Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2009
Publication Date: 1/19/2010
Citation: Kemper, J., Walse, S.S., Mitch, W.A. 2010. Quarternary Amines as Nitrosamine Precursors: A Role for Consumer Products?. Environmental Science and Technology. 44(4):1224-1231. Interpretive Summary: Nitrosamines are potent mammalian carcinogens and are therefore of public interest. The role of agricultural practices in nitrosamine formation and human exposure pathways has not been clearly elucidated. Results indicate that quaternary amines, a class of nitrogen-containing compounds that are often used as biocides and food preservatives, can be converted into nitrosamines. The structure of quaternary amines was found to play an important role in determining the relative potential of quaternary amines to serve as nitrosamine precursors. For example, polymeric and benzylated quaternary amines were more potent precursors than monomeric quaternary alkylamines. Future studies will adapt this work from water-treatment scenarios to agricultural scenarios, such as farm runoff, commodity disinfection, and pre-plant fumigation. As such, this work surveys as an important springboard for future investigations that will attempt to minimize the role of agriculture in nitrosamine formation and exposure.
Technical Abstract: Nitrosamine formation is associated with wastewater-impacted water supplies, but the specific precursors within municipal wastewater effluents have not been identified. Quaternary amines are significant constituents of consumer products, including shampoos, detergents and fabric softeners. Experiments indicated that the low nitrosamine yields resulted from quaternary amines themselves, not just from lower order amine impurities often found in association with them. Polymeric and benzylated quaternary amines were more potent precursors than monomeric quaternary alkylamines. Pre-treatment of quaternary amines with ozone or free chlorine, previously demonstrated to deactivate secondary and tertiary amine precursors for nitrosamines, did not significantly reduce nitrosamine formation from quaternary amines. The nitrosamine formation pathway is unclear and the role of Hoffman elimination, which involves the transformation of quaternary amines to lower order amine precursors of nitrosamines, appears to be minimal. Rather, experiments suggest that the pathway may involve degradation of quaternary amines by amidogen or chloramino radicals formed from chloramines. Although quaternary amines may be readily removed by sedimentation during wastewater treatment, their importance should be evaluated on a case-by-case basis. The high loadings from consumer products may enable the portion not removed to serve as important precursors, as was previously found for quaternary-amine based coagulation polymers.