A Newcastle University analysis has estimated that people are ingesting the equivalent of a credit card in plastic every week.
The study, commissioned by the World Wide Fund for Nature (WWF), suggests people consume about 2000 tiny pieces of plastic every week, much of it via bottled and tap water.
The Newcastle researchers, working on a "limited set" of available evidence, found the global average rate of plastic consumption could be five grams a week, 21 grams a month and 250 grams a year.
The No Plastic in Nature: Assessing Plastic Ingestion from Nature to People report is the first global analysis combining data from more than 50 studies on the ingestion of microplastics.
Project co-leader Dr Thava Palanisami said the research would help establish the potential health effects of plastics pollution.
"While the awareness of microplastics and their impact on the environment is increasing, this study has helped to provide an accurate calculation of ingestion rates for the first time," the Newcastle University microplastics researcher said.
"Developing a method for transforming counts of microplastic particles into masses will help determine the potential toxicological risks for humans moving forward."
Dr Palanisami said some of the chemicals used in food and other packaging contained chemicals which were linked to cancer and hormone imbalances.
"The direct evidence is not yet known, but the associated chemicals are already known to cause a carcinogenic impact and endocrine-disturbing behaviour."
Dr Alastair Grant, a professor of ecology at the University of East Anglia in England, told the Newcastle Herald that "even the higher figure" in the report was "unlikely to present any risk to human health".
"Adverse effects of microplastics on animals have only been observed in laboratory experiments at concentrations that are several orders of magnitude higher than those that occur in the environment," he said.
The study found wide regional variations in the amount of plastics in water, twice as much in the US or India compared with Europe or Indonesia.
Dr Palanisami said not enough data was available on Australian water for it to be included in the analysis.
Of the consumables studied, those with the highest recorded plastic levels included shellfish, beer and salt.
The WWF's Richard Leck, who leads the organisation's ocean preservation program in Australia, said the federal government should target the 10 worst single-use plastics, starting with a ban on single-use plastic bags and microbeads.
"It's alarming that plastic pollution has become so all-pervasive that we're now ingesting five grams per week. This information must spur more urgent action to address the plastics crisis," Mr Leck said.
The report calls for governments to play a key role in ensuring the entire chain in the plastic system, from manufacturers to consumers, is accountable for ending plastic pollution.
WWF says it has attracted more than 500,000 signatures to a global petition calling for a legally binding treaty on marine plastics pollution to establish national targets and transparent reporting mechanisms that extend to companies.
"These findings must serve as a wake-up call to governments," WWF international director general Marco Lambertini said.
"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.
"If we don't want plastic in our bodies, we need to stop the millions of tons of plastic that continue leaking into nature every year."