Environmental Trends 2002

Chemicals in Wildlife

PCBs in Harbour Seals

Dioxins and Furans in Harbour Seals

SOURCE: Ross, P.S. et al. 2001a. PCBs at the top of the food chain: geographical variation in British Columbia and Washington harbour seals. Puget Sound Research 2001 Bellevue, USA. Ross, P.S. et al. 2002. Spatial fractionation of PCB, PCDD, and PCDF congeners in free-ranging harbour seals (Phoca vitulina) from coastal British Columbia, Canada and Washington State, USA. submitted. NOTES: At all sites, blubber biopsy samples were taken from 4-6 week old free-ranging harbour seal pups in good condition. Samples were pooled for Vancouver due to a limited sample size. As a result, the location reflects the site where most samples were obtained, while extra samples were collected in adjacent areas.

What are the contaminant levels in Harbour Seals?

• Harbour seals are good indicators of the contaminant level in coastal food chains because they are at the top of the food chain and spend most of their time in the same place.

• Harbour seals in the Strait of Georgia showed higher levels of dioxins and furans than those in Puget Sound. PCB levels, however, were more than seven times higher in Puget Sound seals.

• The PCB levels found in Puget sound seals are similar to levels that have been found to suppress the immune systems of seals and other marine mammals, leaving them more susceptible to disease.

• Although certain chemicals are banned from use in Canada they are still used in other countries. These chemicals can evaporate easily in hot climates and get carried by wind currents (atmospheric transport) to colder regions, such as mountains in British Columbia and the Canadian Arctic, where they condense.

For detailed information, including graph data, see In-Depth report [pdf].