Document bBG6MLkvgvepXvXb07dM6pnog

FILE NAME: Z< DATE: DOC#: Z< DOCUMENT DESCRIPTION >ZZZZZZ sDZDZZ Ann. Ocwp. Hyg.) 2016) Vol. 60) No. 4) 528-530 dOl: 10.1093/annhyg/mewO 15 ( " ' , /~ ,1 LETTER TO THE EDITOR Editorial Note. Letters to the Ed,tor are peer relllCwed to ensure that the argumellts are reasonable and clearly expressed. HoweveJ; letters may express a parliwlar optnion rather than a balanced mterpretatwH. AuthOl s ofpapers wmmented on are mVlled to reply, but lIelther lhe Journal Hor pcer reviewers should be assumed to support tlte argumwts lIIade. Thinking about Occupation-Response and Exposure-Response Relationships: Vehicle Mechanics, Chrysotile, and Mesothelioma I(ay Teschke School ofPopulatlon and Pubhc Health, University ofBnbsh Colombia, 2206 East Mall, Vancouver, Rntish Columlnd V6T lZ3, C.,oad. E-mail kay.teschke@lubcca Submitted 16 December 20lS; revIsed 20 February 2016; revised version accepted lO March 2016. The 2015 paper by Garabrant et al. (2016)) 1he first question addresses the statement at the Mesothelioma among Motor Vehicle Mechanics: An beginning ~fthe review paper (Garabrant et al.) 2016): Updated Review and Meta-analysis) includes our 1997 are studi~s of motor vehicle repair activities and brake paper (Teschke et al.) 1997) as a 'tier l' study in the repair activities appropriate settings to examine the meta-analysis. risks of mesothelioma from chrysotile exposure? About a decade after our paper (Teschke et al.) The issue of interest is whether chrysotile asbestos 1997) was published) it came to my attention that causes mesothelioma. It may be reas.onable to study it had been used regularly in litigation related to jobs or tasks to investigate this question) but note that mesothelioma in people who had worked as vehicle the jobs or tasks are being used as surrogates of chry- N o mechanics or in brake repair. I do not normally accept sotile exposure. It is important to consider whether 0-, legal work) but agreed to take part as an expert witness they are good surrogates. Some occupations are syn- In one case to point out some problems in interpreta- onymous with extensive exposure to certain agents. tion of epidemiologIcal evidence such as ours in these For example) it would be a rare wood furniture maker cases. It seems possible that this new meta-analysis who did not have daily high exposure to hard wood will be used in the same way as our individual paper) dust and an exceptional asbestos insulator without daily so 1 thought it may be useful to present the issues in a high exposure to amphibole asbestos. For such jobs) more public forum. I will focus on two questions. the association between the occupation and a disease <1;) 'r he Author 2016. Pu bh,hed by Oxford Umver"ty Press on behalf of the BrItIsh OccupatIOnal HygIene SOCIety. 528 Letter to the EdItor 529. may be virtually equivalent to the association between Other oc.cupational groups, such as chrysotile tex- its predominant exposure and that disease. Many jobs tile wOl:kers, may be more appropriate occupations have much more variable exposures. For example, some to study. The most reliable epidemiological study nurses are regularly exposed to anesthetic gases and would measure chrysotile exposure and assess the others are rarely or never exposed. Examining the rela- 'exposure-response' relationship, not count on an tionship between nursing and spontaneous abortion occupation or task to act as an exposure surrogate. is not equivalent to examining exposure to anesthetic Even with 'exposure-response' analyses, data quality gases and that outcome. Because exposures are so varia- can make a profound difference in the strength of an ble within the occupation, any true 'exposure-response' observed relationshipj for example, a 9-fold stronger relationship will be attenuated or not observable when relationship between chrysotile and mesothelioma examined instead via an 'occupation-response' analysis. was observed with better exposure data (Sun;lorf and In the case ofvehicle mechanics, brake repairwork is Heederik) 2011). not consistently performed. Three studies (Woitowitz The second question addresses an issue that is and Rodelsperger, 1994j Teschke et al., 1997; Rake raised in litigation and workers' compellsation: is it et al., 2009) cited in the meta-analysis (Garabrant appropriate to require evidence of elevated associa- et al., 2016) included information on subjects' brake tions between an occupation and a disease to ascer- repair work separately from vehlcle mechanic occupa- tain whether someone incurred the disea~e as a result tionj at least 34% ofthe vehicle mechanics reported no of exposures in that occupation? brake repair work. Yet of the 16 studies included in the meta-analysis (Garabrant et al., 2016), 12 examined The answer must be 'no: Answering 'yes' requires thaf every per~on who has a disease arising from workplace only the vehicle mechanic job or even broader job cat- exposure .provide epidemiological evidence that their egories such as garage workers, auto repair and related specific job