NCIt definition : The major metabolite of the potentially carcinogenic nitrosamine 4-methylnitrosamino-1,3-pyridyl-1-butanone
(nicotine-derived nitrosamine ketone; NNK) that is detected in the urine of subjects
exposed to tobacco products. 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (nicotine-derived
nitrosamine alcohol; NNAL) is produced by carbonyl reduction of NNK and may also be
a carcinogen.;