A central role for fecal matter in the transport of microplastics: An updated analysis of new findings and persisting questions

Microplastics are commonly known to be excreted in feces after being ingested by organisms, and fecal analysis has become an important tool for monitoring the extent of microplastic exposure by organisms and humans. While the number of studies investigating feces for microplastics is increasing, understanding their role and fate in the environment is critical in microplastic pollution research. This paper aims to review the presence and characteristics of microplastics detected in the feces of various organisms, including humans, as well as to uncover their fate and dispersion in the environment by highlighting several examples and combining data from experimental studies. Our analysis indicated that feces act as a microplastics transporter (between ecosystems) and disperser of microplastic pollution in the surrounding environment (i.e., aquatic, and terrestrial). Microplastics released from feces can extend their lifespan, become bioavailable to organisms, and serve as a vector for contaminants and microorganisms associated with plastic/feces. Hence, it is crucial to investigate the concentration, characteristics, and distribution of microplastics in feces and to consider these when designing environmental monitoring for microplastics in a region of interest. In addition, we suggested challenges that are important for investigations into microplastic pollution and feces on identifying pollution levels and ecological threats.