Microplastics are commonly defined as fragments of any type of plastic ranging in size from less than five millimeters in length all the way down to the micron level (which is invisible to the unaided human eye). They cause pollution by entering the land, water and air from a wide variety of sources.
Primary microplastics are plastic fragments or particles that are already 5.0 mm or less before entering the environment, including microfibers from clothing, microbeads, and plastic pellets. Secondary microplastics arise from the breakdown of larger pieces plastic through natural weathering processes after entering the environment, including plastic bottles, plastic bags, fishing nets, microwave containers and pieces of vehicle tires. It is commonly estimated that about 35 percent of all microplastics in the oceans originate from textiles, primarily due to the erosion of polyester, acrylic, or nylon-based clothing, including during washing.
The full effects of microplastics on the environment and human health are still not known. However, there is great cause for concern because (1) there has been a rapid growth in the output and dispersion into the environment of plastics during the past seventy years or so, (2) plastics degrade extremely slowly (often taking hundreds or even thousands of years), and (3) microplastics are easily ingested into and accumulate in the bodies and tissues of many organisms, including humans, from the air, water and food.