Bioaccessibility and health risk assessment of trace metals in Nanjing park dust

Abstract

The bioaccessibility, chemical fractions, and total concentrations of Hg, As, Mn, Ni, Cd, Cr, Cu, Pb and Zn were determined in 17 urban park dust samples collected from a megacity in China. The geoaccumulation index indicated heavy Hg pollution, moderate Cd pollution, and slight to moderate Cu, Pb and Zn pollution. The inhalation bioaccessibility measured by the Artificial Lysosomal Fluid method decreased in the order of Cd > Zn > Mn > Ni > Pb > As > Cr > Cu. The ingestion bioaccessibility measured by the Physiologically Based Extraction Test decreased in the order of Cd > Zn > Mn > Cu > Pb > As > Ni > Cr. The modified European Community Bureau of Reference method was used to extract the chemical fractions of trace metals. As (87%), Cr (87%), and Hg (99%) were predominantly found in residual fraction (F4), whereas Cd was predominantly found in water soluble and exchangeable fraction (F1 34%) and carbonate, oxidizable and reducible fraction (F2 27%). The first two chemical fractions of the trace metals were closely correlated with their bioaccessibilities. The carcinogenic and non-carcinogenic risks of exposure to trace metals in park dust were assessed using inhalation bioaccessibility and ingestion bioaccessibility. The hazard indexes of all investigated trace metals were below the safe level of 1. The carcinogenic risks of As, Ni, Cd and Cr were also below the acceptable level (10−6), indicating that there was no non-carcinogenic or carcinogenic risk from trace metals in the park dust.