Potential toxicity of micronized polyethylene terephthalate microparticles (PET-µPs) on the Manila clam (Ruditapes philippinarum)

Microplastic (µPs) contamination represents a worrisome environmental problem threatening marine ecosystems. Several monitoring studies have revealed the presence of different µPs composed by different polymers floating in the surface waters, but recently µPs have been found also in the deep sediments. This is particularly true for µPs of polyethylene terephthalate (PET), one of the plastic types most commonly used in food and beverage packaging and whose potential toxicity towards the biota is still largely unknown. Considering the high density of PET (1.38 g/cm³), this type of plastic could be potential toxic for organisms that lives in the sediment, such as the bivalves. Thus, the aim of this study was to investigate the ingestion/egestion and the potential adverse effects induced by 7-days exposure to two concentrations (0.125 and 12.5 µg/mL) of micronized, irregular shaped PET microparticles (PET-µPs) towards the Manila clam Ruditapes philippinarum. In order to check the capability to ingest PET-µPs and the possible tissue damage a histological analysis was performed. Furthermore, we relied on a suite of oxidative stress biomarkers in order to investigate the possible alteration of oxidative status and the presence of oxidative damage. Our results evidenced that manila clams were able to ingest PET-µPs without histological alteration to the bivalve tissue. Biomarkers analyses highlighted an alteration of the oxidative status of the gills, leading to lipid peroxidation, while no effect was noted for the digestive gland. Overall, our findings suggest that PET-µPs might represent a treat for organisms that live sunked in sediment.