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Microplastics are small plastic particles in the environment that are generally between .〔Browne, Mark A: "Ingested microscopic plastic translocates to the circulatory system of the mussel, Mytilus edulis (L.)", ''Environmental Science & Technology'', 42(13), pp. 5026–5031, 2008〕 They can come from a variety of sources, including cosmetics, clothing, and industrial processes. Two classifications of microplastics currently exist: primary microplastics are manufactured and are a direct result of human material and product use, and secondary microplastics are microscopic plastic fragments derived from the breakdown of larger plastic debris.〔Patel, M.M., Goyal, B.R., Bhadada, S.V., Bhatt, J.S., Amin, A.F., 2009. Getting into the brain: approaches to enhance brain drug delivery. CNS Drugs 23, 35–58.〕 Both types are recognized to persist in the environment at high levels, particularly in aquatic and marine ecosystems. Because plastics do not break down for many years, they can be ingested and incorporated into the bodies and tissues of many organisms.〔Grossman, Elizabeth: "How Plastics from Your Clothes Can End up in Your Fish", Time, 15 Jan. 2015, http://time.com/3669084/plastics-pollution-fish/〕 The entire cycle and movement of microplastics in the environment is not yet known, but research is currently underway to investigate this issue. ==Classification== ===Primary microplastics=== These are particles of plastics that are purposefully manufactured to be of a microscopic size. They are usually used in facial cleansers and cosmetics, or in air blasting technology. In some cases, their use in medicine as vectors for drugs was reported.〔 Microplastic ‘‘scrubbers’’, used in exfoliating hand cleansers and facial scrubs, have replaced traditionally used natural ingredients, including ground almonds, oatmeal and pumice. Primary microplastics have also been produced for use in air blasting technology. This process involves blasting acrylic, melamine or polyester microplastic scrubbers at machinery, engines and boat hulls to remove rust and paint. As these scrubbers are used repeatedly until they diminish in size and their cutting power is lost, they often become contaminated with heavy metals (e.g. Cadmium, Chromium, and Lead).〔Cole Matthew, 2011, Microplastics as contaminants in the marine environment: A review, Marine Pollution Bulletin, Nr. 62, pp. 2588-2597〕 ===Secondary microplastics=== These are described as microscopic plastic fragments derived from the breakdown of larger plastic debris, both at sea and on land. Over time, a culmination of physical, biological and chemical processes can reduce the structural integrity of plastic debris, resulting in fragmentation. It is considered that microplastics might further degrade to be nanoplastic in size, although the smallest microparticle reportedly detected in the oceans at present is 1.6 µm in diameter.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「microplastics」の詳細全文を読む スポンサード リンク
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