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FILE NAME Brakes BRK DATE 1977 Jan DOC BRK067 DOCUMENT DESCRIPTION Journal Article - Asbestos Content of Dust Encountered in Brake Maintenance and Repair - Proceedings of the Royal Society of Medicine Oe ane - Volume 70 Number 1 January 1977 Proceedings of the Royal Society of Medicine Management Management Management Pulmonary Pulmonary of Tuberculosis Pulmonary Tuberculosis Medicine the Crossroads page 16 ' 4 page 4 Published by The Royal Society of Medicine 1 Wimpole Street London W1M 8AE ee ** and Academic Press ** London New York San Francisco DATS the the om 32 Proc roy Soc Med Volume 70 January 1977 irregular or nodular interstitial opacities of limited extent and intensity on their films Silica or asbestos exposure had occurred in 22 of the work force examined Such exposures had occur- red in various job categories in the titanium facility as well as in prior occupations Eight of the 26 workers with abnormal rays had had silica or asbestos exposure No clear pattern of restrictive disease in relation to ray findings could be seen Summary and Conclusions Clinically significant or symptomatic pulmonary disease was infrequent in a survey of 207 currently employed production workers in a plant producing titanium dioxide from ilmenite ore Evidence of airways obstruction was found in 47 of all workers including 38 % of workers who had never smoked regularly This abnormality was not frequently accompanied by disabling shortness of breath Despite the fact that approximately 90 of the group of workers examined had worked for 20 years or more radiological changes consistent with pneumoconiosis were relatively few and unrelated to the respiratory abnormalities observed We conclude with the caveats inherent in a prevalence study in which only half of the eligible long workers were examined that occupational exposure associated with titanium production by the sulphate process may commonly cause undesirable irritation of the upper and lower respiratory tract and functional abnormalities of the lung but does not result in an important incidence of serious occupational lung disease Individual workers may however suffer unwanted abnormalities These findings of course do not speak to the presence or absence of increased risk of malignant pulmonary disease This is being separately studied Acknowledgment This research study was sup- ported in part by National Institute for Occupational Safety and Health Contract 99-74- 91 Asbestos Content of Dust Encountered in Brake Maintenance and Repair by N Rohl PhD A M Langer PhD R Klimentidis BA MS Wolff PhD and I J Selikoff MD Environmental Sciences Laboratory Mount Sinai School of Medicine of the City University of New York New York NY 10029 Asbestos in Brake Linings The composition of automotive brake linings includes chrysotile asbestos fibre which comprises about % of the friction material The exposure of garage workers to asbestos during brake lining maintenance and repair has recently been investigated Rohl et al 1976 This important issue was studied because a large labour force is potentially exposed over one million people in the United States alone Consequently it was thought essential to determine if chrysotile fibre survives braking and to measure the amounts liberated as an aerosol during maintenance and repair oper- ations _ Investigators in the past have expressed doubt as to whether chrysotile fibres can survive the high temperatures generated during braking Lynch 1968 Hickish & Knight 1970 Hatch 1970 Chrysotile is alleged to be subjected to temperatures in excess of 800 which would cause its thermal transformation to forsterite or to an amorphous magnesium silicate phase While hot spots up to 1000 may be attained Carroll 1962 the heat distribution is nonuniform and other processes in addition to thermal wear contribute to de- gradation of brake linings For example abrasion and macroshear may cause physical breakdown Burwell 1957 Mizutani et al 1973 Accordingly brake lining disintegration by these mechanisms may liberate partially altered or even unaltered chrysotile fibres REFERENCE Miller A Chuang M & SelikoffI J 1976 American Review of Respiratory Diseases 113 Suppl p 89 abstract Analysis of Brake Drum Dust Initially ten samples of automobile brake drum dusts from brake repair shops in New York City . were collected and examined by optical microscopy ray diffraction transmission electron mic- roscopy and energy dispersive ray spectroscopy to determine the presence of chrysotile Optical microscopy The detection of chrysotile in brake drum dust by optical microscopy is hindered by the nature of the debris matrix consisting largely of opaque pyrolyzed phenolic resin binders and road dust Chrysotile particularly small fibres has low optical relief and low birefringence which further hinder its identification Only in rare instances have large fibres with optical Section of Occupational Medicine 33 Table 1 Chrysotile asbestos content of brake drum dusts ray diffraction scan Great Britain West Germany France United States