Document G5BMK6b1J3Mk6VYree2w4B1er

CANCEROGBNIC EFFECT OF VINYL CHLORIDE P. L. Viola (Regina Elena Institute for Cancer Research) Rome, Italy Presented at the Tenth International Cancer Congress Houston, Texas May 22-29, 1970 The demonstration of oncogenic activity of some chemical organic compounds employed for the preparation of "plastics" has been widely investigated and the limits and the effectiven ss of their oncogenic power have been well defined. The present investigation demonstrates that it is possible to obtain for some experimental models a marked carcinogenic r sponse to a monomeric precursor, i.e. vinyl chloride, of plastic polymers which follows a peculiar pattern for different tissues and organs of the rat. Twenty-six Mister (AR/IRE) male albino rats, of the average weight of 150 gr. were exposed to vapours of vinyl chloride 4 hours a day for 5 days a week during 12 months. The animals were kept in a plastic, air-tight container through which there was a constant flow of air containing 3% in weight equal to 30,000 p.p.m., of vinyl chloride. At the end of treatment the surviving animals were killed at twenty-day intervals, and the most important tissues and obgans were histologically examined by conventional methods. Twenty-five rats of the same strain were kept aside as a control. During the period of exposure the animals were slightly soporific, but the first few months of treatment were well tolerated and the rats showed no change in body growth or behavior and no organic alterations visible macroscopically or by radiological means. 65% of the animalB developed tumors of the skin and 26% of these showed tumors of the respiratory tract exclusively localised in the lungs. Very few animals d veloped tumors in the bone and in this case the tumors were localized in the metaphysical region of the femurs, and it is worthy to mention that the femurs of both posterior limbs showed the carcinogenic transformation. Tumors of the akin The skin transformation which developed more frequently in the para-aural r gion, has been the epidermoid carcinoma, but we have s en also papillomas and rarely mucoepidermoid carcinomas. s R&S158786 -2- Cancerooenic Effect of Vinyl Chloride P. L. Viola Tumors of the respiratory tract Even if as far as the percentage is concerned these occur in a smaller number, their morphologic appearance is mainly of an adenocarcinoma; only in one rat it has been observed a tumor of the epidermoid type. Sometimes the tumor showed an early developmental stage and consisted predominantly of cubic or columnar cells arranged as regular or irregular tubular and papillary elements supported by poorly developed fibrous stroma. Tumors of the bones In the metaphysical region of the four limbs a large proliferation of cartilaginous tissue arises outwardly to the periostium and seems to derive directly' out of the osseous cortical by the growth of its cells. The cartilagenous growth is dishotnogeneous as it is shown by the extension of finger-like prolongations into the boundary of neoformed tissue. Beside the chondroblastic, chondrocytic and angiomatous areas, manifestation of noticeable growth power, there are cartilaginous cones with regressive features, as fibrosis and hyalinosis. The results reported above indicated that vinyl chloride is an effective carcinogenic agent for the rat. As for many carcinogenesis studies, where multiple tumors arise at different sites, in different tissues and organs, the data obtained need to be evaluated considering a more prompt positive response according to the ideal concentration of the carcinogenic. It is noteworthy to emphasize that the cutaneous system represents an impressive pattern of susceptibility to the vinyl chloride. Another point to be considered is that all the cutaneous tumors developed in the same site, i.e., the region including the area in which submaxillary and parotid gland are located. Mo implications to hianan pathology can be extrapolated from the experimental model reported in this paper. R&S158787