A new study sponsored by the environmental group WWF says that people could be ingesting a credit card sized amount of microplastics every week.
The study, which says it is the first to analyze global research looking at microplastics ingestion, reported that the largest source of the plastics is drinking water, both bottled and tap. It accounted for 88 percent of the microplastics sources identified.
Other identified sources in the study from the World Wildlife Fund for Nature included shellfish, because they are often eaten whole, along with beer and salt.
Both WWF and the study authors at the University of Newcastle in Australia said that more research is needed to understand potential health effects from the ingestion and to understand the distribution of microplastics in the environment.
They noted, for example, ongoing work to create a 3D map of ocean plastic litter by 2022, allowing for better estimates of plastic ingestion based on type of polymer and particle size.
The study reported that worldwide, people eat about 5 grams of plastic per week, the equivalent of a credit card, which adds up to about 250 grams a year.
It said the highest levels were found in the United States, India and Lebanon, about twice the amount reported in studies in Europe, Indonesia, Uganda and Ecuador.
"These findings must serve as a wake-up call to governments," said Marco Lambertini, director general of Gland, Switzerland-based WWF International. "Not only are plastics polluting our oceans and waterways and killing marine life — it's in all of us and we can't escape consuming plastics."
WWF called for a global treaty on plastics, with national targets on reducing plastic pollution, and said government responses thus far have been inadequate.