Microplastics are fragments of any type of plastic less than 5 mm (0.20 in) in length,[1] according to the U.S. National Oceanic and Atmospheric Administration (NOAA)[2][3] and the European Chemicals Agency.[4] They cause pollution by entering naturalecosystems from a variety of sources, including cosmetics, clothing, food packaging, and industrial processes.[1][5]
The term microplastics is used to differentiate from larger, non-microscopic plastic waste. Two classifications of microplastics are currently recognized. Primary microplastics include any plastic fragments or particles that are already 5.0 mm in size or less before entering the environment.[5] These include microfibers from clothing, microbeads, plastic glitter[6] and plastic pellets (also known as nurdles).[7][8][9] Secondary microplastics arise from the degradation (breakdown) of larger plastic products through natural weathering processes after entering the environment.[5] Such sources of secondary microplastics include water and soda bottles, fishing nets, plastic bags, microwave containers, tea bags and tire wear.[10][9][11][12] Both types are recognized to persist in the environment at high levels, particularly in aquatic and marine ecosystems, where they cause water pollution.[13]
35% of all ocean microplastics come from textiles/clothing, primarily due to the erosion of polyester, acrylic, or nylon-based clothing, often during the washing process.[14] However, microplastics also accumulate in the air and terrestrial ecosystems.
Because plastics degrade slowly (often over hundreds to thousands of years),[15][16] microplastics have a high probability of ingestion, incorporation into, and accumulation in the bodies and tissues of many organisms.[1] The toxic chemicals that come from both the ocean and runoff can also biomagnify up the food chain.[17][18] In terrestrial ecosystems, microplastics have been demonstrated to reduce the viability of soil ecosystems.[19][20] As of 2023, the cycle and movement of microplastics in the environment was not fully known.[5] Deep layer ocean sediment surveys in China (2020) show the presence of plastics in deposition layers far older than the invention of plastics, leading to suspected underestimation of microplastics in surface sample ocean surveys.[21]
^Klein S, Dimzon IK, Eubeler J, Knepper TP (2018). "Analysis, Occurrence, and Degradation of Microplastics in the Aqueous Environment". In Wagner M, Lambert S (eds.). Freshwater Microplastics. The Handbook of Environmental Chemistry. Vol. 58. Cham.: Springer. pp. 51–67. doi:10.1007/978-3-319-61615-5_3. ISBN978-3319616148. See Section 3, "Environmental Degradation of Synthetic Polymers".
^Nex, Sally (2021). How to garden the low carbon way: the steps you can take to help combat climate change (First American ed.). New York. ISBN978-0744029284. OCLC1241100709.{{cite book}}: CS1 maint: location missing publisher (link)