Ingestion and effects from microplastic (polyethylene) derived from toothpaste on blue mussel (Mytilus galloprovincialis)

Polyethylene (PE) microplastic particles (<5 mm) are found in consumer products such as toothpaste and there is evidence that these particles are ending up in the marine environment. This is why we used PE particles derived from toothpaste as our exposure particles (ranging from 50 µm - 570 µm). Blue mussels are suitable bio-indicators for microplastic pollution since they are sessile and are filtering large volumes of seawater including their ability to bio-concentrate none water-soluble pollutants. To best mimic the exposure scenarios in the marine environment we exposed both virgin PE particles and weathered PE particles (deployed in Outer Oslofjord for 3 weeks) to the blue mussels for a chronic study (21 days) with a concentration of 10mg/L. The mussels did ingest both raw and the weathered particles, however they did ingest 26% more of the weathered particles. They ingested particles up to 383 µM, and to our knowledge this is the first study identifying ingestion of such large microplastic particles in bivalves. This ingestion did cause alteration of the gills and digestive gland and also necrosis in other tissue such as the mantel. Bivalves are eaten whole and are therefore of special concern regarding seafood safety and as our study shows that they are able to ingest PE microplastics particles derived from toothpaste, particles that most likely end up in the marine environment