Forever chemicals move through the food web and end up in the bodies of high-level predators such as dolphins. Credit: Unsplash/CC0 Public Domain
Whales and dolphins inhabit some of the largest and seemingly most pristine environments on Earth, from tropical coastlines to Antarctic waters. Yet even they cannot escape PFAS—persistent "forever chemicals" that leak from our homes, factories and waterways into the sea.
Forever chemicals are the secret ingredients in our nonstick pans, waterproof jackets and stain-resistant carpets. These chemicals belong to a group of more than 1,400 compounds known as PFAS (per- and polyfluoroalkyl substances). They enter the environment through manufacturing waste, industrial runoff, wastewater treatment plants and firefighting foams. But once these chemicals escape our homes and factories, they become almost impossible to get rid of. Washed into waterways, they make their way to the sea.
Small organisms absorb them from the water, fish eat those organisms, and larger predators eat the fish. At each step, the chemical load increases. As top predators, whales and dolphins can end up with very high levels in their bodies. Not even deep-diving species living and feeding far from humans are safe .
In our new research , we found PFAS concentrations in cetaceans have increased globally since 2000. Animals in the Pacific Ocean were the most contaminated, with humpback dolphins showing the highest PFAS concentrations.
These mammals are sentinels of ocean health. They sit high in the food web, live for many years and are exposed to pollution across large areas of the ocean. When whales and dolphins show signs of chemical exposure, it tells us something is wrong in the wider marine ecosystem.
Infographic showing the main findings of the study. Credit: CC BY
Why are we worried about forever chemicals?
Many of these chemicals have been in use for decades. Their durability and ability to resist heat, oil and water make them very useful.
Scientists have grown increasingly concerned about them because they persist for decades and build up over time in our own bodies, as well as in wildlife and the broader environment.
The key concern is what these chemicals may be doing to the animals that accumulate them.
Research in humans and laboratory animals links PFAS to immune suppression , hormonal changes, reproductive problems and developmental effects. But we don't yet have enough research to understand how different PFAS compounds and levels of exposure affect health .
Understanding these impacts in whales and dolphins is harder still. Marine mammals are long-lived, highly mobile and exposed to many human-made problems at once, from climate change to noise pollution to other contaminants.
Even so, there are warning signs. Some dolphin studies have reported changes in immune-related markers associated with PFAS exposure.
How do you test a whale for forever chemicals?
For humans, testing PFAS levels is usually done with a blood test. It is not as simple for whales and dolphins.
It is extremely difficult to take blood samples from large marine mammals in the wild. Scientists often rely on tissue samples from dead animals, particularly from the liver and kidney, where many PFAS compounds tend to accumulate. These samples are analyzed in specialized laboratories capable of detecting tiny concentrations of individual PFAS compounds.
Scientists have been measuring PFAS in whales and dolphins this way for decades. Each study added another piece to the puzzle, showing these chemicals were present in different species, populations and oceans.
Our study took a step back and looked at the global picture.
We compiled PFAS data from cetaceans worldwide, focusing on liver samples because they are the most commonly available tissue type, allowing us to compare studies across species and regions.
What did we find?
We found PFAS contamination differed substantially across species, location, sex, age and time.
The highest concentrations tended to be found in coastal dolphins and porpoises, suggesting animals living near urban and industrial areas face greater exposure.
Cetaceans in the Pacific had higher levels than other oceans. This is likely due to high industrial activity and the extent of historical PFAS production in coastal regions.
Female whales and dolphins can transfer forever chemicals during pregnancy and nursing. This means their calves can be exposed to concerning levels of PFAS at a very early age.
Males often end up with higher levels than females overall, as they cannot transfer these chemicals to their young.
There are some large gaps in the global data set we compiled, which means we don't fully know the extent of PFAS contamination in cetaceans off India, Indonesia and parts of Africa.
What should we do?
While important questions remain about the effects of forever chemicals on whales and dolphins, the widespread contamination we observed is a real concern. We need…
Read the full article at Phys.org →