Quantitative analysis of high commercial value Australian seafood for selected plastics

A third of the plastic waste produced globally ends up in the environment, including aquatic environments. In the marine systems, plastic fractures into smaller pieces forming microplastics. Given the vulnerability of marine organisms to microplastic exposure, seafood has been identified as one of the largest sources of human plastic ingestion, and is among the most consumed foods worldwide. Recent studies have tried to estimate human plastic ingestion from food based on a low number of semi-quantitative studies that lack standardized methods for reporting results. These mainly identify microplastics by visual techniques and attempt to quantify by counting particles and confirming polymer identity with spectroscopy techniques. However, these methods are exhaustive, time-consuming and potentially do not account for the fraction of smaller plastics that cannot be visually identified or which appear similar to non-plastics. The aim of this study is to develop a simple seafood sample processing and analysis method capable of accurately identifying the types of polymers within the samples as well as providing reliable quantitative measurements of each. The method consists of sample digestion followed by accelerated solvent extraction and analysis using pyrolysis gas chromatography coupled to mass spectrometry (Pyr-GC/MS). This method allows the quantification of five different polymers in seafood (polystyrene, polyethylene, polyvinyl chloride, polypropylene and poly (methyl methacrylate)). High commercial value seafood was selected, including: oysters, prawns, crabs, squid, sardines and barramundi. The predominant polymer found in samples was polyethylene with 23 to 400 µg per gram of tissue. Crabs and barramundi contained the highest plastic concentration, followed by sardines. Our results also show that plastic concentration is variable among species and that microplastic content differs between organisms of the same species. These findings highlight the need to consider the analysis of different organisms when doing environmental monitoring and the importance of a representative sample size.