Single-use takeaway cups can release millions of microplastic and even smaller nanoplastic particles when filled with hot liquid, according to a new study. These particles, shed from the plastic lining inside paper cups, are a previously overlooked source of microplastic pollution, researchers warn.
The study, published in ACS Food Science & Technology, examined two types of single-use cups: one lined with fossil fuel-based polyethylene (PE) and another with biodegradable polylactic acid (PLA). While PLA-lined cups may seem more environmentally friendly, they released 12 times more microplastic particles than their PE-lined counterparts.
Microplastics are defined as tiny plastic pieces ranging from one micrometer to five millimeters in diameter, while nanoplastics are even smaller, measuring approximately a thousandth the thickness of a human hair. These microscopic pollutants have been detected globally and have been found within the human body.
"Our results show that plastic-lined paper cups release substantial quantities of micro- and nanoscale plastic material when exposed to hot water," said Dr. Elvis Okoffo, an environmental health scientist from the University of Queensland and co-author of the study. "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."
In the research, scientists exposed the cups to hot water and analyzed the liquid. Water kept in a PE-lined cup contained 2.7 million plastic particles per milliliter, while water from a PLA-lined cup contained 4.3 million particles per milliliter. The PLA-lined cups released 12 times the total mass of particles compared to the PE-lined cups, attributed to the larger size of the particles shed.
While the long-term health impacts of microplastic ingestion are still under investigation, studies have linked these particles to inflammation, impaired immune systems, tissue damage, and abnormal organ development in animal and cell-based research. Microplastics have been found in various human organs, including the brain, heart, and placenta. Some research suggests potential links to reproductive, digestive, and respiratory health issues, and even an increased risk of heart attack and stroke.
"Although the researchers don't suggest that customers give up using paper cups just yet, they're calling for regulators to consider implementing safety guidelines or product warnings," Dr. Okoffo stated. "Nanoplastic release should form part of the safety assessment of food-contact materials, particularly products designed for hot beverages."
Product manufacturers could also explore developing cup linings that release fewer plastic particles when exposed to hot liquids. The study notes that chemicals within plastics can leach into the bloodstream, though not all plastics contain harmful chemicals or are equally prone to leaching. Significant knowledge gaps remain regarding the precise human health effects and risks associated with microplastic exposure.