Human TCDD analysis

Figure 10 illustrates the results of a typical analysis of a 10-gram sample of human milk to which 0.1 ppb TCDD has been added. Blank... 

Polychloro-benzenes, polybromo-benzenes, and dioxins (TCDD) are among these compounds. They were discovered when the analysis techniques improved. Especially the development of GC-MS has contributed to the knowledge of the distribution of these compounds. Effects on humans are the development of chloracne, suppression of the immune system, and some compounds are probably carcinogens (Shaw 1993). As a consequence of the ubiquitous nature of PCBs, humans are exposed via many sources. 

A median half-life of 7.1 years for excretion in humans was estimated for 2,3,7,8-TCDD in a group of 36 Vietnam veterans." Further studies have indicated that the half-life may be closer to 8.7 years." CDDs are lipophilic compounds that can concentrate in maternal milk. An analysis of 526 individual milk samples from a German population indicated a mean 2,3,7,8-TCDD level of 3.2 ng/kg milk fat. ... 

JA Boyd National Institute of Environmental Health Sciences (NIEHS Perform a molecular genetic analysis of pathologic conditions of the human uterus, resulting from exposure to chemicals such as 2,3,7,8-TCDD ... 

TP Brent St. Jude Children s Research Hospital Develop histochemical assays for MGMT (06-alkylguanine-DNA alkylt-ransferase, previously called GATase) expression in human tumor and tissue preparations Detailed analysis of the structure, function, and regulation of MGMT activity will ultimately enable the to prediction of tumor resistance, as well as an individual s susceptibility to carcinogenesis induced by chemicals such as 2,3,7,8-TCDD ... 

Individuals exposed through industrial accidents or environmental contamination. Very extensive residential contamination by 2,3,7,8-TCDD occurred in Seveso, Italy, when a 2,4,5-TCP reactor exploded in 1976 (Mocarelli et al. 1991). The contaminated area was divided into three zones based on the concentration of 2,3,7,8-TCDD in the soil. Families in zone A, the most heavily contaminated area based on soil 2,3,7,8-TCDD levels, were evacuated within 20 days of the explosion and measures were taken to minimize exposure of residents in nearby zones. A recent analysis of 19 blood samples from residents of zone A, which were collected and stored shortly after the accident, showed serum lipid levels of 2,3,7,8-TCDD that ranged from 828 to 56,000 ppt. These serum lipid levels are among the highest ever reported for humans (Mocarelli et al. 1991). 

These herbicides have been used extensively in silviculture for control of deciduous trees in conifer forests (13). As a military defoliant, 2,4,5-T was mixed with 2,4-dichlorophenoxy acetic acid (2,4-D), and an estimated 10 million gallons of this mixture was applied in South Vietnam under the name of Agent Orange. Subsequent analysis of human samples from South Vietnam has found 2,3,7,8-TCDD at elevated levels compared to samples from North Vietnam where Agent Orange was not used (14). 

In Figure 3, there is a suspect point plotted at 6.35 cm, taken in August 9, 1984, with a concentration of 8.2 ppb. There were two cores taken in August of 1984 for Plot A. The corresponding concentration in the second core was found to be 98 ppb. All TCDD analyses for the August 1984 cores yield concentrations between 86 and 115 ppb. We conclude that sample is an outlier probably due to human error in the analysis. 

The major rationale for the cleanup of sites contaminated with TCDD is that the contamination by this highly toxic compound presents a major risk to human health. Risk is made up of the inherent hazard of the compound and the extent of exposure to the compound. Operationally, it has been assumed that most of the TCDD that can be detected by chemical analysis is available to cause toxicity. There has been little evidence until recently regarding the validity of this assumption. Several studies (discussed below) have suggested that the entire amount of TCDD that can be detected in a soil sample may not be completely bioavailable. Rather, some portion of the TCDD may be too tightly sorbed to the matrix to be released in biological systems. Further, the presence of other chemicals in the matrix may interfere with gastric uptake of TCDD or with the receptor mediated toxicity of TCDD. 

Recalling levels of the PCDD and PCDF isomers previously reported in adipose tissue from a North American population (Tables I-II) (16 17), the most toxic isomer, 2,3,7,8-TCDD, is found in the lowest concentration, whereas the octachlorodioxin is found in the highest concentration. We and others have reported similar results of analysis of separate sample populations in the United States (1,18,19). These results emphasize the need to consider other dioxin and dibenzofuran isomers, in addition to the 2,3,7,8-TCDD isomer, when an evaluation of potential human health risk is performed. 

Table III summarizes some of the reported and calculated levels of PCDD and PCDF isomers in human breast milk from populations in the south and north of Vietnam ( 3), and the United States (1 ). It is noteworthy that analysis of 9 adipose tissue samples taken in 1984 from individuals living in the north of Vietnam showed no detectable concentrations of 2,3,7,8-TCDD at a detection limit of 2 ppt (3). As expected, the milk pattern and levels on a lipid basis are similar to that reported for adipose tissue (2,3,16) (Tables I and II).

This analysis indicates that remediation would not be Indicated at this site. Of course. In any Isolated instances where children or adults might be exposed to TCDD soil concentration In excess of 500-1000 ppb, e.g., hot spots, clean-up of these would need to be considered. Concentrations as high as 1000 ppb In soil, assuming 1% dermal bioavailability, would not be expected to cause chloracne with repeated exposure, based on the work of Kligman who dermally applied TCDD to human volunteers (57.59). 

Frericks M, Burgeon LD, Zacharewski TR, Esser C (2008) Promoter analysis of TCDD-inducible genes in a thymic epithelial cell line indicates the potential for cell-specific transcription factor crosstalk in the AhR response. Toxicol Appl Pharmacol 232 268-279 Gaido KW, Maness SC, Leonard LS, Greenlee WF (1992) 2, 3,7, 8-Tetrachlorodibenzo-p-dioxin-dependent regulation of transforming growth factors-alpha and -beta 2 expression in a human keratinocyte cell line involves both transcriptional and post-transcriptional control. J Biol Chem 267 24591-24595... 

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