of America Finland Western Australia No. samples 8 8 1 No. positive 6@ se 1 10 10 5 3 7 4 39 29 Weight percent Mean Range CNC 0.7-2.3 CNC 0.5-3.2 CNC FE FE FE -2.4 = 2.4 1.1 2.0-15.1 0.8-2.5 0.5-2.3 @ I sample possibly positive Transmission electron microscopy No. positie 8 1 10 S 7 39 properties consistent with chrysotile been observed with this technique ray diffractometry The ten brake dust samples were analysed by ray diffractometry in both continuous and scan mode The diagnostic reflection selected for chrysotile 3.66 A hkl 004 was scanned in the count mode By comparison with external standards the amount of chrysotile present can be determined Chrysotile reflections were observed in all samples with weight percentages estimated to range from 2 to 15 average 4.5 Lead compounds quartz carbonate minerals clays halite NaCl graphite micas and alpha were also identified in vari- ous samples Twenty additional brake drum dust samp- les were collected by colleagues in four European countries and Australia The samples were obtained from areas representing variable circumstances such as driving conditions friction material composition type of automobile and climate The results of ray diffraction analyses are presented in Table 1. Of the 39 total samples analysed including 10 United States samples chrysotile was found in 29 or about fourths The mean chrysotile content varied from 1.4 in the seven Australian samples to 4.5 in the New York City samples The thermal breakdown product of chrysotile i.e. forsterite which might be expected to form as a result of recrystallization was not unambiguously detected in any sample Transmission electron microscopy TEM In order to verify the results of ray diffraction analysis the brake dust samples were prepared for electron microscopic analysis by means of a technique which disperses the dust particles in a nitrocellulose film without altering particle sizes Both free chrysotile fibre bundles and fibrils were observed in all 39 samples Most of the chrysotile retained its characteristic morphology without significant alteration and selected area electron diffraction patterns obtained on representative fibres dem- onstrated the preservation of crystal structure as . well Fig ) Fibre size distribution In ten brake dusts sampled in New York City free asbestos fibres were sized by TEM at magnification 000. The results showed that about 80 of chrysotile is in free fibril form and is shorter than 0.4 ...min length Over 57 have lengths of about 0.2 ...mAt magnification 000 such a fibre would be about cm long If lower magnification were used to scan for asbestos significant numbers of fibres might not be detected It is obvious that most fibres are too small to be seen by optical microscopy The Asbestos Standard adopted by the Occupational Safety and Health Administration OSHA of the US Depart- ment of Labour is limited to optical microscopy and neglects to count or control fibres less than ...mlong On the other hand accumulating evidence suggests that such small asbestos fibres may produce disease Holt et al 1964 Davis 1965 Pott et al 1972 Wagner et al 1973 Hilscher et al 1970 Bouhuys 1975 ra Air sampling Eight personal air samples taken during brake repair work were selected for electron microscopic analysis This was done in order to positively identify chrysotile in the samples and to determine whether a systematic relationship existed between optically and submicroscopically visible fibres for this type of exposure The memb- rane filters were ashed in plasma oxygen to eliminate organic materials and the residue was prepared for electron microscopy by a rubout technique Nicholson et al 1971 which comminutes large chrysotile fibre bundles into individual fibres and fibrils Large inorganic particles are likewise reduced in size permitting all chrysotile to be seen and measured Chrysotile was identified in the eight samples in both fibre and fibril form Fig 2 By measuring a large number of fibres at magnification 42 000 and converting the volumetric data into mass a concentration per volume of air is determined Comparison of optical microscopic 34 Proc roy Soc Med Volume 70 January 1977 fibre counts and the electron microscopic asbestos mass calculations indicates that a positive cor- relation exists between the two sets of data These results show that the standard OSHA optical fibre counts may be only indicative of the total asbestos exposure Asbestos Exposure of Workmen After the identification of chrysotile in the brake drum dusts asbestos fibre exposure during maintenance and repair was determined by personal air sampling carried out at automobile repair shops taxi fleet repair shops and a municipal truck repair shop in New York City Air sampling and analyti- cal methods for the determination of fibre con- centrations were in accordance with the OSHA techniques Bayer et al 1975 Present regulations of OSHA prohibit asbestos concentrations of 5 fibres per millilitre f ml or greater longer than ...mas a weighted average and concentrations above 2 f'ml will be illegal after July 1976. Peak