The 8th Food Packaging Forum (FPF) workshop “Improving the chemical safety of food contact articles: Linking policy-making with scientific research” took place online on October 21-23, 2020.
In his talk, Stefan Merkel from the German Federal Institute of Risk Assessment (BfR) discussed recent projects pursued by BfR in the area of risk assessment of chemicals migrating from food contact materials (FCM) into food. One example concerned the migration of melamine (CAS 108-78-1) and formaldehyde (CAS 50-00-0) from ‘melaware’ (articles made from melamine-formadehyde resin) and ‘bambooware’ (articles made from melamine-formaldehyde resin filled with bamboo fibers). Specific migration limits (SML) given for melamine and formaldehyde in the regulation (EU) 10/2011 on food contact plastics are 15 mg/kg and 2.5 mg/kg food or food simulant, respectively. Migration of melamine was found to increase with each successive migration round, exceeding the SML after about 7-8 migrations. Migration from ‘bambooware’ was much higher, exceeding the SML from the beginning and showing similar behavior to further increase with each succeeding migration round. Migration of melamine and formaldehyde was also found to strongly increase after heating, for example in an experiment simulating the use of coffee in a mug made of ‘bambooware.’ BfR concluded that tableware based on melamine-formaldehyde resin “can be used to consume foodstuffs at room temperature,” but it should not be used in microwave ovens or to hold hot meals or beverages, because this material is “degraded and damaged by contact with hot liquids” and it is particularly “not suited for repeated usage in contact with hot liquid foodstuffs” (FPF reported).
For many FCMs not yet having a dedicated EU-wide regulation, BfR has issued so-called recommendations which can be freely downloaded from its website. BfR’s Recommendation XXXVI covers paper and board for food contact. Bisphenol A (BPA, CAS 80-05-7) is not included in this recommendation as a substance allowed to be used in food contact paper production. However, it could still appear in the food contact paper due to the use of recycled fibers, which are allowed to be used as raw materials for the production of food contact paper. Therefore, the Annex of Recommendation XXXVI indicates a maximum value for migration of BPA into food from paper/board FCMs. Until 2015, this value was 600 µg/kg food, but then was lowered to 240 µg/kg food and then to 50 µg/kg food.
Lisa Zimmermann from the Goethe University Frankfurt, Germany, presented the results of her recent work applying non-targeted chemical analysis and in vitro bioassays to investigate the chemical composition and toxicity of mixtures extractable from articles made of conventional plastics, bioplastics, and plant-based materials. In 2019, a mixture of substances extracted from bioplastics such as polylactic acid (PLA) was found to exert similar toxicity as that found in conventional plastics such as polyvinylchloride (PVC) and polyurethane (PUR) (FPF reported). Now, high toxicity was confirmed for some products made of a wider variety of bioplastics, including PLA, bio-based polyethylene (bio-PE) and polyethylene terephthalate (bio-PET), PLA, polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), and polybutylene adipate terephthalate (PBAT), as well as for cellulose-based and starch-based materials (FPF reported). The observed toxic effects included baseline toxicity (frequent), oxidative stress and estrogenicity (rare), and anti-androgenicity (frequent).
Zimmerman concluded that “toxicologically, bio-based/biodegradable materials are not better than conventional plastics” and called for a more targeted consideration of chemical toxicity in the design of (bio)plastic products. She then discussed opportunities and challenges posed by increased use of bioplastics replacing conventional plastics in some food contact applications. As a way forward, Zimmermann suggested that considerations related to chemical safety should receive more weight in regulations and frameworks aimed at comparing the safety and sustainability of different FCAs, such as life cycle analysis. To enable appropriate assessment of chemical safety, complexity of chemicals and polymers used in food contact may need to be reduced, and chemical composition of FCAs should be transparently communicated. In addition, instead of assessing one substance at a time, Zimmermann recommended to test the whole migrate from the final FCA. Complex requirements placed on different types of FCAs are resulting in complex challenges. This makes a “one-size-fits-all solution unlikely” and instead necessitates a differentiated approach, where the most sustainable products should be developed and evaluated to be selected for each niche separately.
Andrew Turner from the University of Plymouth, UK, talked about hazardous elements in plastic and glass articles for food contact and storage. According to Turner, four groups of plastic additives represent a particular concern with regard to human health, namely flame retardants, heat stabilizers, pigments, and plasticizers. Turner discussed studies demonstrating the likely presence of brominated flame retardants in FCAs made of black plastics, introduced there through contamination of recycling streams with waste electric and electronic equipment (WEEE) (FPF reported). Two of the tested cocktail stirrers had such high concentration of bromine (pointing to the likely presence of brominated flame retardants) that they would not have been allowed to be used to make a laptop case according to the Restriction of Hazardous Substances (RoHS) directive (Directive 2002/95/EC).
Toxic heavy metals, such as cadmium (Cd, CAS 7440-43-9) and lead (Pb, CAS 7439-92-1) were also regularly detected in products made of black plastics, including many FCAs. Two regulations of relevance to heavy metals in food contact plastics include Directive 94/62/EC which regulates Cd, Pb, Cr(VI) and Hg in packaging and packaging waste, and Directive 2002/72/EC which regulates Pb and Cr (VI) in FCAs. Black plastics where high concentrations of Br, Cd, and Pb were frequently detected were often made of polyethyelene (PE), polypropylene (PP), polystyrene (PS), and acrylonitrile-butadiene-styrene (ABS) plastic polymers. In contrast, these elements were never detected in black plastics made of polyethylene terephthalate (PET). PET is only infrequently used in electronics, which is probably the reason why this material escapes this “toxic cycling,” Turner explained.
He then turned to discussing Cd and Pb content in outside enamels brought on decorated glassware. Very high concentrations of these metals measured in some of the products are likely due to the use of metal-containing pigments, such as heat resistant pigment containing Cd or Pb-containing overglaze. Turner explained that the use of these pigments as glass decorations does not make the product non-compliant, because they are considered as part of the glass, and, divided by the overall weight of a bottle, the levels appear to be much lower. However, he questioned whether external decoration really should be considered as part of the glass and suggested to address the question whether it would “come-off” from a product. Indeed, Turner then showed a product where exterior decoration became detached, likely because the Cd-containing pigment was unglazed, and concluded that such products both pose a “significant direct human health risk” and add to the contamination of glass cullet. According to Turner, FCM safety issues requiring immediate attention include “(i) export of hazardous plastics; (ii) recycling of materials into products serving a different function; (iii) components of articles that pose a hazard.” In a subsequent Q&A session, it was commented that products featuring external decorations which could be based on heavy metal-containing pigments constitute a relatively low proportion (1-2%) of all glass-made FCAs. Further, efforts are being made to eliminate or substitute the use of heavy metal-based pigments for external decoration of glass articles.
European Bioplastics (October 29, 2020). “Hazardous chemicals in plastic and glass articles for food contact and storage.”