Plastic pollution is now so widespread that you may be ingesting 5g a week, the equivalent of eating a credit card, according to a study commissioned by the environmental charity WWF International.

The study by Australia's University of Newcastle said the largest source of plastic ingestion was from tap and especially bottled water.

In the United States, 94.4% of tap water samples contained plastic fibres, with an average of 9.6 fibres per litre. 

European water was less polluted, with fibres showing up in only 72.2% of water samples, and only 3.8 fibres per litre.

Another major source was shellfish, which tended to be eaten whole so the plastic in their digestive system was consumed too. Nearly invisible bits of polymer were also found in beer and salt.

"Since 2000, the world has produced as much plastic as all the preceding years combined, a third of which is leaked into nature," the report said.

The average person could be consuming 1,769 particles of plastic every week from water alone, it said.

The findings, drawn from 52 peer-reviewed studies, are the first to estimate the sheer weight of plastics consumed by individual humans: about 250g over the course of a year.

The amount of plastic pollution varies by location, but nowhere is untouched, said the report.

"Not only are plastics polluting our oceans and waterways and killing marine life, it's in all of us," said Marco Lambertini, director general of WWF International.

"If we don't want it in our bodies, we need to stop the millions of tons of plastic that continue leaking into Nature every year."