and D rugs. Federal Register. Sept. 28. 1973. 27076-27081. 7. W . R. Foster. "Gravity-Separation in Powder Mounts as an Aid to the Petrographer." American M ineralogist. 32 (1947). 462-467. 8. B. M . Shaub. 'U sing the Microscope for Specific Gravity Determination of Minute Mineral G rains," American M ineralogist, 44 (J959), 890-891. 9. F . D. Bloss. An Introduction to the Methods of Optical Crystallography (New York. NY: Holt. Rinehart & Winston, 1961), 0-294. 10. W . C. T roger. Optical Determination o f Rock-Forming M inerals (StuttartrE. Schwelzerbart'sche Verlagsbuchhandlung. 1979). 1-188. 11. P. L. Hauff and J. Aircy. 'T h e Handling of Hazards and Maintenance of Heavy Liquids in the Geologic Laboratory." United States Geological Survey C ircular. 827 (1980), 0-24. 12. A. Riedmiller. P. L. H auff and R. W . M athias. "The Dangers and Handling of Hazardous Chemicals in the Geologic Laboratory." United States Geological Survey C ircular. 924 (1984) 0-39. 13. M . Allman and D. F. Lawrence, Geological Laboratory Techniques (New York. NY: Arco Publishing Co., Inc., 1972). 0-335. 14. C. S. Hutchison. Laboratory H andbook of Petrographic Techniques (New York. NY: John Wiley & Sons. 1974). 192-214. I 15. R. Sacher, private communication with author. R. P. Cargille Laboratories. Inc.. 4 January. 1989. 16. Beckman Instruments. In c..'In stru c tio n s for Using the Type 80 Ti Rotor" (Instruction M anual for the Beckman Class F , G. H & R Preparative Ultraccntrifugcs. 1988) 6-7. 17. D. W . M ing and J. B. Dixon. "Technique for the Separation of Clinoptilolite front Soils." Clays and Clay Minerals. 35 (1987) 469-472. 18. J. L. W ooden, private communication with author. U. S. Geological Survey. 29 O ctober. 1987. 19. ASTM. D4532-85 Standard Test M ethod for Respirable Dust in the Workplace Atmosphere. 569 Protected Docum ent-Subject to Protective Order J&J-0049180 JNJNL61 000052442 ! I Annual Book of ASTM Standards (1985). 20. NIOSH. "Asbestos Fibers in A ir," Manual of Analytical M ethods. I (1977) 239:1-239:21. 21. Occupational Safety and Health Adminstration, Air Contamination. Final Rule 29 CFR Part 1910 (1989). 22. E. J. Chatfidd and G. M . Lewis. 'Examination of Vermiculite for the Presence of Asbestos Fiber" (Vermiculitc Research & Development Report 22056-2. 1979). 0-22. 23. W . J. Campbell. E. B. Steel. R. L. V irla and M. H. E isner, "Relationship o f M ineral Habit to Size Characteristics for Tremolite Cleavage Fragments and F ib e rs.' U, S. Bureau of M ines Report of Investigations. 8367 (1979) 0-18. 24. A. G. W ylie. R. L. Virla and L. Russck, 'C haracterizing and Discriminating A irborne Amphibole Cleavage Fragments and Amosite Fibers: Implications for the NIOSH Method." American Industrial Hygiene Association Journal. 46 (1985) 197-201. 25. A. G. Wylie, 'Relationship between Growth Habit of Asbestos and the Dimensions of Asbestos Fibers." Mining Engineering (1988) 1036-)040. i i Protected Docum ent-Subject to Protective Order 570 i l I J& J-0049181 JNJNL61 000052443 f s' Environmental Health Perspectives k>/. 94. pp. 225-230.1991 Amphibole Content of Cosmetic and Pharmaceutical Talcs by A. M. Blount* Pharmaceutical and cosmetic-grade tides were examined for asbatUonn amphflxde content using a new density-optical method. Tides under the Food and Drug Administration are not regulated as to asbestos content; however, all talcs were well below the level mandated by the Occupational Safety and llcah b Administration for industrial U k s. Only one was found to contain an amphibole particle size distribution typical o f asbestos. Introduction In 1973 the Food and Drug Administration (FDA) proposed a regulation on the permissible asbestos content of laic ( /) . This regulation proposed to limit the amount of amphibole m inerals to less than 0.1 % and chrysotile to less than 0.01 %. However, the optical microscopy method proposed was so com plicated, lengthy, and subject to error that the proposed method was never finalized. Since then no final ruling has been issued. The Occupational Safety and Health Administration, on the other hand, has been more rigorous and has instituted regulations despite the lack o f methods to carry out the required measure ments. One regulation, instituted in 1986, defines amphibole minerals as asbestos