Pollutants in ringed seals
Last updated 29 March 2017
Moderate levels of contaminants are found in ringed seals (Pusa hispida) from Svalbard. Ringed seals are the polar bear’s main prey, and moderate pollutant levels in ringed seals may contribute to high levels in polar bears. Most of the so-called old pollutants are decreasing in ringed seal, while a similar decrease has not been proven for newer contaminants.
What is being monitored?
Persistent organic pollutants in ringed seals
The figure shows a sharp reduction of PCB-153, DDE and chlordane (sum of transnonachlor and oxychlordan) levels measured in ringed seal blubber in the period 1992-2014. Annual decrease is 6-8%.
(Cite these data: Norwegian Polar Institute (2022). Chordanes, DDE and PCB-153 in ringed seal blubber. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/indikator/influence/pollution/pollutants-in-ringed-seals/)
The levels of hexachlorobenzene (HCB), α-hexachlorocyclohexane (α-HCH) and toxaphenes (sum of congeners 26 and 50) in ringed seal from Svalbard show a decline in the period 1992-2014. Annual decline is 6-11%. The levels of the brominated flame retardant BDE-47 shows no trend in ringed seals from Svalbard.
(Cite these data: Norwegian Polar Institute (2022). HCB, α–HCH, BDE-47 and toxaphenes in ringed seals. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/indikator/influence/pollution/pollutants-in-ringed-seals/)
The figure shows no significant trend of PFOS measured in the plasma of ringed seals over the period 1990-2010. Highest levels were measured in 2004, and in 2010 levels were halved.
(Cite these data: Norwegian Polar Institute (2022). PFOS in plasma in ringed seals. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: https://mosj.no/en/indikator/influence/pollution/pollutants-in-ringed-seals/)
Details on these data
|Last updated||29 March 2017|
|Update interval||Every 10th year|
|Next update||March 2026|
|Commissioning organization||Ministry of Climate and Environment|
|Executive organization||Norwegian Polar Institute|
|Contact persons||Heli Routti|
Individual blubber samples from ringed seals are analyzed.
Samples for surveillance comes from animals which have been shot for research purposes or hunting. The samples are stored frozen at the Norwegian Polar Institute. Samples are also preserved for analyzes of new pollutants in the future. For future analysis, one can choose samples for different purposes.
Analyses of time-trend in the period 1990-2014 consists of animals that are a mix of males and females at varying ages. Since levels of PCB 153, chlordanes, DDE, and BDE-47 is higher in the older than younger animals, results are adjusted for age. Samples are taken from 10 to 19 individuals per year. Localities for PCBs, chlorinated pesticides and brominated flame retardants are limited to the west coast of Spitsbergen. Since PFOS levels vary among fjords, is PFOS only analyzed in seals caught Kongsfjorden.
For analysis of brominated and chlorinated fat-soluble pollutants fat is extracted from blubber. Contaminants in fat extracts are separated and quantified by gas chromatography as described for example in Severinsen et al. 2000 and Wolkers et al. 2008.
Perfluorinated contaminants are extracted from ringed seal blood plasma according to the method described by Hansen et al. 2013.
The work is done according to AMAP guidelines for sampling and analysis. Tissue samples are handeled by people with experience of ecotoxicological studies, to prevent contamination of the samples. The analysis is quality assured by the methods described in the accreditation. It is used only super clean equipment in the lab to prevent sample contamination. For every tenth sample analyzed, a blank and a standard reference sample are analyzed. The laboratory regularly participates in international ring tests.
The Norwegian Polar Institute has all metadata.
Reference level and action level
Since both PCBs, pesticides and perfluorinated is manmade pollutants, and do not occur naturally, the reference value for an unaffected state is zero (actually the detection limit). The decline in the old POPs suggests that the regulations introduced by the authorities have proven effective and that we are on the right path with these contaminants. It is implemented strong measures to limit the spread of persistent organic pollutants. The Stockholm Convention regulates an international ban on production and use of persistent organic pollutants, and most Western countries imposed strict regulation of PCBs and pesticides around 1980. The largest manufacturer of PFOS, 3M, stopped the production of PFOS and related contaminants in the early 2000s. It is consistent with the decline of PFOS in ringed seals since 2004. PFOS or related contaminants were included in the Stockholm Convention in 2009.
Recent studies show that the limits for when immune and endocrine effects may occur are very low in ringed seals. Therefore, there is reason to believe that the level of contaminants can affect the immune and hormonal systems of ringed seals in Svalbard at the molecular level.
There are no set threshold values for the conwenstration of contaminants in ringed seals. The number of animals used for human consumption in Svalbard (Norway) is small. PCBs and chlorinated pesticides are fat-soluble and are therefore mostly in their blubber. The meat contains little pollutants and use of ringed seal meat for consumption has not been linked to high levels of POPs in humans.