concentrations or maximum excursions of 10 ml are permitted by the regulations In brake lining inspection and repair the wheel Sgr yer te m4 3 ' Oe brent Cle Be -_ \ sewr wae adit geet WBa ef aLie whei thinedbuoray chrysotile fibres Fig 1 Electron photomicrographs ofbrake drum dusts taken at various magnifications A the numerous chrysotilefibrils have average lengths of 0.4 mor less ^ 30 000 B. large numbers of imbedded in and protruding from opaque particle probably pyrolized phenolic resin binder ( ^ 30 000 C large chrysotile fibre bundle ^ 45 000 D. large particle in left centre ofphotograph is the same as in C but cannot be identified at low magnification ( ^ 5400 Section of Occupational Medicine 35 is removed from the axle and loose dust is com- monly removed from the drum and back plates by means of a jet of compressed air A survey of 220 garages in Baltimore and Washington DC has shown that this is the method of choice in 80 of the shops Castleman et al 1975 A similar situation exists in New York City The data in Table 2 show that fibre concentrations are high in the breathing zone of the operator during com- pressed air blowing An asbestos concentration gradient diminishing with time and distance away from the operation appears to occur Persons up to 22 m from such activity are exposed to measur- able concentrations of asbestos Personal air sampling was also conducted at New York City Department of Sanitation where truck brakes are repaired Used linings are salvaged by machine grinding to remove dirt and grease from the surface New linings are bevelled by grinding to reduce noise and improve break Accordingly these studies relate to levels of as- bestos exposure which may be experienced by workers engaged in brake lining manufacturing Table 2 shows that fibre concentrations experi- enced during grinding ranged from 1.7 to 7.0 ml of air in the breathing zone of the operator The background or area samples for this operation ranged from 1.2 to 0.2 ml with a general decrease athe Ate Nas srearlise Fig 2 Electron photomicrographs of personal air samples taken during brake repair work Clumps of chrysotile are associated with opaque particles of road dust and resin binders A B. x 60 000. D ^ 000 ream ame e ee ae - wea to. 36 Proc roy Soc Med Volume 70 January 1977 Table 2 Personal air samples automobile and truck brake repair Automobile brake repair Blowing dust from brake drums Distance 1-1.5 m Distance 1.5-3 m Distance 3-6 Background 5 min after air jet blowing distance 3.6-16 m Background 7-14 min after air jet blowing distance 19.6-22.6 m No. samples Peak fibre concentration fibres per ml Mean Range 432 150 432 3.3 432 1.6 N 0.2 WN 0.1 6.6-29.4 2.0-4.2 0.3-4.8 0.1-0.2 0.1 WN Truck brake repair Renewing used linings by grinding distance 1-1.5 m Background to grinding used linings Distance 3.3 m Distance 8.3 m Distance 20.0 m Bevelling new linings Background to bevelling new linings Distance 2.4 m Distance 3.6 Distance 9.1 m 10 2214 2214 2214 2214 121 121 121 4.8 1.5 0.8 37.3 0.4 1.7-7.0 1.2-1.7 0.6-1.0 0.2 23.7-72.0 0.6 0.3-0.5 0.3 . 23 away from the operator From six to ten other mechanics work within an area up to 20 m from this operation are exposed to asbestos as well Since a person breathes about one cubic metre of air an hour multiplication of the fibre concentrations by one million gives the number of fibres inhaled during this period Fibre concentrations measured during bevelling of truck linings were as high as 72 ml and averaged about 37 ml Background counts were measured up to 9.1 m away from this operation 0.3 ml Fibre concentrations measured during drilling holes for rivets and grinding ranged from 0.3 to 29.2 ml as reported by Boillat & Lob 1973 Four of the nine values exceeded 5 ml Conclusions . The existence of significant exposure during brake servicing operations necessitates the following measures ledge support under a grant from the National Institute of Environmental Health Sciences ES 00928 and support by the Ford Motor Company MSW wishes to acknowledge support under a doctoral fellowship from the NIEHS ES 02565 We are grateful to the following for assistance in obtaining brake dust samples Professor Donald Bowes University of Glasgow Scotland Mr L B Bowes Department of Labour and Industry Adelaide South Australia Dr Trevor Turner Adelaide South Australia Professor Jean Bignon Hospital Laennec Paris France M^/unuHarme | Geological Survey of Finland Otaniemi Finland Dr G. Ga^lHelsinki University of Technology Helsinki Finland Dr K Robock and Dr W Kl^sterkotterInstitut f^...rHygiene und Arbeitsmedizin des Klinikum der Universit^/t Essen West Germany 1 Implementation of industrial hygiene pro- cedures to control exposure 2 Clinical studies of garage mechanics to determine evidence of asbestos disease 3 Epidemiological studies of the mortality experience of exposed workers In addition the entire variety of dusts and other materials present in brake repair work should be characterized in order to determine its disease potential especially silica and lead compounds Acknowledgment The authors wish to acknow- REFERENCES Bayer S G Brown TA TA & Zumwalde R D Document TR US Public Health Service Cincinnati OOhhiioo Boillat MA & Lob M 1973 Schweizerische medizinische Wochenschrift 103 39 Bouhuys A 1975 Annals of Internal Medicine 83 898 Burwell JT 1957 Wear 119 Carroll G 1962 British Plastics 35. 