if the length to width ratio is 3:1 or greater. Because many nonfibrous cleavage fragments of amphibole minerals have a 3:1 aspect or greater and because there is no good evidence for adverse effects of these particles, a stay has been in affect on this part of the regulation (2). The second applicable regulation is the Hazard Communication Regulation (3), which applies to all chemicals used in the workplace. Specifically, it re quires labeling of substances containing > 1% of a chemical hazardous to health and > 0.1% of a carcinogenic chemical. Unfortunately, asbestos and amphiboles cannot be measured using currently developed methods to the level of 0.1% in the presence of talc. Some investigators have suggested that tremolite can be measured to that level by X-ray diffraction. But others have shown that the peak intensities vary between nonfibrous and fibrous tremolite (4) so that the 0.1% level of detection and measurement is doubtful except in cases where the sample has been spiked so that the exact nature of the tremolite is known. For anthophyllite there is little argument about the fact that detection cannot be made to 0 .1%. However, the main problem with using X-ray diffraction for detection of amphibole minerals is that it gives no information about the shape of the particles, and shape is important in view of the uncertainly in the outcome o f the asbestos regulation pertaining to nonfibrous amphiboles. Geology Department. Rutgers University, Newark. NJ 07102. The talcs that are pharmaceutical grade fall under the domain of the FDA and are therefore nonregulated in regard to fibrous mineral content. In the course of developing a technique to facilitate quantification of amphiboles in talc (5). pharmaceutical and high-grade talcs were examined. They were found to have very low amphibole content and. because of this, were extensive ly used in examining the lower limit of detection of the new method. The purpose of this paper is to describe the results of analyses for content and shape of amphibole mineral fragments in cosmetic and pharmaceutical talc powders ofthe United States. Methods The method proposed by the FDA in 1973 for analysis of talc was an optical procedure as described below (7): Weigh oui 1milligram of a representative portion of talc on each of two microscope slides. Mis the talc with a needle on one slide with a drop of 1.374 refractive index liquid, and then (he other with 1.390 liquid, and place on each a square or rectangular cover glass sufficiently huge so that the liquid will not run out from the edge (ca. 18 mm square) and will provide a uniform particle distribution. Fibers counted by this method should meet the following criteria; (!) Length to width ratio o f3 o r greater (ii) length of 3 pm o r greater (iii) width of 3 pm or less. Count and record the number of asbestos fibers in each I milligram as determined from a scanofboth Slides with a polarizing microscope at a magnification of approximately 4 0 0 x . In the 1.574 refractive index liquid, chrysotile fibers with indices less than 1.574 m both extinction positions may be present: in the 1.590 refractive index liquid, the other five angrhibole types of asbestos fibers with indices exceeding l-590in both extinction positions may be picscm. Check the extinction and sign of elongation for tentative identification. For specific identification of asbestos fibers, make additional mounts in appropriate refractive index liquids, and refer to the optical crystallographic data in the table. A ctsunl of not more than 1000amphibole types of asbestos and not mote than MX)chrysotile asbestos fibers per milligram-slide constitutes the maximum limji for the presence of these robestos fibers in talc. These limits assure a purity of at least 99.9 percent free of amphibole types o f asbestos fibers and at least 99.99 percent free of chrysotile asbestos fibers. The problem with the proposed method is that talc flakes are often oriented vertical ly o r at a sufficient angle that they appear to be needles and thus must be tested for refractive index (Fig. 1). A typical number o f such panicles is five per field o f view. This Protected Docum ent-Subject to Protective Order J& J-0049182 JNJNL61_000052444 y 226 A. M. BLOUNT Figure I. Talc (laXcs in 1.584 