National occurrence of N-Nitrosodimethylamine (NDMA): an investigation of 38 Australian drinking water supplies

To date, limited exposure data have been published on N-nitrosodimethylamine (NDMA) occurrence in Australian drinking water. Here, we present a comprehensive analysis of data from the largest survey of NDMA in Australian drinking water, with a total of 211 samples, from 38 drinking water treatment plants across five states and one territory. Samples were collected at the treatment plants after disinfection as well as in the distribution systems. Only nine water treatment plants reported NDMA above 5 ng/L. NDMA was detected in more than half of the samples collected (57 of 87) from these plants, but all detections were below the Australian Drinking Water Guideline (100 ng/L). In agreement with other studies, NDMA was more frequently detected in chloraminated waters than chlorinated waters. The dosing of certain coagulant aids, and addition of ammonia prior to chlorine during chloramination were key factors in the formation of NDMA. Overall the results show that the drivers for NDMA formation in Australia are similar to those found in other studies worldwide.