Document 93ao8dj6OQ85jXvza7501y2Zq

carcinogenicity of vi:;yl chloride and VINYLIDENE CHLORIDE C. C. Lee, J. C. Bhandari, J. M. Winston W. B. House, R. L. Dixon, and J. S. Woods /I // ~r< r :977 A Pharmacology and Toxicology Midwest Research Institute Kansas City, Missouri 64110 and Environmental Toxicology Branch National Institute of Environmental Health Sciences Research Triangle Park, North Carolina 27709 CARCINOGENICITY OF VC AIT) VDC Correspondence: Dr. Cheng-Chun Lee Midwest Research Institute 425 Voiker Boulevard Kansas City, Missouri 64110 3 CMA 010891 ACKNOLTEDCCMENTS This research was supported by Contract No. N01-ES-2-2084 from the National Institute of Environmental Health Sciences. Preliminary results were presented to the 1976 Fall meeting of the American Society for Pharmacology and Experimental Therapeutics, August 15-19, 1976, Tulane University, New Orleans, Louisiana, in the Pharmacologist, 18: No. 2, 245, Fall 1976; and to the First International Congress on Toxicology, March 30-April 2, 1977, Toronto, Canada, in the Abstract, 32, 1977. The authors are indebted to Dr. P, J. peters and Mr. J, K. Hagensen for their assistance on inhalation and chamber monitoring operations and to Mrs, E. R, Ellis for her super vision on histology preparation. 3 ADS'l'RACT Carcinogenicity of Vinyl Chloride and Vinylidene Chloride. Lee, C. C., Bhandari, J. C., Winston, J. M. , House, W. B.} Dixon, R. L., and Woods, J, S. (1977). Toxicol. Environ. Health 00:00-00. Exposure of mice to 50? 250 or 1,000 ppm of vinyl chloride (VC) in the air, 6 hrs/day and 5 days/vk, caused a high incidence of bronchiolo-alveolar adenoma, mammary gland tumors and hemangiosarcoma. Mammary gland tumors occurred only in the female and in cluded ductular adenocarcinoma, squamous and anaplastic carcinomas with meta stasis to the lung. Hemangiosarcoma occurred in the liver, and, to a lesser extent, in various other organs. The incidence and severity of these tumors increased with the VC level and the length of exposure. Malignant lymphoma involving various organs was observed in several mice. Rais were more re sistant to the carcinogenic effects of VC. Exposure of rats to 250 or 1,000 ppm of VC caused hemangiosarcoma in the liver. Many rats with hepatic hemangi- isarcoma also developed hemangiosarcoma in the lung, Extrahepatic hemangi osarcoma also occasionally occurred in other organs. Exposure to 55 ppm of vinylidene chloride (VDC) caused hepatic hemangio- -.rcoma and probably bron chiolo-alveolar adenoma in mice- Hemangiosarcoma; . 1 so occurred in the me senteric lymph node or subcutaneous tissue in two rats exposed to 55 ppm of VDC. = Key 'Words; Carcinogenicity Vinyl chloride Vinylidene chloride INTRODUCTION In 1971, the carcinogenic effect of vinyl chloride (VC) was first reported in animals (Viola, et al.). Male Ar/IRE rats exposed to 30,000 ppm of VC, 4 hrs/day, 5 days/wk for 12 months, developed epidermoid carcinomas, papillomas and mucoepidermoid carcinomas of the skin, adenocarcinomas of the lung, and osteochondromas of the metacarpal and metatarsal regions of the- . limbs. Hepatic angiosarcomas and other tumors were observed in rats exposed to 20,000, 500 or 50 ppm of VC (Caputo ec al., 1974; Winell et al., 1976). Tumors of the skin and lung were also reported in rabbits exposed to 10,000 ppm (Caputo et al., 1974). Exposure to VC as low as 50 ppm, with the same exposure times, induced angiosarcomas in the liver and other tissues of Sprague Dawley and Vis tar rats, Swiss mice and Golden hamsters (Maltoni and Lefemine, 1975). In addition, other tumors were seen including tumors of the cymbal glands and skin, nephroblastomas, hepatomas and neuroblastomas in rats; tumors of the lung and skin in mice; and tumors of the skin and lymphomas in hamsters These results were further confirmed, and in addition, dose-time ar.d carcino genic response relationships were established (Maltoni, 1977), In 1974, four cases of hepatic angiosarcoma were reported in poly vinyl chloride workers (Creech and Johnson). The first case of hepatic an.