refractive index liquid. Note that there arc pani cles in this field that have aspect rai 105 greater than 3:1. Width of view 0.13 mm. means that some 20.000 panicles would need to be examined in a typical ease. In additon, chlorite is often present and when on edge must be examined in two extinction positions. This is clearly beyond what could be expected of any sane microscopist for a routine analysis. Since no other procedure has been developed as an alternative, a compromise has been to count 100 fields of view (FOV). In this way one need only examine about 500 par ticles in detail. Because 500 panicles is still a lengthy process, a more rapid and equally accurate method has been developed based on con centrating theamphibole particles by density difference. Figure 2 illustrates that there is a distinct break in density ranges be tween talcs and amphiboles. A heavy liquid of intermediate den sity is used, either Klein's (cadmium borotungstate) or Clerici's (thallium fomiate-malonate) solution. Experimentation showed that a heavy liquid of density 2.810 gives good separation even though values given in the literature and shown in Figure 2 would suggest that the density should be slightly higher. Because the density difference between panicles and liquid is small, to get separation in a reasonable length of time a microcentrifuge is used with tubes containing 1.5 mL liquid. The height of the li quid column is. in this case, about 10 mm. : : 1-- i 1 C u m m m g lo rn if > t ]|< I I ! 1 1 I 5 m o llir 1 1 1 1 1 1 A h o o ter 1*1 ^ J I _______ 1t ? E ; - 1 i1 3 - 1 Ar> IJ o t ^ r f . T " _______ T " ............................ 3 1 3. i j Figure 2. Specific graviiics of laic and amphibole (6). The general procedure involves weighing about 60 mg sample into a microcentrifuge tube and adding heavy liquid of density 2.810. After these are mixed, the tube with sample is placed in a vacuum for 3 min to remove the small bubbles adhering to the panicles. After centrifuging the sample for 10 min at 7000 rpm. the heavy panicles are removed from the bottom of the tube with a micropipette. The counting of panicles can be done either on a membrane filler (Nuclepore. 1.0 /un pore size) which has been placed o n a microscope slide or as panicles directly on the glass slide, in the first case, the heavy liquid with sample is forced through a mem brane filter followed by distilled water to clean out the heavy li quid. The filter is then placed on aglass slide while wet. When dry. 1.584 refractive index liquid is placed on the filter followed by a cover glass. The photographs shown in this paper are of par ticles on filters. The second case, panicles directly on the microscope slide, re quires transferring the heavy panicles and some of the heavy li quid to a second centrifuge tube. Distilled water is added and the sample centrifuged. The liquid is pipetted off and more distilled water added. This is repeated several times to clean out the heavy liquid. Finally, the panicles with several drops of water are transferred to a glass microscope slide. The advantage of this pro cedure is that any refractive index liquid can be used, whereas, in the former case, the refractive index is constrained by having to match the index of the membrane filter (either 1.584 or 1.625). The 1.584 value is good for analyzing amphiboles in talc, but the centrifuge method described has application to other mineral combinations, such as talc-quartz. With other combinations, refractive indices other than the two exhibited by the membrane filter may be more appropriate. The panicles are counted in 20 FOV. Being concentrated from 60 mg or more of sample, one will see more amphiboles than in 100 FOV using the old method. The number of amphibole par ticles per milligram (ppmg) is calculated: ppmg = amphibole particles/mg = (number of amphibole counted/number FOV counted) x total number FQV (efficiency) x (number of mg of sample) Efficiency of the spin-down is determined experimentally. For more details of the method see Blount (5). Figure 3 illustrates the results obtained when testing the method using known mixtures. Because it is difficult to measure and mix in very small weights of amphibole. a sample contain ing 2% tremolite in talc was mixed with pure talc to make mix tures