A more detailed analysis of a subset of 20 samples found that perfluorooctanoic acid (PFOA), a long-chain PFAS currently being phased out in the US, was among the packaging compounds.

The PFASs occurred at a wide range of concentrations, suggesting that some of them were not specifically added to the packaging but came from older, recycled materials or other undetermined sources.

The researchers say this could lead to the persistence of some of the compounds, even if phased out, for many years to come.

Study lead author Doctor Laurel Schaider, an environmental chemist at Silent Spring Institute, said: "These chemicals have been linked with numerous health problems, so it's concerning that people are potentially exposed to them in food.

"Children are especially at risk for health effects because their developing bodies are more vulnerable to toxic chemicals."

Co-author Doctor Arlene Blum, founder of the Green Science Policy Institute, said: "The replacement compounds are equally persistent and have not been shown to be safe for human health.

"That's why we need to reduce the use of the entire class of highly fluorinated compounds. The good news is there are non-fluorinated alternatives available."

Co-author Professor Graham Peaslee, a physicist at the University of Notre Dame who developed the method to screen food wrappers, added: "All PFASs, including the newer replacements, are highly resistant to degradation and will remain in the environment for a long time.