Polar bears (Ursus maritimus) are apex predators that play a fundamental role in maintaining the ecological balance of Arctic marine ecosystems. As the dominant predators within the Arctic food web, they regulate seal populations and serve as important indicators of ecosystem health.

Although polar bears are widely recognized as one of the species most severely affected by climate change, environmental pollution has emerged as an additional and increasingly significant threat to their survival. Persistent pollutants released through industrial and agricultural activities are transported thousands of kilometres by atmospheric and oceanic currents before accumulating in the Arctic. Once introduced into the marine food web, ultimately reaching their highest concentrations in apex predators such as polar bears.

This report examines two major forms of anthropogenic pollution affecting polar bears: persistent organic pollutants that accumulate, disrupting reproductive health, and plastic pollution—threatening polar bears through entanglement, ingestion, and increasing exposure to anthropogenic debris.

Understanding the origin and movement of pollutants is essential for evaluating their effects on polar bears. Despite the Arctic’s remote location, much of its pollution originates in heavily industrialized and agricultural regions located thousands of kilometres to the south. These contaminants are transported northward through large river systems, atmospheric circulation, and ocean currents before being deposited throughout the Arctic environment (Pollution, n.d.). Consequently, even ecosystems that experience relatively little direct human activity become contaminated by pollutants generated elsewhere. Among the most significant contaminants are organochlorines, a class of persistent organic pollutants (POPs) historically used as industrial chemicals and agricultural pesticides. A defining characteristic of these compounds is their exceptional resistance to chemical and biological degradation, allowing them to remain in the environment for decades after their release (Pollution, n.d.). Their persistence enables them to travel vast distances and continuously accumulate within Arctic ecosystems. Polychlorinated biphenyls (PCBs) were extensively utilised in electrical equipment and numerous industrial applications because of their remarkable chemical stability. Similarly, pesticides including DDT, dieldrin, toxaphene, and chlordanes were designed to resist environmental degradation, allowing them to remain effective for prolonged periods. Although many of these chemicals have since been banned or heavily restricted in numerous countries, their persistence means they continue to contaminate Arctic ecosystems decades after their initial release (Pollution, n.d.).

The harmful effects of organochlorines are further intensified by their strong affinity for lipids (fat). Fat plays a critical role in Arctic marine organisms by providing insulation against extreme cold, maintaining buoyancy, and serving as an essential energy reserve. Because organochlorines readily accumulate in fatty tissues, they become increasingly concentrated as they move through each trophic level of the food web (Pollution, n.d.).

As organisms consume contaminated prey, pollutant concentrations progressively increase until they reach their highest levels in apex predators. Polar bears are particularly vulnerable because their diet consists primarily of the blubber from ringed, harp, and other seal species. This continual accumulation places them at an elevated risk of reproductive impairment. Understanding how persistent pollutants affect the reproductive physiology of polar bears is essential because the species possesses one of the slowest reproductive rates among terrestrial mammals. Polar bears are seasonal breeders that exhibit delayed implantation and typically give birth to only one or two cubs following successful mating (Sonne et al., 2006, p. 5668). Because reproductive success depends on precise hormonal regulation and favourable environmental conditions, even minor physiological disturbances can significantly reduce population growth.

One of the greatest concerns is the ability of organochlorines and other organohalogen compounds to function as endocrine-disrupting chemicals. These pollutants interfere with the hypothalamic-pituitary-target organ axis, the hormonal system responsible for regulating reproductive development and function. Proper reproductive function depends upon the precise coordination between endocrine signalling and immune processes. When endocrine-disrupting chemicals interfere with this coordination, reproductive organs may develop abnormally or function less effectively, reducing fertility in both males and females (Sonne et al., 2006, p. 5668).

Exposure to anthropogenic organhalogen compounds including organochlorines and brominated flame retardants has been associated with numerous reproductive abnormalities across mammalian species. In males, these contaminants have been linked to reduced sperm counts, abnormal sperm morphology, and impaired testicular function. In females, they have been associated with reproductive tract disorders such as endometriosis, leiomyomas, uterine occlusions, and stenosis, all of which may reduce reproductive success and decrease offspring survival (Sonne et al., 2006, p. 5668). Such reproductive impairments are particularly concerning for polar bears because their naturally low reproductive rate limits their ability to recover from population declines.

To investigate these effects directly, Sonne et al. (2006) examined the reproductive organs of 55 male and 44 female East Greenland polar bears. After accounting for age, statistical analyses revealed significant relationships between organohalogen contaminant concentrations and reproductive characteristics. In males, higher concentrations of dichlorodiphenyl trichloroethanes (DDTs), dieldrin, chlordanes, hexachlorocyclohexanes, and polychlorinated biphenyls (PCBs) were associated with reductions in testis length as well as baculum length and weight. Bone mineral density within the baculum also decreased as concentrations of chlordanes, DDTs, and hexachlorobenzene (HCB) increased among both subadult and adult bears. Female polar bears exhibited significant inverse relationships between contaminant concentrations and ovary length, ovary weight, and uterine horn length (Sonne et al., 2006, p. 5668).

