Twenty years later: PBDEs in fish from U.S. sites with historically extreme contamination.

Shortly after their production ban PBDE environmental levels retreated from their peak (circa 2000), but rates of decrease appear to be slowing. Therefore, to update environmental PBDE trends, this study re-examined a U.S. riverine system found in 1999 to have the highest PBDE fish tissue (fillet) burdens in the world. Archived 2018-2020 fish tissues were analyzed for PBDEs and results compared to 1999-2000 and 2007 levels. On a positive note, levels decreased by >75% over 20 years. However, PBDEs were still detectable at each collection site (n = 16) and in 93% of the samples. The highest PBDE level (16,300 ng g-1 lipid weight) was observed in fish from the Dan R., downstream from the Hyco R. (where the world's highest level was previously reported). Levels within Hyco R. fish have declined at an annual rate of 30% through 2007. However, reductions during the subsequent 12 years have diminished to only 1.2%. Fillet levels since 2007 actually increased at an estimated annual rate of 8%. Downstream from the Hyco R. Congener profiles varied between species, likely due to hepatic enzyme debromination, indicating single congener-based health risk may not be protective. Within North America, PBDE fish levels in this freshwater system were twice those of North America's Great Lakes and exceeded by 10-fold those in carp examined near Illinois, USA., another historical hotspot. Average fish PBDE levels also exceed maxima observed in European and Asian riverine systems and were 1000's of times higher than the environmental quality standard (EQS) set by European Parliament (0.0085 ng g-1 wet weight, aquatic biota). Therefore, to protect human health and the environment, PBDE monitoring should remain a priority for regulatory agencies with the goal to identify and eliminate their source and to consider their potential health impacts in the context of other co-existing (emerging and legacy) contaminants.