PCBs in fish caught in Maryland from 1986 to 2021

Historical dataset collected to establish fish consumption advisories represents a valuable source of information on contamination levels in the waterbodies and changes over time. Of particular interest to environmental managers is the extent to which current and future levels of persistent chemicals in fish reflect the expected response to completed remediation projects. In this study, PCB concentrations measured across 323 monitoring stations in Maryland over 3 decades were curated and used to perform spatial and temporal analysis. Five watersheds out of 25 were identified as highly impacted by PCBs including the Upper Chesapeake Bay. Known areas of contamination were better predictors of PCBs in fish than generic land use or toxic release information, but PCB transport across watersheds may also explain PCB levels in watersheds with little or no known PCB sources. Impacted watersheds showed slow nationally consistent natural attenuation rates ranging from 2% to 6% yr-1, except the Gunpowder-Patapsco near Baltimore MD, where no temporal trend was observed since 1996. The overall study showed that PCB source mitigation implemented across Maryland and surrounding States helped recoveries, but more efforts are needed to fully control all PCB sources (legacy or ongoing) that are still impacting the rivers and fish.