Document dZmMkbz1rwxoqy3nMpNGNpGe

FILE NAME Brakes BRK DATE 2012 DOC BRK238 DOCUMENT DESCRIPTION Journal Article - Determining the Frequency of Asbestos Use in Automotive Brakes Determining the Frequency of Asbestos Use in Automotive Brakes from a Fleet of Road California Vehicles Joseph De Vita Stephen Wall Jeff Wagner Zhong Wang and Leela E. Rao California Air Resources Board Mobile Source Control Division El Monte California 91731 United States * California Department of Public Health Environmental Health Laboratory Richmond California 94804 United States ABSTRACT Asbestos is a known human carcinogen and recent regulation in i California limits asbestiform fibers in brakes to trace levels beginning in 2014 Chrysotile Asbestos although there is no corresponding federal requirement In order to gauge the current prevalence of asbestos use in automotive brake applications the California Air Resources Board tested brake linings from 137 light- and medium vehicles and 54 heavy vehicles Only about % of the light- and medium- duty vehicle brake linings contained chrysotile asbestos All of those brake linings were drum shoes which are generally being phased out No asbestos was found in low mileage vehicles presumed to have their original stock linings from the vehicle manufacturer Additionally no asbestos was found in the heavy Cut Away of Brake Lining vehicle brake shoe linings sampled Given the small percentage of vehicle brake 100um linings with asbestos observed it appears that the prior federal ban that was subsequently overturned in combination with a threat of litigation has reduced asbestos use in brake linings However our study was limited in scope and without a national ban the current and future prevalence of asbestos in brakes is uncertain suggesting the need for continued monitoring of materials released as toxic air contaminants in normal braking operations M@ INTRODUCTION Asbestos has been used in many products including automotive brake linings cements millboard roofing materials floorings resistant gaskets and electrical wiring insulation For decades asbestos was the primary material in automotive brake linings due to its thermal stability low wear rate low cost and other useful characteristics It is estimated that in 2003 10 of the estimated world sales of chrysotile asbestos was used for brake linings and clutch facings. Chrysotile asbestos was eventually shown to be a human carcinogen and has become the source of much debate and an aggressive litigation industry over the past few decades Central to the litigation are risks to auto mechanics from handling brake linings containing asbestos as identified by Castleman et al.4 and reviewed subsequently by Lemen and Welch However asbestos particles are also released into the general environment as a result of routine driving and braking with airborne concentrations of asbestos close to major highways and roadways up to 3-6 times higher than at locations away from roadways As of 2011 55 countries including all member states of the European Union have banned the use of all forms of asbestos in manufactured products In 1989 the United States Environmental Protection Agency USEPA issued a rule that would have phased out the manufacture import and processing of original equipment manufacturer OEM containing automotive brakes by 1996 but that rule was subsequently overturned in 1991 by the fifth Circuit Court of Appeals In reaction to the impending U.S. asbestos ban rising concern in other industrialized countries about asbestos health effects and ongoing litigation manufacturers of brake linings began searching for asbestos alternatives A 1998 report indicated 25 of new vehicles built in the U.S. with OEM drum brakes contained asbestos but by 2004 a USEPA survey of the nine major OEMs found that none of the major manufacturers sold asbestos brakes in new vehicles or as replacement parts in the U.S. Instead OEMs were opting to use alternative formulations such as metallic semimetallic synthetic and ceramic fibers However no legal impediment to using asbestos exists and a 2007 Occupational Safety and Health Administration OSHA survey found that some vehicles of two OEMs were still equipped with asbestos- containing friction products Furthermore aftermarket brake linings containing asbestos are still available as demonstrated by Senator Patty Murray WA who brought an asbestos brake lining purchased by her staffer to a 2007 U.S. Senate Subcommittee hearing in an effort to dispel the myth that asbestos products are no longer available in the U.S. Current litigation regarding asbestos cancer may lead to further reductions in asbestos use and even greater nationwide reductions may occur due to a California ban on asbestos in friction materials that goes into effect in 2014. Received August 1 2011 Revised | December 14 2011 Accepted December 14 2011 Published December 14 2011 ACS Publications w '2011 American Chemical Society 1344 dx doi org es202667d | Environ Sci Technol 2012 46 1344-1351 Environmental Science & Technology Asbestos is known to cause lung cancer pleural fibrosis scarring of the lung tissue and mesothelioma a cancer of the membrane that lines