Document NrrbLGoRMYL9BjO666JvwR8p

Johns-Manville RESEARCH & ENGINEERING CENTER P. O. BOX 159 MANVIllE, N. J. C8835 TELEPHONE: 722-9000 AREA CODE 201 iisi June 18, 1970 Mr. J. E. Stonis Manager, Market Research 4 Sales Development The C. P. Hall Company of Illinois 7300 S. Central Avenue Chicago, Illinois 60638 . Dear Mr. Stonis: Don Partridge has referred your letter of May 28, 1970 to me for reply. It has long bean recognized that asbestos fiber. Inhaled In large quantities over a long period of time, can be hazardous to health. Protection against this hazard can be achieved by maintaining the asbestos fiber dust concentrations In the workplace below the established Threshold Limit Value. Threshold Limit Values refer to airborne concentrations of substances and represent conditions under which it ts believed that nearly all workers may be repeatedly exposed, day after day, without adverse effect. TLV's are set by the American Conference of Governmental Industrial Hygienists, assisted by the Bureau of Occupational Safety and Health of the Department of Health, Education and Welfare. The presently proposed TLV for asbestos fiber dust Is 5 fibers over 5 microns in length, per mi l 111 Iter of alr. Maintenance of the dust concentrations below the Threshold Limit requires processes and handling methods that do not generate excessive dust, or, If they do, that properly designed mechanical dust control systems be provided. Good housekeeping practices are also essential in maintaining proper dust levels. If dust concentrations cannot be maintained below the TLV, then exposed workers should wear respirators approved by the U.S. Bureau of Mines for protection against hazardous dusts. The latest Bureau of Miners approval schedule for such respirators Is 21--B. For your further Information'on the general subject of asbestos and health, I enclose the following papers that have been prepared by Johns-Manville: "Asbestos and Human Health" . "Asbestos and the General Public" "Asbestos--A Family of Minerals". Mr. J. E. S+onls -2- June 18, 1970 I also enclose a pamphlet prepared by the National Insulation Manufacturers Association on recommended health safety practices for handling and applying thermal insulation products containing asbestos. I am sure that some of the suggestions in this pamphlet would be applicable to your operations. As you are undoubtedly well aware, there are in daily use throughout industry many materia Is"that are potentially hazardous and toxic. Methods and techniques are available by which these materials, including asbestos fiber, may be handled safely. Please contact me directly if you have additional questions. Very truly yours EMF/ems Enc. (4) Edmund M. Fenner, Director Environmental Control ASBESTOS AND HUMAN HEALTH INTRODUCTION Asbestos, known since antiquity, has wide-spread and important applications in our modern industrial society. With the 20th century burgeoning of the uses of asbestos has come recognition of the need to cope with occupational hazards assoc iated with excessive inhalation of asbestos dust. This statement summarizes the essential uses of asbestos, the know facts about health problems associated with occupational exposure to asbestos dust, and the research being conducted to identify and reduce these health risks. AN ESSENTIAL PRODUCT Asbestos has many essential functions in construction, in industry and in transportation.. Over the years fireproof asbestos has saved thousands of lives and much valuable property. For safety, fire prevention and other reasons, products containing asbestos are used in schools, houses, theaters, ships, office and other public buildings, furnaces, boilers and firefighting equipment. Th'e brakes on automobiles, trucks, buses and trains are dependable because asbestos is a major component of brake linings. WHAT IS ASBESTOS? Asbestos (from the Greek "unquenched1*) is the name given a family of mineral fibers comprised of three major types -----chrvsotile. crocidolite and amosite ----- each of which differs from the other; physically and chemically. Studies of the relationship between asbestos and health are complicated by this diversity. Chrvsotile is a white magnesium silicate, can be attacked by acids, has a positive electrical charge, is flexible and not easily pulverized. Crocidolite is a blue ferrous sodium silicate, is acid-resistant, has a negative electrical charge, and is le33 flexible than chrysotile. Amosite is a ferrous magnesium silicate with a negative electrical charge, is brittle and easily pulverized. - more - Jf - t- KNOWN AND SUSPECTED OCCUPATIONAL RISKS /`nr workers who handle* asbestos fibers m mines, mills, factories, and some building and insulation trades, the industry shares with doctors, public health officials and