Document eDQ2Rk3g1mgdpoxQR1jyDy99

y- 'i.......... TESTIMONY OF HAMS WEILL, K.D. OSHA HEARINGS ON THE PROPOSED RULE ON OCCUPATIONAL EXPOSURE TO ASBESTOS JUNE 19, 1984 My nai* is Hens Weill and X a* Professor of Hadicine and Chiaf of the Pulmonary Disease Division at tha Tulana Radical Cntr In Naw Orlaana. I direct an intardiaciplinary unit engaged in'tha invaatigation of occupational lung diaaaaaa, with currant raaaarch projects dealing with the wide apactrua of mineral and organic duata, and chemical vapora and gaaea in tha workplace. Z and my colleaguea have atudied the reapiratory effecta of aabeatoa expoaure, during the paat fifteen yeara. I h ve served aa preaident of the American Thoracic Society, the medical and aclentific arm of the American Lung Association, and aa currently the chairman of the Pulaonary Disease Advisory Committee of the National Heart, Lung and Blood Institute (NIH). Our research haa been supported primarily through federal funds' (eg NIH and NIOSH). Hy colleagues and I are continuing our inveatigationa of the morbidity and mortality aasoeisted with occupational exposure to asbestos in the manufacture of asbestos cenent building products. During this year I aa in residence at the Brookings Institution in Washington, as a Fellow in Science and Public Policy. Hy work at Brookings involves an examination of the use of science in policy decision-making as it relates to the asbestos-related diseases, including the regulation of workplace expoauree. 1 asbestos and its effect on health Under certain conditions of aabaatoa Mining, Milling, Manufacturing and end-product uae, an airborne duet cloud ia generated and fiber* may ba Inhalad by proximate workers. Fiber deposition, clearance, and tissue persistence are primary determinants of the types and severity of the diseases which may ultimately result from asbestos exposure. These factors are in * turn importantly influenced by fiber type and dimension (diamoter end length). Dust concentration and length of exposure, which determine the total or cumulative lung tissue burden or "do**" are quantitatively related to measures of the disease outcomes. Where differences in disease risk have been associated with parts of the industry studied, such risk gradients are likely to be r*latd bo the feetere emier*ted above. Very thin fibers (generally <1 micron in diaaeter) are Most likely to be deposited deep within the lungs and relatively long fibers OS microns) are most likely to he retained for long periods of tlae in lung tissue. The distributions of fiber physical dimensions almost certainly relate closely to the pathogenic potential of the asbestos exposure. Thin or "respirable" fibers are carried down the branching air conducting system of the lungs, the bronchial tree. They are -most likely to deposit in the smallest such conducting tubes, called respiratory bronchioles end alveolar duets. These 2 structures not only conduct air Into tha lunga but also participate in tha cxchang* of oxygmn (uptake) and carbon dioxida (raioval), tha primary function o tha lunga. Tha fibers raaching thaaa daap racaaaaa of tha lunga hava aacapad tha initial dafanaa aachaniaaa which protact aan againat inhalad particles, aotila projections (cilia) and a oving ucu* layifir on tha lnnar bronchial aurfaca which propal tha fibara upward whara they can be awallowad or axpactoratad Fibara onca deposited in th lung aay than be angulfed by acavangar calla (phagocytaa or aacrophagaa) but whan tha fibara ara long, tha phagocytoaia la likely to ba incoaplata. When auccaaaful, engulfed particlaa aay ba eliainatad by tha muco ciliary aacalator or by transport to tha regional lymph nodaa. They aay alao be coated by protein and iron frca tha tiaaue and remain for long periods of tine as "asbestos bodies", perhaps having 1 st their pathogenic potential. Remaining asbestos fibers embedded in the tissue lead to the development of diseaae over many years.' Two primary tissue, responses result from asbestos exposure: scarring (fibrosis, called asbestos!s when the lung la Involved) and cancer (carcinogenesis). Fibrosis begins in the peripheral and lower ronoa of fcho lungs, a reflection no doubt of the pattern of heaviest mineral deposition. Gradually, the process becomes cissemi.iated throughout the lunga. A characteristic of ~the~ibrotlc luag is that it is contracted (smaller then normel), tiff (poorly compliant) end deficient in its ability to exchange 3 gases. Tha precise biological *chni la incompletely understood. Macrophages which only partially ingest a fiber are damaged and relaaae aubatancea which Induce other cells (fibroblasts) to produce and lay down acar (collagen). Once initiated, the fibrogenlc process i progressive, even after e.-.posure to asbestos ceases. Generalized or focal fibrosis (the latter called plaques) of tha lining of the lunge (pleura) ia also a common consequence of asbestos exposure, but with rsre * exceptions results in no functional impairment and should be considered only as an indicator of exposure. Significant asbeatoaia la recognized only as the result of occupational exposure to asbestos; pleural fibrosis say result from environmental (eg neighborhood or household) exposures. Zt ia not likely that clinically Important chronic airways obatruction (as seen with chronic bronchitis and emphysema) ia the primary consequence of asbestos exposure. Important increase in risk for developing two malignant tumors has been xepeatedly demonstrated in asbestos exposed individuals: lung cancer and mesothelioma, the latter a cancer of the pleural or peritoneal (abdominal lining) surface. The carcinogenic mechanism in either case ia poorly understood, but csrtain relationships ha emerged, perhaps giving soma clues to pathogenesis. Risk for lung cancer la greatest those exposed individuals who have also developed asbeatoaia. Indeed such 4 c -V " -V evidence which la available auggeata that, an axpoaura doae which detactably lncrttnei tha riak of lung cancar will alao raault in aabaatoaia in a alallarly axpoaad population. Saoklng incraaaaa tha lung cancar riak in a aynargiatic aannar. Evidanca that pacific lung cancar call typaa or lung location of tha tuaor ara particularly aaaoclatad with aabaatoa axpoaura, ia not convincing. Aacant lnvaatigatlona auggaat that aabaatoa may act aa a tuaor proaotor following tha indapandant initiation of tha prt>e*>. It ahould ba bor.a in aind that thara ia a aubatantlal background of thla tuaor in tha ganaral population (130,000 caaaa in tha U.S.par year) and thara ara no apaelfie lndicatora of aabaatoa cauaation. Excaaa riak for tha davalopaant of thia tuaor ha* baan