the body cavities and some internal organs The onset of mesothelioma can involve a latency of 10-50 years from the time of exposure thereby accounting for current litigation based on exposures from past decades The etiology of mesothelioma and other asbestos diseases involves various environmental sources of asbestos most of which are anthropogenic toxicological concern have Historically been those asbestos that can fibers of penetrate deep into the lungs which are typically between 5 and 10 ...min length As such OSHA has permissible exposure limits on airborne asbestos fibers which are defined as those 5 ...mor longer with an aspect ratio 1.e. length ratio of 3 or longer However the definition of relevant fibers is somewhat variable and a recent review by Lemenfound that there was significant evidence for toxicity of asbestos fibers less than 5 ...min length which outnumber fibers greater than 5 m in brake wear debris by a ratio of 300 Relevant motor vehicle sources of asbestos are brake linings clutch facings gaskets and automatic transmission compo- nents Of importance in this context is the inhalation exposure to brake wear dust emitted from the vehicle and entrained in ambient air Due to the high heat generated during braking much of the surface asbestos is converted to forsterite a nonfibrous material Thus both forsterite and short length chrysotile asbestos are present in brake wear debris While the toxicity of chrysotile asbestos is well documented the health risk associated with forsterite exposure is not well studied although evidence suggests that both forsterite and brake lining dust have a cytotoxic effect The percentage of brake wear mass that becomes airborne has been reported as anywhere between 7 and .2,19-23 Mechanics performing brake replacements are especially susceptible to high exposures In 2010 brake wear accounted for 19 of California's on- road motor vehicle emissions inventory of PM particulate matter /1 0 ...mas based on the California Air Resources Board's CARB's model for estimating California's motor vehicle emissions For PM25 particulate matter /2.5 m brake wear accounted for 11 of the 2010 road motor vehicle emissions inventory Human exposure to brake- related asbestos emissions is likely to be the highest in urban and suburban environments compared to rural environment7s,8 Currently the proportion of ambient asbestos and the associated level of human exposure due to brake wear emissions in California are unknown Given that human exposure may be occurring and the fact that asbestos is a known human carcinogen an assessment was made to gauge the prevalence of asbestos use in automotive brake applications The purpose of this study was to estimate the current level of asbestos use in the California road fleet of duty medium and heavy motor vehicles and evaluate the regulatory implications of the findings Hi MATERIALS AND METHODS Light and Medium Vehicles Vehicles were procured under CARB's 18th Vehicle Surveillance Program VSP18 program a test program routinely conducted for the purpose of assessing emission levels of duty and mediumduty vehicles representative of the road California fleet Under this program vehicles are randomly selected from a registered database maintained by the California Department of Motor Vehicles Selection of approximately 300 vehicles was based on stratified sampling by model year i.e. weighted by the number of vehicles still on the road The model year of the vehicles sampled ranged from 1989 to 2006 and sampling was terminated in July of 2008. The sampling area encompassed an approximate 50 mile radius from the CARB El Monte office located roughly ten miles east of downtown Los Angeles This area includes all of Los Angeles County Orange County and portions of neighboring counties which are likely to be representative of suburban populations in southern California Vehicle selection is also presumed to include approximate representation across all income levels all manufacturers all models and targeted vehicle classes However consideration of potential biases in this study is given in a later section Sampling of these vehicles was halted after 137 vehicles when this subsample of vehicles was not statistically different at p 0/.05 from the target fleet of 300 with respect to model year p = 0.069 t = 2.04 df= 32 and manufacturer p = 0.403 t = 2.03 df = 7 based on a paired sample tailed test using the arcsine root transformation Although not statistically significantly different the mean model year age for the target fleet was slightly lower than our sample fleet 1996 versus 1999 with our sample fleet distribution skewed slightly more toward newer model vehicles Replacement of brake linings for the light- and medium vehicles was performed by certified CARB auto mechanics Brake lining samples were bagged and labeled with coded vehicle identifiers The following samples of brake lining were collected a the two inner disk linings from the front axle and b the two inner disk linings from the rear axle or in the case of drum brakes the two primary drum linings from the rear axle One front and one rear lining from each vehicle was sent the California Department