By Isabelle Groc
In the 19th century, humans used whale oil to illuminate city streets and houses. While whales are now protected from the exploitation of their blubber, they are tragically faced with another danger related to flammability and human activities. Scientists have found that many marine mammals are highly contaminated with emergent forms of toxic chemicals. Of particular concern are Polybrominated Diphenyl Ethers, or PBDEs, that are used as flame retardants in many consumer and industrial applications.
“The irony to me is that we used to burn whale oil and now we are making whale oil difficult to burn because we have introduced these chemicals that prevent fire into their blubber,” says Peter Ross, a marine mammal toxicologist with the Department of Fisheries and Oceans.
In a recent study, Ross compared levels of contaminants in typical harbour seal diets in the Strait of Georgia and Puget Sound. In the Strait of Georgia, he found that PBDEs had the third-highest concentration in a typical seal diet after PCBs (polychlorinated biphenyls) and the persistent pesticide DDT. PBDE levels were even higher in the Puget Sound diet, where they had the second-highest concentration after PCBs. Ross indicated that PBDE levels are increasing exponentially, and will surpass PCBs within about fifteen years. “If we are not going to act, then at some point in the future they will be the number one chemical presence in those animals,” he said.
PBDEs are often referred to as the new PCBs: they have similar chemical structures, are persistent, bioaccumulative, and toxic, and are suspected to present similar health risks. PCBs were banned in North America in the late 1970s but are still present in the environment. PCBs have been linked to cancer and cause a range of effects on the immune, reproductive, and nervous systems.
PBDEs are fire retardants that are very widely used in commercial goods such as foam mattresses, furniture, and cars and in plastic housings for computer equipment. While it has been said that such fire retardants have saved many lives from house fires, they are now a cause for concern. PBDEs are released into the environment both during manufacture and through everyday product wear and tear. In particular, studies have shown that the chemical appears to migrate out of its product and attach to household dust. That dust is then inhaled and accumulates in our bodies. Toddlers are at particular risk because they are frequently bringing toys and other objects from the floor to their mouths. As PBDEs are fat-soluble, they tend to build up in body fats. Studies have showed them turning up in women’s breast milk, which would be another source of exposure for infants.
Once released into the environment, PBDEs get carried by the wind and deposited far and wide. As they can persist in the environment for years, they ultimately work their way up the food chain. Marine mammals are particularly vulnerable to such persistent toxins because they are long-lived and at the top of the food chain. As a result, they receive concentrated doses of toxins in the prey they eat.
So far, little is known about the health impacts of PBDEs. Real world studies of the impacts of PBDEs on animals such as killer whales are difficult to conduct because they are exposed to multiple families of chemicals that are likely to interact with each other in affecting the health of the animals. As it is difficult to experiment with human subjects and endangered species, toxicologists have conducted studies with laboratory animals and attempted to extrapolate the results to humans and marine mammals. Laboratory experiments have revealed that exposure to PBDEs is associated with endocrine disruption, impaired reproduction, and reduced immunity; affects neurological development; and disrupts vitamin A and thyroid hormones. The impact of these chemicals is most likely felt when animals are stressed due to limited food supply, pathogens or other environmental stressors. They are most toxic when an organism metabolizes the fat in which they are stored.
While the concentrations of many industrial chemicals in the environment are decreasing, PBDE levels are rising at an exponential rate, doubling every two to five years in North America.
The European Union has already banned two PBDE formulations, octa and penta, but in North America, PBDEs remain largely unregulated. Canada has announced its intention to ban penta and octa PBDEs, and a growing number of states in the U.S. are seeking bans as well. The US Environmental Protection Agency has worked with industry to voluntarily withdraw penta and octa PBDEs from the market; and in practice, a number of product manufacturers such as Ikea, Sony and Volvo have dropped these two members of the PBDE family for alternative chemicals. Consequently consumers can make the choice to avoid PBDEs by buying products such as furniture and electronics from PBDE-free manufacturers, thus encouraging the use of alternative flame retardants.
There is currently considerable disagreement over whether a third form of PBDE known as “deca” poses a health hazard and should be restricted. According to industry, deca PBDE is stable, does not break down or disperse, and is not taken up by animals in the environment. However, new studies suggest that deca PBDE can break down into other forms of PBDEs (octa and penta) that are more harmful and readily absorbed. As Peter Ross suggests, “If you ban penta and octa, but your deca product degrades in the environment to resemble penta and octa, you’re not very far ahead, are you?”
To learn more about how to avoid PBDEs in your daily life, visit: