N-Nitrosodimethylamine is highly toxic, especially to the liver, and is a known carcinogen in lab animals. The EPA classifies NDMA as a probable human carcinogen. The US Environmental Protection Agency has determined that the maximal admissible concentration of NDMA in drinking water is 7 ng/L.[6] The EPA has not yet set a regulatory maximal contaminant level (MCL) for drinking water.