Plastic is non-biodegradable and over time, it breaks down into smaller and smaller pieces.

https://www.istockphoto.com/vector/the-disposable-plastic-breaks-up-into-small-pieces-gm1290528709-385910362

Over 90% of plastic pollution is made up of microplastics smaller than your fingernail.

https://depositphotos.com/photo/micro-plastic-small-plastic-pellets-finger-378324682.html

Particles smaller than 5mm are known as microplastics.

https://www.swimdrinkfish.ca/lake-ontario-waterkeeper/blog/2016/11/15/zooming-in-on-the-five-types-of-microplastics

These particles break down even further into nanoparticles (smaller than 0.1 micrometer in size) which you cannot see even with a microscope. Microbeads are solid plastic particles from 10 micrometers to 1mm in size and are used in cosmetics and personal care products such as toothpaste. Plastic can also be found in the form of microfibers. Every time we wash clothes made of nylon, polyester or acrylic, thousands of microfibers are released. It has been reported that more than 800,00 microscopic microfibers are released during one washing machine cycle.

Once in the environment, these microplastics cannot be removed and forever remain in our environment.