In an article published on September 17, 2020, in the peer-reviewed journal Environment International, Lisa Zimmermann and colleagues from the Goethe University Frankfurt am Main, Germany, and Norwegian University of Science and Technology, Trondheim, Norway, reported on the assessment of in vitro toxicity and chemical composition of extracts of bioplastics and plant-based materials used in food contact.
The scientists used methanol to extract a total of 43 samples, which included food contact articles made of diverse bio-based and/or biodegradable materials, as well as respective raw materials (pre-production pellets). Twenty-seven of these samples represented “bioplastics with the highest market share,” including bio-based polyethylene (bio-PE) and bio-based polyethyelene terephthalate (bio-PET), as well as polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), and polybutylene adipate terephthalate (PBAT). Sixteen samples represented plant-based materials, namely starch, cellulose, and bamboo. In vitro assays covered baseline toxicity, oxidative stress responses, and estrogenic and antiandrogenic activity. Chemical composition of the extracts was analyzed with non-target high-resolution mass spectrometry.
The authors report that “two-thirds (67%) of the samples induced baseline toxicity, 42% oxidative stress, 23 % antiandrogenicity and one sample estrogenicity.” The single estrogenic sample was a PLA film.
With regard to chemical composition, in total “41,395 chemical features with 186–20,965 features present in the individual samples” were detected, and “80% of the extracts contained >1,000 features, most of them unique to one sample.” Among these, “343 priority compounds including monomers, oligomers, plastic additives, lubricants and non-intentionally added substances” could be tentatively identified.
With regard to material identity, “extracts from cellulose and starch-based materials generally triggered a strong in vitro toxicity and contained most chemical features.” Specifically, all cellulose- and starch-based samples exhibited baseline toxicity and some also showed effects in other in vitro assays. The eight tested products made of starch included disposable cutlery, a bag for foodstuff, a waste bag, and several samples of films and pellets. The seven tested products made of cellulose included tea bag wrapping, chocolate wrapping, a cigarette filter, pellets, and three samples of bags for foodstuff. No toxicity was detected from a reusable coffee cup made of the so-called “bamboo” material, which is actually a blend of bamboo and melamine plastics (FPF reported). It has to be stressed, however, that only one “bamboo” sample was tested in this work. For bio-PE, bio-PET, and PBAT samples, “the toxicological and chemical signatures . . . varied with the respective product rather than the material.” One further observation was that “toxicity was less prevalent and potent in raw materials than in final products.”
The authors conclude that a comparison with the results from a similar study they have performed earlier with conventional plastics (FPF reported) “indicates that bioplastics and plant-based materials are similarly toxic. This highlights the need to focus more on aspects of chemical safety when designing truly ‘better’ plastic alternatives.” Zimmermann will present and further discuss this study during the Food Packaging Forum’s virtual workshop on October 21, 2020.
Zimmermann, L., et al. (2020). “Are bioplastics and plant-based materials safer than conventional plastics? In vitro toxicity and chemical composition.” Environment International. DOI 10.1016/j.envint.2020.106066