Document 0qjJ1JNgJg4XynX9q0kMqV6nd

FILE NAME: W hip-Mix (WM) DATE: 1977 DOC#: W M 003 DOCUMENT DESCRIPTION: Army Report AD A 045,02 ? s e y s i v v C L A S S IF IC A T IO N O F TH IS P A G E fWh.TM D . r . E n t.r.d ) ZT REPORT DOCUMENTATION PAGE ' BEPgSTNUMBER 2, G O V T A C H S S IO M & IO . icf Suli.) (I Asbestos: A Subtle Carcinogen in the Dental > Laboratori' SB1and Microprobe Study. RAEDCIONMSTPRLUETCTINIOONFSORM IEh T' S C A T ALOC. N U M BER 5. T Y P E O F R E P O R T 1 P E R I O D C O V E R E D MTaniuils^cTript~ifo11r|| TT F e w FO RNIN O ;rrr B*E./Cutright, EiF./Huget^aafi J9U./Brady S. C O N T R A C T O R G R A N T N U M B E R . P E R FO R M IN G ORGANIZATION N AM E ANO ADDRESS GS Amy Institute of Dental Research v Walter Reed Army Medical Center g a s iiin g to n -D .C .__ 20012 I. CO N TRO LLIN O O F F IC E NAME ANO AOORESS 61102A 04 010 OS Amy Medical Research & Development Camand(/ef7 feptaWfaMr g T ^ 1 S2DA (S G R D -R P) ' n u m b e r o f peaces i7p=;hirotnn D C 20314. 1. MONITORING A G E N C Y NAM E A O O R E S V dtltmnn l from Controlli* O iflcoJ IS. S E C U R IT Y C L A S S . f o f u i l i UNCLASSIFIED IS*. OEC LASSIFtC ATIO N /D O W N G R AD ING SCHEDULE It. DISTRIBUTION S T A T E M E N T (o l th ia Jlapori) This document has been approved for public release and sale; its distribution is unlimited. IT. DISTRIBUTION S T A T E M E N T (o f the ab.trm sl m Im W in Bina* 20. it d itta rm i tram Empori) jqC IB. S U P P LE M E N T A R Y N O TES IS. K E Y WOROS (C ontim i, on N T H o ld . It H H U M T m i tornititr *T loe numb.r) Asbestos; chyrsotile; carcinogen; S.E.M., microprobe, dental hazard Particles of debris emanating Ipoa an asbestos containing dental laboratory material were characterized with 4Jie scanning electron microscope and x-ray microprobe. The dimensions and comi.position of these particles suggest their potential to behave as subtle carcino- Vr'ith almost daily use of dust producing asbestos in the dental laboratory, improper Handling of this substance could be hazardous to the health of den- personnel. It is recommended that high standards of personal and laboratory ene be enployed in the handling of asbestos. toRM irn I JAM W / l EDITION OF t Neva IB OBSOLETE UNCLASSIFIED secu rity < w ASBESTOS: A SUBTLE CARCINOGEN IN THE DENTAL LABORATORY SEM AND MICROPRDBE STUDY Duane E. Outright, D.D.S., Pb.D.* Eugene F. Huget, D.D.S., M.S.** John M. Brady, D.D.S., M.S.*** U.S. Army Institute of Dental Research Valter Reed Army Medical Center Washington, D.C. 20012 Commercial materials and equipment are identified in this report to specify the investigative procedure. Such identification does not imply reoomnendation or endorsement or that the materials and equipment are necessarily the best available for the purpose. * Commander, U.S. Army Institute of Dental Research ** Chief, Division of Dental Materials Chief, Department of Biophysics Risks encountered in dental practice have become foci of a nuntoer of studies. Dangers associated with the inhalation of particulate matter (bacteria, viruses, enamel, dentin, calculus and amalgam) from microbial aerosols1'2 produced during the use of high-speed rotary instruments have been addressed. Also, investigations have been conducted to establish and to define acceptable limits for operating room levels of mercury vapor3-5 and of nitrous oxide."" Recently, concern has been shown for asbestos fibers which emanate from the powder conponent of some periodontal dressings as well as from liners for casting rings and crucibles. The present study was conducted to sanple and to characterize particulate debris encountered in the use of asbestos in the dental laboratory. MATERIAL AND METHODS A. A three-inch segment of one-inch wide ring liner was tom from a roll of asbestos* by each of two laboratory workers. Particulate matter re maining on the thuobs and index fingers of the test subjects was removed with the use of acetate tape. Additionally, the sites from which debris had been removed were resanpled after the workers washed and dried their hands. Ttoo three-inch strips of the asbestos were heated in a burnout furnace at 1,300PF. for 45 minutes. The strips were cooled to roan temperature in open air and tom by two volunteers. Sampling of particulate matter from the thumbs and index fingers of these individuals was accomplished as de scribed above. __ B. Samples of debris were collected on acetate tape from a bench top upon which 20 phosphate-bound investment molds had been broken from asbestos- lined metal casting rings. Additional particles were removed from a wall * Material supplied with Ceramigold Investment, Whip-Mix Corp-, Louisville, KY 40217. -- --,, against which the bench was located, from the muffle of a furnace, from a casting machine and from a drawer in which a roll of ring-liner had been stored. The sanpling tapes were sealed to aluminum stubs. The debris-con taining side of each tape was coated with gold and palladium or carbon and examined with the use of a scanning electron microscope.