Food in supermarkets at risk from contamination

Chemicals used in adhesives for food labels can seep through packaging and contaminate food, according to research published by the Royal Society of Chemistry.

Strict EU regulations exist for the use of plastics in food packaging, but there is no specific legislation about the chemicals in adhesives used to attach sticky labels directly or indirectly to food packaging or to fix packaging layers together. But all materials that come into contact with food must comply with framework regulation set out by the European Parliament*.

A team of scientists studied compounds in acrylic adhesives, and discovered that some chemicals can diffuse through the packaging and reach the food inside. One of those is considered highly toxic and found in high concentration in some adhesives.

Their results, described by one expert as a "significant breakthrough" are published in the latest edition of the RSC's Journal of Materials Chemistry.

The team, from the University of Zaragoza, Spain, studied four different acrylic adhesives and examined in detail 11 compounds found in them. Some were solvents, while others were residual monomers or impurities remaining from manufacture. There are three toxicity classes: low, moderate and high. Ten of the 11 compounds studied had low toxicity while the remaining compound belonged to the high category. But the authors point out that "some of these compounds had a restriction or specification in the Commission Directive 2002/72/EC relating to plastic materials and articles intended to come into contact with foodstuffs".

Of the 11 compounds, four migrated all the way into the food stimulant used for the experiments, with two being higher toxicity than recommended by the International Life Sciences Institute Europe, the body that investigates food safety and toxicology. One of these, 2,4,7,9-tetramethyldec-5-yne-4,7-diol, which is used as a non-ionic surfactant, has high concentrations in some adhesives, and this, together with its high toxicity, makes it a particular target for future studies, says Cristina Nerín, who led the team.

Nerín placed a layer containing the adhesive on to a layer of packaging material (polymer or paper) that covered Tenax, a food simulant. Analysis of the layers using mass spectrometry determined whether, and how far, any chemicals had diffused through. The reasons why chemicals can seep from the sticky labels to the food depend on many factors such as the food itself, time, temperature and other structural properties.

Valérie Guillard, an expert in food technology and packaging at the University of Montpellier, France, said: "This work brings significant breakthroughs in the study of compliance with regulations of food contact materials." She believes Nerin's studies show that "migration of adhesive compounds is possible and at a level that could raise safety concerns".

*Framework Regulation (EC) 1935/2004

References

Elena Canellas, Margarita Aznar, Cristina Nerín and Peter Mercea, J. Mater. Chem., 2010
DOI: 10.1039/c0jm00514b