title: Effects of aging and sediment composition on hexachlorobenzene desorption resistance compared to oral bioavailability in rats.
abstract: Studies were conducted to assess the effects of black carbon, clay type and aging (1-1.5yr) on desorption and bioavailability of hexachlorobenzene (HCB) in spiked artificial sediments. Tenax (a super sorbent)-mediated desorption was used to examine the effects of these parameters on the physicochemical availability of HCB. The Tenax-mediated desorption of HCB from the four aged artificial sediments exhibited biphasic kinetics. The fast desorbing fractions ranged from 64.8% to 22.3%, showing reductions of 4.0-18.9% compared with freshly-spiked sediments. Statistical analysis on the fast desorbing fractions showed that all three treatment effects (i.e., montmorillonite clay, black carbon content, and aging) were significant. Two sediments with higher black carbon content exhibited much greater aging effects (i.e., greater reduction in fast desorbing fraction) than the other two sediments without the addition of black carbon. For both freshly-spiked and aged sediments, the desorption resistant sediment-bound HCB (i.e., slow desorbing fraction) correlated reasonably well to previously reported rat fecal elimination of HCB, which is a measure of the non-bioavailable fraction of sediment-bound HCB. A similar correlation was also observed between fast desorbing fraction and previously reported accumulation of HCB in the rat body (carcass+skin). These observations suggest that physicochemical availability, as defined by the desorption of HCB from sediments, provides a reasonable prediction of the oral bioavailability of sediment-bound HCB to rats. These results showed that montmorillonite clay, black carbon and aging reduced physicochemical availability and ultimately bioavailability of sediment-bound HCB.
authors.affiliation: Toxicology and Environmental Research and Consulting, The Dow Chemical Company, 1803 Building, Midland, MI 48674, United States.
authors.forename: Yunzhou
authors.initials: Y
authors.lastname: Chai
authors.forename: John W
authors.initials: JW
authors.lastname: Davis
authors.forename: Shakil A
authors.initials: SA
authors.lastname: Saghir
authors.forename: Xiujin
authors.initials: X
authors.lastname: Qiu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Budinsky
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bartels
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D000818:Animals; D001682:Biological Availability; D002244:Carbon / Q000737:chemistry; D000077215:Clay; D004784:Environmental Monitoring; D005243:Feces / Q000737:chemistry; D005659:Fungicides, Industrial / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine; D041981:Gastrointestinal Tract / Q000378:metabolism; D019015:Geologic Sediments / Q000737:chemistry*; D006581:Hexachlorobenzene / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D051381:Rats; D011916:Rats, Inbred F344; D012867:Skin / Q000378:metabolism; D053260:Soot / Q000737:chemistry; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D000538:Aluminum Silicates; D005659:Fungicides, Industrial; D053260:Soot; D006581:Hexachlorobenzene; D002244:Carbon; D000077215:Clay