Toward an Improved Understanding of the Ingestion and Trophic Transfer of Microplastic Particles: Critical Review and Implications for Future Research

Microplastic particles have been observed in the environment and routinely detected in the stomachs and intestines of aquatic organisms over the last 50 yr. In the present review, information on the ingestion of plastic debris of varying sizes is collated, including data for >800 species representing approximately 87 000 individual organisms, for which plastic debris and microplastic particles have been observed in approximately 17 500, or 20%. The average reported number of microplastic particles/individual across all studies is estimated to be 4, with studies typically reporting averages ranging from 0 to 10 particles/individual. A general observation is that although strong evidence exists for the biological ingestion of microplastic particles, they do not bioaccumulate and do not appear to be subject to biomagnification as a result of trophic transfer through food webs, with >99% of observations from field‐based studies reporting that microplastic particles are located within the gastrointestinal tract. Overall, there is substantial heterogeneity in how samples are collected, processed, analyzed, and reported, causing significant challenges in attempting to assess temporal and spatial trends or helping to inform a mechanistic understanding. Nevertheless, several studies suggest that the characteristics of microplastic particles ingested by organisms are generally representative of plastic debris in the vicinity where individuals are collected. Monitoring of spatial and temporal trends of ingested microplastic particles could thus potentially be useful in assessing mitigation efforts aimed at reducing the emission of plastic and microplastic particles to the environment. The development and application of standardized analytical methods are urgently needed to better understand spatial and temporal trends. Environ Toxicol Chem 2020;39:1119–1137. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.