Are Microplastics Linked to Cancer?

Plastic turns up everywhere in modern life for good reason. It’s adaptable, sturdy, and light. Plastic can help make cars safer and keep food fresher for longer.

But all that plastic comes with a downside. It is a major source of environmental pollution, and scientists also wonder about its long-term effects on humans.

“We’re exposed to plastic constantly, from the synthetic clothes we wear to the drinking straws we use. We are just beginning to understand how microplastic exposure affects our health, including whether it’s connected to cancer,” said Thejus Jayakrishnan, MD, an American Society of Clinical Oncology (ASCO) expert, gastrointestinal medical oncologist at the Dana-Farber Cancer Institute, and instructor at Harvard Medical School.

What are microplastics?

Microplastics are tiny pieces of plastic measuring less than 5 millimeters. This means they are smaller than a pea or a grain of rice, and many can’t be seen with the naked eye. Some plastics are designed to be that small, like the microbeads in face wash. Other microplastics form when large pieces of plastic break down, such as trash in a landfill.

Microplastics can contaminate soil, water, and air. As a result, they become part of the environment. “Microplastics can get into our bodies through many different means. We can ingest the particles through food and drink, inhale them from the air, and even absorb them through our skin from cosmetics,” said Dr. Jayakrishnan.

The human body eliminates many microplastics through the digestive, urinary, and respiratory systems. However, animal studies suggest that some microplastic particles may build up throughout the body, including in the heart, lungs, brain, reproductive organs, and digestive tract.

How do we know what causes cancer?

A carcinogen refers to any substance that has been determined to cause cancer or help cancer grow. A substance is classified as a carcinogen based on extensive research and evaluation by scientific experts and government agencies. Substances labeled as carcinogens often have varying levels of risk depending on how and when a person is exposed or how long the exposure lasts.

Do microplastics cause cancer?

At this time, there isn’t enough evidence to know if microplastics cause cancer, and if so, how. No agency has officially determined that microplastics pose health risks for humans.

Some research has found that microplastics can damage DNA, injure the lining of organs, cause inflammation, and disrupt gut health. Microplastics may also introduce bacteria, chemicals, and other toxins deeper into the body. These processes are known to promote cancer growth. One study showed that cancerous tumors have a higher level of microplastics than healthy surrounding tissue. Early research has also suggested possible links between microplastics and infertility, dementia, heart attacks, and strokes.

“Ultimately, we need more research and more data to learn how microplastics affect human health, including their role in cancer,” said Dr. Jayakrishnan.

Why it’s hard to study microplastics

Studies show that certain cancers, including breast, colorectal, and lung cancers, have been rising among adults under 50. Researchers wonder whether this trend could be the result of something in the environment. One idea is plastic, which started being used widely in the 1950s.

“Younger generations have been exposed to more plastic than older generations, and at younger ages. Plastic could be one reason for the difference in cancer rates, combined with other factors such as sedentary lifestyles and processed food,” Dr. Jayakrishnan said.

Microplastics are hard to study because many of the tools researchers use, such as test tubes, are made of plastic. Scientists have to make sure those microplastics don’t affect the research results. Other challenges include how many kinds of microplastics there are and all the different ways they enter the body. Everyone has been exposed to plastic, which makes it tough to prove a connection between microplastics and cancer.

“You can study people who drink or smoke and compare them to people who don’t. You can’t do that with microplastics,” Dr. Jayakrishnan said.

How to limit being exposed to microplastics

While it’s impossible to avoid microplastics completely, you may be able to reduce exposure to them. Even small changes to your home and lifestyle might make a difference.

Steering clear of microplastics when possible can be better for the planet, too. “Cutting down on plastic decreases your own exposure and the plastic in the environment. You can also support policies that reduce how much plastic ends up in the environment,” Dr. Jayakrishnan said.

You can:

• Limit the use of plastic materials. Choose glass, stainless steel, or biodegradable food packaging, like storage containers and reusable straws. Cover food with foil instead of plastic wrap. Limit single-use plastics, such as disposable utensils. Shop at bulk food stores where you can fill your own containers.
• Avoid heating plastic. Do not use plastic containers to store hot food or drinks. The same goes for reheating cold food. Higher temperatures release more microplastics into food.
• Use a water filter. Filtering can remove most particles from drinking water.
• Limit ultra-processed foods. The more processed a food is, the more likely it is to contain microplastics.
• Wear natural fabrics. Choose clothes made of cotton, linen, or wool.
• Adjust your shopping list. Look for personal care and household cleaning products without fragrances or exfoliants, which often contain microplastics.
• Support research. Research provides scientists with more data to better understand the effects of microplastics on human health. You can donate to organizations that research microplastics or search for studies looking for volunteer participants.

Ways to lower cancer risk

Experts urge caution about microplastics, but not panic. “We don’t yet have the full picture of how microplastics may contribute to cancer. But some scientists suspect it’s part of the bigger picture. It’s important to be mindful of other, well-known cancer risk factors,” said Dr. Jayakrishnan.

There’s no surefire way to prevent cancer, but you can help reduce your risk by making healthy choices:

• Stay away from tobacco.
• Maintain a healthy weight.
• Get regular physical activity.
• Follow a healthy eating pattern with plenty of vegetables, fruits, and whole grains.
• Limit red meat, alcohol, and sugar-sweetened beverages.
• Practice sun safety.
• Get your recommended cancer screening tests.
• Know the signs and symptoms of cancer. See your doctor if you notice changes in your body.

Learn more about carcinogens from the American Cancer Society:

• Determining if Something Is a Carcinogen
• Known and Probable Human Carcinogens
• Cancer Risk and Prevention

Dr. Jayakrishnan is an ASCO member.