observed variations are not known, but may be associated with localized inputs 

 from municipal sewage treatment plants (Lamparski et al. 1984) and with 

 atmospheric transport of incinerated domestic and industrial chemical wastes 

 (Czuczwa et al. 1984). For example, the PCDD composition of sewage sludge 

 from Milwaukee, Wisconsin, was relatively constant, as judged by analysis of 

 samples from 1933, 1981, and 1982 (Lamparski et al . 1984). Total PCDD content 

 in these samples ranged between 60,950 and 70,191 ppt, of which the great 

 majority was in the form of octa-CDDs (82-86%), hepta-CDDs (11.0-15.4%), and 

 hexa-CDDs (1.3-2.1%). However, the tetra-CDDs increased from 34 ppt in 1933, 

 to 138 in 1981, and to 222 in 1981; corresponding values for the 2,3,7,8-TCDD 

 isomer in 1933, 1981, and 1982 were 2.2, 11.0, and 16.0 ppt, respectively. 

 Other TCDD isomers also showed increases from 6 ppt in 1933 to 22 ppt in 1982 

 (1,3,7,8-TCDD), and during that same period from 2.2 ppt to 140 ppt (1,2,3,7-, 

 and 1,2,3,8-TCDD). It seems that chlorinated dibenzodioxins have been present 

 in dried sludge from this plant for at least 50 years. Their presence in this 

 material suggests that they may have been formed by the condensation of 

 chlorophenols resulting from the chlorination of naturally occurring phenolic 

 compounds (Lamparski et al . 1984). PCDDs were also found in sediments from 

 Siskiwit Lake on Isle Royale in Lake Superior, a location which can receive 

 only atmospheric inputs. The source of these compounds is the atmospheric 

 transport of dioxins formed by combustion of domestic and chemical wastes. 

 For example, particulates from a chemical waste incinerator in Midland, 

 Michigan had 260,000,000 ppt of octa-CDDs and 170,000,000 ppt of hepta-CDDs; 

 lower, but still elevated levels of 440,000 ppt of octa-CDDs and 310,000 ppt 

 of hepta-CDDs were measured in municipal trash incinerator particulates 

 (Czuczwa et al. 1984). 



Data are limited on 2,3,7,8-TCDD concentrations in field collections of 

 biological and other materials (Table 3). In the Great Lakes area, fish from 

 the Tittabawasee and Saginaw Rivers, two tributaries of Lake Huron's Saginaw 

 Bay, contained up to 695 ppt of 2,3,7,8-TCDD (Stolzenburg and Sullivan 1983). 

 High 2,3,7,8-TCDD levels (87 to 162 ppt) were also recorded in fish from the 

 Niagara River, New York, and from parts of Lake Ontario; lower concentrations 

 (2 to 28 ppt) were noted in fish from Lakes Erie, Huron, Michigan, and 

 Superior (Stolzenburg and Sullivan 1983). Muscle from larger specimens of 

 commercial fish collected from Lake Ontario in 1980 had higher levels of 

 2,3,7,8-TCDD than smaller fish (Ryan et al . 1984), suggesting that 

 accumulation increases with age. The larger fish also contained high 

 concentrations (1.2 to 4.9 parts per million, fresh weight) of polychlorinated 

 biphenyls (Ryan et al. 1984), demonstrating a need to elucidate TCDD 

 interaction kinetics with other contaminants. Bottom-feeding fish, such as 

 carp and catfish, from rivers in Michigan during 1978, contained higher 

 2,3,7,8-TCDD residues than surface feeders (Harless et al . 1982), indicating 

 an association with contaminated sediments. Sediments from the Spring River, 

 Missouri, contained 12 ppt of 2,3,7,8-TCDD immediately downstream of a now 

 defunct hexachlorophene facility (Kleopfer and Zirschky 1983); concentrations 

 in fish were measurable 111 km downstream from this disposal site (Table 3). 

 Fish from the Spring River (and also the Meremac River, Missouri) contained 

 inordinately high levels of 18 to 78 ppt of 2,3,7,8-TCDD, prompting the U.S. 

 Food and Drug Administration to issue a health advisory in 1982 against fish 