others involved in industrial medicine a concern about possible health effects from excessive on-the-job exposure to asbestos dust. ASBESTOS IS-: The industry long ago recognized the risk of a particular lung disease called asbestosis among some workers and tooksteps to safeguard employees. This non-malignant disease is brought on after inhalation of excessive concentrations of asbestos dust over a period of many.years. Asbestosis is one of the lunq diseases.called pneumoconioses. Others are silicosis, from silica (stone) dust; talcosis from talc; anthracosis, from coal dust. These are considered industrial health risks against which the various industries have instituted protective measures. For years, the asbestos industry has taken protective measures to roduce excessive exposures to asbestos dust and the risk of asbestosis among its workers. BRONCHOGENIC (Lung) CANCER: The industry is aware of some medical studies that have reported 'an association between excess ive exposure to asbestos dust and an increased risk of a certain type of lung cancer (bronchogenic). Even though the number of these cases among asbestos industry workers is only a small fraction of the total employed, the industry considers the problem a serious one. It has become the subject of considerable scienti fic research through statistical, clinical and pathological studies of exposed workers; through experimental studies with laboratory animals; and through studies of the physical and chemical nature of asbestos and associated minerals. Recent studies have suggested that the trace metal3 often found with asbestos dust (nickel, cobalt and chrome) should be examined more closely. In 1967, results of a study of deaths occurring among a group of insulation workers indicated that occupational exposure to asbestos greatly increased the risk of lung cancer but only among cigarette smokers. Although the number of deaths involved was small, the study showed no cases of lung cancer among insulation workers who were non-smokers. MESOTHELIOMA: Also under study is a rare disease called mesothelioma, a tumor of the che3t and abdominal cavity which is different from bronchogenic lung cancer. Recently, investigators have associated a frequency of cases of mesothelioma with exposure to asbestos in certain geographic locations. This was originally more - for research of such organizations as: The Industrial Hygiene Founcl.it urn ol America, The Ashostosis Research Council (Imu.lquartered in Great Britain). The Institute of Occupational and Environmental Health in Montreal, The Environmental Health Center at Mt. Sinai Hospital and others. Johns-Manville also conducts studies on technical aspects of asbestos in its own Research and Engineering Center at Manville, New Jersey. Among the subjects scientists are now exploring are: the specific identification and health significance of fiber-like (ferruginous) bodies found in lung tissues; the health of asbestos mining,-processing and fabricating workers compared with the general population; the relationship between cigarette smoking and cancer among asbestos insulation workers; the accurate identifica tion of particles found in the air over `a major industrial city; and the development and evaluation of the most'effective indus trial hygiene practices for use in the asbestos industry. In cooperation and in conjunction with other agencies, the asbestos industry will continue to seek now information about the biological effects of asbestos fiber and to develop ways of assuring maximum possible protection from occupational hazards, for its employees in asbestos mines, mills and plants and among fabricators and applicators of this essential material. ## ## January 15. 1968 September 16, 1968 ASBESTOS AND THE GENERAL PUBLIC People of virtually every nation in the world benefit from the many uaea of the mineral, aabeatoa. Asbestos helps to "build safety and durability into schools, houses, ships, aircraft and public buildings. With the increasing use of this mineral fiber, the question has been raised as to whether asbestos, especially when suspended in city air, poses any health risk to the general public. The same question is being asked about many other materials in general use in our modern society. Medical and scientific research is being conducted to find answers. For asbestos, some of the answers are already in. To the extent that any asbestos fibers are in the general air -- and there are literally hundreds of different animal, vegetable and mineral fibers in the dust of the air -- there is nothing to show that these are a health hazard for the public. To see why this is so requires understanding of how and why asbestos is used, of some of the scientific research that has been conducted, and of the meaning