Approach for Qualitatively Evaluating the Potential Impact of Tentatively Identified Compounds (TICS) at Contaminated Sites. T. C. Marshall, PTRL Environmental Services, 1942 Oak Ridge Turnpike, Oak Ridge, TN 37830; and M. Maddaloni, USEPA Region II, 290 Broadway, New York, NY 10007
The USEPA Risk Assessment Guidance on TICs states that TICs should be evaluated if they are present in large numbers relative to the detected chemicals on the Target Analyte/Target Compound list, or if TIC concentrations appear to be high relative to the other chemicals detected. The preferred method for evaluating TICs is to use special analytical procedures to confirm the identity and concentration of TICs prior to conducting the risk assessment. When this is not practical, the TICs are to be included as chemicals of potential concern, but no approaches for assessment are provided in existing guidance. An approach to evaluating the potential environmental impact of TICs was developed for a Superfund site in the USEPA Region II. The approach is qualitative since both the identity and concentrations of TICs are highly uncertain. Only TICs with explicit Chemical Abstract Services Registration Numbers and a 5% or greater frequency of detection are evaluated. The TICs are segregated by their presence in surficial and subsurface soil. A screen was developed to determine which TICs have positive data as to the potential for carcinogenicity, mutagenicity, or teratogenicity. A categorization matrix was developed for TICs using the toxicity data combined with concentration cut-offs of 1 ppm and 10 ppm or greater. Those chemicals that are possible carcinogens, mutagens, or teratogens and exceed 1 ppm in soil and the others that exceed 10 ppm are qualitatively evaluated in the risk assessment during the discussion of uncertainties.