Concentration level, health risk assessment and source apportionment of nitrosamines in PM2.5 in Urumqi during winter time

Abstract

Nitrogen-containing organic compounds (NOCs) in atmospheric particulate matter are important species for the formation of brown carbon. N-nitrosamines are a class of NOCs which are carcinogenic to humans. In this paper, nine nitrosamines of PM2.5 were analyzed by gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS) in a multiple reaction monitoring (MRM) mode in Urumqi, Xinjiang. The aim is to reveal the concentration level, assess the carcinogenic risk and identify the possible emission source of nitrosamines during winter time. The results show that total nitrosamine concentrations range from 1.54 to 23.22 ng m−3, with a daily average of 4.47 ng m−3. N-nitrosodimethylamine (NDMA), N-nitrosodi-n-butylamine (NDBA), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR) and N-nitrosodiphenylamine (NDPhA) are predominant compounds for more than 80% of the total nitrosamines. The average concentrations of nitrosamines in each carcinogenic classification are 2.68, 1.45, and 0.34 ng m−3, respectively. Cumulative lifetime cancer risk assessment indicates that adult exposure to nitrosamine concentrations of 1 h per day results in 1.15 excess cancer cases per million population. Furthermore, based on correlation analysis and Positive Matrix Factorization, NDMA and NDBA may from disinfection process for water treatment, landfills, cooking and vehicle exhaust; NPYR and NDEA may be mainly emitted from cooking and tobacco combustion. However, NDPhA presents a negative correlation with other nitrosamines, probably resulting from the atmospheric reaction source. These findings not only draw attention to the systematic research of nitrosamines in PM2.5 but also provide a new perspective on the monitoring and management of regional air pollutants.