of Public Health Environmental Health Laboratory EHL for asbestos analysis and the other set was retained as back As part of the vehicle procurement protocol conducted under the VSP18 program the owner was given a questionnaire to assess use condition and integrity of the vehicle Questions on household income and where vehicle repairs were typically conducted were also asked Vehicle owners who agreed to participate in the program were asked if they wanted their brakes replaced at no cost Regarding the replacement of brake linings in particular the vehicle owner was also asked if the front and rear brake linings on their vehicle were ever replaced and if so how long ago The answer to this question was intended to assist in the determination of whether the linings on the vehicle were the original linings installed on the vehicle at the time of purchase or if they were aftermarket linings This distinction was considered important because communications with automotive trade groups and manufac- turers strongly suggested that both U.S. and foreign auto manufacturers were no longer selling new vehicles equipped with brake linings containing asbestos A typical vehicle is likely to have its brake linings replaced anywhere from 4 to 8 times during its lifetime and in many cases with the use of aftermarket brake linings i.e. non OEM Heavy Vehicles The sampling of heavy vehicles was initiated in November 2008 and terminated in October 2009. The combined fleet of 54 heavy vehicles consisted of haul tractors haul trailers delivery vehicles motor homes dump trucks and buses Due to the large size and mass of heavy vehicle brake linings two- to inch square pieces were removed for analysis The sampled pieces 1345 dx doi org es202667di es2067di Environ Sci Technol 2012 46 1344-1351 Environmental Science & Technology 3 Figure 1, Images for subsample from brake linings showing a sampled drum brake lining b sampled disk brake lining c 6.3 stereozoom microscope image of subsample from drum brake lining and d 32 stereozoom microscope image of drum brake subsample showing fibious asbestos 50 ...mfrom the outer surface were bagged for transport and labeled with appropriate identifiers Thirty heavy vehicles were obtained from one repair shop in the Los Angeles area alongside a major California highway In all but two vehicles both the steer and drive axle brake linings were sampled Twelve samples were obtained a from trailer repair facility located in the Los Angeles suburb of Compton Samples collected from this facility consisted of stockpiled linings with no associated vehicle information other than the fact they were removed from line- haul trailers Linings from this stockpile were arbitrarily selected with the only criterion being a composition visually different from all others for example based on presence or absence of copper particles or visually different fibers Five samples were obtained from a repair shop at French Camp a community located near the city of Stockton and one additional sample was from a bus owned by a school district in Anaheim a city in Orange County Asbestos Analysis Asbestos analysis was conducted by EHL which has state facilities for identification of the following species of asbestos chrysotile actinolite tremolite crocidolite anthophyllite and amosite A screening procedure was developed based on established National Institute for Occupational Safety and Health NIOSH methodology which allowed for the qualitative identification presence or absence of chrysotile asbestos the most common asbestos mineral used in automotive brake linings All brake linings were qualitatively screened for asbestos using techniques specified in NIOSH Method 9002 which uses power stereozoom microscopy and polarized light microscopy PLM and has a detection limit of % asbestos content For light- and medium vehicles samples of each brake lining were prepared by breaking off pieces of the brake lining in a ventilation hood with the use of a hammer and awl Figure la and b For heavy vehicles this was not necessary since these samples were already removed from the backing of the brake lining All brake lining samples were then inspected under the stereozoom microscope Using a scalpel and forceps brake material was removed from the brake lining For the light- and medium vehicle brake linings containing asbestos brake material was removed from three locations in the following manner a by scraping from top to bottom along the sectional edge referred to as cross section b by scraping the outer frictional surface referred to as outer surface and c by scraping the inside surface of a piece broken off from the bottom of the brake lining referred to as the subsurface sample Analysis of these brake lining subsamples was performed in order to account for any heterogeneity in the spatial distribution of asbestos the presence of wear dust and the thermochemical transformation of asbestos Brake lining samples were placed in 1.550 refractive index Cargille oil on a slide with a coverslip PLM was used to characterize the fibers in the brake material with respect to the following key optical properties fiber morphology color under plane polarized light extinction angle under crossed polars sign of elongation using a full wave plate and birefringence as measured by dispersion staining Figure 2 If any fibers were positive for chrysotile the sample was ashed in a muffle furnace at 500 C for 24 h to remove the interfering organic matrix thereby facilitating improved asbestos identification and quantitation without denaturing the asbestos The asbestos content was determined by 1346 dx doi org | es202667d Environ Sci Technol 2012 46 1344-1351 Environmental Science & Technology 100um | 100um 100um b Figure 2. 