Danish scientists say studies have shown environmental toxins are entering the brain tissue of polar bears, suggesting they can cross the blood-brain barrier.

The toxins are in a class known as PerFluoroAlkyl Substances, or PFASs, used in a wide variety of commercial and industrial products over the past six decades including water and oil repellent coatings for textiles, paper products, carpets and food packaging, and also in pharmaceuticals, cleaning products and fire-fighting foams, the scientists said.

PFASs have shown a dramatic increase and dispersal around the world over the past four decades, a release from Denmark's Aarhus University said Tuesday.

Studies have documented the toxicity of PFASs on wildlife and human health, including carcinogenesis and genetic effects as well as reproductive and developmental toxicities, the researchers said.

Concentrations of the toxins have been found in eight brain regions of polar bears collected in East Greenland.

Arctic researchers from Aarhus and Carleton University in Canada have used the polar bear as a sentinel species for humans and other predators in the top of the food chain.

"If [the toxins] can cross the blood-brain barrier in polar bears, it will also be the case in humans," Aarhus researcher Rune Dietz said. "The brain is one of the most essential parts of the body, where anthropogenic chemicals can have a severe impact."