+ Photomicro graphs of the collected matter were analyzed for determination of shape, size and distribution of particulate ccwponents. Elemental constituents of selected carbon coated particles were determined by energy-dispersive x-ray microanalysis.^ RESULTS A. Material collected from thumbs and index fingers: Scanning elec tron microscopic examination shewed aggregates of relatively straight, parallel fibers and single randomly dispersed fibers (Figure 1). The fibers, though fragmented, did not exhibit axial cleavage. Diameters of the linear particles ranged from 0.10 to 1.0 van. Generally, fiber length exceeded 200 ym. Morphological differences between the particles broken from unheated and heated strips of the test material were not detected. Dispersive x-ray analysis of selected particles revealed that magnesium and silicon were the predominant constituents of the test material. However, small amomts of iron were also detected as well as sulfur and calcium (Figure 2). Approximate elemental composition of the fiber was as follows; 45%, silicon 40%, sulfur 2%, calcium 2% and iron 4%. Heating at a conventional mold burnout temperature did not alter the elemental composition of the woven fibers. + Scanning Electron Microscope, model 1000, Advanced Metals Research Corporation, Burlington, MA 01803. # Energy Dispersive X-Ray Analyzer, model 707k, with EDIT II Software, EDAX International, PrairieView, XL 60009.2 2 Fibers were not detected in the particulate matter removed from the digits of washed hands. Occasional small spheroidal, and plate-like parti cles found in one sanple exhibited a broad range (titanium, silicon, chlorine, potassium, calcium and iron) of elemental constituents. B. Material collected from laboratory bench, storage drawer, wall. furnace and casting machine: Samples of debris removed from the laboratory bench and wall contained fragmented slender particles (Figure 3). Particles of similar configuration were recovered iron the casting machine and iron the storage drawer. Analysis revealed that these filamentous particles were com posed of magnesinn, silicon, sulfur, calcium and iron in the same relative concentration as found cm the finger tips. Particles detected within the muffle of the furnace were not fibrous (ration of length to diameter less than 3 to 1). Constituents of these particles included silioon, phosphorous, calcium and sulfur. DISCUSSION Asbestos is a term used to identify any one of several minerals which can be crushed into fibers. However, a particular mineral substance known as chrysolite is the principle source of commercial asbestos.11 Chrysolite is a hydrated silicate of magnesium, the approximate ccnposition of which is 37 to 44 percent silicon dioxide, 39 to 44 percent magnesium oxide, 12 to 15 percent water and 1 to 6 percent iron oxide. Analytical data suggest that the fibrous material examined in this study is chrysolite. Compositional features of the nonfibrous particles removed from the fingers of washed hands and from the furnace muffle infer the presence of debris from refractory investment materials. The occupational risk associated with asbestos exposure has been well documented.I2-16 In man, exposure to asbestos dust is associated with an in- 3 creased incidence of tuners of the lung1^ and with pleural and peritoneal mesothelioma. I** Asbestos fibers are subtle carcinogens that do not produce an obvious exposure-response relationship. Usually a long latency precedes the onset of fibrogenic or carcinogenic activity and the effects of repeated exposures over long periods of time are cumulative.19 The threshold limit value (TLV) below which asbestos would not affect adversely the health of man is not known. The current eight-hour time weighted TLV for asbestos is 2 fibers per cubic centimeter of air,20 however, this limit has not been evaluated with regard to its effectiveness in the preven tion of asbestos-induced disease. Additionally, the mechanisms by which fibrous materials produce malignant disease are uncertain. It has been shown, however, that the degree of carcinogenicity is related to fiber size rather than to ccnposition.21 Data from animal experiments have indicated that durable fibers less than 3 pm in diameter and more than 20 pm in length present the greatest hazard, and the fibers described in this report fall within this range of size. Since it has been shown that cigarette smoking increases the risk of Its cancer in asbestos workers, it should be discouraged especially within the working area.22 The actual risk incurred in the use of dust producing asbestos in dental laixsratories is unknown. However, the potential for inhalation or ingestion of asbestos particles by dental laboratory workers would appear to be greater than that of meabers of the general population (Figure 4). The need for rigorous standards of personal and laboratory hygiene in the handling of asbestos is obvious. Hand washing for example as shewn in tills study effectively removes the material from fingertips. In view of these results reported here ami In conformity with correct occupational health practices, the following protective measures are suggested in dental clinics: 4 1. Inform all office and laboratory personnel of the potential danger of asbestos. 