Skip to navigation | Skip to content

Polar bears face melting chemical cocktail

A male polar bear waits for an ice sheet to form

Polar bears are particularly at risk, because they are at the very top of the Arctic food chain (Source: Iain Williams/Reuters)

Polar bears, the icon of the Arctic, are under threat from the twin challenges of climate change and chemicals that are not breaking down in the region's cold waters.

Research published in the journal Science of The Total Environment shows the retreat of sea-ice in the Arctic could increase the exposure of species such as polar bears to persistent organic pollutants, which include flame-retardants and substances used to harden plastics.

Scientists believe the pollutants, locked in the polar ice for decades, could be released into the ocean as the ice melts due to climate change.

It is estimated annual summer sea-ice cover in the Arctic is now up to a third less than it was thirty years ago.

According to study co-author Professor Bjorn Munro Jenssen, an eco-toxicologist from the Norwegian University of Science and technology (NTNU), polar bears are particularly at risk, because they are at the very top of the Arctic food chain.

"These contaminants are bio-accumulated and bio-magnified up the food chain. So the higher you are, the higher the contaminants," says Munro Jenssen.

The fact a polar bear's favourite meal is seal doesn't help.

"These contaminants accumulate in fat and the polar bear only eats the fat of seals. And they eat maybe a few hundred or a thousand seals per year."

"These contaminants are toxic, even in low concentrations. So they can affect the hormone system, the immune system probably the reproduction rate and the survival of the bears … maybe not a lot, but enough to have an effect on the numbers of polar bears."

Even though the Arctic covers a vast area, it's estimated there are currently only 20-25,000 polar bears.

Climate change

Munro Jenssen believes climate change will cause a shift in the spreading of contaminants throughout the world.

"We think the rate of contaminants from populated areas to the Arctic can increase," he says.

"When the ice melts, maybe more contaminants will come into the environment and that will probably make the animals more exposed for a longer time."

Despite its pristine appearance, concentrations of human-made compounds in the Arctic are high.

Air and water currents bring pollution from industrialised countries thousands of kilometres away.

"[They] start to condense and ... they stay in the Arctic because the temperatures are so low", says Dr Reinhold Fieler from Akvaplan Niva, an environmental consultancy that specialises in the Arctic.

"So we have PCBs (polychlorinated biphenyls) and hydro-carbonated substances which…stay in the area and get into the animals," he says.

"They will break down but it takes a much, much longer time (in the Arctic)".

Hormonal changes

Fieler is particularly concerned by a group of compounds used to harden the plastics, which mimic hormones.

"They change the hormone system of the animals so that some polar bears have actually turned from being female to male," he says.

The good news, according to Munro Jenssen, is that the polar bear has already demonstrated it can adapt to climate change.

"From 9000 to 6000 years ago, it was probably much warmer in the Arctic than it is today, and the polar bears survived that period."

But, he says the complicating factor of chemical contaminants may hinder this adaptation.

"So for bio-diversity in the Arctic it will be a great loss, because the number of animals will probably become very low."

Tags: environment, climate-change, pollution, water-pollution, animals, mammals