Objective To explore the bioaccessibility of Pb in soil and its influencing factors in different functional areas of Guangzhou,and to assess the health risk of hand-to-mouth exposure to Pb.
Methods Triplicate soil samples were collected separately from 9 commercial districts,9 bus stations,9 residential areas,6 education areas,6 hospitals,and 7 parks in Guangzhou city as the research object.An in vitro digestion model was developed to assess bioaccessibility and health risks.Soluble Pb contents in simulated stomach and intestinal solutions,as well as Pb contents in soil,were determined using atomic absorption spectrometry.
Results The mean content of Pb in soils of different functional areas (90.34 mg/kg) exceeded the Pb background values in soils of Guangzhou,Guangdong,and China,respectively (P<0.05).The average bioaccessibility of Pb in the simulated stomach and intestinal phases were 36.55% and 9.03% respectively,in which the park soil presented the highest values (41.98%,14.17%).The average intakes of Pb by oral exposure among children and adults were 18.32 μg/d and 4.58 μg/d,respectively,in which the commercial district soil was the highest (28.14 μg/d,7.03 μg/d).The average bioaccessible amounts of Pb for children in simulated gastric and intestinal phases were 6.86 μg/d and 1.46 μg/d,with the highest values in the commercial district (13.03 μg/d,2.03 μg/d);and those for adults were 1.72 μg/d and 0.36 μg/d,respectively,also with the highest values in the commercial district (3.26 μg/d,0.51 μg/d).There were good linear relationships between bioaccessible values and total Pb content in soil (P<0.05).The values of absolute health risk coefficient (Ka) and the relative risk coefficients for simulated gastric phase (Kr1) and simulated intestinal phase (Kr2) in different functional areas were within the permitted maximum Pb intake levels for both children and adults as suggested by the World Health Organization (WHO).
Conclusion Soil Pb contamination levels vary in different functional areas in Guangzhou,but not exceed the WHO human health risk warning line.
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