Comparative study on the carcinogenicity of N-nitrosodiethylamine, N-nitrosodimethylamine, N-nitrosomorpholine, N-nitrosopyrrolidine and N-nitrosodi-n-propylamine to the lung of Syrian golden hamsters following intermittent instillations to the trachea.

N-Nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR), N-nitrosopyrrolidine (NPYR) and N-nitrosodi-n-propylamine (NDPA) were instilled into the lungs of male Syrian golden hamsters by intratracheal instillations once a week for 15 weeks. The total doses given were 1.5 mg of each drug. As a control, hamsters were treated with the vehicle, phosphate buffer solution. During the total lifespan, tumor incidence rates in the respiratory organs were 100% in the NDEA group, 6% in the NDMA group, 43% in the NMOR group, 0% in the NPYR group, 72% in the NDPA group and 4% in the control group. The incidence rates in the liver were 19% in the NDMA group and 4% in the NPYR group. No liver tumors developed in the other groups. The carcinogenic potencies of these N-nitroso compounds to the respiratory organs was provisionally estimated to be in the following order: NDEA greater than NDPA greater than NMOR greater than NDMA = NPYR, at the 1.5 mg dosage level. However, the difference in the rates of tumor incidence between the NDMA or NPYR group and the control group was not significant.