"Microplastics" is the broad category for several different kinds of plastic bits
that are smaller than 5 mm. Primary microplastics are manufactured
“micro” to serve as the building blocks of many items for modern living.
Secondary microplastics, on the other hand, are never intended to be
tiny. They begin as large plastic objects, and over time in the environment,
wind, waves, and energy from the sun help break them down.
Photos (top to bottom): Nurdles, Tristan Baurick / NOLA.com; Microbeads, Minnesota Pollution Control Agency; Fragments, NOAA; Microfiber, J. Adam Frederick / MDSG; Polystyrene, Will Parson / Chesapeake Bay Program