Is the accumulation of fire-retardant products in beluga whales a cause for concern?
The demand for fire-retardant products (which reduce the flammability of materials) has drastically increased in the past few decades. These products include a number of organobromine compounds such as polybrominated diphenyl ethers (PBDE). These compounds are similar to polychlorinated biphenyls (PCB) in that they are resistant to degradation and accumulate in organisms, notably marine mammals.
Peering through the looking glass
Fat samples from the carcasses of 54 belugas (28 females and 26 males) found stranded on the shores of the St. Lawrence between 1988 and 1999 were analyzed to determine PBDE concentrations.
PBDE concentrations averaging 430 to 540 nanograms per gram of body weight (ng/g) were measured in the fat of St. Lawrence belugas. Even if these concentrations are 10 to 25 times higher than those measured in some belugas sampled in the Arctic, they are nevertheless considered low with respect to certain populations living close to other densely populated and industrialized regions of the world. However, researchers are measuring very high rates of accumulation of PBDEs in St. Lawrence belugas; in fact, concentrations are increasing exponentially, doubling every three years. Scientists fear that St. Lawrence belugas might some day reach the top of the PBDE contamination scale, given the growing demand in Canada for these products and the absence of rules and regulations on their use in North America. There is also concern in the scientific community about the potential impact of contamination by these products, as a growing number of studies are revealing that PBDEs can cause hormonal and neurological disorders, and possibly cancer. Like other contaminants detected in St. Lawrence belugas, PBDEs might be hampering the recovery of this threatened population.
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Toxic Substances Research Initiative (TSRI), Species At Risk Coordination des Espèces en Péril (SARCEP) and Fishery and Ocean Canada’s Environmental Science Strategic Research Fund (ESSRF).
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PBDEs: use, accumulation, toxicity and … legislation?
Demand for fire retardant products has increased dramatically in recent decades. Many products that surround us, such as computers, furniture and automobiles, are treated using these compounds to reduce the risk of them catching fire. The resulting decline in the number of residential fires is just one of many examples of the benefits of the increased use of fire retardants over the past few decades. Of the compounds most in demand, PBDEs—compounds that were approved years ago—have only been in strong demand since the early 1980s. The Americas consume a record 50 percent of worldwide production of PBDEs, compared to only 12 percent in Europe.
PBDEs are released into the environment as much during production, use and recycling as they are through domestic garbage, landfill sites and incinerators They are similar to PCBs in that they do not break down easily, are persistent in the environment and accumulate in organisms. One example of this comes from a recent study carried out in San Francisco Bay, a densely populated, industrialized area of California, U.S.A. This study demonstrated that PBDEs are on the rise in fish species caught both commercially and by sport fishermen. PBDE levels tripled in halibut and striped bass between 1997 and 2002. Simultaneously, PBDE levels measured in human breast tissue were 10 times higher for women from this area of the United States than for women from Japan and Europe, and these levels are increasing. Moreover, harbour seals in San Francisco Bay are among the most heavily contaminated marine mammals in the world with levels of approximately 5000 nanograms of PBDEs per gram of body weight (ng/g).
With the situation so alarming in California, what is it like here in Canada? Recent studies have shown that PBDE levels are on the rise in Canada in human breast milk, marine mammals, bird eggs and fish, for starters. A study published in 2004 stated that PBDE levels were higher in farmed salmon than they were in wild salmon. The authors concluded that eating farmed salmon increased the risk of exposure to PBDEs. Health Canada, on the other hand, declared that according to information gathered by government scientists PBDE levels measured in Canadian food, including farmed salmon, pose no threat to human health. Rising levels have also been measured in Arctic ringed seals, thus demonstrating that PBDEs can travel great distances. Average levels in St. Lawrence beluga whales are between 430 and 540 ng/g. A high accumulation rate, with levels doubling every three years, was also noted. These facts reflect a growing accumulation of PBDEs in North America resulting from increasing world demand for these products and a present lack of controls and regulations for their use in North America.
These PBDE accumulations raise serious health concerns. A limited, but growing, number of studies carried out on lab mice and rats have revealed the toxicity of PBDEs, even at low levels. Results show that effects are more harmful from exposure during the early developmental stages of life: during foetal development or soon after birth. This is a both a critical and a vulnerable stage of development for the nervous system. Researchers have noted permanent nerve damage in laboratory animals including a drop in learning capabilities—which may worsen over time—and sensory motor responses. PBDEs also appear to interfere with hormone production in the thyroid gland. These hormones play an essential role in the development of the brain. There are many consequences associated with the poor performance of the thyroid gland including fatigue, depression, anxiety, unexplained weight gain, loss of hair and low libido. Serious consequences, such as mental retardation, can also occur during foetal development. A delay in the onset of puberty was also noted in lab rats, along with a decrease in the weight of reproductive organs in males. A study carried out 15 years ago on mice also showed that exposure to PBDEs could provoke the formation of cancerous tumours. Tumours in the liver, thyroid gland and pancreas were noted in this study.
High PBDE levels in food and human tissues, combined with health risks, have led several governments and companies to limit the use and production of these compounds. In the early 1990s Europe began reducing the use of PBDEs on a voluntary basis. Since 2004, the European Union has banned two of the three commercial forms of PBDEs. The result: PBDE levels in the environment are falling. Since the progressive elimination of PBDEs in Sweden, which began in 1997, there has been a notable drop in these toxic products in Swedish mothers’ milk. In 2003, California became the first U.S. state to adopt a regulation that will eventually ban the manufacture, fabrication and distribution of any product containing certain types of PBDEs starting in 2008. Already, several companies, including Sony, Apple, Ericsson, IBM, Intel, Motorola, NEC, Panasonic, Phillips and Ikea, use alternative products to PBDEs, products considered to be safer. The main company producing PBDEs in North America indicated that it would halt production by the end of 2004. The results of scientific studies, some of them Canadian, reporting the presence and toxicity of PBDEs in the environment very likely contributed to this company making this decision, even before legislative measures are put in place in Canada.
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