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"Literature Update on Potential Health Effects Proa Exposures to Polychlorinated Biphenyls and Related Chlorinated Hatarocycl.es" Prepared by Victor A. Drill, M.D., Ph.D. Seymour L. Friesa, Ph.D Harry w. Hays, Ph.D. Ted A. Loomis, M.D., Ph.D. December 20, 1983 HONS 015780 TABLE Of CONTENTS Executive Summary......................................................................................... I. Introduction............................................................................. II. Yusho Episode........................................................................... III. Body Buedene, Metaboliea andKinetics........................ IV. General Toxicity,.................................................................. V. Dermal Effects............................................................. VI Effects of PCBs on Liver.................................................... VII. Gastric Lesions....................................................................... VIII. Carcinogenesis: Experimental........................................ IX. Reproductive Effects............................................................ X. Mutagenesis................................................................................ XI. Other Health Effects............................................................ XII. Epidemiology.............................................................................. XIII. Recent Findings on Health Effects of Polychlorinated Dibenxofurans........................................ XIV. References.................................................................................. 1 8 11 17 26 11 1] 35 3S 44 45 47 53 60 72 HONS 015781 Executive Summary This addition to a previous study of tha available biomdical literature on potential health effects of the poly chlorinated biphenyls (PCBs) and related Impurities is essen tially an update froai literature and other data retrieved during late 1981 and up through November IS, 1982. As in the first study, the review and conclusions were formulated by a Category I team from DFHLas, Inc. and subjected to a second level review and critique by an independent Category II team. The comsMnts and suggestions from the Category II review have been incorpo rated into the final revised text of this annex, for which DFHLas, Inc. takes full responsibility. All new conclusions for each specific health effect in test animal systems and human populations are discussed in the context of both the new studies reviewed and conclusions from the previous report material based on the earlier literature. A summary of thm major new findings and conclusions with respect to specific health effects resulting from PCS exposure is given below. Also included is a summary of observations on health effects attributable to exposure to polychlorinated dlbensofurans (PCDFs) in test animal models and humans, for this same literature retrieval period. 1. Recent findings on the health status of Individuals previously exposed to the mixtures of PCBs, PCDFs and PCQs MQNS 015782 I' (polychlorinated quaterphenyls) In the contaminated rice bran cooking oil* consumed during the Yusho episodes in Japan (1980's) and Taiwan (1970's) have served to emphasise and re inforce two points made in the 1982 report. First, it appears that elevated PCOF levels in the cooking oils may have been a principal causa of the enhanced toxicity of those oils over that of the parent commercial PCB mixtures originally charged into the heat exchangers. Second, because of the mixed PCBi PCDFi PCQ content of those oils, the Yusho episodes are not appropriate models for prediction of human health effects from exposure to commercial PCB mixtures. 2. New findings in test animal models and exposed human populations have served to emphasize distinct species specificity in biological processes of tissue metabolism, distribution and excretion. The residual concentrations of PCB congeners in fatty and other tissues are seen to be par ticularly dependent on ease of metabolism and subsequent excretion of polar metabolites, free or conjugated, from specific congeners in commercial PCB mixtures. 3. In the domain of acute toxicity of PCBs, recent attention has been focused on< (a) the substantial toxicity of 2,3,6-hexa C8 (chlorinated biphenyl) in inhibition of growth of a mouse embryo cell linei and (b) the marked hepatotoxlclty of the 3,4,5-hexa CB congener in young mice. The latter was a rare congener in commercial PCB mixtures. MOWS 015783 -3- These finding* do not alter significantly the generalixations on structure vs. toxicity in the 1982 report. 4. Dermal effects in humans attributable to expoaure to PCBs and related Impurities are of continued Interest, even though most of the rare cases of chloracne found in PCB-exposed Industrial workers ace not severe and not long-lasting after exposure has stopped. Such signs were particularly severe and long-lasting in certain of the Yusho poisoning patients. The most recent evidence reviewed by Kashimoto et al. (1981) for chloracne in Yusho victims points to the enhanced levels of contaminants such as ths PCDPs in the rice oils as primary factors in ssvere chloracne, 5. Recent results on the potential impact of PCB ex posure on liver structure or function have derived from an experimental study in the rat and an epidemiological study of capacitor workers. It appears that Aroclor 1254 does not in duce benign liver lesions (hyperplastic foci, nodular hyper plasia) in the male Sprague-Dawley rat, and that extended ex posure of people in the electrical industry setting to various Aroclors has not resultsd in findings of significant liver dysfunction or disease. 6. In two studies, gastric lesions were observed in rats and monkeys receiving Aroclor 12S4 orally* such lesions hsve not been seen in occupationally exposed human populations. HONS 015784 4 In the rat, at aitaa naar tha glandular stomach that vara high in alkalina phosphatase, an increasad frequency of occurranca of cyatlc lntaatlnal mataplaala was observed. in tha monkay, tha principal finding in tha atomach was hypertro phic and hyperplastic mucous gastrophy. These are noncancerous lesions. 7. Studies in the rat using Aroclor 1254 and focused on potential carcinogenesis in chronically exposed rats at target organs such as liver, bladder, stomach and intestinal tract have proven essentially negative, in our opinion. The recent reevaluation of rat stOMch tissues from an MCI bio assay (1978) by Morgan at al. (1981) did not result in a sta tistically significant, dose-related increase in the numbers of stomach adenocarcinomas observed. However, the finding by Preston at al. (1981) of a possible tumor-promoting effect of Aroclor 1254 in the Sprague-Dawley rat is judged as biolog ically significant and requiring further investigation. 8. a new study has evaluated the effect of Aroclor 1254 on reproduction, the compound being administered in concen trations of 25-900 ppm in the diet of female rats during days 6-15 of gestation. Noted weret (a) decrease in placental protein and glycogen* and (b) decreases in fetal weight and survival rate. Since decreases in food intake were also noted, resulting in reduced nutritional status and a decrease in weight gain, attribution of the placental and fetal effects MONS 015785 -5- to either direct PCB action or to altered nutritional state cannot clearly be made. 9. Recent test results on mutagenic potential of PCBs in Ames tests with Salmonella systems in vitro, with or without metabolic activation, have been negative. 10. The ability of Aroclors to induce a variety of micro somal enxyme systems in test animal tissues has been widely documented. A new and unexpected finding in this area of bio logical activity has been negative! Aroclor 1254 leads to a decrease in microsomal enxyme content of P-4S0j in rabbit lung, rather than an Increase, with no alteration in P-450Xi content. On the positive side, Aroclor 1254 causes the induction of glucuronyl transferases and inhibits the release of polymorphonuclear glucuronidase from leucocytes. These biological actions have not been related to human disease states or dysfunctions. 11. Recent experiMntal studies have shown that immuno logical effects in test animal systems exposed to PCBs and in Yusho victims exposed to mixtures of PCBs, PCQs and PCDFs can Indeed occur. Humans exposed to Yusho oils and monkeys exposed to synthetic mixtures of PCBs, PCQs and PCPPs show signs of immuno-supprssslon or alterations in immunoglobulins and T-cells. Immunogenic alteration or lmmunotoxlcity have also been observed in rabbits and mice dosed with PCBs. How HONS 015786 ever, th evidence to data doaa not point to a dlract. doeetalatad effect of FCBe alona In exposed human populations, axpraaaibla aa a change In immunological competence. 12. Tba new epidemiological study of Lawton at al. (1981) on electrical industry workars, takan In conjunction with othar racant studlas on workars occupationally axposad to PCBs, laads to additional insights in the araas of skin problems, lipid metabolism, pulmonary function, blood glucoaa lavals, blood uric acid levels, and general complaints and symptoms. The Lawton study found no signs of chloracne, past or present, and no dermatological findings specifically re lated to PCB exposure. Associations were found between blood levels of PCBs and serum triglyceride levels in exposed per sonnel. The Lawton study extends previous conclusions that PCB exposure under occupational conditions does not lead to signs or symptoms of clinical disaasa, despite the presence of normal incidence rates for symptoms associated with inter currant disease and/or general stress. Further, the Lawton study did not reveal any abnormal findings with respect to pulmonary function in PCB exposed workers, or any changes in either fasting blood glucose levels or serum uric acid levels vs. those levels in control populations. 13. In the domain of potential behavioral effects attri butable to PCB exposure, several recent studies are of inter est. In offspring of rats given prenatal treatment with Kanechlor 300 and $00, and of monkeys dosed with Aroclor 124B HONS 015787 -7- ln th diet during pregnancy, signs of decreased learning ability were observed. Offspring of mice after prenatal and postnatal exposure to Aroclor 1254 showed a latency period in making responses, following training in an avoidance response pattern. These behavioral manifestations of PCB exposure in animal models have not been related to any poten tial behavioral changes in exposed human populations. 14. The PCDFs have been studied with increasing Interest in recent years as realization grows that they are toxic derivatives of the PCBs and may be Important contributors to the toxicity of mixtures in which they are present if their concentratione are at high enough levels. In recent animal studies they have been shown to be powerful aryl hydrocarbon hydroxylase (AHH) Inducers, especially when the lateral 2,3,7,8-positions are fully substituted by chlorine atoaM. They produce many toxic signs in test animal systems at doses in the ug/kg/day range. Including severe skin changes, swollen eyelids, enlargement of meibomian glands, squamous metaplasia, hyperplasia of the gastric mucosa, thymic Involution, hypo plasia of the bone narrow, and hepatotoxicity. Aside from continued analysis of residual health effects in Yusho pa tients, in which the opinion is growing that the PCDrs are principal contributors to the persistent toxic syndrome ob served, no human PCDF exposure vs. effect Information has been documented in the 1981-1982 interval. HONS 019788 I INTRODUCTION A study on the potential health effects docunantad in tha literature through 1981 for human populationa, from axpoaure to commercial polychlorinated biphenyl (PCS) mixtures under occupational or other environmental conditions, vaa completed by thla firm In 1982. Entitled 'Potential Health Effacta In the Human fromExpoaure to Polychlorinated Blphenyla (PCBa) and Related Impurltlea*. the atudy (hereafter labeled aa the DPHLS report), was aponaored by tha Edlaon Electric Xnatltute (BED and the National Electrical Manufacturera Aaaoclatlon ((IBM). The literature coverage In that atudy Included Important toxi cological and epidemiological papera generally available through the middle of 1981. It was iaaued under a date of rebruary 12, 1982. Since many important PCS atudiea have appeared In publlcatlona or preaentatione alnce mid 1981, an update of the DPHLS atudy in the form of an annex waa deemed adviaable by both sponaora. The present document conatltutaa that updated annex to the 1912 DPHLS report. It covera literature retrieved from library and other sources up to a cutoff aearch data of November IS, 1982. Aa in the original DPHLS atudy, the preaent annex was constructed in draft by a Category I team composed of members of this firm (Drs. Drill, Prlesa, Hays and Loomis), reviewed HONS 015789 9 for contone and with suggestions for revision by two external peer reviewers (Drs. Standaert and Alvares), and finally revised by the Category I teas which takes full responsibil ity for Its content and conclusions. The annex Is cast in a format which largely tracks the original report, section by section, In the sequence of health effects. For each effect, the results of new toxicological and epidemiological studies are considered, and then reviewed in the framework of results cited in the 19(2 report to reach judgment on the possibility of occurrence of that effect in exposed human populations. Also included in the annex are sections dealing with recent publications on behavlorsl affects attri buted to PCB exposure, and with new findings on potential health effects from exposures to polychlorinated dlbenxofurans (PCDFs). It is of considerable Interest that modern receptor theory has been brought to bear on interpretation of health effects of of PCBs and related compounds. It is possible that manifes tations of toxicity may result from a. common initial path way of interactions of certain PCBs, PCDFs or PCDDs with tissue elements in massaalian organisms. In particular, recant interpretations of experimental findings in test animal systems have centered on the possibility that one or more receptor pro teins may be involved in initial binding of a suitably substi tuted compound leading to ultimate expression of a biological MOMS 015790 10 activity auch as chloracne or thymic involution. in this picture of events, under a theory proposed by Poland and Knudsen (1982) and Nebert et al. (1981), the effects stesmng from exposure to a given polychlorinated molecule would be tra ceable to Initial binding to an inherent receptor surface whose structure and location in tissues are genetically controlled. Such binding could occur broadly across mammalian species and strains, providing a unifying basis for correlating phenomena of many types in different species. The PCBs as a group are considered to be the least potent in this binding - mobili zation process, the PCDFs orders of magnitude more potent, and the FCDDs the most potent of all. The receptor substance itself is thought to be regulated genetically, and to be cyeoplasmic in location. if the receptor is induced by a given stimulus and triggered by binding of the agonist, the mobilization of the endogenous transmitter substance could then account under this theory for hyperplasia at a variety of cutaneous and hepatic tissues. Involution of the thymus, and metabolic derrangements leading to lesions of chloracne. The theory is presently quite useful, in the material that follows, in efforts to under stand phenomena that extend across many species and are triggered by specific molecular structures in the PCB and PCor families of compounds. HONS 015191 11- II. YUSHO EPISODE Since the occurrence of the 1968 Yusho episode in Japan involving consumption of Kanemi rice bran cooking oil contain ing PCB, PCQ. and PCDF impurities which were accidentally leaked into the oil from heat exchanger colls originally charged with Kanechlor 400, the medical follow-up and history of recovery of these patients has been persistent and well documented. Yoahlhara and Yoshimura (1981) have recently reviewed residual health effects from this intoxication episode, as seen in medical examinations made over the past decade. In general, most of the clinical symptoms from this bran oil intoxication have diminished gradually, accom panied by a decrease in blood PCB levels to a mean residual of 7 ppb (vs. a mean level of 3 ppb in control subjects). Since the estimated average total intakes of PCBs, PCQs and PCDFs in these patients during 1968-1969 amounted to 633, 596 and 3.4 mg respectively (Yoshihara and Yoshimura, 1981) the persistence of traces of markers of the original intox icant load in the circulatory systems of these individuals after a 15 year period la striking. Perhaps steaming from residual body burdens in storage tissues, this occurrence of traces of marker substances in blood has bean accompanied by the persistence of certain symptoms, e.g. subcutan eous cyst formation, pigmentation of the skin, eyelids and gingiva, eye discharge, and abnormal changes of the tarsal gland in a relatively small number of severely affected Japanese patients. mows 015792 12- Considerable variance has bn rcorded in estimates of PCS, PCQ and PCDP intakes in patients and in oil samples from the Taiwanese episode. In a very recent analytical study, Hasuda et al. (1982) have reported on analyses for PCB, PCQ, and PCDP congeners in the 1979 Taiwan Yusho oil, and in the blood of Taiwanese patients sampled several months after the onset of symptosis from that episode. The levels in oil and blood were compared with those from the Japanese Yusho epi sode of 1968, except that blood samples from Japanese patients were taken 5 years after that poisoning episode. It was found that! (1) the concentrations of PCBs in the Taiwan oil (60-100 ppm) were 10 percent or less of that in the Japanese oil (900 ppm), but the concentrations In the blood of Taiwanese patients were about ten or more times those of Japanese patients. These results follow from the ingestion of higher amounts of oil by the Taiwanese (about 12.3 kg per person vs. about 800 ml for Japanese consum ers), the net ingestion of about equal amounts of PCBs by the two populations, tho longer tima interval for metabolism/ elimination by the Japanese, and the fact that the Taiwanese oil had a higher proportion of more highly chlorinated congen ers. (2) The Taiwan rice oil contained a much lower concen tration (90-180 ppm) of PCQs than did the Japanese Yusho oil (800 ppm). (3) Both the Taiwanese, and Japanese oils con tained PCDFs, chiefly 2,3,4,7,8 - penta CDF and 2,3,4,6,7 penta CDF, which were also detected in the blood of Taiwanese HONS 015793 -13 patients. In view of previous finding* by these invastigator* that 2,3,4,7,6 - penta CDS is one of the moat accumula tive congeners In the livers of humans, monkeys and rats, and Is very potent In its biological actions (F-448 Induc tion, thymic atrophy or liver hypertrophy), kasuda et al. (1982) conjecture that this congener may well be one of the most important etiologic agents for the Yuaho poisonings in both countries. Yoshlhara and Yoshimura (1981) also take note of the in creasing body of evidence implicating the PCDr component in the Japanese Yusho oil as an important contributor to the total toxic syndrome. Further, they cite supporting experi mental data in the rat with a variety of PCDP congeners, given at single doses in the range 1-10 mg/kg, which included significant lowering of thymus weight, increase in liver weight, and retention in liver of large fractions (20-974) of the administered PCDP congener* that contain 5 or 6 Chlor ine atoms per molecule. Magayama et al. (1981) have also contributed to the data base on possible contributions of the PCDF component to the Japanese Yusho syndrome, from experiments on controlled heat ing of Kanechlor 400 which parallel the cumulative heating cycles characteristic of the use of this fluid in a metal heat exchanger. In the presence of metallic iron, nickel or stainless steel end a small aanunt of water contaminant as HUNS 015794 14- an oxygen source, heating at 300*C {or seven weeks leads to an Increase of PCDF content In the Kanechlor to levels of 240-560 ppa> further heating at 350*C for four more weeks led to enhancement of PCDF content to 610-740 ppm. The possible role of PCDFs as a principal agent in Yusho poisoning has been studied in detail by Kashimoto et al. (1981). This work was based on comparative health effects observations on a group of 56 patients in the Japanese epi sode, IS Yusho patients in the Taiwanese event that occurred about ten years later, control populations, and groups of workers occupationally expoaed to PCBs in Japan and Taiwan. Kashimoto et al. have presented analytical data on relative PCBs PCQs PCDF residual levsls in liver in Yusho patients from the Japanese episode, showing relatively high retention of PCDFs in that tissue (PCBss PCQs: PCDFs - 100:76:20), and on concentrations of these components in several samples of the toxic Yusho oils obtained during the two separate but parallel intoxication episodes. From their data analyses, Kashimoto and colleagues concluded that the PCDFs in the Yusho oils were the major pathogenic compounds contributing to the developSMnt of the Yusho syndrome In the Taiwanese patients, despite their low levels in blood compared to those of the PCBs and PCQs (PCBs: PCQs: PCDFS 500:160:1). This conclusion was based principally on the following points. 1. The clinical manifestations and duration of Yusho symptoms were disproportionately more severe and MOWS 015795 -15- perslstent In consideration of the blood Pcb levels observed in Taiwanese patients than in PCB - exposed populations of industrial workers with considerably higher blood PCB levels who had much more benign or mild clinical syndromes. 2. PCDPs show a marked tendency to accumulate in the liver, which could well explain the frequent initial finding of jaundice and other serious abdominal symptoms in Yusho patients and the absence of such changes in people occupationally exposed to PCBs. 3. Prom biological dose vs. response data for a series of toxic effects in many test animals, including the chick, monkey, mouse, and rat, it is apparent that the toxicities of PCBs and the derived PCQs are of the same order of magnitude, but that the toxic potencies of PCDPs are greater by factors ranging from 100 - 10,000. Finally, Chen et al. (1901) have analyzed the toxic con taminants in a Taiwanese Yusho cooking oil that was ingested by approximately 2,000 people. These investigators studied six samples of the oil, both for total PCB and PCDF content and for the distribution of congeners in each family of cose- pounds. They found that the distribution in the PCB fraction favored the more highly chlorinated structures MOMS 015796 -16- (panta-CBi tatrai haxai haptai trii - 47s30:1616il), and that tha PCDF conganara vara moatly of tha panta - cor and tatra CDF vatlaty with only minor amount* of haxa - CDF and tri - CDF. Thin diatribution of componanta dlffars from that in Japanaaa Kanechlor 400, and would ba in accord with more laating Yuaho aysptoma by paraiatanca in tiaaua atoraga of mora highly chlorinatad molacular apaclaa that ara laaa actlva matabolically and laaa likaly to ba axcratad aa polar matabolitaa or thair conjugataa. Diacuaalon and Conclualona Thaaa racant findinga, aapaclally aa thay hava focuaad incraaaingly on tha potantial rola of alavatad lavala of PCDFa in contaminated cooking oila aa tha principal contri butor to tha Yuaho ayndroma in tha Japanaaa and Taiwanaaa intoxication apiaodaa, aarva to amphaalze and rainforca polnta mad* in tha DFHL8 analyai* of aarllar atudiaa. Flrat, haat axchangar action on PCB fluid* laading to alavatad PCDF lavala contrlbutad . to tha enhanced toxicity of the Yuaho cooking oila over that of the parent commercial PCB mixture. Second, bacauaa of the unique PCSiPCQtPCDF diatribution of the Yuaho oila, it ia not correct to ua* the** intoxication apiaodaa aa modal* of acuta or aubdhronic PCB poiaonlng in human*, or for prediction of human health effect* from expoaura to commercial PCB mixture*. HONS 015797 -17- III. BODY BURDENS, METABOLISM AND KINETICS A. Animal Exparlmantx In continuation o studlaa on tha biological fata of Individual PCB conganars in animal modala following admini tratlon of a singla doaa of a radiolabalad compound, Slpaa at al. (1982) hava raportad on tha dlatrlbution, matabollam and axcratlon of 2,4,5, 2',4',S'- haxa-CB in tha baagla dog and tha cynomolgua monkay by following tha lavals of 14c labalad matarial in axcrata, blood and tlasuaa for up to 15 days in tha dog and 90 days In tha monkay. Thasa worksrs obsarvad tha ratas of alimination of this parsistant haxa-CB from thasa tast animals. Elimination from blood occurrad as a blphaslc klnatic procass. Aftar tha first rapid phasa, tha slowar tarminal alimination from blood was charactarlsad by rata constants that wars thraa tlmas as graat in tha dog as in tha monkay. Tha kinatics of axcratlon of tha PCB in tha two spaclas also diffar markadlyi by IS days tha dog had axcratad 66 parcant of tha dosa, mainly in tha fecas, wharaas tha monkay in a 90 day intarval had axcratad only 18 parcant of tha doaa. Tha ramaindar of tha doaa in both spaclas was found largaly as tha parant compound in adiposa tissua and skin as tha major storaga dapot. Furthar study on biliary axcratlon of tha haxa-CB in tha two spaclas again showad that axcratlon procassas in tha dog ara faatar than in tha sronkay, fourfold in this casa during two hours, with 0.8 parcant of tha labal appaarlng in tha bila of anasthatlsad dogs during this pariod. Howavar, tha monkay axcratad a HONS 015798 -18- greater percentage of tha dosa aa parent compound into tha biliary flow than did tha dog, raflacting a lowar dagraa of metabolism of this haxa-CB in the liver of the primate. From these and othar obaarvationa, Sipaa at al. reached a number of significant conclusions. First, tha dog is clearly able to eliminate this hexa-CB from the body substan tially faster than the monkey. Indeed, the dog is the only test species that has been shown to reduce its body burden of this persistent PCB substantially, probably because of its ability to metabolize the molecule despite the lack of vicinal unsubstituted ring position pairs. The monkey appears to be similar to other species in its pattern of elimination of this hexa-CB. The processes of tissue distri bution in the dog are relatively rapid, beginning with early distribution into skin and adipose tissue. In the dog liver, metabolism is relativsly facile in that approximately 80 percent of the radiolabel present in that tissue at 24 hours was in the form of metabolites. In contrast, for both dog and monkey, the major molecular species present in muscle, skin and adipose tissue was in the form of unmetabolized parent compound. For both animal species, the major route of elimination of the hexa-CB and metabolites was via the feces. These results of Sipes et al. with 2,4,S,2',4',S'- hexa-CB can be Integrated with findings from previous studies by Matthews and his colleagues (e.g. Matthews and Anderson, 197S) MONS 015799 -19- 1975) to afford a brlaf survey of tha pharmacokinetic behavlor of thraa PCBs In thraa species, dogs, monkays and rats, ror 4.4' dl-CB, data from tha rat afford raasonabla predlctlva powar for distribution, metabolism and elimination In tha dog, but not In tha aonkay. For 2,3,4- haxaCB, tha dog and tha rat aliainata tha coapound at similar ratas which wara, howavar, fastar than tha obsarvad rata in tha aonkay. Finally, in tha prasant study by Slpas at al., tha 2,4,5 haxaCB data froa tha aonkay ara quita similar to pravlous findings in tha rat, but tha dog is dacldadly dlffarant in that its matabollsa and allalnatlon ratas ara auch fastar. Claarly, spaclas specificity operates markedly and not always predictably in the pharmacokinetics of PCBs in test animal models. Tha reason