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FILE NAME: National Safety Council (NSC) DATE: 1975 DOC#: NSC504 DOCUMENT DESCRIPTION: NSC Safety News - Microscopical Identification of Target Health Hazards NATIONAL SAFETY COUNCIL A NON-GOVERNMENTAL, NON-PROFIT, PUBLIC SERVICE ORGANIZATION Headquarters Office: 4 2 5 N. Michigan Ave. Chicago, IL 60611 Trustees' Fund Office: 8 5 6 Lincoln Bldg. 6 0 E. 42nd St. New York, NY 10017 CHAIRMAN, BOARD OF DIRECTORS DR. DEWEY F. BARICH, President Detroit Institute of Technology, Detroit, Ml 48201 PRESIDENT VINCENT LT O FA N Y , National Safety Council VICE-PRESIDENT FOR INDUSTRY MICHAEL F. BIANCARDI, Assistant Vice-President Employers Insurance of Wausau, Wausau, Wl 54401 ACTING EXECUTIVE VICE-PRESIDENT FRED POTENZA, National Safety Council SECRETARY AND TREASURER H. W. CHAMPL1N, National Safety Council PRESIDENT EMERITUS HOWARD PYLE, National Safety Council A NATIONAL SAFETY COUNCIL PUBLICATION AUGUST 1975 VOLUME 112, NUMBER 2 5 5 ,0 0 0 copies of thfejssue were printed m m m c, 1u- 62 64 67 72 80 81 84 93 96 98 100 106 Public Hearings on Proposed Noise Standard Programming Persona! Protection-- To Hear or Not To Hear (It's That Simple) Noise Control . . . Diesei Compressors industrial Hygiene Instrumentation-- Vinyl Chloride Monomer OSHA Issues Guidelines fo r Vinyl' Chloride Inspections Vinyl Chloride-- Monitoring Exposures Microscopical Identification of Target Health Hazards Bulk First Aid Kits (Data Sheet 651) Specialized Safety Manual NSC Proclaims . . . With Safety For All NSC Safety Training Institute Schedule for the Bicentennial Emphasis on: Occupational Health and Protection Before Compliance Future Article Preview Officially OSHA Voice of the Reader Safetybriefs Coming Events In Focus CRISP Standards Product Safety Memo With Safety For All Congress Registration OSHA-Gram Ideas That Worked O ff the Job Sa'fetyclips Safety Literature Keeping Posted Change o f Address Card Wire from Washington Safety Library Newscope Obituary Personnel Directory New Safety Equipment OSHCO Reprints Advertisers' Index Reader Service Card 4 6 8 16 28 36 42 48 52 56 57 59 86 88 91 108 111 115 150 170 178 182 183 184 186 193 196 198 A model of the human ear, used at Northwestern University's Diagnostic Center for Hearing Impaired, was photographed partially assembled by James B. Lehman, NSC staff photographer. It calls attention to " Hearing Protection"-- what the recent federal hearings on the proposed noise standard were all about. (See page 62.) .4 Lf ilT nr >Y //A fct, C editor associate editors contributing editors data sheet technical director editprial director publications manager art director photographer advertising manager production manager reader card inquiries ROY FISHER JAMES W. LAHEY SUSAN M. SHEMERDIAK EDWARD D, DIONNE DOROTHEA GUTHRIE RUTH HAMMERSMITH TOM HIRSH CHARLES PRICE HARRY N. ROSENFIELD ROBERT WATERBURY fr a n k e . Mcelroy JAMES WEGING ROBERT BELKNAP ROBERT L, M EYER JACK HORNER FRANK WASZAK JAMES B. LEHMAN JOHN C. LUNDGREN PATRICIA MAZZUCCA VICKI BACSKAt STATEMENTS AND OPINIONS advanced In articles and advertisements ere personal expressions of the authors and advertisers, and they are not necessarily those of the National Safety C ouncil. , . unless they are presented as policy statements and are so-stated. INFORMATION AND RECOMMENDATIONS contained In this publication have been compiled from sources believed to'be reliable and to be representative of the best current opinion on the subject No warranty, guarantee, nor representation is made by the National Safety Council as to the absolute correctness or sufficiency of atiy representation contained In this and other Council publications, and the National Safety Council assumes no responsibility In connection therewith. Likewise, It can not be assumed that all acceptable safety measures are contained in this and in other Council publica tions, nor th a t other oc. additional measures may not be required under particular or exceptional conditions or circumstances. NATIONAL SAFETY NEWS ts published monthly by the National Safety Council, and It Is printed In the U.SJL Copyright 1975 by the National Safety Council. 