Leachates from weathered polypropylene items, but not from polylactic acid, induce ecotoxicological effects on a marine diatom

Abstract Plastic items released in the marine environment are subject to weathering processes which alter their surface physiochemical properties, and which can induce the leaching of associated chemicals from the polymer matrix to the aquatic media. Even though plastic leachates (i.e., an aqueous solution of released compounds) can induce negative effects on aquatic biota, the effects of plastic leachates from weathered plastics are still poorly known. The goal of our work was to assess the ecotoxicological effects of plastic leachates from pristine and weathered items on a marine diatom. To do so, we exposed the marine diatom Phaeodactylum tricornutum to the leachates from pristine and UV-weathered self-reinforced (SR-) polylactic acid (PLA) and polypropylene (PP) items. As a positive control, we assessed the response of the diatom growth to two associated compounds (dodecan-1-ol and 2,4-di-tert-butylphenol), components of the tested items. Weathered plastic items were obtained after being exposed to 57-day artificial ultraviolet radiation, simulating 18-months of solar exposure in central Europe. Our results indicate that neither leachates from pristine nor weathered SR-PLA items had adverse effects on P. tricornutum growth. This outcome was corroborated by the measured concentrations of associated compounds (i.e. dodecan-1-ol) in leachates, which were at least three orders of magnitude lower than the 72-h EC 50 of diatom growth (dodecan-1-ol: 1.56 mg / L, 2,4,-DTBP: 1.52 mg / L). Leachates from weathered SR-PP items at full-strength concentration induced 51% greater growth inhibition than control treatments, and 43% greater inhibition than leachates from pristine SR-PP items at the same concentration. Our results suggest that leachates from the tested weathered SR-PP items inhibited the population growth of P. tricornutum , although at plastic concentrations above environmentally relevant levels.