behind the ability of the dog to metabo lise the persistent 2,4,5 - haxaCB, presumably by direct biochemical action at unsubstituted ring mats positions, is presently unknown. A point bearing on the direction of PCS metabolism in liver by aonooxygenasas Induced by Aroclor 1254 or by 3-aethycholanthrane (3-MC) was demonstrated In a recant paper by Halpaap-Wood at al. (1981). These workers studied the actions of ensymes contained in 9000g fractions derived from tha PCB Induced Sprague-Dawley rat and tha Ha/ICR mouse on unsubstituted biphenyls. When a single polar group is already in place, as in the aonohydroxylated biphenyls, it appears that induction of the 3-MC type (P-448 requiring MONS 015800 -20- enzymes) leads to further monohydroxylatlon in the ring that already bears the first hydroxyl group. The diols produced In this metabolic step result from ortho-para direction by the initial hydroxyl group, leading to 2,5 - and 3,4 -diols. These workers also demonstrated a species difference In the effects of PCBs on the hydroxylatlon of biphenyl in alee. They showed that Aroclor 1254 induction of biphenyl metabo11am differed in the rat and in the mouee. In the rat, PCBa Induced hydroxylatlon both in the 2- and 4- positions. In the mouse, Aroclor 1254 resulted in an Increase in 2- oh biphenyl formation, but not in the 4- hydroxylatlon. Work on metabolic hydroxylatlon of commercial Aroclor mixtures in test animal systems has recently been extended to the terphenyl series. Voss (1981) has observed that the mixture of polychlorinated terphenyls (PCTs) in Aroclor 5460 and a representative hexaCT congener (2,2)2* 5,5',5" -hexa-CT) undergo metabolism in the Sprague-Dawley rat to yield monohydroxylated metabolites, which as yet have not been fully characterised. The rates of excretion of these hexa-CT congeners and their metabolites in feces and urine were quite lowt within 7-14 days only about 10 percent of the radiolabel in the administered dose was recovered in excreta, largely in the feces. ' HONS 015801 -21- B. Human Observations Previous studies by Jensen end Sundstrom (1974), who determined the Cate oC 40 PCB congeners in human adipose had shown that PCBs with no chlorines at the 3,4- position of one ring (e.g. 2,5- diCl-l constituted about 201 of pcbs in human adipose tissue. Two compounds, 2,4,5,2',4*,5'- and 2,3,4,2',4',5'- hexachlorobiphenyl accounted for 36t of the PCBs is tissue. Similar findings were reported by (urokl and Haauda (1977), In an effort to assess exposure among workers in capacitor manufacture, Wolff et al. (1982) determined PCB concentrations in plasma (290) and adipose tissue (61). The highly chlorin ated congeners appeared to be present mostly in tissues of workers who had been exposed to the higher chlorine-containing Aroclors in the past. The less highly chlorinated PCBs, dl-, trl-, and tetrachloroblphenyls, were found in workers who were recently employed and had thus been exposed to the lower chlorine-containing PCBs mixtures, such as Aroclors 1016 and 1221 which were used from 1971 to 1976. further they found that higher exposure occurred among persona with direct contact with PCBs, in jobs such as capacitor filling. Adipose tissue concentrations were proportional to those in plasma. Wolff et al. (1982) have reported recently on epidemio logical findings in a limited cohort of 26 workers employed HONS 015802 22- over a period of years In tha manufacture of electrical capaci tors. They presented analytical data on the content of 37 different PCS congeners in paired samples of adipose tissue and plasma in these workers. It was noted in general that the concentrations of PCBa in tissues were related to the duration and relative intensity of exposures to these chemi cals in the workplace, with a median range of 0.1-9 ug/g for individual congeners in adipose tissue and 0.3 - 27 ng/ml in plasma. As a rule, the PCB concentration in adipose tissue was proportional to that observed in plasma, with partition ing between adipose and plasma in an approximate ratio 190il. Congeners with chlorine atoms in 4 and 4'poaitlons, such as 2,4,4'-tri, 2,4,2',4'-, 2,4,5,4'- and 2,4, 3*,4' -tetra-CB, were major components in plasma and adipose tissue. These workers had been exposed primarily to Aroclora 1016, 1242, and 1254 (20-544 chlorine). Congeners with unsubstituted 3,4 positions (e.g. 2,5-dichloro substitu ted) were observed at lower tissue concentrations and lower adiposeiplasma ratios than other congeners, probably reflec ting metabolism to polar derivatives and excretion by virtue of vicinal positions unsubstituted in either ring. Conver sely, compounds with 2,4 and/ or 3,4 positions substituted by Cl on both rings were present in much higher proportions in plasma or adipose tissue than in the PCB mixtures used to fill capacitors, probably because of diminished capability for hydroxylation and elimination, and were characterized by much higher adipoaeiplasna partition ratios than those for HONS 015803 23- congenera with unaubatitutad 3,4-vicinai ring poaitiona. Alao, aa axpactad on tha baaia of increaaed PCS tiaaut atorage whan metabolic poaaibilitiaa are limitad, thoaa conqanara with 2,4-aubatitution on both ringa had highar adipoaaiplaaaia partition ratioa than conganara with 3,4-aubatitution on at laaat ona of tha ringa. Finally, Bataboiic oxidation and axcration of polar natabolltaa in hiuaan aubjecta of thoaa PCS conganara with two vicinal unaubatitutad carbona corralata rathar wall with lowar adipoaatplaaaa partition ratioa pravioualy obaarvad by Hatthawa and Tuay (I960). Bickal and Muahlabach (1980) aaan to agraa with Hatthawa that by blocking natabolically vulnerabla groupa (auch aa 2 unaubatitutad carbona) a paraiatant compound aay bacoma an unnatabolizabla ona. Thay cita the *key work* of Hatthawa and Andaraon (197S) that the hexa iaoaer, 2,4,5,2',4',5'CB haa no unaubatitutad pair and waa practi cally unaietabolixed. Thay alao atate that in addition to dagraa of chlorination, tha para poaitiona (4,4') are aoat natabolically vulnerable poaitiona. Thua 2,4,2',4'- tatra-CB ia aore paraiatant than tha 2,5,2',$'- iaonar. Finally, thay apaculate that tha general atructure-peraiatence ralationahipa apply to other polyhalogenated hydcocarbona, auch aa PBBa, and polychlorinated naphthalanaa. Bickal and Muahlabach noted, for correlation purpoaaa be tween congener diatributlona in tiaauaa and in coaaaarelal MOMS 015804 -24 Aroclor mixtures, that tha distribution of PCS congeners in huaan adipoaa tlsauaa aanplad in thalr aurvay cantarad about a aaan degree of chlorination naar that of hexa-CB and tharafora was closar to tha composition of Aroclor 1254 (Man degree of chlorination, 5.1) than to Aroclor 1242 (aaan, 3.1) or Aroclor 1221 (aaan, 1.2). It la claar, howavar, that tha distribution of conganars in huaan tlasuaa aftar axtandad Aroclor exposure intervals, and a description of their aaan degree of chlorination, do not nacaasarily constitute quanti tative indices of identity or relationship to any single Aroclor source. Failure to establish this flra linkage is due, at least in part, to tha shifts in residual retention in adipose tissue that can accoapany structure-specific aetabollsa and excretion of suitably substituted congeners from a complex exposure aixture. Discussion and Summary The current findings on tissue levels and pharaacoklnetlc handling of PCla in teat aniaal models and exposed huaan populations have not revealed any significant new insights on the aechanisaa employed by aaauaalian syateae in coping with the presence of these molecules in tissues. Nearly all studies reviewed suggest strongly that in most species, including huaans, tha higher chlorine containing isomers are more blopersistent and resistant to aetabollsa to polar metabolites. The total data base on PCS handling HONS 015805 -25mechanisms Including tissue distribution, metabolism excre tion, points to distinct species specificity in these pro cesses, with rate and tissue distribution constants that are also linked to molecular structure of the individual PCS congeners. The residual concentrations of PCS congeners in fatty and other tissues are seen to be particularly dependent on the ease of metabolism and subsequent excretion of polar metabolites of specific components of the commercial pc* mix tures to which humans and other animal species are exposed. HONS 015806 -26- IV. GENERAL TOXICITY In a racant study by Norback at al. (1981) a call cultura fro* a mouaa embryo call lina was uaad to examine tha toxicity of two hexachloroblphenyls. Thia method involvaa measurement of growth rata and plating afflclancias of tha call lina. Evaluation of two haxachlorobiphanyls (2.4,5.2' ,4 *,5* and 2,3,6,2',3',6') damonatrataa that tha 2,3,6,2' ,3* ,6-isomer was tha most toxic and tha ordar of toxicity parallalad tha long-tarm whola animal studlas. Not all casaa showad a linaar doaa (concantratlon)-raaponga ralatad affact on tha call numbars aftar 10 days axpoaura. Blocca at al. (1981) fad haxachlorobiphanyl lsoaMrs in tha diat of fiva week old mica. Haxachlorobiphanyl rasiduas wara datarmlnad in adiposa tissua and livar. Tha 3,4,5,3 *,4,5* -isomar (not commonly ancountarad in commarcial mlxturas) was the most toxic of those studied and was tha most concen trated in the fat and liver. It also produced tha greatest mortality as wall as hepatocellular markings, hepatocellular swelling and nacrosis, subcutaneous edema and changes in body and organ weights at doses ranging from 0.3 to 300 ppm in the feed. In a review article by McConnell and Moore (1979) on the general toxlclties of halogenated aromatics, including tha dioxins, biphenyls, dibansofurana and naphthalenes, they noted that tha structure-toxicity relationships are similar MQNS 01580? - 27- tor all the compounda in non-human primata* but tha abaoiuta dosaa to produca toxic effects are quite different. Tha affacta include loaa of body weight, alopecia, chloracne, blapharitia, waxy oar canala, dry-scaly-skin and naila and prograaaiva weakneaa. Fatal deatha often occur and offapring may die aarly. The aigna are laaa conapicuoua in rodanta than in non-human primatea. Rabbits apecifically show chloracne. Thera ara other affacta, auch aa, teaticular degeneration, hyperplaaia of tha epithelial tiaaue in tha urinary tract, leucopenia, pancytopenia and altered serum enxyme ayatama which may bo reflective of organ dasMge. Behavioral Effacta The use of behavioral affects in tha assessment of tha toxicity of xanobiotics, particularly those affecting the ner vous systems, is a new field of toxicology which may event ually provide sensitive biological endpoints. There are some who believe that behavioral changes in offspring as well as reduced growth rates should be considered as teratologlcal effects, but until more is known about behavioral lesions and the underlying mechanisms we prefer to adhere to the original concept that teratology refers to abnormal structural changes during embroyonic development. Several animal apeclea have been uaed to detect subtle behavioral effects of PCSs in offapring of mothers expoeed to MQNS 01580S -28- the environmental pollutant during various stages of gestation. Shiota (1970 using the Japanese brand of PCBs, Kanechlors 300 and 500, administered by gavage on 8-14 and 15-21 days of gestation to rats, showed that the offspring had lower birth weights than controls and learning impairments were observed In male testing. However, other field activities and seining ability of the treated and control offspring were sieilar. Store et al. (1981) adeinistered Aroclor 1254 to feaale nice prior to eating and during gestation. Thera was no effect on the ability of the nice to learn an avoidance responses but they took longer to learn the response. The data obtained with primates appear to be more defin itive. Bownan et a^. (1978) observed that feeding of Rhesus monkeys at 2.5 ppm of Aroclor 1248 in the diet resulted in disruption of discrimination learning. A dose-effect rela tionship between PCB body burdens early in life and later behavioral effects were observed. Surviving monkeys were hyperactive in locoawtor tests and deficient in learning various types of discrimination problems at 6 and 12 months of age. These sum eonkeys became significantly hypoactlve, when compared to controls, at 44 months of age (Bowman and Heironimus (1981). These data My indicate that priMtes may have a greater sensitivity to In utero PCB exposure than do mice. In other studies, Bowun et al. (1981) also ob served hyperactivity in the early stages of development of monkeys whose mothers had received the PCBa. However, In HONS 015809 -29- these studies the hyperactivity did not correlate with pcb dosage, leading to the deairabllity of further study. More extenaive atudiea are required to determine which particular period of exposure (gestation or lactation) contri butes to the observed behavioral effects. It would also be important to correlate these effects with physiological or biochemical tissue markers, in particular at the central nervous system (CNS) level. Discussion and Conclusions Recent activity in the study of the acute toxicity of commercial Aroclors and synthetic or purified congeners has tended to focus on evaluation of specific changes Induced in target organs and cell lines. Findings of interest that complement previous literature include! (1) substantial tox icity of 2,3,4-HCB in inhibition of growth of a mouse embryo cell llnei (2) narked hepatocellular toxicity of the 3,4,5-HCB congener in young mice! and (3) an explanation for the inability of 4-chloromethylbiphenyl to induce in vitro genotoxlc effects in terms of its ready metabolic conversion to the corresponding hydroxy compound. These findings do not alter the generalisations on 'PCB toxicity, acute or chronic, pointed out in the 1982 report. The relevance of the behavioral studies in animals to man can only be a matter of speculation, for little or nothing is MOWS 015810 30- knovn about any structural oc metabolic change* that might have taken place during the period of geatatlon and the lngeatlon of Pda In the animal teata. In animal studlea. it la well known that houalng condition* and malnutrition may alter the development of offspring, leading to tome abnormal behav ioral pattern. It la our view that one cannot draw any general conelualon from these studies in relation to behav ioral changes in man and that much more work will be required to understand the mechanisms Involved in altered behavioral activity. Further, the current findings do not cast add itional light on the problem of whether or not lesions lead ing to behavioral aberrations are the precursors of patho logic changes in tissues in animal models or humans. HONS 015811 -31- V. DEEMM. EFFECTS In the previous rsport on potential human haalth affects from exposure to PCBs, it was pointed out that one of the clinical manifestations of Yusho disease was the appearance of chloracne in about 82* of the patients who had consumed contaminated rice oil containing PCBs, PCDFs and PCQs. riachbeln, et al. (1979) reported on the clinical findings among PCB-exposed capacitor manufacturing workers, and noted a high incidence (38-41*) of dermatologic problems in his study population which included about 5* of cases with acneform eruptions. Other Investigators (Inoue et al., 197Si Ouw et al., 1978j chase et al., 1981; Maroni et al., 1981; Baker et al., 1980i Smith et al., 1981) have found low to zero Incidence rates for chloracne in populations occupation ally exposed to commercial PCBs and derived products. In a later paper (1982), Fiahbeln et al. made a more de tailed study of dermatological findings among capacitor work ers and noted a high prevalence of dermatological effects such as erythema, swelling, dryness, thickening of the skin, rash, hyperpigmentation, comedones and acne. However, acne was far less prevalent in these industrial workers than among patients with Yusho disease, .despite high concentra tions of PCBs found in the blood of some of the subjects in the riachbeln survey. HOMS 015812 -32- Dlscusslon and Conclusion* It seems clear that prolonged exposure to certain Aroclor or Kanechlor type PCB mixtures in the occupational setting, sufficient to establish high blood levels of FCBs, could lead to the development of signs of chloracne In sensitive Individuals, but this effect has been seen only rarely. It has generally been observed that an Industrial outbreak of dermatitis. Including chloracne cases, coincided with the production or use of a poor or oxidized grade of PCB containing enhanced levels of contaminants, presumably the PCDFs, and PCQs. Such contamin ants, which have been Identified as major components In samples of the rice oils from the Yusho events In Japan and Taiwan, In our opinion, have led to the high Incidence of chloracne In Yusho patients. The recent findings of Kashimoto et al. (1981) also point to this conclusion. Compat ible with these observations Is the finding that most of the signs of chloracne found in industrial workers are not severe and not long-lasting after exposure has stopped, and are not at all comparable in severity or duration to the symptoms seen in some Yusho disease patients. HONS 015813 -33- vi. grrecrs of pcbs oh liver A. Byperplaatic Foci and Nodular Hyperplasia in th Liver In a recent study, Preaton et al. (1981) reported chat the oral administration of Aroclor 1254 alone or with PCDF impuri ties did not Induce foci of cellular alteration, hyperplas tic nodules or cholangiomas in the livers of male SpragueOawley rats. Further, pretreatment of the animale with diethylnitrosamine (DENA) followed by administration of Aroclor 1254 did not significantly affect the incidence of foci of cellular alteration or other benign hepatic lesions. These results are summarized in Table I. The tumor-promoting activity of Aroclor 1254 recorded in the Table is discussed in Section VII of this annex. These results are of particu lar interest from the standpoint that the studies of Calandra (1975), the National Cancer Institute bioassay (1978) and Preston et al. (1981) with Aroclor 1254 all fall to confirm the Increase in benign hepatic lesions reported by Kimbrough et al. (1975) for Aroclor 1260 in the rat. B. Liver Function and Liver Diseaae in PCB-Exooasd workers In an unpublished, comprehensive epidemiologic study of General Electric Co. employees, Lawton et al. (1981) studied liver function in 172 capacitor workers previously exposed to PCBs. Serum PCB levels for the workers averaged 276 ppb for HONS 015814 -34- Aroclor 1242, S8 ppm for Aroclor 1254, and 34 ppb for Aroclor 1240. Tha hepatic studies showed that the mean serum values 2 standard deviations (SD) were within the normal range for SGOT, SGPT, alkaline phosphatase, total bilirubin and direct reacting bilirubin analyses. The mean serum SGPT value of 34.5 IU was within the normal range (1-55 IU), but the upper level of +2 SD exceeded the normal range. As a part of this study, Lawton at al. conducted an evaluation of the history of 194 PCB-exposed capacitor workers. There was no relation ship between the exposure and episodes of jaundice or hepati tis, most of which occurred prior to employment. Summary and Conclusions These recent studies add Important findings on the poten tial Impact of PCB exposure on liver structure or function in the rat and in human populations. Clearly, Aroclor 1254 dees not lead to benign liver lesions in the male SpragueDawley rat, and extended exposure to Aroclora in the indus trial setting has not resulted in findings of significant liver dysfunction or disease in capacitor workers surveyed in the Lawton study. HONS 015815 -34a- TABLE I Incidence of Liver Lesions In Mli Sorague-Dawley Baca Treated with Aroclor 1254 (Data from Preston et al. , 1981) Number of: Treatment* Ar Control Animals necropsied Foci of cellular alteration Neoplastic nodules Hapatocallular carcinoma Cholangioma Cholangiocarcinoma 72 0 0 0 0 0 Ar 1254 34 0 0 0 0 0 DEN A DENA AH PCDF DEN A 1254 34 32 33 0 10(31) 0 0 6(19) 10(30) 0 5(16) 21(64) 0 1(3) 1(3) 0 0 1(3) AR 1254 PCDF 32 1(3) St 14 ) 27(84) 2(6) 1(3) *Numbers in parentheae* are % incidence. HONS 015816 -35- VII. GASTRIC LESIONS Morgan at al. (1981) examined histologically the stomachs of 144 rats treated with Aroclor 12S4. (These preserved tis sues were from theNCI, 1978 bioassay study). All stomachs were examined (a) by routine section through the junction of the pyloric region and the duodenum and (b) by section of any areas that gave a positive staining reaction for alkaline phosphatase. Although the phosphatase stain may aid in detecting areas with cellular change, the authors state that most of the stomachs showing positive alkaline phosphatase activity were histologically normal. The authors reported an increased frequency of cystic in testinal metaplasia in the treated animals; comparative inci dences were 0/47 in control rats, 3/48 in low-dose, 3/48 in medium-dose, and 13/48 in the high-dose treated animals. Treatment did not change the frequency of 'crypt type* intes tinal metaplasia or diffuse intestinal metaplasia. The total number of rats with all types of intestinal metaplasia was 3/47 in control rats, 4/43 in low-dose, 5/48 in mediumdose, and 15/48 in the high-dose treated group. Thus, the high-dose group, but not the low or medium-dose groups, showed a significant increase in intestinal metaplasia. Metaplasia is characterized by an adaptive substitution ' by one type of adult or fully differentiated cell for another HONS 015817 -34- typo of adult coll. Although Intestinal metaplasia and stomach cancer may co-exist in the pyloric region of the rat stomach, it does not mean that the changes ere related or that metaplasia is a promalignant change. Findings in this study with respect to stomach or intestinal tract cancer are discussed elsewhere in this review. An unusual form of gastric lesion ha3 been observed (Seistfeld et a_l., 1932) in monkeys housed in new facilities which resembled the morphological changes that have been described for animals receiving PCBs in their diet. Forty- five of 2S9 mala monkeys died of chronic progressive disease. The principal necropsy findings were hypertrophic and hyper- plaatic mucous qastrophy. The gastric lesion was characterized by hyperplasia of the gastric epithelium, hypertrophy of mucus- secreting glands, cyst formation and penetration of glands into the submucosa. PCBs were implicated in this finding because of the presence of Aroclor 1254 In the adipose tissue of the animals and in samples of concrete from pens in which the monkeys were housed. The source of the PCDs appeared to be the concrete sealer used in the construction of the pens. Re moval of successive layers of concrete greatly reduced the level of PCB exposure, with a corresponding reduction in animal deaths. Quantitative information on levels of PCBs in the concrete end on dose tranefer to the monkeys was not obtained. HONS 015018 -37- Summary and Conclusions It seems clear that relatively high doses of commercial Aroclors delivered chronically to the stomachs of rats or mon keys can produce pathologic changes in stomach or nearby intestinal tissues. In ehe rat the major change is seen in an increase in the frequency of cystic Intestinal metaplasia in tissue loci otherwise characterized by elevated alkaline phosphatase levels. In the monkey the principal pathologic findings in the stomach are hypertrophic and hyperplastic mucous changes. These recent findings amplify and extend indications of target action on the stomach seen previously in the monkey and rat. HONS 015819 38- VIII. CARCINOGENESIS I EXPERIMENTAL A. Hepatocellular Carcinoma Preston et *1. (1981) reported that administration of Aroclor 12S4 alona or with addad RCDF content for 23 weeks In mala Spragua-Dawley rats did not tnduca hapatocailular carcinoma or cholangiocarcinoma In tha traatad animals (saa Tabla l, Section VI). They found, however that the number of hepatocellular carcinomas induced by dlethylnitrosamlne (OEMA) was in creased whan tha DENA-treated rats also received Aroclor 1254, either with or without PCDF, indicating a tumor promo ting effect of the Aroclor (Table I). B. Bladder Cancer Bladder tumors were not observed in rats given Aroclor 1254 for 23 weeks (Preston et al., 1981). C. Stomach. Intestinal Tract Cancer Using fixed tissues from an earlier bioassay, Morgan et al. (19(1) conducted a reexamination of the gross morph ology and histology of the stomachs of 191 animals preserved from the 1978 NCI bloassay of Aroclor 1254 in F344 rats. The stomachs of these animals were stained for alkaline phosphatase activity, and the alkaline phosphatase positive areas were used to select areas of possible pathological significance. By this means, they detected histological changes in an additional three animals which they characterised as early adenocarci noma) one lesion was in the medium-dose group and two in the MONS 015820 -39- high-doae group. Sex of Che animals was not stated. They also noted two regiona of severe dysplasia in the high-dose group. The lesions which were observed in the glandular stomach and at the junction between the pyloric region of the stomach and the duodenum by Morgan et al. Included intes tinal metaplasia, cystic lesions, and three new adenocarcin omas not seen in the original examination. The total inci dence of adenocarcinomas observed in a total dosed population of 144 animals was therefore one cancer at the low-dose, three at the medium-dose and two at the high-dose of Aroclor 12S4, for a total of six adenocarcinomas. The authors con cluded that since the incidence of stomach adenocarcinomas was less than two percent (no tumors in 47 animals) in simultaneous controls, the observation of six cancers in 144 treated rats constituted a finding in which the likelihood of occurrence at random is less than 0.05. further, they referred to this cancer incidence rate relative to the incidence of stomach adenocarcinomas in historical controls I cited to be one case in 3548 animals), and concluded anew that the occur rence of six adenocarcinomas in 144 Aroclor-treated rats is highly significant (p < 0.001). These conclusions as to the statistical significance of the adenocarcinoma findings in the stomach tissues reexamined by Morgan al. should be subjected' to scientific scrutiny and challenged on several grounds; detailed below. 1. First, Morgan et al. do not specify what statistical HONS 015821 -40- methodology they employed to reach their conclusions about the significance of the cancer Incidence in Aroclor-treated animals vs. either the concurrent controls or the historical controls. The comparisons are further confounded in that the cancer incidence is not separated by both sex and dose for test animals, and proper comparisons are not made between cancer incidences for each sex at each dose level and the corresponding control group values. 2. Since the rate of occurrence of cancers by sex group was not recorded, the only valid test that one can apply to these experimental results is the simultaneous set of com parisons for three dose groups and controls. Nhen this is done, for example, by chi-square analysis with three degrees of free dom, the chi-square statistic is 3.39 for the Morgan data. A value of 7.815 would be required for significance at a level of 0.05. Therefore, the rates of occurence of stomach adenocarcinomas among the dosed and concurrent control groups as presented in the paper could represent just a random draw ing from the same populations. 