MERCURY CONTAMINATION STANDARDS 259 



1 to 17 mg Hg/kg wet weight suggest to some health authorities that 

 the currently accepted level in the United States [0.5 mg Hg/kg wet 

 weight (500 /ng/kg)] does not have an appreciable level of safety for 

 pregnant women (Establier, 1975b; Peakall and Lovett, 1972; 

 Skerfving, Hansson, and Lindstem, 1970). In Sweden, the official 

 limit for mercury in fish is 1.0 mg/kg wet flesh. Human risk in 

 consumption of mercury-contaminated fish within this guideline is 

 considered negligible in that country (Berglund and Berlin, 1969); 

 however, some Scandinavian scientists recommend that fish con- 

 sumption should be limited to one meal a week (Lofroth, 1970). 



Selected Studies 



Mercury retention by teleost species is variable. In one study, 

 when northern pike from a lake that was heavily contaminated with 

 mercury were transplanted to waters relatively free of mercury, only 

 30% of the mercury in their muscle was eliminated in 1 year 

 (Lockhart et al., 1972). A study by Amend (1970) of juvenile sockeye 

 salmon indicated that fish treated repeatedly with mercurials during 

 their freshwater phase accumulated and retained high levels of 

 mercury for several months, but, after 4 years at sea, the returning 

 salmon contained normal levels of mercury in all tissues examined. 



A number of investigators report that mercury from point-source 

 discharges, including sewer outfalls and chloi^alkali plants, was 

 taken up by sediments; sediment levels were eventually reflected by 

 an increased mercury content of epibenthic fauna (Dehlinger et al., 

 1973; Hoggins and Brooks, 1973; Klein and Goldberg, 1970; 

 Klemmer, Luoma, and Lau, 1973; Parsons, Bawden, and Heath, 

 1973; Takevchi, 1972). Analysis of the effluent from the Hyperion 

 sewer outfall in Los Angeles showed a mercury content slightly 

 below 1 /jg/liter (Klein and Goldberg, 1970). Concentrations of 

 mercury in sediments near this outfall were as high as 820 jug/kg but 

 decreased with increasing distance from the outfall; mercury levels in 

 epibenthic fauna, including crabs, whelks, and scallops, were also 

 highest near the discharge and lowest tens of kilometers away. 



A mercury budget for estuaries along the Georgia coast indicates 

 that the dominant salt-marsh plant, Spartina alterniflora, exerts a 

 strong control on mercury migration (Gardner et al., 1975;Windom 

 et al., 1976; Windom, 1973). Mercury entered the estuary primarily 

 in solution, delivering ~1.5 mg annually to each square meter of salt 

 marsh. Annual uptake of mercury by S. alterniflora alone was about 

 0.7 mg/m^ salt marsh. Mangrove vegetation plays a similarly im- 

 portant role in mercury cycling in the Florida everglades (Lindberg 

 and Harriss, 1974; Tripp and Harriss, 1976). 



