Plastic Chemicals Found in Whales Raise New Concerns About Ocean Health

UC Davis researchers discover plasticizers in southern right whales—including calves—highlighting an invisible threat to marine mammals.

When most people think about plastic pollution, they picture floating bottles, discarded fishing nets, or beaches covered in trash. While these images represent a visible environmental crisis, scientists say an even greater threat may be hiding beneath the surface.

A new study involving researchers from the UC Davis Weill School of Veterinary Medicine has found plasticizers—chemicals added to plastics to make them softer and more flexible—in the blubber of southern right whales (Eubalaena australis). Even more concerning, researchers detected these chemicals in whale calves, suggesting exposure begins early in life.

Published in the journal Polar Biology, the study is the first to document phthalate exposure in southern right whales and the first to demonstrate that these chemicals accumulate in calves. Researchers found measurable levels of phthalates in more than 90% of the whales tested.

The findings add to growing evidence that plastic pollution extends far beyond the debris visible on the ocean's surface. Invisible chemical contaminants are moving through marine food webs and reaching some of the largest and most iconic animals on Earth.

What Are Plasticizers?

Plasticizers are chemicals used to increase the flexibility, durability, and longevity of plastics. One of the most common groups is phthalates, which are found in thousands of everyday products.

These chemicals can be present in:

• Food packaging

• Vinyl flooring

• Medical tubing

• Toys

• Personal care products

• Household goods

• Building materials

Unlike some ingredients that remain chemically bound within plastic products, many plasticizers slowly leach into the surrounding environment over time.

Once released, they can enter rivers, lakes, and oceans, where they are absorbed by marine organisms and move up the food chain.

Unlike plastic bottles or bags that can be collected during beach cleanups, these chemicals are essentially invisible, making them much more difficult to monitor and remove.

A Long-Term Whale Health Program Makes the Discovery Possible

The study was made possible through Argentina's Southern Right Whale Health Monitoring Program, a collaborative effort that has investigated whale deaths and collected biological samples at Península Valdés for more than 20 years.

Long-term monitoring programs like this are invaluable because they allow scientists to detect emerging environmental threats that would otherwise go unnoticed.

Whenever whales strand or die naturally, veterinary pathologists and wildlife health experts carefully examine the animals and collect tissue samples. These investigations help researchers understand causes of death, disease patterns, nutritional status, infectious diseases, and exposure to environmental contaminants.

By analyzing blubber samples collected over many years, researchers identified phthalates in the overwhelming majority of whales examined.

Perhaps the most alarming finding was that whale calves also contained these chemicals.

Because calves spend their earliest months nursing from their mothers and living in relatively protected nursery habitats, scientists believe contamination may be transferred from mother to calf during pregnancy or through milk.

Additional research will be needed to determine exactly how exposure occurs and what health effects it may have.

Why Blubber Matters

Whale blubber is much more than insulation.

This thick layer of fat stores energy, regulates body temperature, supports migration, and plays an important role in metabolism.

It also acts as a reservoir for many environmental contaminants.

Because fat-soluble chemicals accumulate in blubber over time, scientists often analyze these tissues to understand long-term exposure to pollutants.

Finding plasticizers in blubber suggests whales are experiencing ongoing exposure throughout their lives rather than brief, isolated encounters.

What Do These Chemicals Do?

Researchers are still working to understand the full impact of phthalates on marine mammals.

In laboratory animals and humans, some phthalates have been associated with:

• Hormonal disruption

• Reproductive abnormalities

• Developmental changes

• Altered metabolism

• Immune system effects

Whether these same effects occur in whales remains unknown.

Marine mammals have very different physiology from humans, and much more research is needed before scientists can determine the clinical significance of the concentrations detected.

However, wildlife health experts say the findings deserve careful attention.

When contaminants become widespread throughout an ecosystem, they may interact with other stressors such as climate change, declining food availability, ship strikes, fishing gear entanglement, and infectious disease.

Together, these cumulative pressures can influence the health and resilience of whale populations.

Whales as Sentinels of Ocean Health

Marine veterinarians often describe whales as "sentinel species."

Just as canaries once warned miners about dangerous gases, whales can provide early warning signs of problems affecting the broader marine environment.

Because southern right whales are long-lived, migrate across vast distances, and feed high in the marine food web, contaminants accumulating in their tissues may reflect widespread environmental conditions.

As corresponding author Dr. Marcela Uhart of UC Davis explains, studying whale health helps scientists understand larger ecological challenges.

The discovery reinforces an important message: cleaning up visible plastic waste is only part of the solution.

Reducing chemical pollution requires changes throughout the life cycle of plastics—from manufacturing and product design to recycling, waste management, regulation, and consumer choices.

A One Health Perspective

The study also highlights the importance of the One Health approach, which recognizes the close connection between environmental, animal, and human health.

Many of the chemicals detected in whales originate from products people use every day.

Once released into the environment, they circulate through ecosystems that support fisheries, coastal communities, wildlife, and ultimately human populations.

Veterinarians increasingly play an important role in identifying these emerging environmental threats through wildlife surveillance, toxicology research, and conservation medicine.

The health of marine mammals often reflects the health of the oceans themselves.

Looking Ahead

Scientists emphasize that this study represents an important first step rather than a final answer.

Future research will investigate whether plasticizer concentrations are changing over time, how these chemicals affect whale reproduction and immune function, and whether similar contamination exists in other whale species around the world.

As concerns about plastic pollution continue to grow, the discovery serves as a reminder that some of the greatest environmental threats cannot be seen with the naked eye.

The ocean may appear clean from the surface, but invisible contaminants are quietly accumulating inside the animals that depend on it.

For veterinarians, conservationists, and policymakers, protecting marine wildlife will require addressing not only the plastics we can see—but also the chemicals we cannot.

Key Takeaways

• Researchers detected plasticizers in more than 90% of southern right whales tested.

• Whale calves also contained phthalates, suggesting exposure begins early in life.

• The study represents the first documented evidence of phthalate accumulation in this species.

• Whale blubber provides valuable information about long-term environmental contamination.

• Scientists say reducing plastic pollution requires addressing both visible debris and invisible chemical contaminants.

• The findings reinforce the importance of wildlife monitoring and the One Health approach to protecting ecosystems.

Source: UC Davis Weill School of Veterinary Medicine, IBIOMAR, and the Southern Right Whale Health Monitoring Program. Study published in Polar Biology.