A new UNSW-led global meta-analysis shows that PFAS concentrations can double at every step up the food chain, leaving top predators - and humans - potentially exposed to higher chemical loads.
A bottlenose dolphin swimming off the coast of Shanghai, China eats a fish.
Before it was eaten, the fish, one of the millions of sardines that live in Chinese coastal waters, fed on smaller fish.
Those smaller fish fed on plankton and algae drifting through water laced with the faintest trace of industrial chemicals - per- and polyfluoroalkyl substances, PFAS for short.
By the time they reach the dolphin, or the eagle, or the tuna on someone's dinner plate, these chemical concentrations have magnified with every meal, and now a new meta-analysis led by UNSW researchers has revealed the scale of the problem.
Studies have linked PFAS to a host of illnesses, including some cancers , although Australian health authorities say there is limited conclusive evidence linking PFAS exposure to any specific disease and that more research is needed.
The authors examined 119 aquatic and terrestrial food webs across the globe, finding that top predators such as large fish, seabirds, and marine mammals can accumulate PFAS concentrations exponentially larger than the environments in which they're found.
"PFAS concentrations double, on average, with each step up the food chain," says study lead author Lorenzo Ricolfi, a PhD candidate from the UNSW School of Biological, Earth, and Environmental Sciences.
Known as "forever chemicals", PFAS are from a family of more than 12,000 man-made compounds.
These chemicals are prized for their heat resistance and water repelling properties, and are used in cleaning products, food-packaging, non-stick pans, clothing, and fire-fighting equipment.
Since being discovered by the American chemical company DuPont in the 1930s, PFAS are now detectable in the bloodstream of almost every human being on the planet.
Unlike other chemicals, PFAS never break down, meaning that throughout the world right now they're building up in environments, plants, and animals on land and in the ocean.
For humans, sitting as we do at the top of the food chain, this means the our diets can be an important pathway for PFAS exposure.
"Given what we know about PFAS toxicity from other studies, these extreme accumulation rates in top predators suggest serious health risks," Ricolfi says.
"This creates a cascading ecological risk: apex predators face disproportionately high exposure even in relatively low-contaminated environments."
The authors analysed 72 different PFAS and found dramatic variation in how much concentrations magnified up the food chain.
Some compounds - including chemicals marketed as safer alternatives to existing products - showed even higher magnification than the chemicals they were designed to replace.
"Urgent research into health impacts of these new chemicals is needed before they become as ubiquitous and problematic as the PFAS they're replacing," Ricolfi says.
Ricolfi and his co-authors want to see policy changes at the international level, where toxicity is considered but not how much the chemicals accumulate up the food chain.
The authors argue compounds more prone to accumulation need greater scrutiny, particularly those that are unregulated.
"Our findings demand immediate action across multiple policy fronts," Ricolfi says.
The team wants to see magnification data considered by international authorities when making regulatory decisions, instead of just acute toxicity.
They also argue authorities should urgently look at newer, unregulated chemicals prone to magnification before their use becomes widespread, particularly those that are filling the vacuum left behind by banned chemicals.
"Our findings reveal that some newer PFAS marketed as safer alternatives may replicate or even exacerbate the biomagnification consequences of legacy PFAS," Ricolfi says.
While PFAS concentrations double, on average, at every step up the food chain, the authors note wide variation between different chemicals, with some accumulating more readily and others less so.
Because of this the authors want to see regulations based on compound-specific information rather than a one-size-fits-all approach.
The research appeared in the journal Nature Communications .
