Isotope Labelled 1-Nitrosopyrrolidine (N545950), which is one of the N-nitroso compounds (NOCs) implicated in human colon carcinogenesis, but the toxicological mechanisms involved have not been elucidated. Drinking water contaminant candidate list 3 (CCL 3) compound as per United States Environmental Protection Agency (EPA), environmental, and food contaminants.