100 PLM analysis of chrysotile asbestos subsampled from a 1997 Oldsmobile Silhouette drum brake lining a Positive sign of elongation under crossed polarizers with full wave plate b Characteristic dispersion staining colors Table 1. Summary Data for Light Medium and Heavy Vehicles Sampled vehicle type duty + mediumduty heavy line haul heavy city delivery heavy motor home no vehicles 137 13 10 7 average model year 1999 2004 1999 2001 average odometer miles 100 390 386 070 165 571 58235 58235 average GVWR lbs 4856 49 881 22 629 16936 16936 no axles sampled 274 27 21 14 no samples analyzed 274 33 36 24 no vehicles with asbestos 4 0 0 0 heavy bus 3 1998 313 852 38667 38667 4 8 0 heavy trailer 12 c - 12 12 o heavy other 9 1999 132 205 38 289 23 35 o heavy total 54 2001 219 373 32 554 101 148 0 = a GVWR gross vehicle weight rating defined as the maximum allowable total weight of a road vehicle or trailer carrying full load inclusive of vehicle weight fuel passengers cargo and trailer weight All brake linings with asbestos were rear drum brakes Trailer brake linings taken from a stockpile at a trailer repair facility and with each lacking associated vehicle information These assumed to originate from different axles based on differences in visual appearance 1.e. visual composition measuring the weight percent asbestos in the ash correcting for the amount of matrix removed and then calculating the implied percentage in the original brake RESULTS RESULTA S ND DISCUSSION Fleet Characteristics Characteristics of the vehicle fleet sampled are given in Table 1. In total 422 brake lining samples from light- medium- and heavy vehicles were analyzed for asbestos Of the 137 light- and medium vehicles sampled the average model year was 1999 with an average odometer of 100 390 miles and an average weight of 4856 lbs gross vehicle rate weighting GVWR which is defined as the actual vehicle weight plus its maximum allowable load Of this sample fleet only four vehicles had brake linings that contained asbestos which in all cases was identified as chrysotile asbestos The heavy fleet consisted of six vehicle categories representing various specialties of use Of the 42 vehicles for which vehicle information was available the average model year was 2001 the average odometer reading was 219 373 miles and the average weight 32 554 lbs GVWR The stockpiled brake linings from the heavy trailers were estimated by the owner to have been removed from vehicles over the 2005- 2008 time frame but no vehicle information was available for these samples No asbestos was found in any of the heavy duty brakes that were sampled Asbestos is used primarily in drum brakes though based searches have indicated that containing disk brakes are 1347 dx doi org es202667d | Environ Sci Technol 2012 46 1344-1351 Environmental Science & Technology Table 2. Asbestos Content and Vehicle Description in Brake Lining Samples with Asbestos vehicle no 7Rb model year 1997 vehicle information mfr Oldsmobile model Silhouette sample location on lining cross section outer surface subsurface mean = sample information wt % asbestos collection date 26 1/23/07 23 32 27 a_nalysis date 6/7/07 9/9/08 9/9/08 edge coded FASA 76 1989 Cadillac Coupe DeVille cross section outer surface subsurface mean = 3223 11/5/07 12/24/07 no edge code 3223 9/9/08 3223 9/9/08 25 116 1990 Ford Thunderbird cross section outer surface subsurface mean = 2233 3/28/08 4/23/08 FASA 2233 9/9/08 2233 9/9/08 2233 140 1998 Toyota 4 Runner cross section outer surface 33 7/11/08 7/28/09 FASA 25 9/9/08 subsurface 29 mean = 29 9/9/08 Grand Mean = 27.5 Vehicles procured under Surveillance Program No. 18 Project No. 2S06C1 and Project No. 2R0609 An R after the vehicle no indicates that the vehicle was rejected from the study due to excessive mechanical problems See text for details regarding the methods and location from which samples were taken The edge code is an identification marking stamped on the edge of the brake lining available on the market The four vehicles found with asbestos in this study were all equipped with front disk and rear drum brakes with asbestos present only in the drum brakes Currently the majority of light- and medium vehicles have disk brakes on all four wheels Of the light- and mediumduty vehicles we sampled 60 employed only disk brakes with the remainder utilizing front disk brakes and rear drum brakes The current study should be viewed as a snapshot in time conducted over a relatively short period of only 18 months for the light- and medium fleet beginning January 2007 and 12 months for the heavy fleet beginning June 2008 The