Two 9‐month continuous‐flow bioassays and several intermediate length continuous‐flow tests were conducted to determine safe levels of Aroclor 1242, 1248, and 1254 for the fathead minnow (Pimephales promelas) and Aroclor 1248 for the flagfish, Jordanella floridae. Calculated 96‐hr LC50 values for newly hatched fathead minnows were 7.7 μg/liter for Aroclor 1254 and 15 μg/liter for 1242. Three‐month‐old fatheads had a 96‐hr LC50 of 300 μg/liter for 1242. Reproduction occurred at and below 1.8 μg/liter 1254 and at and below 5.4 μg/liter 1242. Newly hatched young were the most sensitive life stage. Growth of young fatheads was also affected above 2.2 μg/liter 1248, and none survived above 5.1 μg/liter after 30 days. Young flagfish did not survive at 1248 concentrations above 5.1 μg/liter and did not grow well above 2.2 μg/liter.
Tissue residues in fathead minnows ranged from 0.7 μ/g 1248 in control fish to 1036 μ/g 1254 in fish held for 8 months in water containing 4.6 μg/liter 1254.
Fish from western Lake Superior (1972-73) contained DDT and PCB residues at concentrations greater than o.1 ppm. The most predominant PCB's were those containing 3 to 6 chlorine atoms per molecule, and GLC data indicated that the mixtures were most like the commercial product Aroclor 1254(2). Other chlorinated contiminants identified by GC/MS analyses and occurring at concentrations less than 0.1 ppm were hexachlorobenzene (C6Cl6), chlordane, nonaclor, and dieldrin. Lindane, which has been previously reported in Lake Superior, was below the detection limit of approximately 0.01 ppm. The relationship between the size of lake trout and the concentration of total DDT in the fish was compared to measurements reported in previous studies. The comparison suggests that DDT residues have declined since 1968. The concentration of PCBs was estimated to be 0.8 ng/L in Lake Superior water and 0.1 ppm in large zooplankton. The apparent bioconcentration factor for PCBs in Lake Superior fish ranged from 10(5) to 10(6). The concentration of total DDT and PCBs in the larger Lake Superior fish exceeded the 5 ppm tolerance level established by the U.S. Food and Drug Administration for these chemicals in fish tbe used for human consumption.
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