recognized only in occupationally axpoaad populationa. All aabaatoa flbar typaa have baan aaaoclatad with axcaaa lung e*ncr riak. Fortunately, aeaothelioaa ia a rare tuaor (approxiaataly 1500 case* in the U.S. annually), aince it ia alaoat invariably fatal, no effactive therapy being available. Moat caaaa ara caused by exposure to aebestoa, the proportion being variable in tha reported retroapectlve reviewa of aerie* of caaaa. Klniaua causative axpoaura doae ia likely to be ahortar and perhaps lower than for the other asbestos associated diseases, probably explaining the considerable nuaber of reported cases with doaicilisry and neighborhood exposure. It has been suggested that aabaatoa acta aa an initiator of thia tuaor. Expoauraa early in life are apt to lncrttM tht risk greatly aince it appeara that the riak incraaaaa by the power of three or four with tine aince 5 5553 first axposura. Evidenca for a gradient cf risk in relation to fiber type ia strongest for aeaothellosa> exposure to crocidollte or asosite being such more likely to result in the development of this tumor than chrysotile. Usually, two or more decades elapse from first exposure before either the non-malignant respiratory effects or the calignsnt intrathoracie. tumors become clinically evident; the "latency period". Other cancers have been less consistently found to be associated with asbestos exposure: most prominently gastro intestinal and laryngeal; less often ovarian and kidney. The epidemiologic evidence is equivocal and the animal studies are not at all supportive of these putative relationships. DEVELOPMENT OF KNOWLEDGE REGARDING THE HEALTH EFFECTS' A quarter of a century following the commercial introduction of asbestos, the first case of lung fibrosis, later called eabestoais, was recognized and reported to the British government. By the 192C'e and early 1330's aaseotaaia risk was clearly recognized in asbestos textile manufacturing on both sides of the Atlantic, as reflected by the medical literature. That this risk was dose-related was shown by USPHS studies in the late 1'330's, leading to the first suggestion of a dust exposure level intended to result in no risk of disease (threshold limit value). Aabestoaia risk in users of asbestos-containing products weV regarded as minimal as the result of s report on New England shipyard workers, published in ths mid 1940's, and it was not until* twenty yrera later thet of ineuXatore ahowed substantial evidence of lung fibroala in thia occupational group. Caae reporta in the United Kingdom, Germany and the United Statea in the 1930'a firat. augjaatad that, an lncreaaed nuaber of lung cancera aeeaed to occur In workera with aabeatoaia. An autopay atudy in the U.K. aupporting thia aaaociation waa publiahed in the lata 1940'a and, in 1955, ti.e firat * epidealologlc atudy of workers in asbeatoa textile aanufacturing clearly ahowed increaaed lung cancer riak in thia expoaed population. Excess lung cancer riak in mining and ailling waa eatabliahed in the late 1960'a and early 1970'a and in insulators in the early 1960's. The relationship between aabeatoa exposure and lung cancer riak waa accepted earlier in the U.K. and Europe than it waa in the United States, uh,r, the scientific community was not unlforaly convinced of the riak until the 1960'a. A rare and highly aalignant tuaor of the pleural and peritoneal eurfacea, seoothellona, uaa aaaociated with exposure to eabeatoa aa the reault of iaportant observations in South Africa, reported in 1960. Workera and others expoaed to crocidolite aabeatoa in and near the ainea in the Northwest Cape were found to (and di* of) thia fora of cancer with alarming frequency. Subaequently, aeaothelioaa riak waa confiraed in aanufacturing and end-product uae of aabeatoa around the world. The relevance of nan-occupational exposures in the causation of - thia tuaor became increasingly apparent. Exposures were often 7 short with a long latency period of generally two to four decades. . SCIENTIFIC ISSUES XH QUANTITATIVE ASSESSMENT OF RISK Quantitative risk assessment underline the rational aanageaent of that risk by regulatory policy. The greateat publi confidence in deciaion making to reduce an envlronaental or occupational riak reaulta when the data uaed are the product of *. well designed and conducted studies of relevant hussn populationa. Thia type of inveatigation la called epidemiology, the inveatigation of populationa in order to detect the distribution and deterainanta of disease. The strength of epidemiologic evidence varies with study design, sots types of studies being aore "powerful" than othera. When n occupational h.urH ha been identified, useful epidemiologic study results will determine the quantitative relationship between the dose of exposure to the csusative agent and the riak of the adverse health response in the exposed population. The product is the exposuro-rBsponse relationship, which together with a valid estimate of the size of the exposed population, the extent of that exposure and accurate indicators of the disense outcome, give the characterization of the risk. It will, of course, also provide levels or cumulative doses of exposure which can be expected to result in a predetermined riak, including one which is considered to be "reasonable** or "acceptable". Optimally, the exposure-response relationship for a specific egent will be -; generallzable for all circumstances of exposure; often varying 6 relationships tr found for differing condition*. It ha* baan primari 1y mi nee 1970 that valid quantitative aaaaaaaant of the risk haa been accomplished for varying circuaatancea of asbestos exposure in the workplace. Although auch data for aabaatoa axpoaure ia probably acre coaplate than for any other occupational axpoaure, it should not be aaauaed that all uncertainty regarding the axpoaure-reaponae relationahipa ha* been reaolved; it haa not. At present, exposure-response relationahipa have been established for asbestos-related disease in mining and allling; and in various parts of the manufacturing of asbestos-containing products, such as textiles, asbeatoa-ceaent, and friction aateriala. Since contemporaneous measures of exposure are not available for workers exposed to the dust of end-product use, auch as insulators and shipyard employees, any quantitative risk analysis based on exposurt-response estimates will be less reliable than when these data are accessible. Attempts have, however, been made to estimate "average" exposures for these industries, which have then been used to construct a slope booed on certain additional assumptions, eg. the ahape of the exposureresponse