Document gavR9oZg3XQKGxQXkJ2wJx5eG

UNITED I SIERRA Dl\IISlON BOX 1201 CYPRUS TELEPHONE TRENTON, NEW JERSEY 08606 MINES CORPORATION 609 l 883-5111 TWX 510 l 685-9585 December 21, 1973 Hearing Clerk Food & Drug Administration Room 6-86 5600 Fishers Lane Rockville, Md. 20852 Subject: Asbestos particles in Food and Drugs, the subject of proposed rulemaking of the Food and Drug Administra.tion, Federal Register, Vol. 38, No. 168, g/28/73, (21 CFR Parts 121, 128 and 133) Dear Sir: As a. ma.jor talc producer, this division is vita.lly concerned with this subject. On September 7, 1972, we commented on the Federal Register publication of August 12, 1972 proposing regulation of asbestos-containing talcs for food additives. A copy of this letter is a.tta.ched for your reference. We have, since that time, carried out numerous progra.ms designed to identify and quantify asbestos impurities occurring in talcs of various origins. Methods tried include transmitting and scanning electron microscopy for fiber detection; electron and X-r diffraction; and X-ray fluorescence for mineral identification. We also carried out extensive work using the proposed optical pala.rizing_~~cro~.~opy method, _ We found this method uncertain and mislea.ding with indentification of asbestos erring both positively and negatively. The reason for this is that some talcs have been observed with indices of refraction in excess of 1.5928 for r)y while some fiber bundles ha.ve given refra.ctive indices below 1.5928 for qo and higher than 1.5928 for QY . Therefore, distinguishing amphibole a.sbestos from fibrous talc (or talc plates on edge) in the 1.59 liquid is subject to considerable difficulty, As an alternative method for tremolite, we repeat our easlier suggestion that X-ray diffraction be the basic tool. We have refined this technique and are now a.ble to state: CAM-46 . - , .. 0 -2- Tremolite can be determined quantitatively in talc by X-ray diffraction and X-ray spectrometry. The tremolite pea.k at 8.38 a. u. can be semi-quantitatively determined by normal powder diffraction techniques in the presence of chlorite and talc using a. scanning technique and Cu ho radiation with a. monochromafor. The results can be confirmed and made more quantitative by making X-ray spectrometer determination for calcium in the talc material before and after acid leaching to remove calcium compounds such a.s dolomite a.nd calcite. Tremolite contains calcium oxide in the approximate level of 140/o, and the CaO level can be determined easily to 0.0150/o, equiva.lent to 0.105% tremolite. The acid leaching at low temperature affects neither the talc nor tremolite. Unfortunately quantitative chrysotile determination in talc is a.more difficult problem which requires a. combination of techniques. The scanning electron microscope technique permits rea.dy identification of a.sbestos forms, pa.rticula.rly with tilting sta.ge and in the high magnification range. The scanning electron microscope can show chrysotile fibers which are not present in sufficient quantity to show in normal powder diffraction techniques and optical microscopy. Transmission electron microscopy of higher magnification can be of value for observing chrysotile fibers, and electron diffraction used in conjunction with the transmission microscope can permit single fiber determinations. It is noted that Colgate Palmolive Company, Research and Development Department, Research Report 2675, August 15, 1973 states one worker has reported successful determination of chrysotile in talc by the X-ray diffraction technique for powder sa.mple and step scanning technique, but United Sierra. has not ha.d an opportunity to attempt this procedure in detail with the step scanning procedure. It is reported to ha.ve success with a. lower limit of detection of 0.2% chrysotile We evaluate our own production talcs routinely via. X-ray diffra.ction with or without step scanning depending on tremolite content. If we are concerned with very small a.mounts of tremolite, t he XRS after acid leaching described above is also used. Since tremolite is the only asbestos impurity with which we contend, and only then in sma.11a.mounts in certain California. talcs, these measures suffice our normal needs. Work on competitive talcs, which may or may not contain chrysotile is carried out via. scanning electron microscope using electron diffraction for positive identifidation of individual fibers. Recommendations We recommend that the proposed identification method be rejected and that: . . 1. X-ray fluorescence after acid leaching be adopted as the official method for tremolite determination. Accuracy to 0.2% can be obtained. 2. A program involving government and industry to establish a.more accurate, simpler method of chrysotile detemination be instituted. This division would be pleased to pa.rticipa.te in such a progra.m. Very truly yours, UNITED SIERRA DIVISION Cyprus M..i-n-Ie,s Corporation ,f;pcfzy3-7zG&im H. T. MUIRYAN President HTM:EE Y',`ercfcr to the Tc&rnl i?c:,tr L,nr document of Augst 12, 1972 concerning propored rr@ationa for asbestos conbinin~ talcs as food additives. In this connection we should like to make the followins comments: Corscming the quoted article in Ykience~~, the basis for its discussion is very r:ea!< and hypothetical as the subsequent letters from the readers of the mzgaziue proved. Koreovcr, the term ttasbestos-form't is, in our opinion, arbitrary in that any fibroEs material inciuding such materials as cetlutose, cotton, etc. could be cons ldered "a&es tos form". Y,`P bcllieve Oat the various types of asbestos, that is, chrysotiie, crocidolftc , anthophyllite, tremolite, etc. should be spelled out as the contaminant. This has the double advantage of atso providing a satkfactory means of crclyzix7 for the e&estos impurity. We believe this matter has been brought to your attention in connection with cosmetic talcs. Our opinion, as v/e11 as that of many others, is that the X-ray diffraction method of detecting ascestos mtiierals mineraiogicalfy is the qutckest and most acczxnte clFtl!o:I?. It can detect 8~: little C?FITS of these impurities and ciearly di--+.*;L?yy,-wishes them from other minerals including talc, vzhich may take the form of a fiber or rollt,?d-up pi2telct. Tire proposed rcigu?ation makes no reference to the size of the contaminating fibcre. Li$eratum2.-ecl2ar:y tnc::cates t:lat. the range of 5 to 50/4m in length is considered hazardous; smaller or larger particles not. Very truly yours,