Soils and tobacco polycyclic aromatic hydrocarbon characterisation and associated health risk assessment in Qingzhen city, Southwest China

Purpose The present study aimed to characterise and identify the sources of polycyclic aromatic hydrocarbons (PAHs) in tobacco and soils and assess the potential carcinogenic risks (CRs) and non-carcinogenic risks (NCRs) of these PAHs to farmers. Understanding the characteristics of PAHs in the soil-tobacco system will provide regulators with a guide for establishing control standards for PAHs in ambient media. Methods The sample PAHs were extracted using dichloromethane and measured using gas chromatography-mass spectrometry. Positive matrix factorisation, principal component analysis, and diagnostic ratios were used to identify the primary sources of PAHs. The CRs and NCRs to farmers of the 16 PAHs were estimated based on the methods outlined by the United States Environmental Protection Agency (US EPA). Results The concentrations of Sigma(16)PAH in soils and tobacco ranged from 72.94 to 941.77 mu g kg(-1) and 130.02 to 1545.35 mu g kg(-1), respectively. The source analysis results indicated that coal combustion (15-20%), coke combustion (11-19%), oil leakage (9-21%), traffic emissions (19-24%), petroleum combustion (9-27%), and biomass combustion (12-15%) were the dominant sources of PAHs in the soil-tobacco system. Total CR values in soils and tobacco varied from 9.54 x 10(-8) to 5.31 x 10(-7) and 1.95 x 10(-7) to 4.16 x 10(-6), respectively, and the total NCR values in soils and tobacco ranged from 1.49 x 10(-6) to 1.28 x 10(-4) and 1.32 x10(-6) to 4.67 x 10(-4), respectively. A total of 60.4% of the tobacco samples exposed to benzo[a]pyrene (BaP) were higher than 1 x 10(-6) but lower than 1 x 10(-4). Conclusion The PAH concentrations in the soil samples observed in this study ranged from low to moderately polluted. In soils and tobacco, 3- to 5-ring PAHs were dominant. Petroleum, coal, and biomass combustion, as well as plastic film and fertiliser consumption in the cultivation and management of tobacco, were the primary PAH sources. The CR of BaP in most tobacco samples was low, and the NCR of PAHs was acceptable.