Research progress on pollution levels, sources, and health risks of <italic>N</italic>-nitrosamines in the atmosphere

N-nitrosamines are a class of highly carcinogenic organic nitrogen compounds containing nitroso groups characterized by water solubility and volatility. Although N-nitrosamine pollution in drinking water systems has received significant attention, atmospheric research is limited. N-nitrosamines are prevalent in indoor air and the environmental atmosphere, with high concentrations in industrial and urban areas potentially reaching levels that pose significant long-term cancer risks. Furthermore, this risk may be underestimated due to limited assessment scenarios, insufficient toxicological data, and incomplete monitoring media. Primary sources of atmospheric N-nitrosamines include industrial emissions from rubber factories and landfills, as well as lifestyle emissions such as smoking, cooking, and vehicle exhaust. Furthermore, N-nitrosamines can be secondarily formed from precursor compounds widely present in the environment. This paper reviews the concentrations, compositional characteristics, and key polluted areas of N-nitrosamines in indoor air and the environmental atmosphere. It summarizes primary emission sources from industrial and lifestyle activities and secondary formation mechanisms of N-nitrosamines in the atmosphere. This review provides a reference for research on the environmental geochemical behavior of atmospheric N-nitrosamines and public risk prevention and monitoring.