title: Bioaccessibility of nitro- and oxy-PAHs in fuel soot assessed by an in vitro digestive model with absorptive sink.
abstract: Ingestion of soot present in soil or other environmental particles is expected to be an important route of exposure to nitro and oxygenated derivatives of polycyclic aromatic hydrocarbons (PAHs). We measured the apparent bioaccessibility (Bapp) of native concentrations of 1-nitropyrene (1N-PYR), 9-fluorenone (9FLO), anthracene-9,10-dione (ATQ), benzo[a]anthracene-7,12-dione (BaAQ), and benzanthrone (BZO) in a composite fuel soot sample using a previously-developed in vitro human gastrointestinal model that includes silicone sheet as a third-phase absorptive sink. Along with Bapp, we determined the 24-h sheet-digestive fluid partition coefficient (Ks,24h), the soot residue-fluid distribution ratio of the labile sorbed fraction after digestion (Kr,lab), and the maximum possible (limiting) bioaccessibility, Blim. The Bappof PAH derivatives was positively affected by the presence of the sheet due to mass-action removal of the sorbed compounds. In all cases Bappincreased with imposition of fed conditions. The enhancement of Bappunder fed conditions is due to increasingly favorable mass transfer of target compounds from soot to fluid (increasing bile acid concentration, or adding food lipids) or transfer from fluid to sheet (by raising small intestinal pH). Food lipids may also enhance Bappby mobilizing contaminants from nonlabile to labile states of the soot. Compared to the parent PAH, the derivatives had larger Kr,lab, despite having lower partition coefficients to various hydrophobic reference phases including silicone sheet. The Blimof the derivatives under the default conditions of the model ranged from 65.5% to 34.4%, in the order, 1N-PYR > ATQ > 9FLO > BZO > BaAQ, with no significant correlation with hydrophobic parameters, nor consistent relationship with Blimof the parent PAH. Consistent with earlier experiments on a wider range of PAHs, the results suggest that a major determinant of bioaccessibility is the distribution of chemical between nonlabile and labile states in the original solid.
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, PR China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, New Haven, CT, 06504-1106, United States. Electronic address: joseph.pignatello@ct.gov.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Pignatello
authors.affiliation: Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, PR China. Electronic address: taos@pku.edu.cn.
authors.forename: Shu
authors.initials: S
authors.lastname: Tao
mesh_terms: D065966:Absorption, Physicochemical; D000880:Anthraquinones / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics; D001551:Benz(a)Anthracenes / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics; D001682:Biological Availability; D004063:Digestion / Q000502:physiology*; D005449:Fluorenes / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics; D065569:Gastrointestinal Absorption / Q000502:physiology; D006801:Humans; D008954:Models, Biological; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics*; D011721:Pyrenes / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics; D012828:Silicones / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics*; D053260:Soot / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D000880:Anthraquinones; D001551:Benz(a)Anthracenes; D005449:Fluorenes; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; D012828:Silicones; D012989:Soil Pollutants; D053260:Soot; C028401:9-fluorenone; C012768:benzanthrone; C032668:1-nitropyrene
keywords: Bioaccessibility; Digestive model; PAH derivatives; Soot