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N‐nitrosodimethylamine (NDMA) is a carcinogen known to be present in various foods and industrial products. The US Environmental Protection Agency has established a 10 –6 cancer risk level for NDMA of 0.7 ng/L. NDMA has been found in the effluents of various water and wastewater plants, but its formation mechanism is not yet understood. This study evaluated NDMA formation during various water and wastewater treatment processes including chlorination and chloramination, ozonation, and ion exchange. On the basis of the limited results obtained in this study, NDMA appears to be a by‐product of the chloramination of water and wastewater, with the level of NDMA formed directly related to the chloramine dose. In the waters tested, NDMA did not form on contact with free chlorine or ozone. Contact of one water with typical levels of amine‐based polymer did not form any measurable NDMA levels (<2 ng/L). Batch testing was conducted with four strong‐base anion exchange resins contacted with untreated groundwater and with buffered deionized water. Results showed that some resins might leach or form NDMA and the level of NDMA produced is a function of the chemical functional group on the surface of the resin.
Najm et al. (Thu,) studied this question.