PULMONARY CARCINOGENICITY OF 3,9-DINITROFLUORANTHENE AND 3,7-DINITROFLUORANTHENE, 3-NITROFLUORANTHENE AND BENZO[A]PYRENE IN F344 RATS

3,9- and 3,7-Dinitrofluoranthene (3,9- and 3,7-DNF), 3-nitrofluoranthene (3-NF) and benzo[a]pyrene (B[a]P) were tested for pulmonary carcinogenicity by intrapulmonary implantation of the compounds into rat lung. These chemicals were given in various doses as suspensions in beeswax-trycaprylin and the animals were observed for 100 weeks. The control group received no drugs. The incidences of lung tumors were 19/21 (90.5%), 7/10 (70%) and 1/10 (10%) in rats treated with 200, 100 and 50-mu-g of 3,9-DNF, 4/9 (44.4%), 3/10 (30%) and 0/10 (0%) in rats treated with 200, 100 and 50-mu-g of B[a]P, 12/22 (54.5%) in rats treated with 200-mu-g of 3,7-DNF and 1/20 (5%) in rats treated with 1000-mu-g of 3-NF respectively. No lung tumors were found in control rats. The incidence of lung tumors induced by 3,9-DNF was twice as high as that induced by B[a]P, when the equivalent dose levels of the two compounds were compared. Histologically, most of the tumors induced by 3,9- and 3,7-DNF and B[a]P were squamous cell carcinomas.