heavy trailer brake linings were estimated to have been removed from vehicles over the 2005-2008 time frame but with no associated vehicle information available Thus caution must be exercised in the interpretation of these data relative to past or future prevalence of asbestos in the road vehicle population Sample Bias Five possible sources of bias in the light- and medium vehicle populations sampled include a overrepresentation of cost vehicles resulting from the offer of a free brake lining replacement a and free loaner vehicle b representation of high mileage vehicles also resulting from the offer of a free brake lining replacement anda free loaner vehicle c representation of wheel drive vehicles resulting from limitations in dynamometer emissions testing d representation of high vehicles from possible owner concern of vehicle damage and e geographic variation resulting in either an representation or representation in the supply and thus use of specific aftermarket brake linings With particular respect to geographical representation the nearness of a brake repair facility to particular manufacturers and distributors of brake linings could bias the brands of brakes sold into that local market and sold to a particular repair shop Investigation into the brake lining edge codes indicate that three of the four brake linings containing asbestos originated from the same Canadian manufacturer with Canada being one of the largest producers of asbestos in the world the manufacturer of the fourth lining is unknown due to an illegible edge code Since the study described herein was conducted in southern California there exists the possibility that the incidence of asbestos linings may be higher in northern California and the more northern U.S. states since to our knowledge no brake manufacturer in the U.S. produces containing brake linings Similar to the light- and medium population of vehicles sampled there was a geographic bias in the heavy vehicles sampled namely a bias toward southern California In addition the heavy vehicles were serviced on site at their respective facility thus requiring the selection of facilities that were willing to coordinate with CARB staff Besides resulting in additional logistical complexities this also resulted in the inability to collect a random sample A sampling issue and likely bias specific to the stockpile of heavy trailer brake linings was selection of friction material samples based solely on visual differences resulting in sampling that was not random Asbestos Content Analysis of the three subsamples from each of the four duty and medium vehicles with asbestos brake linings are reported in Table 2 and include mean values of the relative asbestos contents for each vehicle These means ranged from 25 to 30 wt % with a mean of 27.5 wt % n = 4 A way ANOVA analysis of variance was conducted to assess the presence of any statistically significant differences p 0/.05 between asbestos brake lining content of the four vehicles as well as any differences between the three locations where the brake subsamples were taken n = 12 No statistically significant differences F3,6 = 1.76 p = 252 were found among the four vehicles with respect to asbestos content in the brake lining samples However there was a statistically significant difference F2,6 = 7.47 p = 0.023 found among the three locations from which subsamples were taken A posthoc 1348 dx doi org es2026|6En7 vid ron Sci Technol 2012 46 1344-1351 Environmental Science & Technology Table 3. Characteristics of the Four Vehicles with Asbestos Brake Linings vehicle no 7Rb model year odometer miles 1997 101947 GVWR lbs 5357 comments damage stains on door 4 broken items outside 13 paint scratches one deep metal 2 dents dings one chipped paint approximately 40 items indicated on damage diagram one metal scratch mechanical leaking radiator approximately 1300 in repairs conducted by dealership noise when turning sharp left or right household income 35-50K other vehicle failed Smog Check on the first test dirty oil maintenance typically conducted by service station 76 1989 167 482 4507 damage carpet stains and tears rips on passenger door broken light on driver's side steering wheel damage some dents on roof cracked windshield approximately 20 items total on damage diagram mechanical driver's side window has operational problems repaired 2 vacuum lines and O2 sensor household income 50-70K other failed two emission tests for nitrogen oxides vehicle maintenance typically conducted by service station owner rarely follows recommended maintenance schedule carpet 116 1990 180 541 4885 damage view mirror fell off driver's seat leans to left weak AC brakes squeak stains on seat and approximately 41 items total on damage diagram mechanical two drums replaced rear spring kit tow wheel cylinder muffler was repaired had oil leak with puddle on ground household income 90K 140 1998 465 we 5250 typically other failed one emission test for nitrogen oxides and hydrocarbons low coolant level in reservoir maintenance conducted by service station damage front windshield pitted approximately 29 items total on damage diagram mechanical master cylinder rear right axle