curve for lur.g cancer being linear without a threshold. Such a alope will be baaed on one axpoaure point and will contain considerable uncertainty, being clearly interior to alopcs constructed froa multiple axpoaura-apec.fic risk points, which show sn exposure-related risk gradient. Regulatory decision-making for the prevention of aab,,ts,- 9 related would be substantially aimplmr if the quantitative risk analyaaa gave similar res ilta irraapactiva of tha Industrial procaia, type<c) of aabaatoa fiber to which tha workar had beer. exposed and tha apociflc aabaatoa-i rduced diaaaaa. The avidanca indicataa that such comparability la not tha caaa. An additional complicating aspect in tba uaa of existing quantitative estimates of risk la that all ganaral environmental levels of aabaatoa exposure and moat racant occupational axpoauras will ba lover tha.) any of tha obaarvationa or eatiaataa of paat axpoauraa which hava bean uaad to derive exposure-response relationships. In order to aaaeiaa risk at the relevant lavala of exposure which are of current concern, extrapolation of tha ralatlonahlp to thaaa lavala below which "hard'* data are available, becoaaa nwcaaaery. further, even if epidasloJoqic data were available on health experience at currently relevant low exposures (after the appropriate latency period for the disease appearance has elapsed), the sensitivity of tha methods of disease detection, particularly cauae-apacifie mortality, is, in general, not likely to be sufficient to reliably measure this level of risk. Therefore, specific considerations neceaaary to generate quantitative rim': assessments for asbestos axpoauro include: the shape of the e::poaure-reaponse curve, differing risk estimates for the various expoaura-related diseases, the influence of occupational potential odlflr of tha doM-raaponta relationship (eg. smoking). Thaaa factor* will oftan not be Independent, or indeed, diatingulanabla In thalr affect on tha risk analyala. It la, however, lncuabant on aclantlat* to take thaaa and othar potentially influencing factor* Into account and claarly preaent tha aaauaptlona which hava baaa aada ao that an optlaal characterization cf tha rlak will emerge. " INFLUENCE OF DISEASE OUTCOME ON SHAPE OF THE CURVE Whila tha ahapa of tha doaa-raaponaa curva for aabaatoaia cannot ba datarainad with cartalnty. It la ciaar that this fibrctic effect 1* doae-related, parhap* linearly, and whether thraahold exists aay vary wall dapand on tha reeponte indicator choeen. Tha clinical and other feature* of tnie di<e of the lung include abnoraal cheat aounda heard on eu-icultaticr. Crolea or eracklee); ehortneen of braath which la exceasiva for the level of phyalcal activity in which tha individual i engaged; rarely, deformity of tha tipe of tha linjere nf oei (Including tha nails) called clubbing; email linear or irregular ahadowa on tha cheat x-ray fila; derengeeent of tha function cf tha lung, eoet oftan reduced voluaea and diaturbence of ga* (oxygen) exchange; and certain pattern* o( abnormality detected or. aicroacapic exaainatlon of lung tlaaue (fibrosis and asbestos bodies!, uaually obtained by aurgical biopsy or autopsy. All of thaaa features are non-specific but in practice, for clinical - (and legal) purpeaea, sls exposure history eod eherertarlatlc a h '~ ray pattern are sufficient for asking a diegnoaie. Zn atad la* of t y x . .;r.yu*ijR 3r5 .1 spoaad populations, relationships hava Won sought by aaasursaant of tha ra >naa uMog s prsdatarainad combination of thaaa fsaturss of th l*a*. *g, at Isast thrao), oaa of thaa (g, tha a-ray pattarn. *ftar othar poasibla la/lwancUf factors hava baaa taksn into account), cart iftcstlon by an ad*lftlatratl*a body for purpoaaa of eoapanaatlon, or mortality Oats which dapaad on tha daath cartlflcats ^ i noaaa . Thaaa approaches has varying dagrasa of llaltatlon, inciu-llng abasrvar variability, sad tha a _ Bang want uncartalnty aust ba borrva in Bind vhaa avsluatlng raaultiog data. A final complicating aapact in l\a davalnpasot of aapoaura* rsaponaa information on sabwatoala la that it la a alowly prograaalva dlaordar which aay land fragwonlly tfoaa) coatlnua to vsricn aftar aapoaura caaaaa. Varying atudiaa hava loohad at tha pravalanca or inctdanca of tha dlaaaaa aa tha biologic raaponaa varlabla. Pravalanca la a aaaaura of tha fraguan?y of tha condition in a population at er.a point in tiaa and la tha rasui; of both tha rata at which tha condition la appaartng in tha population unear atudy. aa wall aa survival of tha affactad individuals. IncidsAcs la tha Busbar of now caaaa which ara baing rC09ll*? <l. dlagnoaaO during a apacifiad pariod of tiaa, usually pa.- yaar. Tha Uttar ta ga-sraliy ragardad aa aamg u, aora inr:r*t:* aaaaura. alnca :t aora fully aapraaaaa tha riaa. Thaca la 11ttla dlaagraaaaat that raducad raca^t aapoauraa hava raaultad in lovar riah of aabaatoaln and la-aa aawa diaaaaa. Whan aabaatoala ta alaiaally datactahia. it la aot 12 llkmlf to lapalr fIon. prodwca ayaptoaa or raduco longavity, d thorofora, rlah analyala for abtoU haa boon ralogatad to a poaltlon of Uaaor laportanco in contraat to that for tha aaltgnant eonaoquaocoo of aaboaton axpoaura. Quaatltatlva rlak analyala la quit# a dlfforont aattor for Um aallgnaat dlaaaaoa duo to aaOoatoo aapoaura. Ao ragarda tha ahapo of tho doaa-raaponaa alopo. an oprUonal 3ud^nt la boaad on tho conclusion that thara la currant!? no avallabla avidanca that oonvlncln ly pro*** that tho alopo la not linaar. croaa1ng tha rlah aal* at tha origin. Thla aaauaptlan ( aadn in tha C5>i a rlah analyala) la juatifiao fro* tha eb*r>*isn. at aodarata and high lavaia of aapoaura ti *. ganorally lnClcata linaartty. which whan aetandoo oovnwaru v. l**ta of *poaura Valow which oPt*r<`.lona are available, ro not lnconalatant with linaar low do*# l r apol at ion . Tatting into account tha ralatlva inaanait1*1ty of population atuCiaa to oatect alight mcraaaaa in riau of aalignant dlaaaao* it wnlifcaly that apldaalology will avar provlda avidanca ragardlng tha ahapa of tha curva at Ita lov and or whathar a throohold exlsta. Mowavar, tha poaatbility that auch avidanca aight aaarga from anlaal aolala of c*rcinogana*ia la not ** pr.