title: Transformation and bioaccessibility of lead induced by steamed bread feed in the gastrointestinal tract.
abstract: Accidental ingestion of contaminated soil has been recognized as an important pathway of human exposure to lead (Pb), especially for children through hand-to-mouth activities. Intake of food following the soil ingestion may affect the bioaccessibility of Pb in the gastrointestinal tract. In this study, the effect of steamed bread on the transformation and subsequent bioaccessibility of Pb in two soils was determined by the physiologically based extraction test (PBET). Two compounds, Pb(NO3)2and PbCO3, were included in the evaluation for comparison. In the gastric phase, Pb bioaccessibility decreased as the steamed bread increased due to the sorption of Pb on the undissolved steamed bread, especially in PbCO3, Pb bioaccessibility decreased from 95.03% to 85.40%. Whereas in the intestinal phase, Pb bioaccessibility increased from 1.85% to 5.66% and from 0.89% to 1.80% for Pb(NO3)2and PbCO3, respectively. The increase was attributed to the transformation of formed Pb carbonates into soluble organic-Pb complexes induced by the dissolved steamed bread at neutral pH as indicated by MINTEQ modeling. For the PbCO3-contaminated soil, the change in Pb bioaccessibility in both gastric and intestinal phases behaved like that in the pure PbCO3compound, the steamed bread increased the bioaccessibility of Pb in the intestinal phase, but the decreased bioaccessibility of Pb was observed in the gastric phase after the steamed bread was added. However, in the soil contaminated with free Pb2+or sorbed Pb forms, the steamed bread increased the Pb bioaccessibility in both gastric and intestinal phases. This was probably due to the higher dissolved organic carbon induced transformation of sorbed Pb (Pb sorbed by Fe/Mn oxides) into soluble Pb-organic complex. Results from this study indicated that steamed bread had an influence on the Pb speciation transformation, correspondingly affecting Pb bioaccessibility in the gastrointestinal tract.
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Junhong
authors.initials: J
authors.lastname: Kan
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Jingke
authors.initials: J
authors.lastname: Sima
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: xdcao@sjtu.edu.cn.
authors.forename: Xinde
authors.initials: X
authors.lastname: Cao
mesh_terms: D001682:Biological Availability; D001711:Biotransformation; D001939:Bread / Q000032:analysis*; D002254:Carbonates / Q000493:pharmacokinetics; D055598:Chemical Phenomena; D004784:Environmental Monitoring; D041981:Gastrointestinal Tract / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007854:Lead / Q000493:pharmacokinetics*; D009566:Nitrates / Q000493:pharmacokinetics; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D002254:Carbonates; D009566:Nitrates; D012987:Soil; D012989:Soil Pollutants; D007854:Lead; C043262:lead carbonate; C017461:lead nitrate
keywords: Bioaccessibility; Lead; PBET; Steamed bread; Transformation