3. Attribution of possible biological significance to the adenocarcinoma Incidence rates in the three treated groups is further compromised by the fact that there is no clear Aroclor dosage vs. response relationship among the results. Indeed, fewer cancers were observed at the high-dose than at the the medium-dose. The authors do not discuss this point. HOhS 015822 -41- 4. Finally, the reference by Morgan et a^L. to cancer rates In historical controls is inappropriate and possibly mislead ing, since the tissues of historical controls were not exam ined in the same painstaking manner and by the same personnel who performed the Aroclor animal reexamination. Bearing in mind that Morgan et al. picked out cancers in their tissue reexamination that had not been recorded by the pathologists in the 197B bioassay procedures, it could well be that cancers in the. large number of historical controls went unrecorded. These points constitute serious objections to any possible conclusion that the 1978 NCI bioassay provided consistent evidence for. the occurrence of stomach adenocar cinomas in F344 rats treated with Aroclor 1254. Another aspect of this general problem of potential stom ach tumors in test animals dosed with Aroclor mixtures is pro vided by the findings from studies in monkeys discussed in our previous health effects document. Workers in the laboratory of Dr. J. R. Allen at the University of Wisconsin had performed experiments with Aroclor 1248 administered in the diet of the Rhesus monkey, leading to findings of gastric lesions in this primate species. These findings included hypertrophy and hy perplasia of the gastric mucosa, edema of the stomach submu cosa, and mucous conversion of the gastric epithelium at doses as low as 100 ppm in the feed. No such gastric changes were documented in monkeys fed at 2.5 or 5 ppm in the diet. Additionally, Aroclor 1248 in the diet as low as 2.5 ppm HONS 015823 -42- .-ilso produced reproductive problems in monkeys and some fetotoxieity in their offspring in the experiments conducted by Dr. Allen and his colleagues during the period 1974-1980. The work of Allen et al. (1973) on gastric lesions in monkoys received some confirmation in the work of Becker et al. (1979) who produced gastric lesions in Rhesus monkeys receiving dosages of Aroclor 1242 in the mg/kg range. How ever, Iatropoulos et al. (1977) working with the PCB mixture Clophen A-30 and the monkey as test animal did not observe the production of gastric lesions. The question of whether low doses of PCB mixtures of a sufficient degree of chlorin ation can indeed produce gastric lesions in a primate model, possibly as the precursors of the carcinogenesis which Porgan et al. claim to have seen in Aroclor 12S4-treated rats, is an important health effects Issue that requires further experimental study. Finally, in the recent study of Preston et al. (1981) it was found that treatment of male Sprague-Dawley rats with Aroclor 12S4 (100 ppm in the diet) for 23 weeks did not induce gastrointestinal carcinomas. Summary and Conclusion The recent evidence on carcinogenic potential of Aroclor 12S4 in the rat, as cited above in two experimental studies HONS 015824 -43focused on the liver, bladder, stomach and intestinal tract as target organs, must be viewed as essentially negative in our opinion. However, the finding by Preston et al. (1981) of a possible tumor promoting effect of Aroclor 1254 in the Sprague-Dawley rat must be judged as biologically significant. Further studies to probe possible promoter activity of PCB mixtures in mammalian systems seem worthy of early attention. HONS 015825 44 IX. REPBOPUCTIVE EPPECTS Spencer (1982) haa made an aaaeasment of tha fatotoxlc affacta of Aroclor 1254 In rata by adding tha compound to tha dlat of pregnant and paaudopragnant Spragua-Dawlay rata) doaaa rangad from 25 to 900 ppm adminlatarad on daya 6 through 15. Thara vaa a dacraaaa in ovarian protaln in paaudopragnant rata and a dacraaaa in placantal protain and glycogan in pragnant rata. Embryonic raaorptlon did not occur up to expoaura lavala of 900 ppm, but thara waa a dacraaaa in fatal aurvlval rata and fatal weight at concantrationa of 300 ppm and 100 ppm raapactivaly. Thara vaa alao a aignificant dacraaaa in food intaka and matarnal body waight at doaaa of 300 ppm and abova. and nutritional factora alona may account for tha raducad fatal aurvlval and fatal walghta obaarvad at thaaa high concantrationa. Summary and Conclualon Thla nav atudy on tha Impact of Aroclor 1254 on reproduc tion in female rata fad 25 to 900 ppm in tha dlat at a critical parlod during gaatation confirma pravioua raporta that high doaaa of tha PCBa may ba fatotoxlc. Although it ia known that high doaaa of PCS may affact food intaka and waight gain, tha dagraa to which the fatotoxlc affacta ara dlractly cauaad by PCBa or ara a aecondary conaequence of altered nutritional etate in tha doaad animala la praaantly unknown. MOMS 015826 X. MUTAGENESIS Although this annex deals principally with polychlorin ated biphenyls, it is of interest to note results froa a study by Ashby et al. (1981) on mutagenic properties of substructural elements of the PCBs in the in vitro Ames tsst systems. Starting with single aryl rings, these workers found that aniline and benzyl chloride give a negative re sponse in the Ames test for mutagenicity, using a number of strains of S.typhimurium. The addition, however, of a benzene ring to form 4-aainobiphenyl (4AB) and 4-chloromethylbiphenyl (4CMB) greatly enhances the biological activ ity above that of the parent compounds. Positive responses for 4AB were observed in strains TA 1517, TA 1538, TA 100 and TA 98. A negative response was observed in TA 1535. Positive responses for 4Cra were obtained in strains TA 98, TA 1538 and TA 100 but weak and non-reproducible positive effects in strains TA 1535 and TA 1537. On the basis of these observations one might expect that certain PCBs would also be mutagenic in the same Ames assay systems. Schoeny (1982) tested 2,4, 2*,4'-tetrachlorobiphenyl, 3,4,3',4'-tetrachlorobiphenyl, 4-chloroblphenyl, 2,4,6, 2',4',6'hexachlorobiphenyl, and several chlorinated dibenzofurans. All the compounds were found to be nonmutagenic for strains TA 98 and TA 100 when tested over a 3-log dose range. They were also non-mutagenic when tested with either induced or non-induced microsomal extracts as HONS 015827 -46- activators. These result* are reminiscent of the recent finding on the lack of mutagenic potency, with or without S9 Activation, of the important PCDO congener 2,3,7,8 dibenzop-dioxin in the Ames systems. Summary and Conclusion These recent test results on mutagenic potential of PCBs and their analogs in the Ames test with Salmonella test strains add to a body of previously available data pointing to a lack of potency with regard to this important biological effect. Although the biphenyl nucleus substituted with a single polar or reactive group (NH2 or CHjCl) yields posi tive results in Ames systems, single or multiple substitution of Cl groups on the biphenyl rings generally does not yield mutagenic activity, with or without metabolic activation by S9 fractions. It is of further interest that this lack of mutagenic activity also extends to several polychlorinated dibenzo-p-dloxins. MONS 015828 -47- XI. OTHER HEALTH EFFECTS A. ftct on Enzyme Systems Many report! have appeared in the paat tvo or three year! which dealt mainly with effect! of the PCBs and related halogenated compound! on liver microsomal enzyme systems. Moat of these reports simply confirm what is known of the effects of PCBs on the liver and its enzymes. Gartoff et al. (1981) showed that single or repeated doses of various Aroclors In rats produced decreased hexabarbital sleeping-time and in creased liver weight. Shull et al. (1982) studied the induc tive capacity of certain Aroclors in mink and ferrets and found that at 20 ppm in the diet, Aroclor 1016 and 1242 produced only weak induction of mixed function oxidases (MFO). Related poly chlorinated compounds such as the polychlorinated naphthalenes induce mixed hepatic microsomal enzymes in immature male rats, as shown in a study by Cockerline et al. (1981). They induced both the phenobarbital and methylcholanthrena types of enzymes. Pereira et al. (1982) compared single doses of Aroclor 12S4 to single doses of diethylnitrosamine (DENA) as inducers of foci in the liver which produce gamma glutamyl transpeptidase and found that Aroclor was a much weaker initiator of those foci than DENA. The rate of progression of the effect of single doses of Aroclor 12S4 on the different liver forms of cytochrome p-430s (a,b,c,) and epoxide hydrolase (EH) in rat liver microsomes was reported by Parkinson et al. (1982) to vary MONS 015829 -48- ln regard to rat* of Induction and duration of *ff*ct. Ryan *t al. (1982) laolatad a new hemoprotein from rat liver called P-450* and found that It could be Induced by Aroclor 12S4 and phenobarbltal, but not by iMthylcholanthrane. Nllaen and Tuftgard (1981) reported that varloua forma of cytochrome P-450 were inducible in rat livers by paraffins. Ryan and Levin (1981) have purified and characterised the spectral peaks of three different cytochrome P-4S0 ensymes <*,b,c) from rats given Aroclor 1254. Lillenblum at al. (1982) showed that Aroclor 1254 stimu lated glucuronidatlon systems, that is, the glucuronyl tranferases, GTi and GT2. It was also found that GT| is induced by methylcholanthrene, whereas GT2 is like the phenobarbltal induced ensym*. In connection with the effects of FOBS on glucuronidase release when polymorphonuclear leucocytes are treated with certain releasors, such as husian blood serum plus symogen, Lee (1981) showed that Aroclor Inhibited release of polymor phonuclear glucuronidase. The possible significance of this finding is not clear. A clearly protective mechanism has been shown to result when the mlcroaomal system is induced by the PCBs in Aroclor 1254 since this Induction partially protects mice from benzeneinduced leucopenla (Hlerda *t al., al.. 1981> and Greenlee *t 1., 1979). In chicks, Hansen at al. (1981) found that Aroclor 1254 was less potent as an HONS 015830 -49- enzyme inducer than was the same amount of Aroclor 1254 in animal fat obtained from swine which was subsequently fed to the chicks. High-dose levels (t.e.i 9mg/kg> of the Aroclor, were required, but the chicks did not show any other toxic effects from the PCBs. The effects of the pesticides mire*, photomirex and kepone were found by Chu et al. (1980) to be additive, but they did not potentiate the induction of microsomal enzymes produced by polybrominated and polychlor inated biphenyls in rats. Ueng and Alvares (1981), Alvares et al. (1982), Alvares (undated workshop report, 1981) and Serabjit-Singh et al. (1982) have shown that In the rabbit lung, microsomal enzyme content as well as cytochrome P-4S0 were decreased, rather than induced, by administration of Aroclor 1254. The de crease was due to a decrease in P-450; with no alteration in P-450jj . At the doses of the Aroclor used by Alvares et al. (1982) the PCBs were poor inducers of arylhydrocarbon hydroxylase activity in the livers of mice as well as in the kidney of rabbits, but resulted in suppression of this enzyme in rabbit lung. The Serabjit-Singh et, al. study (1982) showed that the effect on the rabbit lung enzyme system was dose related and that 200 mg/kg of Aroclor 1260 in one or two doses produced no change in lung cytochrome P-4S0. The effect of topically applied Aroclor 1254 on the same enzyme systems in the skin has been investigated by Bickers et al. (1962) who showed induction in whole skin, epidermis and HONS 015831 -50- dermls ot arylhydrocarbon hydroxylase, 0-deethylase and epox ide hydrolase. They emphasized the Importance ot the skin as an organ for metabolizing xenobiotics. Summary and Conclusions The ability of Aroclors to induce a variety of micro somal enzyme systems in tissues of test animals has been widely documented. The recent results add to the body of information on the specificity of the Induction process in terns of the types of enzyme systems induced and of the specific tissues in which the process occurs. Notable new findings includet (1) the surprising observation that Aroclor 1254 leads to a decrease in microsomal enzyme content of rabbit lung rather than an increase, due to a decrease in P-450 f with no alteration in P-450u content; (2) the finding of a new Induced heanprotein in rat liver designated as P-450(i (3) the induction of glucuronyl transferases by Aroclor 1254; (4) Aroclor 1254 inhibition of release of polymorphonuclear glucuronidase from leucocytes; and (5) the demonstration that PCB induction in skin leads to an impor tant contribution to metabolism of xenobiotics. NOhS 015832 -51- B- Immunologic Effects Chang At Al. (1981) followed 30 patients who had "YuCheng" disease, duo to Ingestion of rice benn oil contaminAtAd with PCBs, PCDFs and PCQs, in 1979, and found differen ces in these subjects compared to controls in regard to the serum immunoglobulins. They found that serum IgA and Igr but not IgC globulins were lower in the patients than in controls. Also total T-cells, active T-cells and Tu-cells were decreased in the patients but the percentages of 8cells and T-cells were not different in the patients. Hori at al. (1981) succeeded in simulating the Yusho disease in monkeys by feeding them dally doses of a mixture of 5.0 mg of Kanechlor 400, a polychlorinated dibenzofuran (5 ug) plus a polychlorinated quaterphenyl (5.0 mg). The animals exhi bited the usual signs and symptoms of Yusho, such as edema, liver necrosis, and immune suppression. These results strongly suggest that PCDFs and/or PCQs play a major role in the etiology of Yusho. Rabbits which were fed Aroclor 1248 for 4 weeks prior to mating, during gestation, and nursing of the young, were tes ted for immunogenic alterations (Thomas and Hlnsdill, 1980). No general toxicity was seen in the mothers. Only the off spring from the mothers fed 250 ppm (the highest dose in the study) showed some Impaired contact sensitivity but these offspring also showed impaired body weight gains. It was questioned whether the effect observed on contact sensitiv- MONS 015833 -52- ity was a direct effect rathar than an indiraet effect due to tha gonaral action on body waight gain. Silkworth and Grabstain (1982) lhowad that PCB-producad lmmunotoxicity wa* mediated through tha Ah (aryl hydrocarbon) gana locus in mica and that only tha 'planar* structure of tha PCBs (planar being 2,3,3`,4'- versus non-planar 2,5,2',S' -isomers of tetrachlorobiphenyl) was activs. Summary and Conclusions Continuing work on immunological effects in humans ex posed to PCBs mixed with other chlorinated substances in contaminated rice bran oil (PCBs, PCDFs, PCQs), and in mon keys exposed to synthetic mixtures of these three components, has shown signs of immunosuppression or alteration in immun oglobulins and T~cells. Causality with respect to PCBs alone has yet to be established in these species. Additionally, signs of immunogenic alteration or lmmunotoxicity in rabbits and mice dosed with PCBs have been observed. Despite the growing numbers of studies on this health effect, the body of available evidence does not suggest that PCBs alone can produce a dose related effect on immunological competence in the human. In human PCB workers there is no rsported effect on food Intake and body weight, an effect seen only at relatively high-dose levels in animals. HONS 015834 -53- xil. Epidemiology A. Skin Problems Lawton et *1. (1981) made a review of medical records of workers at several General Electric plants; the records from a five year period (1970-1975) were reviewed at which time the employee census varied between 1,500 and 1,800. Skin irritations and dermatitis were reported among these employees. Medical records for a 15 year period of individuals occupationally exposed to PCBs were reviewed. During this period, 49 individuals presented with 'allergic contact derma titis* to PCBs or other constituents of the compounded dielec tric fluid; the dermatitis cleared rapidly, usually without medication, upon removal from exposure. No cases of chloracne were observed. Lawton et al. (1981) also examined the dermatological history of 194 PCB-exposed capacitor workers; 75 employees had 100 dermatological findings of various types in their medical history. Many of the tabulated cases had dermatolog ical findings that would not be considered work-related, since employees recognized the contact nature of most rashes (fiberglass, dirty gloves, watch straps, etc.). Two cases of rash were related to epoxy exposure and not to dielectric fluid. Physical examination of these employees was unremark- MQNS 015835 -54- able and no signs of chloracna past or prasant vara discovarad. Pigmentation, thickening of the skin or discoloration of tha f Inga mails vara not notad. Many of tha darn*to log ical episodes vara notad to antedate employment at General Electric. Host employees had multiple industrial exposures arising from job mobility (maintenance man, use of other chemicals such as solvents, etc.). The authors conclude that it was difficult to relate any dermatological findings specifically to PCI exposure. B. Lipid Metabolism The recent epidemiologic study of Lawton et al. (1981) also focused on workers with elevated serum PCBs. The average serum levels werei Xroclor 1242, 276 ppb; Aroclor 1254, 58 ppb> Aroclor 1260, 34 ppb. The mean serum triglyceride level for 172 PCB-exposed workers was 144.5 mg/dl, which is within the normal range of 50-200 mg/dl, but the upper level of 2 SO was above the normal range. Oeteiled statlsticel analysis demonstrated! 1. A significant positive association between log serum triglycerides and log aerum FCB levels, either as Aroclor 1242, Aroclor 1260 or total PCBi 2. When PCB and ODE levels were considered as HONS 015836 -55- distributed In a serum lipid fraction (sum of triglycerides and cholesterol), the log serum triglyceride level was not significantly dependent on log serum PCBs plus DDEi 3. When PCBs and DDE were considered as body burden, the log serum triglyceride level was significantly dependent on burden only when the percent body fat was removed as an indepen dent variable in the case of Aroclor 1242 4, That the log serum triglycerides were positively related to percent body fat but negatively related to sex. Following discontinuation of the use of PCBs at the 'eneral Electric plants on 6/30/77, Lawton et al. (1981) :ound that the serum cholesterol level for each sex of PCBtxposed workers showed a statistically significant decline ihrough 1979. The 1979 determinations showed that the range * 2SD) in the exposed group was above the upper limit for :he standard range. The serum cholesterol had a significant lositlve association with log serum PCBs but not when stated is PCB in adipose tissue or PCB body burdens. The serum :holesterol level was service and/or age dependent. C. general Complaints 6 Symptomatology HONS 015837 It should be recognised that any survey data on sympto- -56- matology are subjective In nature and that the 'normal* background Incidences of various symptoms can vary widely In different studies, depending In part on how questions are asked and on the type of questions used. Thus, symptomatol ogy reported by workers is the least reliable of the data available for analysis. Flschbein at al. (1979), studying volunteers from Gen eral Electric plants, did not find a significant correlation between reported symptoms and plasma PCS level or between symptoms and duration of employment. Lawton et al. (19(1), studying symptoms reported by 194 PCB exposed capacitor workers at General Electric plants, found reported symptoms (headache, dizziness, depression, memory loss, fatigue, ner vousness, sleeplessness, somnolence) to be less frequent than reported by Flschbein et al. (1979). The analysis of Lawton et al. (1981) suggests that the symptoms reported can be reasonably associated with intercurrent disease and/or the general situations of life stress. Smith e al. (1981), summarizing data from combined work sites, reported that coughing at work and eye irritation were related to both L-PCB and H-PCB levels in serum whereas the symptoms of loss of appetite and peripheral 'tingling* were associated only with L-PCB. Many of these differences were not observed when individual work site data were anal yzed separately) the lack of a difference in each site mav HONS 015838 -57- result because joba war* included as a confounder varlabla. Moat atudiaa have not reported any major aymptoaa aaaociated with expoaure to PCBa (Smith et al., 1581; Krelas et al. 1981). Except for Yuaho disease, which is a special situation (see Section II), and an occasional report of chloracne (section xil), there haa been no reported clinical disease in PCB-exposed populations (Karppanen and Kolho, I972i Humph rey, 19801 Smith et al. 1981) Chase et al. 1981r Xrelss e al. 1981> Baker et al., 1980i Lawton et 4i., 1981). The common but not consistent findings of abnormalities of lipid metabolism, especially blood triglyceride levels, and minor abnormalities of liver ensymes, especially SGOT and GCTP, were not associated with symptoms or clinical disease. D. Pulmonary function The work of Warshaw et al. (1979) of pulmonary function in workers in a capacitor plant, has been reviewed previously, in contrast, the study of Lawton et al. (1981) did not demonstrate that PCI exposure, as measured by serum PCB levels, is correlated with splrosMtric abnormalities. Their data are calculated on the basis of Knudson et al. (1970, using a normal range to >70% for both vital capacity and PEVi/rvc as recomannded by the American Thoracic Society. Abnormal findings occurred primarily in smokers and ex-smokers, HONS 015839 -se as shown In Table II. E. Easting Blood Glucose Lsvsls In tha epidemiologic study of capacitor workers (Lawton at si., 1981), tha naan fasting blood glucose laval and range for PCB exposed workers wars within normal limits. Compari son of 1976 and 1979 valuas showad an apparant dacllna in 1979 that was statistically significant. It was also obsarvad that fasting blood glucosa lsvsls lncrsasad with aga, which Is in agraamant with tha lltaratura. Glucoaurla was not obsarvad. F. Uric Acid Lavals Normal sarum uric acid lavals wars obtalnad in PCBaxposad workars (Lawton at al. 1981). Summary and Conclusions Tha apidamiological ravlaw of madlcal racords of General Elactrlc workars by Lawton at al. (1981), focusad on amployaat with racords of PCB exposure in alactrical capacitor manufacture provides additional clinical data to assess tha possible hasards of PCBs. For workers occupstlonally sxpoaad to PCBs over many years, it is important to note that dermato logical findings ware relatively minor, physical examinations wars unremarkable, and no signs of chloracna past or present HONS 015860 -59- were discovered. Soiaa relationships indicative of altered triglycerides in the circulating serum, were observed; they were not associated with symptoms of clinical disease. Other reported symptoxu, e.g. headache, dlztiness and depres sion are reasonably associated with general life stress, not PCS exposure. Complaints of coughing and eye irritation have been reported by Smith et al. (1981) as related to serum PCB levels, but this has not been reported by other authors. The study by Lawton demonstrates that extensive exposure to PCBs in the occupational setting, sufficient to have established blood levels in excess of 200 ppb, has not led to the production of clinical disease states in General Elec tric capacitor workers. HONS 015841 TABLE II - 6 - Prevalence of spirometric abnormalities in 187 PCB-exposed capacitor workers. Criteria for abnormality of FfVj/rfC given as percent of predicted using standards of Knodson et al. (<70% compared to the older standard (<75%) used by Harshaw et al.). MonSmokers KALE Current a Ex-Smokers Ail MonSmokers FE KALE Current t Ex-Smokers All FVC* 0/41 5/105 (4.8%) FBVj* 0/41 11/105 (10.5%) revj/ rvo 0/41 21/105 (20.0%) 44 12/41 36/105 (29.3%) (34.3%) < 79.5* + < 70.0% < 75.0% 5/146 (3.4%) 1/15 (7.0%) 11/146 (7.5%) 0/15 21/146 (14.4%) 1/15 (7.0%) 48/146 (32.9%) 4/15 (26.7%) 4/26 (15.4%) 8/26 (30.8%) 11/26 (42.3%) 20/26 (76.9%) 5/41 (12.2%) 8/41 (19.5% 12/41 (29.3%) 24/41 (58.5%) HONS 0 1 5 8 4 2 -60- XIII. Recent Finding! on Health Effect* of Polychlorinated Dlbenzofurans 1. Introduction with Increasing realization that tha ralatlvaly potant polychlorinated dlbenzofurans (PCDFs) occur aa trace constituents In commercial PCB mixtures, and are also formed in small yields at temperatures above 270*c (Choudhry and Hutzlnger, 1982) by oxldation/cyclization of suitably substituted PCB congeners, attention has turned to evaluation of the contributions that these tricyclic compounds My make to the toxicity syndrome elicited by exposure to PCB/PCOP mixtures or to Individ ual PCB congeners. A workshop on chlorinated aromatic heterocyclic com pounds was held in Rome In October, 1980. The papers presented at that workshop represent summaries of Impor tant studies performed to that date and form a useful framework for integration with work on the Poors that has appeared In the past two years. Specifically, Mjor workshop papers includedi (1) a presentation (Jansson and Sundstrom, 1980) which described the fonsatlon of PCDFs during a fire in electrical capacitors containing PCBs; and (2) a paper by He Nulty at el. (1980) which presented results on the chronic toxicity of 2,3,7,8-tetrachlorodlbenzofuran In Rhesus Mcaques. HONS 013843 -61- Slnce the biological potencies of PCDFs are of the order of 10* - 104 greater than the toxlcities of corresponding substituted PCBs with respect to produc tion of such health effects as chloracne and P-448 oxi dase induction, it is clearly important to sort out the contributions to total toxicity patterns made by PCDFs even when they are minor constituents (at a few ppm) in PCB mixtures. Indeed, Kaahlmoto at al. (1981) have already high-lighted this point in their analysis of the progress of the Yusho disease syndrome in Japanese patients. These patients were exposed to contaminated rice oil in which the PCDF content was only 5 ppm (on a rice oil basis) but may have been almost entirely respon sible for the persistence of chloracne and skin pigmenta tion over many years in some of the more severely affected patients. Therefore, the following sections are devoted to a brief review of some recent advances toward understanding of the structure vs. activity rela tionships for this important class of halogenated poly cyclic compounds. 