containing very low percentage values of tremolite. For ex ample. sample A (Fig. 3) consisting of 0.06% tremolite was made by weighing 58.9 mg of pure talc with 1.7 mg of talc containing 2% tremolite (1.7 mg/60.6 mg x 2% = 0.06%). It is not neces sary to make a homogeneous mixture since the entire sample was used in the experiment. Also, the talc containing amphibole was put in the tube second in order not to give the amphibole any " head-start" in sinking to the bottom. The centrifuge method was also tested with a commercial talc. 100 FOV were counted in ten 1-mg samples according to the FDA procedure for amphibole. This was compared with 20 FOV counts on 60-mg centrifuge samples (Fig. 4). The agreement is quite good. The standard deviations were determined in two Protected Docum ent-Subject to Protective Order J&J-004S JNJNL61 AMPHIBOLE CONTENTOF TALC JO1 A 6 227 1.0 % ! E K Fkajrk 3. Percem irtmolite intalcas dettrmined by ihe centrifuge/optical method (shided ban) compared with lhai actually present m cxpcrimrraal mixtures (black bars). The dashed pan of the shaded bars indicates + 2 5D (right arrow) or - 2 SD (left arrow). overage o f 10 ro m p t '' '' I I I 100 200 300 400 500 600 PPMG Fkujrk 4. Comparison of traditional (100 FOV) count with cenlrifuge/opttcaJ count of same talc. The three lower b an indcate the values in panicles/mg obtained by the cemrifugc/opticaJ method for three 60*mg samples. The top bar is the average of ten 100FOV (tradhional method). The dashed pan of all the bars is +2 SD. ways: for the traditional method by calculating in the usual way from multiple analyses and for the centrifuge method by means of the Poisson distribution from single counts. Standard devia tions are high for the centrifuge method because of the very few panicles counted. These could be decreased by making a larger count, but isnee the purpose of the study was to find a reasonably rapid method of monitoring amphibole content of talcs, larger counts were not generally made. Results High-grade talc products from five deposits in Montana, three in Vermont, and one each in North Carolina and Alabama were examined using the centrifuge/optical method. In addition, four talcs from outside the U.S. but available in the U.S. market were included in this study. Talcs from other districts in the U.S. were examined, but these talcs had grades with less stringent re quirements and are not included in this report. Results of panicle counts are shown in Table I. The FDA has equated 0.1% with 1000 panicles per milligram. In order for am phibole particle content to be less than 0.1%. 20 or less panicles must be observed in 20 FOV (5). Since all were well below this value, more extensive counts were not generally made. It should be borne in mind that the 0.1% indicated is percent by count and not percent by weight or volume. The question of the validity o f this relation has been considered (5). Briefly, the relation implies (1000 am phibole particles)/(1.000j000 total par ticles) . Counts of total panicles per milligram of talc have shown that 1 million particles per milligram of talc is a low value. Most show at least 2 to 3 times this number. The only exception was a bahy powder with very large flakes which showed 0.4 to 0.8 m illion particles per milligram. It was not clear, however, whether this was a true value or due to the problem of counting where large, flakey panicles could potentially hide other par ticles even in the most carefully prepared samples. Using 1000 particles/mg = 0.1 % would, in most samples, give a percentage value on the high side and in this sense be a conservative answer. The counts shown in la b le 1 were made of regulatory fibers i.e., aspect ratio > 3:1. In some samples there were as many or more nonregulatory particles of amphibole as regulatory fibers. The shape of the amphibole varies greatly and seems to be highly characteristic of each deposit. In Table 1, the panicles having aspect ratios less than 6:1 are designated cleavages and prismatic pieces. Those greater than 6:1 and less than 15:1 are labeled Protected Docum ent-Subject to Protective Order J& J-0049184 JNJNL61 000052446 I 228 A. M. BLOUNT Table 1. Counts of regulatory fibers in processed talcs. Count*, Sample particles/mp SD Panicle shapes Panic les/FOV' A 