of this research with regard specifically to those with occupational exposures in contrast to the general public. (More) A MODERN USES GROW OUT OF ANCIENT KWnWT.gnrtE 2. The word asbestoB is from the Greek; it means "unquenched" or "incombustible." The peculiar properties of asbestos have fascinated people ever since the mineral was discovered more than 4,500 years ago. Although in the raw state it is as dense and compact as the rock which encases it, asbestos can be separated into light, silky fibers. These fibers have many uses. They can be woven into non-combustible fabrics for such things as fire curtains for theaters or protective garments for firefighters. They can be added to other materials to produce floor and ceiling tile, roofing shingles, siding, asbestos-cement pipe and many other useful products The earliest known use of asbestos goes back 45 centuries. Objects unearthed by archeologists in Finland indicate that it was used to hold together pieces of pottery before the clay was baked. According to legend, the Emperor Charlemagne owned a "magic" asbestos table cloth which his stewards cleaned after royal banquets by throwing it into a fire, then retrieving it intact. Marco Polo found asbestos cloth on his journey to Asia and was told that it was woven from a salamander skin, but he later learned its true origin. (More) MINERAL PROVIDES SAFETY AND DURABILITY 3. In the twentieth century, aabeatoa has become an increasingly essential material of an improved way of life and an expanding industrial economy. Asbestos has many vital functions in constructs transportation and industrial processes. It provides built-in protection against fire and deterioration in scores of common products in daily use. Through the years it has saved countless lives and billions of dollars in property damage by preventing or checking the spread of fires. Electrical installations are safer because of asbestos insulation. When used as packings and gaskets, asbestos promotes the efficient operation of industrial machines and pumps. . In transportation, the brakes on vehicles -- cars, trucks, buses and trains --' are dependable because asbestos is a chief component in brake linings. OCCUPATIONAL RISKS AND STEPS TO PROTECT WORKERS To meet the increasing demand for this invaluable fiber, a worldwide asbestos mining and processing industry came into being. A3 in many other mineral and materials industries, the need developed to protect employees against occupational health hazards. (More) 4 t It was found that some workers exposed to excessive asbestos dust over a period of years developed a non-malignant lung disease called "asbestosis." As with many similar conditions, asbestosis is dose-and-time related -- that is, it develops only after inhalation of excessive concentrations of asbestos dust over a period that averages 17 years. Some medical studies have reported an association between the disease "asbestosis" and an increased risk of a certain type of lung cancer (bronchogenic). Even though the number of lung cancer cases among workers heavily exposed to asbestos fiber is only a small fraction of the total employed, the industry considers the problem serious. It is the subject of considerable Scientific research through statistical, clinical and pathological studies of exposed workers; through experimental studies with laboratory animals, and through studies of the physical and chemical nature of asbestos and associated minerals. In the recent past, the asbestos industry has invested millions of dollars in equipment and techniques to prevent the inhalation of asbestos dust by workers in the mining and milling of asbestos and in the manufacture of asbestos-containing products. A program of education and training is conducted for asbestos fabricators and applicators to provide them with a thorough under standing of potential risks and' to encourage general adherence to sound industrial hygiane practices. (M< 5. Studies in asbest03-using industries in England and the United States indicate that where dust control measures have been taken, the risk of lung diseases among the workers has been greatly reduced. NO RISKS TO GENERAL PUBLIC SHOWN IN STUDIES Because of the occupational health hazards associated with asbestos, some people who are concerned about general air pollution have raised the question of whether there is asbestos dust in the air in sufficient quantities to constitute a health risk to the general public. Studies of asbestos exposure and human health of the general public have produced no evidence of any health hazard to the general public from the use of finished asbestos products. "Asbestosis" does not occur among the general population; it occurs only among those with long-time,heavy occupational exposures. There