*nt. it ***** raaaonahl# iprudani), that forpurpoaaa of policy davclopaant, tha linaar- at-lo** 00**, no thraaholu aocai ba aaployad. " Of tho tho two Mjor wlt|*t d i iiimo* cauood b> aaboatoo axpoaura, lung caacor and aoaothal loaa, tho for war la highly 13 prevalant in tha ganaral population (background) and la aoat often not tha raault of aabaatoa or othar occupational axpoaurc. Tha lattar la, however, rara and aoat often cauaed by aabaatoa xpoaura. Vhlla available data Indicate that both eondltlone are doaa-relatad, quantitatlv < aapacta cf aabaatoa-Induced lung cancer riak are batter knovn than thoaa for aaaothell->aa, owing prlaarily to tha relative frequency of thaae tuaora and, parhapa, to differential accuracy of dlagnoala in the pet. Beat evidence at'pracent indlcataa that while the lung cancer riak curve la linear in relation to doae, aeaothalloaa incidence alao aeeaa to incraaae with the third (or ellghtly greater) power of the tine interval alnce flrat. tpo>ur, In addition to being proportionately related to lntanalty of expoaure. For tha raaaona already given (dlffaraneaa in background incidence of tha two typaa of cancer), lung cancer riak ia uaually axpraaaad aa a ratio of obaarvad caaee, in a population or axpoaure aub-group, te expected nuaber of case* in non- axpoaad coapirlion group, auch ae the U.S. population. Depending on the specific study design, this say be axpraaaad in standardized aortality ratios, riak ratios or relative risk. Since the occurrence of mesothelioma in an aabaatoa exposed individual la conaidarad to be eauaally related to the expoaure, riak la axpraaaad in actual nuaber of caaea. No convincing doaa- raaponae ralationahlpa have been reported for other cancera (ag. (UointMtlnal). . 14 INFLUENCE OF INDUSTRY SEGMENT CM THE RELATIONSHIP The relationship* betusan doaa of aabaatoa exposure and lung cancer risk, as determined by various apideaiologic studies, vary considerably, according to the segment of the industry. Where valid doae-reaponaa data are available, there is s gradient of risk (highest to lowest) froa the manufacture of asbestos textiles to asbestos-cement and other asbestos-containing products and finally to mining and milling, and friction * materials manufacture, where the slope is least steep. As Indicated previously, aabaatoa pathogenic potential seems to be related to fiber dimension, namely diameter and length. Longer, thinner fibers ara probably moat hazardous, this type of physical configuration being moat likely in the textile Industry. Other factors, a* yat unrecognised, may also ha important in this regard. Accurate doee-reaponae relationships are not known for end-product uae, air.ee minimal exposure data for relevant time periods are available. There la no evidence to suggest that maaethalloma rlek variea signifleant1y by industrial activity. EFFECT OF FIBER TYPE EXPOSURE Thar* ia a growing consensus that amphibolaa are more hazardous than chryaotile. The evidence is based priaarlly on studies of exposed human populations; aniaal axposura data are not confirmatory of this risk gradient. The moat impressive gradients of risk by fiber type have been demonstrated for mesothelioma. In mining of chryaotile and crocidollte and in the 13 t manufacture of textiles, friction materials, and gas masks in World War II, the mesothelioma experience of axpoaad worker* haa baan strikingly laaa favorabla in thoaa who wara axpoaad to aaphibolaa alona or in coabination with ehrysotile, in contraat to populationa axpoaad to chryaotila alona. For axaapla, in tha atudy of South Carolina aabaatoa taxtila workara, whara tha lung cancar riak waa aaong tha highaat of any daaonatratad, tha aaaothalioaa riak waa ainiaal. Thaaa workara wara axpoaad only to chryaotila aabaatoa. Maaothalioaaa hava baan ralativaly rara in ainara and aillara of chryaotila aabaatoa in tha Province of Quebec, in contraat to tha axparianca of thoaa occupationally and environmentally axpoaad to tha duat of tha crocidolite lines of tha Northwest Capa of South Africa and Australia. During the Second World War, gaa aaak filteni were manufactured using aabaatoa. Apparently, crocidolite was considered superior for this purpose and waa therefore utilized in making tasks for military peraonnel; chryaotile was employed in the production of civilian gas masks. In workers engaged in this wartime activity in Nottingham, U.K., and in Ottawa, Canada, a substantial differential mesothelioma riak haa now become apparent, following the expected several decades of latency time for the development of these tumors. Agsin, most of the mesotheliomas are occurring in those individuals previously exposed to crocidolite. If one exesinea the twenty sejor epidemiologic studies of mortality in aabeatoa-expoaed workers which have been published is to data (or tr about to be), mesothelioma experience can ba compared by fiber type exposure in raiation to axcaaa lung cancar risk, axpraaaad aa observed caaaa minua tha axpactad. Tha lattar might ba thought of as a aurrogata aaaaura of axpoaura, allowing for aaaaaamant of aaaothalioaa riak aftar diffarencaa in loval of fibar axpoaura have baan takan into account. Tha highaat avaraga ratio for aaaothalioaa/axcaaa lung rincar appaara in tha crocidolita exposed populationa, followad by mixad fibar * axpoaurea (uaually Including crocidolita), than aaoaita axpoaura, and tha lowaat ratio found in atudiaa of populationa axpoaed to chryaotile alone (aee appended table). The evidence on fiber type influence on riak of aabaatoaia and lung ene*r ia far leaa convincing, primarily because it is much more limited in extent. Where auch evidence has been sought,# it has generally suggested thet, aa with mesothelioma, these risks tend to be greater if there haa been exposure to phibolas. There are biologically plausible reasons why fiber-specific riak differentials might eximt. Reference haa previously been made to the importance of fiber dimension in pathogenesis. It is likely, for exaaple, that a cloud of asbestos dust contains a higher proportion of reapirable "carcinogenic" fibers if crocidolita is present (fibers >8 microns in length and <1 micron in diameter). Crocidolita might therefore be more likely to be deposited in the deep portione of the lung and migrate more 17 easily to the pleural surfaces. Additionally, it ha< been racognizad that chryaotila fibara do not hava infinita tiaaua persistence. Thay ara known to ba aolubla to aoaa extant, probably dua to leaching of thair aagnaaiua. Uorkara with aany yaara of pradoainantly chryaotila axpoaura may, on alagant ainaralogic axaaination of thair lunga, hava nuabara of thaaa flbara aiailar to unaxpoaad controla, claarly indicating that lung tiaaua analyaia la not an accurata Indicator of chryaotila axpoaura. Thla la not tha case with aaphibola axpoaura, thaaa fibara ganarally balng ratainad in tha tiaaua for vary long parioda, aa daaonatratad by coaparable lung tiaaua analyaia. Thaaa dlfferencaa in tiaaua paraiatanea aay wholly or partially axplain tha obaervationa in huaan exposed populations cited abova. Von-confiraatlon