Effects of petroleum-based and biopolymer-based nanoplastics on aquatic organisms: A case study with mechanically degraded pristine polymers

Mismanaged plastic litter submitted to environmental conditions may breakdown into smaller fragments, eventually reaching nano-scale particles (nanoplastics, NPLs). In this study, pristine beads of four different types of polymers, three oil-based (polypropylene, PP; polystyrene, PS; and low-density polyethylene, LDPE) and one bio-based (polylactic acid, PLA) were mechanically broken down to obtain more environmentally realistic NPLs and its toxicity to two freshwater secondary consumers was assessed. Thus, effects on the cnidarian Hydra viridissima (mortality, morphology, regeneration ability, and feeding behavior) and the fish Danio rerio (mortality, morphological alterations, and swimming behavior) were tested at NPLs concentrations in the 0.001 to 100 mg/L range. Mortality and several morphological alterations were observed on hydras exposed to 10 and 100 mg/L PP and 100 mg/L LDPE, whilst regeneration capacity was overall accelerated. The locomotory activity of D. rerio larvae was affected by NPLs (decreased swimming time, distance or turning frequency) at environmentally realistic concentrations (as low as 0.001 mg/L). Overall, petroleum- and bio-based NPLs elicited pernicious effects on tested model organisms, especially PP, LDPE and PLA. Data allowed the estimation of NPLs effective concentrations and showed that biopolymers may also induce relevant toxic effectsThe authors acknowledge the financial support provided by the Spanish Government (Ministerio de Ciencia e Innovación): PID2020-113769RBC21/22, PLEC2021-007693 and the Thematic Network of Micro- and Nanoplastics in the Environment (RED2018-102345-T, EnviroPlaNet Network) and by the Portuguese Government: Project NanoPlanet (2022.02340.PTDC) and financial support to CESAM (UIDP/ 50017/ 2020+UIDB/50017/2020+LA/P/0094/2020), through FCT/MCTES. MTB is the recipient of a FPU (FPU17/01789) pre-doctoral contract by the Spanish Ministerio de Ciencia, Innovación y Universidade