Document zQL7jRNG565j41x4J4733VaLn

s / I ASBESTOS AkD BRAKE LIFTINGS The contribution of asbestos from broke lining wear to smbient air pollution is infin itesimal, even in urban areas, and is "on inconsequential health factor in urban air pollution."1 ' Brakes Rely On Asbestos The use of high heal and friciicn resistant chrysotile asbestos in the manufacture of motor vehicle brake linings was developed in Great Britain In 1908. Today, more than 65 years later, no other material has been found which wiil provide the same degree of sate, dependable slopping performance as asbestos. Throughout the world, more than 300 million motor vehicles of all types -- automobiles. Irucks, buses --rely on asbestos-containing brake linings to bring them to safe, sure slops, lime sfler lime after lime. While formulations vary consider ably, an average automobile brake lining contains approximately 55 percent asbestos by weight, while the asbestos in a truck lining constitutes around 33 percent of the total.' Approximately 50.000 tons of asbestos is used in the manufacture of brake linings in the United States each year.2 Health Questions Arose The inhalation of excessive quantities of asbestos fiber in occupational settings can cause respiratory disease and cancer. In the mid-sixties, speculation arose whether the gradual in service wear of asbc-stos-containing brake linings would release potentially harmful amounts of asbestos fiber into the ambient air. This concern was heightened by repeated findings ol small amounts ol asbestos liber in the lungs of some city dwellers not known to have had occupational exposure lo asbestos. While it is now generally recognised by the worldwide asbes tos-health medical community that, these small amounts of fiber do not constitute a hazard to the health of the general public,0-4 the question still remained unanswered what contribution emissions from asbestos-containing brake linings made lo urban air pollution. The results of research under taken to answer this question are now available. Natural Sources ' Asbestos exists naturally in small though detect able amounts in serpentine rock formations through out the world and is constantly being released into lire atmosphere through erosion by wind and water. Asbestos is thus natural to our environment and -- as analysis ol dated ice (rom the polar caps have revealed--Iras been tor thousands or even millions o( years. Thus, the mere presence of asbestos in ambient air is not prima facie evidence of pollution from brake linings or other sources. Fcr this reason, investigations into this question have had to be conducted cither on specially equipped cars and trucks under actual driving conditions or in the laboratory on sophisticated brake testing dyna mometers. Emissions Hot Significant ' The results of three such research projects carried out over the past six years support the conclusion that emissions from brake lining wear are not a significant source of asbestos in the envi- ronmenl.'-2-5 Some of the results of the three studies are summarized as follows: * When brakes are applied, the high heat of friction converts more than 99 percent cl the asbestos in the lining to a non-fibrous, non-toxic material called forsterite. The two most recent investiga-' tions shewed conversion ratios ot 99.7 percent2 and 99.95 percent5 respectively. * Total airborne emissions of free asbestos liber from brake lining wear amount to approximately 2'A tons each year for the entire United States.2 This is less than one-half ol one percent of the total particulate emissions in" a city the size of Los Angeles in a single day! * The calculated contribution of asbestos from brake lining wear to the air in a typical urban area is less than 0.07 nanograms per cubic meter of air (a r.anogram is one-biltionth of a gram).5 Sci entists estimate that asbestos fiber concentra tions in urban areas average between 5-10 nano grams per cubic meter. It is therefore clear that "the wear o( brake lining produces, at most, a smalt fraction of the asbestos fiber in urban air."5 *i References 1. "Drake Lining Decomposition Products," by Jeremiah Ft. Lynch, National Center for Urban and Industrial Health, U.S. Public Health Ser vice, Journal of the Air Pollution Control Associ ation. Vol. 18, No. 12. pp. 824-826, 1968. 2. "Brake and Clutch Emissions Generated During Vehicle Operation," by Michael G. Jacko. Robert T. DuCharme and Joseph H. Somers, presented at Automobile Engineering Meeting, Society of Automotive Engineers, Inc.. Detroit, Mich., May 14-18. 1973. (Study sponsored by U.S. Environmental Protection Agency.) 3;. "Asbestos: The Need For and Feasibility of Air Pollution Controls," Committee on Biologic Effects of Atmospheric Pollutants. National Academy of Sciences, IS8N 0-309-01927-3, | 1971. . 4. "Report of the Advisory Committee on Asbestos Cancers to the Director of the International ' Agency for Research on Cancer," British Jour ' nal of Industrial Medicine, Vol. 30, pp. 180-186, 1973. 5. "Asbestos Emissions from Brake Dynamom eter Tests," by A. E. Anderson, R. L. Gealer, R. C. McCune and J. W. Sprys. presented at Automobile Engineering Meeting. Society cl Automotive Engineers, Inc., Detroit. Mich., May 14-18, 1973. Additional Copies of This Pamphlet Are Available Asbestos Information Association/North America 1660 L Street. N.W. Washington, D.C. 20036 * Z 2. J* - /0Z*. /?%--