is no evidence that anyone has ever contracted any disease from exposure to the wearing or weathering of brake linings, floor tile, roofing, or other products containing asbestos. Brake linings in particular were the subject of a 1968 United States Public Health Service report. Jeremiah Lynch of the National Center for Urban and Industrial Health, U. S.Public Health Service, conducted the tests. He concluded that any asbestos that might come from brake lining wear was "an inconsequential health (Mo 4* 6. factor in urban air pollution." The study provided scientific evidence refuting much recent unsupported speculation that the wear of brake linings might be releasing many asbestos fibers into the air: "Except in all but the most extreme driving conditions, only a very small fraction of the 30 to 50* asbestos present in a brake lining escapes into the atmosphere as free fiber ... the remainder is converted into some other mineral as a result of the extreme temperatures generated at small spots on the lining surface. Thus, although urban air contains a few free fibers as a result of brake lining wear, they represent a very small pro portion of the total asbestos used in the manufacture of brakes. Many sources of respirable fibers not associated with asbestos products have been identified, and the free fibers from brake lining wear appear to be an inconsequential health factor in urban air pollution." Other medical and scientific reports show that the' occupational health risks from asbestos dust exposure do not extend to the public. In 1967 Drs. P. E. Enter line and M. A. Kendrick reported on the reduction of asbestosis among workers in asbestos fabricat- - in industries where protective measures have been taken. They pointed out that the small amount of asbestos to tfiich people in general may be exposed is of "little importance:" "..................... if very low-level exposures of populations to asbestos dust play any part in the pathogenesis (development) of disease it must be very small indeed .... Asbestos dust at levels to which general populations are exposed probably is of little importance in the etiology (caustion) of disease." (More) 7. SO-CALLED "ASBESTOS BODIES" NOT RELATED TO DISEASE In the mid-1960's the question of public exposure was discussed in studies that reported finding so-called "asbestos bodies" in the autopsied lungs of some city dwellers whowere not known to have been exposed directly to asbestos dust. The studies emphasized that these so-called "asbestos bodies" had no relation with either the cause of death or with any history or symptoms of pulmonary disease. The authors of one such study, Drs. J. G. Thomson and W. M. Graves, noted that it would have taken a tremendous increase in the number of "asbestos bodies" found in the autopsied lungs to constitute even a "minimal" case of asbestosi3. They said in their 1966 report: "It should be stressed that in spite of frequent asbestos bodies in the lung bases none of this group had pulmonary disability and all died from other causes .... to convert the scanty or very scanty bodies which we have demonstrated to be present in so many urban dwellers to the frequency present in a minimal basal asbestosis would require an increase by hundredfolds and to get a more diffuse classical asbestosis with pulmonary disability the multiplying factor might well be in many millions." In a similar study the same year, Drs. L. Anjilvel and W. M. Thurlbeck noted that there is no risk of cancer to the general population from asbestos exposure. These researchers said: "In our series there seemed to be no particular association between malignancy and the presence of asbestos bodies ... asbestos bodies are not more common in patients with malignant disease in the autopsy populations we have ( Jf 8. studied, and thus casual exposure to asbestos is not an important cause of malignancy in the general population." Other authors have raised the question of the real identity of these so-called "asbestos bodies." The term has for years been applied loosely to describe a tiny body of tissue in the lung containing a core of some inhaled particle -- asbestos, talc, man-made fiber, or certain other common substances. The name "asbestos body" is misleading if the core substance has not been positively identified. Thus, it is not necessarily so that the finding of such "bodies" in city dwellers' lungs means that these people inhaled asbestos. Because the cores of such "bodies" do not always contain asbestos, and because the over-growth tissue contains some identifiable iron. Dr. Paul Gross, who has studied the problem extensively, has suggested that a more accurate name would be "ferruginous (iron-like) bodies." Other specialists have now begun * to refer to "ferruginous bodies" in their papers. Dr. J. M. G. Davis, in 1967, deplored the "current furor over asbestos bodies --- which recently appeared in the professional literature and wa3 widely reported in the new3 media with varying degrees of sensationalism." He commented specifically: ".............. the basic assumption that asbestos-like bodies can only be produced from asbestos has proved incorrect and this cast3 considerable doubt on the theory that ha3 been the chief basis of the asbestos 'scare'." (More * 9. MANY THINGS BESIDES ASBESTOS MAY CAUSE FIBROUS ''BODIES1' Much research work is going on to develop ways of identifying the particles that may be the core of these "bodies." It has been shown that a number of substances can cause "bodies"in both humans and experimental animals. L. J. Cralley and associates in the U. S. Public Health Service have discussed the great number of substances which might produce "bodies"`in human lungs. Publishing in 1968, they said: "On the premise that the fibrous bodies observed in the lungs of persons at autopsy are all "a3be3tos bodies" and that coated fibrous bodies are a specific reaction to asbestos fibers, sone investigators have concluded that asbestos fibers are significant air contaminants ... Respirable fibers may be mineral, vegetable or animal in origin and may come from both natural and synthetic sources. There are well over a hundred different natural minerals with some degree of fibrous structure .... Respirable fibers of vegetable orgin may be from both live and dead plant tissues .... Animal fibrous materials include animal hair and scale, insect hair ... Synthetic fibers include the newer ceramic fibers ... as well as a wide range of established and emerg ing organic types used in textiles, fillers, containers, filaments, structural materials, etc." Whatever their origin, the "bodies" that have been reported have not been connected with any disease, or with the cause of death, in the subjects studied. Even if some asbestos is among the variety of fibers in the air breathed by the public there is no evidence that it has any health significance. SUMMARY People throughout the world benefit from the many U3es of (Me *W I asbestos -- in schools, houses, theaters, ships, aircraft, offices and other public buildings, furnancea, boilers, firefighting equipment and in a myriad of everyday products. With the 20th century growth in the use of asbestos has come recognition of the need to cope with occupational hazards associated with excessive inhalation of asbestos dust. Much progress has been and is being made in protecting workers who handle asbestos fibers in mines, mills, factories and in some building and insulation trades. Medical scientists studying the occupational health hazards of asbestos see no evidence that asbestos poses any risk to the general public. Asbestos dust is not present in the general air in amounts of any significance to human health. PERSPECTIVE It is important to view in its proper perspective the expressed concern of some people that asbestos in the ambient air is a health risk to the general public. Asbestos is by no means alone in having the finger pointed toward it as a possible health hazard. Literally hundreds of substances -- as common and everyday as fuel oil.charcoal broiled steaks, iron rust and egg yolks -- are known or suspected of being cancer causing agents under certain experimental conditions. (Mo1"*' J* The point is that nearly everything we use and create in our increasingly complex society has been suspected, by someone, of being a potential hazard. To forego the many benefits' of these products of modern technology -- simply on the basis of suspicions that are un supported by medical evidence, would be a great and unwarranted disservice to the American public. # ### REFERENCES Anjilvel, L. and Thurlbeck, W.M., "The Incidence of Asbestos Bodies in the Lungs at Random Necropsies in Montreal" -- CANADIAN MEDICAL ASSOCIATION JOURNAL, December 3, 1966. Cralley, L. J., Keenan, R. G., Lynch, J. R., and Lainhart, W. s., "Sources and Identification of Respirable Fibers." AMERICAN INDUSTRIAL HYGIENE JOURNAL, March/April, 1968. Davis, J.M.G., "Asbestos Bodies and Bioeffects -- A Detective Story" presented at the meeting of the Industrial Hygiene Foundation, Pittsburgh, Pa., October 1967. Enterline, P. E.,and Kendrick, M. A., "Asbestos Dust Exposures at Various Levels and Mortality" - ARCHIVES OF ENVIRONMENTAL HEALTH, August 1967. Gross, P., Cralley, L.J.,and do Treville, R.T.P., "Asbestos Bodies: Their Nonspecificity." AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL, November/December, 1967. Lynch, J., "Brake Lining Decomposition Products." Meeting American Conference of Governmental Industrial Hygienists,- St. Louis, May, 