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Are we really producing environmentally relevant reference materials for microplastic studies?
Summary
This study evaluated whether laboratory-produced microplastic reference materials used in research adequately represent the physical and chemical properties of particles found in natural environments. Results found substantial differences between commercially available reference materials and environmentally weathered microplastics, undermining the ecological relevance of studies using pristine materials.
The tremendous increase in plastic pollution and its adverse effects on the environment and organisms makes it important to better understand the effects of microplastics (MPs). To do so, the first step is to produce environmentally relevant MPs, known as reference materials. These reference materials should be similar to the particles found in the environment, according to physicochemical properties. Nowadays there are some ways to produce reference materials, however, whether these particles can accurately represent the particles formed in nature or not, is yet to be determined. In this project, we aimed to compare the physicochemical and toxicological properties of the reference material produced in the lab by exposing LDPE plastic bags to UV-C, with the MPs produced by naturally aged plastic bags. For this purpose, pristine and post-consumer recycled plastics (PCRs) were exposed to UV-C for 14 days and then the plastics were cryomilled to produce MPs. The naturally aged plastic bag was sampled from the Norwegian coast. The surface chemistry of all the plastic bags was analyzed using FTIR. The morphology of the plastic bags and MPs were studied by SEM. The size distribution and the number of MPs were analysed using a coulter counter and the chemical composition of the plastic bags was examined via Py-GC/MS. The toxicity of naturally and artificially aged polyethylene was studied by exposing Daphnia magna to the extracts from plastic bags following OECD 211 guidelines. The results showed that the naturally aged plastic bags produce more, and smaller MPs compared to the reference materials produced in the lab. There were also differences in toxicity: the reference materials from the lab affected mortality and reproduction, whereas naturally aged extracts affected the size and oxygen consumption in D.Magna. This study showed by using accelerated aging methods we are not necessarily producing environmentally relevant MPs. Also see: https://micro2024.sciencesconf.org/559333/document