TeCDD

Group of isomers with the same carbon skeleton and number of chlorines, e.g., TeCDDs Rat hepatoma cell line Polychlorinated biphenyls Polychlorinated dibcnzo-p-dioxin Polychlorinated dibenzofuran Polychlorinated dibenzo-p-dioxin and -furan Tetrachlorodibenzo-p-dioxin (-furan) Pentachlorodibenzo-p-dioxin ( furan) Hexachlorodibenzo-p-dioxin (-furan) Heptachlorodibenzo-p-dioxin ( furan)... 

H4IIE PCBs PCDD PCDF PCDD/F TeCDD (F) PnCDD (F) HxCDD (F) HpCDD (F)... 

TeCDD toxic equivalent factor (relative toxicity/potency to 2,3,7,8-TeCDD) World Health Organization... 

Among these was a preliminary investigation in 1980 of 2378-TeCDD in herring gull eggs, which found concentrations in eggs from Saginaw Bay,... 

A thorough analysis of atmospheric transport and deposition to the Great Lakes has been carried out using the HYSPLIT model developed by the US National Atmospheric and Oceanic Administration (NOAA) [28,29]. An emissions inventory of PCDD/Fs for North America in 1996 was used as input to the model. Factors considered in the fate and distribution were meteorological data, vapor-particle partitioning, aerosol characteristics, reaction with hydroxyl radicals, photolysis, and dry and wet deposition. The model was generally satisfactory at estimating fluxes, except for HpCDD and OCDD, which appeared to be underestimated by about a factor of four. The model output was summarized as 2378-TeCDD toxic equivalent concentrations (TEQs) based on the WHO mammalian 2378-TeCDD toxic equivalent factors (TEFs) [30]. Since HpCDD and OCDD were estimated to contribute only 2% of TEQs, the model was considered to be valid for the purpose intended. 

Predicted individual congener contribution to atmospheric deposition of TEQs in Lake Superior in 1996 is given in Fig. 5. Overall, PCDFs, especially 23478-PnCDF, had a larger contribution than PCDDs. The most toxic congener, 2378-TeCDD, provided about 5% of total TEQs in all of the lakes. Most... 

Hallett and Brooksbank [39] quote an internal Environment Canada report in which water and suspended sediment samples from the Niagara River were sometimes found to contain measurable concentrations of various PCDD/F homologs. PCDD concentrations were < 1.4 pgL-1 in one or two out of six samples, however, five or six samples contained OCDD concentrations up to 3.6pgL-1. TeCDF concentrations were very high in one sample, 156pgL-1 four out of six samples had PnCDF concentrations up to 317 pg L-1. PCDD/Fs were detected in suspended sediments more frequently, up to 2530 pg L-1 of OCDF. TeCDDs were not detected in any sample at unknown detection limits. 

PCDD/Fs were determined in sediments from a harbor near a wood-pre-serving plan in Thunder Bay, Lake Superior, 1988. The plant used pentachloro-phenol [49]. TeCDDs and PnCDDs were below detection, 0.02-0.9 ngg 1 dw. Most important PCDD/Fs were OCDD (< 0.4-980ngg x), HpCDDs (< 0.4-320 ngg x), and OCDF (< 1-400 ngg-1). Lesser concentrations of HxDDs, HxCDFs, and HpCDFs were frequently present (< 0.03-36 ngg ). The contamination was highly associated with oil/grease and PAH concentrations, suggesting a common source. There is no indication from Lake Superior sedi-... 

Aryl Hydrocarbon Receptor, and is the basis of the 2378-TeCDD TEQ additive toxicity model. Concentrations of AHR PCDD/Fs increased an order of magnitude downstream from the confluence of the Tittabawassee River, and increased a further order of magnitude in the lower reaches of the river, presumably because these were depositional zones. 

HpCDF, and 123478-HxCDF. The proportion of 123478-HxCDF increases at the expense of 1234678-FlpCDF downstream from Niagara Falls. The PCDD pattern is much more variable. At Two-Mile Creek, virtually all PCDD contamination was OCDD. At the next four sites, the proportion of 1234678-FlpCDD increased, especially at Pettit Flume. Downstream from Niagara Falls, the proportion of2378-TeCDD jumped to 11 -23% of E-PCDDs. 

Table 4 Early reports of concentrations (ngkg 1 whole fish or fillet) of 2378-TeCDD and 2378-TeCDF in fish from the Great lakes...

Species Area Lake Year Ref. 2378- TeCDD 2378- TeCDF... 

As part of a detailed analysis of lake trout reproductive impairment in Lake Ontario, Cook et al. [16] determined PCDD/F concentrations in lake trout eggs from Lake Ontario, 1978-1991, which are summarized in Table 6. The concentrations are less than one-half of those in lake trout muscle from the same lake and time (Table 5). However, on a lipid weight basis, the egg to female concentration ratio of TeCDD/Fs and PnCDD/Fs was 0.6-0.7, similar to that found in herring gulls [63]. The overall trend in PCDD/F concentrations was similar to that found in lake trout muscle over the same time period, i.e., concentrations of 2378-TeCDD demonstrated the most consistent downward tendency. 

Giesy et al. [66] compared PCDD/F concentrations in dorsal muscle and eggs of coho salmon, chinook salmon and lake trout from Lakes Michigan, Superior, and Huron, 1987 and 1988. Data for the three species were presented as concentrations of homologs plus 2378-TeCDD and 2378-TeCDF. The homolog approach renders comparison of higher chlorinated PCDD/F concen-... 

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