Chemical concentrations in aquatic organisms are of interest not only for learning what may be accumulating in their tissues and potentially causing harm but also for estimating potential threats to other organisms, including birds and humans, who eat the contaminated organisms. Tissue analyses also serve as estimates of the chemical forms and concentrations that are biologically available for uptake. Fish were collected at three sites in early October 2004 for analysis of chemical concentrations. Green sunfish were collected at the Root River near Franklin and Milwaukee River at Milwaukee sites, and creek chubs were collected at the Root River near Franklin and at the Menomonee River at Wauwatosa sites. Three to five fish of a single species were composited for a site and analyzed by the WSLH.

Concentrations of chromium and lead in whole fish were below analytical reporting levels (0.2 and 0.8 µg/g wet weight, respectively) (table 25). Copper concentrations were at least 10 times higher in whole fish from Milwaukee River at Milwaukee and Menomonee River at Wauwatosa than in whole fish from Root River near Franklin. Mercury was detected in whole fish from all three sites at low total mercury⁵ concentrations (0.03–0.12 µg/g wet weight) and was below the USEPA methylmercury criterion of 0.3 µg/g wet weight in fish (U.S. Environmental Protection Agency, 2001).

⁵ Between 95 and 99 percent of the mercury in fish tissue is typically methylmercury (Wiener and Spry, 1996).

Table 25. Summary of chemical analysis of whole fish (composites) at three Phase II stream sites of the Milwaukee Metropolitan Sewerage District Corridor Study, during one-time surveys conducted in October, 2004.

[µg/g, microgram per gram; PCB, polychlorinated biphenyl; all concentrations are in wet weight]

  ^a DDT breakdown products
  ^b Aroclor-1260
  ^c Arochor-1248/1254/1260

The synthetic organic contaminants chlordane and dieldrin were not detected (less than 0.010 micrograms per gram wet weight) in whole fish. DDT breakdown products p-p’-DDE and p-p’-DDD were detected in whole fish from Menomonee River at Wauwatosa, and p-p’-DDE was detected in whole fish from Milwaukee River at Milwaukee; however, concentrations were still less than available guidelines for protection of sensitive fish-eating wildlife. Although the insecticide DDT has not been used in the United States for decades, the breakdown products DDE and DDD are known to be persistent in the environment from historical use. PCBs were not detected in fish from Root River near Franklin (less than 0.040 µg/g wet weight); however, PCBs were found in relatively high concentrations in fish from the Menomonee River site and the Milwaukee River at Milwaukee site. Although manufacture of PCBs ended in 1977, the PCBs found were Aroclors or common mixtures of PCB compounds, indicating that high concentrations persist in stream sediment and accumulate in fish and wildlife. A concentration of 1.5 µg/g wet weight of Aroclors 1248/1254/1260 in whole green sunfish from Milwaukee River at Milwaukee exceeded the New York guideline for the protection of fish-eating wildlife of 0.11 µg/g wet weight for total PCBs (Newell and others, 1987). This indicates that wildlife eating fish from this site could be at risk. The PCB concentration from Milwaukee River fish is similar to that found in whole fish (1.6 µg/g wet weight total PCBs) in 1995 by Scudder and others (1997) and was high compared to concentrations at other sampled sites in the Milwaukee area (Scudder and others, 1997; Steuer and others, 1999); PCB contamination along the main stem of the Milwaukee River may be attributed to the Cedar Creek Superfund alternative site located upstream. Toxicity of specific Aroclor mixtures can vary greatly but the Arochlors detected are considered to be particularly toxic as immunotoxins and carcinogens. Fish consumption is the most common reason for high PCB concentrations in humans. A fish-consumption advisory for PCBs has been in affect at the Milwaukee River at Milwaukee site since 1980 and at the Menomonee River at Wauwatosa site since 1984 (Candy S. Schrank, Wisconsin Department of Natural Resources, written commun., 2006; Wisconsin Department of Natural Resources, 2006).

Comparisons between Phase I and Phase II results for pesticides and PCBs were available for three sites: Milwaukee River at Milwaukee, Menomonee River at Wauwatosa, and Root River near Franklin (appendix 5). Improvement in analytical equipment and techniques for these constituents have allowed for ever-decreasing reporting levels, thereby allowing more low-level concentrations to be detected. This greater analytical sensitivity over time is important to keep in mind when drawing comparisons between Phase I and Phase II data. Many of the Phase I samples below reporting level likely contained pesticides and PCBs at concentrations undetectable by older analytical methods (reporting levels of 0.05 and 0.2 µg/g, respectively), but which might have been detectable using current analytical methods (reporting levels of 0.01 and 0.04 µg/g, respectively).

During Phase I, pesticides in fish tissues were detected only in samples collected from the Lower Milwaukee River subwatershed. During Phase II pesticide concentrations in fish tissues were below the Phase I reporting level at Milwaukee River at Milwaukee, but above the Phase I reporting level at Menomonee River at Wauwatosa. No detections were observed during either Phase at Root River near Franklin.

During Phase I, PCBs were detected only in samples collected from the Lower Milwaukee River subwatershed. During Phase II, PCB concentrations in fish tissues were above the Phase I reporting level at both Milwaukee River at Milwaukee and Menomonee River at Wauwatosa. No detections were observed during either Phase at Root River near Franklin.

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