-tosarcoma occurred in 19 11 (Heath et al., . ')) . Further cue- of hepa tic angiosarcoma and other hepatic diseases, notably portal fibrosis and portal pertension, were identified among VC polymerization workers (Slock. 1974; g t ril,, 1974: Ice ind 'r,,rr" 1 ^ **4 * r* *- mT ^- tumors at multiple sites developed in VC and polyvinyl chloride workers (Monson and Peters, 1974; Tabershaw ar.d Gaffcy, 1974; Nicholson et al., 1975; Byron et al., 1976; Waxweiler et al., 1976). This report summarizes the car cinogenic effects of 50, 250 or 1,000 ppm of VC in rats and mice and com pares the effect of vinylidene chloride (VDC) at concentraion of 55 ppm. 3 3 010895 CMA MKTilOOS Inhalation Chambers and Air Snnnlv; Five stainless steel cubical type exposure chambers of 3.5 volume were used. VC or VDC was intro duced through the top of the chamber. Each chamber contained a plenum, a diffusion plate and two small squirrel cage fans (2.85 m-Vmin), mounted on opposite sides of the top cone above the diffusion plate, to ensure com-, plete mixture of the gas with air. The outside air supply passed through a coarse filter, over coils for heating, cooling and dehumidifying, and then through an absolute filter (99.97-99.95% retention of 0.3 u particles) irmo the plenum of the chamber. Air flow rates were measured initially at the inlet side of the chamber with a pitot tube connected to a magnahelix gauge and later at the exhaust outlet with a orifice plate and magnahelix gauge. The orifice plate was calibrated with an air flow transducer (Autotronics 10G-3XX). These measurements indicated air flew rates of about 12 chamber volumes (0.70 m-^/min) per hour. Generation of VC and VDC Vapor: VC gas (99.87, pure, Matheson Products) was metered with rotameters into the clumber air supply. VDC (997, pure, Aldrich Company) was heated to 37 C to ;nerate the vapor. All VDC lines and the rotameter were heated to 40'C to prevent condensation. Cham^r '-'on L tor In*.', and Sampling; g. ;;bcr concentrations were monitored using a gas chromatograph (Varian-2700) with a flame ionization detector. A 6 ft x 1/8 in, stainless steel column packed with 0.4% Carbovax 1500 on Carbopak A was used with a nitrogen carrier flow rate of SO ml/min. The injection, coLumn and detector temperacures were 135CC, 65 C, and 170 "C, respectively. VC standards at dilutions of 10, 50 and 100 ppm were obtained in lecture bottles (Supelco, Inc., Bellefonte, PA), and a 1,000 ppm primary standard was obtained from Matheson Gas Products (Joliet, IL). VDC standards were prepared by a serial dilution (weight/volume) of VDC in carbon tetra chloride. Each chamber was fitted with 10 sampling ports on two sides. Polyethylene tubes were positioned through the ports at the center and near the periphery of the chamber. Samples were withdrawn with a syringe and introduced into the gas chromatograph, A valid sample could be withdrawn by pumping the syringe three times on the short sampling lines and five times on the long Lines, All sampling was performed in triplicate. Dis tribution studies at ail parts of the chamber were compared with a reference point in the center. The results indicated that average chamber concentra tions were 3% of the desired concentration and the reference point averages were 98,47, to 100.47, of the chamber averages. During the study, chambers were routinely sampled from the reference point three to four times a dav. An automatic sampling system was used later during the experiment. A polyfluroethylene (TeflotO, DuPont) Line (1/4 i . diameter) connected each chamber to the automatic sampler. These 11 were purged Constantly, peri od.cally, a sample was directed to the gas chromatograph whore it was in ject .1 via a sampling valve with twin 1-m.l sampling loops. The readout was processed by a Varian CDS 111 electronic integrator. The integrator was programed to measure peak area and to calculate ppm by an external standards program. A chart recorder connected to the integrator was oc casionally used to visualize the chromatogram. Experimental Desizn: