Edible bivalves and gastropods as bioindicators of MP pollution: Contamination patterns, and environmental...

Microplastic (MP) pollution is widespread in marine ecosystems, with edible bivalves and gastropods acting as important bioindicators due to their feeding modes and direct relevance to seafood consumption. This review synthesizes global evidence on MP contamination in these taxa, focusing on spatial patterns, particle characteristics, analytical methods, bioaccumulation, ecological risk, and human exposure. Gastropods showed higher mean MP concentrations (6.35 mps g^-1 ww) than bivalves (2.89 mps g^-1 ww), with wild populations generally more contaminated than cultured ones. Fibers were the dominant MP type, followed by fragments, while polyethylene, polypropylene, and polyethylene terephthalate were the most frequent polymers. The mean highest recorded bivalve contamination (9.18 mps g^-1 ww) was observed in South America, indicating a significant hotspot. Pollution load index revealed comparatively higher contamination risk in Asia and Europe. Human exposure estimates varied widely across regions, strongly influenced by both environmental contamination and seafood consumption rates. Methodological inconsistencies in digestion, density separation, and identification approaches limit data comparability and highlight the need for standardized protocols. Bivalves are more reliable indicators of water-column MPs, whereas gastropods better reflect sediment-associated contamination but remain less standardized for monitoring applications. Overall, this review emphasizes the need for harmonized analytical methods, expanded geographic coverage, and integrated environmental, human health risk frameworks to improve global MP assessment and policy development.