Document e717Xdr9bd2XNaEKav3VYzDJe

Johns Studies of asbestos exposure and human health 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 heavy occupational exposure. There is no evidence that anyone has ever contracted any disease from exposure to the wearing or weathering of brake lin ings, 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.1 He concluded that any asbes tos that might come from brake lining wear was "an inconsequential health factor in urban air pollu tion." The study provided scientific evidence refut ing 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 brake linings 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 proportion of the total asbestos used in the manufacture of brakes. Many sources of the respirable fibers not asso ciated with asbestos products have been iden tified, 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 expo sure do not extend to the public. In 1967, P. E. Enterline, Ph.D.,and M. A. Kendrick, Ph.D., reported on the reduction of asbestosis among workers in asbestos fabricating industries where protective measures have been taken.2 They pointed out that the small amount of asbestos to which 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 patho genesis (development) of disease it must be very small indeed....Asbestos dust at levels to which general populations are exposed prob ably is of little importance in the etiology (causation) of disease." "ASBESTOS BODIES" STUDIED In the mid-1960's the question of public exposure was discussed in studies that reported finding socalled "asbestos bodies" in the autopsied lungs of some city dwellers who were 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 asbestosis.3 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 demon strated to be present in so many urban dwellers to the frequency present in a minimal basal asbestosis would require an increase by hun dredfolds and to get a more diffuse classical asbestosis with pulmonary disability the mul tiplying factor might well be in many millions." In a similar study the same year, Drs. Lily Anjilvel and W. M. Thurlbeck noted that there is no risk of cancer to the general population from asbestos ex posure.4 These researchers said: KMX 01719 IZ\ ENVIRONMENTAL FACTS/Asbestos "In our series there seemed to be no particular association between malignancy and the pres ence of asbestos bodies...asbestos bodies are not more common in patients with malignant disease in the autopsy populations we have studied, and thus casual exposure to asbestos is not an important cause of malignancy in the general population." Other studies 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 term "asbestos body" is misleading if the core sub stance 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 in haled 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 exten sively, has suggested that a more accurate name would be "ferruginous (iron-like) bodies."5 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 ap peared in the professional literature and was widely reported in the news media with varying degrees of sensationalism."6 He commented specifically: "...the basic assumption that asbestos-like bodies can only be produced from asbestos has proved incorrect and this casts consider able doubt on the theory that has been the chief basis of the asbestos 'scare.' " OTHER CAUSES OF FIBROUS "BODIES" 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 4 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.7 Publishing in 1968, they said: "On the premise that the fibrous bodies ob served in the lungs of persons at autopsy are all "asbestos bodies" and that coated fibrous bodies are a specific reaction to asbestos fi bers, some investigators have concluded that asbestos fibers are significant air contam inants....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 min erals with some degree of fibrous structure.... Respirable fibers of vegetable origin may be from both live and dead plant tissues....Ani mal 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 emerging organic types used in textiles, fillers, containers, fila ments, 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 uses of asbestos--in schools, houses, thea ters, ships, aircraft, offices and other public facil ities, furnaces, boilers, firefighting equipment and in a myriad of everyday products. With the twentieth century growth in the use of asbestos has come recognition of the need to cope with occupational hazards associated with exces sive inhalation of asbestos dust. Much progress has KMX 01720 !i3iENVIRONMENTAL FACTS /Asbestos 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 occupa tional health hazards of asbestos see no evidence that asbestos poses any risk to the general public. There is no evidence that asbestos dust is present in the general air in amounts of any significance to hu man 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 being investi gated 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. To forego the many benefits of these and other products of modern technology--simply on the basis of suspicions that are unsupported by medical evidence--would be a great and unwarranted dis service to the American public. REFERENCES ' Lynch, J., "Brake Lining Decomposition Products," Meeting, AMERICAN CONFERENCE OF GOVERNMENTAL INDUS TRIAL HYGIENISTS, St. Louis, May, 1968. 3 Enterline, P. E., and Kendrick, M. A., "Asbestos Dust Expo sures at Various Levels and Mortality," ARCHIVES OF EN VIRONMENTAL HEALTH, August, 1967. 3 Thomson, |. G., and Graves, W. M., "Asbestos as an Urban Air Contaminant," ARCHIVES OF PATHOLOGY, May, 1966. 4 Anjilvel, L. and Thurlbeck, W. M., "The Incidence of Asbestos Bodies in the Lungs at Random Necropsies in Montreal," CANADIAN MEDICAL ASSOCIATION IOURNAL, December 3, 1966. 5 Gross, P., Cralley, L. J., and de Treville, R. T. P., "Asbestos Bodies: Their Nonspecificity," AMERICAN INDUSTRIAL HYGIENE ASSOCIATION IOURNAL, November/December, 1967. ` Davis, J. M. G., "Asbestos Bodies and Bioeffects--A Detec tive Story" presented at the meeting of the INDUSTRIAL HYGIENE FOUNDATION, Pittsburgh, Pa., October, 1967. 7 Cralley, L. J., Keenan, R. G., Lynch, J. R., and Lainhart, W. S., "Sources and Identification of Respirable Fibers," AMERICAN INDUSTRIAL HYGIENE IOURNAL, March/April, 1968. KMX 01721 Johni-Mar>vil US1 ENVIRONMENTAL FACTS/Asbestos For further information on this subject please contact: Environmental Affairs Department, Johns-Manville Greenwood Plaza Denver, CO 80217 EA-8P 3711 KMX 01722 Printed in USA