Nationwide assessment of nitrosamine occurrence and trends

Nitrosamine data reported from the first rounds of samples collected under the second Unregulated Contaminants Monitoring Rule (UCMR2) were reviewed to assess the frequency and magnitude of occurrence and the effect of disinfectant type and other treatment factors on reported nitrosarnine concentrations. N-nitrosodimethylamine (NDMA) was detected in drinking water at concentrations above the UCMR2 minimum reporting level of 2 ng/L in 1 of every 10 samples, primarily in systems using chloramines. Other nitrosamines (i.e., N-nitrosodiethylamine [NDEA], N-nitrosopyrrolidine [NPYR], N-nitroso-di-n-butylamine [NDBA], and N-nitrosodimethylethylamine [NMEA] were rarely detected. Follow-up survey results from 45 water systems generally followed expected trends based on the literature. NDMA occurrence was more frequent, and concentrations were higher in water systems having long contact times with chloramines and with no preoxidation step.