The quantitative relationship between dose and tumor morbidity were studied in 1,004 male C3H mice following subcutaneous injections of 3-methylcholanthrene, dibenz(a,h)anthracene, or benzo(a)pyrene. Biomathematical procedures were used to determine both the tumor morbidity and latent-period responses with regard to the injected dose and relative carcinogenic potencies of these carcinogenic hydrocarbons. The results were as follows: The minimal average latent period in months (days/30) was 3.72 for dibenz(a,h)anthracene, 2.48 for 3-methylcholanthrene, and 3.02 for benzo(a)pyrene. The median tumor dose (TD-50) was 0.016mg. for dibenz (a,h)anthracene, 0.021 mg. for 3-r 24 ·lylcholanthrene, and 0.101 for benzo(a)pyrene. The 95% tumor dose (TD-95) was 0.084 Dlg. for dibenz(a,h)anthracene, 0.096 mg. for 3-methylcholanthrene, and 08.75 mg. for benzo(a)pyrene. The specific induction time in months (days/30) was 6.79 for dibenz(a,h)anthracene, 5.14 for 3-methylcholanthrene, and 5.23 for benzo(a)pyrene. The difference between the relative potencies of 3-methylcholanthrene, and dibenz{a,h)anthracene is not statistically significant, but both of these hydrocarbons differed significantly from benzo(a)pyrene. A total of 433 tumors at the site of injection was observed in the 957 surviving mice. Histologically, the tumors were spindle cell sarcoma (411), carcinoma (2}, or mixed carcinoma and sarcoma (2). Eighteen tumors were excluded in the absence of histological examination.
