HEEP COPYRIGHT: BIOL ABS. In a model study of the metabolic activation of carcinogens, 2-bromo-2-nitropropane-1,3-diol (BNPD), an antibacterial and antifungal agent, was shown to nitrosate diethanolamine and triethanolamine. The reaction between diethanolamine and BNPD in aqueous solution was pH- and time-dependent, nitrosation being most effective when the initial pH was 12.0, as in an aqueous equimolar solution of BNPD and the amine. At this pH, the yield of the animal carcinogen N-nitrosodiethanolamine (NDELA) increased from 1% after 1 h to a maximum of 11% after 96 h. Yields of the nitrosamine declined significantly when the initial pH was lower. Decomposition products of BNPD in alkaline solution include nitrite, bromide, 2-bromo-2-nitroethanol, 2-nitroethanol, formaldehyde, 2-hydroxymethyl-2-nitropropane-1,3-diol and other compounds. A mechanism is proposed by which BNPD releases nitrite ion, the assumed nitrosating species. BNPD is this a nitrosating agent which is most effective in alkaline media.