Nitrosamines are impurities that can show up in a wide array of cosmetics ingredients—including diethanolamine (DEA) and triethanolamine (TEA)—and products. The U.K.’s Department for Business, Enterprise and Regulatory Reform characterizes nitrosamines as toxic in more animal species than any other category of chemical carcinogen . While common in cosmetics, nitrosamines are not listed on product labels because they are impurities, but avoiding products with DEA and TEA is a start
Research has revealed that common household products such as shampoo can interact with disinfectants at U.S. wastewater treatment plants to form a little-studied class of cancer-causing substances. These substances, called nitrosamines, can end up in drinking water, experts say.