How safe is the inclusion of recycled material for plastics used in food industry?

Humans are exposed to plastic particles through several pathways, including through food contaminated by plastics derived from packaging. This is a major challenge to overcome, as plastics are extremely useful for food industry (e.g., transport and prevention of food spoilage). In this sense, the plastic industry is aiming at improving the sustainability and safety of their products. The present work involved the collaboration of producers and academia to develop new strategies in food packaging, namely the incorporation of recycled material into water bottles made of polyethylene terephthalate (PET) and yogurt cups made of polypropylene (PP). An evaluation of the toxicity profiles of microplastics originated from the new materials in comparison to commercial plastic materials already in use, was made using human cell lines as biological model, namely PNT-2, HepG2 and HCT116. The test materials were mechanically degraded and two different size ranges of particles were obtained by differential filtration, micro(nano)particles below 25 µm and 1.6 µm. Cells were exposed to different concentrations (1.28 µg/L up to 100 mg/L) and cell viability was assessed at 24, 48 and 72h of exposure, using the MTT assay. In general, the new materials presented lower impact in cell viability in the 3 tested cell lines, with lower IC₅₀. PNT-2 was the less sensitive cell (for both commercial and new materials), regardless of size. HCT116 was the most sensitive cell line, and plastic toxicity was modulated by the exposure duration. Overall, incorporation of recycled proved valuable, allowing reduction of production costs and biological impact.