Toxicologists are urging food manufacturers to consider new packaging methods after discovering possible health risks from recycled cardboard.
Swiss researchers have found that mineral oils in printing ink from recycled newspapers used in cardboard can pass into food such as cereal, pasta and rice, even if surrounded by protective inner plastic bags.
They have linked the oils to inflammation of internal organs and even cancer, although they found that individual meals would contain only a tiny dose of the chemicals.
Koni Grob of the Food Safety Laboratory in Zurich said switching to non-recycled packaging would be costly for the environment and that new solutions needed to be considered such as inner food linings which are effective barriers to the oils.
"The easy idea to change over to fresh fibres is not a viable solution because it would cost too many trees. We need better solutions such as introducing special barriers," he said.
While research has found that products such as paper and bags made of polyethylene and polypropylene let mineral oils pass through, other linings like aluminium foil are effective barriers.
Analysis of 119 products bought from German supermarkets last year found that a large majority contained traces of mineral oils higher than the agreed level – with some exceeding the limits by up to 10 times.
However around 30 products which were lined with thicker and more expensive bags were uncontaminated by the oils.
Cereal firm Jordans has stopped using recycled cardboard while other manufacturers are looking at ways to reduce levels of mineral oils in packaging.
While toxicologists have discovered that mineral oils can cause chronic inflammation of internal organs or cancer, Grob said that consumers only had to be concerned about long-term exposure to the oils as “one meal has no real effect on health”.
"Our bodies already contain on average roughly around one gram mineral oil - that is by far the largest contaminant we have in our body. For some people it is 10 grams, which is a high value.
"We are obviously accumulating mineral oil over a lifetime. What the baby gets through human milk is probably staying over a lifetime.”
"For this reason, one month or less has no real effect, so there is no emergency, consumers should not make any rapid changes, we have to think about it.”