Albino CD-I mice and CDs rats (Charles River Breeding Lab) about 2 months old wore used. For each species, a total of 360 animals were divided into five groups, each consisting of 36 males and 36 females. Each group of both species was exposed to 50, 250 or I7OOO ppm of VC, 55 ppm of VDC, or uncontaminated air for 6hrs/dayand 5 days/wk. All animals were kept in the same stainless steel cages with wire bottoms both during exposure and when outside of the chambers. Mice were housed six to eight/cage and rats two/cage. During exposure, the position of cages was constantly rotated throughout the study. Pulverized or block laboratorv chow (Wayne Lab Blox) was provided except during exposure. Water was available ad libitum. A 12-hr light cycle was maintained. The temperature in the chamber and in the room averaged 24 1.3C. The relative humidity ranged from 25 to 607, at the start of the experiment and was later regulated at 50 107,. Four animals of each species, sex and exposure level were termi nated for various laboratory tests, and gross and histopathologic examina tions at the end of 1, 2, 3, 6 and 9 moot! .e surviving animals were tc'zinated it '.he end of 12 months. I iborator.- Eva 1 uatlons ; All animals were observed throeiuou: the study for adverse signs. Food consumption was recorded weekly and body 6 'eight biweekly at a uniform time of day. Various clinical laboratory tests and specific studies were performed as described elsewhere (Lee et al., 1977). When moribund or at terminations, all animals were euthanized for necropsv after the collection, of blood. Gross examination, especially for anv appear ance of abnormal growth or other lesions, was carefully performed on all tissues including the brain, pituitary, thyroids, respiratory tract, ali mentary canal, urogenital organs, thymus, heart, liver, pancreas, spleen, mesenteric lymph nodes, and other tissues with pathological lesions. Tumors with adjacent normal tissues and the other tissues without tumors were fixed, processed, sectioned, and stained for microscopic examination. All external and internal tumors were carefully examined and identified histologically. 5 7 CMA 01089? RTSH TS Chamber Conceneracions: For VC, Che average weekly concentration in the 1,000 ppm and 250 ppm chambers did not vary more than 5% from the desired concentrations except during the third week when the average con centrations were about 10% lower. The variations in the 50 ppm chamber were slightly greate-r during the second, 7th and 8th weeks. With a few exceptions, no sample varied more than 10% from the desired concentration. It was planned that the exposure concentration for VDC would be 50 ppm. However, the slightlv higher concentration of 55 ppm was obtained and maintained throughout the experi meet. MTC2 General Condition: A few mice exposed to various levels of VC started to exhibit toxic signs including rough hair coat, lethargy, anorexia and rapid weight loss during the 6th month. Some mice died or were terminated before their imminent death. Thereafter, die general health of the remaining mice exposed to VC deteriorated. Abdominal distention and/or external tumor masses, especially mammary tumors in the females, .ecurrcd. All male and female mice exposed to 1,000 ppm and all females exposed to 250 ppm died or were terminated during the 10th through L2tk -.onths . Of the mice exposed to 55 ppm of '."DC, two males were terminated during the 9th month and one female during the 10th month. Most mice that died or were terminated ahead of schedule and many mice that were terminated on schedule at various times developed one or more types of tumors. In the control group, two males 8 died during the 8th or 9th month. One death was due to injury from fighting, the other mouse was found dead with autolysis. No obvious mass was observed in any controls. Gross Lesions: Gross lesions were observed in several organs of some mice. In the lung, there were raised, tan to greyish white nodules of pinhead size to 0,5 cm or larger. In the liver, there were moderate mottling