of fibar typa differences in nniaal axparlienta aay ba ralated to tha *urh shorter Ill's span, not allowing the effecta of varying tissue persistence to be expressed. ASSESSING THE QUALITY QF THE DATA Risk asaasaaent infarsnees auat ultiaataly taka into account the form and quality of the data upon which the ana./sia la baaed, aaong other factors. Uuantificstlen of the rink depends first upon the quality, the fora and the temporal appropriateness of tha axpoaure lnforaation in tha jroup for whoa riak la being ralated to axpoaura. Thaaa factors hava varied considerably ssong tha atudlaa which ara avallabla for possible risk analyaia. IS In the i860'a and before, airborna duat aaaauraa In workpieces in which there haa baan aabaatoa axpoiura, 'have quantified total particulataa (all duat), not just aabaatoa fibara. Slnca tha relationship batwaan fibers and othar particulataa la known to vary undar differing conditions, exposure to aabaatoa during thoaa yaara can only ba aatlaatad by applying ratioa to convart total particulataa to fiber lavala. Thaaa convaraion ratioa hava at tiaaa baan aapirically datarainad undar aora racant conditiona and aaauaad not to hava changad auch froa tha paat (although lavala of axpoaura cartalnly hava), or thay have been aatlaatad without direct aeaauraaant. Tha nuaber of actual duet aeaauraaenta which can be uaad for axpoaura raconatruction la very liaitad for work altaa before tha 195C'a, an era with obviour influence on health riak being observed in recent years, due to the latency effect, already discussed. Measurement of airborne fibers (of a certain diaension) become prevalent in tha U.S. only in the late ISfeO'u. While helping to estimate past exposures in terms of fibers, the actual asbestos concentrations determined can be validly correlated only with the health experience now evolving in exposed workers. However, epidemiologists appropriately utilize the best available data, while at the aaae tlae fully presenting tha limitations of these data. And so they have done, with individual exposure dose estimates being derived froa total and asbestos dust measurements for whatever time periods for which thay are available. Taken into account la tha time of aeaauraaant, job hiatory of members is '- CAW>* u of the study cohort, and conversion ratio* for xprtaalon of dos* In fiber levels (tha way in which atandarda for workplace axpoauraa ara now axpreased), and uaeful expoaure-reaponaa ralationahipa hava baan generated. Quantification of "dose** haa generally baan accoapliahad by aatiaating cuaulativa exposure, obtained from tha product of duat concentration for a particular- 30b at a apecific"tie -period and tiaa at that concentration, with tha raaulting producta over tha working lifatiaa being auaaed. Thera ara two aajor aaauaptiona in thia procedure, neither preaently aciantifically provable. Firat, that a heavy expoaur* over a ahort tiaa ia likely to reault in tha aaae risk am a low or moderate level expoaure over e longer period of time, if the product ia the aaae. There ia certainly evidence that both duration end concentration of expoaure influence risk, but the precise quantitative contribution of each ia not known. Secondly, aince the aineral haa a long reeidence period in lung tlsaue and presuaably continuea to exert its pathogenic effect after exposure ceaaea, soae weighting of exposure dose by residence or tiae aince first exposure aight sees appropriate. However, a valid way of doing thia haa not been deaonatrated. In spite of the difficulties suaaarized, these curves, in the sain, appear quite plausible, essentially always showing doae-relatednesa of the effect, and bear reasonable relationship one curve to another, when the conditions lead to the expectation of concordance. 23 Least satisfactory for purpotaa of quantitative riak analyala la whan tha ebaenct of duat measurements during tha appropriate tiaa parioda aakaa it iapoaaibla to attempt to racunatruct Individual aatlaataa of exposure ovar tha worker'a lifetime. Aa a substitute, applying one or aora average axpoaura eatinatea to large aagaanta of tha atudy population may aaaily lead to misleading overall quantitative eatlmatee of riak, alnce there la likely to-have been considerable variability -among those considered to have the aaae exposure. Additionally, when average levels of exposure are used for atudy groups, a gradient of risk by dosa of exposure cannot emerge atd cannot, therefore, provide a degree of validation by showing that the riak is indeed, doserelated. This is the situation for the studies of insulator- and shipyard workers. While providing qualitative information on asbestos-associated diseases, these studies hsve limited utility in producing reliable exposure-response relationships upon which to set workplace standards. This is particularly regrettable fros a public health point of view, since the important asbestos exposures in the recent past and in the future are likely to be in those whose work puts then in contact with asbestos-containing sstarials, as in the construction trades. Tha state of affaire regarding data quality ia aubstantially better on the other aide of the exposure-response relationship, ascertainment and quantification of the adverse effect on health. There too, however, uncertaintlee exist. Primary reliance for riek assessment in the malignant dieeeees associated with asbestos exposure is placed on analysis of age and cause-specific 21 Mortality. Coiptrlaoa peculations aKould be appropriate for the cohort under study, and difficult choices have been encountered when county, state and U.*3. cancer rates have differed. Expected deeth rates Must be obtained for the coeperable era because o secular trends (changes) in mortality experience in the general population. The study population vital status should be known for a high proportion of the cohort end sufficient follow-up time Must be allowed to accuretely reflect the risk of long latency * diseases, such as occupationally Induced neoplasms. Death certificate diagnoses have a margin of error, but attempts to obtain further information regarding diagnosis after death, such as review of pathologic material, have not ganerally elterrd study results or interpretation. Incidence (new esses occurring per unit of time) of tumors may not be accurately reflected in mortality dou. Unfortunately, in the ease of lung cancer and mesothelioma, the primary tumors of interest in asbestos exposed populations, their very poor cure rates result in a satisfactory approximation of incidence by mortality statistics. Uncertainty regarding the risk of death from a specific cause in an exposure category will obviously be affected by the number of cases in that cell, the number of cases expected for that group and indirectly by the total size of the study population. Smaller nu.bera widen the confidence limits, and consequently redt.ee the precision of the exposure-response slope. While these potential limitations may seem to be overwhelming, in fact, extremely useful risk snslyses have been possible end there ie emexingly . broad-based confidence in the estimates. 