Environmental Toxins Discovered in Polar Bear Brains: Chemical Danger for Wildlife

Polar bears are in trouble--and not just from climate change. Researchers have found that environmental toxins are seeping into the brain tissue of these charismatic mammals, potentially causing unforeseen side effects as they enter the Arctic food chain.

PerFluoroAlkyl Substances (PFASs) and precursor compounds have been used a wide variety of commercial and industrial products over the past six decades. They can be found in oil and water repellent coatings for textiles, paper products, carpets, food packaging and other materials. Unfortunately, the same reason why we prize these chemicals also explains why they're filtering into the food chain; PFASs are highly resistant to chemical, thermal and biological degradation.

This wouldn't be an issue if PFASs were completely harmless. Yet an increasing amount of information is accumulating on the toxicity of these compounds. In fact, researchers have documented carcinogenesis, genotoxicity and epigenetic effects as well as reproductive and developmental toxicities, neurotoxicity, effects of the endocrine system and immunotoxicity when it comes to PFASs. Needless to say, that's a huge issue.

In order to see how far these compounds have infiltrated the food chain, researchers decided to take a look at polar bears. More specifically, they wanted to see if PFASs had the ability to cross the blood-brain barrier, something that could have major implications for both wildlife and humans.

Previous studies have shown a dramatic increase of several PFASs in polar bears, including one known as perfluorooctane sulfonate (PFOS) as well as several compounds of the perfluorinated carboxylate (PFCAs). In fact, PFOS have been found at concentrations in the liver that are 100 times higher than in ringed seals, a polar bear's preferred prey.  In this study, the researchers examined the brains of polar bears. Their findings were disturbing.

"We know that fat soluble contaminants are able to cross the brain-blood barrier, but it is quite worrying that PFOS and PFCAs, which are more associated with proteins in the body, were present in all of the brains we analyzed," said Robert Letcher of Carlton University in a news release.

He's not the only one that's worried about the results. Rune Dietz of Aarhus University also expressed concern.

"If PFOS and PFCAs can cross the blood-brain barrier in polar bears, it will also be the case in humans," said Dietz. "The brain is one of the most essential parts of the body, where anthropogentic chemicals can have a severe impact. However, we are beginning to see the effect of the efforts to minimize the dispersal of this group of contaminants."

Currently, many of these compounds have been phased or are being phased out of production. Unfortunately, because of their ability to persist in the environment, it's likely that these compounds will continue to be an issue in years to come.

The findings are published in the journal Environ Toxico Chem.