A new study finds signs of dementia-like brain damage, kidney and liver dysfunction and alterations in the stomach lining of seabird chicks with significant amounts of plastic in their stomachs, specifically in Sable shearwater chicks.
Seabirds eat plastic
Birds and other animals that live in seas and oceans mistake plastic debris floating in the water for food.
Sometimes because their sense of smell confuses this plastic debris with food, due to the fact that this waste emits a sulfurous compound, dimethyl sulfide. This is a compound released by algae that eventually cover floating plastics.
The algae themselves do not smell like food to birds, but the dimethyl sulfide is released when they, for example, are eaten by animals such as krill (small pelagic crustacean, similar to a shrimp), i.e., although the algae is not food, it smells like food.
On other occasions, species such as albatrosses eat brightly colored plastic, particularly red, green and blue, probably because they mistake them for prey.
Science has baptized this phenomenon as “plasticosis”, a term that was initially associated with the conditions caused by scars in the digestive tract of seabirds when ingesting pieces of plastic, and which is gradually being applied to all those pathologies that affect different organs and systems in living beings as a result of exposure to macro, micro and nano plastics.
Shearwaters
Shearwaters are medium-sized birds with long wings. Capable of traveling long distances by gliding through the air with minimal effort. Adult birds live on the ocean where they feed mainly during the day and do not return to land unless they are breeding or feeding their chicks. Incubation of the single egg they lay is shared by both parents, as is the rearing of the chick. The chicks remain in the burrow and are fed by their parents usually at night.
Balearic Shearwater chick. Seabirds are the most endangered group of birds globally. Author: Pep Arcos-SEO/BirdLife.
There are currently more than 20 species of shearwaters worldwide.
In Spain we have our own species, the balearic shearwater, the only endemic seabird in Spain and the most endangered in Europe. Currently in critical danger of extinction due to the alarming decline of offspring in a very small and localized population.
SEO/BirdLife has been working for decades on the conservation of the endangered Balearic shearwater. Author: Pep Arcos-SEO/BirdLife.
This seabird is present in the Indian and Pacific Oceans. It is considered by the International Union for Conservation of Nature (IUCN) as “near threatened”. One of the possible causes of its decline is the consumption of plastic by chicks and adults.
Chicks that eat plastic
Dr. Jack Rivers‘ research team used mass spectrometry techniques to identify disease markers in the blood of the birds under study.
Thirty-one sable shearwater chicks were identified on Australia’s Lord Howe Island.
All of them were healthy in appearance and had similar characteristics in terms of weight and size.
Signs of brain damage in seabirds with plastic in their stomachs. Researchers performed a procedure called gastric lavage to collect pieces of plastic ingested by shearwater chicks. Credit: Jack Rivers-Auty.
The gastric lavage performed on the chicks led the research team to group the birds into two groups, one group where individuals had consumed high amounts of plastic and another where they had consumed a smaller amount.
Study detects signs of brain damage in seabirds with plastic in their stomachs
A study by the University of Tasmania has found signs of brain damage in dementia-like sable shearwater chicks, in addition to problems with kidney dysfunction, liver and alterations in the stomach lining ( Sci. Adv . 2025, DOI: 10.1126/sciadv.ads0834 ).
Signs of brain damage in seabirds with plastic in their stomachs. Researchers recovered 403 pieces of plastic from a 90-day-old sable shearwater chick. Credit: Jack Rivers-Auty.
The researchers found significant differences in the levels of 202 of the 745 plasma proteins detected in the birds’ blood. High levels of intracellular proteins were found, proteins that should be inside the cells were now outside. Which could suggest that plastic is causing this situation.
Low levels of albumin (a protein produced by the liver), which could indicate liver or kidney dysfunction, were also found in the blood of birds with higher amounts of plastic in their stomachs. These same birds also had significantly low levels of a protein called brain-derived neurotrophic factor (BDNF). A key brain protein that stimulates the production of new brain cells, strengthens existing ones, and affects memory and learning.
Shearwaters, “sentinel species”.
Seabird chicks need as youngsters to mentally remember where they were born. In the case of shearwaters they can spend up to five years fishing far from their birthplace and then have to return to it to nest, journeys of up to 10,000 km, any problems arising from poor orientation or associated with memory could prove catastrophic for them. In addition, the team suggests that a decrease in BDNF levels could also affect the birds’ ability to distinguish songs from each other.
Author: Sylvia Domínguez Castillo
Black-capped Shearwater Bermeo (Spain), October 2024
It is unclear whether these shearwater chicks remain affected into adulthood. The researchers are therefore analyzing the blood of adult individual sable shearwaters from the same colony to assess the effects of plastic exposure.