seal replaced household income declined other maintenance typically conducted by dealership or owner Vehicles procured under CARB's Light Vehicle Surveillance Program No. 18. R after the vehicle no indicates that the vehicle was rejected from the study due to the need for excessive mechanical repairs GVWR = gross vehicle weight rating defined as the maximum allowable total weight of a road vehicle or trailer carrying a full load inclusive of vehicle weight fuel passengers cargo and trailer weight Tukey HSD honestly significant difference test indicated that the section samples contained significantly more asbestos than the outer surface samples with the subsurface sample asbestos content lying between these extremes The outer surface was expected to have the least amount of asbestos due to the conversion of the asbestos to forsterite through frictional heating which creates a relatively thin asbestos layer Figure 1c 1d However we should note that the value of 0.023 indicates only a weak trend due in large part to the limited sample size These results indicate that care should be taken in sampling brake linings for asbestos content by avoiding sample contamination from the brake dust and also by avoiding sampling any subsurface forsterite resulting from frictional heat The average approximate asbestos content of 27.5 wt % found in this study can be compared to previous estimates of 20-60 wt .22,26-29 However only a very small fraction of the original asbestos survives the thermal temperatures experienced during a braking event due to the conversion to forsterite The percentages by weight of airborne asbestos found in brake wear dust worn from asbestos brake linings are typically less than 1.0 wt % ranging from 0.02 to 0.50 wt 21,22,30 Variability in these estimates is likely due to differences in the asbestos contents of the brake linings as well as differences in the driving cycles or the number and intensity of stopping events and the sampling methodology used to collect and size the asbestos fibers Such variability exacerbates any attempt to estimate the contribution of motor vehicle brake wear emissions to the ambient air concentration of asbestos Characteristics of Vehicles with Asbestos In our study four out of the 137 vehicles sampled 1.e. 2.9 of the lightand medium fleet had brake linings with asbestos Table 3 presents characteristics of the four vehicles found to have asbestos brakes Two clearly distinguishing factors among the four vehicles determined to have containing brake friction material were high mileages and earlier model years In particular the average model year of the four vehicles was 1994 compared to the sample fleet average of 1999. Odometer mileages of the four vehicles averaged 148 000 miles compared to 000 miles for the total sample fleet average From the perspective of mechanical condition one of the four vehicles required so many repairs totaling approximately 1300 that it was ultimately rejected from the program and never tested for tailpipe emissions Another metric of assessing the mechanical condition of the vehicle is the number of VSP18 program emission tests that it fails Of the three vehicles tested one failed two tests and two of the vehicles failed one test A test engineer for the program qualitatively estimated that 60 or more of the vehicles do not fail any of the emission tests Regarding vehicle maintenance three of the four owners had their maintenance performed at a service station or independent garage rather than a dealership For the fourth vehicle maintenance was conducted by the owner or a dealership Maintenance and repair costs at dealerships tend to be significantly higher than service stations or independent repair facilities In addition asbestos linings are less expensive linings linings than nonasbestos 31 and so the owner may have- requested expensive brakes In summary these four vehicles can be characterized as early model mileage and mechanically compromised with their owners tending to minimize the cost of maintenance and repairs Based on high mileage and confirmation by vehicle owners all four vehicles with containing brakes were assumed to have had their brakes replaced at least once thereby indicating a high probability of an aftermarket source of the brake linings Although no single characteristic described above would likely serve to distinguish a vehicle with asbestos brake linings compared to one that does not the ensemble of characteristics nonetheless serves to typify those light- and medium 1349 dx doi org es20266es2067d1 7 End vir1 on Sci Technol 2012 46 1344-1351 Environmental Science & Technology vehicles that do have asbestos brake linings However this small sample size of four vehicles does warrant caution in extrapolating these results to a larger fleet These characteristics are not likely to be useful in predicting if a given vehicle will have asbestos brake linings since many vehicles may have the above traits but only a very few of those are likely to have containing brake linings The lack of containing brake linings in the heavyduty vehicles sampled may be due to the low sample size of 54 and the result of heavy brake specifications