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HAZARD OF INORGANICS TO ENDANGERED FISH .. sidering that three endangered fish are of concern and that the Endangered Species Act essentially requires a degree of confidence approaching 100% that endangered species will not be adversely affected. To evaluate the hazard of the inorganic chemicals tested, the margin of uncertainty was calculated by com- paring acute toxicity values with the maximum concen- trations of boron, selenium, uranium, vanadium, and zinc in three waters sampled as part of the DOl reconnais- Inorganic sance investigation of the middle Green River (Stephens et al., 1988; Table 3). Information on lithium was not available. When using the geometric mean of the 96-hr LCso val- ues for all species and life stages tested as the BEC, the margins of uncertainty ranged from 129 for selenium as selenite to 32,333 for selenium as selenate (Table 4). Al- though using the geometric mean for all species and life stages tested might be acceptable when considering n~nthreatened or nonendangered species, it is not appro- pnate for endangered species, which require a higher level of protection. Thus, a more conservative approach necessary to protect endangered species would be to use t~e 96-hr LCso values for the most sensitive species and hfe stages as the BEC. The margins of uncertainty were lower and ranged from 42 for zinc to 8333 for selenium as selenate (Table 5). If only waterborne inorganic concentrations were con- sidered in the Green River as the EEC, then selenite and zinc would be of concern relative to the most sensitive species and life stage. However, larval razorback sucker and Colorado squawfish utilize backwaters and embay- ments, including the mouths of tributaries and down- stream littoral areas. Consequently, they could be ex- posed in the mouth of Ashley Creek and downstream of it, with the resulting margins of uncertainty for the most sensitive species and life stage of less than 100 for zinc and close to the 100 for selenite, selenate, and boron (Table 5). Thus, these inorganics are a moderate to high hazard to the species tested. Vanadium and uranium do not seem to be waterborne hazards to the fish tested; the hazard for lithium is unknown. TABLE 3 Maximum Inorganic Concentrations (....glIiter) in Three Water Samples as Part of the DOl Reconnaissance Investigation of the Middle Green River in 1986-1987 r rrigation Ashley Creek Green Inorganic project drains (Green River tributary) River Boron 1200 630 80 Selenium 140 73 3 Uranium 73 33 Zinc 40 20 10 Vanadium 5 2 139 TABLE 4 Margin of Uncertainitya Ratios Using the Geomet~c Mean of the 96-hr LCso Values for All Species and Life Stages Tested as the Biological Effect Concentration (BEC), and the Maximum inor- ganic Concentrations Reported in the DOl Reconnaissance inves- tigation of the Middle Green River as the Expected Environmental Concentration (EEC) Irrigation project drains Ashley Creek (Green River tributary) 247 330 535 1,394 1,329 2,300 Green River Selenite Zinc Boron Uranium Selenate Vanadium 129 165 281 630 693 920 6,000 660 4,212 32,333 a BEC/EEC. The concentrations of selenium in irrigation drains and Ashley Creek (Table 3) are substantially higher than the national water quality criterion for the protection of aquatic life: the 4-day average concentration not to ex- ceed 5 /J-g/liter or the I-hr average not to exceed 20 /J-g/ liter-more than once every 3 years on the average (USEPA, 1986). The concentrations of zinc in all three waters is below the national water quality criterion for the protection of aquatic life: the 4-day average not to exceed 110 /J-g/liter at a hardness oflOO mg/liter more than once every 3 years (USEPA, '1986). There are no national water quality for boron, lithium, uranium, or vanadium. The national criteria for selenium and zinc are substantially lower than the 96-hr LCso values for the three species tested and thus would be protective for these endangered fish. The potential hazard of waterborne exposure of indi- vidual inorganics to endangered fish tested should be in- terpreted with caution because fish would be inseparably - TABLE 5 Margin of Uncertainitya Ratios Using the 96-hr LCso for the Most Sensitive Species and Life Stage as the Biological Effect Concentration (BEC), and the Maximum Inorganic Concentra- tions Reported in the DOl Reconnaissance Investigation of the Middle Green River as the Expected Environmental Concentra- tion (EEC) Irrigation Ashley Creek Green Inorganic project drains (Green River tributary) River Zinc 42 85 170 Selenite 64 122 2967 Selenate 179 342 8333 Boron ]94 370 2912 Vanadium 440 1100 Uranium 630 1394 a BECfEEC.