Plastic Ingestion Risk
Modeling Wildlife Mortality Risk From Ingested Plastics
Widespread concern about plastics being swallowed by marine life—which can lead to their deaths—has fueled calls to determine how much and which types of plastic are riskiest for ocean wildlife. This has never successfully been done for a broad number of marine species until now.
Ocean Conservancy researchers and our academic collaborators around the world have developed scientific models that quantify the risk of marine wildlife deaths associated with the ingestion of macroplastics (greater than 5mm in size or the diameter of a pencil eraser), including many single-use plastic products that are commonly encountered in Ocean Conservancy’s International Coastal Cleanup®. These models are based on more than 10,000 necropsy datapoints and determine the likelihood of mortality for sea turtles, seabirds and marine mammals based on the amount of plastic found in their gastrointestinal tracts.
This research, published in November 2025 in the scientific journal Proceedings of the National Academy of Sciences (PNAS), represents the most comprehensive mortality risk assessment conducted for macroplastic ingestion to date, building extensively on previous work both in terms of the sample size of individuals considered, and the complexity of the modeling approach. Most important for policy, this work emphasizes the risk macroplastic pollution poses to animal health, and that risk varies by animal and plastic type.
In some cases, just one piece of ingested plastic led to animal death. Rubber items like balloons were the deadliest for seabirds, while soft plastics were deadliest for sea turtles and marine mammals. Fishing debris and hard plastics were also deadly for marine mammals and sea turtles, respectively. Therefore, actions taken by governments, corporations and even individuals that prevent plastics from entering the environment, as well as interventions like beach cleanups that remove plastic pollution from coastlines, are critical for protecting marine species.
“The lethal dose varies based on the species, the animal’s size, the type of plastic it’s consuming, and other factors, but overall it’s much smaller than you’d think, which is troubling when you consider that more than a garbage truck’s worth of plastics enters the ocean every minute.”
“This study reminds us that plastic bags, fishing gear, and other items continue to threaten animals big and small.”