Adipose tissue 2,3,7,8-TCDD levels

Calculated using the reported mean current adipose tissue 2,3,7,8-TCDD level of 296 ng/kg, half-life of 8.5 years (Michalek et al. 1996), background 2,3,7,8-TCDD concentration of 5 ng/kg lipid, and 1-33 years of elapsed time. 

When pushed to the limit by overriding human health concerns, residue chemists have achieved detection limits of Ippt (Ingkg ) or even into the low ppqr (1 pg kg ) range. An example at the 1 ppt level is provided by methods for 2,3,7,8-tetrachlorodibenzodioxin (TCDD) in milk and TCDD in adipose tissue. Eor relatively clean matrices such as water and air, preconcentration on solid-phase adsorbents followed by GC or gas chromatography/mass spectrometry (GC/MS) can provide detection limits of 1 ng m and less for air (examples in Majewski and Capel ) and 1 ngL and less for water (examples in Larson et A summary of units of weight and concentration used to express residue data is given in Table 1. 

CDDs have been found in all samples of adipose tissue and blood (serum lipids) from individuals with no known previous exposure. This indicates that all people are exposed to small amounts of CDDs. Levels of 2,3,7,8-TCDD in serum from the general population typically range from 3 to... 

Various populations in Missouri were exposed to 2,3,7,8-TCDD in 1971 and 1972 as a result of spraying approximately 29 kg of 2,3,7,8-TCDD-contaminated waste oil on horse arenas, parking lots, and residential roads for dust control (Andrews et al. 1989). The oils originated from an industrial waste residue contaminated with 2,3,7,8-TCDD at levels of 305 ppm (Needham et al. 1991). An exposed group of 51 adults have been the subject of several studies. Adipose tissue levels, as well as paired human serum levels, were measured for 36 of these persons. Sixteen of the individuals were residents of areas where roadways had been sprayed and had mean 2,3,7,8-TCDD adipose tissue levels of 21.1 ppt (range,... 

Intermediate-duration studies have also been conducted with radioactively labeled OCDD. OCDD had similar patterns of distribution and similar half-lives as 2,3,7,8-TCDD in Sprague-Dawley (Norback et al. 1975) and Fischer 344 rats (Bimbaum and Couture 1988 Bimbaum et al. 1989a). Most of the absorbed amount (50-97%) was found in the liver and was associated with the microsomal fractions. Skin- and adipose-tissue levels were much lower. Radioactivity was also detected in the kidneys, heart, testes, skeletal muscle, and serum. 

The elimination of 2,3,7,8-TCDD from humans was evaluated using a PBPK model developed by Kissel and Robarge (1988). The steady-state adipose tissue concentration predicted by the model was similar to the lipid-based blood levels reported in the general population with no known special exposure to... 

TCDD in blood of veterans with adipose burdens >10 ppt. The apparent half-lives increased as the adipose tissue concentration approached the steady-state level associated with background exposure. The model also predicted reasonably well the elimination of 2,3,7,8-TCDD from a volunteer who ingested a single 2,3,7,8-TCDD dose. 

There is a limited amount of data on the toxicokinetic properties of CDDs in children or immature animals. A toxicokinetic model was constructed that accurately predicted the lifetime concentrations of 2,3,7,8-TCDD in adipose tissue, blood, liver, and feces at different ages (Kreuzer et al. 1997). In formula-fed infants, the model predicted that 2,3,7,8-TCDD lipid levels would decrease during the first... 

Methods for measuring CDDs in biological fluids and tissues are available. Adipose tissue and liver are the primary storage site for CDDs and tissue samples have been analyzed in several studies. It was demonstrated that the relative (lipid-based) levels of 2,3,7,8-TCDD are similar in hepatic and adipose tissues (Leung et al. 1990a) and between adipose tissue and serum (Patterson et al. 1988 Schecter et al. 1990) from the same patients. However, this was not the case for more highly chlorinated dioxins for... 

TCDD was detected in adipose tissue samples of two herds in the eastern Canadian Arctic at levels of 0.73 and 0.14 ng/kg, but was not detected in tissue samples from other herds at detections limits as low as 0.03 ng/kg (lipid basis). CDF levels were sub-ng/kg in all cases. TEQs were dominated by non-ortho substituted PCBs in all cases, and ranged from 0.33 ng/kg to 3.29 ng/kg in adipose tissue. The authors concluded that caribou tissues are therefore less contaminated than tissues from marine mammals. 

Needham et al. (1991) also showed that human adipose tissue concentrations of CDDs may be correlated with blood serum levels after adjusting for total lipid content. On a lipid basis, total CDD/CDFs are higher in blood than adipose tissue. Partitioning is not identical in these tissues 2,3,7,8-TCDD levels are almost identical in blood and adipose tissues, but OCDD levels are higher in blood. However, the presence of OCDD at levels of 5,000-10,000 pg/person when concentrations in food are generally in the low pg/g level suggests that the contribution of food to the OCDD body burden in humans requires further study (Rappe 1993). 

TCDD-contaminated waste oil). All study participants had detectable levels of 2,3,7,8-TCDD in their adipose tissue, but the group with known previous exposures had significantly higher levels than... 

Hoang TQ, Dai LC, Hong Thom LT. 1989. Effects of geographical conditions, soil movement and other variables on the distribution of 2,3,7,8-TCDD levels in adipose tissues from Vietnam Preliminary observations. Chemosphere 18 967-974. 

Schecter A, Ryan JJ. 1988. Polychlorinated dibenzo-p-dioxin and dibenzofuran levels in human adipose tissues from workers 32 years after occupational exposure to 2,3,7,8-TCDD. Chemosphere 17 915-920. 

Weerasinghe NCA, Schecter AJ, Pan JC, et al. 1986. Levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in adipose tissue of Vietnam veterans seeking medical assistance. Chemosphere 15 1787-1794. 

Ultimate proof of the widespread exposure to TCDD is exemplified by the fact that virtually all human adipose tissue samples contain TCDD at trace levels of 6 ppt.60 Adipose tissue of non-occupationally exposed humans has been found to contain concentrations of 18-122 pg TEQ g 1 fat, with a mean value of 56pg TEQ g 1 fat,43 a value 22 times higher than the concentration in beef fat (2.6 pg TEQ g 1 fat). 

Unlike adipose tissues discussed above, however, normalizing TCDD levels in non-adipose tissues to total lipids did not eliminate tissue differences in TCDD concentration, differences which ranged up to fourfold85. In an attempt to optimize... 

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