2. Animal Studies Recently, Hori et al. (1982) reported on an Inter esting study in which the PCB and PCDF fractions isola ted from a batch of the original Japanese Yusho rice oil were administered orally as the PCB fraction alone (15.4 ug/mouse/day) or mixed PCB PCDF fractions (15.4 uo * HONS 015844 -62- 1.0 ug/mouse/day) for seven days to mala ICR strain mica, follovad by analysis of tha ratantlon of Individual PCB conganara In llvar and adlposa tlssus for tba next 50 days. Ovarall, rasults warn assantlally tha aama for tha two experimental groups In tha following respects' (1) by day 50 In both llvar and adlposa tlasua tha relatlva content of hexa-and hapta-CBs retained was nearly 90 percent of the PCBs In those tissues, probably because of metabolic elimination of lower chlorinated congeners! and (2) residual amounts of PCBs in tissue with the Beta and para positions unsubstituted by Cl atoms (l.e. the 3,4-, 4,5-, 3',4'-, or 4`, 5'-positlons) were small, presumably because of low original concentrations and ready metabolism via vicinal unsubstituted ring posi tions. The principal effect of the PCDFs on PCB reten tion in tissues was to lower the half-lives of three marker PCB congeners in each tissue by a factor of about two. This effect was presumed to originate from selec tive metabolic activation/elimination of these congeners by P-448 oxidases Induced by the PCDFs. Yoshihara at al. (1981) have reported on an Impor tant study of the acute actions of 13 different PCOF congeners in male Wlstar rats, with single lntraperltoneal injections of congeners in corn oil vehicle at levels near 1 mg/kg leading to enxyme induction of the 3-methylcholanthrene (P-448) type and to variable accumulations HONS 015845 -63- ln liver tissue. A major finding of the study concarnad tha controlling influence o ring substitution by Cl atoms on tha coursa of 3-MC typa ansyme induction in livar tiasuai all 9 PCDF congenars having at laast 3 Cl atoms in tha critical lataral positions (2,3,7,8 on tha PCDF rings) axhibltad typical 3-MC typa induction. Tha moat potant conganara for this affect, active at a single dose near 1 mg/kg, ware those with tha lateral positions completely filled, i.a. both 2,3,7,8 - tatra CDF and 2,3,4,7,8 - panta CDF. Congenars with two or lass Cl atoms in the lataral positions did not show any enzyme inductive affect at a single dose as high as 5-10 g/)cg. In this study, tha PCDF congeners active as 3-MC typa Inducers also produced marked atrophy of tha thymus and hypertrophy of tha livar in rats) congeners inactive as inducers failed to elicit these effects on thymus and liver. The ability of congeners to concentrate in liver and produce acute hepatotoxlclty turned out to be quite variable and to bear no clear relationship to PCDF struc ture. The cooperative acute and subchronic toxicities of two of these highly substituted PCDTs with lateral posi tions completely filled, the 2,3,7,8 - tatra CDF and 2,3,4,7,8 penta CDF congeners, were studied earlier by MONS 015096 64 Moor* *t al. (1979) In single strains oe mice and guinea pigs and also in th* Rhesus monkey. All animals war* doaad by gastric intubation in corn oil, and showad toxic signs ranging through th* sati body weight loss, dacraaa* in body waight gain, thymic atrophy, llvar hypertrophy, anemia, edema of fac* and lips, loss of facial and other hair, loss of fat, hyperkeratosis, squamous metaplasia, etc. Curiously, both the guinea pig and th* monkey were quit* sensitive to th* acute toxicitles of these PCDrs 5-10 ug/kg (12-15 days) and 1000 ug/kg, respectively, but th* (S7Bl/6fh(J67) strain of mouse was relatively insensitive to acute toxic actions of these PCDPs, showing no clinical signs of toxicity over 30 days at doses up to 6600 ug/kg. These acute lethality data could also be compared with acute data on th* correspondingly substituted dibenzo-p-dloxln, th* 2,3,7,8 - tetra COD congener, to give an estimate of th* relative lethal potencies of fully laterally substi tuted PCDrs vs. PCDDs. In th* guinea pig th* PCDrs were only 2-4 fold weaker than th* tetra CDD; in th* monkey th* factor by which th* PCDPs was weaker was about 20 fold) and in the resistant mouse th* factor difference in 30 day LDSOs was approximately 23 fold. These differ ences amount to on* to two orders of magnitude in lethal strength of fully laterally substituted PCDD* over PCDPs. The PCDPe are not uncommon contaminanta in the eco MONS 015847 -65- sphere. They are formed In the coarse of synthesis of polychlorinated phenols. Rappe et al. (1979) have noted that they are found in fly ash and flue gases, resulting from pyrolysis of PCS residues by at least three cyclixstlon reactions involving either loss of two ortho cl atoms, loss of ortho H and Cl atosis, or migration of Cl atoais on rings followed by cyclization. Cavallaro et al. (I960) have also measured the amounts of PCDP con geners in effluents from inclnersted solid urban wastes. Rappe et al. (1981) have found many PCDP congeners stored In the fat of animal species as widely separsted as the snapping turtle (U.S.) and the grey seal (Sweden), using mass fragmentograms as the detection/identification tool. PCDP congeners have been studied in recent pharmaco kinetic and toxicologic experiments with a variety of animal models. Decad at al. (1981) studied the distribu tion and excretion of the fully laterally substituted 2,3,7,8 - tetra CDP In two strains of mice, with the findings that the liver was the major site of Initial accumulation, redistribution to adipose tissue then occurred, 55-80 percent was excreted as polar metabolites in the feces within 10 days, and the whole body half life for total elimination of parent compound and metabo lites was of the order of 2-4 days. Veerkamp et al. (1981) also studied PCDP metabolism, using the Wlstar rat. These workers found that monohydroxy and dihydro'xy MONS 015848 -66- derivatlves ware In various tissues and excreta (Cat, liver, urine, feces), involving, at least in part, the occurrence of Cl atom shifts plus hydroxylation. Lower degrees of PCDP chlorination led to a variety of hydroxylated derivatives, plus some containing the -SB sulfhydryl group Isolated as the methylthioether, but the higher PCDFs (e.g. the fully substituted octa car) resis ted metabolism. Much unchanged PCDP was excreted in the feces, presumably before intestinal reabsorptlon had occurred. Nc Nulty at al. (1981) extended the study of the actions of the potent congener 2,1,7,8 - tetra COP to Rhesus monkeys. Dosing in the food at SO ug/kg/day for 2 months or S ug/kg/day for 8 months yielded severe signs of toxicity (and early deaths) in these primates. Including reduction in physical activity, severe skin changes, swollen eyelids and enlargement of the meibomian glands, hyperkeratonlc nail bed, atrophy or squamous metaplasia of sebaceous glands, mucous metaplasia and hyperplasia of the gastric mucosa, involution of the thymus and hypoplasia of the bone marrow. In animals that survived, recovery was apparently complete after 3 months on control diet. Because of the biological potencies of suitably subs tituted PCDrs, the ability to detect and quantitate small amounts of these compounds in tissues and other samples becomes very important. Hutslnger e al. (1981) HONS 015849 -67 have reported on a bioanalytical approach to this prob lem which make* uaa of an initial atap involving reversibla binding to a specific racaptor protain of tha hepa tic cytoaol of rodanta or in cultured mammalian call*. Essentially, thla technique measure* tha ability of a compound in a sample to diaplace radiolabeled 2,3,7,8TCDD from ita binding to tha receptor ayatea, and quantitataa tha molar amount of that compound in reference to that concentration of unlabeled TCDD which can affect half-diaplacament of tha label. From extracta of air aamplea containing PCDFa or PCDOa in tha ng/m3 concentra tion range, thia method ia able to afford eatlmatea of the amounta of tetra-octa chloro-aubatltuted congener* in either family of compound*. A recent report (Sllkworth at al., 1982) on a 1981 fire in the State Office Building in Binghamton, New York Involved fire product* from a transformer containing aa dielectric fluid 65 percent of a PCB mixture and 35 percent of chlorinated benxenea. The fire reaulted in releaae of large quantltie* of aoot contaminated with PCBa, PCDDa and PCDFa. Congener* preaent included the fully laterally aubatituted 2,3,7,8-TCDO (two aampleat 2.8, 2.9 ppm) and 2,3,7,8-TCOF (272, 124 ppm). Both the aoot and equivalent aample of ita benzene extract ware teated for acute oral toxicity and lethality in guinea piga and dermal toxicity in rabbit*. In guinea piga. HONS 015850 '68 the spectrum of toxic signs sxpoctsd for PCDD-PCDP mixtures (weight dscrsssas, offset on thymus and kldnay, hyperpla sia and metaplasia, triglyceride elevation, etc.) was about equivalent for either carrier mode, soot vs. extract, as were the respective LDSO valuea (410 mg soot/kg, 337 mg soot equivalent/kg). In rabbits, dermal application of the soot or the extract resulted In liver pathology, but local skin serous lnflsaaatlon occurred only with the benzene extract. Indicating that the soot matrix prevented local Inflammatory reaction from particlebound PCDOs and PCDPa. Finally, In a comprehensive recent review, Parkin son and Safe (1981) have attested correlations of PCOr toxlclties with aryl hydrocarbon hydroxylase (AHH) induc tion, as a key biological action of these chemicals. The animal toxlclties sort Into the following major health categories! (1) wasting syndrome. Involving pro gressive weight loss that la not simply related to de creased food consumption) (2) a variety of skin disor ders Including chloraene, alopecia, etc.) (3) lymphoid Involution, with thymic and splenic atrophy and Immunosup pression) porphyria, involving an overproduction of uroporphyrinogen) (S) endocrine and reproduction dysfunc tion) (6) tsratogenesls) (7) carcinogenesis. These auth ors tested correlations between specific health effects HONS 015851 69- ln theae categorlea and the ability to induca AHH, rea eon ing fro* tha baa la that correeponding atructura v*. activity ralatlonahlpa in aach chemical elaaa ahould influence or govarn toxic potency for a given affect, receptor binding affinity to tha apaciflc cytoaoi recep tor, and tha ability to Induca P-448 requiring AHH. Taking account of age dependent, aex-dapandant and organ-apeciflc differencea In auaceptiblllty aaan in dlffarent teat apaciaa and atraina, and affecta dependant on tha praaanca or abaanca of a genetic Ah locua control ling AHH aynthaaia, some poaitlve correlation ware in deed noted. Good correapondence waa found between Mo lecular atructura lending to AHH induction and that producing aignlfieant binding affinity to the cytoaoi receptor. However, it waa noted that AHH induction may correlate with one toxic affect but not another aa atructure la varied, and that in aoae caaea the relationahlp between AHH induction and toxicity la not eatabllahed unequivocally. No coapelliag evidence waa found that AHH per ae -aedlatea the lethal effacta of theae com pound! , even though AHH induction correlatea with toxi city for certain apecific health affecta. Farklnaon and Safe alao pointed out that other factora laplnge on the ability to aort out clear correlatlona between AHH induc tion and apecific toxic affecta. Por example, theae polyhalogenated coapounda alter the vltaaln atatua of HONS 015852 70- animal models (vitamin A, ate.), which may in ltaalf hava great impact on biological response patterns, and iron daficiancy in a teat animal modal may ba abla to negate or parturb the ability of a compound to initiata porphyria. 3. Human Qbaarvatlona Ho naw information bearing on Pepr-induced health affacta in exposed human populatlona haa appeared in the paat two yeare, aalde from the Increasing emphaala placed on potential cauaatlon of paralatant Tuaho dlaaaaa aymptoma in Japanese and Taiwanaaa patianta by thaaa chemlcala. It la possible that PCDP affects such as chloracna and ensyme Induction might also occur in other sufficient ly exposed human populations, but detection would depend on being able to tort out the specific contrlbutiona of these agents alone from the total spectrum of chemical mixtures (e.g. PCBs and chlorinated phenols) in which they are generally encountered aa trace contaminants. To date, the identification of unique PCDP effects In humans haa not been documented. Summary and Conclusions The PCPrs have been studied with increasing Interest In recent years as realisation grows that they are Impor tant contributors to the toxicity of mixtures in which they may be present at only tiny mole fractions. In HONS 015853 -71- recent animal studies they have been shown to be powerful AHH inducers, especially when the lateral 2,3,7,8-posi tions are fully substituted by chlorine atone. They produce aany toxic signs in test aninal systems including severe skin changes, swollen eyelids, enlargement of meibomian glands, squamous metaplasia, hyperplasia of the gastric mucosa, thymic involution, hypoplasia of the bone marrow, and hepatotoxicity. They undergo antabolic hydroxylation and excretion when the pattern of chlorine substitution is suitable, with major excretion of polar metabolites in the feces. Aside from continued analysis of residual health effects in Yusho patients, in which the opinion is growing that PCDFa are major contributors to the persistent toxic syndrome observed, little in the way of human PCDP exposure vs. effect Information has bean docusMnted. HONS 01585** -72- re reran ces ALLEN, J.R., ABRAHAMSON, L.J., andNORBACK, D.H. (1973). Biological affects of polychlorinated biphenyls and triphenyla on the subhuman primate. Environ. Res. 6:344-354. ALVARES, A.P., UENG. T.H. and EISEMAN, J.L. (1982). Polychlorinated Biphenyls (PCBs) Inducible Mono-oxygenases in Rabblta and Mice: Species and Organ Specificities. Life Sciences. 30:747-751. ASHBY, J., TRUEMN, R.W., STYLES, J., et al. (1981). 4-Chloroaethylblphenyl (4-CfB): a novel mutagen an3 potential carcinogen. Carcinogenesis 2(11:33-38. BAKER, E.L., LAN ORIGAN, P.J., GLUECK, C.J., ZACX, M.M., et al. (1980). Metabolic consequences of exposure to polychlorinated biphenyls (PCB) in sewage sludge. An. J. Epldea. 112(553-3*3. BECKER, G.H. et al. (1979). Polychlorinated biphenyl-induced morphologic changes in the gastric aucosa of the rhesus monkey. Laboratory Investigation 40373-383. BICKEL, M.H. and MDEHLEBACH, S. (1980). Pharmacokinetics and ecodlsposltlon of polyhalogenated hydrocarbons: aspects and concepts. Drug Metabolise: Reviews 11(2): 149-190. BICKERS, D.R., DUTTA-CHOUDKURY, T., MUKHTAR. H. (1982). Studies on Cytochrome P-450 content and mixed-function oxidase and epoxide hydrolase activity. Molecular Pharm. 21:239-247. BIOCCA, M., GUPTA, B.N. and CHAE, K., et al. (1981). Toxicity of selected symmetrical hexachlorobiphenyl isomers in the mouse. Toxicol. Applied Pharmacol. 58:4*1-474. BOWMAN, R.E., HEXRONXMUS, M.P., and ALLEN, J.R. (1978). Correlation of PCB body burden with behavioral toxicology in monkeys. Pharmacol. Blochem. Behavior 9:49-56. BOWMAN, R.E., and HEXRONXMUS, M.P. (1981). Locomotor hyperactivity in PCB-exposed rhesus monkeys. Heurotoxlcol. 2(2):251-268. BOWMAN, R.E., and HEXRONXKJS, M.P. (1981). Hypoactlvity in adoles cent monkeys perinatally exposed to PCBs -and hyperactive as juveniles. Neurobehavloral Tox. Teratol. 3:15-18. CALANORA, J.C., (1975). Summary of toxicological studies on coasserclal PCBs. Proc. of the National Confer, on Polychlorinated Blphenvla. Nov. 19-21, Chicago, XL. CAVALLARO, A., BANDI, G., INVERNIZZX, G., et al. (1980). Sampling occurrence and evaluation of PCDDs and PCDrs from incinerated solid urban waste. Chemoaphere 9:611-621. HONS 015855 -73 CHANG, X., HSIEH. X., LEE. T., et al. (1980). Immunologic evaluation of patlanta with PCB poisoning: Determination of lynphocyta sub populations. Toxicol Applied Pharmacol 61)58-63. CHASE, X.H., VIOMG.O., THOMAS, D., BEIMEY, B.W. , and SIN, R.R. (1981). Clinical and metabolic abnormalities in occupational exposure to polychlorinated biphenyls. Presented at the American Occupational Health Conference. Atlanta, Georgia. CHEN, P.H., CHANG, K.T., and LU, Y.D. (1981). Polychlorinated biphenyls and polychlorinated dibenzofurana in the toxic rice-bran oil that caused PCB poisoning in Taichung. Bull. Environ. Contam. Toxicol. 26:489-495. CHOUDHRY, G.G., and HUTZINGER, 0. (1982). Mechanistic aspects of the thermal formation of halogenated organic compounds including polychlorinated dibenzo-dloxins. Part II: Thermo-chemical generation and destruction of dlbensofurans and 3lT5enzo-p-dioxins. Toxicol. Environ. Cham. 5)67-93. CHU, I., VILLENEUVE, O.C., BECKING, G.C., IVERSON, P., and RITTER, L. (1980). Short-term study of the combined effects of mirex, photo* ml rex, and kepone with halogenated biphenyls In rats. Jour. Tox. Environ. Health 6:421-432. COCKERLINE, R., SHILLING, M., and SAFE, S. (1981). Polychlorinated naphthalenes as hepatic microsomal enzyme inducers in the immature male rat. Gen. Pharm. 12:83-87. DECAO, G.M., BIIMBAUM, L.S., and MATTHEWS, H.B. (1981). Distribution and excretion of 2,3,7,8-tetrachlorodibenzofuran in C57BL/6J and DBA/2J mice. Toxicol. Applied. Pharmacol. 59:564-573. FISCHBEIN, A., WOLFF, M.S., LILIS, R., THORNTON, J. and SELIKOFF, I. (1979). Clinical findings axmng PCB-exposed capacitor manufacturing workers. Ann. N.Y. Acad. Sciences 320:703-715. FISCHBEIN, A. WOLFF. N.S., BERNSTEIN, J., SELIKOFF. I. and THORNTON, J. (1982). Deotatological findings in capacitor manufacturing workers exposed to dielectric fluids containing poly chlorinated biphenyls (PCBs). Arch, of Environ. Health, Vol.37 (2) >69-74. GARTHOrr, L.H., CERRA, F.E. and MARKS, E.P. (1981). Blood chemistry alterations in rats after single and multiple gavage administration of polychlorinated biphenyl. Toxicol. Applied Pharm. 0:33*44. GEISTFELO, J.G., BONO, M.G., BULLOCK, B.C. and VARIAN, M.C. (1982). Mucinous gastric hyperplasia in a colony of rhesus monkeys (Macaca aulatta) induced by polychlorinated biphenyl (Aroclor 1254). Laboratory Animal Science 32(1)>83-86. MONS 015856 -74 GREENLEE, W.F. , DENT, J.G. and IRONS, R.O. (1979). efface Of pretreataent with Aroclor 1254 and salactad polychlorinated blphanyl isomers on bansana-lnducad myelotoxicity In tha rat. Acadea^Proceedlnga arid Abatracta. John Ellaha Hltchall scl. Soc. HALPAAP-WOOD, K., HOIKING, E.C. and HOIKING, H.G. (1981). Tha affact of 3-aethylcholanthrene, Aroclor 1254, and phanobarbltal induction on tha netabolisa of blphanyl by rat and aouse 9000g auparnatant llvar fractlona. Drue Watab. and blapoalt. 9(2):103-107. HANSEN, L.G. and STRIR, J.J., at al. (1981). Biological activity of technical Aroclor 1254 compared to Aroclor 1254 raaiduaai Swine fat raalduaa fad to broilar cockerels. Toxicol. 21:203-212. HAY, A.W.M. (1980). Expoaura to TCDD: Tha Health Rieka, in Chlorinated Pioxlna and Related Coapounda. Ed. by O. Hutxingar, jt.al., V5i58#-<6fl, 19801 3757 Pergaaon Praaa, 1982. HEIHONIMUS, N.P., LAUGHLIN, N.K., and BONHAN, R.E. (1981). Effecta of early expoaura to PCBe on learned Irrelevancy of cues In rhesus sonkeysi An incidental learning paradlgs. Teratology 24(1)i55A. HORI, S., OBANA, H., and KASHIHDTO, T., e al. (1981). Biological affects of PCBs and related polychlorinated coapounda on Croo sonkeys. J. Pharaacobla Dvn. 14i5-65. HORI, s., KASHIMDTO, T., and KUNITA, N. (1982). Effect of poly chlorinated dlbenxo-furan on tha retention of polychlorlnatad biphenyl isosera in the liver and adipose tissue of alee. J. rood Hvc. Soc. Japan 23(2)>147-175. . HU0HREY, H. (1980). Evaluation of huaana exposed to halogenated biphenyls. Mar. Chea. Soc. Olv. of Environ. Chea. 201(2). HUTIINCER, 0., OLIE, K., and LUSTENHOUNER, J.W.A. (1981). Poly chlorinated dibsnso-p-dioxlns and dibenaofuranss a blo-analytical approach. Cheaosphere 10i19-25. IATROPOOLOS, M.J., rELT, R., at al. (1977). Histopathology of low chlorinated biphenyls and hexachlorobenxene in feaale rhesus aonkeys. Toxicol. Applied Pharaacol. 41:173,4100. INOGE, Y., at al. (1975). Discovery of PCB pollution In a textile factory. I. 5b level In blood aerua of laborers and results of physical exaalnation. Jon. J. Public Health 22:461-463. (As reported in NIOSH Criteria Document). JANSSGN, B. and SUNDSTROM, G. (1980). Foraatlon of polychlorinated dlbenxofurana (PCDP) during a fire accident in capacltora containing polychlorinated biphenyls (PCB). In Chlorinated Dioxins and Related Coapounda. Ed. by O. Hutalneer. at al.. v5:201-208, 1980. N7x7 Pergaaon Press, 1982. MQNS 015857 -75- JENSBI, S. and SUNDSTROM, G. (1974). Structures and levels of moat chlorobiphenyls In two technics! PCS products and in human adipose tissue. Anblo 3i(2)70-76. KSRPPANEN, C. and KOLHO, L. (1972). The concentration of PCS in huaan blood and adipose tissue in three different research groups. PCS Conference II. Stockholm. KASHINDTO, T., at al. (1981). Role of polychlorinated dlbensofuran in Yusho (PCS poisoning). Arch. Environ. Health. 36:(6>:321-364. ---------- KlfBROUGH, R.D., et al. (1975). Induction of liver tumors in Sherisen strain female rats by polychlorinated biphenyl (Aroclor 1260). J. Natl. Cancer Inst. 55i1453-1459. KNUDSCM, R.J., SLATIN, R.C., LEBOWITZ, H.D.. and BURAOWO, B. (1978). The smxIisusi expiratory flow voluste curves normal standards, variabi lity, and effects of age. Am. Rev. Reap. Pis. 113:587. XREZSS, I., et al. (1981). Association of blood pressure and poly chlorinated EIpKenyl levels. JAHA. 245(24)s2505-2509. KUROKI, H., and MASUDA, Y. (1977). Structures and concentrations of the siain components of polychlorinated biphenyls retained in patients with yusho. Chemosphere. 8:4(9-474. LAWTON, R.W., SACK, S.T., ROSS, N.R. and FEINGOLD, J. (1981). Stud ies of employees occupationally exposed to PCBs. General Electric Progress Report. LEE, Tee-Ping, (1981). The inhibition of PH) B-glucuronidase release by Aroclor 1254. Environ. Res. 25:386-390. LILIENBLUM, N., KALLI, A.K., AND BOCK, K.W. , (1982). Differential induction of rat livar microsomal UDP-glucuronosyltransferase activities by various inducing, agents. Blochem. Phans.31(6):907-193. MAR0HI, M., al. (1981). Occupational exposure to polychlorinated biphenyls in electrical workers. I., Environmental and blood polychlorinated biphenyls concentrations. British of Indust. Had. 38:49-54. MAR0NI, M., et al. (1981). Occupational exposure to polychlorinated biphenyls in electrical workers. II.. 'Health Effects. British Indus. Usd. 38:55-60. RASUDA, Y., KUROKI, H., YAMARYO, T., HARAGUCHI, K., SJ al. (1982). Comparison of causal agents in Taiwan and Fukuoka PCs poisonings. Chemosohets. 11,(2)t199-206. MATTHEWS, II.B. and ANDERSON, K.W. (1975). Effect of chlorination on the distribution and excretion of polychlorinated biphenyls. Drue Mstab. Disc. 2:(5)371-380. HONS 015858 76- MATTHEWS, H.B. and TOBY, D.B. (1980). The effect of chlorine position on the distribution and excretion of four hexachlorobiphenyl isomers. Toxicol. AppI. Pharma. 53:377-388. MCCONNELL, E.F., and MOORE, J.A., (1979). Toxlcopathology charac teristics of the halogenated aromatics. Annals. N.Y. Acad. Scien 320:138-150. ----------- ~~ ------- -- MCNULTY, W.P., POWRANT8, I.H. and FARRELL, T.J. (1981). Chronic toxicity of 2,3,7,8-tetrachlorodibentofuran for rhesus macaques MCNULTY, N.P., POME RAN T1, I.H. and FARRELL, T.J. (1980). Chronic toxicity of 2,3,7,8-tetrachlorodibenzofuran for rhesus macaques. In Chlorinated Dioxins and Related Compounds. Ed. by o. Hutsinqer, et al, 5:41 l-lUTT nTy. Perqamon Press, 1982. MOORE, J.A., MCCONNELL, E.E., DALGARO, D.W. and HARRIS, M.H. (1979). Comparative toxicity of three haloqenated dibenxofurans in guinea pigs, mice and rhesus monkeys. Annals N.Y. Acad. Scl. 320:151-183. MORGAN, R.W. , HARD, J.M. and HARTMAN, P.C. (1981). Aroclor 1254- induced intestinal metaplasia and adenocarcinoma in the glandular stomach of F-344 rats. Cancer Res. 41:5052-5059. NAGAYAMA, J., KURATSUNE, M. and MASUDA, Y. (1981). Formation Of polychlorinated dibenxofurans by heating polychlorinated biphenyls. rukuoka Acta Med. 68:593-599. NATIONAL CANCER INSTITUTE, (1978). Biosassay of AROCLOR 1254 for possible carcinogenicity. Technical Report Series. No.38. NEBERTS, DANIEL, W., (1981). Genetic mechanisms controlling the induction of polysubstrate mono-oxgenase (P-450) activities. Ann. Rev. Pharm. Tox., 21:431-462. NILSEN, O.G. and TOFTGARD, R. (1981). Effects of polychlorinated terphenyls and paraffins on rat liver microsomal cytochroaw P-450 and in vitro metabolic activities. Arch. Toxicol. 47:1-11. NORBACK, D.H., CIHLA, H.P. and RE0DY, G. (1981). In vitro measur ement of PCS toxicity. Toxicol. Halooenated Hydrocarbons: Hlth. Ecol. Effect (Pap. 8vmp.) 173-184. OUH, H.R., SIMPSCN, G.R. and SIYALI, D.S. (1976). Usa and health effects of Aroclor 1242, a polychlorinated biphenyl, in an electr ical Industry. Archives Environ. Health 31:189-194. PARKINSON, a. and SAFE, S. (1981). Aryl hydrocarbon hydroxylase induction and Its relationship to the toxicity of halogenated aryl hydrocarbons. Toxicol. Environ. Chem. Rev. 4:1-45. PARKINSON, A., THOMAS, P.E., and RYAN, D.E., at al. (1982). Time course of Induction by Aroclor 1254 of three 7orma of cytochrome P-450 and epoxide hydrolase (EH0 In rat liver mlcrosomes. Fed. Prac. 41 (4),1299. MQNS Q15859 77 PEREIRA, M.A., HERRD), S.L., BRITT, A.L. and KHOURY, M.M. (1982). Promotion by polychlorinated biphenyls o enzyme-altered foci in rst livar. Cancar Letters 15:185-190. POLAND, ALAN and KNUTSON, JOYCE, C., (1982). 2,3 ,7,8-tetrachloro- dibenso-p-dioxin and related halogenatad aromatic hydrocarbons. Ann. Rev. Pharm. To*. 22:517-554. PRESTON, B.D., VAN KILLER, J.P., MOORE, R.N. and ALLEN, J.R. (1981). Promoting affects of polychlorinated biphenyls (Aroclor 1254) and polychlorinated dlbensofuran-free Aroclor 1254 on diethyl- nitroaamine-indueed tumorigenesls in the rat. J. Nat. Cancer Inst. 66(3) :509-515. " ----------- RAPPS, C., BUSER, H.R. 6 BOSSHAROT, H-P. (1979). Dioxins, dibenzofurans and other polyhalogenated aromatiesi production, use, for mation and destruction. Annals N.Y. Acad. Set. 320:1-18. RAPPE, C., NYGREN, H., BUSER, H.R. and KAUFPINEN, T. (1981). Occupational exposure to polychlorinated dioxins and dlbensofurans. In Chlorinated Dioxins and Related Compounds. Ed. by 0. Rutzlnger, et al. vit4ff-S13. N.Y. Perqamon Press, 1982. RYAN, D.B. and LEVIN, H. (1981). Comparisons between a major and minor form of liver mlcrosoawl cytochrome P-4S0 from rats treated with Aroclor 1254. Fjd. Proc. 40(6): 1640, Abst.4582. RYAN, D.E., THOMAS, P.E. and LEVIN, w. (1982). Purification and characterization of a minor fora of hepatic microsomal cytochrome P-450 from rats treated with PCBS. Archives Biochem. Biophysics 216(1)1272-288. SERABJIT-SINGH, C.J., ALBRO, P.N. and PHILPOT, R.N. (1982). The effects of Aroclor 1260 on rabbit pulmonary cytochrome P-4S0 isozymes. Pad. Proc. 41(5):1479. SHIOTA, K. (1976). Postnatal behavioral effects of prenatal treatment with PCBs in rats. OtaUmax rol. Anat. Jap. 53:105-114. SCBOHY, R. (1982). Mutagenicity testing of chlorinate?-biphenyls and chlorinated dlbensofurans. Mutation Rea. 101:45-55. SHULL, L.R., BLEAVXRS, M.R., OLSON, B.A. and AULERICH, R.J. (1982). Polychlorinated biphenyls (Aroclors 1016 and 1242): Effect on hepatic microsomal mixed function oxidases in mink and ferrets. Environ. Contam. Toxicol. 11:313-321. ' SILKMORTH, J.B.. and GRABSTEIN, E.M. (1982). PCB lamunotoxlclty: Dependence on isoawr planarity and the Ah gene complex. Toxicol. Applied Pharmacol. 65:109-115. SIPES, I.G., SLOCUM, M.L., PERRY, D.F. and CARTER, D.E. (1982). 2,4,5,2*,4*,5'-hexachlorobiphenyl: Distribution, metabolism, and excretion in the dog and the monkey. Toxicol. Applied Phar macol. 65:264-272. HONS 015860 -78- SNTH, A. B., at al. (1982). Metabolic and haalth consequences o{ occupationaT-axpoaure to polychlorinated biphanyls (PCBa). British J. of. Ind. Mad. 39:361-369. SPENCER. F. (19B2). An assessment o tha reproductive toxic poten tial of Aroclor 1254 in female Spraque-Dawley rata. Bull. Environ. Contaw. Toxicol. 2S<290-297. s-- STORK, 3.X., HART, J.L. and SKITH, R.E. (1981). Bahavior of alee aftar pra- and poatnatal axpoaura to Aroclor 1254. Naurobahav. Toxicol, and Taratol. 3_(l)<5-9. -- THOMAS, P.T. and HIHSOILL, R.O. (1980). Parinatal PCB axpoaura and lta afftct on tha iamuna syataia of young rabbits. Drug Chaw. Toxicol. 3(2) 1173-184. ----- * UEMG, T.H. and ALVARES, A.P. (1981). Salactiva loss of pulmonary cytochroma P-450 in rabbits pra-traatad with poiychlorlnatad biphanyls. J. Biol. Chaw. 258(14)<7536-7542. VEERKAMP, H., NEVER, J. and HUTZXNGER, 0. (1981). Tha watabolisw of soma chlorinated dibensofurans by rats. Chawosphara 10(4)<397-403. VOSS, R.A. (1981). In vivo watabolisw and disposition of Aroclor 5460 and 2,2,2", 5,3751' Kaxachlocotarphanyla (HCTs) in tha rat. Dlaaartatlon Abstract Int. 42i no. 3. WARSHAW, R. at al. (1979). Dacraasa in vital capacity in PCB- expoaad workers in a capacitor manufacturing facility. Annals N.Y. Acad. Scl. 320<277-283. H1ER0A, 0., IRONS, R.O. and GREENLEE, W.F. (1981). twwunotoxicity in C57BL/6 wica exposed to benxene and Aroclor 1254. Toxicol. Applied Pharmacol. 60:410-417. HOLFF, K.S., at al. (1982). Disposition of polychlorinated biphenyl congeners in occupationally exposed parsons. Toxicol. Applied Pharmacol. 62(1)<294-306. YOSHXHARA, S., NAQATA, X., YOSHI MURA, H., KUROXI, H., and MASUDA, Y. (1911). Inductive affect on hepatic anxymas and acuta toxicity of individual polychlorinated dlbansofuran congeners in rats. Toxicol. Applied Pharmacol. H<500-588. YOSHIHARA, S. and YOSHIMURA,.H. (1981).' Study for "Yusho*- the progress in this decade. Elsel' XaoaXu 27(3) <144-155. HONS 015861 CW-143 SUMMARY OF THE HEALTH EFFECTS OF PCB* Novunbf 1981 Pnpaiad for: CHEMICAL MANUFACTURERS ASSOCIATION ecology and environment, inc. Its SUGG ROAD, P.O. BOX O. BUFFALO. NEW YORK 14226. TEL. 716-WTT M>1 International SpscMtts in the Environmental Sdencea recycled paper HONS 015862 TABLE OF CONTENTS Section Paq8 PREFACE ...................................................................................... Ill EXECUTIVE SUMMARY ................................................................. 