MOSJInfluencePollutionPollutants in ringed seals

Pollutants in ringed seals

Last updated 12 November 2024

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 legacy contaminants are decreasing in ringed seal.

Pollutants in ringed seals
Photo: Bjørn Frantzen / Norwegian Polar Institute

What is being monitored?

Persistent organic pollutants in ringed seals

The figure shows a sharp reduction of polychlorinated biphenyls (PCB)-153, dichlorodiphenyldichloroethylene (DDE) and chlordane (sum of transnonachlor and oxychlordan) levels measured in ringed seal blubber in the period 1992-2020. Concentrations are given as geometric means with 95% confidence intervals.
(Cite these data: Norwegian Polar Institute (2024). 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), sum of alpha- and beta-hexachlorocyclohexane (HCH) and toxaphenes (sum of congeners 26 and 50) in ringed seal from Svalbard show a decline since the 1990s.  The levels of the brominated flame retardant BDE-47 shows no change between 2004 and 2014 in ringed seals from Svalbard. Concentrations are given as geometric means with 95% confidence intervals.
(Cite these data: Norwegian Polar Institute (2024). 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 perfluorooctasulfonate (PFOS) measured in the plasma of ringed seals over the period 1990-2010. The highest levels were measured in 2004, and in 2010 levels were halved. The levels of the sum of long-chain perfluorinated carboxylic acids (PFCA) increased from 1990-2010. Concentrations are given as geometric means with 95% confidence intervals.
(Cite these data: Norwegian Polar Institute (2024). 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 updated12 November 2024
Update intervalEvery 10th year
Next updateMarch 2026
Commissioning organizationMinistry of Climate and Environment
Executive organizationNorwegian Polar Institute
Contact personsHeli Routti

Method

Individual blubber or plasma 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 1990-2020 consists of animals that are a mix of males and females at varying ages. Samples are taken from 6 to 19 individuals per year. Localities for seals analysed 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 analysed 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.

Quality

The laboratories are quality assured and accredited. The work is carried out in accordance with AMAP’s guidelines for sampling and analysis. The laboratories regularly participate in international ring tests.

Other metadata

The Norwegian Polar Institute has all metadata.

Reference level and action level

Since both PCBs, pesticides, brominated flame retardants and perfluorinated compounds is manmade pollutants, and do not occur naturally, the reference value for an unaffected state is zero (actually the detection limit).

Levels of environmental toxins in ringed seals from Svalbard are significantly lower compared to limit values ​​for harmful effects of environmental toxins defined by AMAP.

There are no set threshold values for the concenstration of contaminants in ringed seals. The number of animals used for human consumption in Svalbard is small. PCBs and chlorinated pesticides are fat-soluble and are therefore mostly in their blubber.  The European Food Safety Authority has set a limit value for tolerable weekly intake of PFAS of 4.4 ng/kg body weight. It describes the amount of substance a person can take in weekly throughout their life without risk of negative health effects. Based on levels of PFAS measured in the muscle of ringed seals from East Greenland, collected in 2018-2019, this means that consumption of ringed seal meat should not be more than 100 g of meat per week for a person of 70 kg.

Status and trend

Geographic trends

Ringed seals from Svalbard have approximately equal levels of PCB-153, DDE and HCB and somewhat lower HCH (sum of α- and β-HCH) and chlordane levels than ringed seals from Canada (Facciola et al., 2022), and most of these substances are lower in ringed seals from Svalbard than in ringed seals from East Greenland. Studies from 2007 showed that levels of PCBs, brominated flame retardants and pesticides in the liver of ringed seals are 6-15 times higher in the Baltic Sea than in Svalbard.

Species trends

Today’s levels of PCBs, chlorinated pesticides and PFAS in ringed seals are low compared to polar bears.

Time trends

Monitoring of ringed seals shows that the concentrations of fat-soluble organic pollutants PCB-153 and chlorinated pesticides DDE, chlordanes, HCB and HCH have decreased in the period 1990-2020, but the decrease in PCB-153 and DDE has stabilized in the last half of the study period. The levels of another chlorinated pesticide group, toxaphenes, also show a decrease between the measurements in 2004 and 2014.

The levels of the flame retardant BDE-47 show no difference in ringed seals from Svalbard collected in 2004 and 2014, while the levels of PFOS have varied in the period 1990-2010, and show no significant trend. The highest PFOS levels were measured in 2004, in 2010 the levels had halved.

Causal factors

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 substances do not exist any longer.

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.

The production and use of other contaminants such as BDE and PFOS has been restricted in the last 15-20 years. Tetra-BDE, penta-BDE, hexa-BDE, hepta-BDE and PFOS were included in the Stockholm Convention in 2009, while deca-BDE was included in 2017. The largest producer of PFOS, 3M, stopped production of PFOS and related substances early in the 2000s. The PFCA have been proposed to be included in the Stockholm Convention and production has decreased in many countries, but many of their precursors are not regulated as of today.

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.

Consequences

Ringed seals from Svalbard have moderate levels of contaminants in their tissues.

Levels of environmental toxins in ringed seals are generally lower compared to limit values ​​for harmful effects of environmental toxins defined by AMAP. However, some correlative studies show that the threshold values ​​for when changes in gene expression can occur are very low in ringed seals, while experimental studies indicate that the ringed seal’s immune system is not weakened by the current contaminant load.

