A Ticking Time Bomb in the Arctic
The pristine white of the Arctic wilderness hides a toxic secret, one that accumulates in the body of its top predator.
The polar bear, an iconic symbol of the Arctic, faces a well-documented threat from the climate crisis and melting sea ice. Less visible, but equally insidious, is the burden of industrial chemicals and legacy pollutants that contaminate its body, despite being thousands of miles from any source.
These contaminants journey on wind and water to the Arctic, where they build up in the food web. As the top predator, the polar bear consumes a highly concentrated chemical cocktail, with potential devastating effects on its health and the ecosystem it calls home.
Key Fact: Polar bears can biomagnify pollutants up to 200 times compared to their prey due to their highly efficient lipid assimilation .
To understand the threat, we must first identify the key chemical invaders. The Arctic environment acts as a sink for a complex mixture of persistent organic pollutants (POPs), substances that resist environmental breakdown and accumulate in living tissue.
These are "old" chemicals, banned or severely restricted decades ago but which persist in the environment. Their levels are generally high in polar bears.
These are substances either still in use or recently regulated.
Research on polar bears from 2005 to 2008 revealed that contamination is not uniform across the Arctic. Levels of these pollutants vary significantly, creating distinct geographic hotspots.
This east-to-west gradient, with higher levels in the European Arctic, is influenced by ocean currents, atmospheric transport patterns, and the historical use of these chemicals. For example, polar bears from Svalbard show approximately three times higher levels of certain PFAS than those from East Greenland or Canada 7 . Meanwhile, the Barents Sea population, shared by Norway and Russia, carries higher average levels of pollutants like PCBs than bears in Greenland or Arctic Alaska 8 .
The primary route of exposure for polar bears is their diet. As a top predator, it feeds predominantly on ringed seals, which themselves consume fish that have ingested contaminated zooplankton. This creates a perfect storm for biomagnification—the process where contaminant concentrations increase at each successive trophic level.
Base level contaminants
Contaminants concentrate
Higher concentration
Maximum concentration
Lipid assimilation efficiency in polar bears
Biomagnification potential in polar bears compared to prey
A 2024 study unveiled just how astonishingly efficient polar bears are at biomagnifying pollutants. The research introduced a non-invasive method to study this process in zoo-housed bears, revealing two key factors :
This combination results in a biomagnification capability—the potential for a chemical to concentrate in the predator compared to its prey—that can be up to 200 times . This means a chemical can be 200 times more concentrated in the polar bear than in the seal it ate.
Long-term monitoring programs, such as those conducted in Svalbard, provide crucial insights into how contaminant levels are changing. By analyzing the blood plasma of adult female polar bears over decades, scientists can track the success of global regulations and identify new threats.
| Contaminant | Long-Term Trend (since 1990s) | Recent Notable Trend |
|---|---|---|
| PCBs (e.g., PCB-153) | Significant decrease (5% per year) 7 | --- |
| PBDEs (e.g., BDE-47) | Significant decrease (3% per year) 7 | --- |
| PFOS (a PFAS) | Decrease (5% per year, 2002-2022) 7 | --- |
| DDE | Decreased until ~2010, then increased 7 | Increase of 21% per year since 2010 7 |
| Hexachlorobenzene (HCB) | Decreased until ~2010, then increased 7 | Increase of 8% per year since 2010 7 |
| Mercury (Hg) | Stable (1995-2023) 7 | Stable 7 |
The data tells a mixed story. On one hand, the decline of PCBs and PBDEs demonstrates the positive impact of international regulations like the Stockholm Convention 1 7 . On the other, the recent rise of DDE and HCB is a stark warning that the movement and recycling of old pollutants in the environment are not fully understood and that climate change may be re-releasing stored contaminants from ice and oceans 4 .
Climate change is not a separate threat; it intensifies the problem of pollution. As the Arctic warms at an alarming rate, it alters the very environment that governs how polar bears interact with these toxins.
With less access to seals, some bears are turning to alternative food sources like bird eggs, reindeer, and vegetation. While this may temporarily reduce the intake of some marine-sourced contaminants, it also leads to poorer body condition and may introduce other pollutants 8 .
Melting glaciers and permafrost may be re-releasing legacy contaminants that were trapped for decades, creating a second wave of pollution 4 .
The story of flame retardants and legacy contaminants in polar bears is a powerful reminder that our actions have far-reaching consequences. The toxins used decades ago, or in products far from the Arctic, continue to haunt this remote ecosystem.
The good news is that regulation works, as shown by the declining levels of regulated PCBs and PBDEs. However, the emergence of new chemicals and the unsettling resurgence of others demand continued vigilance. Protecting the polar bear requires a dual strategy: urgent action on climate change to preserve their sea-ice habitat and robust global policies to eliminate the production and release of persistent toxic chemicals. The health of the Arctic's top predator is a barometer for the health of the entire planet.
To follow the latest research and monitoring data, you can explore resources provided by the Norwegian Polar Institute's MOSJ (Environmental monitoring of Svalbard and Jan Mayen) 7 .