and small dark hemorrhagic spots varying in size from petechiae to 1 cm in diameter, or dark nodular masses filled with blood or ruptures in several animals. Spleens were slightly to markedly enlarged. Subcutane ous masses occurred at various locations, varying in size from 1 to 3 cm or larger, moderately firm and greyish-white to dark in appearance. Bronchiolo-alveolar Adenoma: Bronchiolo-alveolar adenomas were found during the second month in the mice exposed to 1,000 or 250 pom of VC and during the third month in the mice exposed to 50 ppm. The adenoma was characterized by focal areas of acinar or papillary growth, forming small solitary nodules which were well demarcated but'not encapsulated (Plate 1). The incidence (Table 1) and severity of the tumor were in di rect proportion to the level of VC and to the ie.- ih of exposure. In more severe tumors, there was an increase in number ar. . in size of nodules by expansion and coalescing to cause consolidation of the affected lobes. There was no sex difference. A. total of 12, 22 and 48 mice3exposed to 50, 250 or i.OOO ppm of VC, respectively, developed bronchiolo-alveolar adenoma. This tumor was found in only one male control during the 9th month. In the group exposed to 55 ppm of VDC, a few small nodules of bronchiolo-alveolar adenoma were found in one male during the 6:h month, two males during the 9th month, and three males during the 12th mo-'th. Heman-icsarcoma: Hemangiosarcomas were found in the livers of mice exposed to 1,000 or 250 ppm of VC starting the 6th month. The hemangiosarcoma was characterized by moderate to severe proliferation of endothelial cells lining the sinusoids, dilation of the sinusoids, focal hemorrhage forming small to large cavernous blood spaces, invasion of the hepatic parenchyma with neoplastic cells, and mild to severe necrosis (Plate 2) depending upon the VC level and length of exposure. The incidence of he patic hemangiosarcoma was also related to the VC levels and to the length of exposure (Table 2), A total of 3, 23 and 31 mice exposed to 50, 250 or 1,000 ppm, respectively, developed hemangiosarcoma in the liver. Hepatic hemangiosarcoma appeared to occur more in females than in males exposed to 250 or 1,000 ppm of VC. However, the differences between sexes were not statistically significant. Extrahepatic hemanigosarcoraas occasionally occured in mammary gland, heart, gastrointestinal tract, pancreas, kidney, epididymis and testis, mesenteric lymph nodes and skeletal muscle. The incidence of extra hepatic hemangiosarcoma was rv ' related to the VC level or to the length of exposure. Hemaniyosarcoma w.n not found in any con trol mice. In the mice exposed to 55 ppm of VDC, hemangiosarcomas occurred in the livers of two males and one ferule. Iherc were also hemangiomas in the mediastinum of one fenule exposed to 50 ppm of VC and in the connective tissue adjacent to the salivary gland of one male exposed to 1,000 ppm. CMA 010902 10 Mammary Tumors; Mammary "land tumor a were observed in females exposed to various levels of VC starting the 6th or 7th month. The tumors consisted of adenocarcinoma, squamous and anaplastic carcinomas (Plate 3). The adenocarcinoma was characterized by proliferation of ductular epithelium with a marked anaplastic and squamous cell metaplasia; the squamous carcinoma was characterized by marked proliferation of stratified squamous epiLhel iu::i, marked keratinizaticn, marked purulent inflammation and necrosis; and the anaplastic carcinoma was characterized by marked proliferation of undif ferentiated cells in large sheets, irregular cords, and packets. These tumors occurred in 9, 3 and 13 females exposed to 50, 250 or 1,000 ppm, respectively (Table 3), Most of these mice had a combination of the various tumors. Metastic clusters of squamous and/or anaplastic carcinomas were also found adjacent to the pleura and/or in the lung of most of these fe males (Plate 4). These primary and metastic mammary gland tumors were more severe in the mice exposed to higher levels of VC and in the mice that died