1 1 MAMMALIAN TOXICOLOGY OF PCBs .............................................. 1-1 2 ROLE OF PCBs IN PROOUCINS CANCER ...................................... 2-1 3 RISK ASSESSMENT AS PART OF THE REGULATION OF PCBs: STATEMENT OFPURPOSE, NEEO, AND LIMITATION .................... 3-1 4 SUMMARY ANO CONCLUSIONS ....................................................... 4-1 MQNS 015863 1i PREFACE The technical review concerned with the effects of PCBs, as pro vided on the following pages, summarizes the findings reported In the following documents: e "The Epidemiology of PCSs" by William Gaffey, a Monsanto pub lication, (1981). e "A Review and Evaluation of Carcinogenicity Studies In Mice and Rats and Mutagenicity Studies with Polychlorinated 81phenyls" by George Levlnskas, a Monsanto publication, (1981). t "The Toxicity of Aroclor Products 1242, 1254, and 1260 to the Liver of Albino Rats" by George Levlnskas, a Monsanto publica tion, (1981). "Human Health Effects of Electrical-Grade PCBs" by J.F. Brown, Jr., J.T. Coe, and H.O. Pocock, Or., a General Electric publi cation, (1981). e "Technical Review of the Health Effects of PC8s" by Robert Janes, Morris Cranmer, and Raymond Harblson, a New England Gas Association publication, (1981). "Assessment of Carcinogenic Risks From PC3s in Food" by kenny S. Grump and Marjory Masterman, prepared for the United States Congress Office of Technology, contract # 933.1350.0, (1979). Ill HONS 015864 The reader will note that, with the exception of the section on risk assessment, the summaries In this report contain no specific ref erences to other documents. Since the documents listed above, which review the pertinent literature on PC8 health effects to date, give specific references for further study. It was not thought necessary to repeat these same citations In the body of this report. For a more In-depth review of the pertinent PC8 literature and specific cita tions, It Is suggested that the reader refer to the documents listed above. HONS 015865 1v EXECUTIVE SUMMARY In this paper we examined the human health risks associated with exposure to PCBs. To accomplish this purpose, we reviewed all slonifIcant published or readily available studies of the effects of PCBs as well as the pertinent current theories of carcinogenesis, the scien tific body of knowledge which supports these theories; and have pro vided an analysis of the chemical carcinogenesis testing performed with commercial PCBs. As a result of this review and evaluation, it is our Independent professional opinion that "any exposure to PCBs" does not pose a significant health risk to humans. These conclusions are based on data of the primary exposure to commercial grade PCBs. After reviewing the carcinogenesis test data, we have concluded that coimercial PCBs do not represent a carcinogenic (genotoxic/ initiator) risk and that, even if they possess oncogenic (epigenetic/ promoting) activity, the risk at low exposures is insignificant. This mechanistic distinction Is a very important basis from which to address the cancer risk. To paraphrase a succinct summary of this distinction by Welsburger and Williams, promoters (oncogens) share the characteristic of being active only at high, sustained doses, and up to a certain point, the lesion may be reversible. Thus, these types of carcinogens represent only quantitative hazards to humans, and safe levels of exposure may be established by carrying out proper doseresponse studies. Attempts to estimate the potential risk of cancer to man caused by PCS exposure using data developed In rodents represents a contro versial but crucial dilemma. Numerous studies involving both mice and 1 HONS 015866 rats hive been reported, but only one study exists to date that sug gests PCBs may cause an increase in hepatocellular carcinoma. When the paucity of convincing data is compared to the large number of neg ative tests, and when other important contributing factors are con sidered (e.g., the spontaneous rate of liver injury and liver regener ation, thereby promoting aberrant hepatocellular growth; etc.), it Is difficult to conclude that PCBs represent a significant cancer risk in man. Analysis of published animal data leads to the conclusion that. In animals, commercial PCBs represent a low acute exposure hazard; that mutagenic, teratogenic, and reproductive risks are minimal; and that the carcinogenic potential of this compound has not been convinc ingly demonstrated In an animal model relevant to man. This lack of suggestive risk based on animal data has been further borne out by the fact that neither liver nor other cancers in man have been positively linked to PC8 exposure in recent epidemiologic studies utilizing large study populations. At worst, PCBs at high or elevated doses meet some of the cri teria for a chemical promoter, i.e., they enhance tumor growth through epigenetic mechanisms but do not Induce new tumor growths. This dis tinction Is of extreme Importance and can be made based upon the known mechanisms for genotoxlc carcinogens and those for promoting agents. PC8s demonstrate many characteristics of the latter and none of the former. A further Importance of this distinction is that PCBs have only been shown to possess a weak promoting activity at most. There fore, the thresholds both proposed in theory and observed in animal studies suggest that there are safe exposure levels for PCBs. The occupational exposures are certainly the most extensive and longest-term human PC8 exposures that we are currently aware of, and are therefore probably most representative of what adverse effects might be expected. A comparative review of these occupationalexposure studies reveals that, like other chemicals, PCBs can cause adverse health effects, but In many respects these have been minimal. While dermatitis and chloracne, which were reversible after discon tinuing the exposure, have been noted in some cases, no other sig- > nlflcant findings were routinely made. Even though several studies incorporated clinical chemistry analysis as Indications of organ Z HONS 015867 dysfunction or other physical disorders, no remarkable clinical find ings have been uncovered. Furthermore, several investigators have commented to the effect that there is a "paucity of abnormal results" and that "there is no evidence of physical harm resulting from working with PC8s." In spite of over 50 years of use, no causal relationship has been established for any specific type of cancer, nor has it been proved that the incidence of cancer mortality has increased. The largest study, by the National Institute for Occupational Safety and Health (NIOSH), iWilch involved over 2,500 persons, did not detect any statistically significant excess in the cancer mortality. Since this study failed to demonstrate an excess cancer rate in a high exposure population, It provides some reassurance that it is unlikely that future studies will show any Increased risk of cancer from PCBs. ' In sumeary, epidemiologic studies have demonstrated that PCBs are not remarkably toxic chemicals after acute exposure, and that when excess exposure does occur, the usual consequences are dermatologic and not of a serious or permanent nature. Chronic exposures have added little or no additional adverse effects of note to this picture. The preponderance of studies has not identified a clinical disease associated with exposure to PCBs, nor has It provided persuasive evidence of health impairment. There is no evidence of an excess In total mortality or in mortality due to cancer, cardiovascular disease, or nervous system disease associated with occupational exposure to PCBs. PCBs have not been linked to any human cancer, and studies to date indicate It is highly unlikely future studies will establish such a link. Therefore, It appears that PCBs are not a remarkable toxi cant, but a chemical which requires high doses to produce harmful effects. The chemical analyses of PCBs have shown that they often contain polychlorinated dlbenzofurans (PCOFs) at low levels. The concentra tions of these toxic contaminants are generally in the parts-permllllon range In pure PC8 mixtures, but percent of contamination can be substantially Increased as a result of Industrial use. Since levels of PCBs generally found In the environment are in the partsper-mlllion range or lower, the concomitant concentrations of PCOFs would be expected to be unmeasurable. For this reason and because the toxicity data of all PC8 exposures have probably Included this 3 HONS 015866 contaminant, the concern for low level exposures to PCDFs Is still expected to be minimal. However, the conclusions reached In this report apply to exposure to conmerclal PCBs and cannot be applied to all environmental PC8 exposures, which may Include exposure to concen trated contaminated waste mixtures. HONS 015869 4 MONS 015070 1. MAMMALIAN TOXICOLOGY OF PCBs Any assessment of hazards posed by exposure to a chemical must consider the doses required to elicit each toxic response as well as the spectrum of toxlcltles the chemical Is capable of Inducing. All of these factors must be carefully Incorporated Into the final estima tion of risk. Many toxicity tests depend upon clearly observable effects, such as organ Injury or tissue damage. For these tests, detection of the effects in question Is clear, and the results can directly be extrapolated to determine the potential for a similar adverse effect In man. However, a complete safety assessment and evaluation must also include tests designed to measure mutagenic or carclnogenlc potential. While the biological manifestations for these tests may be easily measured and reproduced, what the experimental results represent with respect to the expected human response is less clear. Therefore, results from the latter tests should not necessar ily overshadow findings In the former tests. Instead, the results from all tests must be evaluated for Internal consistency. As new data emerges, this Information should likewise be Incorporated and, if necessary, the risk reassessed. Polychlorinated biphenyls (PCBs) are not capable of causing Iimedlate life-threatening responses In animals except at very high doses. When given as a single oral dose to rats, mice, or rabbits, the dose lethal to SOS of the test species lies in the 1,000 to 16,000 mg/kg of body weight dosage range. According to the scheme proposed by the American Industrial Hygiene Association, this dosage range for acute or Immediate toxicity classifies PCBs as only a slightly toxic to 1-1 MOMS 015871 practically nontoxic chemical. Ethyl alcohol Is in the same toxicity class. The most consistent pathologic findings associated with the lethality of short-term tests are fatty Infiltration of the liver, liver Injury, and centrllobular necrosis of the liver. This Is not an unexpected finding. Many chlorinated organic chemicals produce liver or kidney Injury In mannals. Other effects observed In acute studies Include depression and lethargy, decreased pain response, anorexia (loss of appetite), ataxia (unsteady gait), and diarrhea. These are signs of chemical Intoxication that are also commonly seen with many other organic chemicals. PCSs applied directly to the skin of rabbits produce dermal re sponses such as erythema, hyperkeratosis, blisters, and desquamation. These effects are not a particularly remarkable finding for any or ganic chemical. In monkeys, the epidermal disorders from oral dosages of 250 to 400 mg/kg are facial edema, hair loss, and acne. While chloracne has been reproduced in humans after high occupational expo sures, It can also be produced by exposure to other chlorinated ben zene derivatives. Other than discomfort and some scarring In severe cases, It Is a reversible effect. Subchronic studies have revealed other effects. Weight loss and liver Injury become a more consistent finding in the rodent species, with liver enlargement and an Induction of liver metabolism occurring at lower doses. PCBs are potent Inducers of the mixed function oxi dase system, more potent In fact than either phenobarbltal or DDT, which have been used extensively as experimental tools for this pur pose. PCB mixtures are also uniquely capable of Inducing both cyto chrome P-450 and cytochrome P-448. The other systemic effects reported are porphyria; Increased thy roid metabolism; gastric hyperplasia; Increases in triglycerides, cholesterol, and phospholipids; and atrophy of the spleen and thymus. Estrogenic activity for PCBs has been reported in rats, and prolonged menstrual cycles and Increased bleeding have been observed In monkeys. Of the above effects, the thymic change and the Immunosuppressive effects of PCBs are probably of most concern. Changes In the Immune system could lead to Increases In the susceptibility to and'severlty of Infectious and neoplastic diseases. However, attempts to verify that the immunosuppressive effects of high doses of PCBs might 1-2 HONS 015872 Increase the cancer risk from other causative agents have produced Inconsistent results. PCBs have been reported to Inhibit the tumor growth of Walker 256 carcinosarcoma cells, to enhance the growth rate of MC8 cells derived from the moloney sarcoma virus, and to be without any effect on the moloney leukemia virus. Test procedures designed to Indicate serious long-term or chronic effects have been somewhat variable, but these too have provided fairly unremarkable effects when compared to the potential harm caused by other useful Industrial chemicals that have been similarly tested. Manual Ian studies Indicate that there Is little reproductive risk as sociated with moderate to high doses of PCBs. Studies using up to 100 mg/kg/day did not affect reproduction In the rat, and similar results have been reported from tests in mice and monlceys. PCBs do, however, cross the "placental barrier." Primates born to exposed mothers have shown symptoms of intoxication. Also, those doses high enough to dis rupt the estrus cycle have been shown to decrease the implantation rate, ret PCBs did not produce any hlstopathologlcal changes In the reproductive tracts of either sex of rats, caused no chromosomal dam age or arrested spermatogenesis, and were negative In the dominant lethal test for Inheritable damage to germ cells. More Importantly, PCBs have not significantly altered embryo or fetal development In either rodents or nonhuman primates at doses that were not maternally toxic; thus, It can be concluded that there appears to be little or no teratogenic or reproductive risk associated with exposure to PCBs. The overall mutagenic potential of PCBs Is Inconsequential. Di rect mutagenic activity as measured by point mutations In bacterial tester strains has been recently reviewed by levlnskas (1981). Ac cording to the results of seven different studies, a group of chlori nated biphenyl compounds did not demonstrate any mutagenic activity. Although there Is one report In the literature that 4-chlorobiphenyl might have mutagenic activity, other researchers have not been able to reproduce this observation. Additionally, Aroclor 1254 was found not to stimulate unscheduled DMA synthesis In the rat hepatocyte. In tests designed to observe chromosomal aberrations or alterations In number, the results were also overwhelmingly negative. PCBs were HONS 015873 1-3 negative when tested In the Drosophila melanoqaster. negative In cyto genetic analysis of In vitro hunan lymphocytes, negative In cytoge netic preparations of rat sperm and bone marrow cells, and negative In the dominant lethal assay. Thus, chlorinated biphenyls have not demonstrated any mutagenic potential when tested with the majority of commonly used and well-substantiated mutagenicity procedures. Attempts to estimate the potential risk of cancer to man caused by PCS exposure using data developed In rodents represents a contro versial but crucial dilemma. Numerous studies Involving both mice and rats have been reported, but only one study exists to date that sug gests PCBs may cause an increase in hepatocellular carcinoma. When the paucity of convincing data Is compared to the large number of negative tests, and when other Important contributing factors are con sidered (e.g., the spontaneous rate of liver cancer In rodents; the Inductive and cellular growth-promoting potential of PCBs; the poten tial for PCBs to Induce recurrent liver Injury and liver regeneration, thereby promoting aberrant hepatocellular growth; etc.). It Is dif ficult to conclude that PCBs represent a significant cancer risk in man. This lack of suggestive risk based on animal data has been further borne out by the fact that neither liver cancer nor other cancers In man have been positively linked to PCS exposure in recent epidemiologic studies utilizing large test populations. Industrial-grade PCBs may not be just a mixture of chlorinated biphenyls but a mixture that may also contain chemical contaminants, the polychlorinated dlbenzofurans (PCDFs). Therefore, when consider ing all of the data sumaarlzed In preceding paragraphs, an assessment of the toxicity and risk to PCS exposure may be complicated by the fairly recent recognition and acknowledgement of PCDF contamination. Tetra-, penta-, and hexachlorodlbenzofurans have been measured In Aroclors 1248, 12S4, and 1260 In concentrations on the order of 0.1 ppm for each isomer. Studies of Japanese brands of PCBs Indicate that they contained concentrations which were several times higher. Of even more concern Is the possibility that dlbenzofurans may be formed In significant amounts when PC8s are exposed to high heat and some reactable form of oxygen. This concern was first expressed after the Yusho Incident when It was discovered that the PCOf content was AONS 015874 1-4 approximately 1,000 times higher than expected for commercial Japanese PCB mixtures. Studies have revealed that the oxidation of PCBs to PCOFs is 2* to 3* for Aroclor 1254 at 550' to 600`C and that, during combustion, the rate of formation Is time and temperature dependent. However, these conditions do not exist in the normal manufacture or use of PCBs nor In the normal use of PCBs In capacitors or trans formers. These conditions might have occurred, however. In some heat exchange equipment. So, at present, the conditions for and the extent of PCDF contamination In PC8 wastes Is unknown. While It should always be considered that PCDFs may Increase the toxicity of coemerclal PCB mixtures, the variety of acute and chronic tests reviewed on the preceding pages are tests In which the contribu tion of PCOF toxicity was, no doubt, unconsciously measured. There fore. concern for the greater toxicity of this contaminant, when It Is. In concentrations approximating those previously measured In coemerclal PCB mixtures (l.e., about 1 ppm), should be tempered by the possibility that its risk Is that reflected by the animal test data gathered for what was previously considered to be a PCB mixture alone. To reiterate the original premise, evaluating the hazard of any chemical on the basis of animal data requires careful consideration of (1) the spectrun and types of toxic responses induced; (2) the degree of species variation or consistency of the effects monitored; (3) the relevancy and validity of the test performed; (4) the dosage required to elicit the response; and (5) the level of relevance of the toxic effects observed, based upon the expected level of human exposure. Thus, many of the PCB-Induced adverse effects would be expected for a chlorinated organic compound of the PCB type, or at least these effects are consistently produced by many chlorinated organics. These effects Include liver injury, liver enlargement, liver enzjme Induc tion, Irritation when applied to the skin, chloracne, and possibly a disruption of the estrogenic balance In females because of Increased liver metabolism. Although these may Indeed be considered adverse effects, all chemicals are capable of altering some physiologic func tion at a high enough dose. In the more relevant reproductive, tera togenic, mutagenic, and carcinogenic tests, chlorinated biphenyls were consistently negative with only a few exceptions. These exceptions _ 1-5 MOMS 015875 c>n be discounted because of Inadequate study design, disputable Interpretations, and unusual tests. Titus, It seems unnecessary to display a disproportionately high concern for those few controversial studies, especially when their findings were not reproduced In sub sequent studies under similar or identical conditions. In the vast majority of experiments, the effects were produced by PCBs at high doses. Since the expected and likely human exposure to PCBs Is low, the results of the tests using high-exposure conditions are not rele vant to the expected human exposure level. Therefore, It appears that PCBs are not a remarkable toxicant, but a chemical which requires high doses to produce harmful effects and one which clearly represents minimal or no risk to htmans because of the limited nature of anticipated hunan exposure. White PCBs can be toxic, and their toxicity can be dramatically Increased by high levels of dlbenzofuran contamination, the manmallan toxicity data sug gest that. In general, PCS mixtures can be tolerated under most realworld conditions. Ktrns 0158'" 1-6 2 * **> MOMS 015S77 2. THE ROLE OF PCBs IN PROCUCING CANCER Chemically Induced carcinogenesis Is a special aspect of toxlcology, for the toxicants may or may not observe traditional toxicologic principles. For example, although carcinogens show dose-response relationships, may undergo biotransformation to active or Inactive metabolites, and demonstrate specific structure activity relation ships as other toxicants do, they may also be unlike other toxicants: they may not demonstrate thresholds and there may exist a long and Indefinite latency period between the critical biochemical event and any cellular or physiologic expression. In recent years, the scientific community has concluded that even among chemical carcinogens there exist vast differences In the mechan isms by which they Induce cancer. One can separate chemical carcino gens Into two groups. One group obeys traditional toxicologic princi ples while the other does not. This classification of carcinogens has been described by Welsburger and Williams In Casarett and Doulls' "Toxicology: The Basic Science of Poisons." These authors separate carcinogens Into genotoxlc (Initiator) and epigenetic (promoter) car cinogens, the distinction being that genotoxlc carcinogens Induce can cer by Initiating a permanent change In ONA. Epigenetic chemicals comprise those chemicals which alter the manifestation of cancer by other than genetic means and Include hormones. Immunosuppressants, cocarcinogens, and promoters. This distinction is extremely important because genotoxlc carcinogens are irreversible and may not have thresholds; therefore, some risk Is present at any dose. Promoting HONS 015878 2-1 agents (epigenetic chemicals), on the other hand, do have demonstrable threshold levels; thus, there are exposures for which the risk is minimal or the risk exists only for some finite interval after expo sure. For our discussion of the carcinogenic potential of PC8s, we reviewed the data for evidence to determine to which of these two classes of tumorogenic chemicals PC8s belong, and in our discussion we refer to the epigenetic class as promoters (i.e., chemicals that only increase the manifestation of cancer cells) and to the genotoxic class as initiators. After reviewing the carcinogenic test data, we have concluded that PCBs do not represent a genotoxic (initiator) risk and that, while they may possess some promoting activity, the risk at low expo sures is insignificant. This mechanistic distinction is a very impor tant basis from which to address the cancer risk. To paraphrase a succinct summary of this distinction by Weisburger and Williams, pro moters share the characteristic of being active only at high, sus tained doses, and up to a certain point, the lesion may be reversible. Thus, these types of carcinogens represent only quantitative hazards to humans, and safe levels of exposure may be established by carrying out proper dose-response studies. The following paragraphs suimurize the data supporting this important distinction and address their sig nificance for PC8s. There has been yeat controversy about the relevance and nomen clature of rodent hepatic lesions. Most of this controversy surrounds the criteria used to diagnose cancer. The National Cancer Institute (NCI) has recommended a scheme for the classification of hepatocel lular tumors and related lesions In rats. These recommendations have not been universally accepted, but are utilized in many of the reports of PC8 carcinogenesis. The NCI classification scheme is extensive and specific in defining neoplastic lesions. It was concluded by NCI that benign hepatic celt tumors, i.e., without potential for malignant be havior, could not be diagnosed consistently. Therefore, terms such as "adenoma," which refers to a benign tumor, were not recommended. It was also determined that the term "hepatoma,* used to denote a benign liver tumor, was Imprecise in its usage and was not recommended for the description of any of the lesions under discussion. In contrast Z-2 HONS 015*79 to tradition, detection of vascular Invasion or metastases was not considered by NCI to be essential for the diagnosis of hepatocellular carcinoma. Instead, the utilization of inclusive cytologlcal criteria describing changes which may or may not have the potential to become the disease process we call cancer. Including many responses which will never progress to cancer, was accepted at the expense of the more definitive criteria of malignant or Invasive neoplasms. The first report of PC8-1nduced tunors was that of an Increased Incidence of hepatomas. A later publication of the first study, which appears to have Included the animals from the original report, terms the previously described hepatomas as well-differentiated hepatocel lular carcinomas. Similarly, another study describes the production of hepatomas by PCBs in mice, but later the hepatomas are described as neoplastic nodules. Changes In liver cellular morphology were Observed In mice only when the PCS chlorine content was 52* to 54*, and then only at exposure levels of 300 to 500 ppm. Lower doses did not produce tumors, and those PCBs with a chlorine content below 52* to 54* did not Induce tunors. Further, the reported study of PC8fnduced cancer In mice Included only 12 mice studied for 32 weeks. This Is not an acceptable bioassay procedure because of the small mxnber of experimental animals used and the short time of exposure. Also, there was an Inconsistency In reporting terminology. The liver changes were reported as hepatocellular carcinoma and also as hepato mas or tunors or nodular hyperplasia. A better bioassay was performed later that Included larger numbers of test animals exposed for longer periods of time, and no Increased Incidence of tunors was reported. Subsequent studies were consistent with this larger study, and the majority of scientific literature supports the claim that PC8s are not carcinogenic In mice. Similarly, only PCBs with a chlorine content of 60* produced those cellular morphological changes In rat liver that were classified using NCI guidelines as hepatocellular carcinoma. However, this same PCS mixture was tested In another strain of rat and did not signifi cantly Increase the Incidence of tumor formation. Moreover, four other studies also failed to show any PCB-Induced tuxors. With one exception, there Is a consistent absence of reports finding PCBInduced hepatocellular carcinomas. Again, those PCBs with a chlorine 2-3 HONS 015880 content below 52* to 54* did not produce tumors In rats. These results are similar to those for mice. Neither were tumors Induced when the average PCB chlorine content was 52* to 54*. The two studies using an average chlorine content of 60* reported no induction of hepatocellular carcinomas. There is only one report of PCB-induced hepatocellular carcinoma in rats. Since this report used the criteria developed by NCI for classifying liver pathology, we must weigh the