Abstract
Microplastic pollution has been reported in marine, freshwater, and terrestrial ecosystems, from the sea surface to sediments, from beaches to the deep sea, from lakes to rivers, from the tropics to the poles, and in a wide range of organisms representing different trophic levels. Our current understanding of microplastic behavior has increased in recent years, but we still lack the ability to reliably predict exposure hotspots or exposure scenarios. This is further complicated by degradation processes, biofouling, and ingestion by organisms that change plastic particle properties and result in largely unpredictable changes to their environmental fate. While the quantity of data available on microplastic concentrations in different environmental compartments and different species has increased significantly, this is not matched with a comparable amount of experimental microplastic uptake, accumulation, and effects data, especially for organisms in freshwater and terrestrial environmental compartments. This chapter provides an overview of the current state of knowledge concerning the sources, fate, uptake, accumulation, and effects of microplastic in different environmental compartments. The roles of degradation, biofouling, and additive chemical content, as well as more uptake and mechanistic effects studies utilizing relevant microplastic reference materials, are highlighted as challenges that need to be addressed moving toward risk assessment of microplastic pollution.