How birds of prey are exposing a toxic time bomb | Pollution

Rui Lourenço first started collecting feathers because they were beautiful. Below the birds’ cliff-side nests in rural Portugal, he would find their shed feathers and bring them back to his ecology lab at the University of Évora. “It was just the typical curiosity of a naturalist,” he says. “Especially the flight feathers, they’re large, they’re soft, they have really interesting patterns.”

One day, a colleague asked if she could check them for toxic chemicals. As top predators, raptors’ concentration of chemicals is particularly high due to a phenomenon called biomagnification in which concentrations increase as you go up the food chain. This means that monitoring them can help reveal what substances are polluting the natural world. Lourenço now regularly sends feathers for analysis. “They work as an alert system not only for predators, but for the environment and humans,” he says.

And we need to be alerted. This year, a team of scientists warned that we had probably breached the planetary boundary for how much chemical pollution the Earth can handle and still remain a suitable home for human beings. Since the release of new chemicals now far outstrips our ability to test and regulate them, they argue, the situation is out of control.

Then, last month a paper showed that just one class of chemicals – per- and polyfluoroalkyl substances (PFASs), also known as “forever chemicals” because they do not break down in the environment – is now ubiquitous in Earth’s rainwater at concentrations above the safe drinking limit. “At the UN environment programme, they talk now consistently about the triple crisis: climate, biodiversity and pollution,” says Linn Persson from the Swedish Society for Nature Conservation, who co-authored the planetary boundary warning.

Chemical pollution is a vast problem, the depth of which is still unclear because many chemicals are not extensively tested for their environmental impact and not routinely monitored. This means that analysing raptors and other top predators is one of the only ways to tell how bad the situation really is – and how to save it.


‘There are around 350,000 substances marketed worldwide and around 100,000 of these are marketed in the EU,” says ecotoxicologist Paola Movalli. “Of these, only about 500 are well-characterised for their [hazards and] exposure.” That leaves a huge knowledge gap for scientists and for regulators deciding where to step in. “You can’t regulate something unless you know whether it’s a problem and why it’s a problem,” says Daniel Lapworth, who researches groundwater pollution at the British Geological Survey.

Since 2007, the EU has had Reach, a regulatory framework for industrial chemicals not covered by food, medicine or agricultural legislation, and post-Brexit, the UK has UK Reach. While similar, UK Reach is starting to diverge on what substances to regulate and how. “[We] are trying to create a UK version of it rather than just what we acquired on the day we left the EU,” says Andrew Smith, a regulatory scientist at the UK’s Health and Safety Executive. Under either system, however, companies must provide substance dossiers with information on hazards to human health and potential environmental effects.

But the lower the amount produced or imported, the fewer tests are required. The European Environment Agency estimates that more than 70,000 mostly low-volume chemicals have little to no toxicity information available. On top of that, reports from the German Environment Agency show that at least a quarter of dossier datasets for medium and high-volume chemicals do not actually comply with Reach’s requirements. “We are producing tens of thousands of different compounds,” says Lapworth, “but for many of them, we don’t have the toxicity data.”

Most under-studied chemicals face no regulation and are not routinely monitored. Scientists, however, have started to find some of them in the environment: in water supplies, the Arctic and now in top predators such as birds of prey. Dubbed “emerging contaminants” (ECs), their presence is worrying because it suggests that they build up in living organisms and do not easily break down. Such pollution is very difficult to reverse and can cause problems for decades: for example, polychlorinated biphenyls were banned in the 1980s, but still seem to cause infertility in Britain’s last orcas.

Point of no return? Orcas around the British Isles produce calves only rarely, with fertility thought to be affected by high levels of PCBs. Photograph: SeaTops/Alamy

ECs are not necessarily new in the environment, but advanced mass spectrometry techniques mean that scientists can now spot more and more of them. They give an almost complete picture of “the ‘universe’ of chemicals in the environment”, says Movalli, who is based at the Naturalis Biodiversity Centre in the Netherlands. That is critical because wildlife is exposed to chemicals in combination, not one by one.

For example, a study this year found an overwhelming 85 contaminants in 30 white-tailed eagles from northern Germany, including pharmaceuticals, musk fragrances, pesticides and PFASs. While some were long-banned chemicals such as DDT, still frequently found in wild animals after over 40 years of restrictions, many were ECs. Other recent raptor studies also report detecting new types of flame retardants, UV filters from sunscreens and plastic additives such as bisphenols.

PFASs are a particular concern, says ecotoxicologist Veerle Jaspers from the Norwegian University of Science and Technology. They are used for all kinds of things, such as lining takeaway bags and waterproofing raincoats, and some have been linked to hormone and immune disruptions as well as cancer in humans. Jaspers has found PFASs in eagle-owls in Norway and has seen “very clear effects” of them in the lab.

In one study, she and her team tested the effect of a now restricted PFAS against an unregulated alternative in chicken eggs, at comparable concentrations to those observed for PFASs in wild eggs. They found that both chemicals altered the chicks’ heart rate, potentially imperilling their hatching. At a higher dose, which was still significantly less than the reported PFAS exposure in eggs close to European chemical plants, the unrestricted alternative also resulted in abnormally large livers.