38 25 Cleavages 3/100 B ND" 0/20 C ND 0/20 D < 25' Cleavages 0/20 E ND 0/20 F ND 0/20 G ND 0/20 H 17 17 Cleavages and 2/20 needles I 226 59 Needles and fibers 17/20" 283 100 Needles and fibers 8/20 291 98 Needles and fibers 9/20 341 108 Needles and fibers 10/20 102 51 Needles and fibers 3/20 J 25 14 Cleavages 1/20 27 27 Cleavages 3/20 K 25 25 Cleavages 1/20 L <10' Needles 0/20 M 39 21 Cleavages and 4/20 fibers N 25 17 Prismatic pieces 3/20 O ND 0/20 'FOV. fields of vie* *ND. none detected. `No panicles seen during a 20 FOV count, but some panicles could be seen during a random scan of the filter. Value shown is the lower limit ol detection. '`Large sample used for this analysis (305 mg). `needles." The remainder, which are greater than 15:1, are labeled "fibers.`` Whereas in many samples only a few particles were counted as shown in the right-hand column of Table I . it should be remembered that even if only one particle was present in 20 FOV that about 300 were present on the slide. Because of the low interference by talc particles, these were seen so that it was easy to gel a sense of the general particle shape. The shape distribution of panicles for several samples was determined. Figure 5 shows a photograph of a particle of tremolite in sample /. The panicle is composed of fibrils. The length and width of 100 amphibole particles in this talc were measured. The resulting distribution of aspect ratios is shown in Figure 6. The results when compared with the aspect ratios determinded for tremolite asbestos with SEM by Campbell et al. (7) show sample / has a distribution similar to asbestos. Sam ple M was analyzed in the same way (Figs. 6 and 7). The graph of aspect ratio verses percent is compared with Campbell's results for nonfibrous tremolite. The similarity of the curves in dicates that the tremolite in this talc is of the nonfibrous type. Because the fractions produced by centrifuge are not generally pure after a single spin-down, a sample containing a variety of particle shapes was tested to see if the aspect ratio distribution results become biased in favor of larger, chunky grains (low aspect ratio) over small, long grains (high aspect ratio). The sample used contained 6.5% tremolite. a sufficient quantity that the traditional optica) method could be used to compare with the centifuged sample. The resulting aspect ratio distribution curves (Fig. 8)donot show significant differences. With the traditional method, 69% of the amphibole panicles have an aspect ratio of 3 :1or greater, whereas for the centrifuged samples the value is 64 %. a variation which is not significant. The differences shown for 5 : 1and 10:1 are probably due to the limited num berof par ticles measured, in this test 100 panicles in each sample. Despite the similarity o f the curves. the mean length and mean width of the amphibole particles measured using the centrifuge method are greater than those obtained using the traditional method (Table 2). Analysis of size distribution indicates that the proportion larger than 15 pm is greater in the centrifuged sam ple. This difference in dimension distribution does not appear, however, to affect the aspect ratio distribution. Other invest igators have found that as panicles increase in length, the aspect ratio shifts to higher values [8.9). This applies to both asbestos and nonasbestiform amphiboles, so presumably the effect of centrifuging down longer particles would be to force the aspect ratio distribution peak to higher values. Discussion The high-grade talc powders are uniformly low in amphibole content. Counts obtained were 0 to 341 particles/mg. Indeed, talc from some districts appears to be completely free o f such minerals. In those containing amphibole minerals there are two distinct types: cleavage type and asbestos type. These two types show distinctly different aspect ratio distributions as demon strated in Figure 6 (samples / and M). The aspect ratio difference probably accounts in a large part for the higher particle count per milligram of sample / compared with the others which show cleavage fragments. It is easy to see that the number o f particles showing greater than 3:1 aspect ratio would be greater in the former case even if the total number of particles o f amphibole were equal. This