In addition to persistent organic pollutants, plastic pollution has emerged as another significant anthropogenic threat to Arctic ecosystems. The rapid expansion in the production and use of plastic materials has resulted in increasing quantities of plastic debris entering terrestrial and marine environments (Lusher et al., 2022). Plastics consist of numerous polymer types and chemical additives that differ in their physical and chemical properties, environmental persistence, and toxicity. Consequently, different plastic materials may produce varying effects on ecosystems, wildlife, and human health (Lusher et al., 2022). Understanding the types, sources, and distribution of plastic within Arctic environments is therefore essential for assessing ecological risks and developing effective mitigation and remediation strategies (Lusher et al., 2022).

Plastic pollution affects wildlife primarily through entanglement and ingestion. Marine mammals, birds, and other Arctic species frequently become entangled in discarded fishing gear, ropes, nets, and other large plastic debris. These interactions can result in severe lacerations, restricted movement, impaired feeding, infection, starvation, and in marine mammals, drowning when individuals are unable to reach the surface to breathe (Lusher et al., 2022). Ingestion of plastic debris presents an additional threat because plastic fragments can obstruct or damage the digestive tract. Obstruction of the intestines would reduce nutrient absorption, and ultimately lead to malnutrition or death (Kühn, 2015, as cited in Lusher et al., 2022). Evidence also suggests that polar bears are increasingly exposed to plastic debris through ingestion. Plastic and other anthropogenic debris were identified in the stomachs of approximately 25% of harvested polar bears in Alaska, while additional plastic materials have been documented within the gastrointestinal tracts of polar bears from Nunavut, Canada (Lusher et al., 2022).

Furthermore, researchers observed polar bear feces containing substantial quantities of polystyrene debris near abandoned cabins in Franz Josef Land, indicating that bears are directly consuming plastic waste within Arctic environments (Lusher et al., 2022). These findings provide clear evidence that plastic ingestion is occurring across multiple regions of the Arctic. Despite these observations, researchers acknowledge that significant knowledge gaps remain regarding the extent of plastic accumulation within polar bear populations (Lusher et al., 2022) suggesting that polar bears may currently ingest relatively small quantities of plastic through their primary prey because seals retain little plastic within their digestive systems.

However, it was also emphasized that too few studies have examined seal populations across the Arctic to confirm this hypothesis. Consequently, additional research is required before the magnitude of secondary plastic exposure through the Arctic food web can be fully understood. Climate change may further increase the risk of plastic exposure in the future. As declining sea ice alters prey availability, polar bears have begun expanding their diets and spending more time on land, increasing the likelihood of encountering human-generated waste (McKinney et al., 2013; Lippold et al., 2019, as cited in Lusher et al., 2022). Indigenous harvesters in Nunavut have reported frequent observations of polar bears feeding at landfills and near urban settlements where they may consume plastic debris along with other refuse (Lusher et al., 2022).

Hunters have also documented plastics and other debris within polar bear stomach contents and scat, providing further evidence that human activities are increasing opportunities for plastic ingestion throughout the Arctic.

Although climate change remains the greatest long-term threat to polar bears, pollution represents another significant anthropogenic stressor that compounds the challenges facing Arctic populations. Persistent organic pollutants accumulate, reaching exceptionally high concentrations in polar bears and disrupting endocrine function, reproductive development, and fertility. At the same time, plastic pollution has emerged as a growing threat through entanglement, ingestion, and increasing exposure associated with changing feeding behaviours. Together, these forms of pollution reduce individual health, reproductive success, and ultimately the resilience of polar bear populations. Continued international efforts to reduce persistent pollutants and plastic waste, combined with long-term monitoring of Arctic ecosystems, will be essential for conserving polar bears and protecting the ecological integrity of one of the world’s most vulnerable environments.

References:

Lusher, A. L., Provencher, J. F., Baak, J. E., Hamilton, B. M., Vorkamp, K., Hallanger, I. G., Pijogge, L., Liboiron, M., Bourdages, M. P. T., Hammer, S., Gavrilo, M., Vermaire, J. C., Linnebjerg, J. F., Mallory, M. L., & Gabrielsen, G. W. (2022). Monitoring litter and microplastics in Arctic mammals and birds. Arctic Science, 8(4), 1217–1235. https://doi.org/10.1139/AS-2021-0058

Polar Bears International. (n.d.). Polar bears and the chemical cocktail. Retrieved June 26, 2026, from https://polarbearsinternational.org/news-media/articles/polar-bears-ocean-chemicals-toxic-pollution/

Polar Bear Specialist Group. (n.d.). Pollution. Retrieved June 26, 2026, from https://www.iucn-pbsg.org/pollution/

Sonne, C., Leifsson, P. S., Dietz, R., Born, E. W., Letcher, R. J., Hyldstrup, L., Riget, F. F., Kirkegaard, M., & Muir, D. C. G. (2006). Xenoendocrine pollutants may reduce size of sexual organs in East Greenland polar bears (Ursus maritimus). Environmental Science & Technology, 40(18), 5668–5672. https://doi.org/10.1021/es060836n