Polar bear fur could hold the secret to replacing ‘forever chemicals’

White fur, blubbery skin, sharp claws. Polar bears seem perfectly adapted to their frigid habitat up north.

Now, researchers have discovered the bears have another unexpected Arctic adaptation: greasy fur. It’s a trait that might help us find alternatives to “forever chemicals,” a class of widely used compounds that are linked to a range of health problems in people.

An oily substance secreted by glands in polar bears’ skin helps keep their fur from freezing in subzero temperatures, according to a study published Wednesday.

The anti-icing ability of their naturally greasy pelts rivals that of some of the most advanced human-made fibers coated with those chemicals, which are used to repel oil, heat, water and ice.

By re-creating the bears’ ability to resist icing, researchers hope to develop healthier alternatives to these toxic chemicals.

“If we do it in the right way, we have a chance of making them environmentally friendly,” said Bodil Holst, a researcher at the University of Bergen in Norway who co-wrote the study published in the journal Science Advances. “That is certainly the inspiration here.”

A physicist, Holst normally doesn’t think about polar bears. But about five years ago, she was watching a German television program that mentioned the Arctic animals that got her wondering how their fur managed to stay free of ice even after diving into the water.

Their slippery skin is a huge advantage as hunters. Polar bears lurk near holes in sea ice until a seal surfaces and — snap — they’ve caught their next meal. The bears’ ability to slide on their bellies with minimal friction between fur and ice helps prevent the seals from taking notice. Inuit people made sandals from polar bear pelts to move in almost complete silence across the ice.

“I just thought: ‘Well, this is fascinating. How can this be?’” Holst said.

So Holst gathered a team of a dozen and a half scientists to solve the mystery. “When you say the magic word ‘polar bears,’” she said, “everybody wants to join.”

To test how well the animals’ fur resists icing, researchers froze blocks of ice to samples of washed and unwashed polar bear fur, as well as human hair attached to a synthetic scalp, and ski equipment that contains per- and polyfluoroalkyl substances, also known as PFAS. One of the researchers, Julian Carolan, used his own hair for the experiment.

“It wasn’t that pleasant to do,” said Carolan, a doctoral candidate who led the paper. “I had to let my hair get very greasy over a week, which did not look very good. I then shaved it all off as close as I could to the scalp, which was tough on account of the greasiness. This also left me with a bald head in the cold month of January last year.”

The oily bear fur and the PFAS-laden ski equipment resisted adhering to ice, compared with samples of oily human hair and fur washed of its grease. A chemical analysis revealed that the grease on the bears’ fur — a substance scientists call sebum — contains a concoction of cholesterol and other lipids that distinguish it from the sebum found on other mammals.

That unique recipe is what made polar bears resist icing.

The new study “confirms what those of us that have handled bears have known,” said Geoff York, a biologist with Polar Bears International who was not involved in the study. “When we get them on the ground, and they’re safely sedated, they’re amazingly dry.”

Until now, he added, “we didn’t know the mechanism” behind their ability to resist ice.

Of course, getting significant amounts of sebum from polar bears, which are threatened with extinction due to rising temperatures and shrinking sea ice, isn’t possible. But now that researchers know the formula behind polar bear grease, they hope to design PFAS-free coatings made with similar ingredients.

“It offers insights and inspirations to develop materials that are naturally sourced and provide a solution to the long-standing icing issue without causing” harm, said Manish Tiwari, a nanoengineering professor at University College London who co-wrote the study.

With strong bonds between carbon and fluorine atoms, PFAS have been used to make nonstick cookware, water-resistant clothing, food packaging, dental floss and a variety of other products.

But mounting evidence suggests many PFAS pose risks of cancer, infertility and other health problems to people at even low levels of exposure. The substances are nicknamed “forever chemicals” since they persist for years in the environment.

Even if a practical application is years away, Holst, the physicist who conceived the research project, is glad to have studied such a beloved animal.

“I’m really thrilled I’ve been able to discover something new about polar bears,” she said. “I didn’t see that one coming.”