that preclude the use of asbestos There is also a possibility of some bias in the heavy brake samples collected since front tractor brake linings may be of identical composition to the rear tractor brake linings because they typically have the same specifications and are often replaced at the same time with the same brake linings The same is often true for trailer brakes when trailer brake linings are replaced all are typically changed at the same time There is also a sparse representation regarding the variety of use in the total fleet sampled with only three buses sampled and many other specialty vehicles not included Regulatory Implications In the mid to late 1980s brake lining manufacturers began to develop alternatives to asbestos motivated by litigation and the aforementioned asbestos bans in European countries and an imminent USEPA ban on asbestos use in friction products However following the ban enacted by the USEPA in 1989 and the court's subsequent reversal of that ban in 1991 auto manufacturers and the aftermarket brake lining industry continued to use asbestos In 1998 it was estimated that approximately 25ofthe duty and _ medium vehicles sold in the U.S. were equipped with OEM drum brakescontaining asbestos12 At the same time the aftermarket brake industry in the U.S. was reported as being approximately 10 times the size of the OEM market The consensus among automotive trade associations is that no U.S. automotive manufacturers currently use asbestos in OEM brakes and that no foreign vehicle manufacturers are selling brakes with asbestos in the U.S. market However without a federal ban aftermarket providers of brake linings throughout the U.S. are likely to continue to include asbestoscontaining linings within the mix of their product offerings The future trend nationally in the use of asbestos is likely to depend on availability cost advantage and the likelihood of a ban on importation and sales Although our study identified only four vehicles with containing brake linings all four were high mileage vehicles with a high likelihood of aftermarket brake linings with three of four having linings from the same Canadian aftermarket manufacturer In late 2010 after completion of our study California signed into law Senate Bill SB 346 which specifies a de mimimis level of 0.1 by weight of toxics in motor vehicle brake friction materials including asbestiformfibers as well as compoofucandmdiusm chromium and mercury This regulation takes effect on Januar1y 2014 and essentially bans asbestos and these other toxic compounds in brake lining formulations for vehicles sold in the state At this time California appears to be the only state to ban asbestos use in automotive brake linings Our sampling program found that only % of light- and medium vehicles and % of heavy vehicles had brake linings with asbestos supporting the contention that the U.S. is currently experiencing a downward trend in the use of asbestos in brake linings Although there have been repeated calls by national and international organizations to implement a worldwide ban on asbestos products most recently by the Collegium Ramazzini a nonpartisan international academic society that examines public health issues no U.S. or worldwide ban appears forthcoming Thus the monitoring of asbestos use and other toxic materials in brake linings is a prudent course of action In this context ongoing sampling programs will be required to assess the prevalence of asbestos and other toxic substances present in the brake dust released from the operation of road vehicles and adherence to state regulation M AUTHOR INFORMATION Corresponding Author Phone 626-350-6469 fax 626-459-4480 mail Irao@arb.ca gov > oa HM ACKNOWLEDGMENTS John Urkov Raphael Susnowitz Tom Valencia Don Chernich Brian Weitz Jerry Ho and Mike O'Connor were very supportive of this project and assisted with funding sample collection and logistics Ron Haste served as the backup engineer for this program Marco Diaz and Carl Law were very helpful in performing the brake lining replacement The following staff provided excellent field support for the collection of heavy vehicle brake samples Bob Torres Mark Burnitzki Gene Sato Manny Arevalos Javier Chavez Esther Gonzales William Interiano John O'Cain Gary Okimoto and Luis Ordonez Daimon Pon from the California Department of Public Health provided custom coded sample labels M REFERENCES . 1 Virta R. L. Worldwide Asbestos Supply and Consumption Trends from 1900 through 2003 U.S. Geological Survey Circular 1298 United States Geological Survey Reston VA 2006 pubs usgs.gov/ c1298.pdf accessed April 6 2011 2 Blau P. J. Compositions Functions And Testing of Friction Brake Materials and Their Additives ORNL Oak Ridge National Laboratory Oak Ridge TN 2001 //www.ornl gov 112956.pdf accessed April 6 2011 3 Moore P. Chrysotile in crisis Industrial Minerals Magazine April 2004 56-61 4 Castleman B Camarota L. A Fritsch A .; Mazzocchi S. Crawley R. G. The hazards of asbestos for brake mechanics Public Health Rep 1975 90 3 254 256 5 Lemen R. A. Asbestos in brakes exposure and risk of disease Am J. Ind Med 2004 45 3 229 237 6 Welch L. S. Asbestos exposure causes mesothelioma but not this asbestos exposure An amicus brief to the Michigan Supreme Court Int J. Occup Environ Health 2007 13 3 318 327 7 Lim H KimJ. Y Sakai K Hisanaga N. Airborne asbestos and asbestos fiber concentrations in occupational environments in Korea Ind Health 2004 41 171 178 8 Kohyama N. Airborne asbestos levels in occupational environments in Japan In Occupational Exposure to Mineral Fibers IARC Scientific Publications No.90 Bignon J. Peto J. Saracci R. Eds International Agency for Research on Cancer Lyon 1989 pp 262-276 9 Kazan L Current asbestos bans and restrictions 2011 International Ban Asbestos Secratariat http.