Hidden Toxins Beneath the Waves
Dolphins living in polluted waters may be growing biologically older faster than expected.
New research suggests that exposure to certain trace metals and long-lasting industrial chemicals could accelerate the aging process in common dolphins. The findings raise concerns not only for marine wildlife, but also for humans who share many of the same environmental exposures.
Among the substances examined were metals such as zinc, copper and selenium, along with per- and polyfluoroalkyl substances, commonly known as PFAS or “forever chemicals.”
These pollutants can enter oceans through industrial waste, mining, firefighting foams and everyday consumer products.
Why Forever Chemicals Are So Dangerous
PFAS are known for their remarkable resistance to breaking down.
Once released into the environment, they can remain in water, soil and living organisms for years. As animals eat contaminated prey and move through polluted habitats, the chemicals can gradually accumulate inside their bodies.
Previous studies have linked PFAS exposure in dolphins to damage involving the liver, kidneys and immune system.
Researchers have also found that mother dolphins can transfer some of these chemicals to their calves through milk, meaning exposure may begin during the earliest stages of life.
Calendar Age Versus Biological Age
A dolphin’s chronological age is simply the number of years it has lived.
Biological age, however, reflects the condition of its cells and DNA. Two animals of the same chronological age may have very different biological ages depending on their health, environment and exposure to stress.
Pollution, disease and other external pressures can speed up biological aging.
When this happens, illnesses normally associated with later life—such as cancer and chronic disease—may appear earlier than expected.
Studying Decades of Dolphin Samples
Researchers examined liver and kidney tissue collected from 75 common dolphins that died from unrelated causes between 2000 and 2023.
They measured the concentration of various metals and PFAS compounds in the tissues, then compared those levels with the dolphins’ chronological and biological ages.
The scientists initially expected the overall amount of contamination to explain the accelerated aging.
Instead, they discovered that specific pollutants appeared to matter more than the total toxic burden.
The study was released as a preprint and had not yet completed peer review at the time of publication.
Certain Chemicals Stood Out
One of the strongest associations involved PFBA, a PFAS compound used in products including nonstick materials and firefighting foams.
Another chemical, PFNA, was also connected to accelerated aging. Previous research has identified a similar association in humans.
This suggests that the risks may depend less on how much PFAS is present overall and more on which individual compounds have accumulated.
Because the PFAS family includes thousands of different substances, each chemical may affect the body in a different way.
Essential Metals Can Become Harmful
Several trace metals were also associated with faster biological aging.
Selenium showed the strongest relationship. Although the body requires small amounts of selenium for normal biological functions, high concentrations can become toxic.
Zinc, copper, aluminum and manganese were also linked to the aging difference.
Together, the selected metals and PFAS compounds accounted for more than half of the accelerated aging observed in the dolphins.
Pollutants Rarely Act Alone
In the natural world, animals are almost never exposed to a single contaminant.
Dolphins may carry a mixture of PFAS, metals, plastics, pesticides and other chemicals at the same time. These substances may interact with one another, creating health effects that are more complicated than those caused by any individual pollutant.
Understanding these combined effects will be an important focus of future research.
Scientists also need to determine whether contaminants can harm organs and biological systems far beyond the tissues where they initially collect.
What Dolphins May Reveal About Human Health
Dolphins are often studied as indicators of environmental risks to people.
Like humans, they are long-lived mammals that breathe air, consume seafood and gradually accumulate pollutants over time.
Their health can therefore offer an early warning about contaminants moving through shared marine food chains.
Although the findings do not prove that the same effects will occur in humans, they add to growing concerns that prolonged exposure to certain PFAS compounds and metals may influence aging and disease.
A Warning Written in Their Cells
Dolphins may appear healthy as they move through the ocean, but their DNA can preserve evidence of the pollution surrounding them.
The possibility that contamination is quietly speeding up their aging reveals how deeply human-made chemicals can affect marine life.
Their changing biology is more than a wildlife concern. It may be a reflection of the same environmental dangers reaching coastlines, seafood and communities around the world.