Nitrosamines attract concern as contaminants in the human environment because of their carcinogenic properties. Although the levels are very low it is desirable to minimise occurrence as far as possible. Some consumer products contained low levels of nitrosamines, and attempts to further reduce the occurrence had only been partially successful. At the time the source of nitrosamine contamination was unknown, although there was evidence that the presence of formaldehyde was important.
I initiated a kinetic study of the formation of N-nitrosomorpholine from morpholine in the presence of sodium nitrite and formaldehyde over the range of pH 5-7. This study identified a previously unknown reaction pathway entailing a nucleophilic attack by nitrite ion on the iminium ion formed by the condensation of formaldehyde with morpholine.
Once the reaction pathways had been elucidated chemical entities were identified which interfered with process which resulted in an over 95% reduction in the occurrence of nitrosamines in consumer products.