or were terminated at later date. In the group exposed to 1,000 or 250 ppm, the females developed these tumors earlier. Mammary gland tumors were not found in any controL mice or mice exposed to 55 of VDC. Malignant Lvmnhoma: During Che 6th mo: . , a mnlignan" lymphoma characterized by marked disseminated or diffused infiltration of lympho- reticular cells in the epicardium and myocardium, perivascular and inter stitial areas of the lung, liver, spleen and kidney was found in one female mouse exposed to 50 ppm of VC. There 'was loss of splenic architecture (Plate 5). In addition, a malignant lymphoma characterized by a large mass 11 CHA 010903 of lvmpho-reticuljr cells and necrotic debris, infiltrating the cervical tis sue surrounding the trachea, blood vessels and esophagus found in one male exposed to 1,000 ppm. During the 9th montli, mal ignant lymphomas involving spleen, liver, lung, heart, subcutaneous tissue in the cervical area, ar.d/'cr mart-nary gland were found in two females exposed to 250 ppm and one male and three females exposed to 1,000 ppm. Malignant lymphoma was not found in any control mice or mice exposed to 55 ppm of VDC at any time. Heoatc.-a and Other Tumors; A total of three mice exposed to 55 ppm of VDC developed hepatomas. This tumor was found in one male when terminated during the 9tn month, in one male and one female during the 12th month. The hepatoma was characterized by a marked proliferation of hepatocytes with a loss of the lobular pattern, except in the male mouse terminated at the 12th month. This mouse had only a tiny focus of the neoplastic cells. Hepatoma was not found in any control mice or mice exposed to any levels of VC. There were a hepatic cell carcinoma, and a renal adenoma in one mouse each exposed to 50 or 1,000 ppm of VC, and skin keratoacanthemas in two mice exposed to 55 ppm of VDC. RATS General Conditions: A number of rats hue rough hair coat, lost muscular tone and weight, and were lethargic after 7 months. Eight males and 13 females exposed to 1,000 ppm of VC died or were terminated curing the 8 th through the 12 rh months. Four males and 10 f-.males expose', to 233 ppm. died or were terminated during the same period. Two females exposed to 12 ,, { i 50 ppm died. No deaths occurred in the control group. One female rat ex posed to 55 ppm of VDC was terminated during the 9th month. Hermaneiosarcoma: All the rats that died or were terminated ahead of schedule and a number of the rats that were terminated on schedule during the 9th through 12th months developed hemangiosarcomas. During the 9th month, hemangiosarcomas were found in the livers of two rats exposed to 250 ppm of VC and of four rats exposed to 1,000 ppm. By the end of the 12th uionth, hepatic hemanigosarcomas were found in the livers of 12 and 21 rats exposed to 250 or 1,000 ppm, respectively. Three of these rats exposed to 250 ppm and thirteen of these rats exposed to 1,000 ppm also had hemangiosarcomas in the lung (Plate 6), As shown in Table 4, hemangiosarcomas in the liver oc curred more in the females than in the males at 1,000 ppm, Hemangiosarcomas also occurred in two rats (subcutaneous) exposed to 50 ppm of VC; two ruts (omentum or mesentery) exposed to 250 ppm; one rat (omentum) exposed to 1,000 ppm; and two rats (mesenteric lymph node or subcutaneous) exposed to 55 ppm of VDC. Hemangiosarcomas were not found in the liver, lungs or ar.v other organs of any control rats. There were also hemangiomas in the ad renal. glands of two rats exposed to 1,000 ppm ot "r. Other Tumors: A few other tumors occu ' '.ally occurred in one or several rats. The tumors included; a small nodule of bronchiolo-alveolar adenoma; reticulo-endothelial cell carcinoma or hepatoma in the liver; ductular adenocarcinoma or fibroadenoma in the mammary gland of the female; malignant lymphoma in the spleen or other organs; adenoma in the kidney; 13 i'*' X/ <L squamous carcinoma, kcratoacantkoma or fibroma in the skin; adero carcinoma in the sebaceous gland; and chromophobe cell adenoma in the pituicar /. Ihese occasior.al