Microfibres and bivalves: A review of their occurrence and analysis

Microfibres represent the most abundant form of microplastics in marine environments and pose potential risks to ecosystems and human health. Bivalves, widely consumed and commonly used as bioindicators, are particularly susceptible to this contamination. This review synthesizes current knowledge on the occurrence and analysis of microfibres in bivalves, based on 107 studies published since 1977. Microfibres were reported in all major bivalve families, with mussels, oysters, and clams being the most frequently investigated groups. Blue fibres were the most common, followed by transparent and black. Polypropylene, polyethylene, and polyester were the predominant polymers, while regenerated cellulose fibres were also frequently detected. Natural fibres, often considered environmentally benign, present risks comparable to those of synthetic polymers. The literature reveals substantial inconsistencies in sampling strategies, digestion protocols, and polymer identification methods, limiting comparability and reliability of reported data. Most studies employed chemical characterization, primarily Fourier-transform infrared spectroscopy, although analytical conditions were often insufficiently documented. Standardization of methodologies is urgently required to improve data quality and enable robust assessment of ecological and human health risks. Recommendations for harmonizing protocols and enhancing monitoring strategies are provided to support future research and inform mitigation measures addressing microfibre pollution in marine ecosystems and seafood safety.