PFAS: How Birds of Prey Reveal Environmental Contamination

When people think of majestic birds of prey, they usually picture spectacular aerial manoeuvres rather than invisible chemistry. Yet a new study from Italy shows that raptors reveal just how heavily our environment is contaminated with so-called “forever chemicals”. These substances occur in tap water, frying pans, jackets and cosmetics - and accumulate in bodies without ever properly disappearing.

What lies behind “forever chemicals”

The substances examined are PFAS: per- and polyfluoroalkyl substances. For decades, these chemicals have been used in countless everyday products: they make textiles water-repellent, pans non-stick, packaging grease-resistant and firefighting foams exceptionally effective. The cost is that they barely break down.

PFAS are found in drinking water as well as rivers, lakes and soils, eventually reaching our bodies. The kidneys and liver can eliminate them only to a very limited extent. Over time, these compounds build up in blood and tissue - a process experts call bioaccumulation.

“PFAS do not disappear; they move: from products into the environment, from the environment into animals, and from animals into people.”

Studies link high PFAS exposure in people to:

• disruptions to the hormonal system
• weakened immunity and poorer vaccine responses
• altered liver function and raised blood lipid levels
• an increase in certain cancers
• possible effects on fertility and children’s development

The new Italian research now places the effects on wildlife - especially birds of prey - at the centre of attention, showing how clearly they reflect our own impact.

Birds of prey as nature’s early-warning system

The researchers assessed data from several regions worldwide and considered numerous species, including falcons, eagles, buzzards and other predators. The conclusion is clear: PFAS were detected in virtually every bird body part examined - in blood, liver, eggs and even feathers.

This points to a key finding: birds of prey are highly suitable “sentinel species”, meaning biological early-warning systems. Because they occupy the top of the food chain, they accumulate everything that has already built up in fish, small mammals and other prey.

“Where birds of prey show high PFAS levels, the entire food chain below them is already heavily contaminated.”

The study also identifies a clear difference among raptors: species that mainly eat fish carry substantially higher concentrations than species hunting solely on land. This directly highlights a long-recognised weakness in our ecosystem.

Why waterways become PFAS hotspots

PFAS enter rivers and lakes through industrial wastewater, sewage treatment works, landfill sites and run-off from contaminated soils. Fish then absorb the substances through their gills and food. Since PFAS are hardly degraded, levels in the body increase with every further meal.

Fish-eating birds of prey - such as ospreys and certain harriers - feed at the top of this aquatic food chain. The Italian data show that their PFAS levels are regularly higher than those of relatives that hunt mice or other land animals.

Birds of prey therefore identify aquatic landscapes as particularly sensitive areas. Where PFOS and related long-chain compounds accumulate, persistent contamination hotspots arise that are difficult to control. These long-chain PFAS are regarded as especially bioaccumulative and long-lasting.

How effects intensify through the food chain

One important mechanism is called biomagnification: a small fish absorbs a low PFAS concentration from the water. A predatory fish eats many of these smaller fish, while a white-tailed eagle in turn eats many predatory fish. At each level, the substances become more concentrated in the body:

• low concentration in water
• higher concentration in small aquatic organisms
• higher concentrations still in fish
• peak levels in birds of prey, otters or seals

Raptors are therefore not only symbols of a healthy natural environment; they are also measuring instruments for the invisible burden in rivers, lakes and wetlands.

New PFAS variants - the same problem, less data

In some regions, international regulations have already reduced concentrations of certain PFAS types. However, the gap is being filled by replacements about which little is yet known. Manufacturers are switching from long-chain compounds to shorter-chain alternatives or new molecules with similar properties.

These substances also reach the air, water and soil while toxicologists are still gathering data. The Italian study therefore warns against being misled by declining levels of individual “older” chemicals. The overall chemical burden remains problematic - and may be underestimated.

“While known PFAS are regulated, industry is introducing new variants for which robust risk data are lacking.”

This is precisely where birds of prey become important: in principle, they incorporate every new PFAS generation that reaches their prey. They do not respond to individual substance names, but to what is actually circulating in the environment.

Why long-term monitoring is so urgent

The researchers call for standardised, long-term monitoring programmes. Only these can track how contamination changes over years and decades. Crucially, the focus should not rest solely on birds of prey; they should be combined with other animal groups, for example:

• fish and mussels for aquatic systems
• amphibians as indicators of wetland habitats
• small mammals for agriculturally dominated landscapes
• marine mammals in coastal and offshore regions

Birds of prey provide a kind of umbrella indicator: if they show high levels, widespread and long-term contamination can be assumed. Policymakers and authorities can use such data to identify hotspots, prioritise clean-up work or tighten limit values.

Practical consequences for everyday life

Although the study focuses on birds of prey, it raises several practical questions for consumers. Many people want to know how they can at least limit their personal exposure. Experts often suggest similar approaches:

• check whether local tap water is contaminated and, if necessary, use suitable filters
• replace old, badly damaged non-stick pans and look for PFAS-free coatings when buying new ones
• choose outdoor textiles and waterproofing products carefully, paying attention to references to fluorine-based protection
• reduce packaging waste, especially grease-resistant fast-food packaging

Such measures do not solve the global problem, but they show that the issue does not affect only remote conservation areas: it is directly connected to our purchasing choices.

How severely birds of prey are affected by PFAS

For the animals themselves, this is about more than laboratory measurements. High PFAS exposure can lead to poorer reproduction, weakened immunity and developmental disorders in chicks, among other effects. If eggs have thinner shells or chicks are less likely to survive, entire populations may become unstable over time.

Birds of prey are often sensitive to environmental pollutants because they reach sexual maturity late, raise only a small number of young each year and invest considerable energy in every clutch. Even minor disruptions to breeding success or health can affect populations in the longer term.

These effects do not affect rare species alone. Even apparently widespread birds of prey can come under gradual pressure while still seeming stable from the outside.

Why PFAS will remain an issue for a long time

A central feature of PFAS is their exceptional persistence. Even if all emissions stopped immediately today, a vast legacy burden would remain in soils, sediments and organisms. This reservoir continues to release substances gradually - like a store from which small quantities keep seeping out.

Birds of prey therefore act not only as indicators of present-day pollution, but also of this “chemical past” stored in the environment. Changes in their blood levels or eggs can reveal whether clean-up measures are genuinely making a difference over the years.

For experts, the Italian study demonstrates two things: first, how extensively PFAS have entered ecosystems; second, how useful biomonitors such as eagles and falcons are for tracking a trend whose causes often date back decades. Anyone looking to the sky therefore sees more than spectacular hunters - they also see valuable witnesses to an ongoing contamination problem that has long reached everyday life.