The
tumor-initiating activities of
benzo[a]fluoranthene (BaF),
benzo[b]fluoranthene (BbF), naphtho[1,2-b]
fluoranthene (NbF) and naphtho[2,1-a]
fluoranthene (NaF) were evaluated on the skin of female CD-1 mice. Each of these
polycyclic aromatic hydrocarbons was assayed at total initiation doses of 1.0 and 4.0 mumol/mouse. These
hydrocarbons were applied in 10 subdoses administered every other day. Promotion commenced 10 days after the last initiator dose and consisted of thrice weekly application of 2.5 micrograms of
tetradecanoylphorbol acetate for 20 weeks. BbF was the most potent
tumor initiator inducing a 100% incidence of
tumor-bearing mice with an average of 8.5
tumors per mouse at a total initiator dose of 1.0 mumol. NaF was slightly more active as a
tumor initiator than either NbF or BaF. NaF induced a 90% incidence of
tumor-bearing mice with an average of 5.9
tumors per mouse at a total initiator dose of 1.0 mumol. BaF and NbF at a total initiator dose of 4.0 mumol exhibited similar
tumor-initiating activity with both inducing a 90% incidence of
tumor-bearing mice with an average of 4.3 and 6.6
tumors per mouse, respectively. However, at a total initiator dose of 1.0 mumol, BaF and NbF induced a 95% and 65% incidence of
tumor-bearing mice with an average of 3.3 and 2.5
tumors per mouse, respectively.