1968. Thomson, J.G., and Graves, W.M., "Asbestos as an Urban Air Contaminant." ARCHIVES OF PATHOLOGY, May 1966. ## July 1, 1968 ASBESTOS------A FAMILY OF MINERALS SUMMARY; This paper sets forth some of the reasons why the term "asbestos" should not be used loosely in discussing medical questions. There is no single mineral known as asbestos. "Asbestos" is a name given to a family of minerals. It includes two major groups, containing a total of six varieties of asbestos. Each of these six differs from the others, physically, chemically and inbiological effect. Any study of the effects of asbestos is complicated by this diversity. Studies of both people and animals show differing types of reaction to the various types of- asbestos. Animal studies of excessive exposure indicate that of the three major commercial types of asbestos, commonly used chrysotile is least likely to produce a reaction. Because different varieties of asbestos produce different reactions, scientists are working on better methods for identifying the types of asbestos involved in their studies on human health. Other complications arise be cause trace amounts of mineral impurities are often found in samples of raw asbestos ore and refined fiber. VARIOUS TYPES OP ASBESTOS Any attempt to assess the effect of asbestos on health is complicated by the fact that asbestos is not a single chemical or physical entity. "Asbestos" is a generic name given to a group of hydrated silicate minerals that have one common attribute, namely, the ability to be separated into relatively 30ft, silky fibers. The known varieties of these minerals can be divided into two main classes on the basis of their crystal structures: serpentine asbestos and amphibole asbestos. The lone member of the serpentine class is chrysotile asbestos, which is by far the most common of the asbestos minerals. About 95 per cent of the asbestos used in this country is chrysotile,principally from mines in Canada. There are five recognized varieties of amphibole asbestos: crocidolite, amosite, anthophyllite, tremolite and actionolite. Of the amphiboles, crocidolite and amosite have the greatest commercial significance, although the use of anthophyllite is increasing. Each of the six types of asbestos differs from the others, chemically and physically. To add to the complexity, the chrysotile from one Canadian mine, for example, will differ in chemical impurities and in physical properties from the chrysotile from A CHARACTERISTICS OF THREE MAJOR TYPES 2. Each of the three types of asbestos that are most important commercially - - chrysotile, crocidolite and amosite - exhibits distinguishing characteristics. CHRYSOTILE - By far the leading producers are Canada and the Soviet Union. Smaller deposits are found in South Africa, Rhodesia, China, the United States and Italy. Chrysotile is a white serpentine asbestos and occurs in areas where serpentine rock was cracked by earth movement long ago and subjected to intense pressure and volcanic waters. This transformed some of the granular serpentine into fibrous chrysotile. Chemically, chrysotile is hydrous magnesium silicate with a magnesium hydroxide surface, it has a positive electrical charge. It can.be attacked by acids. It is a flexible fiber and does not pulverize readily. Commercial fibers contain small and varying amounts of iron and calcium compounds, depending upon origin. CROCIDOLITE - The bulk of the world's supply comes from South Africa. There are also small deposits in Australia, but they are no longer being mined commercially. It is an amphibole asbestos occurring in iron-rich sedimentary rock. Chemically, crocidolite i3 a ferrous sodium silicate with a silica surface. It has a negative electrical charge. 0039 It is acid-resistant. It is characterized by a deep blue color. Crocidolite is less flexible than chrysotile. AMOSITE - The Transvall district of South Africa is the only place where araosite is mined commercially. It is a member of the amphibole asbestos family, occurs in the same type of rock as does crocidolite, and ha3 the same negative electrical charge, but is brown in color. Chemically, amosite is a ferrous magnesium silicate with a silica surface. It is also acid-resistant, but less 30 than crocidolite. It is brittle and pulverizes easily. The major characteristics of these' three types of asbestos are summarized in a table attached to this paper. Because of the basic chemical and physical differences between chrysotile, crocidolite and amosite, it would be expected that overexposure to the three varieties would show varying biological effects. Scientific observation confirms this expect ation. There seems to be broad agreement that chrysotile, the type of asbestos moat heavily used in the United States, is least