22 > Mortality data ara not useful in fully quantifying tha riak of asbestos-imluced lung flbroaia (aabeotoaia). Affected workers ay dia with aabaatoaia but not of it, in which case it ia not likaly to appaar on tha daath cartificata aa tha primary cauaa of I daath. In contract, aanaitivity of datacting aarly evidence of aabaatoaia in a living exposed population haa Increased aubatantially in recent yeara. Standardization -in the reading of abiforaalitiea consistent with aabaatoaia by radiographic (x-ray) claaaification haa been aapeeially facilitated by continuing improvement in the international claaaiflcatlon now widely uaad <ILO>. Tha randomized raading of filma of axpoaed workers, without any information regarding tha individual whoaa fila ia being claaaified, including exposure, results in quite good reproducibility of readings or at laaat consistency in "over or under-reading". Since much of the sabestosis being seen now ia the result of lower dust levels in the pest two decades, the filma are likely to be classified in the lower cstegcries of profusion of small opacities (fewer shadows meaning less severe disease). As ia frequently the case with biological aeasurenents, it ia at these lower limits of disease detection that inter- and intra-observer variability ia greatest. Again, it ia gratifying to know that in spite of these recognized problems, excellent exposure-response relationships have resulted from the radiographic classification described. J Uhile tha cheat x-ray indirectly meaaurea structural or anatomical elterationa in the lung, pulmonary function testing 23 ' 4 *.' ' * ` l~ !'* the tffack tnet injury to the lung tluu* ham had on t ha capacity of the raaplratory a>itai to perform its basic functions of delivering "fresh" air to tha distal lung sacs (alveoli) for ha purpoaa of axchanging gasas batwaan tha lung and blood; la. oxygenation. Asbaatsaia will, at aoaa stag*, intarfara with thla normal function, but to may cthar injurious influancas (eg. . smoking, allargy) . As with x-ray raadir.g in the dust disaa -as, pulmonary function tasting has bacoac increasingly standardized * With bitiar quality control and iaprovJ apparatus. Uhtn using functional laaaureianis as indicators of a dust affact, which has resulted in quite satisfactory expoaura-reaponaa ralationahipa, other potential confounding influences auat ba taken into account in the statistical analyses- It appears, at llaat on the basis of population-based data, that tha cheat x-ray and lung function are equally sensitive in the early rteti- tion of SabestoaiS, although in an individual case, one method may reveal abnormality before the other. Exposure-raapenaa ralationahipa have been reported using as the biologic response indicator either s constellation of clinical findings to define ssbestoais, or certification by a worker's compensation panel or board. These two studies, from the Jnited Kingdom and Cntario, used incidence of ssbestoais and found different quantitative relationships with estimates of past asbestos exposure. The variation in results may have been due to differences in length of maximum follow-up (more case* being expected when longer follow-up is possible); differing criteria 24 - ... ---1 by the two certifying bodies for coepensetlon ewei-Oa; ' - *o differences In tthod of determining past pour# g - . - * likely>. How do tha txpouri*rponM rl<tionat>lp tor the as;er outeotat of Mbto erpoaure differ! With *rf too xcption, (pacific curve* are not available tor neeoihellaea but. indirect evidence strongly suggests that exposure <aaa rdfcuitlng in this tuaor nay certainly be abort. It net Joe. Presumably, the expo*ure-rapofi3 curve would be expected la be steeper than that (or lung cancer risk, under the aaM circuiataneea, although tor aoat aortallty aludlea of war*i* population# exposed to aa-beetoa, tha auaber of excess . ung cancer caaaa la likely to exceed the frequency of eesolkel ln. Thla la undoubtedly influenced by factor# other than cumulative doee of asbeatoa, luett aa the low background incidence In the general population and abaance of tha Important influence of aoaothelloao risk. The power relationship of mesothelioma rlaa with tlaa since first exposure also result# in manviiM rt uhan exposure first occurs later in life. Population data are net now available, nor are they likely to bocooo M in iju future, is eat a paraiaalbla exposure 11*11 in tha workplace baaed na exposure-raapinaa ralat lona.Mpa ter tn;a tuaor. v Although peat standards for asbestos have generally beea baaed on aabeatoala risk, this la no longer the cane. The cur rest eaphaaln In asbeatoa risk analysis la flraty fecua ad aa the aellgnent consequences of thla exposure. It therefore beoeeae la eoaaUar 4U >l(t rUa l*Ur(Uaa f*{r<la< IM ra'itii nab of **alaU M imm Unf > :*f il t**Mf H of at^aaara. toforo **-1M UU. tt *l /iral H c!r *Mt ailcaaa la kalaf iaa*raa. u ^r>ivtr t-o l^oaura r*aa rololloraahlM <r ali|MMT M* >aaa- oa caaM-arwriHo aortalltr. la. *aaUa Iraa IM laaaf ttMar (-onauartlian. Siaea 1 kava alraaff aataalaf Uai for tlaaloaia. tarlaiur aludlaa a/a aal likair la I*'ir aaaraaa IVa Mali, altar 1 Smncm aval bo aovfM. Slate* IM Oltfwoala eo* V* aa4a ai ralltar aarlr aiafa, aM Ifca aiaaaaa la aio/tf trr>l>a, ll atftuld la facofnifaO ta>*l Utora will bo o t^Mlaivl lal vafcoc of <rtaft |IK o* atiaaara of ataa::<, vbieb la aol llMaly to raaoit to Itrrtleaal iaj-ai ratal or raoneod iyyotty. v>-*t v *-- 1 ** araaraal la t-H* rtflar l*>li<;a'.aa liat J * . yr.a or t.ijro.; la lala of * a a.s a I a 'K*' i 4 tta it; ik.-iti . - r.' * r r ; ta , aaltoatoaia ia s'.se H*iT to to - a*MAirat:a. to ay ttv>oio4*o. litata l* a* a*ilaaea to ibo contrary. i. ai^aara }aata *tick Ma taa* aiM to protact <roa aasaaiaaia K; *ara aaetaa Uaf caacar ru la oat. . ?>* r-rtli^r laplieaviu* bib follow* la laal ^ * * t : rattottf ` * lo toaj oa a.INar ab*alb*l t ' loaf Caa^ar r l a* if It* /oraal la tatataait u;m *aaaHlaa aa;t.o4al^of > *.c . la bats l&a. a/io* , a<a-at lap {&.** Uaigt aflacu a/lar Ua /re, r i.