What Happens to the Plastic in Single-Serve Coffee Pods?

Every morning, millions of Americans press a single button for a hot cup of coffee. Even if they enjoy the instant comfort, it can have hidden health costs.

Like many other kitchen products, the pods and cups used inside these coffee machines often contain plastic materials. Studies reveal that these materials can excrete microplastics, which are then released into the coffee. New research suggests that long-term exposure to microplastics in general can compromise health. By 2024, researchers showed that patients with microplastics in their arteries had a higher risk of heart attack, stroke and premature death.

“We already have evidence that many plastics and related microplastics contain hazardous chemicals that can be harmful,” says Justin Boucher, an environmental engineer and chief operating officer of the Food Packaging Forum, a nonprofit that tracks research on how the materials affect food.

Scientists are discovering that coffee pods and cups may contribute to this problem.

Reason for concern

Many coffee pods and single-serve cups contain plastics that break down as coffee is brewed. They can end up in your drink, creating a cocktail of convenience, caffeine, and microscopic debris.

Microplastics are pieces of plastic less than five millimeters in size. They have become ubiquitous due to our heavy reliance on plastic and enter our bodies in many ways. One of them is through plastic food packaging; their microplastics can migrate, along with plastic-related chemicals, into food.

Due to their small size, microplastics are absorbed and transported through the bloodstream to vital organs. Laboratory studies of human and animal cells show that they can cause inflammation, oxidative stress, and immune disorders, problems that contribute to various diseases.

What’s currently lacking is clear evidence that microplastics are directly causing these diseases, says Mohamed Abdallah, professor of environmental chemistry at the University of Birmingham in the United Kingdom. “Our understanding of the toxicity of microplastics is still in its infancy,” adds Abdallah. But he thinks we know enough for people to worry.

Just like the inside of your body, it’s important to understand the inner workings of your single-cup coffee machine. It heats the water to about 190°F, just before boiling, and forces it through the pod under high pressure. When the brewed coffee is released from the pod, the heat and pressure cause the plastic to release chemicals and fragment into tiny pieces, which then slide smoothly into the dark brown swirl.

Learn more: What happens to the plastic in dishwasher pods?

This year, Abdallah published a study on three different brands of coffee pods. When he inspected the coffee made from the pods, he discovered significant levels of microplastics. He confirmed the source of these microplastics by tracing them to the same type of plastic used to make each capsule.

Christopher Helt, a toxicologist and director of the GreenScreen Certified® program, run by the nonprofit Clean Production Action, notes “there is a clear opportunity for chemical additive migration into coffee.” But he also thinks contamination might be limited because the pods are exposed to high heat and pressure for a relatively short period of time – only about a minute.

Abdallah says results can diverge depending on the particular methods chosen to measure microplastics and associated chemicals. “Depending on what you look at, the numbers vary,” he explains. For example, studies can use different mesh sizes to filter microplastics, says Abdallah.

A 2020 paper from University of Connecticut researchers found that chemicals in plastic pods leach into coffee at low levels, but they didn’t look specifically at microplastics, as Abdallah did.

Further research is needed. “Overall, there is a lack of very reliable studies on the subject,” says Lisa Zimmermann, biologist and science communications officer at the Food Packaging Forum. But she adds that the materials in the cups and pods are “very complex and contain many different ingredients, necessary to withstand the high heat and pressure inside the machines.” With that kind of complexity, combined with high heat and pressure, “a lot more chemicals can migrate into the coffee,” Boucher says.

The U.S. Food and Drug Administration (FDA) has not yet established relevant standards for assessing exposure to microplastics in food. “The federal government hasn’t done anything specifically about microplastics,” says Tracey Woodruff, a health policy professor at the University of California, San Francisco and a former senior scientist for the U.S. government. The FDA did not respond to TIME’s request for comment.

A strong alternative

Given the research into the potential dangers, Boucher and Zimmermann say it’s helpful to take a precautionary approach. One alternative, in particular, is safer and less expensive in the long run: stainless steel pods and cups.

Stainless steel is safer to heat than plastic. “The complex chemistry needed to maintain the physical properties of plastic is not necessary to protect stainless steel,” Boucher explains. Steel pods cost more upfront, but they can be washed and used repeatedly, unlike single-use plastic. Third-party companies design them to be compatible with popular machines like Keurig and Nespresso.

Some companies are advertising pods and cups made from bioplastics that are at least partly plant-based – or intended to mimic plant-based versions – with potential health and environmental benefits. But replacements are still made of complex materials that include additives like colorants; chemicals can react in ways that companies don’t want or don’t understand, Boucher says.

Learn more: The dirty secret of alternative plastics

Biomaterials like corn starch, used in some alternative cups, have their benefits, but they could still be dangerous, Helt says. Some research suggests that bioplastics are just as toxic as other plastics.

Meanwhile, Nespresso pods are mostly made of aluminum. However, a Nespresso representative confirmed via email that their capsules contain a small amount of materials other than aluminum, which may include plastic.

Keurig, which sells the popular K-Cups coffee pods, did not respond to TIME’s requests for comment. The Plastics Industry Association, a trade association, provided no comment.

Other sources of microplastics

It’s not just plastic pods and cups that generate microplastics in your morning drink. “There are so many different paths,” Abdallah says.

One of them is the machine itself, since its internal parts are usually made of plastic, both in single-cup and drip coffee makers. In the same 2025 study, Abdallah found microplastics in coffee drinks from the machine, in addition to those from pods and cups. He analyzed an eight-year-old machine and newer machines about a year old. “The old machine released more microplastics than the two newer versions,” says Abdallah.

Considering the age of your coffee maker, consider a PVC garden chair. “After a few months or years in your garden in the sun, it can just start to disintegrate,” Boucher says. High heat has a similar effect on your machine.

Learn more: Scientists discover how toxic your products are

Single-cup machines often have plastic external water reservoirs. “It can also be a source of microplastics,” says Abdallah. The water itself can contain microplastics before it even goes through the machine. However, the coffee that comes out at the other end contains almost two-thirds more of these contaminants, Abdallah found.

And then there’s milk, if you add it. “Milk can pass through hundreds of feet of plastic tubing during its production phase,” says Boucher, which could result in more microplastics being produced.

Coffee may contain even more microplastics if you drink it from disposable paper cups; some are lined with plastic. When possible, choose glass instead, advises Abdallah. The Food Packaging Forum maintains a research database on plastics contaminating foods, including paper cups.

These other sources of microplastics, combined with long-term use of coffee pods, can add up to increase health risks. Researchers believe people can reduce risks by using stainless steel pods. Woodruff went further: she purchased a stainless steel machine.