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Michigan Ave., Chicago, IL 60611 2 August 1975, NATIONAL SAFETY NEWS M icroscopical Identification O f Target Health Hazards 75 3848 Through sophisticated techniques arid instruments, scientists can readily identify asbestos, lead, silica, cotton dust and other air-borne particulates in the workplace. I n d u s t r ia l h y g ie n e is concerned with the s t u d y of hazards to the health of the industrial worker. Some of these hazards are tiny particles in the air we breathe. They are hard to trap and identify, and difficult to associate directly with the failure of health because many years may elapse after exposure before adverse effects occur. In any case, we know we have problems. Focusing upon the need to create healthful working condi tions, OSHA, in January, 1972, initiated the'T arget Health-Hazards Program. The emphasis is on five hazardous workplace substances: asbestos, lead, silica, cotton, dust, arid carbon monoxide. Asbestosis resulting from pro longed inhalation of respirable air borne asbestos dust may appear 20, 30, or 40 years after the exposure. Other particulate hazards are cot ton dust, lead compounds, and quartz. Unfortunately, air-borne particles of these materials are so ubiquitous that everyone from fac tory workers to housewives and school children is exposed to some extent. Exposure to particulate lead compounds is common due to the us& of tetraethyl lead in gasoline and in paint. Asbestos is used in filters, in sulation, fire-retardant textiles, and brake linings. Abrasion of these materials produces particles that find their way into the atmosphere. Quartz,- one form of which is silica, is the most common mineral on earth and few air samples are free of small particles of the type that may eventually 'cause silicosis. Cotton dust, though less of a hazard than the others, is still a potent danger to industrial workers exposed for long periods of time to high cotton dust concentrations. The exposure time to quartz and asbestos particles must be long term, and the dosage high before serious .impairment occurs, Our lungs also have a reasonably good flushing mechanism that helps to remove the billions of particles that settle every day on those surfaces. Perhaps this capacity for cleansing the lungs must be overwhelmed for some minimal time before perma nent serious damage is done. Many varieties of technical back grounds must be involved before the solutions are found. The microscopist has one important role-- By Walter C ., McCrone, D. Sc., Scientific Advisor, Walter C. McCrone Associates, Inc., Chicago. among others--monitoring dust and other samples for the presence and amount of the hazardous sub stances. He is able to do this be cause the microscope magnifies each particle to a size such that selective Figure 1 shows quartz (silica) particles magnified 125 times with crossed polars. B Figure 2 represents cotton fibers as they appear with crossed polars at 200 times magnification. Figure 3 shows chrysotile fibers (one form of asbestos) at 100 times magni fication. Angust 1975, NATIONAL SAFETY NEWS with a finely focused pencil of electrons. Each time the beam strikes a tiny particle X-rays are created and emitted. If these X-rays show the proper wavelength for lead the computer stops the,,, scanning sequence until 'that leader containing speck can be analyzed completely and quantitatively. This 'requires less than one minute for each particle. The scanning then proceeds to the next lead particle. Figure 4 shows electron microprobe onolyzer used at McCrune Associates, Figura 5 shows the AEi EMMA 4 electron microscope/electron probe analyser. In one two-week period of continu ous operation the probe found and analyzed over 12,000 individual lead particles. The problem presented by water and specific physical measurements widely varying composition and borne samples is one of decreased can be made to identify that properties. Even here, however, particle sizes; most large particles particle. By selecting the proper the microscopist is able to vary will have settled out. Particles microscope and utilizing Ms back his procedure so that fibers ob smaller than about a few tenths of ground in crystallography the micro- served microscopically can be a micrometer (10 millionths of an scopist can identify many particu further identified as chrysotile, anti- inch, for example) cannot usually late substances at sight. These in gorite, anthophyilite, tremofite, be identified by the methods de i clude most of the air-borne particles amosite, or crocidolite. Each has scribed. The microscopist can, detrimental, to our health-- quartz, unique optical properties observed however, identify these small par-, cotton fiber dust, and asbestos. Lead as optical staining colors when tides by electron microscopy and its I; is a special problem because there properly.mounted for examination. auxiliary techniques'. The most are' many different lead compounds. Figure 3 shows one of four different sophisticated of these tools is the Carbon monoxide is not detect asbestifoim minerals, chrysotile. A.E.I. Scientific Apparatus Ltd. able by microscopy. Refer to the Again, individual small fibers can be EMMA (Electron Microscope October 1973 N a t io n a l Sa f e t y identified even when present as MicroAnalyser) (See Figure 5) It N e w s article "Target Health Haz trace quantities in a complex mix is a combined electron microscope ard--Carbon Monoxide," for in ture. and microprobe anaylzer. The formation regarding CO and the Finally, we should consider lead identification of asbestos in water various means of detecting it. compounds. As suggested, these supplies is a good example of the First, consider the problem of present problems because they are application of an EMMA, A sam identifying quartz microscopically. not a specific compound as is, ple of water is filtered through the The shape and optical properties quartz, nor even a small group of finest membrane filter. A few square make this easy. Figure 1 shows slightly different compounds like millimeters of the filter are cut out ? V ' quartz between two slightly un asbestos. There is, however, one and placed on a carbon-coated crossed polarizing filters; the low simple procedure that identifies electron microscope grid. The birefringence (low numerical differ all lead-containing particles as filter itself is dissolved in a solvent ence between the maximum and such, though it does not specifically vapor system, and the particles are minimum refractive indices) and identify the compound. The dust is left supported on the thin carbon ! conchoidal (shell-like) fracture are dispersed (allowed to settle due to film. The grid is then placed in the I ] obvious. To confirm his initial gravity) on a reagent-impregnated, EMMA and scanned visually at t identification of quartz the micro- gelatin-coated microscope slide. The about 20,000 times -for fibers, ,scopisi has an optical staining pro cedure (called dispersion staining) reagent--sodium chromate, for ex ample-- reacts with lead to form a Each suspected asbestos fiber is then analyzed chemically in situ that causes all quartz particles to colored halo around each particle by the microprobe and by selected appear blue or blue magenta. The containing lead. One then simply area electron diffraction (identifica latter procedure is excellent for de counts the'halos microscopically to tion of elements from the wave tecting traces of very fine quartz determine the number of lead lengths of their electrons). This 5"' in dust samples. particles. determines its crystal structure to Next, consider cotton fibers. Another procedure has been confirm asbestos and identify pre These, too, have characteristic used to identify the lead compounds cisely the mineral type. optical properties and shape, and in auto exhaust. The particles Microscopy is a sophisticated can be identified just as dependably spread over the surface of a highly technique for analyzing particles as quartz (see Figure 2). polished beryllium plate were ex hazardous to health. A well-trained Asbestos presents a somewhat amined by an electron microprobe microscopist with the necessary more complicated problem because analyzer as shown in Figure 4, This equipment can quickly and posi asbestos is not a single substance, instrument, com puter-controlled, tively identify and characterize but a class of fibrous minerals of systematically scans the particles suspect particles.-- End. August 1375, HATIONAL SAFETY HEWS PR