Every morning, as predictably as the sunrise, countless people stop at a coffee shop on their way to work—unless they have already brewed a pot at home and poured some into a travel mug. Doctors, engineers, dentists, pharmacists, store clerks, movers, landscapers, house painters, road crews… everyone seems to need that cup of coffee, hot or iced.
Sipping a fragrant cup behind the wheel, whether piping hot or refreshingly cold, with coffee’s bitterness softened by sugar and the richness of cream, while the car radio plays the news or a favorite song—it is a habit that is hard to give up. It is also a familiar scene among millions of working Americans. Whether dressed in a neatly pressed suit and tie with a gold watch on the wrist, or doing physical labor in a yellow hard hat, people count on caffeine to feel alert and clearheaded as they begin another workday.
As most of us know, coffee contains caffeine, a stimulant that acts on the nervous system and brain. It increases alertness, can make the heart beat faster, and may keep us awake at night. For most healthy adults, moderate coffee consumption is generally considered safe and may offer health benefits. Too much caffeine, however, can cause anxiety, elevated blood pressure, and sleep problems.
But the issue here is not that dark, fragrant brew. It is the paper cup holding it.
Paper Cups and Plastic Lids
Yes, the cup is made of sturdy paper. But paper alone would soften, fall apart, and tear when filled with boiling water or hot coffee. That is why the inside needs a plastic lining. And to keep our hands comfortable, we may still slip a little cardboard “jacket,” or coffee cup sleeve, around the outside.
The lining is typically made from polyethylene, or PE, or a biodegradable plastic called polylactic acid, or PLA. When hot liquid is poured into the cup, the lining can shed tiny plastic particles that end up in the coffee or tea. Testing may also reveal substances known as PFAS—often called “forever chemicals”—including chemicals used to resist moisture and help keep the cup from leaking or falling apart, at least until we have finished our drink.
Research from the University of Queensland found that plastic-lined paper cups release millions of plastic particles into hot drinks. Some of these particles are thousands of times thinner than a human hair. What is more, cups lined with the bioplastic PLA released 12 times as many nanoparticles as those lined with conventional polyethylene. In other words, “eco-friendly” does not necessarily mean safer.
Although major coffee chains may describe their paper cups as compostable, the cups still need a lining or coating to keep liquids from soaking through. These coatings are, of course, quite different from the waterproofing products used in home construction. And remember: compostable, biodegradable, and recyclable do not mean the same thing.
When hot coffee comes into contact with the cup’s lining, tiny particles can be released. Reheating the coffee in a microwave can cause even more microplastics to come loose. The plastic lid deserves attention, too. Steam rises from the hot coffee, condenses underneath the lid, and drips back into the drink. Eventually, whatever plastic particles the cup and lid have released go into the drinker’s mouth, down the throat, and into the stomach.
Put simply, we may be drinking coffee with a little plastic mixed in—even though we cannot see it with the naked eye.
Scientists have linked exposure to certain PFAS, which are difficult to break down, to immune system problems and lower birth weight. Researchers have also detected potentially toxic elements, including chromium (Cr), cadmium (Cd), and nickel (Ni), in the polyethylene linings of paper cups. The hotter the liquid and the longer it sits, the more substances may leach into it. So much for leisurely sipping a cup of hot coffee or tea, taking a little swallow now and then to… keep the throat lubricated.
What Are the Risks?
Common sense tells us that swallowing enormous numbers of tiny PE and PLA particles, along with PFAS chemicals, can hardly be reassuring. Yet science has not reached a clear conclusion about what microplastics do to human health. Researchers are not telling everyone to stop using paper cups; they are urging us to pay attention. What happens over the long term remains an open question.
What we do know is that microplastics have been detected in human blood, the brain, the placenta, the testicles, and other parts of the body. Their presence has been documented. But being present in the body is different from causing disease.
To establish that microplastics cause a particular illness, scientists would need to follow large numbers of people over many years and separate the effects of microplastics from dozens of other influences, such as environmental conditions, air pollution, food, and other chemicals. That is extraordinarily difficult to do in humans. Laboratory experiments involving cells or mice have shown harm at high doses, but those results may not reflect the levels people encounter in everyday life.
If hot coffee can affect the lining inside a paper cup, what about switching to Vietnamese iced coffee with condensed milk, or a fruit smoothie served in one of those clear plastic cups with a plastic straw, so common at Vietnamese cafés?
That may not be much better.
A study published in the Journal of Hazardous Materials found that clear plastic cups have rougher interior surfaces, with tiny ridges and grooves left by the manufacturing molds. Even at cold temperatures—around 41°F, or 5°C—friction from the liquid and ice rubbing against those surfaces caused the cups to release 33% to 38% more microplastics than plastic-lined paper cups.
And that does not even account for the occasional shake to mix the ice and coffee. Who knows how many more particles might come loose from the sides and end up in the drink? Those ice cubes can act like little pieces of sandpaper, scraping against the inside of the cup. Vietnamese iced coffee served in a clear plastic cup usually comes with a paper or plastic straw as well.
Granted, paper straws can break down within a few months, reducing the problem of persistent plastic waste. But producing them takes considerably more energy and resources. Plastic straws, meanwhile, can take around 200 years to break down, leaving behind microplastics. These tiny particles have been found in the human body and in foods such as chicken, pork, beef, and ocean fish—another way they can enter our bodies when we eat.
A Word of Advice: Be Cautious
Scientists cannot promise that these products are “100% safe.” At the same time, they do not yet have enough evidence to say that using them will definitely cause a particular disease. The thinking is simple: since we do not yet know, a little caution makes sense.
Before today’s paper cups became commonplace, we drank from white foam cups, often called Styrofoam cups, made from expanded polystyrene, or EPS. These contain styrene, which the International Agency for Research on Cancer, or IARC, has classified as potentially cancer-causing in humans.
The specific effects on human health of exposure to PE and PLA linings and PFAS in paper cups have not been conclusively established. Meanwhile, styrene, associated with polystyrene foam cups, carries a cancer hazard classification.
So how do we spare ourselves the worry? By retirement, many of us have already gone through hundreds of cups of coffee in foam and paper cups during all those years of working hard to pay the bills. We may have reheated plenty of meals in foam containers, too.
At this point, the practical choice is to reach for glass, stoneware, ceramic, or a stainless steel travel mug—and get on with enjoying the years ahead with a little more peace of mind.
And if, one day, we happen to fall ill anyway, we can always blame it on… fate.
By Đức Hà
Special to HuuTri.org