Environ. Sci. Technol. 2008, 42, 2694–2700
Comparative Absorption and Bioaccumulation of Polybrominated Diphenyl Ethers following Ingestion via Dust and Oil in Male Rats J A N I C E K . H U W E , * ,† H E L D U R H A K K , † DAVID J. SMITH,† JANET J. DILIBERTO,‡ VICKI RICHARDSON,‡ HEATHER M. STAPLETON,§ AND LINDA S. BIRNBAUM‡ United States Department of Agriculture (USDA), Agricultural Research Service (ARS) Biosciences Research Laboratory, Fargo, North Dakota 58105, United States Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Experimental Toxicology Division, Research Triangle Park, North Carolina, and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina
Received October 31, 2007. Revised manuscript received December 12, 2007. Accepted December 17, 2007.
Household dust has been implicated as a major source of polybrominated diphenyl ether (PBDE) exposure in humans. This finding has important implications for young children, who tend to ingest more dust than adults and may be more susceptible to some of the putative developmental effects of PBDEs. Absorption parameters of PBDEs from ingested dust are unknown; therefore, the objectives of this study were to determine and to compare the uptake of PBDEs from either household dust (NIST Standard Reference Material 2585) or a corn oil solution. Male rats were administered dust or corn oil doses at 1 or 6 µg of PBDEs kg-1 body wt in the diet for 21 days (n ) 4 rats per group). The concentrations of 15 PBDEs were measured in adipose tissue and liver from each treatment group and showed that bioconcentration was congener dependent, but for the majority of congeners, the concentrations did not differ with either dose level or dose vehicle. Hepatic Cyp2b1 and 2b2 mRNA expression increased in rats receiving the higher PBDE doses, suggesting potential effects on metabolic activity. Retention of PBDEs in tissues ranged from 0.94. tissues that were generally 10–50% of the concentration in low-dose rat tissues and 1–20% the concentration in highdose rat tissues for these congeners. Given the presence of PBDEs in the chow, the levels of PBDEs measured in the control rats were subtracted from the dosed rat levels to determine the absorption and bioaccumulation of the doses. To assess whether the rats were approaching a steady state body burden after 21 days of dosing, groups of three rats fed the high oil dose were killed at intervals throughout the study. Because the most persistent PBDEs tend to deposit in the adipose tissues, epididymal fat was analyzed as a surrogate for lipid-based body burden. Typical uptake curves for three of the most prevalent congeners (BDEs-47, 99, and 153) are shown in Figure 1. All major tri- to octa-congeners found in the fat had reached or were approaching a steady state concentration after 14 days of dosing (no statistical differences between PBDE concentrations on days 14 and 21, p < 0.05). Nona- and deca-BDEs were not consistently detected in the adipose tissues above that of controls (see Supporting Information for actual concentrations in control and dosed rat adipose tissue). Bioconcentration factors (BCFs) for PBDEs in the epididymal fat and liver were used to compare the uptake of PBDEs from the four dose groups after 21 days of dosing (Figure 2). In general, the BCFs for adipose tissue were inversely related to the degree of bromination and ranged between 7 and 24 for tri- to hexa-BDEs, 1–6 for hepta- to nona-BDEs, and
