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.

How does this affect me?

Simply said, what's bad for the goose is bad for the gander. If harbor seals, herring and salmon are contaminated with PBDEs, what is in store for us?

Compromised Health in Marine Species

Harbor seals inhabiting the Puget Sound – Strait of Georgia region are exposed to many different chemicals. PCBs continue to present a health risk to Puget Sound seals, in particular, based on a 'weight of evidence' from past and ongoing research. A series of studies determined that PCBs affected the immune system, the endocrine system and the reproductive system of harbor seals.³⁴

However, the rapid emergence of a new class of endocrine disrupting chemicals, the PBDEs, in the seals of this region signal a potential new threat to their health. PBDEs have been found to affect neurological development, thyroid hormone levels and immune function in laboratory animals.³⁵ Exposure to high levels of PBDEs, in conjunction with PCBs, could adversely affect the health of seals and other wildlife in the Puget Sound – Strait of Georgia region.

Likelihood of Harm Based on Chemical Structure and Animal Studies

Scientists use structure activity relationships to make environmental and human health assessments regarding certain classes of chemicals. This is based on decades of research linking certain chemical structures with exposure to humans and the environment. PBDEs are very similar in structure to PCBs, which biomagnify in the food chain, are extremely persistent and bind to fat and sediments. In addition, the bromine-carbon links in PBDEs are weaker, which means they can degrade or break down more readily than the chlorine-carbon links in PCBs^.36

Studies in laboratory animals link PBDEs with effects on hormone (thyroid) function, which are critical to normal brain function.

Do PBDEs present a human health risk?

Over the course of our lifetime, humans are exposed to a wide range of industrial contaminants, including PBTs. Although it is unclear whether the currently-used PBDE flame retardants are affecting human health, similar compounds (e.g. PCBs) have been associated with effects on the immune, hormone and neurological systems. In addition, more detailed studies using laboratory animal models have discovered that PBDEs, like PCBs, can affect their health. Given the widespread occurrence of PBT contaminants in humans, and the health risks that have been identified using a variety of methods, there exists reason for concern about the increasing levels of PBDEs in humans and in the environment. Humans are exposed to thousands of chemicals and health risks through their personal habits (food, smoking, occupation, household), making it exceedingly difficult to identify chemicals directly responsible for health effects. However, concerns are mounting that PBT and other contaminants are playing a role in the increases in developmental, neurological and other disorders observed within the US population over the last 30 years. This includes a ten-fold increase in autism; a two-fold increase in asthma; a 62 percent increase in leukemia; 40 percent increase in childhood brain cancer and 3-5 percent increase in birth defects in all babies.42,43,44 Although some increase is attributable to better data collection and reporting, the strong overall increasing trend of these contaminants in the environment is becoming well established. With harbor seals providing evidence of PBT-related health effects in Puget Sound, and with levels of PBDEs in these same seals doubling every four years, it is difficult to deny an emerging regional health risk to humans and wildlife in this region.

PBDEs in Breast Milk and Umbilical Cord Blood (Newborn Babies)

Harbor seals can provide a "canary in the coal mine" service to us, as they remind us of the dangers of releasing persistent chemicals into the aquatic environment. As highly exposed animals, they may suffer from adverse effects before humans, and thereby provide an early warning about possible health effects.

PBDEs were found in the breast milk of healthy, new mothers in a Pacific NW study,³⁷ with levels ranging from 6-321 parts per billion (ppb) measured in milk fat. These levels are 20 to 40 times higher than measured in Sweden and Japan. Another nationwide study found PBDEs in the umbilical cord blood of newborns, including up to 9630 parts per trillion/lipid weight of deca-BDE, which some industry analysts suggest are not bioavailable.^38,39,40

PBDEs in Household Dust

A recent study indicates very high levels of PBDEs in common household dust. BDE-47, BDE-99 and BDE-209 comprised 90 percent of the makeup, by weight, of the samples. BDE-209, a primary part of deca-BDEs, was found in 42 percent of the samples. Levels of Deca averaged 2,394 ppb. This evidence provides contrary evidence to the assertion that BDE-209, due to its molecular size, is not bioavailable, thereby exposing humans or wildlife^.41

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