importance of this report against the majority whose data are negative. As previously stated, utilization of these inclusive cytologlcal criteria to define cancer will define some hepatocellular changes as cancer that will never progress to cancer. Furthermore, Investigations have shown that the vast majority of regenerating or hyperplastic nodules reported as cancer disappear upon removing the animals from the chemical exposure. While some Investigators have considered the use of the Inclusive cytologlcal criteria for classifying hepatocellular lesions, many have rejected this classification scheme because of Its lack of diagnostic discrimination. Thus, the single report of PCB-induced cancer In rats uses a pathological description in opposition to the usual terminology for describing a benign tumor. Chemical carcinogens are those substances capable of initiating cancer. Cancer is defined as the production of life-threatening malignant tumors of potentially unlimited yowth that expand locally by invasion and systemlcally by metastasis. Chemical carcinogens irreversibly Initiate and ultimately produce cancer. This is an important distinction and requires careful and accurate evaluation of the kind of tumors produced. Chemicals that promote benign tumors are not carcinogens. Therefore, tumor type Is critical to determining whether a compound Is a carcinogen. Failure to distinguish between tumor types will place equal Importance on test results regardless of whether a malignant or benign tumor Is produced as a result of expo sure to a chemical. Therefore, It is absolutely essential to define the tumor type associated with chemical exposure to be able to evalu ate the outcome and apply the data to humans. Equally Important, it is essential to determine the mechanism by which tumors are produced. Failure to distinguish the mechanism by which tumors are produced will place equal Importance on chemicals 2-4 HONS 015881 which are Initiators (genotoxlc) and on those which are promoters (epigenetic). The following discussion of cancer will make the impor tance of this point clear. Initiation of cancer Is the process of producing damage to DMA of a magnitude sufficient to be sustained, but of a nature which permits cell survival and thereby predisposes the capacity of uncontrolled growth. Those cells containing damaged DNA then produce clones con taining an inheritable mutation. Mutagenicity Is defined as produc tion of an Inheritable alteration In the genome of a cell. An altered genome will Increase the probability of cellular dysfunction. There fore, inheritable mutations or Initiation of genes responsible for cellular regulation Increase the probability of producing cancer, a condition of regulatory dysfunction expressed as uncontrolled growth. Since most manual Ian genes exist In allelic pairs and the malignant phenotype Is probably recessive for nonvlral induced cancers, a reces sive mutation would not normally express Itself as cancer until a sec ond mutation occurred In the other allele. While there is normally a low probability of this occurring spontaneously by chance, given enough mutations In enough cells and a prior Inheritance of suscepti ble genes through the germ cell line, the chance of having a success ful mutation within both alleles of a critical gene, thereby producing a dysfunction In cellular regulation like cancer, becomes probable. Thus, we can easily see how genotoxlc agents (Initiators) can apply selective pressure upon the cell toward the cancerous state. However, In our most often used test species, the mouse and the rat, there Is a normal background incidence of the Initiation process lead ing to cancer In the liver. Thus, where there Is a history of spon taneous cancer Incidence, there Is little doubt that cancer will oc cur; only the rate and the time required to develop cancer (latency) Is unknown. In this situation, the risk of cancer Increases with time and the magnitude of the Initiated response Is a cumulative probabil ity. In rodents, several factors have been shown to alter their back ground cancer Incidence Including total dietary calories, fat content, vitamin E, stress, crowding, and gender. Therefore, to define a chem ical as a carcinogen (Initiator) rather than another promoting factor In these species by using changes in liver cytoarchitecture requires proof that the chemical is an initiator and not a promoter of the 2-5 HONS 015882 spontaneously occurring disease state. To do this. It must be shown that the compound Initiates sustained damage to DNA in a dosedependent manner. On the other hand, promoters are chemicals that modify gene ex pression and cellular coirmunlcatlon. Promoters can alter the ability to control various genes, thereby providing a selective growth *1van tage. Promotion Is defined as enhancing the selective proliferation Of previously Initiated cells. By definition, promotion cannot occur until a critical gene Is Initiated. Wounding, growth stimuli, necro sis, Inflanmatlon, and certain chemicals can selectively and rapidly allow cells containing the mutated gene to form a clone of semllnttlated cells. Cell death, cell trauma, and cell hyperplasia are all produced by PCBs and can be expected to yield conditions favoring preferential growth of (promotion of) previously Initiated cells. One can safely generalize that the tumorlgenlc properties of PCBs result, at least. In greatest part from alteration of the homeostasis of con trol mechanisms. Thus, changes seen In rodents with a high Incidence of liver tumors must be Interpreted carefully so as not to mistake toxic responses and promotion for Initiation. Additionally, processes only promoting cancer In situ would be expected to regress upon re moval of the promoter and not change the ratio of metastasizing to nonmetastaslzing tumors. It is noteworthy that often such appears to be the case with liver cancer In rodents produced by cyclic chlori nated compounds. In summary then, It has been documented that PCBs do not increase the Incidence of tumors at any site except the rodent liver, liver tumors are a common part of the natural disease process of rodents. Thus, changes seen in rodents with a natural history of a high Inci dence of liver tumors must be Interpreted carefully so that toxic re sponses and promotion are not mistaken for Initiation. Liver cell death, trauma, and hyperplasia are all produced by PCBs and can be expected to yield conditions favoring preferential growth of cells with dormant neoplastic phenotypes. Therefore, one can safely gener alize that the tumorlgenlc properties of PCBs In the rodent liver re sult, at least. In greatest part from these alterations of homeosta sis. The following sunmarlzes the data delineating PCBs as a poten tial promoting agent (epigenetic) but not an Initiator (genotoxlc car cinogen). 2-6 MQNS 015883 Comparison of the Characteristics of Promoting Agents and Effects of PCBs 1. Promoters produce Increases of spontaneous tumors at selected sites. PCBs produce only liver tumors. 2. Tumors produced by promoters usually do not increase the metastatic characteristics of spontaneous tumors of the same site. PCB-Increased liver tumors do not metastasize. 3. Promoters do not produce transplantable tumors unless the naturally occurring tumor Is capable of transplantation. PCB tumors do not transplant. 4. Tumors Influenced by promoters are often affected by factors such as nutrition, stress, chronic Injury, and sex of the animal. Liver tumors are affected by these factors. 5. Promoters need not be mutagenic. PCBs are not mutagenic. 6. Neoplastic lesions Increased by promoters may be reversible. PCB-Increased liver tumors regress. 7. Progression of differentiation of neoplastic lesions increased by promoters often ceases when the stimulus Is removed. Continued presence of PCBs Is regulred to sustain liver neoplasia. S. Neoplastic effects of promoters are usually associated with the chronic dysfunction of the affected site. PCBs produce chronic hepatotoxlc responses. 9. Promoters do not necessarily Increase the effect of carcino gens acting at the target site. PCBs reduce the response of several other liver carcinogens. 10. Promoters affecting the liver often Increase microsomal enzyme activity and eventually produce evidence of metabolic dysfunction. PCBs stimulate LME and produce metabolic dys function. 2-7 HONS 01588* U. Promoters rarely, if ever. Increase tumor incidence at expo sure levels producing no toxic effects. PCBs are tumorogens only at toxic doses. 12. Promoter effects often require continued presence of the stimulus. Continued presence of PCB is required to sustain neoplastic alterations of the liver. Comparison of the Characteristics of Carcinogens (Inltlators/Genotox1c) and the Effects of PCBs 1. Carcinogens usually produce neoplastic lesions at multiple sites. PCBs Increase lesions of the liver only, 2. Carcinogens often Increase the malignancy of spontaneous tu mors at the same site. PC8-1ncreased liver tumors are of low malignancy. 3. Carcinomas irreversibly progress once a critical tissue mass is established. PC8-1ncreased tumors can regress. 4. Carcinogens produce tumors which metastasize. PCB-Increased liver tumors do not metastasize. 5. Carcinogens produce lethal tumors. PCB-increased liver tu mors are not lethal. 6. Carcinogens produce transplantable tumors. PCB-increased liver tumors do not transplant. 7. Carcinogens are often effective at single exposures. PCBs Increase liver tumors only after prolonged, continuous exposures. B. Carcinogens are often active at nontoxic doses. PC8s only Increase liver tumors at hepatotoxic doses. 9. Initiators are mutagens. PCBs are not mutagens and therefore are not Initiators. 2-8 HONS 015885 It ts apparent that the neoplastic effects of PC8s match the def initions of a promoting agent am) do not match the definitions of an Initiator. It might also be mentioned that Butler and Jones (1978) have pre viously stated that certain compounds, especially persistent chlorin ated compounds Including PCBs, Increase the Incidence of only liver tumors In rodents and that these tumors may not be malignant. In fact, halogenated chemicals are the most numerous class of chemicals to induce rat or mouse liver tumors alone, and most are known not to be mutagenic. These chemicals produce liver cell damage and regenera tion and/or Induction of hypertrophic and hyperplastic changes. Thus, it Is likely that these nonmutagenlc chemicals are causing rodent tumors by an epigenetic mechanism. This distinction concerning the halogenated hydrocarbons has been noted by other scientists as well. For example, Welsburger and Wil liams have stated: Validation of this concept of a promoting rather than a genotoxlc action of chlorinated hydrocarbons Is not only an Important distinction from a theoretic point of view, but Is even more relevant In terms of regulatory actions Indicated to prevent chronic disease. They further reiterated this Idea by stating: If, on the other hand, no convincing evidence for genotoxIclty Is obtained, but the chemical is carcinogenic In animal bioassays, then the possibility exists that the chem ical Is an epigenetic carcinogen. The strength of this con clusion depends on the relevance of the In vitro tests. For example, the finding that certain stable organochlorine pesticides do not display genotoxlc effects in liver cell systems, which are Identical to the In vivo target cell for these carcinogens, strongly supports the Interpretation that these carcinogens may act by epigenetic mechanisms. The nature of these mechanisms Is poorly understood at present and Is probably quite different for different classes of carcinogens. They may Involve chronic tissue Injury, Immunosuppressive effects, hormonal Imbalances, blocks in differentiation, promotion of pre-existing altered cells, or processes not yet known. In conclusion, we have raised the question. Does one experiment utilizing prolonged exposures at high levels, In a single sex of a 2-9 HONS 015886 single strain, Incriminate commercial PCBs as a carcinogen? To answer this question, we have reviewed the pertinent current theories of carcinogens, the scientific body of knowledge which supports these theories, and have provided an analysis of the chemical carcinogenesis testing performed with PCBs. On the basis of the data that have been reported In the last few years, PCBs do not appear to be carcinogens (initiators). At worst, PCBs at high or elevated doses meet some of the cri teria for a chemical promoter, l.e., they enhance tumor growth through epigenetic mechanisms but do not Induce new tumor growths. This dis tinction Is of extreme Importance and can be made based upon the known mechanisms for Initiators and those for promoting agents. PCBs demon strate many characteristics of the latter and none of the former. A further Importance of this distinction Is that PCBs have only been shown to possess a weak promoting activity, at most. Therefore, the thresholds both proposed In theory and observed In animal studies sug gest that there are safe exposure levels for PCBs. MOWS 01588? MO HONS 015888 3. RISK ASSESSMENT AS PART OF THE REGULATION OF PCBs: STATEMENT OF PURPOSE, NEED, AND LIMITATION The Increasing use of chemicals and our ever-growing realization of their Impacts on human health necessitate a scientific basis from which to determine the largest quantity of a chemical. If any, that could be absorbed over an Indefinite period without producing adverse health effects. For this purpose, the toxicologist has long relied on dose-response relationships to guide extrapolation downwards from the observed range to estimate a "safe" dose. A general premise of toxi cology has been that the extent of induced adverse effects Is closely related to the extent of exposure. Some Interested parties have called for an exception to this established toxicological concept, suggesting that chemicals should be considered either as carcinogens or noncarcinogens, regardless of dosage Involved. Many toxicologists continue to maintain that carcinogenesis, although complicated, is in fact consistent with classical toxicological concepts. National ef forts have been made by several government agencies to develop a data base for evaluating test procedures used In the detection of cancer, as well as to develop methodologies for performing risk estimations for chemically Induced cancer. Undeniably, chemical technology has In a large measure contrib uted to the achievement of the present standard of living. It has produced many of the tools and resources needed to reduce human suf fering and to modify selective pressures of the environment. Accompa nying these benefits, however. Is the possibility that toxic proper ties of certain chemicals have the potential to threaten man's health. 3-1 MOMS 015889 Therefore, a rational policy for chemical utilization is to produce the highest standard of living consistent with a quantitatively ac ceptable hazard-to-benefit ratio. A product containing chemicals should be approved for use if there is an acceptable margin of safety between the anticipated expo sure and the level estimated as hazardous to humans or the environ ment. Yet, to accomplish this task, the toxicologist must face the dilenma of estimating the risk to an enormous and variable human popu lation by extrapolating the hazards determined from studies conducted on small numbers of environmentally controlled and genetically homo geneous experimental animals. With the limitations of present experi mental and theoretical techniques, there is considerable potential for error in assessing both sides of the hazard-to-benefit ratio. For these reasons, the limitations of toxicological evaluations should be clearly stated. It never has been, and is not now possible to guaran tee absolute safety. Small populations of experimental subjects, either animal or human, may provide an imprecise estimate of hazard for comparison to a large human population of variable genetic disease states, cultural backgrounds, and ages. Mays of overcoming these lim itations are slowly being recognized, and techniques for extrapolation must make maximum use of available data. Thresholds As a prologue to the discussion, it must be stated that we should resist falling into the Intellectual and experimental quagmire called "threshold" and the mischief of "value judgement.' There Is no mathe matical reason to distinguish cancer from many other toxicological effects. For cancer or any measurable response that may theoretically lack a threshold, the no-effect dose merely becomes a sample-sizedependent phenomena. To argue threshold is to obfuscate. Me will later develop the thesis that time is the critical point of considera tion. The concept of a threshold dose Is based on the premise that un less a specific set of conditions exists, some smaller dose will not produce the measured effect. For carcinogens (i.e., initiators), since there always exists the possibility of a response, the threshold limits of an effectively measured response only depend upon the sample 3-2 HONS 015890 size In a statistically significant evaluation. This does not mean that thresholds do not exist, nor does it mean that thresholds cannot be estimated in a practical manner. It does not mean that bounds can not be established. It only means that thresholds are not absolute and cannot be defined with absolute certainty. In fact, if known, they might yield little practical relief to our current dilemma, since under the preceding limitations time, rather than dose, may become the critical and determining factor of risk. This stems from our percep tion that as the dose decreases the latency period increases. There fore, time is the most appropriate medium to describe the magnitude of excess risk or reduced quality and quantity of life due to neoplastic lesions. Finally, we have demonstrated that PCBs are not genotoxtc; therefore, the no-threshold arguments do not apply. Germane to the modification of risk determinations by combining socially accepted values is the consideration of the hazard/benefit margin. Some chemicals may be considered essential insofar as there is no substitute process considered less hazardous, or for which the requirements of a replacement strategy outweigh or replace the origi nal health concerns. For such chemicals, a relevant approach to con trolling the risk is to permit only those uses for which the absence of hazardous exposures of the chemical can reasonably be assured. The cornerstone of this strategy requires that we define the hazard, then determine the amount of exposure which is not expected to be hazard ous, whtch In turn defines the limits of the sensitivity of the ana lytical methodologies required. Rephrased, the requirements of the analytical methodology and the limitations of chemical use would be defined toxicologically by the acceptable risk rather than as a function of the state of the art of analytical chemistry. The alternatives, zero-residue rules (such as found in the Delaney Clause) or risk analysis based upon an endless series of conservative presumptions, are inadequate and unusable in several respects. Such alternative approaches provide a false sense of security by ignoring the problem of "false negatives," which may result from chance or inadequate testing. In addition, they encourage poor and limited experimentation, since the less we do and the less precise we are, the less chance we have of determining anything at a statistically significant level. Moreover, these alternative HONS 01591 3-3 approaches capriciously eliminate from consideration the use of chemi cals whose benefits might be documented to outweigh a worst-case cal culation of the carcinogenic hazard. Value Judgement and Emphasis Ambiguities In the process of articulating an acceptable safety policy will automatically arise If proposed criteria require Incorpor ation of the unobtainable goal of attempting to prove scientifically that no deleterious effect will take place, l.e., to prove the absence of the possibility of an occurrence In some future time. Examples have been described by Or. Alvin Weinberg as "transclence." Such a policy postulates society's need to Insure an absence of positive findings beyond the range of the methods available for data collec tion. Toxicologists' tools, however, are limited to experiments oaploylng the scientific method. These experiments are usually designed to establish that phenomena resulting from repeated experimental ma nipulations are real, are not artifacts, and have not occurred simply by chance. We are all aware that positive as well as negative findings may be artifacts and that In most scientific disciplines there Is a posi tive reward for Investing In adequate techniques and replication of experiments. Insistence on any desired degree of assurance against making a wrong conclusion Is standard operating procedure. The qual ity of safety evaluations will suffer If we adopt Ingrained unidirec tional attitudes which demand that, once we find a positive carcino genic effect, no number of negative studies provide an adequate coun terbalance. Such attitudes inappropriately Ignore false positives and discourage rigorous and repeated experimentation by even the most re sponsible sponsor. In addition, this emphasis places the sponsor and the conscientious regulator alike In the position of being bludgeoned with experiments carried out by third parties under conditions that often are not appropriate for safety evaluation or for which the re sults have not been validated. This dllemna ferments frustration, and inevitably Intellectual problem-solving deteriorates Into arguments of the wrong Issue--for example, thresholds. HONS 015892 3-4 Why Are Traditional Models Inapplicable? When direct measurements are Impossible, assumptions must be made If we are to be able to extrapolate a cancer hazard from animal stud ies at relatively high dose rates to human population cancer hazards at intermittent and low dose rates. Thus, one set of assumptions we must face concerns the description of the function relating the real hazard measured at high dose rates to a theoretically estimated animal risk at low dose rates. The magnitude of low dose risk Is highly de pendent upon the assumed shape of the dose-response function, and for neoplastic disease we must consider time. Unfortunately, the shape of the curve at low dose rates for most models is much more sensitive to manipulating the extrapolation procedure than to the experimental data. This has led to the discouraging observation that, for most models advanced to date for regulatory purposes, extensive experimen tation and quality assurance means less than arbitrary mathematical manipulation, e.g., worst-case confidence limits. The extreme differences between models for extrapolating to low risks have been reviewed In detail elsewhere and a summary is pre sented in Table 3-1. The probit, logistic, and one-hit curves can all be shown to calculate that one-fourth of a dose producing a 50* tumor Incidence will produce a 16* tumor response. The families of curves generated by these models are Indistinguishable in the range usually described by most experiments, that Is, the 8* to 92* tumor response. However, several thousand animals would have to be tested In order to distinguish with confidence between predictions by the probit and lo gistic models In the 2* to 4* response. Hence, extreme differences between the estimated doses generated by the three models are noted when extrapolating to an upper confidence of no more than a one in a million risk. The "extreme value* curve, another possible model, would gener ally lie between the probit and logistic, depending on the slopes se lected. The choice of an extrapolation model is critical, but the parameters to be adjusted in the use of the model, particularly the slope and upper confidence intervals, are even more critical. The logistic analysis can also be rejected because the logistic function, as originally proposed by Reed and Serkson in 1929, is an empirical form of a series of at least six equations obtained by dataflttlng and not by any form of derivation. In addition, the forms of 3-5 HONS 015893 Table VI DOSES ACQUIRED TO PUCC UPPER LIMITS ON ESTIMATED RISKS Catieetad Rialt 10~J >-4 10-8 Probit 1/67 1/714 1/2440 Loqietic 1/323 V?.a io5 1/4. J IQ4 Ona-Hit 1/714 1/7.H 10S 1/7.14 107 HONS 015694 3-6 the logistic are uncertain since different investigators use different equations, and the different slopes and intercepts thus obtained are without physical meaning, even in well-defined chemical or biochemical systems. The logistic equation has a mathematical form similar to the Hill equation that Is based on the mass-action law. Thus, there seems to be no reason to use the logistic function. Even for a particular model, for example the probit, nondata fac tors influencing the model can produce widely different extrapolation results (Table 3-2). For comparative purposes, dose-reduction factors for a risk not to exceed one in a million are given in Table 3-3 using probit of slope of one. It is obvious that application of the most refined methods of observation or changing diagnostic criteria can lower any observed threshold. For example, if we consider hyperplasia as the endpoint rather than neoplasia, we shift the threshold. Repeating the bioassay will demonstrate variability even among genetically equivalent indi viduals. Phenotypic heterogeneity of any population and micro environments will be expressed and will Influence the responses ob served. Almost all toxicologists believe that for any compound and for given conditions a "biologically insignificant dose" exists. There is little doubt that this Is true; however, so far no acceptable approach has emerged for cancer risk assessment since a consensus on the definition of "insignificant" has not been reached. Low Pose Models Most investigators g-appling with low dose extrapolation problems agree that we must continue to develop mathematical models describing hazards from carcinogenesis. A more fundamental insight into the re lationship which undoubtedly prevails between dose and excess response at low constant dose rates is of critical Importance. Much effort has already been expended. Crump e^al_. (I), Suess et al_. (4), and Peto (5) have Invoiced certain hypotheses of carcinogenesis to argue that the possibility of linear responses at low doses must be considered. For example, Crump et al_. (1) and Guess et_ al_. (4) offer the proposi tion that the probability, P(d), of response at dose rate is given by: P(d) * I-exp[-(a0 + ajd + ajd^ + ....)], 0. 