A screening of metal(loid) content in conventional and compostable plastic polymers: understanding the sources and the connected environmental implications

Plastic pollution is a well-known environmental issue, yet the ecotoxicological implications are still underexplored. In this context, attention towards the characterization of chemical additives in plastics and their potential risks to both human health and ecosystems is now increasing. While significant research has been conducted on organic chemicals, data on inorganic additives (e.g., metallic compounds) remain limited. In this study, we analyzed the metal(loid) content in different types of plastics to better understand the presence of inorganic additives in these materials, their distribution across different polymer types, and their potential impacts. We investigated pristine plastic pellets, single-use plastic materials and recycled plastic pellets made from both conventional and compostable polymers. We observed a notable enrichment of metal(loid)s (particularly Ti, Al, and Zn) across a range of plastic types, especially when comparing pre-production pellets with final consumer materials, suggesting that these additives are incorporated during the final stages of production. Samples of polyethylene terephthalate displayed elevated levels of Sb, while compostable plastics exhibited specific trends related to Sn and In: they are abundant in the pellets, since they are used as catalyst in polymer production. This study provides a comprehensive comparison of metal additives in different plastic polymers and across different production phases. It highlights the need for characterizing metal(loid) content in plastic to understand the potential connected risks. Additionally, the findings underscore the role of compostable plastics as potential carriers of metal(loid)s to terrestrial and aquatic environments, raising concerns about their degradation and impact.