Single-use paper cups used for takeaway coffee and other hot beverages can release millions of plastic particles when exposed to hot liquids, according to a study by researchers at the University of Queensland. The researchers examined paper cups lined with fossil-based polyethylene (PE) and polylactic acid (PLA), a biodegradable plastic alternative, and found that both types released microplastic and nanoplastic particles during testing.

The study found a significant difference between the two types of linings. PLA-lined cups released about 12 times more particle mass than PE-lined cups in the experiments. Researchers measured approximately 4.3 million nanoparticles per millilitre from PLA-lined cups, compared with around 2.7 million particles per millilitre from PE-lined cups.

Dr Elvis Okoffo of the Queensland Alliance for Environmental Health Sciences said the findings challenge the assumption that paper cups are entirely plastic-free. Although the cups are primarily made from paper, many use a thin plastic lining to provide water resistance and maintain structural integrity. The particles detected in the study were extremely small, with nanoparticles measuring around a thousand times thinner than a human hair.

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The researchers stressed that the findings do not establish that paper cups or PLA-lined products are inherently unsafe. Instead, the study adds to growing research into potential human exposure to microplastics and nanoplastics through food and drink. Okoffo said food-contact materials should be assessed not only for environmental sustainability but also for how many particles they may release during normal use.

The study also called attention to the need for greater information about materials used in food and beverage packaging. Researchers suggested that regulators could consider testing microplastic and nanoplastic release as part of safety assessments for food-contact products, particularly those designed for hot beverages. Manufacturers could also explore alternative cup linings that release fewer plastic particles when exposed to heat.

Published in ACS Food Science & Technology, the research highlights an area that remains under investigation rather than providing evidence that consumers must stop using takeaway paper cups. The researchers said better product design, clearer labelling and greater public awareness could help reduce plastic particle exposure while encouraging the development of safer materials for everyday food and beverage use.

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