-.a UUaC) liaa baa aiapaoO Clearly, U Mt si Ik* kM prMftl (*ctr* l\t f r*Ct IN< <IMM MtCOB** (**4 fcy bMlO* >^Okur, 1* tMki^. Tv# uueA <U(*r <r ##ck of tb# lkr# u)or eMUie<Mi #k#(MU, loop corueor Md Mtlt#tls#*. TVoro 1# no l#nr# iMt ##ki r*M# lvftf ftkrMta of t* t|fp# ikit k aiHCtad to k eoofcootf otrwcturolly r rMUeAllr IU u&#imU. Ur U ladood r*lMAM t r< poruUlion t#di# Uat low level prof union of m#H e*citiM * tk cu#c, *f#r. of U typo #o to MftMto#:#, #r be #ocll#d vttb etgorotlo oeootng. In tivot mam, oeoMirug to o confounding influencing foctor wMek iMt bo tobon into accoua: ?\en r* lonMp #r nought between eobeotoo eopoeure and rMllovrt^lc tvlMAC# of MbMloaU. Til# to Mt, of court#, lAe g ' ring that ooMUf to coAtrlbwlinf caum of ##he*ta# ; #; in #r lev, 11 to not. wg w year? (>, Novv.r, . #^uMif c#j## cnrorie long dtoeaee in is# #n#rl $)|>u1#iim. Ta#m co#diu.i #ro oftoo fonortcolly celled c*rontc ot>otructtv lung dteeeeo, coeprlelng prtoortly ctfiAie &rncMtie on* puieonery eaphy##e. wnea they cooaiot tn t#tt# they coo bo ecpoctod to mJaac# Ik# fuaci4on#1 (feet of the occupational im#m, but too duel oapoauro to not lively to No contributed oumuai t i i y to Cil"lC*;iy :gnif;e#nt tirwyt att'.ruCtlon, Cr.# of tan ro4# tn ts* pro## tv#t o#Mi#l# to cnrootc lung dtooooo rMc# to "ciaiinr to oopOyoaoo*. Zo f*ct, U# c 11 n l ce l, rediogrepfcte. potoooory ruActto# rpoyototogter *# (Mtwic fMUr* at uo##tu#t# e#phyee# could rot bo Mr* dtottoet end e-hould oot bo coolly c";JJ# TO* "~ 7 T r.V w^tU - W *** R confvMMt. It ttrtt f non'ttllfntnl rttplrttor^ dtMtM, both aabaatoa and taoklng ar* tiportint ctuttt. While they Ctutt dlffarant dlaaaaaa. th* af ftctt of aaoklng on Lit* airway a and their function* aa w*l1 aa tha a-ray, mat b* takan into account lMfl considering th* relationship batman aabaatoa axpoaura and dlffua* 2un dlaaaaa. Till* can quit* readily ba *ccoapllahad la population atudlaa but la tort difficult to tort out la Individual caaaa. I Zt 1* for lung concur that tb* aynarglaa batman cigarette atohtng and aabaatoa exposure ha* approprtataly racalvad tha gratlatt attention. Our Uforittion on th* rolttlonahip Mtrntn thaaa two cauaal factora coaaa froa th* ralatlvaly fav aortality atudlaa of asbeatoa-axpoaad worker* uhar* sacking nittomt trt tvtiltbia, Tha data lndtcttt that tha Intaraetlon la tort than additive and aay vary wall ba sultipllcattva (th* product of tha two riak factora. *9. in tha inauiator atudlaa, a riak ratio of 10 for aaoklng* 3 for aabaatoa* so for th* cainmauan f boti. factora acting together). While It la clear that th* axtent and pravalanc* of aaokiog la a atudy population, ita varloua exposure group*, and th# coaparlaan or control group* can have an avtraaaiy laportant t((tct on luny c*nt*r *a|w*or-rF*a** c-urvaa, thara la lntufficltnt inforttiion tvtiltbia to allow aao*:ng to ba uaad in quantltat 1v* riak aaaaaaaant for aabaatoaralhtad lung cancar. At praaant. in apldaaiologlc raaaarch, m aaa at boat tttaapt ta cbtrtctcrlM LJu* aaaklag habit* of tKa atudy cohort and attttt coaparabillty In regard to Lh1a 23 p 1 B -------Vmrr - - . Influencing variable between the itudy population and the coapsrlaon <unexposed) population, and between aub-groupa of the cohort which hava baan stratified by laval of axpoaura. Uhila tha ralatlva contribution of aabaatoa axpoaura and aaoking can, with aufficiant lnforaatlon, ba aatiaatad in populations, it la axtraaaly difficult to do ao in an individual with this tuaor, whara both cauaal factors hava baan praaant. Brief comment aaaaa appropriate regarding tha poaaibla significance of iaaunologie abnoraalitiaa which hava baan found in tha blood and calls of aabaatoa-axpoaad or diseased individuals. Investigators have hoped that such findings Bight provide lnforaatlon regarding pathogenesis of these conditions and, perhaps, ba useful in predicting an advaraa response in exposed workara. To data it *aa* that theae lanunoleglc findings are aoat likely to ba tha consequence of tissue injury and appropriately called "api-phenomena", being of little value in either identifying tha auaceptible worker, correlating with tha risk or eevarlty Of disease or providing factors to be taken Into account In generating dose-response relationships. In discussing risk snslysls, I have reviewed the considerable influence of a vtrl'-r of foster* which are llkaly to affect tha measured extant to which asbestos causes allgnsnt and non-Bsllgnsnt dlsssses. These include, but ere undoubtedly not United to: sageant of the industry in which asbestos is ua1> fiber type; physical dlaeneloe of the fiber; choice ef a coapartaon population; differences In follow-up ties in the study 29 population; aaoking habile of tha atudy and control populatlona, and between axpoaura jroupa in tha atudy cohort; quality and for of tha duat axpoaura data and auch aaauaptlona aa ccnvtralon ratloa for total partlculataa to flbara; and crltarla for aacartalnaant of tha haalth raaponaa undar atudy. Zn apita of thaaa laportant aaurcaa of variability, we know of no othar occupational dlaaaaa for which kora coaplata axpoaura-raaponaa data ara avallabla fro* huaan population atudiaa. THE OSHA PROPOSAL FOR AH ASBESTOS STANDARD OSHA haa raliad on a quantitative riak aaaeaament for aarjatoa axpoaura which la baaad on currantly accaptad methodology. Koat, If not all, of the varlablea-dlacuaaed have been conaldered and It la very alallar to the rlak analyaia produced by tha Chronic Hazard Adviaory Panel (CHAP) on Aabaatoa of CPSC. There la not, nor la It likely that there aver would be, complete agreement on all underlying aaauaptlona end declalona, concerning, aoat notably: choice of atudlea for determination of expoaure-reaponae alopea for lung cancer and aeaothelloaa rlak, differential rlak related to fiber type, riak gradient for differing portlona of the lnduatry, and whether to include rlak of gaatrointeatlnal neoplasia In the analyaia. - However, on much laauea, coaproaiae and functional conaenaua haa generally evolved. No algnlflcant differencea have emerged In 30 '.V4 choice of models. At iott, changes in the assumptions which Z end y colleagues eight Bake in the riek enalyeie, would reault only in lowering the eetieated exceu deatha (lifetiae risk) reaulting free aabeatoa exposure by a factor of two, under identical conditlone of age at firat expoaura, duration of eaployaent and level of expoaure, and. If riak gradianta by fiber type and proceaa are ignored. With thoae caveata, and conaidering ell of the uncertainties readily^ conceded "in the proceaa*, Z can accept tife OSHA r4ak aaaeaaaent aa reaaonable and aupportable. The regulatory choice of a paraiaaible expoaure limit (PEL) for aabaatoa clearly extanda beyond the acope of bioaedieal acienca or public health. Such factora aa technological and econoaie feaalbility (available approachea and coat of riak reduction), measurement validity, work practicaa, peraonal respiratory protection (versus engineering controls), and evaluation of comparative risks all require broader input. These considerations aside, the residual risks associated with 43 years of exposure to 0.2 or 0.3 fibera/el., under conditions of fiber type use end processes constituting past exposures (7 and 17 excess deaths per 1,000 workers over their lifetime in the OSHA risk assessment), ere not easily defended by thoae committed to reduction of workplace hazarda. Obviously, the non-health related factora cannot be ignored, as evidenced by the OSHA proposal. Also, there are additional considerations. Z do not believe that all exposures to aabeatoa reault la the same riak to workers. I have reviewed the evidence which 31  ic-ivviiW.