41-1 



Human liitliicnccs— Our Living Resources 



Fig. 2. Mean concentrations of 

 DDT and its primal^ metaholites, 

 DDEaiidDDD(TDE^ 

 dichlorodiplienyldichloroethanel, 

 and of total polychlonnated 

 biphenyls (PCBsl. in fish,1970-86. 

 Also shown are the estimated 

 number of bald eagle pairs in the 

 conterminous United States during 

 the same period (Federal Register 

 14Q4). 



I I <010ppm 



r~l 010-018ppm 



□ 19-0 56ppm 



■ 0.57 - 68 ppm 



I I >2 4 ppm • Collection sites 



Fig. 3. Geographic distribution of 

 DDE residues in starlings collect- 

 ed in 1985. Also shown are bound- 

 aries of the 5-degree (latitude and 

 longitude) sampling blocks and 

 collection sites. 



(decline (Schmitt et al. 1990). Concentrations of 

 toxaphene, an insecticide that replacetJ DDT in 

 cotton farming and many other applications, 

 have also declined in fish since 1980. when its 

 registration was canceled (Schmitt et al. 1990). 

 Toxaphene does not accumulate in birds and 

 was not measured in either starling or duck- 

 wing samples. 



Polychlorinated biphenyls (PCBsl are also 

 complex mixtures of chemicals. Compiising as 

 many as 209 different compounds, various PCB 

 formulations were used historically as lubri- 

 cants, hydraulic fluids, and fire retardants; as 

 heat transfer agents in electrical equipment, 

 including fluorescent light ballasts; and as a 

 component of carbonless copy papers. Much 

 like DDT, many PCBs are persistent and toxic. 

 Large quantities were discharged directly to 

 waterways, including Lakes Michigan and 

 Ontario and the Hudson, Mississippi, Kanawha, 

 and Ohio rivers. PCBs are also often present in 

 landfills and urban runoft". These discharge and 



disposal patterns are reflected in the geographic 

 trends evident for PCBs in fish and wildlife; 

 greatest concentrations generally occur in the 

 urban-industrial regions of the Midwest and 

 Northeast (Fig. 4). By 1980, the direct dis- 

 charge of PCBs to waterways had been greatly 

 restricted, and total PCB concentrations gener- 

 ally declined in U.S. fish and wildlife (Bunck et 

 al. 1987; Schmitt et al. 1990). Residual PCBs 

 nevertheless remain a problem in some areas, as 

 evidenced by human consumption advisories in 

 effect for fish from the Great Lakes, Lake 

 Champlain, the Hudson River, and elsewhere. 



Some highly toxic PCBs are long-lived and 

 are selectively accumulated by aquafic organ- 

 isms. Fish samples collected in 1988 from some 

 regions, especially the Great Lakes, still con- 

 tained toxic PCBs at concentrations great 

 enough to be harmful to fish-eating birds (C.J. 

 Schmitt, National Biological Service, unpub- 

 lished data, 1993). Indeed, PCBs and other con- 

 taminants in Great Lakes fish are believed to 

 limit the reproduction of bald eagles and other 

 fish-eating birds, mink (Mustela vison). and 

 river otters {Liitni caiuidensis) in coastal areas 

 of the Great Lakes (Wren 1991; Giesy et al. 

 1994). PCBs, along with DDE and other con- 

 taminants, including chlorinated dioxins, may 

 also be involved in the failure of lake trout 

 {Salvelinus luwuixciish) to reproduce naturally 

 in Lake Michigan (USFWS 1981; Spitsbergen 

 et al. 1991). In spite of discharge restrictions, 

 the concentrations of PCBs and chemically sim- 

 ilar compounds in the Great Lakes will likely 

 remain elevated because of atmospheric trans- 

 port and the internal cycling of contaminants 

 already present in the lakes. 



The primary sources of mercury to U.S. 

 waters were discharges from chemical facilities 

 that manufactured caustic soda (sodium hydrox- 

 ide). These discharges have been regulated 

 since the 1970"s. Other historical sources 

 included paper mills, gold and silver mines, and 

 the production and use of mercury-containing 

 pesticides. Concentrations of mercury in fish 

 declined significanfly from 1969 through 1974 

 as a result of restrictions on these historical 

 uses, but concentrations have not changed 

 appreciably since 1974. Concentrations in fish 

 from heavily contaminated waters, such as Lake 

 St. Clair, declined the most (Schmitt and 

 Brumbaugh 1990). Despite these declines, fish 

 consumption advisories remain in effect for 

 some waters. Recent findings have highlighted 

 the importance of atmospheric transport and the 

 accumulation of mercury in natural sinks, such 

 as Lake Champlain (e.g., Driscoll et al. 1994) 

 and the Everglades, in the maintenance of ele- 

 vated concentrations (Zillioux et al. 1993). 



Lead concentrations in fish declined from 

 1976 to 1986 (Schmitt and Brumbaugh 1990), 



