A quantitative risk assessment framework for mortality due to macroplastic ingestion in seabirds, marine mammals, and sea turtles

Plastic ingestion is a known cause of mortality across taxa, yet the quantitative risk plastic ingestion poses is still poorly understood. Based on data from more than 10,000 necropsies, we estimate the likelihood of mortality due to the gastrointestinal load of various plastic materials—hard, soft, rubber, and fishing debris—for seabirds, marine mammals, and sea turtles. We find that 6 to 405 pieces of ingested macroplastic (or a volume between 0.044 and 39.89 cm3/cm body length) lead to a 90% chance of mortality in these marine species. Importantly, the amount varies depending on plastic types ingested and taxon. Our findings can be used to better understand the mortality risk of macroplastic pollution and inform future risk assessment frameworks.