Ringed seals are particularly vulnerable to fat soluble 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

Monitoring programme

  • None

International environmental agreements

Voluntary international cooperation

Related monitoring

  • None

Other

Further reading

Links

Publications

  1. AMAP. (2016). AMAP Assessment 2015: Temporal Trends in Persistent Organic Pollutants in the Arctic. Arctic Monitoring and Assessment Programme (AMAP), Oslo, Norway.
  2. AMAP. (2021). AMAP Assessment 2020: POPs and Chemicals of Emerging Arctic Concern: Influence of Climate Change. Arctic Monitoring and Assessment Programme (AMAP), Tromsø, Norway
  3. Brown, T.M., Ross, P.S., Reimer, K.J., Veldhoen, N., Dangerfield, N.J., Fisk, A.T., & Helbing, C.C. (2014). PCB Related Effects Thresholds As Derived through Gene Transcript Profiles in Locally Contaminated Ringed Seals (Pusa hispida). Environmental Science & Technology 48(21), 12952-12961. https://doi.org/10.1021/es5032294.
  4. Daelemans, F.F., Mehlum, F., Lydersen, C., & Schepens, P.J.C. (1993). Mono-ortho and non-ortho substituted PCBs in Arctic ringed seal (Phoca hispida) from the Svalbard area: Analysis and determination of their toxic threat. Chemosphere 27(1-3): 429–437. https://doi.org/10.1016/0045-6535(93)90323-W.
  5. Desforges, J.-P.W., Sonne, C., Levin, M., Siebert, U., De Guise, S., & Dietz, R. (2016). Immunotoxic effects of environmental pollutants in marine mammals. Environment International 86, 126-139. https://doi.org/10.1016/j.envint.2015.10.007.
  6. EFSA Panel on Contaminants in the Food Chain (EFSA CONTAM Panel), Schrenk, D., Bignami, M., Bodin, L., Chipman, J. K., del Mazo, J., … & Schwerdtle, T. (2020). Risk to human health related to the presence of perfluoroalkyl substances in food. EFSA journal, 18(9), e06223. https://doi.org/10.2903/j.efsa.2020.6223.
  7. Facciola, N., Houde, M., Muir, D.C.G., Ferguson, S.H., & McKinney, M.A. (2022). Feeding and contaminant patterns of sub-arctic and arctic ringed seals: Potential insight into climate change-contaminant interactions. Environmental Pollution 313, 120108. https://doi.org/10.1016/j.envpol.2022.120108.
  8. Hanssen, L., Dudarev, A.A., Huber, S., Odland, J.O., Nieboer, E., Sandanger, T.M., 2013. Partition of perfluoroalkyl substances (PFASs) in whole blood and plasma, assessed in maternal and umbilical cord samples from inhabitants of arctic Russia and Uzbekistan. Science of the Total Environment 447, 430-437. https://doi.org/10.1016/j.scitotenv.2013.01.029.
  9. Houde, M., Wang, X., Colson, T. L., Gagnon, P., Ferguson, S. H., Ikonomou, M. G., … & Muir, D. C. G. (2019). Trends of persistent organic pollutants in ringed seals (Phoca hispida) from the Canadian Arctic. Science of the Total Environment, 665, 1135-1146. https://doi.org/10.1016/j.scitotenv.2019.02.138.
  10. Muir, D., Riget, F., Cleemann, M., Skaare, J., Kleivane, L., Nakata, H., … & Tanabe, S. (2000). Circumpolar trends of PCBs and organochlorine pesticides in the Arctic marine environment inferred from levels in ringed seals. Environmental science & technology, 34(12), 2431-2438. https://doi.org/10.1021/es991245i.
  11. Routti, H., Gabrielsen, G.W., Herzke, D., Kovacs, K.M., & Lydersen, C. (2016). Spatial and temporal trends in perfluoroalkyl substances (PFASs) in ringed seals (Pusa hispida) from Svalbard. Environmental Pollution 214. https://doi.org/10.1016/j.envpol.2016.04.016.
  12. Routti, H., Arukwe, A., Jenssen, B.M., Letcher, R.J., Nyman, M., Backman, C., & Gabrielsen, G.W. (2010). Comparative endocrine disruptive effects of contaminants in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 152(3): 306–312. https://doi.org/10.1016/j.cbpc.2010.05.006.
  13. Routti, H., Letcher, R.J., Arukwe, A., van Bavel, B., Yoccoz, N.G., Chu, S., & Gabrielsen, G.W. (2008). Biotransformation of PCBs in relation to phase I and II xenobiotic-metabolizing enzyme activities in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea. Environmental Science & Technology 42(23): 8952–8958. https://doi.org/10.1021/es801682f.
  14. Quinn, C.L., Armitage, J.M., Breivik, K., & Wania, F. (2012). A methodology for evaluating the influence of diets and intergenerational dietary transitions on historic and future human exposure to persistent organic pollutants in the Arctic. Environment International, 49, 83-91. https://doi.org/10.1016/j.envint.2012.08.014.
  15. 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. https://doi.org/10.1016/S0141-1136(99)00078-1.
  16. Sonne, C., Desforges, J. P., Gustavson, K., Bossi, R., Bonefeld-Jørgensen, E. C., Long, M., … & Dietz, R. (2023). Assessment of exposure to perfluorinated industrial substances and risk of immune suppression in Greenland and its global context: a mixed-methods study. The Lancet Planetary Health, 7(7), e570-e579. https://doi.org/10.1016/S2542-5196(23)00106-7.
  17. 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. https://doi.org/10.1080/15287390801907558.
  18. 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. https://doi.org/10.1016/S0048-9697(98)00131-4.