Your morning coffee in a plastic to-go cup could contain thousands of invisible microplastic particles that are released into the beverage due to exposure to high temperatures. A study by Australian scientists warns that in a year with this habit, a person can eat hundreds of thousands of such debris.
A typical morning for many people is to go to a coffee shop to drink hot coffee in a plastic cup and warm their hands before starting their work. This ritual seems harmless, but new research reveals its hidden costs. It turns out that such a cup, whether made entirely of plastic or paper with a thin plastic lining, will release thousands of microscopic plastic particles into the drink when exposed to hot liquid.
With around 1.45 billion disposable hot cups used annually in Australia alone and up to 500 billion globally, the scale of the potential health impact is alarming.
Scientists in Australia have begun a meta-analysis of 30 existing studies to understand the behavior of common plastics such as polyethylene and polypropylene under different conditions. The results are clear: the main factor that causes plastic to “share” its particles is temperature.
As it increases, the amount of microplastics released (particles ranging in size from dust particles to sesame seeds) can increase from hundreds to more than 8 million particles per liter of liquid. At the same time, the time the drink stays in the glass turns out to be less important – the main role is played by the initial thermal shock, when the hot liquid first comes into contact with the plastic surface.
To test these findings in a real-world setting, the researchers collected 400 cups of two main types from Brisbane cafes: all-plastic cups made from polyethylene and paper cups with plastic lining. They are tested with water at 5 degrees Celsius for cold coffee and 60 degrees Celsius for hot coffee). The results confirmed the hypothesis: matter matters.
They found that plastic-coated paper cups emitted fewer particles than all-plastic paper cups at both temperatures. They also found that heating significantly increased the transition from cold to hot water and increased the amount of microplastics released from plastic cups by about 33%. Calculations show that a person who drinks 300 ml of hot coffee in a plastic cup every day can swallow up to 363 thousand microplastic particles in a year.
Why is heat so destructive? Using high-resolution microscopes, scientists discovered that the inner surface of plastic cups has a much rougher, “cartilaginous” texture than the smooth plastic layer of paper cups. Heating softens the plastic, causing it to expand and create new microcracks and irregularities, from which particles can easily flake off and settle in the drink.
The researchers don't advocate avoiding takeout coffee altogether, but they do recommend making wise choices. The best option for hot drinks is to use a reusable cup made from a material that doesn't release microplastics: stainless steel, ceramic or glass. If you can't avoid disposable tableware, you should choose paper cups with plastic lining instead of paper cups made entirely of plastic.
And a simple but effective tip: ask the barista to cool the coffee slightly before pouring it into a plastic cup: “Reducing the temperature of the liquid will reduce the thermal stress on the plastic and, therefore, reduce the amount of beans that come off.”
