Leading food manufacturers are changing their packaging because of health concerns about boxes made from recycled cardboard, the BBC has learned.
Researchers found toxic chemicals from recycled newspapers had contaminated food sold in many cardboard cartons.
The chemicals, known as mineral oils, come from printing inks.
Cereal firm Jordans has stopped using recycled cardboard and other firms are to ensure their recycled packaging does not contain any toxic oils.
Kellogg's and Weetabix said they were taking steps to reduce the amount of mineral oil in their packaging.
Exposure to mineral oils has been linked to inflammation of internal organs and cancer.
Government scientists in Switzerland found quantities of mineral oils between 10 and 100 times above the agreed limit in foods like pasta, rice and cereals sold in cartons made from recycled cardboard.
In one scientific paper they describe the potential for mineral oils to migrate into foodstuffs as "frightening".
However, the Swiss food safety authorities have concluded that consumers who eat a balanced and varied diet have no need to worry.
In a statement Jordans said that, as an environmentally responsible company which had previously used largely recycled packaging, it had taken the decision to abandon it reluctantly, but felt it was sensible.
The BBC investigation found other food companies were aware of the issue - but none had so far followed Jordans' lead.
More than half the cardboard used in Europe is made from recycled materials.
So-called "virgin board" from newly harvested trees is more expensive and there is not enough of it to replace recycled card completely.
The research has been led by Dr Koni Grob at the government-run food safety laboratory of the Canton of Zurich.
In one study for the German food ministry last year he and his colleagues tested a sample of 119 products bought from German supermarkets.
They found mineral oils passed easily through many of the inner bags used to keep food dry and fresh.
The longer a product stood on the shelves, the more mineral oil it was likely to absorb.
Dr Grob told the BBC: "Roughly 30 products from these 119 were free of mineral oil.
"For the others they all exceeded the limit, and most exceeded it more than 10 times, and we calculated that in the long run they would probably exceed the limit 50 times on average and many will exceed it several hundred times."
The agreed safe limit for mineral oil saturated hydrocarbons, derived from an expert evaluation carried out for the UN's Food and Agriculture Organization and the World Health Organisation, is a migration of 0.6mg per kilogram.
Studies on rats have highlighted the dangers to health of mineral oils.
Dr Grob said: "Toxicologists talk about two effects. One is the chronic inflammation of various internal organs and the other one is cancer."
But he stressed consumers would have to be exposed to contaminated foods over many years for their health to be at risk.
The Food and Drink Federation, which represents Britain's food companies, said the Swiss study was "a good starting point for further investigations" - but not enough in itself to justify discontinuing the use of recycled card.
Nonetheless, some of the individual members of the FDF are taking steps to change their packaging.
Kellogg's said it was working with its suppliers on new packaging "which allows us to meet our environmental commitments but will also contain significantly lower levels of mineral oil".
The company is also looking at alternative inner liners for its packets.
Dr Grob's studies suggest only aluminium-coated bags or those made of certain types of thick plastic are an effective barrier to the migration of mineral oils.
Weetabix said it uses 100% recycled board because it is better for the environment, but is also looking at recycled packaging that does not contain recycled newspaper.
Like several other companies, it said: "Our data... does indicate that none of our products pose a risk to consumer health".
In Germany the government has told the food and packaging industries to take immediate steps to reduce the risk from mineral oils, and is considering introducing mandatory rules.
In the UK the Food Standards Agency is doing research of its own: but so far it is only looking at how much mineral oil there is in recycled packaging, not how much gets into the food inside.
Terry Donohoe, the acting head of the FSA's chemical safety division, said: "Should there be any evidence from our study - and we will carry out a risk assessment - we will take immediate action to protect the public."
Dr Grob and his colleagues say that even switching to virgin cardboard would not eliminate the risk from mineral oils entirely.
This is because food cartons are themselves stored and transported in larger corrugated cardboard boxes which are also made from recycled newspapers, and are also a source of contamination.