observation reinforces the original decision to count particles visually rather than attempting to use X-ray dif fraction. It is not wise to try to convert information on dimen sions to percent by weight o r volume because a few very large particles can drastically affect the resulting value. Campbell et al. (8) discuss this in some detail. Figure S. Panicle ot amphibole in centrifuged sample /. Width of view 0.07 mm and 1.584 refractive index liquid. Particle is on a membrane filler. Protected Docum ent-Subject to Protective Order J8.J-0049185 JNJNL61_000( t amphiboif. contentof talc 229 % Tremdite atbnlos F icure 6. Percent amphiboles in each aspect ratio group for talc sample / (left) and M (right) compared with tremolite asbestos (7) and ncmolitc (nonasbestiform) f. Figure 7. Particle of ampbibole in centrifuged sample M . Width of view 0.07 mm and 1.584 refractive index liquid. Article is on a membrane filter. FIGURE 8. ftlrcenl amphiboles in each aspect group (or a sample handled in two ways: solid line shows results using traditional method and dashed tine shows results using centrifuge method. Dimensions of 100 particles measured for each curve. Protected Docum ent-Subject to Protective Order J&J-0049186 JNJNL61 000052448 230 A. M. BLOUNT Table 2. Summary of sizr and aspect ratio data used to construct Figure fL Method Traditional Centrifuge 5-10 fim 57 33 Size. X 10-15 pm 26 27 15 pm 16 38 Traditional Centrifuge Mean length, urn 12.5 17.5 Mean width, /m 3.0 4.7 Mean aspect ratio, am 4.4 4.6 Further, the results from this study demonstrate the utility of the centrifuge method not only for obtaining a count of particles, but also for obtaining information on the shape o f particles in a population. It should be emphasized that the aspect ratio curves determined for samples /and M would have been virtually impos sible to obtain using the FDA procedure. The determination would have required examining over 3000 FOV. As indicated previously, many talc flakes on edge appear to be fibers and must be examined during such a scan, making the wholejob impossibly tedious. Finally, even in those cases where one may wish touse the stand ard 100 FOV cou nt. the ccntri fiige method offers a way to screen samples between those times when a more lengthy count is made, and it permits a double check ofvalues sodetermined. In addition, the tendency to bring down a disproportional numberoflarger par ticles has the advantage that with true asbestiform amphiboles one generally sees some particles showing bundles of fibrils which removes any doubt about the nature of the amphibole. REFERENCES 1. Food and Drug Administration. Asbestos Fortifies in Food and Drugs. Fed. Reg. 28: 27076-27081 (1973). 2. Occupational Safety and Health Administration. Occupational Exposure to Asbestos, Tremolite. Anthophyliite and Actinolttc: Extension of Partial Stay and Amendment of Final Rule. Fed. Reg. 35: 50685-50687 (1990). 3. Occupational Safety and Health Administration. Hazard Communication: Final Rule. Fed. Reg. 25: 53280-53348 (1984) 4. McCrone. L. B. Analysis o f Talc by X-Ray Diffraction and Polarized Light Microscopy. NIOSH Report. Contract 2K375-0063: 0-41. National Institute of Occupational Safety and Health. Cincinnati. OH. 1977. 5. Blount. A. M. Detection and quantification of asbestos and other trace minerals in powdered industrial-mineral samples. AIME Process Mineral. 9: 557-570 (1990). 6. Troger. W. E. Optical determination of rock-forming minerals. E. Schwcizcrbatt'schc Vfcrlagsbuchhanlung 0-188. Stuttgart. Germany. 1979. 7. Campbell. W. J,, Blake. R. L.. Brown. L. L.. Caiher. E. E.. and Sjoberg. J. J. Selected Silicate Minerals and Their Asbestiform Varieties. U.S. Bureau of Mines Information Circular 8751: 0-56. Pittsburgh. PA. 1977. 8. Campbell, W. J.. Higgins, C. W.. and Wylie. A. Chemical and Physical Characterization of Amosite. Chrysotile. and Nonfibrous Tremolite for Oral Ingestion Studies by the National Institute of Environmental Health Sciences. U.S. Bureau of Mines Report of Investigations 8452: 0-63. Pittsburgh. PA, 1980. 9. Wylie. A. G. Relationship between the growth habit of asbestos and the dimensions of asbestos fibers. Mining Engineer. 40: 1036-1040 (1988). Protected Docum ent-Subject to Protective Order J& J-0049187 JNJNL61 000052449