Dear Dr. Gardner:
We are responding to Dr. Paustenbach’s 2,514 word response almost entirely devoted to one sentence of Dr. Egilman’s original letter: “Victor/Dana used crocidolite in gaskets until at least 1963, Borg Warner used crocidolite in transmission friction plates, Ford hygienists were aware of the use of amosite in brakes, Maremont used crocidolite during the Canadian asbestos strike, and Borg Warner admitted that it used crocidolite in brakes in one set of sworn interrogatories, and denied this in another.” The regular readers of this publication may wonder why so much ink is being spilled over what may seem to be a trivial issue: whether or not brake workers are exposed to amphibole (amosite, crocidolite or tremolite) asbestos-containing products when they repair or replace automobile parts including brake pads, clutches, gaskets, transmission bands, and mufflers.
Every year hundreds of automobile repair workers develop mesothelioma and some of them sue automobile parts manufacturers/sellers for compensation (Lemen, Citation2004). In fact, hundreds of millions (perhaps) billions of dollars are at stake.
In asbestos litigation generally, and in automobile cases in particular, many companies have concocted a “fiber type” defense (Welch, Citation2007; Egilman et al., Citation2011). While there are variations, the central feature of this defense is a claim that whichever fiber type was used in a particular company’s products has not been shown to cause mesothelioma. It is undisputed, outside courtrooms, that all fiber types cause lung cancer. Since chrysotile constituted 95% of the fiber used in the US, companies have developed a second line of defense: according to them tremolite found in chrysotile rather than the chrysotile itself is the major cause of mesothelioma in those exposed to chrysotile. Finally, they argue that although chrysotile itself can cause mesothelioma, this only occurs with massive exposure while tremolite and other amphiboles are far more potent. This argument is based on a misinterpretation of the Quebec Asbestos Mining Association studies and has been debunked (Egilman et al., Citation2003).
The “dispute,” which is designed to manufacture doubt over the relative toxicity of different fiber types, did not arise until regulation and litigation commenced in the late 1960s. The tremolite theory was first published in 1995 (McDonald and McDonald, Citation1995). As a result, asbestos product companies have poured more than fifty million dollars to fund “research” that will show that their products do not contain amphiboles (CitationEgilman et al., 2011). This explains the vehemence and surliness of the current exchange. This is not a dispute over science; it is a dispute that sounds like science. The actual subject matter is the compensation of injured workers, relatives and bystanders which has taken the form of a scientific dispute.
1. Tremolite content of Canadian chrysotile asbestos
Dr. Paustenbach concedes that chrysotile from Canadian mines used in friction products contained tremolite. Importantly, there is no evidence that <1% tremolite exposures are insufficient to cause mesothelioma, and Dr. Paustenbach does not cite any evidence for a No Observable Adverse Effect Level (NOAEL) for tremolite. At the current PEL, OSHA predicts that 3.4 workers per thousand will die from mesothelioma (OSHA, Citation1994). There are generally 2–6 lung cancer deaths per mesothelioma (McCormack et al., Citation2012).
Dr. Paustenbach claims Ford tested the tremolite content of its supplier’s chrysotile to reduce squeaks but Ford never manufactured brakes, and there is no evidence that anyone was aware of “trace” tremolite content or its relationship to squeaks in the early 1980s.
Ford used Transmission Electron Microscopy (TEM) to analyze filter samples as part of brake emissions testing (Anderson et al., Citation1973). The tremolite/anthophyllite trace detection problem was first described by Elems, Hodgson and Browne in a meeting of The Asbestos Research Council in 1984 (Asbestosis, Research, and Council, Citation1984). TEM cannot detect the tremolite content in bags of chrysotile fiber (Addison and Davies, Citation1990). For this reason Addison and Davies developed a chemical technique that destroyed chrysotile and left tremolite fibers intact (Addison and Davies, Citation1990). They found that when chrysotile samples were digested using the acid/base process, they were able to increase the detection limit by 10-fold when the samples were analyzed by either X-ray diffraction (XRD), IR analysis and scanning electron microscopy (SEM).
Dr. Paustenbach also cites Finley et al., in support of the inference that the Jeffrey Canadian Chrysotile mine was tremolite free. In turn, Finley et al. (Dr. Paustenbach was a co-author) cites Williams-Jones for this proposition (Williams-Jones et al., Citation2001; Finley et al., Citation2012). One of us (DE) contacted Williams-Jones to determine whether or not this was a correct interpretation of his findings. Williams-Jones replied that the assertion that his paper stood for the proposition that Jeffery mine chrysotile was “amphibole-free” is a “misrepresentation” of his findings:
“It really is frustrating to be misrepresented on this issue and this is not the first time. Our observations showed that the Jeffrey ore, i.e., the chrysotile, which was the target of the mining operations, was tremolite-free. However, we also determined that tremolite crystallized at the contact between dyke rocks and the serpentinites that host the ore. In many places, this tremolite was in close proximity to the chrysotile ore and had been mixed with it during mining. One of the conclusions of our paper was that contamination of the chrysotile ore with this tremolite could be minimized with careful mining practices. We also suggested chemical methods for predicting and thereby avoiding potential tremolite contamination.” [Emphasis added] (Personal communication with A.E. Williams-Jones, 5/1/2012).
