[The dependence of the carcinogenic effect on the concentration of N-nitrosodimethylamine in (CBA x C57Bl/6)F1 mice and noninbred mice].

The relationship between the tumour frequency and nitrosodimethylamine (NDMA) concentration in drinking water was studied in the experiments involving 495 (CBA x C57Bl/6)F1 hybrid and 600 noninbred mice of both sex. At the NDMA concentrations of 0.04, 0.2, 1.0, 5.0 mg/l the tumour frequency was as follows: 21.6/26.2, 35.5/27.3, 57.4/56.4, 90.5/72.9% (20.0/20.0% in control) in hybrid mice; and 15.4/39.6, 18.2/43.5, 62.2/61.0, 76.5/87.5% (15.0/30.0% in control) in noninbred mice, respectively. In the given experiments the minimal effective NDMA concentration was 1.0 mg/l, and the maximal effective one--0.2 mg/l both for the hybrids and noninbred animals. The results of the research may be used for calculation of the MPC for NDMA.