Bioavailability and mass balance studies of a commercial pentabromodiphenyl ether mixture in male Sprague-Dawley rats.

Polybrominated diphenyl ethers (PBDE) are common flame retardants used in polyurethane foam, high impact polystyrene, and textiles which appear to be increasing in the environment and biota. Two PBDE congeners that are particularly prominent in environmental samples are 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99). These two congeners are major components in penta-BDE formulations which constitute a minor percentage of the commercial PBDE market. In order to determine the bioavailability and bioconcentration potential of these PBDEs, we have conducted a feeding experiment in rats, dosing with low amounts of a commercial penta-BDE mixture for 21 days to mimic an environmental exposure. The carcasses, livers, and feces from control and dosed rats were quantitated for PBDEs by a high resolution GC-MS isotope dilution method. Between 25% and 50% of each of the dosed congeners was retained in the rats with the liver being a minor depot (<1% of the dose). Fecal excretion accounted for 4-12% of the dosed congeners. A large percent of the dose (40-60%) was not recovered indicating that metabolic transformations may have occurred in the rats. Hydroxylated metabolites were qualitatively identified in the feces and carcass by GC-MS. The relative congener distribution in each tissue was nearly identical to the congener distribution of the commercial mixture. Conclusions from the study suggest that the tetra- to hexa-BDEs present in commercial penta-BDE formulations are largely bioavailable, that bioavailability in the rat is not dependent on the degree of bromination, and that metabolism may occur to a large extent during a chronic exposure.

Analysis of mono- to deca-brominated diphenyl ethers in chickens at the part per billion level.

Polybrominated diphenyl ethers (PBDEs) are flame retardants which have been found to be increasing in the environment. Because of structural similarities to the polychlorinated biphenyls and concerns that PBDEs may be widespread, we have investigated their presence in a food source, namely chickens. A GC-MS method was developed to analyze mono- through deca-BDEs in chicken fat samples. The method utilized GC pressure programming and selected ion monitoring to quantitate PBDEs at the low part per billion level. Four 13C-labeled surrogates were used to determine recoveries; recoveries averaged from 76% to 114%. Thirteen chickens from the Southern US and a composite sample of chickens from North Dakota were analyzed by this method. The total concentrations of PBDEs on a whole weight basis ranged from 1.7 ppb in North Dakota chickens to 39.4 ppb in a chicken from Arkansas. On a lipid weight basis, these levels were lower than those generally found in fish and fish-eating mammals. The PBDE pattern was also different from other samples reported; penta-BDEs rather than tetra-BDEs were the most prominent congeners.

Survey of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and non-ortho-polychlorinated biphenyls in U.S. meat and poultry, 2007-2008: effect of new toxic equivalency factors on toxic equivalency levels, patterns, and temporal trends.

A statistically based survey of dioxins and dioxin-like compounds in domestic meat and poultry was conducted by the U.S. Department of Agriculture (USDA) from September 2007 to September 2008. Seventeen toxic polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and four non-ortho-polychlorinated biphenyls (no-PCBs) were measured in 510 beef (steer/heifer), market hog, young turkey, and young chicken samples. The results of the survey showed the sum of PCDD/F and no-PCB toxic equivalencies (sum-TEQs) ranging from not detected to 4.5 pg/g of lipid. Mean sum-TEQ levels for beef, turkey, chicken, and pork were 0.66, 0.61, 0.17, and 0.16 pg/g of lipid, respectively. To compare the new survey data with data from previous USDA surveys in the mid-1990s and 2002-2003, TEQs from all data sets were calculated using the most recent 2005 toxic equivalency factors (TEFs). The results of the recalculation on the older survey data was a small increase (4-13%) in mean TEQs for the mid-1990s data, which initially used pre-1994 TEFs, and a small decrease (2-4%) for the 2002-2003 data, which initially used 1998 TEFs. A comparison of the three surveys indicates declining TEQ trends in all slaughter classes over the 10 year period; however, the congener patterns remain relatively constant between 2002 and 2008, indicating similar animal exposures to dioxins and dioxin-like compounds during these time periods. Several samples from the 2008 survey with the highest TEQ values are undergoing follow-up investigations to determine possible sources that may be contributing to these levels.

Statistically designed survey of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and co-planar polychlorinated biphenyls in U. S. meat and poultry, 2002-2003: results, trends, and implications.

To obtain information on dioxin levels in the human diet, the Food Safety and Inspection Service of the United States Department of Agriculture recently determined levels of dioxin-like compounds (dioxins/dibenzofurans/PCBs) in four major slaughter classes (steers and heifers, market hogs, young chickens, and young turkeys) that comprise over 90% of the meat and poultry production in the United States. The data were analyzed and compared to data from smaller surveys carried out from 1994 to 1996. These surveys were conducted by different laboratories nearly 10 years apart, so a direct comparison of the data was not straightforward. Three approaches were taken: (1) comparison with nondetects set to zero, (2) comparison with nondetects set to half the limit of detection, and (3) comparison applying the earlier surveys' limits of detection to the newer data. The data analyses indicated that dioxin levels appear to have declined in three of the four slaughter classes, with young chickens, market hogs, and young turkeys declining 20-80%, while any declines in cattle dioxin levels, if real, are less than those observed in the other slaughter classes. Further study is needed to examine factors that might explain the differences in dioxin levels and distribution profiles in the four slaughter classes. A small number of market hog and steers/ heifers samples had dioxin toxic equivalency levels (TEQs) greater than 2 pg/g lipid weight. Follow-up investigations for those samples indicated a common source for the market hog samples (a dioxin-contaminated mineral supplement), but no commonality was found for the steers/ heifers samples.