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Library: Letters: EPA | |||||||||||||||
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY December 3, 1997 MEMORANDUM SUBJECT: Ecological Risk Evaluation for Clear Creek Bloomington, IN FROM: Mark D. Sprenger, Ph.D. TO: Tom Alcamo, RPM As you are aware the function of a baseline ecological risk assessment (within the CERCLA process) is to establish the need and appropriateness of risk management options in the FS. In addition, the ecological risk assessment (ERA) is the means by which the degree of risk reduction is evaluated within the nine criteria for remedy selection. Unfortunately, a complete and accepted ecological risk assessment does not exist on Clear Creek. This situation is a result of the effort to develop consensus on the risk assessment parameters with the responsible party (as opposed to EPA dictating the process); to the best of my knowledge this consensus has not been achieved. Because of this situation, what I can provide to you is an evaluation of ecological risk based upon EPA - OERR nationally accepted base ecological parameters. One of the Assessment Endpoints which have been identified for Clear Creek is a "sustainable mammalian fish consuming populations". The question (Testable Hypothesis) relative to this assessment endpoint is: are fish tissue PCB levels such that adverse effects may occur in fish consuming mammals utilizing Clear Creek? ~The means of evaluation of this question and thereby the assessment endpoint is the use of a food chain exposure model and a hazard quotient comparing Clear Creek exposure estimates with literature exposure/effects studies. The "default" baseline ecological risk food chain model parameters for a river otter exposure model are attached; These model parameters are conservative. In the case of the studies used for the generation of the toxicity information on PCBs with mink; the toxicity benchmarks from these studies is equal to the concentration of PCBs in an organisms food which results in a hazard quotient of 1. During August 1997, the field effort which was conducted through the Environmental Response Team Center (ERT), in con~unction with the Region V ecological risk assessor and the U.S. Fish and Wildlife Service, it was noted that river otter are currently utilizing Clear Creek as evidenced by tracks observed along the creek. While otter have not been tested directly for PGB adverse effect, their family member (Mustelidae) the mink has been used in the evaluation of PCB effects. A more detailed summary of the toxicity of PCBs to otter is attached, however, the summary of this information is that in Superfund ecological risk assessments, we assume that otter are as sensitive to PCB effects as mink. The rationale for this is based upon inferences from field reports on otter and corresponding PCB exposure; and the close taxonomic and physiological relationship between otter and mink. Based upon the discussion above, the toxicity benchmarks of a no observable adverse effect level (NOAEL), low observable effect level (LOAEL) and mortality translate to a food concentration of O.l mg/kg, 0.13 mg/kg and 3.3 mg/kg PCBs respectively. In other words, if the fish from Clear Creek had less than 0.1 mg/kg PCBs, we would conclude that there is no substantial risk. If the fish contained between 0.1 and 0.13 mg/kg we would conclude that a potential for risk exists and that additional evaluation may be warranted. If the fish contain between 0.13 and 3.3 mg/kg PCBs would could that there is a risk and that adverse impacts may be occurring. Lastly, if fish concentrations are above 3.3 mg/kg there is a risk and adverse effects are likely to have occurred and are occurring. The last round of fish tissue data collected (by Westinghouse) for PCB analyses suggests that creek chub (a major food item for wildlife) range between 0.4 to 42 mg/kg PCBs and green sunfish range between 0.6 and 12 mg/kg; indeed few whole fish samples contained less than I mg/kg PCBs. It must be pointed out these data are in the process of being evaluated for acceptibility to EPA. Additionally, the fish sampling effort conducted through the ERT was directed at potential for dioxins to be present in Clear Creek. The results of that effort confirm that dioxins, including 2,3,7,8 TCDD are present in the fish from Clear Creek. Also, the data suggest that a source of dioxins exist at or above the Winston-Thomas treatment plant. The potential ecological risk from the dioxins present in the fish from Clear Creek has not been evaluated. However, the possibility of additional risk from the dioxins and additive risk with the PCBs needs to be evaluated. While this discussion does not constitute an ERA, it is evident that ecological risks do exist to wildlife which utilize Clear Creek. In addition, concentrations of PCBs in fish are in the range where a high potential exists for historical, as well as, current adverse risk to wildlife. It is clear from the existing data on the Clear Creek system that source control is a vital component of reducing the risks in the system. |
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