Birds of prey warn us: How eagles and falcons reveal our PFAS pollution

PFAS, often labelled “forever chemicals”, turn up in frying pans, waterproof jackets and cosmetics - and by now they are also embedded deep in the natural world. An Italian research team has shown how birds of prey can help track down this invisible toxin more effectively. In practice, these animals become living measuring devices for contamination that has long since started to affect people too.

What sits behind the “forever chemicals”

PFAS is an umbrella term for per- and polyfluoroalkyl substances, a group of chemicals that are exceptionally stable. That very stability is what makes them so useful - and so risky.

• They repel water and grease.
• They withstand heat and abrasion.
• They barely break down in the environment.

PFAS can be found, among other places, in:

• non-stick coatings on pans and pots
• outdoor and technical clothing
• firefighting foams
• food packaging and pizza boxes
• some cosmetics and hygiene products

The difficulty starts once these substances get into the body. The kidneys and liver can hardly eliminate PFAS. The compounds build up in the blood and organs - a process experts call bioaccumulation.

“PFAS practically never leave the body. Every additional intake adds another layer to an already growing chemical account.”

Studies link PFAS, among other things, to hormonal disruption, a weakened immune system and a higher risk of certain cancers. The debate usually centres on drinking water and human exposure. This new Italian work shifts attention to wildlife - specifically, birds of prey.

PFAS and birds of prey as nature’s early-warning system

The study, published in the specialist journal Toxicology Mechanisms and Methods, analyses data from multiple regions worldwide. Its central question is: what role can birds of prey play in improving our understanding of how PFAS spread through the environment?

The conclusion is clear: falcons, eagles and other raptors are highly suitable as so-called sentinel species - in other words, biological warning systems.

“Birds of prey sit at the top of the food chain. What accumulates below them ends up in their bodies sooner or later - and can be measured there.”

The researchers detected PFAS in almost all tissues examined:

• blood
• liver
• eggs
• feathers

This wide distribution shows how deeply these chemicals penetrate the organism. Feathers and eggs can be collected relatively gently - an important consideration when rare species should not be put under additional pressure.

When fish is on the menu, the risk rises

One of the study’s key findings is that raptors that mainly eat fish show markedly higher PFAS concentrations than species that hunt only on land.

These include, for example:

• white-tailed eagles
• ospreys
• fish-hunting buzzards or kites in wetlands

The reason is straightforward: many PFAS types enter water first via industrial wastewater, sewage treatment works and rainwater runoff. From there, they accumulate in sediments, small aquatic organisms, fish - and ultimately in the predators that eat those fish.

“The food chain acts like a chemical amplifier: what starts small in the water ends up in the bird of prey at many times the concentration.”

The study therefore highlights how severely aquatic ecosystems in particular are affected by PFAS. Of special concern are long-chain compounds such as PFOS, which are extremely persistent and especially prone to bioaccumulation.

Why birds of prey are such powerful indicators

Choosing birds of prey as indicators is a strategically sound decision. Several factors combine to make them particularly informative:

• Top of the food chain: they eat fish, small mammals or other birds that may already be contaminated.
• Long lifespans: many raptors live relatively long lives - enough time to accumulate pollutants.
• Large ranges: they cover wide areas and can therefore signal contamination across large regions.
• Good monitoring access: breeding sites and eyries are often tracked for years, so the available data are comparatively strong.

Measuring PFAS in raptors does not just provide a snapshot of a single lake or river. It offers a more integrated view of chemical exposure across the animals’ entire habitat.

Older PFAS are declining - and new compounds are arriving

Some of the best-known PFAS have now been heavily restricted or banned in many countries. In certain regions, their concentrations really are falling slightly. At the same time, new, less-studied substances are appearing as replacements.

These “successor PFAS” are often shorter-chain and are claimed to break down more quickly. Early data, however, suggest they can still be problematic and can also travel long distances through water, air and food chains.

“Industry is switching from known to unknown molecules, but for nature it makes little difference: the contamination remains - it simply changes its chemical face.”

The Italian study therefore warns against being lulled into a false sense of security by declining values for a handful of older substances. Without long-term monitoring using clear standards, it is difficult to see which new PFAS are quietly becoming more important in the background.

Long-term surveillance rather than a brief snapshot

The researchers argue for comprehensive, multi-year programmes in which birds of prey are monitored systematically. Ideally, this would be combined with other species - for instance fish, seals or small mammals - allowing comparisons across different levels of the food chain.

A workable strategy could look like this:

• selecting sensitive species in contaminated regions
• regular sampling of blood, feathers and, where possible, eggs
• standardised laboratory methods to make results internationally comparable
• linking the data with information from drinking water, soils and food

Such programmes would not only show where contamination hotspots are located. They could also provide early signals as to whether bans or tougher rules in chemicals regulation are genuinely working.

What PFAS means for people in Europe

The findings from Italy are directly relevant to the German-speaking countries. Parts of Germany, Austria and Switzerland also have areas with heavily contaminated groundwater and drinking water. PFAS can enter the environment there via industrial sites, airports or former firefighting training grounds.

Birds of prey from such areas could show contamination patterns similar to those described in the study. Testing them would provide a clearer picture of how far PFAS have already moved into food chains in these countries.

PFAS source	Possible route into birds of prey
contaminated drinking water	fish absorb PFAS; fish-eating raptors then eat those fish
industrial waste	inputs into soils; small mammals and other prey species absorb PFAS
firefighting foams	seepage into groundwater, followed by uptake through aquatic food chains

Bioaccumulation, toxicity, cancer risk - what the terms actually mean

Many key technical terms around PFAS sound abstract, but they describe very tangible processes:

• Bioaccumulation: repeated intake of small PFAS amounts over a long period. The body breaks down very little, so levels rise slowly but steadily.
• Biomagnification: concentrations increase at each step of the food chain. From plankton to fish to raptor, the burden multiplies.
• Toxicity: depending on the PFAS type, the liver, immune system or hormonal system can be harmed, often even at low concentrations.

For people, this means that anyone regularly consuming contaminated food or water can build up a measurable PFAS level in the blood over the years. In birds of prey, the mechanism is similar - just often faster and with higher peaks, because they sit right at the top of the food web.

Practical steps: what researchers, policymakers and consumers can do

The Italian study does not offer an easy way out, but it does point to clear lines of action:

• Research: expand raptor-based monitoring programmes and publish open databases for international comparisons.
• Policy: tighter PFAS limits in water, rapid action when new suspect substances appear, and support for PFAS-free alternatives in industry and everyday products.
• Consumers: shop more deliberately, look for PFAS-free coatings and textiles, and follow local information on drinking-water quality.

In this context, birds of prey provide more than just lab numbers. When high PFAS amounts show up in their feathers, eggs and organs, it demonstrates that contamination has already reached the heart of ecosystems we are meant to protect - and, with it, it edges closer to our own health.