Good Practices When Handling Fish Tissue to Avoid Data Reliability Issues: Results from Sample Wrapping and Holding Time Studies

Ensuring Reliable Data
Oral Presentation

Prepared by H. McCarty1, J. Healey2, B. Snyder3, T. Cohen3
1 - General Dynamics Information Technology, 3170 Fairview Park Drive, Falls Church, VA, 22042, United States
2 - USEPA Office of Water, 1200 Pennsylvania Ave., N.W., Washington, DC, 20460, United States
3 - Tetra Tech, Inc., 10711 Red Run Blvd., Suite 105, Owings Mills, MD, 21117, United States


Contact Information: [email protected]; 703-254-0093

ABSTRACT

Fish tissue contaminant studies require careful sample handling and storage to reduce the chance of cross-contamination and maintain the integrity and quality of samples. Beginning with the 2000-2004 National Lake Fish Tissue Study, EPA required study partners (including state or Tribal monitoring teams) to wrap fish specimens in solvent-rinsed aluminum foil before packing the samples in a food-grade polyethylene bag and freezing them until they could be prepared for analysis. Solvent rinsing of the foil proved to be costly; however, EPA was concerned that some analytes being measured in fish might have also been used as lubricants during the aluminum foil manufacturing process and could cross-contaminate samples if the foil was not solvent-rinsed. EPA has also recommended that fish tissue samples be analyzed within 28 days for mercury and within one year for all other contaminants. However, the efficacy of wrapping fish in solvent-rinsed foil to reduce cross-contamination, and the question of whether target analyte residues in frozen fish tissue can remain stable and yield reliable results after extended holding times have not been formally evaluated. To address this, two studies were conducted: one to explore whether “untreated” heavy-duty food grade aluminum foil can be used instead of solvent-rinsed foil when wrapping fish in the field, and another to reanalyze stored fish tissue samples of commonly collected species from past EPA studies. The reanalyzed samples represent six incremental holding times, between 3 and 20 years each, and have been analyzed for mercury, PCBs and PFAS, to compare tissue contaminant levels after long-term storage with the original measured contaminant levels and determine the effect of holding times on analytical results. The findings from these studies have cost saving implications and can guide monitoring program managers on how samples are to be handled and stored before they are analyzed.