How do microplastics form and what are their ecological risks?

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Microplastics form mainly when larger plastic items break into smaller pieces through weathering, with fragmentation driven by waves, abrasion, and sun-driven degradation helping the process. Once these tiny particles are created, they enter aquatic systems and are easily ingested by a wide range of organisms—from plankton to fish and seabirds—leading to physical harm such as gut blockage or reduced feeding, which can affect growth and survival. They also act as carriers for chemicals: additives in the plastics can leach out, and hydrophobic pollutants in the environment can sorb onto the plastic surface, so when organisms ingest them, those chemicals can be released and cause toxic effects. Microplastics can also host microbial communities and move contaminants through ecosystems, amplifying ecological risk. This combination—formation by fragmentation and the prevalence of ingestion with potential chemical toxicity—best captures why microplastics are a concern.