The production of tumors in rats by the implantation of pure polyethylene.

in rats by pure polyethylene implanted in the ab dominal wall, and, in addition, the production of tumors by the implantation of polyethylene over the skull is described. Oppenheimer et al. (1†" 3) have reported the pro duction of malignant tumors in rats by the implan tation of various plastics in the abdominal wall. The frequency of tumor production varied from 4 per cent to 45 per cent, depending upon the plas tic used. Among these plastics were two types of polyethylene : one of a commercial grade and one considered to be pure. They found that the pure polyethylene without a plasticizer induced tumors in 18 per cent of the rats. These tumors were chief ly fibrosarcomas and could be transferred through several generations in rats. Since polyethylene is used for many surgical procedures and is often left in the tissues, con.fir mation of these observations is important even though the relationship between the production of tumors in rodents and the production of tumors in man is not known. Pure polyethylene film' of the kind used in cmi cal procedures was employed as the test substance. This was washed with detergent, rinsed with water, heat-sealed in polyethylene sacs (same material), and sterilized with high voltage cathode rays. Two strains of rats were used, namely, Wistar and Hisaw (originally from Wistar stock). There were equal numbers of each sex. Fifty rats of each strain had polyethylene aseptically implanted sub cutaneously in the abdominal wall and subgaleally over cranial defects. The pieces of polyethylene were square, about 1.5†" 2. cm. oii each side. Fifty additional rats (Hisaw) were used as a control group. These animals were subjected to an identi cal surgical procedure, but no polyethylene was imbedded. All these rats were then allowed to live until they developed tumors or died. All were kept in the same room and fed the same diet.. RESULTS Of the original 150 rats, 59 were lost in their cages by cannibalism, and another six died soon after implantation of the plastic and would not be expected to have developed a tumor. Thus, there were 85 rats that survived long enough to develop tumors and were observed until they died or were sacrificed; 2.8 of these were controls, and 63 had polyethylene implants. The survival times of the 2.8 control rats were: 8†" 12.months, 2.2.; 12.†" iS months, 14; 18†" …