tumors were not related to VC or VDC. 14 CH6 010906 Dir.cr^TP*: Air? tvy.'ChtoTOvo Exposure to 50, 250 or 1,030 ppm of VC, 6 hrs/ day and 5 days/wk, was highly carcinogenic in mice. Bronchiolo-alveolar adenomas, mammary gland tumors, and hematigiosarcomas developed in these mice. The incidence and severity of these tumors were related to the level of VC and to the length of exposure. A few mice exposed to VC also developed malignant lymph omas. The total incidence of various tumors would probably be considerably higher, if some of the mice had not been terminated at early intervals. Bronchiolo-alveolar adenomas were observed starting the second month. Bronchiolo-alveolar adenoma, bronchiolar adenoma, or pulmonary adenomatosis, has been reported to occur spontaneously in aging mice, mostly over 1 year of age (Amaral-Mendes, 1969; Baillif and Jones, 1973; Dearberg et al., 1974). However, in the present study, large numbers of mice ex posed to various levels of VC developed this tumor. In addition, die tumors were observed at a very early age; the incidence and severity were related to the VC level and the length of exposure. On the other hand, only a few small nodules of this tumor occurred at later times in one control and several mice treated with 55 ppm of VDC. Its significance i.. 'C mice is questionable. Hemanigosarcomas, primarily in the liv were observed starting the 6th month especially the mice exposed to 250 or 1,000 ppm of VC. Hepa tic hcraangiosarcomas also occurred in three mice exposed to 55 ppm of VDC. The severity of these tumors and the mammary gland tumors in females ex posed to VC probably contributed to the deaths of most of the mice. CMA 010907 Mammary gland tumors were observed only in female mice starting the 6th mouth and consisted of ductular adenocarcinoma, squamous and anaplastic carcinomas. The mammary gland tumor was the most complex. Observations on several stages and sizes of this tumor suggested that the tumor originated as ductular adenocarcinoma and then in a very early stage underwent an ana plastic ar.d squamous cell metaplasia. The tumor at this s tage appeared quite malignant and invasive. In many cases, there were metastases of the anaplastic and squamous carcinomas in the lung. In addition, the ductular or alveolar involvement seemed to be only minimal except in the early states of some small tumors. This type of pattern is very different from the spon taneously occurring mammary gland tumors in mice. The incidence and severity of the mammary gland tumors aprearod to be greater in mice exposed to higher levels of VC and in those mice ex posed for the longest periods of time. This may explain the higher incidence of mammary tumors in the group exposed to 50 ppm as compared to the group ex posed to 250 ppm. All females exposed to 250 ppm died by the end of the 9th month, while many females exposed to 50 ppm sur, :v 1 beyond this time. This increased exposure time in the latter group may th account for the greater number of tumors, Tl'.e significance of hepatomas in three mice as related to the ex posure of iOC was considered questionable. These tumors have been reported to occ.,.r spontaneously in small numbers at this age (Andervont, 1950; Percy 16 CfiA 010908 and Jor.as, 1971; Shen, 1974), even (.hough Lhev did not occur In anv of the control animals. The other occasional tenors observed in mice cere not re lated to exposure of VC or VDC. Rats were more resistant to the carcinogenic effects of VC or VDC, Hepatic henangiosarcomas were observed in rats exposed to 250 or 1,000 pm of VC starting the 9th month. In contrast to the mice, many of the rats with hepatic henangiosarcomas also developed hemangiosarcomas in the lurrg. VC did not cause any other tumors in the rat. Two rats exposed to 55 ppm of VDC developed hemangiosarcomas in the mesenteric lymph node or subcutane ous tissue; these tumors were probably caused by VDC, The rats were also found to be more resistant to the acuta or other chronic effects of VC or VDC than mice as reported elsewhere (Lee et al., 1977), 17 CMrt 010909 Exposure Time fMon t lis) 1-3 4-6 7-9 10-12 TABLE 1 INCIDENCE OF BR0MC1ITOLO-ALVEOLAR ADENOMA TN MALE fM) AND FEMALE (F) MICE REPOSED TO VC OR VOC 0 M F 0/12 0/12 0/4 1/6 0/4 0/4 0/4 0/16 VC < ppml 50 250 11 F 1 F 1/12 0/12 2/12 0/12 2/5 0/5 1/4 4/7 2/7 4/14 5/11 8/15 3/5 0/3 2/2 0/0 1. 