Transformations of Methylamines and Formation of a Hazardous Product, Dimethylnitrosamine, in Samples of Treated Sewage and Lake Water

Abstract

AbstractAdded trimethylamine is converted to dimethylamine in samples of raw sewage and lake water, and the secondary amine thus formed or added dimethylamine disappears with time. The rates of formation and disappearance of dimethylamine are governed by the pH and the type and amount of inorganic N present. Ammonium is generated from both of the amines. Dimethylnitrosamine, a potent carcinogen, is formed in small amounts in samples of sewage and lake water receiving dimethylamine and nitrite, the maximum nitrosamine level detected rising with increasing acidity and increasing dimethylamine and nitrite concentrations. Dimethylnitrosamine also appears in sewage and lake water samples receiving trimethylamine. Microorganisms are involved in some stage of the conversion of the tertiary amine to the secondary amine and dimethylnitrosamine in sewage because these products are not found in sterilized sewage. The fungicide thiram (tetramethylthiuram disulfide) is converted to dimethylamine in sterilized sewage at pH 4.0, and small amounts of dimethylnitrosamine are also produced in the presence of nitrite; the yields of both products are far greater in nonsterile, thiram‐amended sewage. The identification of dimethylnitrosamine was verified by thin‐layer and gas chromatography, ultraviolet and infrared spectrometry, and combined gas chromatrophy‐mass spectrometry.