And because there are so many of them, they also make up a complex cocktail on their own. Movalli and her colleagues recently detected 56 different PFAS compounds across nine species, including buzzards. Only two are currently banned by Reach and the Stockholm Convention, an international treaty that tackles persistent pollutants worldwide.


Research like Jaspers’s and Movalli’s suggest that exposure is significant and widespread in the environment, so it is no surprise that people are also exposed to many ECs. After all, we are surrounded by them: we put them straight on our skin and cook our food with utensils covered with them. According to estimates, almost everyone on Earth has PFASs in their blood.

That exposure is full of unknowns, even for chemicals we are beginning to understand better. Take the plastic additive and endocrine disruptor bisphenol A (BPA). In 2015, the European Food Safety Authority (EFSA) concluded that normal exposure was way under the safety limit and posed no health risk to the public. But in late 2021, it suggested lowering that limit by many orders of magnitude due to new evidence. This would mean that it now considers most people to be ingesting too much.

As with raptors, biomonitoring can bring clarity here. Environmental epidemiologist Carl-Gustaf Bornehag from Karlstad University runs a large human biomonitoring project called Selma on endocrine disruptors. In a paper published in Science earlier this year, he and his colleagues showed how considering the broader endocrine-disrupting mix of chemicals we are exposed to can help us judge our risk from them better.

a white-tailed eagle by the isle of mull in the inner hebrides of scotland
Scientists recently analysed the livers of 30 white-tailed eagles in northern Germany and found over 85 contaminants. Photograph: Our Wild Life Photography/Alamy

“We have a risk assessment system [of chemicals today] where we take one compound at a time,” he says, “but we are always exposed to very complicated mixtures.” In the study, he identified a mix of chemicals from the blood and urine of nearly 2,000 pregnant Swedes that was associated with having children with a language delay. It consisted of BPA, phthalates and various PFASs.

His colleagues then extensively tested the mix in tadpoles, zebrafish and lab-grown human “mini-brains”. They found significant hormone disruption that increased with dosage. Based on these experiments, the team defined a level of concern before checking the pregnant Swedes: a whopping 54% were above the threshold. Considering the effect of mixtures revealed by biomonitoring, Bornehag says, the safety limit of many everyday chemicals might need to be lowered.

According to Jaspers, however, sufficient action on problematic chemicals can take decades, whether it is to protect humans or wildlife. Movalli shares her frustration: “When a chemical is restricted or banned after years of studies, industry simply replaces it with a similar one,” she says. “It then takes more years of studies to restrict the new substance – repeat ad infinitum.”

Bornehag says he saw the exchange of one phthalate for the next throughout the 2000s. In certain cases, BPA has also been swapped for other endocrine-disrupting bisphenols in products where BPA has been restricted and some replacement flame retardants show similar toxicity to their banned predecessors. But to Smith, it is not as black and white as that. Just take asbestos, he says. Industry is “always going to be very wary of anything that looks like asbestos. The last thing they want to do is to be accused of creating the next big problem.”

One way to circumvent this is to group and regulate substances together. That does look set to become more common: member states are preparing a proposal for the EU to ban most PFASs and the European Commission recently published its vision for restricting a huge number of harmful chemicals by group as part of its new chemicals strategy. At the same time, the EFSA is looking to consider chemical mixtures in its risk assessments.

a burn and lone dead tree on rannoch moor on the edge of the scottish highlands
Rannoch Moor on the edge of the Scottish Highlands. A recent study has shown that rainwater is no longer safe to drink due to levels of “forever chemicals”. Photograph: Adam Burton/Alamy

“[Grouping chemicals] is increasingly what we want to do because it is much more efficient,” says Smith, though with regard to PFASs, he says they are more varied than most people realise. The UK recommendation on how to deal with PFASs, including potential restrictions, was expected this summer but has yet to be published. Similarly, the UK’s delayed chemicals strategy, which was proposed in 2018 with the 25-year environment plan, is expected some time this year.

With the EU’s new strategy signalling a step change, there are fears that UK Reach will fall behind. “Any divergence or any kind of delays in making decisions about particular groups of contaminants [could cause] a problem,” says Lapworth. “It’s potentially a dilution of the gold standard that we were working in line with.”

Persson and her co-authors worry that trying to assess all the chemicals out there is too big a job, a view they share with the European Environment Agency. “The constant inflow of new substances that we synthesise is so much quicker than our capacity to assess,” she says, especially on a global scale. Instead, she and co-authors floated the idea of a fixed cap on chemical production, inspired by emissions caps in the fight against global heating

This idea might find sympathy among the ecotoxicologists who study raptors. When you ask Movalli what chemical worries her most in relation to the peregrine falcons she monitors, you get a list that goes on for some time. PFASs, old toxic metals, the long-banned dioxins, endocrine disruptors, even stimulants such as nicotine. “Sincerely, I am worried about everything,” she says.