In the aquatic environment, plastics may release several hazardous substances of severe ecotoxicological concern not covalently bound to the polymers. The aim of this study was to examine the adverse effects of leachates of different virgin polymers, polypropylene (PP), polyethylene (PE), and polystyrene (PS) on marine microalgae Dunaliella tertiolecta. The tests carried out on D. tertiolecta included: growth inhibition, oxidative stress (DCFH-DA), and DNA damage (COMET assay). Polypropylene and PS leachates produced growth inhibition at the lowest concentration (3.1% of leachate). In contrast, a hormesis phenomenon was observed with PE leachates. An algae inhibition growth ranking (PP>PS>PE) was noted, based upon EC50 values. Reactive oxygen species (ROS) generated were increased with leachates concentrations with PS exhibiting the highest ROS levels, while a marked genotoxic effect (30%) was found only with PP. All leachates were free from detectable quantities of organic compounds (GC/MS) but showed the presence of transition, post-transition and alkaline earth metals, metalloids, and nonmetals (<limit of quantification (LOQ) to 83.5 µg/L). Therefore, the observed toxic action might reasonably be attributable to the presence of metals and in conjunction with polymeric actions. This investigation underlines the need to better characterize the potential impact of virgin polymers.
Keywords: Comet assay; dunaliella tertiolecta; growth inhibition; metal content; oxidative stress; plastic.