Critical reassessment of microplastic detection methodologies and abundances in the marine environment

Microplastics (MPs) pose a growing concern in the marine environment, but their global prevalence remains largely unknown due to the absence of precise and standardized detection methods. This is because current techniques used to quantify MPs in marine field studies can feature methodological inaccuracies or limitations, which collectively prevent a global and reliable MP pollution status for being drawn. These inaccuracies are related, for example, to the exclusion of particle sizes within the broad range of MP size intervals or to the level of identification of polymer types by using spectroscopic analysis or specific extraction methods. Once these inaccuracies have been considered and addressed, the reported MP abundances can be recalculated. This resulted in a significant underestimation of the global pollution levels regarding MPs in the 10–5000 µm size range. MP abundances are then shown to be up to 15 times higher than in the data presented in the public domain in marine waters and up to 11 times higher within marine sediments. This study emphasizes the critical need for global and integrated MP studies and encourages current and future MP researchers to adopt standardized protocols for MP analysis to avoid misleading outcomes.