That seemingly innocuous morning takeaway coffee could be delivering more than just a caffeine hit. New scientific research has uncovered that plastic and plastic-lined disposable cups shed thousands of microplastic fragments directly into your drink, with heat acting as a primary trigger for this release.
The Scale of the Problem and What Are Microplastics?
The study, co-authored by research fellow Xiangyu Liu and published in the Journal of Hazardous Materials: Plastics in January 2026, highlights a staggering global habit. An estimated 500 billion single-use hot beverage cups are used annually worldwide. In Australia alone, the figure reaches 1.45 billion cups and 890 million plastic lids each year.
Microplastics are tiny plastic particles, ranging from the size of a speck of dust up to a sesame seed. They can break off from larger items or be released directly from products during everyday use, ultimately finding their way into our environment, food, and bodies. While the long-term health impacts are still being actively researched, scientists agree that awareness of potential sources is crucial.
Heat and Material: The Critical Factors
The research team from Griffith University in Brisbane first conducted a meta-analysis of 30 existing studies. They found that temperature was the most significant driver of microplastic release, with reported levels ranging from hundreds to over 8 million particles per litre. Surprisingly, the length of time a drink sat in the cup was not a consistent factor.
To test this in the real world, the scientists collected and analysed 400 disposable cups from Brisbane cafes. They compared all-plastic polyethylene cups with paper cups featuring a thin plastic lining, testing them at both iced coffee (5°C) and hot coffee (60°C) temperatures.
The results were clear. Firstly, material matters: plastic-lined paper cups released fewer microplastics than pure plastic cups at both temperatures. Secondly, heat dramatically increases shedding. For all-plastic cups, switching from cold to hot liquid caused a 33% surge in microplastic release.
Using high-resolution imaging, the researchers discovered that all-plastic cups have much rougher inner surfaces. Heat softens the plastic, causing it to expand and contract, which worsens these surface irregularities and makes it easier for particles to break away into the beverage.
Managing Your Microplastic Exposure
The study calculates that a person drinking 300ml of coffee daily from a polyethylene cup could ingest approximately 363,000 microplastic particles every year. However, you don't need to abandon your coffee ritual.
The most effective solution is to use a reusable cup made from stainless steel, ceramic, or glass, as these materials do not shed microplastics. If a disposable cup is unavoidable, opting for a plastic-lined paper cup is better than a pure plastic one, though neither is microplastic-free.
Since heat is the key trigger, a simple behavioural change can help: ask for your drink to be slightly cooler before it is poured into the disposable cup. This reduces the thermal stress on the plastic lining and can lower your overall exposure.
By understanding the interaction between heat and material, both consumers can make better choices and manufacturers can be pushed to design safer, more sustainable products for our daily routines.
