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FILE NAME Brakes BRK DATE 1992 DOC BRK241 DOCUMENT DESCRIPTION Letter to the Editor - American Journal of Industrial Medicine American Journal of Industrial Medicine 449 4511992 LETTER TO THE EDITOR Chrysotile Asbestos Mesothelioma and Garage Mechanics Key words case reports brake lining exposures fiber dimensions forsterite asbestos Drs Woitowitz and R^delsperger1991 commented on the series of articles on the relationship between exposure to chrysotile and mesothelioma published in the Journal in 1988. They also reported some cases of mesothelioma patients at their clinic who had worked at one time as garage mechanics Their conclusion was that they have found an increased incidence of mesothelioma among car mechanics exposed only to chrysotile with a mean dose of < years This conclusion was not in agreement with the general consensus expressed by the authors of the 1988 series of articles that either chrysotile has little or no mesothelioma potential Dunnigan 1988 Craighead 1988 McDonald 1988 or only extremely large doses of chrysotile can produce mesothelioma in man Churg 1988 Furthermore the conclusion reached by Drs Woitowitz and R^delspergerwas not justified by the data they presented What Drs Woitowitz and R^delspergerpresented was not an epidemiologic study Although one of the key words listed by the authors in the report was casecontrol study the report was definitely not a control study The best characterization of the data is that of a case report There were no controls mentioned in the report Furthermore there was no estimate of relative risk of mesothelioma in garage mechanics The authors reported that among mesothelioma patients at their clinic 14 had worked at one time as garage mechanics However in only three cases was there no other occupational exposure to asbestos In the remaining 11 the patients had also worked as fitters for turbines mechanics in the shipbuilding industry riggers welders or in other trades with asbestos exposure Thus with respect to potential exposure to lining dust alone only three cases should be counted The observatioofn three or a few cases of mesothelioma in garage mechanics with some minimal chrysotile exposure does not demonstrate an increased risk of mesothelioma in garage mechanics in general just as we cannot conclude that the use of hair driers increases mesothelioma risk based on an observation of a few cases of mesothelioma among persons who used hair driers Although mesothelioma is a rare Address reprint requests to Dr. O. Wong Appied Health Sciences Inc. 181 Second Avenue Suite 628 PO Box 2078 San Mateo CA 94401 Accepted for publication May 23 1991 '1992 Wiley Inc. 450 Wong disease there is a background rate of mesothelioma in the general population without any occupational exposure to asbestos Similarly there are numerous reports documenting that not all mesothelioma patients had occupational exposures to asbestos Some garage mechanics simply being part of the general population will develop mesothelioma even if they have no exposure to lining dust In their report Drs Woitowitz and R^delspergermentioned that there are currently about 250,000 garage mechanics in Germany The number will likely be several times larger if former garage mechanics are included Since the reported cases included both active and former garage mechanics and the case ascertainment ex- tended over several years it does not seem obvious that three cases of mesothelioma would represent a significant excess over the background rate However a proper assessment requires information on the number of mechanics their ages and the duration of observation In other words properly designed epidemiologic studies are needed to assess the relationship between exposure to brake lining dust and mesothelioma risk Several epidemiologic studies have provided data on this issue In one of the largest casecontrol studies of mesothelioma in North America McDonald and McDonald 1980 " examined the employment histories of 480 cases and their matched controls Eleven 11 cases and 12 controls were found to have worked as garage mechanics Based on these figures an approximate relative risk is estimated to be 0.9 In their 1980 report McDonald and McDonald concluded that there was no excess of mesothe- lioma in garage mechanics Later in 1986 McDonald and McDonald stated in an