000 L1 F 3/12 3/12 6/6 4/5 1.3/15 19/19 0/0 0/0 To i a l 1/26 0/36 8/29 4/34 10/29 12/34 22/33 26/36 EiU r i es indica te Co. of incidence/! lo. of mice examined. VDC (ppm) 55 MF 0/12 0/12 1/4 0/4 2/6 0/4 3/13 0/15 6/35 0/35 t CMA 0 1 0 9 1 0 Exposure Time ("on rhs1 6 7-9 10-12 TABLE 2 I^rnrercc.or hfhanctosarcoha tm mm.e cm) amp l'T.MM.F, (F) MT CK EXPOSF1) TO VC OB VI)C 0 1J --VC_tPpm) ________________________________________________________ 50 250 1. 000 FMF MFMF In Liver 0/16 0/6 0/4 0/16 0/4 0/16 0/17 1/7 2/5 0/17 0/14 0/3 0/16 5/11 2/ 2 2/19 14/15 0/0 2/18 11/15 0/0 3/17 15/19 0/0 VDC (ppm) 55 MF 0/16 1/6 1/13 0/16 0/4 1/15 Total 6 7-9 10-12 0/26 0/16 0/6 0/4 0/36 0/16 0/4 o /16 3/29 0/17 1/7 4/5 0/34 7-^29 16^/34 13^33 In Other Organs 0/17 0/14 1/3 0/16 1/11 1/2 0/19 3/15 0/0 0/18 0/15 0/0 18/36 2/17 7/19 0/0 2/35 0/16 0/6 0/13 1/35 0/16 0/4 0/15 Total 0/26 0/36 5^29 1/34 2/29 3/34 0/33 9SjJl/36 0/35 0/35 Entries indicate ho. of incidence/ iJo. of mice examined. a/ Significantly different from incidence in control group by Fisher exact probability tesL (Siegel 1956), p <0.05. --/ significantly diiferent from incidence in opposite sex exposed to same concentration by Fisher exact probability test (Siegel, 1956), p <0.05. TT60TO VWO t TABLE 3 incidence OF MAMMARY Cl AND TUMORS AND METASTASIS IN Till'. i.u;k: I'll FI MATE MI OF. EXPOSED TO VC Exposure Time VC Concentration (ppm) (Months) 0 50 250 Mammary eland Tumors 6 7-9 10-12 0/16 0/9 0/16 0/17 7/14 2/3 1/19 2/15 0/0 1,000 3/17 10/19 0/0 Total 6 7-9 1o - 1 7 0/36 0/16 0/4 0/16 9/34 3/34 13/36 Me tas tasis in the fame 0/17 2/14 0/3 1/19 1/15 0/0 3/17 5/19 0/0 To tal 0/36 2/34 2/34 8/36 Entries indicate No, of incidcnce/No- of mice examined. CMA 0 1 0 9 1 2 Sex Male Female Male Female Male TABLE 4 NUMBER OF MM,r AND FEHU.E BATS EXPOSED TO VC OR VDC WHICH DEVELOPED iiKHAHCTOSADCOM\ Vt t Will ) 0 50 250 1,000 VDC (ppm) 55 In the Liver 0/35 0/35 0/36 0/36 2/36 1C&//34 6/34 15ib//36 0/36 0/35 In the Limes 0/35 0/35 0/36 0/36 0/36 3/34 4/34 95//36 0/36 0/35 In Other Orp,a ns 0/35 0/35 1/36 1/36 2/36 0/34 0/34 1/36 2/36 0/35 Entries indicated Co. of incidcnce/Ko. of rats examined. <\j Significantly different from incidence in control yroup by Fisher exact probability Lest (Siegel, 1956), p <0.05. b/ Significantly different froi:i incidence in opposite sex exposed to same concen tra t i on by Fisher exacL probability test (JSleel, (1956), p <0.05. 010913 I. nr '-'T s Plata 1 2 3 4 5 6 Title Bronchiolo-alveolar adenoma in nice ex-posed to VC. Top: Showing two snail nodules, one with a focus of metastatic squamous cell carcinoma (A) from the mammary gland. HaE x 25. Bottom: Higher magnification, showing Papillary Prolifera tion. H&E x 160. Hepatic henangiosarcoma in mice exposed to VC, showing endothelial prolif eratior. (A), invasion of hepatocvces (B) and hemorrhage (C) . HLE x 100. Mammary gland tumors in mice exposed co VC. Top: Ductular adenocarcinoma (A) and anaplastic carcinoma (B). H4E x 250. Bottom: Squamous cell carcinoma. HLE x 100. Metastatic mammary gland carcinoma in the lung of mice exposed to VDC. Top: Anaplastic ca cinema, mitotic figures (A). HaZ x 250. Bottom: Squamous cell carcinoma, karat inirxition (A), r.tr.iti- fied squamous epithelium (3). KaE x 250. Malignant lymphoma in the spleen of mice exposed proliferation of lymphocytes and loss of splenic H3E x 160. VC, show: Hemangiosarcom.a in rats e>posed to VC. Top: Liver, shewing endothelial proliferation (A), s ien of hepatocynes (3) and hemorrhage (C) . H:,E x ICO. Bottom: Lung, showing endothelial pr ' 1:feration (A), i nvasion of alveoli (3) and hemorrhage ,C). ULE x 160. CMA 010914 22 REFERENCES Amaral-Mendes, J. J. (1969). 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