Human health risk due to consumption of vegetables contaminated with carcinogenic polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are persistent, toxic, and carcinogenic contaminants present in soil ecosystem globally. These pollutants are gradually accumulating in wastewater-irrigated soils and lead to the contamination of vegetables. Food chain contamination with PAH is considered as one of the major pathways for human exposure. This study was aimed to investigate the concentrations of PAH in soils and vegetables collected from wastewater-irrigated fields from metropolitan areas of Beijing, China. Origin of PAH, daily intake, and health risks of PAH through consumption of contaminated vegetables were studied. Soil samples were collected from the upper horizon (0-20 cm) of both wastewater-irrigated and reference sites and sieved (< 2 mm mesh) and then followed by freeze-drying at -50A degrees C and 123 A +/- 2 Pa. Standing vegetables were also collected from the same sites used for soil sampling and divided into roots and shoots, thoroughly washed with deionized water, and freeze-dried. PAH were extracted using the Soxhlet method with 200 mL DCM for 24 h, and the extracts were cleaned with silica adsorption chromatography prepared with silica gel, alumina, and capped with anhydrous sodium. The final concentrated extracts (soil and vegetable) were analyzed using gas chromatography-mass spectrometry (Agilent 6890). Bioaccumulation factors, daily intake of PAH, and carcinogenicity of PAH were calculated by different statistical equations. Results indicate that the soils and grown vegetables were contaminated with all possible carcinogenic PAH (declared by USEPA 2002) except indeno[1,2,3-c,d]pyrene. The highest concentration (242.9 mu g kg(-1)) was found for benzo(k)fluoranthene (BkF), while lowest (79.12 mu g kg(-1)) for benzo[a]pyrene (BaP). The emission sources of PAH were both pyrogenic and petrogenic in nature. However, the total concentrations of PAH were lower than the permissible limits set by different countries like Canada, Denmark and Germany. Highest total PAH concentration was found in the shoots of Spinacia oleracea L., while lowest in the roots of Raphanus sativus. In this study, the values of total toxic BaP equivalent (TEQ) through consumption of vegetables were found in order of S. oleracea L. > Lactuca sativa L. > Brassica oleracea L. > Brassica napus > Brassica juncea L. > R. sativus L. The data indicate that the daily intake of BaP through consumption of vegetables for adults were lower than virtually safe dose set by the Dutch National Institute for Public Health and the Environment. Our findings indicate that PAH concentrations in soil and vegetables were lower than their respective permissible limits set by different organizations. However, the highest intake of total PAH was estimated through consumption of S. oleracea L. for both adults and children.