“A ‘highly toxic’ chemical in the glue on supermarket labels can seep through packaging and contaminate food”, The Daily Telegraph reported. This study looked at the chemicals in four types of adhesive, how they passed through different types of packaging, and whether the chemicals could be absorbed by a food-like material.
One of these chemicals was found to be potentially toxic and could be absorbed by food through a type of material called thick matt polypropylene. Limited data was given and it is unknown if other materials might be more or less absorbent.
The researchers estimate that the average daily consumption of this chemical through exposure to food labels is greater than safe levels. However, this chemical has no official recommended maximum daily allowance, but only an estimated theoretical advised maximum intake. Further work is needed to assess safe consumption limits.
This was preliminary research and has not provided a comprehensive analysis of whether there is a health risk from packaging and label adhesives. The Food Standards Agency said, "Our own research has found that although several chemical substances are present in adhesives, the potential for them to migrate into food is very low."
Where did the story come from?
The study was carried out by researchers from the University of Zaragoza in Spain. It was funded by the European Union and Gobierno de Aragón, Spain. The study was published in the peer-reviewed Journal of Materials Chemistry.
What kind of research was this?
This laboratory study assessed whether the chemicals found in adhesives of food labels were able to pass through different types of packaging material.
The researchers say that although there are regulations for plastics used in food packaging in the EU, adhesives are not regulated.
What did the research involve?
The researchers obtained four water-based adhesives that are commonly used on sticky labels for the food industry from adhesive companies.
They stuck each adhesive to six types of packaging material. The different materials’ thicknesses are measured in micrometres (1,000 micrometres [µm] = 1 millimetre). These included:
- polyethylene (PE) 40 µm thick
- sheen polypropylene (sPP) 25 µm thick
- matt polypropylene (mPP) 17.5 µm thick
- couche paper (cpaper) 70 µm thick
- kraft paper (Kpaper) 32 µm thick
- polyethylene terephthalate (PET) 25 µm thick
They wanted to assess how the adhesive chemicals were absorbed by the packaging (diffused) and if they could pass through it completely. They used an analytical technique called HS-SPME-GC-mass spectrometry to measure the chemicals.
The researchers also investigated how much of the chemicals would be absorbed by an artificial food ‘simulant’, a material called tenax, to model how much of the chemical might be absorbed by food.
What were the basic results?
The researchers concentrated on 11 component chemicals that they had previously shown to be present in adhesives. Out of these compounds, 10 were considered to be of low toxicity and only one (2,4,7,9-tetramethyldec-5-yne-4,7-diol) was in the high toxicity class. This compound was found in two of the four adhesives.
Tests showed that 2,4,7,9-tetramethyldec-5-yne-4,7-diol could pass through kraft paper, polypropylene and thick couche paper to varying degrees.
Four of the chemicals, including 2,4,7,9-tetramethyldec-5-yne-4,7-diol, could pass into the food simulant when it was sandwiched between paper and 17.5 µm thick matt polypropylene where the polypropylene was in contact with the food. The researchers did not present data for how much of the chemical would reach food when other packaging materials were between the adhesive and the food.
The researchers estimated that the daily intake of 2,4,7,9-tetramethyldec-5-yne-4,7-diol from food (based on their tenax experiments) would be 0.26mg of the chemical per day. There is no official recommended daily allowance for this chemical. The researchers estimated a theoretical maximum intake from the chemical’s structure. They suggested that, based on its toxicity class, the theoretical maximum recommended daily exposure to this chemical should be 0.09mg.
How did the researchers interpret the results?
The researchers say the chemicals pass through different packaging to various degrees. Their estimates of daily intake of 2,4,7,9-tetramethyldec-5-yne-4,7-diol exceeded the recommended daily intake based on its toxicity rating.
This research has given a greater understanding of how chemicals from food labels can pass through packaging. The study found that one potentially toxic chemical (2,4,7,9-tetramethyldec-5-yne-4,7-diol) was present in two of four adhesives that were tested. It also found that this chemical could pass into ‘simulant’ food through 17.5 µm thick matt polypropylene. It is unknown if other materials might be less absorbent. It is also not clear which adhesives are commonly used in the UK.
The researchers estimate that the average daily consumption of this chemical (based on an estimate of the fraction of foods in the diet that are expected to contain specific packing materials) is greater than safe levels. However, this chemical has no official recommended maximum daily allowance, but only an estimated theoretical advised maximum intake calculated from the chemical’s structure. Further work is needed to assess safe consumption limits.
This was preliminary research and has not provided a comprehensive analysis of the variety of packaging and label adhesives used in the UK, nor whether they carry a health risk. More research is needed to establish this. The Food Standards Agency said, "Our own research has found that although several chemical substances are present in adhesives, the potential for them to migrate into food is very low."