Comparative ecotoxicity of a reduced graphene-polypropylene nanocomposite and its components to the terrestrial...

Graphene-enhanced polymer composites are attracting interest due to the unique properties of graphene-related nanomaterials. However, their environmental impact, especially as sources of micro- and nanoplastics (MNPs), remains underexplored compared to conventional polymers. Therefore, comprehensive environmental risk assessments of advanced polymer nanocomposites are needed. This study assessed the toxic potential of reduced graphene oxide-enhanced polypropylene (PP-rGO) using a multi-biomarker approach, focusing on how rGO alters the ecotoxicological profile of polypropylene (PP). Terrestrial isopods were exposed for 14 days to soil mixed with PP and PP-rGO MNPs at 1% and 10% w/w, and to reduced graphene oxide (rGO) alone at 0.1% and 1% w/w. The lowest tested concentrations represent environmentally relevant levels of MNPs in soil, while the highest concentrations reflect a worst-case scenario. Organism-level toxicity was evaluated by monitoring survival, body weight change, and moulting frequency. Sublethal stress responses were evaluated in isolated isopod haemolymph using cellular and biochemical biomarkers, including haemocyte counts, haemocyte viability, and phenoloxidase-like activity. In addition, electron transport system activity, glutathione S-transferase activity, and acetylcholinesterase activity were assessed in whole-animal homogenates. At 1%, PP-rGO triggered sublethal stress without affecting survival. At 10%, it caused low toxicity and altered haemocyte profiles. rGO induced high toxicity at 1%, impacting survival and moulting. PP alone caused stress only at 10%. Embedding rGO in a polymer matrix reduces its toxicity compared to free rGO but still enhances PP effects. These findings highlight the need for thorough environmental risk assessment of nanocomposites.