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4^ \ ' 'H V' I = Vv>% :< r v w -. v' . -t.4 (, ^ h>v'"^V."v`'.*vf'; t1-Kv-cj.vr.;^^->yf;l#J*/twvi ,4-44* 4-y.-VC4` . .' . * -V * * ., Ji. n _ -1 'a* ,<- 4 .:'..**:/-y... ;A< 4, ',:. :; '.'Y^'-rV-jJ-.-'.-u' ' . i;:y-, --;r~.::',-,^'.r<-: .'-''. ;.t'V.-! ;,i>'-;.!:.r,-';::,; *.'-^.:5.'i-'.''r\.^r.,vT,. .v /.v< '.':;V-:.4.;1 -y 4.'; j; .'.i-' x.v,,v4yyy4y'''4'-,;; Vr' -1- .'-->4" " . ''4' ``rt. 1 ./aJ" '>sir'_*v' *t ;--''4'l,* -.*V:.s ,-if,rW: .,*;y- v --V- ' ^wiv '.-v' i,'--V'HW 'f?2, - - h1 |i! ,ii 1 7S Annals New York Aeademv of Sclenues ^ /?s-/7f ffrrc-j onctii t 906frU svu ckissie chronic loxicily and luniortgcncsis until the mechanisms tor both arc CASt STUrW 4: I completely understood for a specific chemical substance. The scientific literature is replete with demonstration of tumor induction in animals exposed by one LEK5L ,APPRO< OCCUPATIONAL or more of several routes to a large variety of chemical substances. Although even one such finding should immediately alert industry and governmental agen Hector P. Blcjcr, cies alike to a possible problem, certainly in-depth review and critical evaluation is necessary prior to establishment of mandatory control standards by such agencies. Such in-depth review requires that all available information and data bearing on the problem be considered and evaluated on their merits. Certainly degrees of carcinogenicity do exist, and it is entirely possible that 1 Notional institute for Otici Department of Heaitfi^ * Cincinnpti i Salt Lake: thresholds for tumor induction may exist. Until such time as this hypothesis is proved, however, only the most stringent of control measures will suffice to assure that employees are adequately protected from chemical substances con sidered to be potential human carcinogens. The assessment of carcinogenic iI I potential for a specific chemical substance must include the consideration of published information, monitoring and control data from affected industries, and the in-depth, epidemiologic experience of affected employees. Negative experience in industry regarding the incidence of cases of human cancer must be considered in proper perspective, not only in terms of pure versus mixed exposures and adequacy of statistical data, but also in the light of the proven experience in the dyestuffs industry that the average latency period for develop ment of bladder cancer is approximately 20 or more years. With these considerations in mind, it is necessary to reflect that the final decision in promulgating an occupational exposure control regulation must be that standard ". . . which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will sulfer impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life." (Occupational Safety and Health Act of 1970.) 4- Arsenic, known and used since i which is truly ubiquitous from botj estimate is that in the U.S.A, atofi^ are potentially exposed to inorganic) fi ` i- . HtSTOij r In 1820, 45 years after Pcrq|V J. A. Paris ascribed the first*^a occupational. While practicing iP$Ej that . . a cancerous di$easc|ihy chimney sweeps . . occasionaH; fumes of a local copper smelting^ and Paris' original specific observat\ a subject of dispute and controy clinically that occupational conta?^"'1' cancer--particularly among sheep.--,. sodium arsenite, a veterinary pc^Ucm . medical or environmental ursenic^llcxc well established by 1V30A Medical reports had postulates cancer among sheep-dip worker^ scnicalsA The first strong imp| tional exposure to these arsenic^ when four falal eases of Iung.canc sheep-dip workers.'* The above evidence pronipj tional group exposed to in^rg^ ported on a study of the mortal}] arsenite sheep-dip, a topical,v^ter (1975), ten cpidi liologicalstildil lfCOa Lassiter: Vinyl Chloridc- -Best Available Tcchnoloj: CASE STUDY 3: VINYL CHLORIDE- ^<2/3 BEST AVAILABLE TECHNOLOGY Donald V. Lassiter Occupational Safety and Health Administration United States Department of Labor Washington, D.C. 20210 Because one person out of every four in the United States dies of cancer, it is of great concern that most estimates of the proportion of cancer induced by environmental factors arc in excess of 5(Kc. Boyland. in the United Kingdom has further estimated that 90Ct of all human tumors result from the action of chemicals of environmental or endogenous origin, with the remaining 10% induced by viruses and ionizing radiation. The significance of these estimates for the occupational environment, as well us similar estimates made here, is quite clear; long-term exposure of employees to carcinogenic chemicals must certainly increase risk of cancer. Yet, in only . a handful of instances has this general conclusion been amply demonstrated. Explosive revelations such as those which characterized the finding that vinyl chloride induced angiosarcoma of the liver in exposed workers arc very rare, at least for