Tissue-specific accumulation and human exposure risk of microplastics in the edible clam Meretrix petechialis

Clams constitute an important source of food for humans. Ingestion of microplastics through the consumption of the edible clam Meretrix petechialis , poses a threat to both human health and the environment. This study revealed that the average microplastic abundance in the clams was 8.62 ± 5.46 items/g (wet weight) or 36.82 ± 12.73 items/ind. Microplastic abundance in all studied clam tissues showed significant differences, which in the inflow and outflow siphons and gills of the clams was significantly higher than those in other tissues. Microplastics in the inflow and outflow siphons, gills and viscera were derived from the ingestion process, whereas those in foot, mantle, and adductor muscles were derived from adherence. The most abundant morphotype was fiber. The dominant polymer types were polyethylene (31.33%), chlorinated polyethylene (23.54%) and polypropylene (23.39%). The size range of 101–500 μm was the most abundant microplastic size. The most common color of microplastics identified in clams was blue. The average intake of microplastics by coastal residents in the study area through Meretrix petechialis consumption was approximately 11295.65 items/person/year. Results of the pollution load index and chemical composition risk assessments indicated that microplastics in the clams posed a threat to both the environment and human food safety.