Document JrrkJQp81nje6D0yM1y0gDdpX

FILE NAME Brakes BRK DATE 2006 DOC BRK153 DOCUMENT DESCRIPTION Letter to the Editor RE Asbestos Containing Brake Components and Respirability Authors Research Primarily Funded by Auto Companies Letter to the Editor re Evaluation of the size and type of free particulates collected from unused containing brake components as related to potential for respirability Dennis J. Paustenbach Ph.D. DABT CIH ChemRisk 25 Jessie St. @ Ecker Square Suite 1800 San Francisco CA 94105 415 896-2400 - phone 415 896-2444 - fax dpaustenbach@chemrisk.com Brent L. Finley Ph.D. DABT ChemRisk 25 Jessie St. @ Ecker Square Suite 1800 San Francisco CA 94105 415 896-2400 - phone 415 896-2444 - fax bfinley@chemrisk.com Patrick J. Sheehan Ph.D. Exponent 500 12th Street Suite 220 Oakland CA 94607 510 268-5008 - phone 510 268-5099 fax psheehan@exponent.com Gregory P. Brorby DABT Exponent 500 12th Street Suite 220 Oakland CA 94607 510 268-5006 - phone 510 268-5099 - fax gbrorby@exponent.com Abstract We are writing in response to the recent article by Atkinson et al regarding potential asbestos exposures associated with unused brake components Atkinson et al 2004 In that study rinsates of unused brake components were analyzed by transmission electron microscopy TEM for the presence of asbestos fibers We do not believe that the findings of Atkinson et al are informative and could have been predicted based on the study design and the fact that one would expect to find measurable TEM asbestos fibers on an unused brake component We also find that the paper did not provide a full or even partial discussion of the published literature with respect to industrial hygiene or epidemiology data The findings of Atkinson et al do not in our view further raise concerns about historical asbestos exposures experienced by automotive mechanics because of the vast amount of published literature to the contrary Keywords asbestos brake mechanics dust electron microscopy epidemiology exposure phase contrast microscopy To the Editor We are writing in response to the recent article by Atkinson et al regarding potential asbestos exposures associated with unused brake components Atkinson et al 2004 In that study rinsates of unused brake components were analyzed by transmission electron microscopy TEM for the presence of asbestos fibers The authors indicate that they detected the presence of free asbestos fibers that theoretically would not have been detected using the standard National Institute of Occupational Safety and Health NIOSH analytical techniques which employ phase contrast microscopy PCM The authors then conclude that this further raises concern about individuals occupationally exposed to work environments where these brake components are used We take issue with the authors methods and conclusions for several reasons First while the question of PCM vs. TEM as the most appropriate or accurate analysis for measuring airborne asbestos levels associated with brake components may be interesting from an academic perspective it is completely irrelevant to the issue of whether automotive mechanics or persons in any other occupation are at increased risk of developing an asbestos disease as a result of handling friction products Atkinson et al fail to discuss or even mention the fact that more than 20 epidemiology studies involving automotive repair workers have been published in the last 30 years none of which detected an increased incidence of asbestosis lung cancer mesothelioma or any other asbestos respiratory disease Paustenbach et al 2004 Goodman et al 2004 Indeed no published epidemiology study of automobile mechanics supports an increase in any asbestos disease As discussed in our recent paper the lack of asbestos diseases in this occupation is due largely to the documented fact that the long e.g. hour weighted airborne levels of asbestos in automotive service facilities where brake components are often handled extensively are very low and in some cases detectable Paustenbach et al 2003 In short we believe that the detection of asbestos fibers in the rinsate of brake components raises concern only for those who are unfamiliar with the vast body of relevant epidemiological and industrial hygiene literature to the contrary The methodology reported in Atkinson et al also raises several questions regarding the validity of the findings It is well known that asbestos fibers are naturally occurring and ubiquitous in environmental media including ambient air and tap water Nicholson et al 1980 Rowe 1983 It is therefore curious that Atkinson et al did not follow standard scientific methods and include analyses of a control rinsate that did not come in contact with brake components In addition the authors make several assumptions regarding the comparative results that theoretically might have been