Fred Hileman

Physical/chemical properties of 2,3,7,8-TCDD

Abstract The efforts to characterize the transport and fate of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been delayed because of insufficient information on the physical/chemical properties of the compound. The work presented in this paper involves the efforts to establish a sound data base for the physical/chemical properties of TCDD. The information includes literature values of measured and estimated properties and values of measured and estimated properties prepared by these authors. Specifically the vapor pressure and heat of sublimation were developed experimentally by these authors (Schroy, et.al., 1984) and are intended for use in transport modeling. The vapor pressure curve presented in the attached fiqure shows the expected behaviour for the solid, liquid and subcooled liquid phases. The possibility of supersaturated vapor concentrations that may exist in solution systems would explain the unusually high sublimation pressures reported for TCDD purification protocols (Aniline, 1973) and shown on the vapor pressure figure. The table of physical/chemical properties, including the Antoine Equation constants for the curves shown in the vapor pressure figure, summarize all available data to date.

Relative distribution of 2,3,7,8-tetrachlorodibenzo-p-dioxin human hepatic and adipose tissues

Paired human hepatic and adipose tissues from 26 people were assayed for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). On a whole tissue weight basis, TCDD concentration in the liver was about one-tenth that in the adipose tissue. When expressed in total tissue lipid basis, the TCDD concentrations in the liver and adipose tissue were about equal. At low levels of exposure, presumably below those necessary to cause hepatic enzyme induction, TCDD appeared to be partitioning into the human liver predominantly on the basis of its lipid solubility in that tissue store. The partitioning behavior of TCDD in the livers of humans exposed to higher levels of TCDD is currently unclear.

Measurement of the photoinduced loss of vapor phase TCDD

Abstract The photoloss of vapor 2,3,7,8-TCDD was observed to occur in the UV region of the light spectrum from 250 nm to 340 nm with an average quantum yield of 0.033-0.046.

An analytical assessment of the bioavailability of dioxin contaminated soils to animals

Abstract Single-dose gavage studies of Times Beach, MO and Newark, NJ dioxin contaminated soils were done to determine relative bioavailability in guinea pigs. GC/MS analysis of the animals livers showed that dioxins in Times Beach soil were more readily absorbed than dioxins in Newark soil. The liver results also revealed that bioavailability decreased for higher chlorinated dioxins. After 60 days the relative clearance of each congener was similar except for octachlorodibenzo-p-dioxin which was strongly retained by the liver.

Analysis of 2,3,7,8-tetrachlorodibenzofuran by fused silica GC combined with atmospheric pressure ionization MS

Abstract A detection limit of 0.5 pg was obtained for 2,3,7,8-tetrachlorodibenzofuran using GC-atmospheric pressure ionization MS with nitrogen as the makeup gas. All of the tetrachlorodibenzofuran isomers studied showed the same mass spectrum. The possible interference of hexachlorodiphenyl ethers was also examined.

Synthesis of polychlorinated dibenzofurans with confirmation by molecular structure/gas chromatographic retention relationships

Abstract Polychlorinated dibenzofurans (PCDFs) have been synthesized by pyrolysis of individual polychlorobiphenyl cogeners. In certain instances additional PCDFs were formed by either photolysis or chlorination of isolated PCDF congeners. The PCDFs formed by these independent reaction routes were cross correlated with each other to confirm the identity of a given congener. A final quality control step involved the development of a mathematical model which describes the relationship between molecular structure and gas chromatographic retention. The model variables include: 1) the substitution pattern of the chlorines on either of the aromatic rings and 2) interaction factors between chlorines on different rings. This model has been used to validate the many syntheses used to prepare the PCDFs and evidence suggests that the general principles may be applied to structurally similar systems.

Dibenzofuran in diphenyl oxide and the relationship to brominated dibenzofurans in brominated diphenyl oxide

Abstract A method was developed for the ppb level analysis of dibenzofuran (DBF) in diphenyl oxide (DPO). Complimentary analytical techniques for the analysis of polybrominated dibenzofurans (PBDFs) in polybrominated diphenyl oxides (PBDPOs) were also developed. The PBDFs in PBDPOs were found to be related to the presence of DBF in the original DPO.

An evaluation of the molecular structure of octachlorodibenzofuran

Abstract Several properties of halogenated dibenzofurans indicated unusual behavior when the 1 and 9-positions were halogenated. This behavior was thought to be due to steric crowding causing the molecule to twist out of planarity to relieve the crowding. In a more definitive study, the molecular structure of octachlorodibenzofuran was determined by x-ray diffraction and was found to be planar with crowding of all chlorines, particularly those at the 1 and 2-positions rather than the expected 1 and 9-positions.

The ultraviolet photolysis of tetrachlorodibenzofurans

Abstract Several tetrachlorodibenzofuran isomers were photolyzed by ultraviolet irradiation and the relative amounts of the various trichlorodibenzofurans produced were determined. A simple set of guidelines for predicting the relative amounts of these photolysis products has been formulated.

Methodology for the analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin in feces

Abstract A methodology for the analysis of 2378-TCDD in feces is presented. This method involves complete digestion of lyophilized feces, extraction and cleanup by routine column chromatography. Analysis is performed by high resolution GC/MS to detect 2378-TCDD concentrations in the sub part-per-trillion range. Successful analysis allows for the estimation of the adipose 2378-TCDD concentration as well as an estimation of dosage.