Pollutants in polar bears (Ursus maritimus)

Two polar bear cubs stick up their heads from behind their mother, who is laying on the ground. In the background snow and ice.
Photo: Jon Aars / Norwegian Polar Institute

The total stress of pollutants in polar bears in Svalbard is dominated by fat-soluble organic pollutants, their metabolites and perfluorinated compounds. Polar bears are exposed to high levels of persistent contaminants, increasing in concentration higher in the food chain. The monitoring shows a significant reduction in fat-soluble organic pollutants that are internationally regulated.

What is being monitored?

Persistent organic pollutants

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The figure shows levels of HCB (hexachlorobenzene), HCH (beta-hexachlorocyclohexane) and DDE measured in blood plasma of adult female polar bears in Svalbard in the period 1992 to 2014. There is a yearly decrease for HCB and DDE of 2 and 6%, and there is no trend for HCH.

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The figure shows levels of the bromated flame retardant BDE-47 measured in blood plasma målt i blodplasma of adult female polar bears in Svalbard in the period 1997 to 2014. Yearly decrease is 4%.

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The figure shows levels of PCB-153 and oxychlordan measured in blood plasma in adult female polar bears in Svalbard in the period 1992 to 2014. Yearly decrease is 4-5%.

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The figure shows levels of perfluorinated compounds PFOS (perfluorooktasulfonate), PFNA (perfluorononanoate) and PFUnDA (perfluorundekanoat) measured in the blood plasma of adult polar bear females on Svalbard in the time-period 2000-2014. For PFOS, there is a yearly decrease of 14% from 2003 to 2009, after which there is no further trend. PFNA and PFUnDA rise by 2.5% and 2% per year respectively.

Status and trend

Polar bear monitoring shows that concentrations of fat-soluble organic pollutants (PCB-153, DDE and oxychlordane) declined by 4–6% per year from 1992 to 2014. The time trend is therefore the same in the polar bear as in other arctic species. This is a confirmation of the success of the international regulations of these substances. 

Levels of HCB in polar bears in Svalbard also shows a decline in the period.  Yearly decrease is 2% between 1992 and 2014.

The bromated flame retardant BDE-47 has been analyzed since 1997. Levels of BDE-47 shows a declining trend of 4% per year in polar bears in Svalbard between 1997 and 2014.

Most studies from Svalbard and other places in the Arctic shows that the old, classic pollutants as PCBs, DDT, chlordanes and HCH decreases. A recent study from eastern Greenland show that levels of PCB and bromated flame retardants (mainly BDE-47) in polar bears have increased in recent years. In polar bears in Canada, levels of DDE and chlordanes declined from early 1990ies to 2005-2008 with the exception of some areas.  Trends for other pollutants in polar bears in Canada varies.

The levels of PFOS in polar bears has reduced by 14 % per year from 2003-2009, but since 2009 the PFOS levels have remained stable. The Levels of PFNA and PFUnDA have, by contrast, risen by 2.5% and 2% per year respectively, from 2000-2014.

Polar bears in Svalbard are among the polar bear populations with the highest levels of contaminants among European and North-American populations in the Arctic.

Causal factors

There is one main reason why the levels of the so-called old organic pollutants in polar bears are sinking. Their manufacture and use are nationally and internationally regulated. Efforts to regulate PCBs and chlorinated pesticides started in the late 1970s, and the international ban on the contaminants took effect in 2004, through the Stockholm Convention.  The main sources of emissions of these contaminants has therefore stalled. The reason for the contaminants still being present in the environment is because they are stable and that they can be recycled and concentrated in the food chain.

Production and use of the newer POPs BDE-47 and PFOS have been restricted in the past fifteen years. They were included in the Stockholm Convention in 2009. Stable concentrations of PFOS since 2009 suggest that the marine environment on Svalbard is still exposed to PFOS that are slowly transported by ocean currents. The rising levels of PFNA and PFUnDA are most likely connected to the production and use of these chemicals and their antecedents (e.g fluorotelomers). PFNA and PFUnDA are regulated at the national level in some countries, but the chemicals antecedents are not currently regulated.

Consequences

Levels of contaminants in polar bears are still high. Polar bears from Svalbard and Eastern Greenland are the best studied populations for effects of contaminants. Results indicate an effect on the immune system, making the polar bears more susceptible to diseases In addition, high levels of contaminants in polar bears has been connected to disturbances in the balance of hormones important to reproduction, development processes and energy metabolism. Further, studies of East-Greenland polar bears have connected large contaminants exposure to a reduction in genitals, osteoporosis and changes in liver and kidneys. Contaminants can also disturb the fat storing processes of polar bears. 

Polar bears have high levels of PCB metabolites, as polar bears are very effective in transforming PCB to more water soluble versions. The main reason for this process is that these versions of PCB are possible to excrete from the body. Still, several metabolites are contained in the body and shows higher toxicity than their mother compounds.

Polar bear cubs are exposed to higher levels of fat soluble contaminants. An example is PCB in blood plasma, where the level is more than twice the level compared to their mothers. Small polar bear cubs receive large doses of these substances from their mothers through the milk.  This is especially alarmingly because these contaminants can reduce the function of the hormones regulating their development. 

Climate change can enhance the effects of contaminants. Sea ice is the most important hunting area for the polar bears. Reduction in sea ice causes elevated levels of contaminants in polar bears, because less ice means poorer food availability and thinner polar bears with a larger concentration of contaminants.  Polar bears have higher levels of contaminants in spring than in autumn, especially after winters with little sea ice.

About the monitoring

The polar bear is a predator at the top of the marine food chain in the Arctic, mainly eating seals hunted at the sea ice.

Mapping of contaminant levels in polar bears in Alaska, Canada, Greenland, and Norway shows that polar bears in Svalbard are among the polar bear populations with the highest levels of contaminants. Negative effects of the present contaminant levels are documented, meaning the contaminants are a threat to the polar bear population in Svalbard. Hence, monitoring is necessary. 

The total load of contaminants can also be affected by rapid melting sea ice, further underlining the importance of monitoring levels of contaminants in polar bears.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring