Biological responses of Chironomus sancticaroli to exposure to naturally aged PP microplastics under realistic concentrations

Abstract Microplastic (MP) is yet another form of chronic anthropogenic contribution to the environment. MP are plastic particles (< 5 mm) that have been widely found in the most diverse natural environments, but their real impacts on ecosystems are still under investigation. Here, we studied the toxicity of naturally aged secondary polypropylene (PP) MP after constant exposure to ultraviolet radiation (26 µm) to larvae of Chironomus sancticaroli, a dipteran species. The concentrations tested were 13.5; 67.5; and 135 items.g -1 of dry sediment. C. sancticaroli organisms were investigated for fragment ingestion, mortality and changes in enzymatic biomarkers after 144 hours of exposure. The organisms were able to ingest MP from the first 48 hours, and the amount of items internalized was dose-dependent and time-dependent. Overall, the results show that mortality was low, being significant at the lowest and highest concentrations (13.5 and 135 items.g -1 ). Regarding changes in enzyme markers, after 144 hours MDA and CAT activities were both significantly altered (increased and reduced, respectively), while SOD and GST levels were unchanged. In the present study, naturally aged polypropylene MP induced biochemical toxicity in C. sancticaroli larvae, with toxicity being higher according to exposure time and particle concentration.