Document ppvjpmJegrjyK2w4Ow3QGdz6k

L'.S. DEPARTMENT OF LABOR Occupanonal Safety and rUalth Admjniscra:;or. WASHINGTON, D.C, 1C210 AIA-70 < 10 FEB 1577 MEMORANDUM FOR: REGIONAL ADMINISTRATORS AND AREA DIRECTORS FROM: Donald E. MacKenzie, Acting Director, Office o Coordination, and Experimental Programs SUBJECT: Asbestos sampling of vermiculite processing On February 1, 1977 OSHA received the enclosed report which indicates that asbestos fibers have been detected in samples of vermiculita ore. When vermiculite is subjected to strong heat in industrial processing, it exfoliates or separates into thin sheets. It is suspected that asbestos fibers may be released by this process and be present in e< fine duet with the final product. Although the enclosed study does net indicate the degree of hasard since fiber counts were not performed, the potential for employee exposure to asbestos can be inferred. Therefore, future inspections of exfoliation processing of vermiculite ore shall include an evaluation of employee exposure to asbestos fibers. AIA-70 Mineralogiesl analysis of ore from a major U.S, vernleuii.ee" deposit: ' preliminary investigation. Problem.: Versionlite is a mica that exfoliates under strong heat into very thin sheets. The resulting lightweight expanded form makes it useful as in sulation, among its many applications. A sample of raw veraiculite ore from the major producing mine in Montana was analyzed by x-ray diffraction and electron microscopy. The major uses of verniculite include concrete, plaster and cement aggregates; loose fill, block, pipe covering and packing insulation; soil conditioning and horticulture, fertilizer carrier and litter. The U. S. production in 1971 was 301,000 tons, and output is increasing at a rate of 6% annually. Geological considerations suggest that the ore might contain chrysotile and/or tremolite asbestos. If this be found to be so, the many industrial and consumer applications of vermiculite raise the question of whether there exists possible occupational or environmental hazards as a result of exposure to asbestos-containing dust. Materials and methods; We have examined ore samples from a major U. S. vermiculite source. Our preliminary results indicate that a broad spectric of verniculite ores from domestic ar.a imported foreign sources should be analyzed for their asbestos content, both qualitatively and quantitatively. A representative number of vermiculite products, especially consumer products such as potting soils and litter, should also be examined. These can be expected to release respirable dust during use. The methods of analysis for as bestos are x-ray diffraction in the step-scanning node and electron mi croscopy. Prior to analysis, the sample should be slurried and subjected to ultrasonic energy (e.g., in a sonifier cell disrupter) for about one minute in order to liberate chrysotile and other asbestos fibers which grow between structural layers of verniculite mica sheets. Results to date: AIA-70 Trerolite and chrysocile asbestos have been, found in. veraiculite ore samples. (Figures 1-3) The amounts of fiber have not yet been measured, Sicnificance: The results indicate that, as, a result of the lightweight expanded fora that rakes veraiculite a valuable material in many industrial and consumer applications, potentially hazardous concentrations of asbestos nay be con tained in the dust produced by the essential stage of expansion. Publications: To be published. Investigator: A. Rohl, Ph.D. Support: Health Research Council, U-1272 Period: 1973- 275 Dl-u- AIA-70 Figure 1- (upper left) Electron photomicrograph of raw vermiculite ore, showing large and small fibers of tremolite. 3200v magnification. Figurg 2. (upper right) Electron photomicrograph of raw vermiculite ore, showing a fiber bundle of chrysotile asbestos. 5000:' magnification. Figure 3. (lower left) Electron photomicrograph of raw vermiculite ore. A large bundle of chrysotile protrudes from a verrniculite mica flake. lO.OOOx magnification. Figure 4. (lower right) Electron photomicrograph of raw vermiculite ore. A fiber of tremolite asbestos is at bottom center. 10,000x magnification '0 AIA-70 277 01. - J i LG) 5"5 - c a