Characterization of Tentatively-Identified Compounds (TICs) and Data Usage Issues
Marilyn Hoyt,AMEC Earth and Environmental, Westford, MA
Barbara Pugh, AMEC Earth and Environmental, Westford, MA
Marie Wojtas, AMEC Earth and Environmental, Westford, MA

Avoiding Overestimates of Chlordane and PCBs as Co-Contaminants by Methods 8081/8082
Dean Gouveia, ICF Consulting, Lexington, MA
Mary O’Connell Kozik, ICF Consulting, Lexington, MA
Andy Beliveau, EPA OSRR, Boston, MA
Peter Kane, Woods Hole Group Environmental Laboratories, Raynham, MA

Characterization of Tentatively-Identified Compounds (TICs) and Data Usage Issues

Marilyn Hoyt, AMEC Earth and Environmental, 239 Littleton Road, Suite 1B, Westford, MA 01886, Tel:  978-692-9090, Fax:  978-692-6633, Email:  marilyn.hoyt@amec.com
Barbara Pugh, AMEC Earth and Environmental, 239 Littleton Road, Suite 1B, Westford, MA 01886, Tel:  978-692-9090, Fax:  978-692-6633, Email:  barbara.pugh@amec.com
Marie Wojtas, AMEC Earth and Environmental, 239 Littleton Road, Suite 1B, Westford, MA 01886, Tel:  978-692-9090, Fax:  978-692-6633, Email:  marie.wojtas@amec.com  

Analyses by mass spectrometry provide the opportunity to identify a wide range of organic chemicals in environmental samples.  Mass spectra for non-target peaks are compared via a computerized search routine against the spectra in the NIST/EPA/NIH database.  If a reasonable match is found, the compound is tentatively identified and its concentration estimated. If no match is found, the compound is reported as “Unknown”. 

Once TICs are reported, there are no consistent guidelines for how the information should be interpreted and used.  For many of these compounds, information regarding fate and transport properties and toxicity is limited or unavailable.  A clear understanding of the nature of the TICs and their possible relation to site activities or compounds of concern is necessary before decisions can be made on whether they should be added as target analytes or included in risk evaluations.

TICs have been reported in approximately 30% of the soil and 14% of the water samples collected at the Massachusetts Military Reservation.  Over 600 individual chemicals or groups have been reported more than once in soils as TICs. While groundwater samples typically have no or very few TICs detected, over 100 different compounds have been tentatively identified more than once.  TICs reported at the site have been categorized by their potential sources.  Hydrocarbons and natural plant chemicals account for a high percentage of the TICs; other categories include organics from commonly used products, potential munition constituents and their degradation products, anthropogenic background compounds and analytical artifacts.

TIC data have been used in some instances to modify the analytical program at MMR. The decision to dismiss or incorporate TIC data into human and ecological risk assessments has the potential for overestimating or underestimating total site risk.  The potential contribution of TICs on the uncertainty of the risk estimates is discussed.

Avoiding Overestimates of Chlordane and PCBs as Co-Contaminants by Methods 8081/8082

Dean Gouveia, Senior Chemist, ICF Consulting, 33 Hayden Avenue, Lexington, MA 02421, Tel: 781-676-4040, Fax: 781-676-4005, Email: dgouveia@icfconsulting.com
Mary O’Connell Kozik, Senior Chemist, ICF Consulting, 33 Hayden Avenue, Lexington, MA 02421, Tel: 781-676-4049, Fax: 781-676-4005, Email: mkozik@icfconsulting.com
Andy Beliveau, Environmental Scientist, Technical Assistance Section, EPA OSRR, 1 Congress Street, Boston, MA 02114, Tel: 617-918-1443, Email: Beliveau.Andy@epamail.epa.gov
Peter Kane, Laboratory Director, Woods Hole Group Environmental Laboratories, 375 Paramount Drive, Suite 2, Raynham, MA 02767, Tel: 508-822-9300, Fax: 508-822-3288, Email: pkane@whgrp.com

Analysis of soils and sediments for chlordane and polychlorinated biphenyls (PCBs) by SW-846 Methods 8081/8082 is common. Interest in these persistent organic pollutants (POPs) has  increased due to recent risk estimates, focus on POPs bioaccumulation, and application of risk based benchmark screening and action levels. Although the Method 8081/8082 electron capture detector (ECD) offers high sensitivity, the detector’s non-specific nature introduces problems of definitive identification and accurate quantitation when multiple compounds of interest or interferences are present. Another difficulty introduced is that the multicomponent species are typically regulated (total PCBs and technical chlordane) although Methods 8081/8082 focus on Aroclors and the alpha and gamma chlordane components of technical chlordane. Recent studies have confirmed that other components and breakdown products of technical chlordane present comparable or higher risk than alpha- and gamma- chlordane.  

In a recent Massachusetts military facility preliminary investigation, soil results were reported at or above Region 9 Residential PRGs and/or Massachusetts S-1 criteria by Methods 8081/8082. Data validation identified issues of identification and quantitation inaccuracy where co-contaminants including chlorinated pesticides, technical chlordane, and weathered PCB Aroclors may be present. The nature of the nonspecific detector and quantitation according to Methods 8081/8082 led to uncertain identification and apparent overestimated concentrations. Analytical options were explored to more definitively identify and quantitate chlordane components and PCBs. GC/MS selected-ion-monitoring (SIM) by modified Method 680 was selected for PCB congeners/homologs and major technical chlordane components (alpha-and gamma- chlordane, cis- and trans- nonachlor, and heptachlor) and breakdown products (heptachlor epoxide and oxychlordane). Initial test results confirm that Methods 8081/8082 overestimated concentration and did not provide a complete perspective to evaluate the data. Understanding the method limitations and cost-effective alternatives is necessary before evaluating any site especially where the method bias can inappropriately indicate action based on low risk based screening or action levels.

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