3-7 HONS 015895 Tabl* 5-2 FACTION or EXPtRIKNTAL DOSE riaoifc ZERO TUMORS USING PROBIT EXTRAPOLATION WITH DIFFERENT SLOPES FOR AN ESTIMATED RISK NOT TO EXCEED ONE IN TOO MILLION Tumor* 0b**rvd t Oo* 0/50 0/100 0/500 0/1000 Fraction oF Dom X Not Exc**<Ung Risk Slop* * 1 X/18,000 X/ 8,300 X/ 1,800 x/ 1,000 Slop* * 11.5 X/690 X/410 X/150 X/100 Slop* a 2.0 X/135 X/ 91 X/ *2 X/ 32 HONS 015096 3-8 Tabla V5 FRACTION OF EXPERIMENTAL OQSE USI* PROSIT EXTRAPOLATION WITH A SLOPE OF QIC WHICH IS CALCULATED TO PROOUCE tt* EST1IWTCD UPPER LIMIT RISK NOT TO EXCEED ONE IN A MILLION Tumors Obssrvsd st Dos* X 0/50 0/100 0/500 0/1,000 Fraction of Cxpanmantal Ooaaga X/2,500 X/1,140 X/ 230 X/ 140 HONS 015897 3-9 When P(d) is small, the excess risk P(d)-(0) is approximately P(d)-P(0) a^d + a^d? + .... and the pseudo-question of nonthreshold low-dose linearity for pur poses of modeling Is determined by whether or not the coefficient aj Is zero. There are plausible assumptions, such as detoxification mechanisms, QUA repair, or the necessity for multiple molecular Inter actions, that lead to aj 0. There are also plausible assumptions for some agents that can lead to positive values for a^. We will almost never have the knowledge to completely discriminate between these alternatives. Acceptable approaches to extrapolation must make efficient use of what experimental data we have or can get. Injection of value judgements, such as selected worst-case confidence limits In place of central expected values for the coefficients aj, Incorpor ates a bias value judgement Into the extrapolation procedures that almost always outweighs the Information Inherent In the data. When one applies selected worst-case confidence limits rather than the cen tral expected value (l.e., the most likely value) for aj It Is equivalent to accepting that ai is positive. At low dose rates, this value judgement (such as an arbitrary worst-case confidence lim its) dominates the remaining terms. The requirement to use upper con fidence limits rather than central expected values In fact guarantees that models will yield nonthreshold linearity at low dose rates. Mas querades should not be necessary. If a policy calls for the selection of nonthreshold linear models, let us state so clearly and forth rightly. The arguments associated with masked conservatism have be come redundant, predictable, and Intellectually unappealing. The lack of mathematical logic supporting certain value Judge ments becomes apparent when they are applied to the procedures of Crump et a]_. (1) and Guess jrt aK (4). Techniques become untenable when they are Insensitive to responses at experimental dosages and fall to distinguish between low levels of potent carcinogens and noncarcinogenic substances. Guess et al_. (4) have documented this by constructing two sets of dose response data for a noncarclnogenlc agent. One simulation contained ISO responses at each of 10 dose rates, while the second was made up of 300 responses at each of 5 dose 3-10 MQNS 015*98 rates. In both cases, as Mas predicted, the 90S upper confidence limit on aj was positive. It then follows that the upper confidence limits on curves relating limits of possible extra response to dose rate will always appear to be linear at low dose rates. The predicta bility of false positive prediction of nonexistent risk supports the contention that the value judgement Inherent In the use of worst-case confidence limits Is not always appropriate. Value judgements should be delineated or completely separated from the quantitative use of mathematical models. Another example of a mathematical procedure Is provided by Gaylor and Kodell (3) In their study of 14 sets of toxicological dose re sponse data previously described by the Scientific Comnlttee of the food Safety Council (2). The behavior of a garnna multihit model was purported to be compared to the Armltage-Ool1 multistage model for low dose extrapolation using the technique gl.ven by Crump et^ ah (1). The Saylor and Kodell Armltage-Doll multistage model results did not exactly agree with the Scientific Committee of the Food Safety Council data because the limits calculated by Gaylor and Kodel did not assume a maximum degree of dose In the exponential term, whereas the limits calculated by the Food Safety Council took the degree of dose as fixed. Gaylor and Kodell (3) concluded that: "Conceptually linear extrapolation would (should) be more conservative, but this Is not the case In actuality, apparently because more stringent mathematical as sumptions and conditions are required" (by the gamma one-hit model). Selected examples are given In Table 3-4. The examples given In Table 3-4 reinforce the recommendation made by the Scientific Committee of the Food Safety Council (2) calling for reason when mathematical Interpretations affect real-life decisions: Although the value judgement involved In the use of conser vative risk assessments may seem appropriate in the light of the many scientific unknowns involved, once formalized as a specific mathematical procedure It escapes the control of the decision-maker and can lead to undesirable and unsound results by distorting the balance between risk and benefit. Me, therefore, recommend the separation of the mathematical and societal aspects of the problems, with the extrapolation procedure chosen to provide 'best estimates' of risk as well as their upper or lower limits. The toxfcological and mathematical uncertainties associated with extrapolating risks from relatively high experimental dosages In 3-11 HONS 015899 Tab1* J-4 LONER 97.55 CONFIDENCE LIMIT FOR 00SAGES PREDICTED TO HAVE A RISK OF LESS THAN OC MILLION IN ROOENT POPULATIONS Subfttanc* Doftft Unit AfUtoxin Vinyl Chloride Ethy Unftthiourftft Oitldrin OOT PP PP ppn PP* ppn Sex. Con. TSC 1970 5.A a 10 1.6 x IQ'3 A.A x 10*4 9.4 x tO'4 2.0 x I0'2 Lxrtftflr 7.9 x 10"4 7.1 x tO'* 1.0 x to"4 5.7 x 10'4 3.4 x I0'5 Ar*itagft-OoU 5.9 x 10"4 5.2 x 10"4 3.2 x tO-4 2.9 x 10 2.4 x to'5 3-12 HONS 015900 animals to low human exposure levels are often cited as a principal concern of those who call for complete prohibition when a chemical has been "demonstrated" to be a carcinogen. A slight modification of this approach is to use a series of conservative assumptions for data presentation followed by linear extrapolation or eouivalent "model" use from upper confidence limits of the experimental results to a zero response at zero dosage. Since rodents, the principal bioassay species, have substantial rates of neoplastic disease at many sites, such an approach invites the option of declaring almost any thoroughly studied compound a carcinogen. PCBs are just such an example when one weighs all the negative studies against the single positive study of Kimbrough. Evaluation of Criteria and Calculations of Risk from PC8s for Hu mans by Crump "1 We have now discussed the lack of mathematical logic supporting use of certain value judgements. In addition. Crump violated his own criteria for Justifying the selected model for PCB risk analysis. This can be demonstrated with Crump's own words. Crump states in ex plaining his approach to risk analysis for PCBs: Tumors of so many different types arise in such a diversity of different tissues, their etiology is so little under stood, and the agents that cause tumors affect a subject in such diverse ways, that it might seem that no general con clusions can be drawn. However, for a certain broad class of 'directly-acting' chemical carcinogens the range of un certainty associated with the shape of the dose response curve at low doses can be greatly narrowed. As used in this paper, the term "directly-acting carcinogen" encompasses (Guess, Crump and Peto, 1977) carcinogenic agents for which either the agent Itself or a metabolite acts directly at the cellular level and produces a hereditable change which even tually leads to the formation of a tumor. Carcinogens which are carcinogenic by reasons of their mutagenicity should fall into the category of 'directly-acting carcinogens.' Accordingly, carcinogens which test positively using the Ames mutagenicity screening test for carcinogenicity are very likely to be directly-acting. The available data suggest that even if Crump's statement was true, the concept could not be appropriately applied to PCB risk analysis since PCBs are not direct-acting carcinogens as demonstrated by scientific literature. For example, the Ames assay utilizes 3-13 HONS 015901 Salmonella typhlmurlum to detect reverse-point mutation at the histi dine locus. Only 4-chloroblphenyls have demonstrated any activity In the Ames 1538 tester strain. In this same study, PCSs such as 2, 2', 5, 5' tetrachloroblphenyl, 1254, and 1260 were negative. In supsequent studies, not even the positive for monochlorobtphenyl could be reproduced. It has been demonstrated that PCSs do not cause significant clastogenlc effects In rat bone marrow or sperm cells even at high doses. Aroclor 1242 was given at a single dose of 1,250 to 5,000 mg/kg and at 500 mg/kg for four days (a regimen causing the condition of the ani mals to deteriorate), while Aroclor 1254 was given at doses of 75 to 300 mg/kg for five days. These findings are consistent with the lack of chromosomal aberrations observed In human lymphocyte cultures with doses of 100 mg/kg Aroclor 1254. The possible mutagenicity of PCSs has also been studied using the dominant lethal test. There was no statistically significant Increase In the number of dead Implants, again at high dosages of Aroclor 1242 and 1254. This test, the dominant lethal assay, has been repeated and again the results were negative. PCBs do not have significant muta genic potential. Crump continues to try to Justify his models and approach taken for risk estimation for PC8s by stating: A partial solution to the low-dose extrapolation problem for the case of directly-acting chemical carcinogens has been given In Peto (1977), Crump, Hoel, Langley and Peto (1976), and Guess et al. (1976). The key result is that, at least as long as~EacFground carcinogenesis is present, we should expect the dose response curve not to be absolutely flat at zero dose. What this means is simply that when risk Is plotted against dose response on ordinary linear scales, the tangent line to the dose response curve at zero dose should have a positive slope. When a dose response function has this property we will say it is linear at low dose. Crump also offers a possible explanation of why the dose response function should be linear at low dose *4>en background is present (Crump, et aK 1976), as does Peto (1977), which will be briefly out lined here. Crump et al_. and Peto argue that when background carcino genesis Is present, the cellular mechanisms through which the test agent produces cancer should already be operative In producing back ground tumors. When this Is true, the effect of the test agent Is to 3-14 HONS 015902 add to any already ongoing process. The dose response curve is for all tumors produced through the mechanisms through which the test agents acts. Background carcinogenesis is allowed for by an effective background dose d0. In this case, the added risk caused by a dose d of the test agent could be expected to increase approximately linearly near d 0 (i.e., the tangent line at d * 0 will have a positive slope). Implicitly assumed is the fact that an added dose of a car cinogen acting through this mechanism does not produce a smaller risk. If background carcinogenesis is allowed for by positing an effective background dose d0 estimated from the data, then the wide range of risks obtained using different models effectively disappears (Peto 1977) because they all approach a simple linear model. The Crump and Peto argument does not apply to PCBs. That the liver cancer rate Induced by direct-acting carcinogens is not added to by PCBs has been demonstrated on several occasions. The effects of PCBs on carcinogenicity of various chemicals have been investigated by numerous groups. Kanechlor-500 in combination with 3' methyl-4dimethylaminoazobenzene, N-2-fluarenylacetamide, and diethylnitrosamine in the diets of rats markedly decreased the formation of hepatocarcinomas. Kimura et al.. demonstrated that pretreatment with Kanechlor400 in diets of rats 4 months prior to and 2 months during treat ment with 3' methyl-4-dimethyulaminoazobenzene protected the rats against the formation of hepatocarc1 nomas induced by this carcinogen. The two-stage system of mouse skin tumorigenesis allows one to evaluate critically the initiation and promotion phases of carcinogen esis individually. This system allows one to study the effects of modifiers on initiation and promotion separately in a skin carcinogen esis assay. The results of Berry et al_. demonstrate that PC8s possess the capacity to decrease tumor initiation in a mouse skin assay and that at the doses utilized, PCBs had no initiating or promoting prop erties. Their study tested PCBs for promoting activity in mouse skin with a high (200 nmol) Initiating dose of DMBA. In a 30-week treat ment period, the normal DMBA-initltated, TPA-promoted controls yielded approximately 8 papillomas per mouse. PCBs (at doses of 100 ug/mouse given twice weekly) did not promote the development of skin tumors. 3-15 HONS 015903 When tested without DM8A Initiation, PCSs did not demonstrate any car cinogenic activity. PCBs did not produce any observable skin lesions. Crump himself Invalidates the model's use with the linear low dose assumption for PCB risk analysis when he states: The evidence for low-dose-llnearlty given above applies mainly to directly-acting carcinogens. An Indirectly acting carcinogen might be one which causes some gross physiologi cal change such as suppression of ovulation which could pre dispose the subject to cancer. For such carcinogens the shape of the dose response curve at low dose Is highly spec ulative. There could possibly be a threshold dose below which the agent has no carcinogenic effect at all on an In dividual . ' The reader should be reminded that for the purposes of the dis cussion, promoter and Indirect carcinogen can be used Interchangeably. That PCBs are at worst an Indirect carcinogen Is supported by a large amount of data. PCBs Induce microsomal mixed-function oxidases and cause hepatomegaly in rodents and other mammals. Heptomegaly has been Interpreted by Kimbrough to be the result of the hypertrophy of Indi vidual hepatocytes. Hyperplasia also commonly occurs and Increased mitotic activity can occasionally be noted. Hepatocytes enlarge and may accumulate lipid In their cytoplasm. At the ultrastructural level, enlarged hepatocytes show an Increase in smooth endoplasmic reticulum and Inclusions within the cytoplasm, which appear like con centric whorls, surrounding lipid vacuoles. Morphologic changes In the mitochondria have also been described (Kimbrough et aK 1972). In addition to these alterations, PCBs induce experimental hep atic porphyria. In the rat, experimental hepatic porphyria only oc curs In the Sherman strain female. This observation indicates a unique sensitivity for the Sherman female rat. On microscopic exami nation, an Increase (n macrophages and prominent kupffer cells con taining brown ceroid pigment and necrobiosis of liver cells is promi nent. Lipid accumulates In the cytoplasma of hepatocytes, resulting at times In hepatocytes with foamy cytoplasm. Acute as well as chronic toxicity of PCBs has been studied in rats, monkeys, mice, and cows. The organ consistently affected was 3-16 HONS 015904 the liver. For example, when male Sprague-Oawley rats were fed a diet containing mixtures of PC8 Isomers (Aroclor 1248, 1254, and 1260) at a concentration of 100 ppm In the diet far 52 weeks, there was an In crease In their sertm lipids and cholesterol, and a transient Increase In triglycerides accompanied by distinct morphological changes in the liver. Generalized liver hypertrophy and focal areas of hepatocellu lar degeneration were followed by a wide spectrum of repair processes. The tissue levels of PCS were greater In the animal receiving the high chlorine mixtures and high levels persisted after the PCB treatment had been discontinued. ' Summary Supporting the Statement that PCBs Are at Horst Indirect Carcinogens (Promoters) 1. Promoters produce increases of spontaneous tumor at selected sites. PCBs only produce liver tumors in rodents for which there is a spontaneous occurrence. 2. Tumors produced by promoters usually do not Increase the metastatic characteristics of spontaneous tumors of the same global (direct-acting) site. PCB increased liver tumors do not metastasize. 3. Promoters do not produce transplantable tumors unless the naturally occurring tumor Is capable of transplantation. PCB tumors do not transplant. 4. Tumors Influenced by promoters are often affected by factors such as nutrition, stress, chronic injury, and sex of the animal. Rodent liver tumors are affected by these factors. 5. Promoters need not be mutagenic. PCBs are not mutagenic. 6. Neoplastic lesions Increased by promoters may be reversible. PCB Increased liver tumors regress. 3-17 HONS 015905 7. Progression of differentiation of neoplastic lesions in creased by promoters often ceases when stimulus is removed. Continued presence of PCBs is required to sustain liver neo plasia. 8. Neoplastic effects of promoters are usually associated with the chronic dysfunction of the affected site. PCBs produce chronic hepatotoxic responses. 9. Promoters do not necessarily increase the effect of carcino gens acting at the target site. PC8s reduce the response of several other liver carcinogens. 10. Promoters affecting the liver often Increase microsomal en zyme activity and eventually produce evidence of metabolic dysfunction. PCBs stimulate IME and produce metabolic dys function. 11. Promoters rarely if ever increase tumor incidence at exposure levels producing no toxic effects. PCBs are tumorogens only at toxic doses. Characteristics of Initiators (Direct-Acting Carcinogens) 1. Initiators usually produce neoplastic lesions at multiple sites. PCBs only increase lesions of the liver. 2. Initiators often Increase the malignancy of spontaneous tu mors at the same site. PCB-increased liver tumors are of low malignancy. 3. Carcinomas irreversibly progress once a critical tissue mass is established. PCB-increased tumors can regress. a. Initiators produce tumors which metastasize. PC8-increased liver tumors do not metastasize. 3-13 HONS 015906 5. Initiators produce lethal tumors. PCB-Increased liver tumors are not lethal. 6. Initiators produce transplantable tumors. PCB-increased liver tumors do not transplant. 7. Initiators are often effective at single exposures. PCBs increase liver tumors only after prolonged continuous expo sures. ' 8. Initiators are often active at nontoxic doses. PC8s only increase liver tumors at hepatotoxic doses. 9. Initiators are mutagens. PCBs are not mutagens and therefore not Initiators. It is apparent that the neoplastic effects of PCBs match the defini tions of a promoter and do not match the definitions of an initiator. We have established that the rationale for Justifying the technique for analysis of PCBs by Crump is Inappropriate when compared against Crump's own criteria. Conclusions About the Application of Linear Extrapolation and the Equivalent wonthreshoid Models to Risk Analysis of PCS? We will establish our thesis when we thoroughly analyze the risk analysis offered by Crump. When referring to his modeling efforts. Crump states, "The expected numbers of extra cases of hepatocellular carcinomas per year resulting from a nationwide exposure at a dietary level detected in the 1976 Total Diet Study (3.3 uug/day) would range between 220,000 (288,000 x 70) 11.1 cases/year and 220,000,000/ (764,000 x 70) * 4.1 cases/year." Crump misleads the reader by suggesting that the mathematical model used to generate these numbers brings logic to the effort. For example, if one simply takes the ratio of animals with and without liver tumors at 100 ppm in the Kimbrough study, divides by the esti mated human exposure (1 ppb), then multiplies by the size of the human population In the United States (220 million), and finally divides by the human lifespan of 70 years, one gets the same answer as Crump: 3-19 HONS 01590? 26 tunors/134 animals 1 ppb PCB/200 ppm PC3/70 years 1 4.3 cancers/year. Crump's analysis of risk to infants Is markedly overstated. A rat consumes approximately 10* of its body weight per day. Feed with 100 ppm PC8 equals a consumption of 100 mg/kg. Therefore, a rat con sumes the equivalent of 10 mg PCB/kg/day. If the human milk sample was 2* fat, then the whole milk would contain 2X of the 4 ppm Crump considered, or .08 ppm. A liter of milk would contain .08 mg of PCB. A child weighing 5 kg would have to consimie 750 liters of milk a day to equal the exposure of the rats. If the child truly only consumes 1.5 liters a day, then there Is a 500-fold difference in exposure rate between rat and baby. If the baby Is exposed, as suggested by Crump, for only 1/140 of Its lifespan, this has to be considered. The 500-fold difference times the 1/140 of the lifespan Is equal to a 70,000 exposure differ ential. The linear risk as calculated by Crump's technique would be 2/1,000,000, not the 1/4,800 reported by Crump. If we approach the problem another way, we obtain other interest ing comparisons. The PC8 dose to high exposure women averaged 1.7 ug/kg/day. A lactating female maintaining her weight would then have 1.7 ug x 50 kg, or 85 ug/day of PCB, available for transfer to the baby. If the baby weighs 6 kg, the dose Is 14 .ug/kg/day. This, when compared to the 10 mg/kg/day dose to the rats, yields an exposure ratio differential of 700 times. The exposure period of 1/140 times the exposure ratio yields a total exposure risk of 98,000 times less for the human than the rat. The linear risk as calculated by Crump's technique would be 1.4 x 10 not the 1/4,800 reported by Crump. If we Insist on linear extrapolation, what are the relative risks? let us assign an average exposure resulting in 500 ppb blood level to capacitor workers, 70 ppb to the heavy fish eaters In Michigan, and 20 ppm to the general Michigan population, let us assign an exposure of 12 ug/kg/day to the capacitor workers, 1.7 ug/kg/day to the fish eaters, and .5 ug/kg/day to the general population. These estimates were taken from the documents of Crump and the EPA water quality criteria for PCBs. 3-20 MONS 015908 The rats In the Kimbrough study were exposed to 10,000 ug/kg/day. Therefore, the ratio of exposure between rats and man Is: Capacitor worker/rat * .0012 Fish eater/rat - .00017 General populatlon/rat .00005 The chances of dying from liver cancer can be expressed In several ways. For example, 816.3/100,000 Americans die each year from all causes. The Incidence of liver cancer disease Is 3/100,000. This translates to a .37* chance of liver cancer. Expressed another way, there will be about 2,000,000 deaths In 1981 and 9,400 are estimated to be from liver cancer. Therefore, 9,400/2,000,000 equals a .47* chance that the registered death will result from liver cancer. This estimate will be rounded off to a .5* chance for the purposes of our discussion. If the risk were linear (and the risk to humans Is the same as in rats, or .14), then the risk In man would be .00017 for capacitor workers, .00024 for fish eaters, and .000007 for the general popula tion. Expressed another way, the risk to humans for liver cancer would Increase to: Capacitor worker Fish eater General population .005 * .00517 * .01017 .005 + .000024 .005024 .005 * .000007 .005007 Thus, the cancer mortality data suggest that there Is only a slight possibility that the actual risk for capacitor workers would be higher; however, the data are far from conclusive. It Is also obvious that It would be impossible to determine epidemiologically the tiny Increases expected to occur either In the fish-eating population or in the general population. Let us approach the problem from a different viewpoint. Let us suppose that our risk analysis should be conducted on a relative risk basis. If the relative risk to rats at 100 ppm is 26, and the same exposure ratios between rat and man hold, then the risks are as fol lows: 3-21 HONS 015909 Capacitor worker .005 Fish eater .005 General population .005 + .0012 x + .00017 x + .00005 x 26 * .0362 (724* background) 26 * .0094 (188* background) 26 * .00552 (110* background) Again, this hypothesis cannot be rejected at the lower exposures because It Is not possible to analyze It on the basis of Information available. However, the capacitor workers aid In the evaluation of this hypothesis since the highly exposed Individuals would demonstrate an Incidence which Is seven times the background Incidence. How Did EPA Analyze the Data? The preceding discussion of human exposure makes clear the fact that a high percentage of the United States population has been and Is exposed to low levels of PC8s In food, water, and air. Those groups at particular risk for PCS exposure Include industrial workers exposed In the workplace and Individuals consuming large amounts of contami nated fish, such as sport fishermen (42 FR 17487). An assessment of carcinogenic risk was made by EPA performing extrapolation from animal data using a linearized multistage (non threshold) model. The extrapolation used was reported to take into account the bioaccumulation of PCBs In fish and shellfish. It Is as sumed that an average of 2 1/day of water are consumed along with 6.5 g of fish taken from that water source. Exposures from other food sources, air, or occupational exposure are not Included In the crite rion level derived by this model. Among the studies reviewed by EPA, only one was considered suit able for use In the cancer risk assessment. EPA made the remarkable statement that, "Of the rat studies, the only one involving long-term exposure and adequate numbers of animals Is the study of Sherman rats by Kimbrough et ah (1975).* EPA goes on to state, "Because there Is no recognized safe concentration for a human carcinogen, the recom mended concentration of PC8s in water for maximum protection of human health Is zero." Since attaining a zero concentration level may be Infeasible In some cases, and In order to assist the agency and states In the possible future development of water quality regulations, the concentration of PCBs corresponding to several Incremental lifetime cancer risk levels have been estimated. A cancer risk level provides 3-22 HONS 01S910 in estimate of the additional Incidence of cancer that may be expected in an exposed population. A risk of 10-5, for example, indicates a probability of one additional case of cancer for every 100,000 peo ple exposed, a risk of 10" indicates one additional case of can cer for every million people exposed, and so forth. In the Federal Register Notice of Availability of Draft Ambient Mater Quality Criteria, EPA stated that It Is considering setting criteria at an Interim target risk levels of 10'5, 10*6, and 10*7, as shown In Table 3-5. If such Is the EPA's estimate, 80 jig/day, how does it compare with other EPA statements and those results gathered in the N10SH and F0A studies? Even when one makes all the conservative assumptions utilized In official PCB cancer risk estimations, one arrives at an swers which are so low as to escape our capability of detecting a pos itive effect via epidemiology. Therefore, one must conclude that mathematical risk estimation, even for the occupationally exposed, yields estimates which are vanishingly small. However, the overzealous use of mathematical models and the assumptions made by the EPA without comparing these results to reality are easily demonstrated. EPA states In the Federal Register Notice of Availability of Oraft Ambient Hater Quality Criteria that the following risk to cancer from PCBs exists, 10*5 cancer risk 80 ng PC8/day. Table 3-6 summarizes known human exposures to the risks calcu lated by an extrapolation of the values. Using estimates performed on preceding pages calculated from ac tual cancer rates In the United States, 9,400/2,000,000 equals a .47% chance of dying from liver cancer. This estimate will be rounded off to a .5* chance for the purposes of our discussion. Using these com parisons, It can be seen from the table above that If the EPA esti mates are correct then 10% of the liver cancer In the United States would be due to PC8 exposure; the Michigan control population would expect a 100% increase In liver cancer Incidence, the Michigan fish eaters would have a 3-fold Increase, the average capacitor worker would have a 10% Incidence of liver cancer or a 20-fold increase, and the highly exposed capacitor worker would have a 25% Incidence of liver cancer or a 50-fold Increase. No human evidence supports any of 3-23 HONS 015911 Tabl* 3-3 cpa interim target risk levels Exposure Assumptions 2 liters of drinking water wri consult Ion of 6.5 g fish end shellfish only4 Cooeumpt lone of fish and shellfish only Risk Lsvsla and Corresponding Criteria* 10*7 to`` I0'5 0.0079 ng/1 0.079 ng/L ,0079 ng/1 0.079 ng/1 0,79 ne/1 (60 ug'ley) 0.79 ng/1 (80 ug/day) iCalculatsd by ^plying a linearised multistage sodal s discussed In the Hutoan Health Appendices to the October 1980 federel Register notice which announced the availability of this document. Since the extrapolation aedel la linear at low doses, the additional Lifatlea rltft is directly proportional to tho water concentration. Therefore, eater concentrations shown in tho t*lo above vary by factors of TO, 100, 1,000, and so forth. 