Toxins found in Polar Bear brains

Denmark: In a new study, Arctic researchers have discovered an accumulation of perfluorooctane sulfonates (PFOS) – a PerFluoroAlkyl Substance (PFAS) – and several compounds of the perfluorinated carboxylate (PFCAs) grouping in eight brain regions of polar bears collected from Scoresby Sound, East Greenland.

PFASs and precursor compounds have been used in a wide variety of commercial and industrial products over the past six decades.

There has shown a dramatic increase and dispersal of these substances around the world over the past four decades, and an increasing amount of information is becoming available on the toxicity of these compounds.

In the new research, the scientists, from Carleton University in Canada and Aarhus University in Denmark, used the polar bear as a sentinel species for humans and other predators at the top of the food chain.

Polar bears in East Greenland have toxins in their brains, which can impact the endangered animals’ fertility, Danish researchers have discovered. What’s worse is that the polar bears have not have ingested products containing the dangerous perfluoroalkyl substances (PFAS) accidentally.

Dr Robert Letcher, Carleton University, explained: “We know that fat soluble contaminants are able to cross the brain-blood barrier, but is it quite worrying that the PFOS and PFCAs, which are more associated with proteins in the body, were present in all the brain regions we analysed.”

Professor Rune Dietz, Aarhus University, added: “If PFOS and PFCAs can cross the blood-brain barrier in polar bears, it will also be the case in humans. The brain is one of the most essential parts of the body, where anthropogenic chemicals can have a severe impact. However, we are beginning to see the effect of the efforts to minimise the dispersal of this group of contaminants.”

Dietz’s team has studied 500 polar bears in East Greenland for the past 30 years.

The products in question are everyday items like Teflon pans and textile coatings. Precisely because they don’t dissipate into the environment, they travel up the food chain once they’ve been ingested by a lowly fish species. They also travel far distances inside the bodies of the various fish species and marine mammals, which is how they arrive in polar bear habitats. “When you get to the top of the food chain, where the polar bear reside, you get the highest concentration of these toxins,” explains Dietz.

Another recent study from Aarhus University has documented that PFOS concentrations in Greenlandic polar bears and ringed seals started to decline after 2006. Other wildlife populations closer to the sources in Europe and North America have also shown a decline prior to the Greenlandic animals.

Dietz commented: “It is promising to see that the PFAS are on the decline. This development should be encouraged by the authorities globally.

“In the meantime my best advice to the consumers is to go for environmentally labelled products. But avoiding products is difficult, because PFASs are so widespread in many kind of products and they are rarely declared.”

Though no conclusive evidence exists, PFAS are suspected of damaging the brain, liver and reproduction.

“There are higher levels of PFASs in the brains of Inuits (Greenlanders) as well,” explains Dietz.

Even more worryingly, people in industrialized countries who have never eaten marine mammals have PFASs in their brains, too. But, if they eat neither marine mammals nor fish, how do they ingest the toxins? Researchers at the Norwegian Institute for Air Research are the science world’s detectives, trying to establish how the poisonous substances enter our bodies.

“The increase in PFASs in humans and polar bears is very frightening,” notes Dietz. “The good news is that production of products using these pollutants peaked in 2006. But it’s worrying that there’s still very little regulation of PFASs in China.”


Rune Dietz Blog:

other papers published:

Rune Dietz Conference May 2010:

Polar Bear Specialist Group:

Other Polar Bear’ threats:

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