Document MMD02op8jyx3B20x8ZYGGn7NM

Federal; Register / Vok. 51, Na. 119 / Friday, June 20-, 1986 / Rules and Regulations' 22645 As pointed out. by Dr.. Wtil in. his written testimony. "Expoaurevresponse relationships havebeen reported! using as the biologic response indicator either a constellation of clinical findings to define asbestosis,.or certification.by a worker's compensation panel or board!' (Ex. 89, p. 24),. but such-approaches have "varying.degrees of limitation"'lEx. 99,. p. 12], Because ofthe many possible combinations, and'therefore "definitions" of asbestosis given by differentgroups, the quantificationofa' single risk'associated! with.aabestosi's is difficult. As Dr. W'eill'noted during cross examination:. * * * The problem is; with asbestosis, the quantification is not'exactly the same as it is with malignant disease: because one is dealing'with's'different set of ralesin the ascertainment of this health effect: And no two studies.have exactly'the same'scheme for making:a decision.that this'individual has asbestosis and'this.individual doesntt flTr,6/ 19, pp. 205-2001- In his prehearing:testimony, Dr. Weill explained further. Mortality date'are not useful livquantifying the risk ofestiestos-induced iung librosis (asbestosis):.Affected' workers may, die with asbestosisbut.notofiti in whicbcase il is not' likely toappeer on.thedeath certificate: as the primary causeof death. In contrast: sensitivity ofdetecting.early evidenced asbestosis in a living.expoeed population has increased substantially in recent years. . . . Since much.of die asbestuai's being seen now ls theresultof- lowerdusf levelfe in the pest two decadfes, the'films; are likely'to'be classified in the lowercategoriesofprofusibn of small .opacities, (fewer shadows,meaning' lesa severe-dispase). As ia frequently the case with biological maasurements^it is atithese lower, limits of diseasedetection.that inlerand Intra-observer varjahility'is greatest. Again, it-is-gratifying tb knowthatinspite of these'recognized'problems: excellent exposure^response relationships have resulted:from the:radiographic classification ' described [Ex. 99,23], Quantitative studies'exist,, primarily for the disablihg fbiTns of the disease; specifically, two: separate- studies provide information to develop a'dbse- ' response relationship:between, asbestos exposure and incidence-'of asbestosis [Ex. 84-254 and-84-44.]'Details' of the data were reported: at 48 FR' 51130. It is clear that material'Impairment from asbestosis occurs; prior to the: onset ofits disabling stage. ... As discussed: in, the1 November proposal; Berry ehah. [1979, Ex. 84-20): studied' a group of 379,men' who worked at an,asbestos textile factory for at least 10 years:'. Dost measurements; were available;and' were correlated-to<each, job.performed'foreachiyear under study. Health;effects- were correlated to cumulative exposure.. Using prevalence data, Berry et al. found adose-response A similar conclusion is; drawn in the relationship with,cumulative exposure, repost:of the-British, Advisory/ Committee (f-y/cc) for three endpoints,, crepitations-, on Asbestos* when the committee; noted- possible. asbestosis,: and' certified, that: "The, present-authors1 come, down in asbestosis.. In, addition,, these: data, alsO' favorof.a- tfose-response relationship: support the: hypothesis that, there. Is, a [asbestosis) without1 a threshold: for low,, or possibly no, threshold for chrysolite, within: the; range experienced; asbestosis, since, there, ia increased: risk in industry"[Ex,84^219*volume:2,p: 38). at cumulative, exposures: aa low as-37 Based; on: this recommendations OSHA fiber-years/cc. did.employ a. linear model! in: the: Berry and Lewinsohn- [1979, Ex: 84- prediction of risk from asbestosis,. but 254) have reported the: incidence; of made no-attempt in. the proposal to- asbestosis. in this- same'asbestos: textile: extrapolate the data, below the.0.5f/cc factory:. The population was divided, into, level or above; the;10.f//cc: level using two, cohorts: those: first employed before this, model. 