Status and trend
Monitoring of ringed seals show that concentrations of fat-soluble organic pollutants (PCB-153, DDE, chlordanes) decreased 6.8 percent per year between 1992 and 2014. This is consistent with the trends seen in other arctic animals, and is a confirmation that international regulation of these pollutants have been successful.
The levels of HCB, α-HCH and toxaphenes in ringed seals from Svalbard also shows a decline in this period. The annual decline has been between 6 and 11 percent.
For the newer POPs, the situation is different. The levels of the brominated flame retardant PBDE-47 show no declining trend in ringed seals from Svalbard from 2004 to 2014, while the levels of PFOS have varied over the period 1990 to 2010, and show no significant trend. The highest PFOS concentrations were measured in 2004, and in 2010 the levels were halved.
Studies from Canada and Greenland show the same as in Svalbard. The old legacy pollutants such as PCBs, DDT, chlordanes and α-HCH decrease in concentration. The studies from Canada, which generally has been going on longer and contains more data than the studies of Svalbard, show that ringed seals today contain significantly less PCB and DDT than they did in the 1970s. At the same time, there are varying trends for the newer environmental toxicants such as brominated flame retardants and perfluoroalkyl and polyfluoroalkyl substances.
A study from 2007 showed that levels of PCBs, brominated flame retardants and pesticides in ringed seals livers is 6-15 times higher in the Baltic Sea than in Svalbard.
Current levels of PCBs, chlorinated pesticides and PFOS in ringed seals are low relative to polar bears.
The main reason why the levels of most of the legacy organic pollutants are decreasing in ringed seals, is that the production and use of them is regulated nationally and internationally.
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 PBDE-47 and PFOS have been restricted in the past years. The largest manufacturer of PFOS, 3M, voluntarily stopped production of PFOS and related substances in the early 2000s. Both the brominated flame retardant PBDE-47 and PFOS were included in the Stockholm Convention in 2009.
Arctic cod is an important prey species for ringed seals, and ringed seals may be influenced by the level of contaminants in polar cod. As mentioned above, the level of contaminants in ringed seals affect the level of pollutants in polar bears, as they are a prey species for polar bears.
Ringed seals from Svalbard have moderate levels of contaminants in their tissues. The levels of PCBs, pesticides and brominated flame retardants is considerably lower in ringed seals from Svalbard than in ringed seals from the Baltic Sea.
Recent studies show that the limits for when immune and endocrine effects may occur are very low in ringed seals. Therefore, there is reason to believe that the concentrations of the contaminants found in ringed seals on Svalbard can affect the immune- and hormonesystem of ringed seals on Svalbard at the molecular level.
Ringed seals can be particularly vulnerable to contaminants when they lose weight during molting. Periods of reductions in body fat allow pollutants stored in their blubber to be released into the blood. Contaminants are then available and taken up in important organs such as the liver and brain.
About the monitoring
The ringed seal is a small species of true seal that is found throughout the Arctic. It is the only seal in Norwegian waters that is capable of keeping breathing holes open in solid ice. In Svalbard, ringed seals have their pups on the ice in the fjords and in the pack ice in the Barents Sea.
The ringed seal is a key species in the plankton – polar cod – ringed seal – polar bear food chain. Ringed seals are monitored to understand how pollutants become concentrated up the food chain.
Places and areas
Relations to other monitoring
International environmental agreements
Voluntary international cooperation
- Facts about the ringed seal
- Management of the Barents Sea and Lofoten (in Norwegian)
- About pollutants – a general introduction (in Norwegian)
- About pollutants in the Arctic (in Norwegian)
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- Severinsen, T., Skaare, J.U., Lydersen, C. 2000. Spatial distribution of persistent organochlorines in ringed seal (Phoca hispida) blubber. Marine Environmental Research 49(3): 291–302. DOI:10.1016/S0141-1136(99)00078-1
- Wolkers, H., Krafft, B.A., van Bavel, B., Helgason, L.B., Lydersen, C., Kovacs, K.M. 2008. Biomarker responses and decreasing contaminant levels in ringed seals (Pusa hispida) from Svalbard, Norway. Journal of Toxicology and Environmental Health, Part A 71(15): 1009–1018. DOI:10.1080/15287390801907558
- Wolkers, J., Burkow, I.C., Lydersen, C., Dahle, S., Monshouwer, M., Witkamp, R.F. 1998. Congener specific PCB and polychlorinated camphene (toxaphene) levels in Svalbard ringed seals (Phoca hispida) in relation to sex, age, condition and cytochrome P450 enzyme activity. Science of The Total Environment 216(1-2): 1–11. DOI:10.1016/S0048-9697(98)00131-4