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Library: Letters: EPA | |||||||||||||||
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY March 16, 1998
Subject- Evaluation of Bloomington Fish Data From: J. Milton Clark, Ph.D. To: Thomas Alcamo Evaluation of recent data for PCBs, dioxins, and dibenzofurans from whole fish and fish fillets collected below Lemon Lane landfill show that PCBs dominate the chemical contamination and resulting risks to human health and wildlife. We would anticipate the same findings for soils in and around Lemon Lane. Actual analytical results are attached. The key tables for evaluation are tables 2.3 and 4.2. The maximum toxic equivalency factor (TEF) for dioxins and dibenzofurans found in whole fish was 5 ppt, while PCBs levels were 400,000 times higher at about 2 ppm (1.9 ppm for a spotted sucker) in edible fish (fillets). The ratio of dioxin toxicity to PCB toxicity using cancer potency values, respectively, of 1.56E-5 (mg/kg-bw-day)-l and 2.0 (mg/kg-bw-day)-I is 75,000. The total dioxin and dibenzofuran TEFs need to be five times higher in fish before they reach the risk levels derived for PCBs. It should be noted that the comparison is worst case, as whole fish PCB data was not available. National surveys show that whole fish have about twice the contaminant levels as fish fillets. Therefore, about ten times the amounts of dioxin and dibenzofurans, as TEFs, would be needed before they equaled the cancer risks from PCBs. In regards to noncancer (e.g., reproductive and immune risks) a ratio of 20,000 is found between the PCB reference dose of 2E-5 mg/kg-bw-day as compared that for dioxin of 1E-9 mg/kg-bw-day. Therefore, concentration levels for the dioxin and dibenzoffirans would need to be at least 20 fold greater to match those non-cancer risks from PCBs. These findings are not unexpected. PCBs dominate human health cancer and non-cancer risks, unless where fires have occurred which can generate dibenzofurans and dioxin, the later when chlorobenzenes or related compounds are present. Some questions have been raised regarding the need to test for dioxin like PCBs. U.S. EPA has not rendered a policy decision regarding testing for these compounds and interpeting the results. Because dioxin like PCBs are part of the total PCBs tested in animals, creating a separate risk from dioxin like PCBs and then adding it to that calculated for total PCBs, would be double counting the risks. Public health decisions regarding contaminants in Bloomington fish can be made by only considering the risks from PCBs. Similar conclusions regarding wildlife were made in the attached December 3, 1997 analysis. As discussed in the December 5, 1997 analysis and 1/21/98 analysis U.S. EPA and the Indiana Department of Public Health have significant human health and analysis U.S. EPA and the Indiana Department of Public Health have significant human health and ecological concerns regarding the PCB levels present in fish collected in the vicinity of Bloomington PCB sites. See attachments. The unacceptably elevated PCB levels are the result of ongoing water discharges and exposures to PCB contaminated sediments. Attachments |
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