2. Regarding exposures from arcing (grinding) and replacing brakes: Dr. Longo of MAS has shared his data on tremolite content in brakes; tremolite is clearly present. A summary of the MAS chrysotile/tremolite automobile part research follows:
Over the last 10 years, MAS has analyzed a number of chrysotile-containing brake friction pads and compressed sheet gaskets using standard PLM analysis, as recommended by the EPA, which is the current industry standard for commercial laboratories around the country that routinely perform this analysis (EPA, Citation1993). The typical concentration range of asbestos-containing brake shoes that MAS has tested is 25–35% chrysotile, and the compressed sheet gaskets contained between 55 and 80% chrysotile when analyzed by PLM. Of the many brake and gasket samples analyzed at MAS by PLM, no trace amounts of amphiboles were ever detected using this method.
The EPA-PLM method has a typical analytical sensitivity of approximately 0.5 weight percent. Therefore, any type of asbestos that may be present below this concentration will not be detected using this method. An example of this detection problem with PLM is the trace amphibole content (tremolite and or anthophyllite) of chrysotile. Tremolite at trace levels (<0.5%) in chrysotile would render it as non-detectable using standard PLM technology.
Addison and Davis did not use analytical transmission electron microscopy (ATEM) that would have further increased their amphibole detection limit in the chrysotile samples by another factor of 1000.
MAS has used an enhanced Addison and Davis method to analyze a number of chrysotile-containing brake samples and sheet gaskets from various manufacturers. By increasing the detection limit using ATEM, MAS has been able to quantitatively measure tremolite/anthophyllite in each of the samples tested.
Besides brake and gasket bulk samples, MAS has also used the enhanced Addison and Davis method on a limited number of air sample filters collected during MAS work practice studies involving the grinding of brake shoes.
Brakes
Bulk samples of chrysotile-containing Bendix (4 sets), Chrysler (2 sets), Wagner (1 set) and Wearever (1 set) brake shoes were analyzed by ATEM after the chrysotile was removed by the Addison and Davis digestion method. Each of the brake shoe friction material MAS tested was found to contain trace weight amounts of tremolite fibers and bundles. The range of tremolite found was 0.0009–0.174%. The results for the analysis are shown in .
Table 1. Concentration of tremolite in chrysotile-containing brake shoes.
MAS has performed a number of work practice studies where air samples were collected during the sanding, filing and grinding of chrysotile-containing brake shoe friction material. This involved the collection of a large number of air samples that were analyzed by PCM and TEM. None of these air samples showed any presence of tremolite; only chrysotile fibers were detected. This is not surprising considering that MAS research shows that the amount of tremolite present in chrysotile brake material tested is at trace levels causing the air sample analysis to be overwhelmed by the sheer number of chrysotile fibers as compared to the amount of tremolite fibers that could possibly be on the collected air filter samples.
To determine if any trace amounts of tremolite present in the brake shoe material was released in measurable amounts, two air samples that were previously collected during arc grinding and hand grinding studies (one for each study) were further analyzed by the Addison and Davis/ATEM method. The analysis showed that both air samples had tremolite fiber concentrations of 0.051–0.22 fibers/cc greater than 5 micrometers in size. The results of the study are shown in .
Table 2. Airborne tremolite fibers in chrysotile-containing brake grinding studies.
This Addison and Davis/ATEM method data indicates that not only were brake mechanics being exposed to high levels of chrysotile during these types of typical work activities, but they were also being exposed to significant levels (above current PEL if work was performed for 40 h) of tremolite. While this is a small sample set, MAS found the tremolite evidence very compelling since every sample tested was positive for tremolite.
The MAS data for the detection of amphiboles in chrysotile containing brakes clearly demonstrates that Dr. Paustenbach’s statements that workers are not exposed to significant levels of airborne amphiboles when using these products are in error. The studies that Dr. Paustenbach reference did not use analytical techniques designed to make assess these exposures.