//ibasecretariat org alpha_ban_list.php accessed October 6 2011 10 Asbestos Manufacture importation processing and distribu- tion in commerce prohibition Code of Federal Regulations Part 763 Title 40 Subpart I Sections 762.160 - 763 179 1989 1350 dx doi org es2026|6En7 vird on Sci Technol 2012 46 1344-1351 Environmental Science & Technology 11 Corrosion Proof Fittings et al Petitioners v the Environmental Protection Agency and William K. Reilly Administrator Respondents No. 89-4596 5th Cir Oct. 18 1991 12 The Friction Product and Materials Market 212 Business Communications Company Inc. Wellesley MA 1998 13 U.S. Environmental Protection Agency Release of draft brochure on current best practices to prevent asbestos exposure among brake and clutch repair workers Notice of availability Fed Regist 2006 71 164 50060 - 50062 14 Asbestos Still Lethal Legal - The Need to Better Protect the Health of American Workers and Their Families Subcommittee Hearing Statement of Barry Castleman Environmental Consultant Senate Health Education Labor and Pensions Committee Subcommittee on Employment and Workplace Safety Washington DC 2007 http help.senate.gov/mo/media/doc/Castleman.pdf accessed October 10 2011 15 Michaels D Monforton C. How litigation shapes the scientific literature asbestos and disease among automobile mechanics J. Law Policy 2007 5 3 1137 1169 16 Hazardous materials motor vehicle brake friction materials Senate Bill 346 Kehoe California Health and Safety Code Chapter 6.5 Division 20 Article 13.5 Sections 25250.50 - 25250.65 September 27 2010 http://e-lobbyist.com/gaits/view/62361 accessed May 24 2011 17 Os~-nubiO. Y. Gochfeld M Kipen H. M. Health effects of asbestos and nonasbestos fibers Environ Health Perspect 2000 108 Suppl 4 665-674 18 Detailed procedure for asbestos sampling and analysis - nonmandatory Code of Federal Regulations Part 1910 Title 29 Subpart Z Section 1910.1001 Appendix B. 1996 http://www.osha.gov/pls/ owadisp.show_document accessed April 6 2011 19 Sanders P. G Xu N Dalka T. M Maricq M. M. Airborne brake wear debris Size distributions composition and a comparison of dynamometer and vehicle tests Environ Sci Technol 2003 37 18 4060-4069 20 Garg B. D Cadle S. H Mulawa P. A Groblicki P. .; Laroo C Parr G A Brake wear particulate matter emissions Environ Sci Technol 2000 34 21 4463 4469 21 Cha S Carter P Bradow R. L. Simulation of automobile brake wear dynamics and estimation of emissions SAE Tech Pap Ser 1983 SAE 831036 1-21 22 Williams R. L Muhlbaier J. L. Asbestos brake emissions Environ Res 1980 29 1 70-82 23 Sanders P G Dalka T. M Xu N Maricq M. M Basch R. H. Brake dynamometer measurement of airborne brake wear debris SAE Tech Pap Ser 2002 SAE 2002-01-1280 1-8 24 EMFAC2007 version 2.3 California Air Resources Board Sacramento CA 2006 http.//www.arb.ca.gov/msei/msei.htm accessed April 7 2011 25 Asbestos Bulk by PLM 9002. NIOSH Manual of Analytical Methods NIOSH Publication Number 2003-154 Third Supplement Center for Disease Control and Prevention Atlanta GA 2003 26 Morshed M. M. Haseeb A. S. Physical and chemical characteristics of commercially available brake shoe linings materials A comparative study J. Mater Process Tech 2004 155-156 1422- 1427 27 Saito T. Indirect estimation of asbestos concentration due to vehicles in particulate matter in the atmosphere and on roads by pyrolysis - gas chromatographyJ Anal Appl Pyrol 1995 32 177 178 28 Rowson D. M. The chrysotile content of the wear debris of brake linings Wear 1978 47 2 315-321 29 Wall S. Determination of Asbestos Content of Current Automotive Dry Friction Materials and the Potential Contribution of Asbestos to Particulate Matter Derived from Brake Wear Contract No. 01-333 Final Report California Air Resources Board Research Division Sacramento CA 2007 30 Jacko M. G DuCharme R. T Somers J. H. Brake and clutch emissions generated during vehicle operation SAE Tech Pap Ser 1973 SAE 730548 1-20 31 Asbestos Materials in the Automotive Maintenance and Repair Industry Guidance Note Chamber of Commerce and Industry Risk Solutions East Perth Australia 1999 32 Collegium Ramazzini Asbestos is still with us Repeat call for a universal ban Arch Environ Occup Health 2010 65 3 121-126 33 LaDou J Castleman B Frank A Gochfeld M Greenberg M Huff .; Joshi T. .; Landrigan P. .; Lemen .; Myers J. Soffritti M Soskolne C. L Takahashi .; Teitelbaum D. Terrac~-n~- B Watterson A. The case for a global ban on asbestos Environ Health Perspect 2010 118 7 897 901 What 1351 dx doi org | es20266En7 vird on Sci Technol 2012 46 1344-1351