Sources and potential health indicators in urban aerosols revealed by gas chromatography-mass spectrometry combined with nitrogen chemiluminescence detector: evidence from a megacity (Tianjin) of China

Understanding the chemical complexity of atmospheric aerosols and their associated health risks remains a significant challenge, particularly in rapidly urban regions. Although PM_2.5-associated organic compounds have received growing attention, nitrogen-containing hazardous species such as nitrosamines remain under-explored. Here, comprehensive chemical characterization of urban PM_2.5 was conducted using two-dimensional gas chromatography–mass spectrometry (GC × GC-MS) for non-targeted profiling, together with a nitrogen chemiluminescence detector (NCD) for the quantification of nitrosamines at a trace level of 1.1 ppb. Aerosol samples were collected in Tianjin (a mega city in China) in 2022, including the Beijing Winter Olympics period. The study revealed seasonal variations in hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), with elevated levels of carcinogenic nitrosamines observed in winter, particularly during the Olympics. And interestingly, the estimated carcinogenic risk of nitrosamines is quite consistent with the local incidence rate in Tianjin. These findings emphasize the need for targeted pollution control strategies to minimize hazardous aerosols and human exposure, particularly during large-scale events.