Some UK breakfast cereal manufacturers plan to stop using recycled cardboard in packaging after researchers in Switzerland discovered that current boxes could pose a cancer risk.
Researchers from the Food Safety Laboratory in Zurich found that toxic chemicals from recycled newspapers had contaminated food sold in many cardboard boxes even passing through the plastic bags within.
The chemicals, called mineral oils, which come from printing inks have been linked to the inflammation of internal organs and cancer, the UK's BBC reported.
UK cereal manufacturers Jordans has stopped using recycled cardboard in its packaging while Kellogg's said it is developing packaging that contains lower levels of mineral oils.
The Swiss researchers analysed 119 products bought from German supermarkets and found quantities of mineral oils between 10 and 100 times above the agreed limit in foods such as pasta, rice and cereals contained in cartons made from recycled cardboard.
"Roughly 30 products from 119 were free of mineral oils, nearly all because of an inner barrier,'' Dr Koni Grob said. ''For the others, they all exceeded the limits and most exceeded it by 10 times.
''We calculated that before the end of their shelf life, they would probably exceed the limit 50 times on average and many would exceed it by several hundred times.''
However, the UK's Food Safety Authority (FSA) said it is "not aware of any firm evidence to suggest that there are food safety risks related to mineral oils in recycled food packaging".
The FSA said due to incomplete data the results do not demonstrate that mineral oils present a health risk but would continue to investigate.
"The FSA is currently gathering information on the extent of the presence of mineral oils in food packaging on the UK market," the authority 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."