Plastic in the environment eventually falls apart into ever-smaller pieces. Microplastics are pieces smaller than half a centimeter but can be so small that they are no longer visible to the naked eye. Nanoplastics are barely visible even under the most modern microscopes. Microplastics released through the wear of other plastic materials, such as fibers from synthetic clothing or the abrasion of car tires – these are secondary microplastics. Primary microplastics include microplastics that manufacturers consciously add to personal care products or paints because they fulfill a specific function. These microplastics end up in the ocean easily via drains or through other routes.
For more information, check out the factsheet from RIVM