The long-term effects of ingested plastic on people aren't yet known. But in rodents, ingested microplastics can impair the function of the liver, intestines, and exocrine and reproductive organs.

Especially at risk of ingesting plastic are scavenging birds. For example, New World vultures regularly forage at landfills, and have been observed to leisurely pick at synthetic materials such as boat seats, rubber seals, and roofs.

Now, researchers from the U.S. have shown that the amount of plastic ingested by black and turkey vultures (Coragyps atratus and Cathartes aura) can be predicted from their location on suburban and exurban maps. This isn't just a distinction between country versus city birds; the amount ingested depends on the local density of human commerce within urbanized landscapes. These findings are published in Frontiers in Ecology and Evolution.

"Here we show that black vultures and turkey vultures in areas with more urban development and a greater density of commercial food providers ingest more plastic," said Hannah Partridge, a doctoral student at the Department of Geography and Earth Sciences of the University of North Carolina at Charlotte, and the study's first author.