Application of EPA Method 1628 for PCB Congeners in Fish Tissue Analyses: Matching the Method to the Question to be Answered

New Organic Monitoring Techniques
Oral Presentation

Prepared by H. McCarty
General Dynamics Information Technology, 3170 Fairview Park Drive, Falls Church, VA, 22042, United States


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

ABSTRACT

The Standards and Health Protection Division within the Office of Water has used versions of Method 1668 in seven nationwide studies of fish tissues since 2000. One of the goals of those studies has been to compare the Total PCB concentrations in the fish to a cancer-risk level of 12 ng/g in fish tissue and assess the extent to which fish in U.S. pose a risk to human health. Aside from the high cost of Method 1668C analyses, one of the greatest challenges has been the risk that the sensitivity of the method can lead to low-level background contamination that calls the results into question individual sample results. Minimizing that risk at a laboratory involves costs, but there are also added costs associated with data review and validation prior to EPA’s use of the results. The Office of Water’s January 2024 publication of Method 1628 for PCB congener analysis was designed to help move Clean Water Act monitoring of PCBs away from Aroclor analyses, yet avoid issues of background contamination in commercial laboratories that are a concern with Method 1668C. To estimate the potential impact of moving from Method 1668C to Method 1628, we used the full-congener results from the 2022 National Lakes Assessment for 413 fish tissue samples analyzed by Method 1668C to create a simulated data set from the use of Method 1628. Using the pooled MDL values from Method 1628 and adjusting for minor differences in co-elutions, we calculated the Total PCB results. While the total number of congener “hits” was drastically reduced using Method 1628, the impact on the assessment of the Total PCB results against the 12 ng/g screening value were much less than expected. The comparison also illustrates the benefits of matching the capabilities of the methods used to the questions to be answered.