PCBs and PBDEs in Salish Sea harbour seals from 1984 to 2014: notable improvements following regulatory changes

As high trophic level, non-migratory marine mammals, harbour seals (Phoca vitulina) inhabiting the Salish Sea provide an integrated signal of localized food web contamination. Blubber biopsies from harbour seal pups were collected at four sites in the Salish Sea (Hornby Island and Burrard Inlet in Canada; Smith Island and Gertrude Island in the USA) and analyzed for polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs). Seals from Gertrude Island had the highest PCB and PBDE concentrations, although spatial variation was less pronounced for PBDEs. PCBs in seals declined between 1984 and 2014, reflecting their regulation in the mid-1970s. PBDEs, however, doubled every 3.1 years between 1984 and 2003, before dropping in 2009. This recent drop may reflect a response to regulatory measures taken in North America after 2004. The application of toxicity reference values (TRVs) for the dominant PCBs to our results reveal an improving “health index” over time in Gertrude Island seals in this study. However, the application of a harbour seal-specific PCB TRV of 1.3 mg/kg revealed that a majority of Gertrude Island seal pups exceeded that threshold in 2003, while seals from the other sites had relatively good health indices. Analyses of 2014 samples are underway and will increase our assessment of temporal trends as well as the effectiveness of PBDE regulations. Our study suggests that regulations have been very effective in reducing health risks to Salish Sea harbour seals, although the slow nature of these improvements underscore the lingering risks associated with very persistent contaminants