Microplastics (MPs) are small pieces of plastics. They are ubiquitous in the environment and can enter the freshwater environment from surface run-off and wastewater effluent (treated and untreated), industrial effluent, degraded plastic waste, and atmospheric deposition. They are not usually destroyed but convert into one phase to another. They are a source of air pollution, occurring in dust and airborne fibrous particles. Mostly MPs are non-biodegradable while some MPs are biodegradable, which can be decomposed in the presence of ultraviolet (UV) light or by the action of microorganisms. Popular methods: chemical, spectroscopic, and thermo-analytical are available for the determination of the chemical composition and size of plastic particles. This chapter discusses the uses, health hazards, sources, and transport of MPs particles.