likely to produce a3bestosis, a non-malignant lung disease brought on after inhalation of excessive concentrations of asbestos dust over a period of many years. ANIMAL EXPERIMENTS SHOW DIFFERENT EFFECTS 4. Dr. J. C.Wagner experimented with all three types of asbestos on various laboratory animals, and found that crocidolite produced the most severe asbestosis and that amosite was more than five times as likely to produce a reaction as chrysotile. He reported, in 1963: "With chrysotile dust is was possible to produce severe lesions in the lungs of guinea-pigs, slight fibrosis in monkeys, while no significant effect was observed in two rabbits. Amosite dust causes marked asbe3tosis in all three kinds of animals. Lesions occur more rapidly in guinea-pigs exposed to this dust than in those exposed to chrysotile. There is an indication that the disease is progressive in monkeys and rabbits. Similar pathology to that which occurred in a monkey exposed to chrysotile for 22 months was observed in a monkey exposed to amosite for four months. The impure crocidolite dust caused severe disease in guinea-pig3, and the rate of respiratory infec tion among animals exposed to this dust was more marked than with the other types. It is possible that this may be due to the high quartz content of the dust. "Finally, asbestos bodies could be demonstrated in the lungs of animals exposed to all three types of asbestos dust. These were scanty in the animals exposed to chrysotile and usually segmented. Only occasional fibers were observed. In contrast to this, the asbestos bodies in the animals that were dusted with amosite were plentiful, and segmentation was rare: fibres were extremely numerous and far outnumbered the bodies." Following further investigation. Dr.Wagner offered an explanation for this observation at a medical symposium in 1965: Mora ... A 5. "A method of producing asbestos dust clouds has been devised and an animal inhalation experiment carried out to test it .... The elimination rate of Rhodesian chrysotile has been found to be three times greater than that of the amosite and crocidolite, which suggests an explanation for the previously observed reduced fibrogenicity of this dust. The reason for the difference in the elimination rate remains to be determined." COMMERCIAL ASBESTOS CONTAINS OTHER MATERIALS Asbestos ore and refined asbestos fiber contain mineral impurities, trace elements, and trace quantitites of organics, which vary from type to type and from mine to mine. In transit the ore may pick up additional trace organic impurities. ^ These trace materials are also the subjects of medical study to see if they may have a role in any of the health effects observed in animals. Trace impurities of nickel, chromium and manganese for example, were found by Dr. L. J. Cralley and associates in samples of chrysotile used in the asbestos textile industry. Other impurities in commercial asbestos fiber include iron, aluminum, calcium, sodium and potassium. WORLD ASBESTOS SANK Much scientific research has focused on studying the varying biological effects of different types of asbestos and on developing techniques for identifying asbestos fibers of unknown origin. In 1967 a "World Asbestos Bank" was established in Johannesburg, South more 6. South Africa# under the direction of the British Medical Research Council. The purpose of the "bank" is to provide standardized samples of asbestos from regions all over the world to be supplied to medical researchers for chemical, physical and biological investigation and for comparision purposes in clinical Studies. # # ## CHARACTERISTICS OF MAJOR COMMERCIAL TYPES OF ASBESTOS 0 9 sc* 1M < rH <D 0 P H l0H n 43 ~o s 41 9P 3 00 P -w PH (9 0 W rH P 9c > as 4> H p rH P a} a rl p p 0 a H 0 -H tH 99u &4 tO CO Z os at H o po o CO H o o Q .aH 00 p0 3O OO (B 0 8 a 43 41 04 e < 3 rH ffl P *H PH 9 &4 CO t4 rtH CO u <0 c > <3 -H u Pa as 0> a 9 (0 Z o; >1 p 4 s fc 3 tH a 9 G 9 <0 O' as 9 rH HG hH H PP X9 ap e9 3 tJ -H -H 9 *4r34 0) >PH 0 a c a 3 (0 ou oX -r4 P 04 a Jh xs ap P H 3 ,C p -H Tf rH >i-P c u H 0<3 TJ >4. a O O a 3 o to 5 co X SC 04 CO 2 s W Q25 Qw H <O CWU < S -a oe o3 o E-* J* < C Cralley, L. J., Keenan, R. G. and Lynch, J. R., "Exposure to Metals in the Manufacture of Asbestos Textile Products," AMERICAN INDUSTRIAL HYGIENE ASSOCIATION JOURNAL, September/October, 1967 Speil, Sm and Leineweber, J. P. "Asbestos Minerals in Modern Technology," INTERNATIONAL CONFERENCE OF BIOLOGICAL EFFECTS OF ASBESTOS; Dresden, East Germany; April 1968. Wagner, J. C., "Asbestosis in Experimental Animals," BRITISH JOURNAL OF INDUSTRIAL MEDICINE, 20:1, 1963. Wagner, J. c. and Skidmore, J. w., "Asbestos Dust Deposition and Retention in Rats," ANNALS OF THE NEW YORK ACADEMY OF SCIENCES December 31, 1965. '