has an elevated risk ofthat disease. Ofcourse, services, and auto engineers. It is reasonable to expect it is impossible to study every occupation--disease rela- that many in these categories had chrysotile exposures tionship. In addition, even where a job has been studied, similar to background levels in the population. the potential for variable exposures within a job to dilute What about brake repair work itself? Four stud- the relationship is probable for many jobs, and would ies (Woitowitz and Rodelsperger, 1994j Teschke preclude a person with high exposures from havmg their et al., 1997; Hessel et al., 2004j Rake et al., 2009) in occupational disease recognized, Simply because others the meta-analysis reported on brake repair. The era in the same job were not similarly exposed. The question of potentially etiologic exposure in these studies was is whether the exposure caused the disease. A job cannot dominantly long prior to 1980, a period when vehicle cause disease} its exposures may. mechanics largely worked in gas stations and brake It may be helpful to think of this in another way. work was one possible task of many within the job. Studies of chrysotile miners and textile workers have The frequency of exposure was likely to be intermit- found elevated risks of mesothelioma (International tent, though it is'possible that rare subjects may have Agency for Research on Cancer, 2012), whereas stud- worked in specialized brake shops and done this task ies ofvehicle mechanics and brake repair workers typi- N repeatedly every day all day for most of their careers. cally have not (Garabrant et al., 2016). Does this mean Cl a- Interpretation of the results of the studies included that vehicle mechanics and brake repair workers are in the meta-analysis (Garabrant et al., 2016) should someho~ immune to the effects of asbestos, that they acknowledge the likelihood that many vehicle are espeCially resistant, superhuman? No, they simply mechanics had done no brake repair work and that of work in a job that has very varied exposures, so detect- those who had, most would have done so infrequently ing occupation-disease relationships is difficult. In as part of a broad array of activities. This means that other words, the effects of chrysotile are not properly both the vehicle mechanic occupation and the brake assessed via the surrogate measures of exposure 'vehi- repair task are unlikely to be good surrogates of chry- cle mechanic' or 'brake repair'. sotile exposure. Associations between the occupa- For people with mesothelioma 'who have been tion or task and mesothelioma were likely attenuated exposed to chrysolile in their job, the first question by subjects with background or low exposure levels. to ask is whether chrysotile causes mesothelioma 530 Letter to the Editor (International Agency for Research on Cancer, 2012). If so, the next question is whether they had sufficient exposure to cause mesothelioma. For some the answer will be yes, and for others the answer may be no. ]be question of what constitutes sufficient exposure is not simple to answer. In some jurisdictions, workers' compensation boards have a presumption in favor of compensation where a person has any workplace e"posure to asbestos and a diagnosis of mesothelioma. Others consider duration of exposure and/or intensity of exposure. Note that exposure, appropriately, is the focus. DECLARATION I was the first author of one of the studies reviewed in the Garabrant et al. article. In 2011-2012, I acted as an expert witness at the request of the Ruckdeschel Law Firm in a mesothelioma case to explain problems with interpretation of epidemiological studies such as ours. 111is is also the motivation for this letter. I wrote the letter, its contents are solely mine, and I received no funding related to it. No one other than reviewers and editors of the Annals of Occupational Hygiene saw this letter prior to it being accepted for publication. REFERENCES Burdorf A, Heederik D. (2011) Applying qualIty cntena to exposure in ,tsbestos epidemiology increases the estimated risk. Ann Occup Hyg; 55: 565-8. Garabrant DH, Alexander DD, Miller PE et al. (2016) Mesothelioma among motor vehicle mechaniCS an updated review and meta-analysis. Ann Occup }Jyg; 60: 8-26. Hessel PA, Teta M], Goodman M et al. (2004) M~sothehol11a among br,lke mechanics: an expanded analYSIS of a casecontrol study. Risk Anal; 24: 547-52. International Agency for Research on Cancer. (2012) Arsenic, metals, fibres and dusts; a review of human carcinogens. In Monographs 011 the evaluatlOll of carclnogemc mic; to humans. lARC Monograph No. 1OOe. Lyon, france: IARe Press. Rake C, Gilham C, Hatch] et al. (2009) Occupational, domestic and environmental mesothelioma risks in the British populatIOn: a case-control study. BrJCancer; lOt): 1175--83. Tcschke K, Morgan MS, Chcckoway H et <il. (1997) Mesothelioma surveillance to locate sources of exposure to asbestos. Call JPublic Health; 88: 163-8. Woitowitz H], Rodclsperger K. (1994) Mesothelioma among car mechanics? Ann Occup IIyg; 38: 635-8.