Paper cups lined with plant-based plastic are often marketed as the eco-friendly choice at coffee shops and cafeterias. But new research by University of Queensland scientists suggests that when it comes to shedding tiny plastic particles into hot beverages, these biodegradable cups may actually be worse offenders than their conventional counterparts.
Shi et al. demonstrate that biodegradable plastics can release nanoplastics during routine use, highlighting a previously overlooked pathway of consumer exposure. Image credit: Alexas Fotos.
Biodegradable plastics are increasingly promoted as sustainable alternatives to conventional plastics.
However, their potential to release micro- and nanoplastics during use remains poorly understood.
“Single-use paper cups are used every day by millions of people around the world for coffee, tea and other hot beverages,” said Dr. Elvis Okoffo, co-lead author of the study.
“A cup made mostly of paper does not mean that the cup is plastic-free because many contain a thin plastic lining that provides water resistance and structural integrity.”
“Our results show that plastic-lined paper cups release substantial quantities of micro- and nanoscale plastic material when exposed to hot water.”
In the study, the researchers compared single-use paper cups lined with polylactic acid (PLA) — a corn- or sugarcane-derived plastic marketed as compostable — against cups lined with conventional polyethylene (PE).
They found that the PLA-lined cups released roughly twelve times more plastic particle mass into hot water than the polyethylene versions.
The PLA cups shed about 4.3 million nanoparticles per milliliter, compared with 2.7 million particles per milliliter for the polyethylene cups.
Using a combination of advanced detection techniques, including mass spectrometry, light-scattering analysis and electron microscopy, the authors were able to confirm that the PLA lining released genuine nanoplastic particles, in two size ranges roughly comparable to large viruses and small bacteria.
“The study contributes to growing evidence that new plastic products used for food storage and preparation represent a significant yet often overlooked source of human exposure via ingestion,” Dr. Okoffo said.
“This does not mean that people should necessarily stop using paper cups, or that PLA is inherently unsafe.”
“But the impact of plastic particles on human health is unclear and we know that the chemicals in plastic are not meant to be consumed.”
“The materials used in food-contact products need to be evaluated not only for their environmental sustainability, but also for their particle-release behavior during everyday use.”
“This study fills an important knowledge gap about how single use paper cups lined with plastic materials can contribute to daily plastic exposure.’’
“Consumers should be provided with information about the materials used to line paper cups and called for regulators to consider safety guidelines or product labels warnings.”
“Policymakers and regulators could consider whether testing for micro- and nanoplastic release should form part of the safety assessment of food-contact materials, particularly products designed for hot beverages.”
“Product manufacturers could also consider developing cup linings that release fewer plastic particles when exposed to hot liquid.”
“By combining better product design, improved labelling, and public awareness, we can help limit the amount of plastic entering both our bodies and the environment.”
The results appear in the journal Food Science & Technology.
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Ke Shi et al. Release of Nanoplastic and Microplastic from Polyethylene and Polylactic Acid Lined Single Use Paper Cups. ACS Food Sci. Technol, published online August 25, 2026; doi: 10.1021/acsfoodscitech.6c00541
