What do you call extremely small pieces of plastic debris, less than 5 mm in size?

Microplastics refer to extremely small pieces of plastic debris that are typically defined as being less than 5 mm in size. This category of plastic can result from the breakdown of larger plastic items through processes such as photodegradation and mechanical wear. Microplastics are a significant environmental concern because they can enter ecosystems and potentially harm wildlife and human health.

Nanoplastics, while also referring to tiny plastic particles, specifically denote even smaller particles that are less than 1 micrometer in size, thus distinguishing them from microplastics. Macrophages are immune cells that play a role in phagocytosis, and they are not related to plastic debris. Ultrafiltration particles pertain to a filtration process and do not specifically describe plastic materials. Therefore, "microplastics" is the most accurate term for plastic debris under 5 mm.