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() Tribal assessment of dioxin/furan levels in Lake Superior fish.

Hudson, M.1, Groetsch, K.2, 1 Great Lakes Indian Fish and Wildlife Commission, Odanah, WI, United States2 Michigan Department of Community Health, Lansing, MI, United States

ABSTRACT- The Lake Superior Chippewa harvested 1.4 million lbs of whitefish, 264,000 lbs of lean lake trout, 11,000 lbs of siscowet lake trout, and 72,500 lbs of lake herring from Lake Superior in 2003. This fishery constitutes both a source of food and income. A total of 267 commonly harvested fish from three species (lake whitefish, herring, and sturgeon) and two subspecies (lake trout and siscowet trout) were collected from the south shore of Lake Superior between November 1998 and August 1999. Lake whitefish, lake trout and siscowet trout were composited based on length, age, and tissue type (skin, fat, muscle). Lake herring and sturgeon were composited by length and age. All samples were analyzed for 7 dioxin and 10 furan congeners. World Health Organization (WHO) and U.S. Environmental Protection Agency (EPA) toxic equivalency factors (TEF) were used to calculate total toxic equivalency (TEQ) concentrations. Two methods for handling non-detections (ND) were evaluated (zero = ND, detection limit = ND). For those species in which multiple tissue types were analyzed, lipid content of the tissue was highly correlated (r2 = 0.60 to 0.96) with the TEQ concentration within a species. The EPA-TEQ based concentrations using zero for non-detects were the lowest estimates of TEQ content. The WHO-TEQ based concentrations using one-half the detection limit were the highest estimates of TEQ content. The edible portion and untrimmed skin-on (UTSO) fillet TEQ concentrations, regardless of species or TEFs used, were on average below the U.S. FDA commercial dioxin guidance level (25 pg TEQ/g) for fish tissue. The average for UTSO siscowet samples, regardless of the type of TEF used exceeded Michigan's sport fish dioxin guidance value of 10 pg TEQ/g. All other edible tissue and UTSO samples were below Michigan's guidance value. Removing the skin and trimming the dorsal and ventral fatty tissue from the whitefish, lake trout, and siscowet trout fillets resulted in reducing, on average, the edible tissue (i.e., trimmed, skin-off fillets) TEQ concentrations by 43 to 68 percent.

Key words: lake superior fish, dioxin/furan, lake superior chippewa, toxic equivalency concentrations

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