2. Confine the storage and use of asbestos to a small area of the laboratory or to a snail isolated working chamber. 3. Isolate operatories and other offices from the dental laboratory. 4. Insure the wearing of face masks and surgical gloves when asbestos or asbestos-containing debris is handled. 5. Encourage cutting in lieu of tearing of asbestos. 6. Prevent smoking and eating in the dental laboratory. 7. Prevent the transmission of asbestos waste by sewage lines and air exhaust systems to preclude its discharge within the community environment. f SUMMARY ^Particles of debris emanating fran an asbestos containing dental labora tory material were characterized with the scanning electron microscope and x-ray microprobe. The dimensions and composition of these particles suggest their potential to behave as subtle carcinogens. With almost daily use of dust producing asbestos in the dental laboratory, the inpmper handling of this substance could be hazardous to the health of dental personnel. It is recommended that high standards of personal and laboratory hygiene be employed in the handling of asbestos. ,, RI 1. Travagliai, E.A.; Larato, D.C. ; and Martin, A. Dissemination of organism-bearing droplets by high-speed dental drills. J Prosthet Dent 16:132 Jan-Feb 1966. 2. Micik, R.E.; Miller, R.L. ; Mazzarella, M.A. ; and Ryge, G. Studies on dental procedures. J Dent Res 48:49 Jan-Feb 1969. 3. Battistone, G.C. ; Hefferren, J.J.; Miller, R.A. ; and Outright, D.E. Mercury: its relation to the dentist's health and dental practice charac teristics. JADA 92:1182 Jun 1976. 4. Mantyla, D.G. ; and Wright, O.D. Mercury toxicity in the dental offioe: a neglected problem. JADA 92:1189 Jun 1976. 5. Eames, W.B. ; Caspar, J.D. ; and Mohler, H.C. The mercury enigma in dentistry. JADA 92:1199 Jun 1976. 6. Linde, H.W. ; and Bruce, D.L. Occupational exposure of anesthetists to halothane, nitrous oxide and radiation. Anesthesiology 30:363 Apr 1969. 7. Johnson, E.G. Harmful pollution by anesthetic gases? Lancet 2:824 Get 1972. 8. Nikki, P. Are anesthetic gases harmful to operating room staff? Ann Clin Res 4:247 Oct 1972. 9. Burnett, G. Substitute for asbestos in casting rings. Br Dent J 141:171 Sept 1976. 10. Cornell on Dental Therapeutics and Council cn Dental Materials and Devices. Hazards of asbestos in dentistry. JADA 92:777 Apr 1976. 6 11. Berg, D. Inorganic insulating materials. In Standard Handbook for Electrical Engineers, ed 10. New York, McGray-Hill Book Co., 1968, p. 355. 12. Enterline, P.E. Type of asbestos and respiratory cancer in the asbestos industry. Arch Environ Health 27:312 Nov 1973. 13. Selikoff, I.J.l and Nicholson, W.J. Asbestos air pollution. Arch Environ Health 25:1 Jul 1972. 14. Weill, H. and others. Radiographic and physiologic patterns among workers engaged in manufacture of asbestos cement products. J Occupational Med 15:248 Mar 1973. 15. Doll, R. Mortality from lung cancer in asbestos workers. Br J Industr Med 12:81 Apr 1955. 16. Cordova, J.F.; Tesluk, H.; and Knudtson, K.P. Asbestosis and carcinoma of the lung. Cancer 15:1181 Nov-Dee 1962, 17. Huper, W.C. Occupational and nonoccupational exposure to asbestos. Ann NY Acad Sci 132:184 Dec 1965. 18. Stantcn, M.F.; and Wrench, C. Mechanisms of mesothelioma induction with asbestos and fibrous glass. J Natl Cancer Inst 48:797 Mar 1972. 19. Thomson, J.C. Asbestos and the urban dweller. Ann NY Acad Sci 132:196 Dec 1965. 20. Nicholson, W.J. Asbestos - the TLV approach. Ann NY Acad Sci 271:152 Dec 1976. 21. Stanton, M.F. Fiber carcinogenesis: is a&estos the only hazard? J Natl Cancer Inst 52:633 Mar 1974. 22. Berry, G. Combined effect of asbestos exposure and smoking on mortality from lung cancer in factory workers. lancet 2:476 Sep 1972. 7 LEGENDS FOR FIGURES Figure 1. Typical scanning electron photomicrographs of particulate matter removed from thurfos and index fingers of laboratory workers. (A) Aggregates from dry, unheated ring liner. Initial magnification was X50. (B) Aggregates from heated ring liner. Initial magnification was X50. (C) Particles of dry, unheated ring liner. Initial magnification was 35,000. (D) Particles of heated ring liner. Initial magni fication was 35,000. Figure 2. Dispersive x-ray analysis of a single fiber oooponent of an asbestos casting ring liner. Figure 3. Topical scanning electron photomicrographs of debris from laboratory bench top and laboratory wall. (A) Full-field of bench top debris. Initial magnification was 350. (B) Full-field of wall debris. Initial magnification was X50. (C) Linear component of bench top debris. Initial magnification was 35,000. (D) Bundle of linear ccnponents of wall debris. Initial magnification was 35,000. ft Figure5*4. Fragmented debris from laboratory asbestos in storage drawer. 8 *