N-Nitrosodiethylamine (NDEA) and N-nitrosodimethylamine (NDMA) were instilled intratracheally into male Syrian golden hamsters once a week for 15 wk. The total dosages were 1.5 mg and 7.5 mg of NDEA and 0.75 mg and 1.5 mg of NDMA. A control group simultaneously received phosphate buffer vehicle. Tumours related to instillation appeared principally in the respiratory tract and the liver. Over the entire lifespan of the animals tumour incidence rates in the respiratory tract were 100% in both the NDEA groups, 6% in both NDMA groups and 8% in the control group. The total incidences of liver tumours were 6% in the 0.75 mg NDMA group, 19% in the 1.5 mg NDMA group, zero in the NDEA groups, and 4% in the control group. These results indicate that, when administered by this route, NDEA is a much more potent carcinogen in the respiratory tract than is NDMA but NDMA alone seems to be carcinogenic to the liver, at a total dosage of 1.5 mg.
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