BACKGROUND CONCENTRATIONS 



Data are accumulating that indicate many PCDDs, in addition to 

 2,3,7,8-TCDD, are present in biological and abiotic samples (NRCC 1981; 

 O'Keefe et al . 1983; Petty et al. 1983; Stalling et al . 1983; Czuczwa et al . 

 1984; Lamparski et al. 1984; Kamrin and Rodgers 1985; Stalling et al. 1985a). 

 In general, wherever high levels of dioxins have been detected in the 

 environment, a local application of TCDD-contaminated herbicide, hazardous 

 waste site, or industrial discharge has usually been implicated as the source 

 (Stolzenburg and Sullivan 1983). At Eglin Air Force Base (EAFB), located in 

 northwestern Florida, contamination of a 208 hectare section with 2.778 kg of 

 2,3,7,8-TCDD (equivalent to 13 mg/ha) occurred between 1962 and 1970 as a 

 result of repeated, massive herbicide applications (Young and Cockerham 

 1985). The 2,3,7,8-TCDD isomer was present as an impurity in 76,740 kg of 

 2,4-D and 73,010 kg of 2,4,5-T applied to this section of EAFB during the 

 9-year span. Ecological surveys conducted between 1970 and 1975 showed an 

 apparently healthy and diverse wildlife fauna, although soil levels of 520 ppt 

 of 2,3,7,8-TCDD were frequently encountered, and 2,3,7,8-TCDD residues were 

 elevated in some species examined. The highest residues recorded in various 

 trophic levels were 283 ppt in whole beetle grubs, up to 1,360 ppt in whole 

 southern toads ( Bufo terrestris ), 360 ppt in viscera and 430 ppt in carcass of 

 a lizard, the six-lined racerunner ( Cnemidophorus sexlineatus ), 18 ppt in 

 gonad and 85 ppt in gut contents of the spotted sunfish ( Lepomis " punctatus ), 

 100 to 1,200 ppt in stomach contents of the southern meadowlark ( Sturnella 

 magna argutula), and 300 to 2,900 ppt in liver and 130 to 200 ppt in pelt of a 

 beachmouse ( T^eromyscus polionotus ) (Young and Cockerham 1985). The 

 significance of these elevated residues will be discussed later. 



In some cases, 2,3,7,8-TCDD has constituted up to 95% of the total body 

 PCDD burden, as was true in lake trout, Salvelinus namaycush (O'Keefe et al . 

 1983), and rainbow trout, Sal mo gairdneri (Fetty et al . 1983) from Lake 

 Ontario. Concentrations of 2,3,7,8-TCDD fn whole carp ( Cyprinus carpio ), 

 varied from 24% of total body PCDDs in Saginaw Bay, Michigan (Stalling et al. 

 1983), to 45 to 56% in the Niagara River (NRCC 1981). In herring gulls from 

 Saginaw Bay, 2,3,7,8-TCDD comprised 40 to 60% of the whole body PCDD content 

 (NRCC 1981; Petty et al. 1983), and 72 to 78% in gulls from Lakes Huron and 

 Ontario (Stalling et al. 1983, 1985a). In 1983, Forster's tern ( Sterna 

 forsteri ) from Green Bay, Wisconsin, contained 114 ppt of PCDDs in eggl of 

 which Tl% was 2,3,7,8-TCDD; double-crested cormorants ( Phalacrocorax auritus ) 

 from the same area contained 25 to 214 ppt of PCDDs in whole body, ^oT which 

 only 10 to 31% was 2,3,7,8-TCDD (Stalling et al . 1985a). The causes of the 