the present. Few would dispute the conclusion, however, that if those employees who contracted this fatal liver tumor had not been exposed to vinyl chloride, the probability of their contracting this rare disease would have been infinitesimally small. Absolute, picvention of this particular tumor could have been assured if substantial exposure to vinyl chloride had not occurred. The increase in incidence of urinary bladder cancer among aromatic amine dycstulTs workers has been well documented. The greatly increased incidence of mesothelioma among asbestos workers and of "oat cell" carcinoma of the lung among chloromcthylalion workers represent still other instances of occur rence of rare cancers in much greater frequency among exposed workers than ' among the general population or unexposed cohorts. The truly alarming common feature in each of these instances has been retrospective recognition of cause and effect some twenty or more years follow ing initiation of exposure. During these periods of latency, many more tumors undoubtedly have been initiated and now only await clinical verification. Un fortunately, such experiences have been necessitated in the past to demonstrate clearly the need for exposure controls. We must not, however, permit the "body count" mentality of the Viet Nam era to find new acceptance in our nation's workplaces. The situation is not so simplistic, however, as to suggest the immediate, total elimination of all chemicals tainted with suspicion of carcinogenic potential in order to assure an exposure-free working environment. Socioeconomic benefits lu he derived from large-scale ^hcmtcal productionJ activities for the individual employed in this industry as well as his employer and the nation must be considered. Such considerations, however, are valid, from the standpoint of occupational health, only to the extent that they may affect -.Vi r - " 176 - decisions concerning substitution or elimination of substa 4 be only weakly tumorigenic. In instances where carcinogcMpbxuj of a chemical is established, the overriding considcrationoMncfjT' be whether he can remain competitive in a situation in \\hich'c'os controls must be., instituted as required by stringent regulations control exposure, and which will assure minimum employee risk'q Differences between situations involving absence of controls,'rrii trols. or stringent controls depend principally on substantiality ofge dcncc available to support regulatory decisions. Where such evident oc.ii, regulatory controls must reflect the current state-of-the-art In coti the following principles of carcinogenicity: . 1) realization of a period of latency, possibly of 20-30 years;^. induration; 2) possibility of extremely low threshold of species or individual: 3) possibility of metabolic modification of parent chemical subsI unidentified proximate or ultimate carcinogenic metnbolitets}; 4) additive or synergistic effects of concomitant workplace expg other agents or factors, including cigarette smoke. .: In the preamble to the rule promulgated on October 4 by the Oqcjip Safety and Health Administration (OSHA) regulating occupational*^ to vinyl chloride, four important policy determinations appear that s?!l' stage for future regulations involving occupational carcinogens: 1) ". . . the demonstration of cancer induction in humans at ap level is not a prerequisite to a determination that a substance^ a cancer hazard for humans at that level. rAW 2) "It would be imprudent to assume man lo bo less sensitive chloride exposure than experimental animals in the ahsencj sive evidence. ` 3) . . the precise level of exposure which poses u.hazdrti| question of whether a `safe' exposure level exists, cannot be d answered. . . . Nor is it clear lo what extent exposures.can. reduced. We cannot wait until indisputable answers to Ihcfa arc available, because lives of employees are at stake. IThc have had to exercise our'bcst judgment on the basis of the evidence. These judgments have required a balancing process? the overriding consideration lias been the protection of empl(jji r those who may have regular exposures to VC' throughout thei v> lives. 4) . . (the exposure limit of 1 ppm) is based on evaluation available evidence and on a judgment .that the health and^ iV employees must he protected lo the fullest extent feasible," "*!l J Mechanisms of carcinogenesis arc far from being completely compr and fully understood, and the many variables surrounding occupational genesis serve to cloud the situation further, even when a specific agent is A more important aspect concerning occupational cancer must be rC f of cause and effect, at least from the standpoint of control measures,, h i associated with occupational exposure to a specific chemical substance? considered not only from aspects of acute and subacute toxicity, but af \ the potential to induce tumors. A clear distinction cannot be drawnf W" R&S 114905