Nitrosamines

Nitrosamines, a family of emerging contaminants with strong carcinogenicity, have been widely detected in water, wastewater, air, soil, food, beverage, tobacco, pharmaceuticals, and industrial reagents. Their occurrence as disinfection by-products (DBPs) has been widely reported in drinking water treatment plants in the U.S. and Canada since the late twentieth century, and later in Europe, Asia, Oceania, and South America. N-nitrosodimethylamine (NDMA) is the most frequently detected nitrosamine species in water. Chloramination, intended or de facto, is the key factor for nitrosamine occurrence during drinking water treatment, however, properties of their precursors, the presence of other disinfectants, and contact time are also strong factors associated with their occurrence. The unsymmetric dimethylhydrazine (UDMH) pathway is often considered to be the main mechanism for the formation of NDMA. Nitrosamine precursors are quite complex and from diverse sources, including basic amines, certain pesticides, pharmaceuticals, natural organic matter, industrial wastewater, and domestic wastewater, including the effluent from wastewater treatment plants. Amino acid metabolism has also been found to be a source of nitrosamine precursors. Nitrosamine control strategies include source control, process control, and end-of-pipe removal. Conventional processes, e.g., coagulation, sedimentation, and filtration, remove few nitrosamine precursors while advanced treatment processes, e.g., ozonation and (biological) activated carbon processes, can reduce nitrosamine precursor concentrations effectively. Modifications to disinfection processes can also help to minimize the formation of nitrosamines. High doses of UV irradiation are also able to degrade NDMA, and while this is not often used to minimize NDMA as a disinfection by-product it may be a method to remove NDMA from contaminated water. Due to its wide occurrence and health impacts, NDMA has been regulated in some countries including the United States, Canada, the Netherlands, Australia, South Korea, and China.