Comparisons between ingestion, rejection, and egestion of microbeads by burrowing clams, Meretrix meretrix and Paphia undulata: Implications for health risk of shellfish consumption.

Two burrowing clam species, namely Meretrix meretrix and Paphia undulata, were offered two sizes (small: 45-53 μm, and large: 106-125 μm) of fluorescent red polyethylene microbeads, and the ingestion (number of MPs in the body tissue and faeces) and rejection (number of MPs in pseudofaeces) of MPs investigated. Overall, MP beads ingested were 36 % more than those rejected. There was also a significant interaction between the size and fate of MPs. For both species, significantly more small beads were ingested than rejected, but there was no difference for the large beads. P. undulata ingested more MPs than M. meretrix and both species could depurate all the ingested MPs in 72 h, although a longer time was needed for the former species. The results can provide guidance on seafood selection and pre-treatment to minimize the number of MPs ingested by humans.