Sources and pathways of microplastics in waterbodies

Microplastics arise through two main pathways. Primary microplastics are intentionally manufactured at small sizes for industrial or commercial purposes, such as cosmetic microbeads, plastic pellets used in manufacturing, and synthetic fibers released from textiles during washing (Coyle et al., 2020). These particles enter aquatic ecosystems directly through wastewater discharge, stormwater runoff, or accidental industrial losses. Secondary microplastics are formed when larger plastic debris, including bottles, bags, and fishing nets, undergo degradation. Ultraviolet radiation weakens polymers through photodegradation, while mechanical forces such as waves, wind, and abrasion with sand and rocks break plastic into progressively smaller fragments (Andrady, 2017).