excellent review article on mesothelioma that increased risk was found for garage work McDonald and McDonald 1987 The relationship between occupational exposures and mesothelioma patients in Connecticut 1955-1977 was examined in a control study conducted by the Connecticut Tumor Registry Teta et al 1983 Included in the study were 220 cases of mesothelioma The authors reported a relative risk RR of 0.65 for automobile repair and related service based on six cases In another control study the epidemiologists at the National Cancer Institute compared occupational exposures between mesothelioma cases and their matched controls Spirtas et al 1985 Included in the study were 259 cases from Los Angeles and New York State 1975 1980. The RR reported for brake lining installation and repair was 1.0 with a 95 confidence interval of 0.6-1.6 Finally in a smaller control study in Louisiana Schiffman et al 1988 reported that none of the 37 mesothelioma cases had worked as a mechanic but there were two mechanics among the controls Thus epidemiologic data consistently and convincingly demonstrate that garage mechanics are not at an increased risk of mesothelioma The suggestion of an increased risk based on a case report in the presence of opposing epidemiologic data is not justified In addition to epidemiologic data there are also physical as well as biological reasons why garage mechanics are not at an increased risk of mesothelioma First the type of fiber used in brake lining is chrysotile which has little or no mesothelioma- producing potential Second during the braking process the temperature in the brake shoes reaches 600-800 At that temperature almost all chrysotile fibers are transformed into forsterite which is neither asbestos nor even fibrous Third based on industrial hygiene measurements the typical hr weighted average fiber concentration in a garage is less than 0.05 fiber Kauppinen and Korhonen 1987 Mesothelioma and Garage Mechanics 451 R^delspergeret al 1986 Cheng and O'Kelly 1986 These industrial hygiene indicate surveys also that almost all fibers detected are less than % longer than 5 ...m than 2-3 ...mwith less Therefore based on a consideration of fiber type physical transformation fiber length and fiber concentration exposure to lining dust should not increase mesothelioma risk among garage mechanics Most importantly as discussed above opposing epidemiologic data have consistently demonstrated that garage mechanics are not at an increased risk In the presence of epidemiologic data I do no think that case reports such as the one by Drs Woitowitz and R^delspergerare very helpful in determining the relationship between lining dust exposure and mesothelioma risk Otto Wong SCD FACE Applied Health Sciences Inc. San Mateo CA 94401 REFERENCES Cheng VKI O'Kelly FJ 1986 Asbestos exposure in the motor vehicle repair and serving industry in Hong Kong J Soc Occup Med 104-106 Churg A 1988 Reply to Dr. Dunnigan Letter to the editor Am J Ind Med 235 238 Craighead JM 1988 Response to Dr. Dunnigan's commentary Letter to the editor Am J Ind Med 241 243 Dunnigan J 1988 Linking chrysotile asbestos to mesothelioma Am J Ind Med 205-209 Kauppinen T Korhonen K 1987 Exposure to asbestos during brake maintenance of automobile vehicle by different methods Am Ind Hyg Assoc J 488 504 McDonald JC 1988 Tremolite other amphiboles and mesothelioma letter to the editor Am J Ind Med 247-249 McDonald AD McDonald JC 1980 Malignant mesothelioma in North America Cancer 1650- 1656 McDonald AD McDonald JC 1987 Epidemiology of malignant mesothelioma In Antman K Aisnerr J eds Asbestos Malignancy London Grune & Stratton Inc. pp 31-55 R^delspergerK Jahn H Bruckel B Manke J Paur R Woitowitz HJ 1986 Asbestos dust exposure during brake repair Am J Ind Med 63-72 Schiffman MH Pickle LW Fontham E Zahm SH Falk R Mele J Correa P Fraumeni JF 1988 control study of diet and mesothelioma in Louisiana Cancer Res 2911-2915 Spirtas R Keehn R Wright W Stark A Beebe G Dickson E 1985 Mesothelioma risk related to occupational or other asbestos exposure preliminary results from a control study Am J Epidemiol 518 Teta MJ Lewinsohn HC Meigs JW Vidone RA Mowad LZ Flannery JT 1983 Mesothelioma in Connecticut 1955-1977 occupational and geographic associations J Occup Med 749 756 Woitowitz HJ R^delspergerK. 1991 Chrysotile asbestos and mesothelioma Letter to the editor Am J Ind Med 551 553