1951 and those, employed-after 1950-.. A Based on1 the three-cohortsdiscussed dcise-response relationship is, apparent above; OSHA calfeulated estimates of for the incidence-data* though it. is-not the lifetime incidence of asbestosis for quite as consistent as. for the: prevalence the Finkelstein, Berry and Lewinsohn data. pre-1951 cohort, and1 the Berry and' In a second study, Finkelatein, [1982, Lewinsohn post-1950'cohoris, Ex. 84-44) looked! at the- development of respectively; The-estimates from the compensable (.certified):asbestosis "three cohorts differ by an approximate among 201 workers at an asbestos-- factor of three. This maybe indicative of cement factory, in;Ontario, A d'ose1- some-of the methodological-differences response relationship was,developed among the studies; For example; it is using estimated cumulative: exposures possible that the estimates msde from based- on plant dust, measurements' and Berry and Lewinsohn-'s data may be using medical information, from the: underestimates. The'maximum duration Ontario; Woi kmenls Compensation. of follow-up in that study waB'23 years, Doard. with an average folfow-up of l8years. As noted by D'r, Weill; "A final: complicating' aspect ini the: development' of exposure-responaeinformationon Observations' from Finkelsfein's d'afa (hisTablel): demonstrate1 that1 only 41% (23/58 cases)'of total'incidence was< asbestosis is that it Is aslowly experienced in the first 24 years:since- progressive disorder which may (and! first'exposure. That is, 59% ofthe frequently does), continue- to worsen asbesfosisi'ncid'ence was not'expressed after exposure ceases" [Ex, 99, p. 1,2), OSHA.'s: original; estimates of risk were' derived from' a simple linear . regression of thelncidtenceof asbestosis on the midpoinfsofthe cumulative exposure d'ata of Barry andLewinsohn and of Finkelstein. A linear relationsbip was assumed, at least for the point until at.leasf 25 years from onset of exposure,Thus, it is likely, that the low incidence rates in the Berry and! Lewinsphn.studfes (and, therefore the Ipw estimates ef. risk predicted from these dataware reflective of the short1 follow-up-period! for this group of workers. estimation of 0,5 fibers/cc for 45 years Op the other hand, Finkelstein's (1982), (or 22.5'fiber-years/cc). As-Dr, Weill observations may overstate-thej stated: incidence of asbestosis because-at. While the shape of the dose-response curve for asbestosis cannot' bo determined with certainty, it ia clear that this-fibrotic effect is dose-related, perhaps linearly. und whether a- autopsy there-was histologic, evidence, of silicosis as- well as asbestosis in many men. Finkelstein states that "we have, nevertheless, chosen to call their threshold existB may veiy well-depend;on the disease 'asbestosis" aswe believe'that is response indicator chosenfEx. 99, p. 11). the pathologic process of most The assumption, of risk linearity is consistent with-the fact'that'early-stages of the disease are-observed1 at low .exposures. This pointwas reilerated'by Howard Ayer on-behalf of the Organization Resources Counselors, Inc. when he'noted1 that: it does appear clear that there is a simple linear relationship between the frequency and degree ofasbestosis'and'the cumulative exposure to asbestosidiist; Time is'merely a factor in thal'it takes a certain1 amount of' time--al.least a matterof years--to develOp significance. Most of the parenchymal' radiographic abnormalltieswece-small irregular opacities-and the mortality . pattern among thememwas,consistent with the toxicieffects of asbestos!' [Ex. B4-44, p. 500). More importantly/,, it. ia indeed possiblethat all.of. these:investigators may have undersfated; asbestosis risk, by,1 examining.only certified: disability from asbestosist. which: istani advanced; stage of the disease. As; noted! in; the' November proposal, there was'evidence the effect on the lung |Ex. 91-10-2, pp. 4-5|. of the earlysigns of: asbestosis at levels GLEASON-000893