Toxics in Harbor Seals
This indicator describes the presence and effect of persistent bioaccumulative toxics (PBTs) in harbor seals and in the fish they eat. PBTs are chemicals that dissolve easily in animal fat and do not break down readily, causing them to build up or bioaccumulate in the food web.

	PBTs, persistent bioaccumulative toxics, are found in area harbor seals. Read more…
	Concentration of PBDEs and other PBTs in harbor seals, herring and other components of the marine food web is due to many factors. Read more…
	If harbor seals, herring and salmon are contaminated with PBDEs, what is in store for us? Read more…
	There are ample reasons for concern and immediate action regarding PBDEs. Read more…

Introduction to the Toxics in Harbor Seals Indicator

This indicator describes the presence and effect of persistent bioaccumulative toxics (PBTs) in harbor seals and in the fish they eat. PBTs are chemicals that dissolve easily in animal fat and do not break down readily, causing them to build up or bioaccumulate in the food web.

This 2006 indicator illustrates the presence of toxics from Washington State and British Columbia over time (1984 to 2003) and highlights the presence of Poly-Brominated Diphenyl Ethers (PBDEs) in harbor seals. The indicator also explores the level and distribution of both PBDEs and Poly-Chlorinated Biphenyls (PCBs) in Pacific herring, a key food of harbor seals. Other PBT issues of interest are discussed as well.

What are PCBs and PBDEs?

PCBs (polychlorinated biphenyls) represent a family of structurally-related chemicals that were designed and used as heat resistant oils and waxy solids. PCBs were sold in several forms containing different combinations of up to 209 different congeners (chemical types). PCBs are considered persistent, bioaccumulative and toxic. Because of these properties, PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics and rubber products; in pigments, dyes and carbonless copy paper and many other applications. More than 1.5 billion pounds (700,000 kg) of PCBs were manufactured in the United States prior to cessation of production in 1977. PBDEs (polybrominated diphenyl ethers) represent a family of structurally related chemicals that were designed as flame retardants that have been used extensively in North America. Like PCBs, there are up to 209 different congeners possible. A variety of congeners are found in three commercial formulations (Commercial Pentabromodiphenyl Ether, PentaBDE; Commercial Octabromodiphenyl Ether, OctaBDE; and Commercial Decabromodiphenyl Ether). They are found in many common household items including upholstery, electronics, and some textiles. Like PCBs, they are persistent, bioaccumulative and toxic. However, the PBDEs differ in some ways from the PCBs; they have bromine atoms instead of chlorine; they are thought to be less persistent and bioaccumulative than the PCBs, with some evidence pointing to degradation into less brominated PBDEs with highly brominated compounds. PBDEs continue to be widely used in North America, although penta and octa products have been withdrawn from the market. The remaining product (DecaBDE) is therefore likely to continue to enter the environment in its commercial form or as a degraded mixture which resembles some of the penta and octa profiles. While DecaBDE in its original form is considered relatively safe, it is likely to degrade into more toxic forms.5 Biomagnification is the bioaccumulation of a substance up the food chain by transfer of residues of the substance in smaller organizations that are food for larger ones. This results in higher concentrations in organisms, such as harbor seals, at higher levels in the food web (U.S. Geological Survey).6,7

Since currently-used PBDEs represent a class of chemicals considered to be persistent, bioaccumulative and toxic (PBT), this indicator also draws on evidence from studies of other contaminants. Three other classes of PBT chemicals (also often referred to as persistent organic pollutants, or POPs), including PCBs, Poly Chorinated Dioxins (PCDDs), and Poly Chlorinated Dibenzo Furans (PCDFs), and were highlighted in the 2002 indicator of toxics in the Puget Sound Georgia Basin ecosystem, 'POPs in harbour seals.'¹

Bioaccumulation of toxic pollutants in marine life is most likely in animals like harbor seals and orca whales that feed near the top of the food web. PBDEs, PCBs, dioxins and dibenzofurans are some of the human-generated, persistent bio-acccumulative toxic pollutants (PBTs) that are monitored in harbor seals within our local inland marine waters. These marine mammals, like humans, are exposed to a wide variety of toxic compounds throughout their lifetime.

In the marine environment, perhaps nothing captures the heart more than the deep, soulful eyes of the playful harbor seal (Phoca vitulina). With adults weighing anywhere from 60 kg/132 lbs to 120kg/264 lbs, and inhabiting our inland marine waters (3 km/1.86 miles to 30 km/18 miles offshore), the harbor seal has proven to be a useful indicator of persistent pollutants^.2

These animals are proxies for assessing overall ecosystem conditions, and provide insight regarding environmental conditions in food webs across space and time.³ Harbor seals are also good indicator or "sentinel" species because they are relatively common in both British Columbia and Washington State, are non-migratory, long-lived and vulnerable to the accumulation of PBTs.

Adult and juvenile Pacific Herring (Clupea harengus pallasii) are an important forage fish to harbor seals and other marine mammals, diving birds, and many fish species. Herring eggs are eaten by shore birds, fish, crabs and thier larvae are eaten by planktivores, including jellyfish. You can think of them as the bread and butter of the sea. With a trout-like body shape, large scales, single dorsal fin and bluish-green coloration, herring are also an important recreational fishing bait and commercial and subsistence fish.⁴

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