For many, a steaming cup of coffee to go—or cuppa tea if you are British— is the only thing that gets us out of bed and to work. After all, it is a fundamental ritual as serious for many as the Japanese tea ceremony (only instead of a geisha, we are served by a Starbucks barista). However, this miraculous drink that makes us productive can be a source of invisible pollution.
Like almost everything else in life, we are referring to microplastics, that microscopic plague that plagues modern human life. Microplastics are already in the air we breathe, the water we drink, and even the salt we use.
But if coffee is made from coffee beans, boiling water, and milk heated in a steamer… where do these microplastics come from? Well, the trap lies in the container: that single-use takeaway cup begins to disintegrate the moment you pour a hot drink into it.
How do microplastics end up in our takeaway cups?
It had always been suspected, but a study by the University of Birmingham in the United Kingdom has confirmed it. Microplastics are tiny fragments of plastic, less than 5 mm in diameter. Among these are nanoplastics, which are even smaller particles, less than 1 µm. Due to their size, nanoplastics are capable of penetrating cell walls and even tissues. The main route of entry into our drinks is the container we use every day.
The paper cups they serve in cafes—although they seem totally harmless to anyone— don’t use pure paper. Think about it, have you ever tried to make an improvised cup out of a sheet of paper? If you have, you will have soon realized that paper is a very porous material and quickly falls apart. Cellulose is not water-repellent, and you may be lucky enough to take a couple of sips before the improvised paper cup crumbles in your hands.
To prevent this from happening with coffee shop cups, these containers have an internal coating. This coating is a thin layer of plastic, usually polyethylene (PE). Although the plastic provides the necessary impermeability to carry your coffee and enjoy it for half an hour, this plastic layer is subjected to thermal stress when freshly brewed or boiling coffee is poured into it. The high heat acts as a powerful catalyst that accelerates the degradation of this polymer.
Remember when you were taught as a child that the Romans cooked with lead kitchen utensils? How could they cook with something they knew was so polluting? Well, it turns out we’re not much smarter than our ancestors.
Top Four Most Contaminated Drinks
It was already known that plastic cups could be contaminated with microplastics. The University of Birmingham study decided to go further and analyze the 150 most popular drinks in the country. They studied not only hot drinks, but also cold ones—which should not alter the behavior of the polymer in the plastic cup.
To the surprise of the research team, they found microplastics in every sample analyzed: the only thing that changed was the amount of microplastics they contained. This is where they created a contamination hierarchy, with hot tea and freshly brewed coffee taking the top spots. Here is a list of the microplastics the researchers found per liter. If you’ve ever wanted to stop spending so much money at Starbucks, this might help you save money:
- Hot tea (49 to 81 MPs/liter),
- Hot coffee (29 to 57 MPs/liter),
- Iced coffee (31 to 43 MPs/liter), and
- Iced Tea (24 to 38 MPs/liter).
Not only was the polymer-coated cup a problem; tea bags—especially the “silk-bag” variants—are made from plastic. When steeped in boiling water, this mesh releases an alarming amount of microplastics, sometimes billions per cup.
That’s why the research principle strongly recommends bringing a metal thermos from home with your favorite drink, buying your tea in bulk (instead of tea bags), and trying to avoid drinking from this type of disposable cup at all costs.