obtained using PCM instead of TEM The authors conclude that PCM would likely have failed to detect many of the fibers that were measured using TEM because the TEM method measures asbestos fibers of all lengths and widths while the PCM method measures fiber lengths of 5 microns or greater This is conjecture on the authors part and underscores a major flaw in the study design Rather than using TEM methods alone and then theorizing as to what the PCM results might have been it would have been far more informative to analyze samples contemporaneously by both methods We would point out that NIOSH conducted such comparative analyses in service garages in the 1970s and found that in many cases the PCM measurements were actually higher than the TEM measurements because PCM measures all fibers while TEM measures only asbestos fibers Johnson et al 1979 Finally there is the obvious question of relevance The authors fail to make any connection between the presence of rinsate fibers and actual airborne concentrations of asbestos The fact that some asbestos fibers are expected to be present on unused brake components which are at least 30 asbestos by weight renders the findings of Atkinson et al fairly uninformative and completely predictable Further it is reasonable to expect that airborne fibers associated with the handling of unused brake components were captured in the hundreds of air samples for brake mechanics collected by NIOSH in the 1970s and 1980s in U.S. service garages As described in our paper Paustenbach et al 2003 the vast majority of the term samples in these studies contained asbestos at levels below the current Occupational Safety and Health Administration OSHA permissible exposure limit PEL of 0.1 cc There are also instances where the authors chose to cite the published literature in a highly selective manner that does not provide a full context to the reader For example Atkinson et al note that Butnor et al reported the presence of chrysotile fibers in the lung tissues of mesothelioma patients wherein brake dust was the sole recognized source of asbestos exposure Butnor et al 2004 But they fail to acknowledge the conclusion of Butnor et al that friction product exposure such as that encountered by automobile mechanics is unlikely to contribute to the development of MM malignant mesothelioma In summary we do not believe that the findings of Atkinson et al were informative and could have been predicted based on the study design and the fact that one would expect to find measurable TEM asbestos fibers on an unused brake component We also find that the paper did not provide a full or even partial discussion of the published literature with respect to industrial hygiene or epidemiology data The findings of Atkinson et al do not in our view further raise concerns about historical asbestos exposures experienced by automotive mechanics because of the vast amount of published literature to the contrary Dennis J. Paustenbach Ph.D. DABT CIH and Brent L. Finley Ph.D. DABT ChemRisk San Francisco California Patrick J. Sheehan Ph.D. and Gregory P. Brorby DABT Exponent Oakland California Our research was primarily funded by Ford Motor Company DaimlerChrysler Corporation and General Motors Corporation Some of the authors have been involved as expert witnesses in litigation regarding the potential health hazards to mechanics historically involved in brake repair References Atkinson MAL O'Sullivan M Zuber S Dodson RF 2004. Evaluation of the size and type of free particulates collected from unused containing brake components as related to potential for respirability Am J Ind Med 545-553 Butnor KJ Sporn TA Roggli VL 2003. Exposure to brake dust and malignant mesothelioma A study of 10 cases with mineral fiber analyses Ann Occup Hyg 291 297 Goodman M Teta MJ Hessel PA Garabrant DH Craven VA Scrafford CG Kelsh MA 2004 Mesothelioma and lung cancer among motor vehicle mechanics A analysis Ann Occup Hyg 309 326 Johnson P Zumwalde RD Roberts D. 1979. Industrial hygiene assessment of seven brake servicing facilities -- Asbestos National Institute for Occupational Safety and Health January 29 Nicholson WJ Rohl AN Weisman I Selikoff IJ 1980. Environmental asbestos concentrations in the United States In J.C. Wagner ed Biological Effects of Mineral Fibres vol 2. IARC Scientific Publications No. 30. International Agency for Research on Cancer Lyon France pp 823-827 Paustenbach DJ Richter RO Finley BL Sheehan PJ 2003. An evaluation of the historical exposures of mechanics to asbestos in brake dust Appl Occup Environ Hyg 786-804 Paustenbach DJ Finley BL Lu ET Brorby GP Sheehan PJ 2004. Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads 1900 to present A state review J Toxicol Environ Health B 33-110 Rowe JN 1983. Relative source contributions to ingested asbestos exposure Environ Health Perspect 115-120