INTERVIEW WITH Dr. Jack Rivers Auty
Dr. Jack Rivers Auty
Faculty of Medicine, University of Tasmania (Australia) Specializing in research on the innate immune system and inflammation. Dr. Jack Rivers Auty is a lecturer in the Medical Sciences in the School of Medicine at the University of Tasmania. His research focus is how inflammation can contribute to disease. Jack has a broad range of interests from how microplastics induce lung and gut inflammation to whether commonly use anti-inflammatories can be used to treat Alzheimer's disease. Jack's research group uses cell culture techniques, rodent models, human tissue, clinical data and statistical modelling to follow the science from cells in a dish all the way to people.
- 1. Why was this type of bird chosen and not another?
- 2. Did the chicks show any prior symptoms that could be associated with dementia?
- 3. What was the most striking aspect of the study?
- 4. What was the criterion for selecting the two groups? What could explain the difference in plastic consumption between individuals?
- 5. What data indicated brain damage, kidney dysfunction, and liver problems?
- 6. Did you expect the results of the study to match what you found?
- 7. Have you been able to establish any relationships based on the different chemicals or additives used in plastics?
- 8. How do you plan to continue this research? Would it be necessary to conduct similar studies in other bird species?
1. Why was this type of bird chosen and not another?
We’ve been studying this species for over 15 years, and it offers a unique research opportunity. These birds live in relatively pristine environments, largely free from air pollution and invasive species, which allows us to isolate the effects of plastic exposure. Additionally, they display a natural variation in plastic ingestion—ranging from mild to severe—providing a spectrum of exposure that is ideal for studying the effects of plasticosis.
2. Did the chicks show any prior symptoms that could be associated with dementia?
No, not at all. We were completely shocked to find dementia-associated biomarkers as the top signal in their blood proteins. One would assume the brain is shielded by the blood-brain barrier, but our data suggest that either microplastics are shedding from larger plastic pieces in the gut or chemicals are leaching from the plastics themselves. These particles and/or chemicals appear to be having a profound impact on brain health—a very unexpected and concerning result.
3. What was the most striking aspect of the study?
The most striking finding was the hidden severity of health impacts. Many assume that small amounts of plastic are harmless unless they physically block the digestive tract. But our birds looked outwardly healthy—well-fed and active. Yet, internally, they showed signs of significant damage to the liver, kidneys, stomach, and even the brain. It’s similar to smoking: you can’t always tell who smokes by looking at them, but we now know the long-term internal damage it causes. These are called sublethal effects, and they often require advanced techniques to detect.
4. What was the criterion for selecting the two groups? What could explain the difference in plastic consumption between individuals?
We selected birds that appeared healthy in terms of weight and body size and showed no outward signs of disease. We then gavaged them to flush out the plastics in their stomachs. Based on the amount of plastic retrieved, we divided them into high and low exposure groups. The high group had a median plastic load equivalent to about 1.5 teaspoons; the low group had only a few small fragments. Since chicks are fed by their parents, the differences likely reflect the foraging patterns of the adults—perhaps due to chance encounters with plastic patches or individual differences in their attraction to plastics, although we can’t say for sure yet.
5. What data indicated brain damage, kidney dysfunction, and liver problems?
For the brain, the key marker was BDNF (Brain-Derived Neurotrophic Factor), which supports neural connectivity and overall brain health. Its levels were reduced by 50% in high-plastic birds. In the liver, secreted proteins—mostly involved in blood maintenance—were significantly reduced, while internal liver enzymes appeared in the bloodstream, suggesting liver cell death and leakage. For the kidneys, we observed elevated markers of oxidative stress, indicating renal strain and early dysfunction.
6. Did you expect the results of the study to match what you found?
We anticipated seeing damage in the stomach, liver, and kidneys, as these are organs involved in processing ingested substances. Based on our previous work, we already knew that the stomach lining suffers damage from plastic exposure. Given the detoxifying role of the liver and kidneys, it made sense that they would be affected by leached chemicals and microplastics. However, the extent of the brain effects was entirely unexpected. The brain is usually well-protected, so these findings were both surprising and deeply concerning.
7. Have you been able to establish any relationships based on the different chemicals or additives used in plastics?
That’s a very important and emerging area. We have some preliminary cell culture data showing that different types of plastic exhibit different toxicity profiles. However, plastics are made with thousands of chemical additives, many of which are poorly studied. Understanding their individual and combined effects will require a great deal more research.
8. How do you plan to continue this research? Would it be necessary to conduct similar studies in other bird species?
Yes, absolutely. We’re currently expanding our research to include other bird species and even different animal groups. We’re also exploring potential links to human health, given the global scale of plastic exposure. This is a vast and urgent field of research that will need more scientists, more collaborations, and significantly more funding to fully understand the biological impacts of plastic pollution.