Dr. Paustenbach gratuitously adds a claim that the OSHA 5 micron counting rule cut off is of biologic relevance. The “scientific basis” of the 5 micron “cut off” is the fact that there was too much “intra-observer variability” at shorter lengths because the shorter fibers were too numerous to count reliably (NIOSH, Citation1972). This “cut off” had nothing to do with biologic activity. In Gardner’s textbook, Bernstein stated that “Historically, a fiber has been defined as a particle that has a length >5 µm, a width <3 µm, and an aspect ratio > 3:1. This definition was not based upon any criteria relating to health but, rather, was related to facilitating the counting of fiber using light microscopy” (Gardner, Citation2006) Suzuki et al. examined 168 mesothelioma cases and found that the majority of fibers (93%) were short (<5 μm) (89%) and thin (<0.25 μm) (93%) chrysotile fibers (Suzuki et al., Citation2005). Suzuki found that chrysotile was present in 70 of the 74 cases (94.6%) and most importantly, he found that chrysotile was the only fiber detected in 55 of the 74 cases (74.3%) (Suzuki et al., Citation2005). The exclusive presence of a particular fiber type (chrysotile) in the pleura (the target organ) of a person who developed mesothelioma is overwhelming evidence that that fiber type (short chrysotile) caused the mesothelioma (Suzuki et al., Citation2005).
3. Victor/Dana use of crocidolite
We thank Dr. Paustenbach for pointing out this error. Victor gaskets were made from amosite and chrysotile. Victor claims they eliminated the use of amosite in 1963 (Dana, Citation2012). The fact that Victor gaskets contained amosite supports our argument that automobile repair workers can be exposed to amphibole fibers.
4. Borg Warner’s use of crocidolite in brakes
Dr. Paustenbach claims, without presenting any evidence, that Borg Warner’s 1992 Sworn Answers to Interrogatories stating that they used crocidolite in brakes was an “error,” and that Borg Warner’s lawyer simply “confused” crocidolite with chrysotile. He claims that these lawyers then “corrected” this “error” three years later in another set of (not amended) Answers to Interrogatories. Borg-Warner did not claim that their lawyer made an error in the earlier admission when they changed their response in subsequent Interrogatory answers. They merely stated that the brakes contained chrysotile. They did not deny that they ever contained crocidolite.
While we neither claim to understand the mentality or motives, nor question the knowledge of the lawyer who wrote these Answers to Interrogatories, we feel it is highly presumptive to characterize this as an error without any evidence or analysis indicating that it is an error. However, it is important to note that the crocidolite/chrysotile fiber type defense was well-established by 1992 and should have been known to all asbestos defense lawyers. Dr. Paustenbach claims that Borg Warner’s lawyers were “less sensitive to the importance of carefully documenting the differences” between these fiber types at this time. However, conflation of crocidolite for chrysotile certainly does not explain Borg Warner’s Interrogatory answers which unambiguously state that “Borg Warner disc brake pads incorporated both crocidolite (blue) and chrysotile (serpentene) [sic] asbestos fibers.” [Emphasis added] Since Borg-Warner asserted that the brakes contained both fiber types and named both fiber types and specified the physical structure of chrysotile presumably to distinguish it from crocidolite, it is clear that the lawyers did not mistakenly conflate crocidolite for chrysotile. Finally, the representation that Borg-Warner brakes contained crocidolite is an admission against interest since crocidolite is universally acknowledged to be a cause of mesothelioma. An admission against interest is considered so reliable that it is an exception to the hearsay rule of legal evidence. Dr. Paustenbach discounts this documentation as a “confused error.” One of the authors (DE) has been cross examined by the lawyer who signed these Answers to Interrogatories and found her to be quite competent. She did not demonstrate confusion about the differences between crocidolite or chrysotile. Dr. Paustenbach claims that he is “not aware of any information indicating that crocidolite has been used to manufacture automobile brakes.” The Borg Warner and Maremont Answers to Interrogatories (see below) certainly qualify as “information” that crocidolite has been used in automobile brakes.
5. Borg Warner’s use of crocidolite in transmission friction plates
Dr. Paustenbach agrees that friction plates contained asbestos, and that no one has assessed exposure from crocidolite bands. He then speculates about the importance of this exposure. Dr. Paustenbach conflates “significant” exposures with TLV levels, which varied from >30 fibers per cc to.1 fiber/cc during the relevant time period. Physicians tend to equate “significant” with “enough to cause mesothelioma and kill you.” Dr. Paustenbach has written that crocidolite is the most potent fiber and is 500 times more potent than chrysotile (Finley et al., Citation2012).
