[Nitrogen dioxide in the environmental air as a precursor of endogenous synthesis of carcinogenic nitrosamines].

The experiment was conducted on white noninbred rats receiving different concentrations of the nitrosamine (NA) precursors NO2 and amidopyrinum. Carcinogenic NAs were determined in the organs of the animals that had inhaled them at concentrations of 0.4, 0.8, and 4.0 mg/m3. There was an increase in tumors in chronic experiments on exposure to NA in the same doses as compared with the controls. It was found that the ambient air NO2 level of 0.4 mg/m3 (MAC 10 mg/m3) should be considered to be hazardous due to the fact that there might be exogenous and endogenous syntheses and that the NA might exert a carcinogenic effect.