*. & .'. <`.V-t'-:_2V f. 4 wa IV-- ' *^ .1 ' rwS V* 'A indicates that (xpotur* to different fiber type*, and in diafclncrt part* of the induatry, haa producad diffaring iavala of riak in workara. I baiiava that thia aclantific avidanca ia strong, although by ita nature, navar concluaiva. It claarly falla undar the rubric: "beat available**, upon which policy daeialana ira aoat oftan taken. Thar* will, of eouraa, ba conaldarationa, falling within tha expertise of dlaclpllnaa othar than biomedical cianca, which will, and ahould, eontrlbuta to tha ragulatory *policy which OSHA ia formulating, in part baaad on these haaringa. Houavar, I would ba raaiaa in ay raaponaibility in thia rula-aaking prsecdura if I did not pravida judgments on policy, which Z hava concludad ar* aupportad by tha avallabla aclantlfic avidanca, sties again ra-atatlng ay recognition that final declilona will ba baaed on broader considerations. I find it difficult to justify the continued uaa of aaphibole aabeatoa, crocldollte and aaoaite, when it can b* avoidad. Demolition and othar construction xp8iura to these fibers will, of course, b* unavoidable in tha foreseeable futur*. Unacceptable risk haa bean daaonatratad or aatlaated at Iavala of expoaure that ara probably lower than can practically be attained, *o that diacontinuing all uaa of thaaa fibera in the manufacture of new producta and aiailar introduction in tha workplace, ahould ba the desired regulatory objective. How thia la to ba aehiavad, Z will leave to othar*. .. . ' . . 32 Aa indicated, the avidanea alao allsua evaluating the rimk gradient* which heve emerged In relation to procaaa. Mining and allling expoeurea are not geraane to theae proceedInga, and will not be conaldered further. The manufacture of aabeatoa taxtllea probably reaulta In an unraaasnably high rlak and should be regulated aoat atringently aaong aanufacturlng processes, perhapa to the point where continuing viability of thia portion of the lnduatry la doubtful. Under the above aaauaptlona of exclualve chryaotlle uae and aanufacturlng proceaaea Halted eaaentially to aabeatoa-ceaent producta and friction materials, the analyaia of riak cited previously should ba considered an a substantial over-estimate. It then becomes probable that a PEL for aabeatoa of 0.*5 would result in a potential rik which is not unreasonable. Should a differential regulatory approach be rejected, adequate riak reduction sight not be achieved, even at a PEL of 0.2 flbera/sl., although non-scientific reasons say sake this limit the lowest "feasible" one which can he promulgated. It should not go unnoticad that othar governments, based on the conclusions of their advisory groups that all asbestos risks were not the ease, have opted to follow thia CQUrsi. Of recant interest in this regard, because of its thoughtful, thorough and overall exemplary approach to public policy In the aabeatoareleted disease leauee, ia the superb report, published in May of thia year, of the Ontario Royal Coaalaeion oa Aabeatoa. Zn addition to Canada, other countriaa regulating aabeatoa according 33 r,T``V. * ~=->l to fiber type are: AuatrtUa, Belgium, Danmark, Iraland, thm Unltmd Kingdom, Italy, Japan, Haw Zealand and Norway. van in tha U.S., wa hava recognized differing rlaka by banning a numbar of uaaa of eabaatoa (ag. apraylng of aabaatoa lnaulation). Furthar, SHA haa pravloualy aat diffarant PEL'a for aaparata parta if tha cotton lnduatry, and, indaad, for diffarant joba In tha taxtlla portion of that lnduatry. X would ancouraga tha Agancy to conaldar a aimilar approach to tha regulation of aabaatoa. MEDICAL SURVEILLANCE OF ASBESTOS EXPOSED WORKERS Finally, I would Ilka to direct ay attention briefly to r rulu covering medical eurvelllence of exposed workers. As K s indicated earlier, aabaatoala la a alowly progressiva diaaaaa, and, due Po the aiibat.ant.lal ly lower expoauraa of the laat two il $ h decades, the extent or severity of this disorder la currently, ii and will continue to be in the future, moat often minimal to l eodest. Specific treatment is not available and ahort term g Lncrtx.nial expoauraa at current operating laveia are not likely to hava a ssssurabls affact on progreaalon of tha diaaaaa. For thaaa raaaona, and tha general precept that all unnecaaaary irradiation ahould be avoided, I recommend that cheat x-ray filma he mandated at a three yearly interval, e change fros the current requireaent of yearly filaa. I would not favor thia change if medical evidence ahowed that annual cheat filma aignificantly Improve prognosis whan a malignant tumor la diacovarad on routine x-ray aurvai 1 lsnes-- this la, unfortunately, not tha came. V*. f5 34 ' i\v* -t: :yXV i|t 4 The eliciting of reapiretory ayaptoaa and parforaanca of aplroaetry r laea of banafit In aabaatoa-axpoaed workar* beeauae of their apeclficity (thay ara non-apaclflc in regard to expoaura-ralated effeeta, primarily aabaatoaia) than for thair uaa in aaking tha workar and hia phyaician awara of a dapartura froa raapiratory haalth, aoat coaaonly chronic airwaya obatruction, dua to chronic bronchitia or pulmonary aiphyaeaa. Whila annual ayaptoa lnvantory and .pulmonary function teata ahould ba conaidarad part of good ganaral madical aurvaillanca froa middla aga on, particularly in high riak groupa, much aa amokara, tha ijor banafit to ba axpactad ia tha auccaaaful counaelling of the early obatructad individual to discontinue amoking. For the limited purpoaaa of occupational haalth monitoring, theaa proceduraa could alao be raquirad only once every three yaara. No new additional madical proceduraa are juatifiably mandated fur incluaion, at thia time, in the surveillance program. 33 trr\wipwiwec: H DATE CONVERTED TO MICROFICHE *: -:*"a|"3