Drinking coffee from a paper cup could lead to the ingestion of thousands of harmful microplastics, new research has warned, amid fears the tiny particles could increase the risk of cancer.

Researchers found storing hot drinks in paper cups releases around 25,000 micron-sized plastic particles into the drink in a matter of minutes.

The study, due to be published in the Journal of Hazardous Materials, revealed the microplastic layer of the cup degrades in just 15 minutes – the amount of time it takes to drink the coffee or tea.

Dr Sudha Goel, study lead author, explained: "An average person drinking three regular cups of tea or coffee daily, in a paper cup, would end up ingesting 75,000 tiny microplastic particles which are invisible to the naked eye.”

Some 264 billion paper cups were produced last year for consuming tea, coffee, chocolate, soft drinks and soups – equivalent to 35 for every person on the planet.

There is emerging concern about the effects of ingesting microplastics, which are typically less than 0.2 inches (5 mm) across – but can be as small as a fiftieth the width of a human hair.

Research published by academics at Arizona State University revealed earlier this year, for the first time, that microplastics can enter human organs.

But they stressed it is not yet known whether the plastics are "just a nuisance or whether it represents a human health hazard".

Some 264 billion paper cups were produced last year for consuming tea, coffee, chocolate, soft drinks and soups – equivalent to 35 for every person on the planet.   

Credit: REUTERS/Simon Dawson

While a report by WWF, published in 2019, found the average person ingests the equivalent of a credit card in plastic each week. It said people are consuming up to 102,000 pieces of plastic, or less than 250 grams each year, with the majority coming from water.

Although the health impacts of microplastics humans still needs further research, experts have linked microplastic pollution to inflammation, infertility and cancer in animals.

Dr Goel, of the Indian Institute of Technology, Kharagpur, said: "Microplastics act as carriers for contaminants like ions, toxic heavy metals such as palladium, chromium and cadmium, as well as organic compounds that are water repelling and can cross over into the animal kingdom.

"When ingested regularly over time, the health implications could be serious."

In this latest study, researchers poured ultra-pure (MilliQ) water at 85 to 90 degrees Celsius into paper cups and then allowed it to sit for 15 minutes.

The liquid was then analysed under a fluorescent microscope for microplastics. Dr Goel described the results as "startling".

IN NUMBERS | The plastic problem

The plastic linings were separately examined for changes in physical, chemical and mechanical properties. Dr Goel said: "We could confirm the release into the MilliQ water of microplastic particles using a scanner.

"A disposable paper cup exposed to hot liquid for 15 minutes will have approximately 10.2 billion submicron sized particles."

A sensitive technique that separates chemicals then identified microplastics in the hot water. Most disturbingly, analysis of the plastic films discovered the presence of heavy metals in the liners.

Experts warned the results should inform discussions around replacing plastic cups with paper ones.

Professor Virendra Tewari, Institute director, said: "This study shows careful consideration needs to be done before the promotion of replacements for bio-hazardous products and environmental pollutants.

"We have been quick to replace plastics cups and glasses with disposable paper cups."

He suggests a return to traditional, disposable terracotta cups that are still used in many parts of India.