Ringed seals are among the most common marine mammals in the Canadian Arctic. They strongly rely on sea ice as a habitat, breathing through holes they maintain in the frozen surface, giving birth in snow lairs and diving beneath the ice to hunt Arctic cod and small crustaceans.They are also a key prey for polar bears and an integral part of Inuit culture, providing nutrition, cultural continuity and a generations-long connection to land and sea.However, our new study shows these seals are being affected by chemical pollution in the Arctic food web and rapid climate-driven warming that is transforming their sea ice habitat. Each of these pressures is serious on its own, but together they are undermining seal health in ways now detectable at the molecular level. Our research focused on ringed seals along the northern Labrador coast of Canada, near Saglek Bay, a site with a long industrial legacy. A former military radar station operating since the 1950s left behind a hotspot of polychlorinated biphenyls (PCBs) that has impacted the ringed seal.A chemical legacy stored in fatPCBs are 209 chlorine-based chemical compounds that are highly toxic. They were produced in large quantities worldwide from the 1920s to late 1970s for use in industrial electrical equipment and commercial products.Despite being banned for decades, they still remain highly persistent in the environment. PCBs do not break down easily. They bind to fat, move through food webs and accumulate in animals like seals, whales, and ultimately, people who rely on marine mammals for food.When we sampled seals near Saglek Bay between 2009 and 2011, PCB concentrations remained high, averaging over 700 nanograms per gram of blubber fat. Alongside PCBs, we also detected residues of the insecticide DDT, chlordanes, dieldrin, mercury and other persistent pollutants that were transported into the Arctic through the air and water.To understand how this chemical burden affects seal biology, we used metabolomics (a scientific method that studies small molecules in tissues) to reveal changes in physiology and cellular function. By measuring 254 molecules in blood and liver samples, we can detect early signs of stress that may not be visible in traditional health assessments.How chemicals are harming sealsWe found that exposure to chemical pollutants is disrupting seals’ core metabolism. In the liver, seals with higher PCB levels showed increased concentrations of methionine sulfoxide, a marker of oxidative stress. This compound forms when proteins are damaged by reactive oxygen species, which are produced when cells are exposed to chemical stress. This suggests that PCBs are contributing to oxidative damage at the cellular level.Chlordanes were associated with disruptions in amino acid metabolism that supports protein synthesis and waste processing. Seals with higher levels of these pesticides showed reduced glutamine, an amino acid important for detoxification and immune function, along with shifts in other metabolic markers that indicate physiological compensation under stress.These changes are not just biochemical signals. Oxidative stress and disrupted amino acid metabolism are linked to reduced immune function, hormonal imbalance, lower reproductive success, and over time, increased disease risk. Earlier work in these same populations has also shown changes in gene expression associated with contaminant exposure. Our findings suggest these effects are also manifesting at the metabolic level.Environmental shocks from a warming oceanClimate change adds another layer of stress. In 2009 and 2010, the Labrador Sea experienced unusually warm winter conditions, with sea surface temperatures ranging from 5 C to 10 C above normal and a sharp decline in sea ice cover. This represented a short but strong shift in environmental conditions.Seal blood samples we collected from that year showed marked changes in lipid composition. Essential omega-3 and omega-6 fatty acids, which are critical for cell membranes, regulating inflammation and neurological function, were significantly reduced. At the same time, levels of saturated fats increased, indicating either changes in diet, altered energy use or physiological stress.This biochemical shift was mirrored in body condition. Adult seals we sampled in 2010 had significantly thinner layers of blubber compared with other years. Because blubber serves as both insulation and an energy reserve, reduced thickness indicates decreased energy intake, increased energetic demand or both.These two stressors do not act independently. When seals lose blubber during periods of poor food supplies or warm conditions, contaminants stored in fat such as PCBs and chlordanes can be released into the bloodstream.This means that nutritional stress can directly increase internal exposure to toxic chemicals. The result is a compounding effect: animals under climate stress may simultaneously experience higher toxic exposure. This dynamic is especially concerning for young seals building fat reserves and for adult females nursing their pups.Implications for Inuit communitiesRinged seals are not only important to the Arctic ecosystem, they also serve as a critical food source for Inuit communities across the region. Changes in the health of ringed seals directly affect food security, traditions and overall well-being of these communities.The sources of these contaminants lie far outside local control. Industrial pollutants such as PCBs were produced and released in southern regions, while greenhouse gas emissions driving Arctic warming come from sources around the world. Yet Arctic communities often experience the greatest impact of both.Ringed seals remain vital to Inuit traditional diets due to their cultural importance, nutritional density and greater affordability and nutrition compared to store-bought alternatives.A changing climate that is affecting both the health of seals and their exposure to contaminants highlights the need to monitor and protect the safety and quality of traditional foods.What remains unknownMetabolomics offer valuable insights into physiological changes in animals. But in complex systems, it can be challenging to distinguish the effects of specific contaminants from other changing biological or environmental factors.Long-term monitoring of animals, combined with experimental studies on contaminants and real-world mixtures, helps clarify how specific chemicals drive these effects.What is already clear, however, is that both climate and chemical stressors are associated with compromised health in seals. The liver signals ongoing detoxification stress, while the blood indicates changes in energy balance as the climate warms.Ringed seals have survived past climate fluctuations, but they have not faced the combined challenges of rapid human-driven warming and persistent industrial pollution. Monitoring their health provides not only insight into Arctic ecosystems, but also an early warning system for the communities that depend on them.Tanya Brown receives funding from the Northern Contaminants Program. Anaïs Remili does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.