6. Ford’s use of amosite in brakes
Dr. Paustenbach calls our quotation of Ford’s industrial hygienists’ acknowledgment of the historical (pre-1968) presence of amosite in brakes “deceptively misleading, and fundamentally an inaccurate characterization of the facts.” Since he agrees that Dr. Egilman accurately reported that Hickish and Knight acknowledged the presence of amosite in Ford brakes, we are baffled by his characterization that Dr. Egilman and others were “deceptive” and provided “fundamentally an inaccurate characterization of the facts.” This is a serious accusation based on pure speculation. Dr. Paustenbach theorizes, without evidence, that the Ford industrial hygienists in charge of brake studies recognized that the amosite statement was an “error” and was “obviously... not correct” and the authors or “peer reviewers” recognized this and removed the words. Dr. Paustenbach also speculates that “someone” could assert the change was made to mislead readers about the hazards of brakes. That “someone” is not us. Hickish and Knight had no reason to misrepresent the presence of amosite in brakes in 1970 since some argued that amosite was not a proven cause of mesothelioma until 1972.
We do not presume to know the mentality, motives, or circumstances of the authors, nor can Dr. Paustenbach know DE’s. There is no evidence that the amosite statement was removed for any reason other than the fact that the history of the content of brakes was not relevant to a paper reporting exposures from a chrysotile brakes. There is no evidence that the 1970 Hickish and Knight paper, which was published as part of a symposium proceeding and did not have the amosite statement, was ever peer-reviewed. We note that Hickish and Knight omitted the following research report language from their published paper:
“It would also be desirable to include in Service manuals, a general instruction that inhalation of dust during brake cleaning should be minimized, and if practical alternative methods, which would produce less dust, can be devised, their use should be recommended.”
We do not believe that this language was removed because it was bad advice or because of “peer reviewer comments.” Citing three papers, Dr. Paustenbach writes: “no amosite was ever measured in literally dozens and dozens of bulk samples of brakes collected from vehicles of the 1940s–1980s, or in the perhaps more than two hundred air samples collected in which the presence of amphiboles was investigated (Sheehy et al., 1989; Blake et al., 2003; Madl et al., 2008)”. Sheehy et al. found amosite in seven samples, and they corrected for background contamination. Madl et al., was a study of exposures during brake box opening. The paper mentions one refurbished Jeep brake, the design of which was unchanged from 1947 to 1967. It appears the brakes were refurbished in the last 20 years. Blake et al. studied four automobiles which were fitted with new replacement chrysotile-containing brake shoes. Therefore, none of the cited studies examined any brakes manufactured between 1947 and 1980.
As Popper noted, finding a thousand white swans does not prove that all swans are white, but finding a single black swan proves that they are not. We do not believe that amosite has been used in brakes in the past 30 years (we have no evidence either way). Therefore we would not expect that brake exposure studies in this century on brakes manufactured after 1980 would find amosite. This does not mean brakes never contained amosite.
7. Maremont’s use of crocidolite in brakes
As cited in Dr. Egilman’s initial letter, Jonathan Sherr, a former Maremont employee, stated in deposition that “Blue crocidolite fiber was supplied by Ural Asbestos” to Maremont. Dr. Paustenbach suggests that Maremont invented this when it restated these facts in Answers to Interrogatories, by implying that only “pure chrysotile is found throughout the Ural Region (Uralbest) in Russia.” Dr. Paustenbach cites three studies from this century for the proposition that Uralbest never sold crocidolite, including one by Kashansky et al. (2001). We wrote Dr. Kashanskiy and he reported that:
“…Near Alapaevsk City [Ural Region] extracted crocidolite-asbestos from 1953 till 1994 year. …. The last enterprise for production of amphibole asbestos in Russia was closed in 1997.” [Emphasis added]
Dr. Paustenbach is correct that Russia no longer exports crocidolite but they did so when Maremont brakes contained crocidolite in the 1940s and fifties.
The human lung is the most effective asbestos filter material because lung tissue can reveal and reflect exposures that occurred over a 90-year time frame. As we noted in our letter, Dr. Roggli has found elevated levels of tremolite in brake repair workers with no other source of exposure. This is the best evidence that work with brakes results in deposition of tremolite in human lungs. He also found elevated levels of amosite in five of ten brake workers “whose only known exposure was to brake dust” (Butnor et al., Citation2003). One of these workers’ lungs was primarily contaminated with crocidolite (Butnor et al., Citation2003). This is further evidence that work with brakes and/or other automobile parts can cause mesothelioma. Finding crocidolite or amosite in the lungs of automobile repair workers is not evidence that they had exposures to products other than brakes or other automobile parts.
William E. Longo PhD President of Materials Analytical Services LLC.
David Egilman MD, MPH Clinical Associate Professor Department of Family Medicine Brown University.
Declaration of interest
Drs. Egilman and Longo have served as expert witnesses in asbestos litigation at the request of workers injured by exposure to asbestos products and companies that manufactured asbestos-containing products. MAS funded the studies presented in this letter. MAS has conducted other studies on asbestos products that were funded by lawyers representing workers injured by exposure to asbestos products and by companies that manufactured asbestos-containing products.
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References
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