Overview
- Published in PNAS, the analysis compiled 10,412 necropsies across 57 seabird species, 31 marine mammal species and all seven sea turtle species to model when ingested plastic becomes deadly.
- As few as six pea‑sized pieces of rubber were 90% likely to kill seabirds, less than three sugar cubes worth could kill birds like puffins, and around 29 pieces of plastic were often lethal for marine mammals.
- The study found material‑specific risks: seabirds are especially vulnerable to rubber and hard plastics, marine mammals to soft plastics and fishing gear, and sea turtles to both hard and soft plastics.
- Plastic was present in the digestive tracts of 35% of seabirds, 12% of marine mammals and 47% of sea turtles examined, yet the authors focused only on acute gastrointestinal injury, meaning total harms are likely underestimated.
- Authors and outside experts say the quantified thresholds can inform policies such as bans on balloons and plastic bags, improved waste collection and recycling, and cleanups as oceans receive more than 11 million metric tonnes of plastic each year with UN projections of steep growth.