414 Castleman B. Camarota LA LA Fritsch Crawley G 1975 Public Health Reports 254 J Mazzocchi & Davis J M J 1965 Annals of the New York Academy of Sciences 132 98 Section of Occupational Medicine 37 Hatch D 1970 Annals of Occupational Hygiene 13 25 Hickish D E & Knight K L 1970 Annals of Occupational Hygiene 13 17 Hilscher W Sethi S Friedrichs K H & Pott F 1970 Naturwissenschaften Naturwissenschaften 57 356 Holt P F Mills J & Young D K 1964 Journal of Pathology and Bacteriology 87 15 Lynch R . 1968 Journal of the Air Pollution Control Association 18 824 Mizutani Y Obara H & Nakajima K 1973 Wear 23 387 Nicholson WJ WJ Rohl A N & Ferrand E F 1971 In Proceedings of the Second International Clean Air Congress Ed H M England & W T Berry Academic Press New York pp 136-139 : Pott F Huth F & Friedrichs K H 1972 Zentralblatt f^...rBakteriologie Abt , Originale 155 463 Rohl N Langer A M Wolff MS & Weisman I 1976 Environmental Research 12 110 Wagner JC Berry G & Timbrell V 1973 British Journal of Cancer 28 173 Neurotoxic Properties of Certain Aliphatic Hexacarbons by Peter S Spencer PhD and Herbert H Schaumburg MD Departments of Pathology and Neuroscience Saul R Korey Department of Neurology Rose F Kennedy Center Albert Einstein College of Medicine Bronx New York 10461 USA several species of experimental animal Duckett et al 1974 Mendell et al 1974 Spencer Schaumburg Raleigh & Terhaar 1975 These studies demonstrated that prolonged intoxication by inhalation or subcutaneous injection caused the insidious development of symmetrical weakness first in the hindlimbs and later in the forelimbs The first signs of peripheral neuropathy developed after 4 to 12 weeks of continuous inhalation of 200- 600 parts of MBK and after 12 to 16 weeks of intermittent inhalation of 1300 parts of MBK The onset of MBK neuropathy was associated with a reduction in the sciatic nerve conduction velocity Mendell et al 1974 an indication of nerve damage also found in rats and monkeys inhaling 1000 or 100 parts MBK intermittently for periods of 3 and 8 months respectively Johnson 1975 the figure of 100 parts being the recommended Threshold Limit Value in the United States Recent studies have suggested that " concurrent exposure to MEK and MBK will produce neuropathy more rapidly than in animals exposed to MBK alone Saida et al 1976 Methylethylketone alone or MBK alone produce no neurotoxic effects Spencer & Schaumburg 1976 The purpose of the present paper is to emphasize the importance of chronic testing of potentially neurotoxic compounds in experimental animals to describe the range of hexacarbon compounds which have been identified as neurotoxic agents and finally to characterize and illustrate the pathological basis for the onset of the nervous system disease A total of seven hexacarbon compounds have been tested in this study Table ) During the summer of 1973 an outbreak of per- ipheral neuropathy developed among a large group of employees of a fabric manufacturing plant in Ohio USA Billmaier et al 1974 The - disease was characterized by distal weakness and sensory loss symmetrically in both the hands and the feet Allen et al 1975 The most severely affected individuals worked in the printing department where colouring inks dissolved in volatile solvents were applied to the surfaces of plastic coated fabrics For several years the printing process required the use of a 1 solvent mixture containing methylethylketone MEK and methylisobutylketone MIBK butylketone MBK was gradually introduced in the summer of 1972 to replace the MIBK butylketone was in its maximal use by December 1972 and the first case of peripheral neuropathy occurred shortly thereafter The recent introduction of MBK into the printing department of the plant coupled with other isolated outbreaks of neuropathy in individuals chronically exposed to MBK suggested that this compound had neurotoxic properties MBK produced peripheral neuropathy in Table 1 Hexacarbon compounds tested 1 hexane CH CH 2 butylketone CH CH CH, 3 hexanedione CH COCH 4 hexanediol CHOHCH 5 hexanedione CH COCH COCH CCHOCH COCH CH 6 hexadione CH COCO CHCCH H3 7 hexanediol HOCH CH2CH2CH2CH2CH2OH The first compound hexane an important solvent and a minor component of petrol was indicted in several reports as a possible neurotoxic agent Herskowitz et al 1971 Korobkin et al 1975 Rats were exposed continuously to atmospheric levels of 400 to 600 parts of hexane for up to five months 500 parts being the US Threshold Limit Value for hexane see also Schaumburg & Spencer 1976 The second compound methyl butylketone the solvent implicated in the outbreak of neuropathy was administered to cats by subcutaneous injection of 150 mg twice daily for periods up to six months see also Spencer & Schaumburg 1976 The third compound 2,5-