2Approximately 99 percent of the PCB exposure results rrom the con sumption of ajuetle organisms which exhibit an average bioconcsntra tion potential of 31,200-fold. The remaining 1 percent of PCB expo sure results from drinking >eter. 3-24 HONS 015912 Tab La 5-6 EXTRAPOLATIONS OF CPA RISK LEVELS TO A HIGHER LEVEL X HUMAN EXPOSURE Group Blood Cxpoeure Blood Expoaura CPA Cxtrapolatad ftlak Highly axpoaad capacitor workara >1,000 ppb Avaraga capacitor worker 500 ppb Michigan fiah atar 70 ppp Michlcan control population 20 ppb Canaral population 2 ppb 2 *g PCB/day .64 PCB/day .12 mq PCB/day .035 *g PCB/day .0033 mg PCB/day 25% 10% 1.4% .55 .05% 3-25 HONS 015913 these estimates. On the contrary, it is obvious that the EPA standard Is from 10 to 100 times more severe than can be Justified on the basis of human experience, and from 10- to 20-fold more severe than can be excluded on the basis of human experience. As our data base grows. It Is likely that the standard will be found to be at least another order of magnitude too severe. In summary, the rationale that was used by Crump and Masterman In establishing the PCD cancer risk was based on a genotoxlc theory of carcinogenesis and was compiled from a series of ultra-conservative assumptions. These assumptions Ignored the fact that PCBs are not genotoxlc; utilized only the positive data and Ignored the negative data; applied constraints to mathematical models which transformed them to the equivalent of linear extrapolation; Ignored all other com peting causes of death; equated cancer risk In the last moment of life with the risk of a newborn; and exaggerated exposures, for example: assumed that mother's milk was 10M fat, equated all PCSs' toxlcltles as the most toxic results observed for any PCB, and Ignored the rever sibility of PCBs' effects and the marked Improvement In human exposure levels that has occurred In the last five years. Furthermore, using a mathematical model to extrapolate the risk at lower doses does not Increase the reliability of animal data. The most Important question still remains: "Does the animal data reflect the human situation and response?" With the addition of the NIOSH study on capacitor workers to the PCB literature It can be demon strated that the risks estimated using Crump's model are unrealisti cally conservative by serveral orders of magnitude. In a practical sense, a substantial number of people have been chronically exposed to higher levels of PCBs for a longer period of time than that which oc curs for the general population. Since no adverse health effects were causally demonstrated In this population, no measurable adverse ef fects would be expected for the general population. 3-26 HONS 015914 REFERENCES--SECTION 1 1. Crump, K.S., Suess, H.A., and Oeal, K.L., 1977, Confidence Inter* vals and test hypotheses concerning dose response relations In ferred from animal carcinogenicity data. Biometrics, 33:437-451. 2. Food Safety Council: Report of the Scientific Committee, 1978, Food Cosmet. Toxicol., 16: Supplement 2, 1-136. 3. Gaylor, D.N., and Kodell, R.L., 1980, Linear Interpolation al gorithm for low dose risk assessment of toxic substances. 4. Guess, H.A., Crump, K.S. and Peto, R., 1977, Uncertainty estimates for low-dose-rate extrapolations of animal carcinogenicity data. Cancer Res.. 37:3475-3483. 5. Peto, R., 1978, Carcinogenesis effects of chronic exposure to very low levels of toxic substances. Environ. Health Perspectives. 22: 155-159. 3-27 HONS 015915 * HONS 015916 i 4. SUMMARY AND CONCLUSIONS In past decades, a combination of "open" systems and sloppy or Illegal disposal practices resulted In the release of large quantities of chemicals Into the surrounding environment. In the 1960s, when It became apparent that persistent chemicals like OOT and PCBs were ubi quitous environmental contaminants which took years to biodegrade, attention became focused on their potential bloaccumulatlon and the possible negative effects of this on animals and humans. Even though the principal United States manufacturer, Monsanto Industrial Chemical Company, had voluntarily restricted PCB sales to manufacturers of "closed" electrical equipment in 1971, Congress enacted the Toxic Sub stances Control Act In 1976, mandating a phaseout of PCB manufacturing and use. During this time, PCBs were considered as highly toxic and dangerous chemicals capable of causing permanent adverse health ef fects such as cancer and birth defects. In recent years, however, a substantial Increase In scientific data has resulted In a better un derstanding of the actual effects of human exposure to PCBs. It was the purpose of this document to review the data regarding the health effects of PCBs to provide an updated perspective to the PCB Issue. While It Is the consensus of this report that PCBs do not pose the health hazards once feared, this conclusion may be complicated by a contaminant, polychlorinated dlbenzofurans (PCDFs), often found In cornierclal PCB mixtures, which In some special circumstances may pose an Increased risk. Yet PCDFs are only a minor component of PCBs pro duced In America, probably In the range of only 0.1 to 2 parts per million (ppm) of commercial PCBs. In addition, such commercial PCB 4-1 HONS 015917 mixtures Mere apparently the same as those extensively tested over the years. Therefore, the concern for this level of contamination is ex pected to be no greater than that predicted for what Mas previously considered to be "pure* PCBs. It nas not the Intent of this document to determine the full im pact of PCDFs Mlth regard to the hazards associated Mith PCBs. How ever. the PCOF content of PCBs may be increased under conditions of high temperatures, and the possibility of increased toxicity by the presence of this contaminant or others should always be considered when dealing with PCB waste mixtures of uncertain origin. Since the consequences of commercial PCB exposure alone were feared and regu lated in the past, it was this Issue alone which was addressed In this document. Therefore, having brought the above qualifying considera tions to the attention of the reader, this report focused only on those health hazards expected to arise from exposure to commercial PCBs alone. For the benefit of readers whose background and understanding of the field of toxicology, and the principles upon which it Is based. Is minimal, the following short discussion on safety and hazards Is provided to help elucidate the problems Involved In extrapolating test data to human consequences. A poison is an agent that can produce an adverse effect In a bio logical system. This adverse effect may be an alteration of normal function or the destruction of life. The definition of a poison Is broad by necessity and would Include most chemicals. If not all. That Is, all agents are capable of altering some function or producing death In some biological organism. Thus, classifying a chemical as a poison does not describe the most Important feature of poisons, which is those circumstances and conditions under which an adverse effect can be produced. An agent that is a poison produces harm only within prescribed conditions of usage. The safety of an agent can be defined In terms of Its probability for producing an alteration of normal function or causing destruction of life under specified conditions. To determine the safety of an agent, the toxicity of the substance must be determined under con trolled circumstances. Assessment of the toxicity of the agent will define the limits and conditions necessary to produce any adverse 4-2 HONS 015918 effects. The question then ashed Is, "What fs considered safe and under what circumstances?* Critical to this determination Is predict ing the impact of the substance and the variations that are likely to occur within the exposed population. A critical evaluation of experi mental evidence Is necessary to define the probable hazard to man and the magnitude of the hazard. The accuracy of the prediction will de pend on the types of experiments performed; the adequacy with which they have been performed; and, most Importantly, the Interpretation of the experimental results and the limits of the data. The questions to be asked are, "Are PC8s poisons or are they safe? And If they are poisonous, when?" The problem Is thus reduced to predicting an agent's safety based upon experimental evidence and a comparison of the results to the likely levels of human exposure. PCBs can be poisons. That Is, like all other chemicals, PC8s are ca pable of altering normal function and can destroy life under specific circumstances and conditions. Alternatively, PCBs are safe under spe cific circumstances and conditions. The following sunwary of PCB properties and effects is meant to provide a perspective on their safety. PC8s are chlorinated compounds of the biphenyl molecule. Theo retically, approximately 209 separate chlorinated biphenyls can be produced chemically. These compounds have unique physical and chemi cal properties that have made them useful and applicable to many com mercial needs. The physical-chemical properties that make these com pounds useful are their thermal stability; resistance to alteration by acids, bases, and other chemical agents; and their ability to provide excellent electrical Insulation, fire resistance, and low volatility. PCBs are useful as lubricants, heat transfer liquids, and hydraulic fluids. PCBs are ubiquitous to the human environment, as evidenced by their detection In the fat and blood of persons not occupationally exposed to them. These compounds have been Identified In air, water, soils, wildlife, marine organisms, fish, and In our food supply. Thus, to minimize man's environmental exposure to PC8s, the United States Food and Orug Administration (FDA) has set tolerances of 0.5 to 5.0 ppm for the various components of our dally food supply. In the early 1970s, the dally consumption of PCBs was estimated by FOA to be 4-3 HONS 015919 about 15 micrograms per day (ug/day). However, all evidence now Indi cates that the level of dally PC8 Intake by humans is subsiding. Yet these factors have resulted in a major concern for the potential long term effects of PCBs on human health because many of us still contain low levels of PCBs. Owing to their low solubility in water and low concentrations in air, PCBs do not present an acute toxicity threat to either birds or aquatic organisms. In other words, the quantity of PCBs necessary to cause death within a short period of time, such as 96 hours. Is greater than the amount generally found in natural environments. PCBs can cause major problems for some species, however, because these chemicals are persistent, lipid soluble, and resistant to blodegration and/or excretion. Consequently, PCBs can bioaccumulate (build up in quantity within an organism) as well as biomagnify within food webs (accumulate in larger amounts per group of Organisms at each subse quent trophic level). The greatest amounts of PCBs are present in the long-lived predatory fish (e.g., trout, sharks) and birds (e.g., ea gles, hawks). Sufficient quantities of PCBs may build up such that physiology or function is disrupted. At high levels, PCBs may de crease resistance to diseases, interfere with reproduction, and dis rupt defensive behavior. In the case of birds, increased mortality of embryos can result as a consequence of the thinning of eggshells. Therefore, it has been concluded that PCBs can cause major environmen tal disruptions, particularly within aquatic habitats. Responding to this problem, the United States Environmental Protection Agency (EPA) has attempted to curtail the release of PCBs into the environment by regulating their use and disposal. Many aspects must be considered and weighed before the hazards to humans associated with exposure to PCBs can be estimated. The human hazard evaluation and subsequent risk estimation for any chemical must address the data base utilizing thorough comparative toxicologic as sessments. This means that the animal and human data available must undergo a careful consideration of 1) the breadth and variety of the toxic responses manifested; 2) the degree of species variation or spe cies consistency In the effects monitored; 3) the possible and/or pro posed mechanisms of toxicity; 4) the validity of the tests performed and their relevance for extrapolations to man; 5) the dosage used in 4-4 HONS 015920 animat tests versus the expected human exposures; and, finally, to the extent that the data are available, 6) the outcomes of serious poison ings and long-term occupational exposures. Only when a consistent pattern of toxicity In animals is consistent with the human experi ences can safe guidelines be promulgated. When assessing the hazards associated with human PC3 exposure based upon the mamnallan test data, we must consider all of the animal data. While concern Is given to positive findings, our decisions must also address the negative data and those doses required to Induce the toxlcltles seen In animals versus our expected human exposures. A review of the PCB literature reveals that PCBs are not very toxic If the exposure Is of short duration. The organ dysfunctions caused by longer but nonchronic exposures also occur only at rela tively high doses. This suggests that while organ dysfunction such as liver Injury or ehloracne might occur In man. It should occur only after high or sustained exposures. This suggestion has. In fact,, been supported by the available human data. Therefore, there Is little risk that these effects will occur In persons exposed to the generally low levels of PCBs In today's environment. If exposure occurs at all. Similarly, the animal data Indicate that there Is little repro ductive risk and that PCBs do not cause birth defects even at moder ately high exposures. Again the animal data reflect the findings In humans. The fusho Incident, a high PC8 exposure combined with expo sure to other toxic chemicals, failed to demonstrate a substantive concern for teratogenic effects. Considering the balance of the re production studies and the breadth of the mutagenic tests performed. It has been concluded that PCBs do not pose a significant mutagenic or reproductive hazard. While positive carcinogenic activity has been reported In one study using rats, this study must be placed In perspective against a far greater number of studies Involving rats and mice that were nega tive. When a positive test result Is our only available data, then that result should be considered as an obvious basis of concern for human exposure. However, a lack of comparable results in subsequent or other similar studies surely decreases the concern for and the val idity of focusing on only the positive data. Such Is the situation for PCBs. It would seem more reasonable to place greater emphasis on 4-5 HONS 015921 the large amount of negative data gathered, a suggestion that is be coming Increasingly substantiated by human exposures. In the last few years, the reported epidemiologic evidence has not Identified PCB ex posure as the cause of any form of human cancer. Therefore, even though there are animal data to demonstrate that PCBs are toxic at high doses, some toxicity at high doses Is expected for any chemical. Additionally, while there Is some evidence suggest ing that the carcinogenic potential of PCBs be considered, the balance of the animal data also suggests that It Is unlikely that this single response should become the focus of disproportionate concern usually given to potent carcinogens with definite initiator or genotoxlc prop erties. On the contrary, one might propose that there exist enough animal data to suggest that this finding could be pertinent only to those specific test conditions and the particular mixture of PCBs tested. In suneary, when all of the animal data are considered, they suggest that low levels of PC8s do not pose a significant health risk. At this point in assessing the hazard associated with exposure to PC8s, a more thorough discussion of the carcinogenic potential of PCBs Is needed because the risk of cancer from PCB exposure Is the most serious concern of the PC8-1nduced adverse effects. This concern Is surely of the utmost Importance to the general public. This has been reflected by the stance taken by the EPA, which is manifested by EPA's recent (1980) publication summarizing Its concern for PCBs. This am bient water quality criteria document Indicates (and we paraphrase) that If PCBs are not carcinogenic, then an allowable dally Intake of 210 jug of PCBs per day would be an estimated safe continual exposure. If, however, PCBs are carcinogens, while there may be no safe level, a level of risk approaching a lifetime risk for cancer of only one ex cess cancer In 100,000 persons exposed would be approximately 2 to 80 nanograms per day (ng/day). By comparison then, the distinction of whether or not PCBs have carcinogenic potential translates Into a 2,500- to 100,000-fold difference for what Is calculated as an allow able or safe level. Thus, the distinction between whether or not a chemical has carcinogenic potential has a profound Impact on how the chemical Is perceived by the public as well as how It might be regu lated. While we agree with the concern for and the distinction of chemi cals which are carcinogens, it Is the conclusion of this review that 4-6 HONS 015922 there presently exist sufficient PCS test date to reevaluate those concerns for PC8s Initiated by reported findings years ago. Further, the data now allow us to make the Important distinction of whether or not PCBs are Indeed Initiating carcinogens. Current theories of chemically-induced tumorogenesls differenti ate tumorogens by mechanism. One class Is the Initiating carcinogens that alter SNA and produce permanent. Inheritable, expressible changes In the Initiated cell. These Initiated cells may ultimately be trans formed Into the disease process we call cancer. The second class Is the promoting agents, which do not directly alter DNA, do not produce Inheritable changes, and are not effective with single or limited ex posures. Chemicals producing tumors by a promoting mechanism have demonstrable threshold levels below which chemical exposure will not result In the expression of tumors. The risk caused by these chemi cals therefore Is Insignificant In some for exposures that art below the threshold. A review of animal testing data documents the case that PCBs, at worst, have some of the characteristics of a promoting agent and do not exhibit characteristics of an Initiating carcinogen. A review of chronic cancer bioassay data further reveals that PCBs produced only a single species-, sex-, and mixture-specific positive response. The large number of negative tests Indicate that they do not possess broad, potent, promoting activity. At the hepatotoxlc doses tested, one reported PCB-Induced Increase In rodent liver tumor Incidence af ter the many studies conducted should not be a totally unexpected finding. The animal testing data and biological characteristics of PCBs overwhelmingly Indicate that If they produce an Increase In tu mors they do so by a promoting mechanism. Therefore, It can further be concluded that there are Indeed safe levels of PCB exposure and that not all exposures carry a risk of producing cancer. The occupational exposures are certainly the most extensive and longest-term human PCB exposures that we are currently aware of and are most representative of tdiat adverse effects might be expected. A comparative review of these occupational-exposure studies reveals that, like other chemicals, PCBs can cause adverse health effects, but in many respects these have been minimal. While dermatitis and chloracne, which were reversible after discontinuing the exposure, have HONS 015923 4-7 been noted In many cases, no other significant findings were routinely found. Even though several studies Incorporated clinical chemistry analysis as Indications of organ dysfunction or other physical disor ders, no remarkable clinical findings have been uncovered. Further more, several Investigators have commented to the effect that there Is a "paucity of abnormal results" and that "there Is no evidence of physical harm resulting from working with PCBs." In spite of over SO years of use, no causal relationship has been established for any spe cific type of cancer nor has the Incidence of cancer mortality been proven to be Increased. The largest study, by the National Institute for Occupational Safety and Health (NIOSH), which Involved over 2,500 persons did not detect any statistically significant excess In the cancer mortality. Since this study failed to demonstrate any statis tically significant excess In cancer In a high exposure population. It provides some reassurance that It Is unlikely that future studies will find any cancer risk from PC8 exposure. There are four epidemiologic studies addressing the card noge net 1c potential of PCBs. However, the first two studies are being reconsidered and will not be addressed here. The two most recent studies have larger populations with better defined exposure records and therefore more accurately reflect PCS effects. A recently re ported NtOSH study by Brown and Jones examined 2,567 workers from two capacitor plants with about half of the cohort having exposure periods of at least 20 years. There was a higher than expected incidence of rectal cancer among the workers, but the higher than normal rectal cancer rates In the geographical area In which the workers lived were not taken Into consideration in the experimental design. There was also a statistically Insignificant Increase In liver cancer deaths. The death rates from all cancers was less than expected (39 as opposed to 43), as was the mortality from all causes. The last study by Bertazzl and coworkers, also Just reported this year, examined 1,310 em ployees with at least six months' employment In a capacitor plant. An excess Incidence of digestive cancer was observed, but there were no liver cancer deaths. Again, the total number of deaths was small. The study Is continuing and these results may be considered prelimi nary. 4-8 HONS 015924 It must be remembered that in any epidemiologic study It may be Impossible to eliminate all of the unrelated but confounding variables In the observed populations. Additionally, It Is not uncommon to see measurable Increases In one type of cancer over what is mathematically expected because we cannot choose a subpopulatlon to observe that re flects exactly the baseline cancer rates of the total population. In fact, It is well known that different areas of the United States have different backgrounds for many of the specific types of cancer. All this must be considered carefully, and no conclusions should be at tributed to any finding of excess cancer which Is not statistically significant but above expected values, unless this same excess for that specific type of cancer Is repeatedly demonstrated In subsequent studies. A positive correlation between exposure to a chemical and a re sultant adverse health effect relies on the following conditions: (I) a positive association must be seen In Individuals with known expo sures; (2) the positive association cannot be explained by bias in recording, detection, or experimental design; (3) the positive associ ation must be statistically significant; (4) the positive association should show both dose and exposure period dependency; and (S) the pos itive association must be observed repeatedly in subsequent studies and cannot be a single, confounding, variable observation. To date, the mortality studies concerned with PC8 exposures present several problems of Interpretation, the most obvious and important of which is the different Increases In cancer type reported. Taken as a whole, they provide no support for assertions that PCBs are a cancer-causing chemical. The variety of tumor sites found to be of most concern within each study largely differs from the animal data and Is Incon sistent with the selectivity of currently known promoting agents. In summary, epidemiologic studies have demonstrated that commer cial PCBs are not remarkably toxic chemicals after acute exposure and that when excess exposure does occur, the usual consequences are der matologic and not of a serious or permanent nature. Chronic exposures have added little or no additional adverse effects of note to this picture. The preponderance of studies has not identified a clinical disease associated with exposure to PCBs nor has It provided persua sive evidence of health impairment. There Is no evidence of an excess 4-9 HONS 015925 In total mortality or In mortality due to cancer, cardiovascular dis ease, or nervous system disease associated with occupational exposure to PCBs. PCBs have not been linked to any human cancer, and studies to date Indicate It Is unlikely that future studies will establish such a link. The NIOSH epidemiology study demonstrated the absence of any can cer excess among those exposed to far higher levels than the general population has received. The liver cancer rate In the United States Is one of the lowest In the world and Is not Increasing over time. If one were observing a significant effect from PCBs, one would expect to detect a gross rate change, yet such Is not the case. Even when one makes all the conservative assumptions utilized In the official PCS cancer risk estimations, one arrives at answers which are so low as to escape our capability of detecting a positive effect via epidemiology. One must conclude that mathematical risk estima tion, even for the occupationally exposed, yields estimates which are vanishingly small. The data provided by recent studies do not support the current assumptions by EPA. The EPA, In the Federal Register No tice of Availability of Draft Ambient Water Quality Criteria, esti mates that the following risk to cancer from PCBs as: 10'^ cancer risk 80 ng PCB/day. When this estimate Is compared to the NIOSH and the FDA studies, one finds a large disparity between those results that would be predicted by this value and those that were actually measured. The following table summarizes estimated exposures and the risk calculated based upon the EPA calculated risk at lower doses, as pro posed In EPA's ambient water quality criteria document (45 FR 79320). 4-10 HONS 015926 Group Blood Levels of PCBs Estimated Exposure EPA Calculated Risks Highly Exposed Capacitor H.OOO ppb Workers Average Capacitor Worker 500 ppb Michigan Ftsh-Eater 70 ppb Michigan Control Population 20 ppb General Population 2 ppb 2.0 mg PCB/day .84 mg PCB/day .12 mg PC8/day .035 mg PCB/day .0035 mg PCB/day 25.0 10.0 1.4 .5 OS The chances of dying from liver cancer can be expressed in sev eral ways. But simply speaking, there will be about 2,000,000 deaths in 1981. Of these, it Is estimated that 9,400 will be from liver can cer. Therefore, 9,400/2,000,000 equals a .47* chance that those dying this year will be dying from liver cancer. Rounding off these esti mates to a .51 chance for the purposes of our discussion, and using these comparisons, thus leads to the conclusion that for the general population, about 10* of the liver cancer in the United States would be due to PCB exposures; that the Michigan control population would expect a 100* Increase In liver cancer Incidence, that the Michigan fish-eaters would have a three-fold Increase, and that the average capacitor worker would have a 20-fold Increase, while the highly ex posed worker would have a 25* Incidence or a 50-fold Increase. There Is no human evidence to support any of this. The EPA's proposed water criteria standard Is from 10 to 100 times higher than can be justified on the basis of recently published human experience, and from 10 to 20 times higher than can be concluded on the basis of the negative find ings from the human experience. It Is our conclusion that commercial PCBs do not represent a sig nificant health hazard. However, the presence and extent of contami nants (e.g., PCOFs) may alter the health concerns. Therefore, It is essential to determine the level of contaminants present when dealing with PCB wastes before applying the conclusions of this report to waste mixtures. 4-11 HONS 015927