Declining concentrations of persistent PCBs, PBDEs, PCDEs, and PCNs in harbor seals (Phoca vitulina) from the Salish Sea

- PCB, PCDE and PCN concentrations declined by 71-98% in harbor seals from the Salish Sea between 1983 and 2003.
- PBDE concentrations doubled every 3.1 years in harbor seals from 1984 to 2003 but declined thereafter.
- Among Salish Sea harbor seals, those in Puget Sound had the highest PCB and PBDE concentrations.
- Changes in food web productivity may explain unexpected contaminant patterns in seals in 2003.
- The 53,000 harbor seals of the Salish Sea had an estimated burden of 2.5 kg of PCBs in 2009.

As high trophic level, non-migratory marine mammals, harbor seals (Phoca vitulina) inhabiting the Strait of Georgia, Juan de Fuca Strait and Puget Sound (collectively referred to as the Salish Sea) in northwestern North America provide an integrated measure of coastal food web contamination. We measured congener-specific polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), polychlorinated diphenylethers (PCDEs) and polychlorinated naphthalenes (PCNs) in blubber biopsies from free-ranging harbor seal pups inhabiting four sites in the Salish Sea in 2003. While legacy PCBs dominated the composition of these contaminants in seals at all sites (PCBs > PBDEs > PCDEs > PCNs), PBDEs were noteworthy in that they averaged as much as 59% of total PCB concentrations. We further evaluated temporal trends in seals sampled at one of these sites (Puget Sound) for PCBs and PBDEs between 1984 and 2009, and for PCDEs and PCNs between 1984 and 2003. PBDE concentrations doubled every 3.1 years between 1984 and 2003, but appeared to decline thereafter. Over the course of the 20 years between 1984 and 2003, PCB concentrations had declined by 81%, PCDEs declined by 71%, and PCNs by 98%. Overall, results suggest that regulations and source controls have noticeably reduced inputs of these contaminants to the Salish Sea, consequently reducing the associated health risks to marine wildlife. We estimate the total mass of these contaminants in the 53,000 harbor seals of the Salish Sea in 2009 to be 2.6 kg PCBs and 1.0 kg PBDEs, compared to just trace amounts of the PCDEs and PCNs.