Surface Reactions of Organic Amines during Indoor Bleach Cleaning: Nitrosamine, Hydrazine, Chlorinated, and Dimer Product Formation

The widespread use of chlorine-based disinfectants drives the transformation of indoor contaminants and the formation of secondary pollutants. However, the occurrence, mechanisms, and products of surface heterogeneous reactions remain poorly understood. Here, based on flow tube experiments, we show that cleaning-emitted reactive chlorine gases (RCGs) (containing ∼350 ppb chloramine) react with surface-sorbed aromatic and aliphatic amines, generating diverse transformation products, including nitrosamines, hydrazines, chlorinated species, and dimers. As an example, dibenzylamine exhibited a heterogeneous reaction rate constant of approximately 7.9 × 10 –3 min –1 at 30% relative humidity (RH), corresponding to a half-life of ∼2.1 h, and with nitrosamine and hydrazine yields of 6.2% and 1.0%, respectively. Nontargeted analysis identified an extensive suite of additional products for different amines, generated through ring cleavage, hydroxylation, chlorination, oxidation, and dimerization. Product formation and reaction kinetics depend on RH, chloramine levels, and amine structures. We further confirmed the formation of these products during cleaning events in indoor environments. These transformation products exhibit greater environmental persistence than their parent amines, especially for chlorinated products, posing concerning exposure risks. Our findings demonstrate that heterogeneous reactions of surface-bound organic amines during cleaning form structurally diverse, persistent, and hazardous products─a process potentially applicable to a wide range of indoor contaminants.