Study details

For the study, researchers looked at brain, kidney, and liver tissues from 92 people who underwent a forensic autopsy to verify their cause of death in 2016 and 2024. Samples of brain tissue were gathered from the frontal cortex, which is the area of the brain associated with thinking and reasoning and most affected by frontotemporal dementia and later stages of Alzheimer's disease.

In 2024, the levels of microplastics found in the brain tissue of normal individuals with an average age of around 45 to 50 years old "were 4,800 micrograms per gram, or 0.5% by weight," according to Matthew Campen, lead author on the study and a regents' professor of pharmaceutical sciences at the University of New Mexico.

"Compared to autopsy brain samples from 2016, that's about 50% higher," Campen said. "That would mean that our brains today are 99.5% brain and the rest is plastic."

The brain samples contained seven to 30 times more microplastics than samples that came from kidneys and liver, according to the study, and the most common type of plastic found in the samples was polyethylene, which is used in plastic bags, films, and bottles.

"Based on our observations, we think the brain is pulling in the very smallest nanostructures, like 100 to 200 nanometers in length, whereas some of the larger particles that are a micrometer to five micrometers go into the liver and kidneys," Campen said.

Microplastics are small fragments that can range in size from less than 0.2 inches — roughly the size of a pencil eraser — to one nanometer, CNN reports. For reference, a strand of human hair is around 80,000 nanometers wide. Anything smaller than one nanometer is referred to as a nanoplastic and is measured in billionths of a meter.

Nanoplastics are the most concerning plastics for human health, according to experts, because the small pieces can reside in individual cells.

"Somehow these nanoplastics hijack their way through the body and get to the brain, crossing the blood-brain barrier," Campen said. "Plastics love fats, or lipids, so one theory is that plastics are hijacking their way with the fats we eat which are then delivered to the organs that really like lipids — the brain is top among those."

When nanoplastics invade individual cells and tissues in major organs, they can potentially interrupt cellular processes and deposit endocrine-disrupting chemicals like bisphenols, phthalates, flame retardants, heavy metals, and per- and polyfluorinated substances, CNN reports.

According to the Endocrine Society, endocrine disruptors interfere with the human reproductive system and can lead to genital and reproductive malformations, as well as female infertility and declines in sperm count.

Discussion

Some experts said the findings of the study were very concerning. Sedat Gündoğdu, who studies microplastics at Cukurova University in Turkey, said that, given the study's findings, "it is now imperative to declare a global emergency" to deal with plastic pollution.

Bethanie Carney Almroth, an ecotoxicologist at the University of Gothenburg in Sweden, said that finding microplastics in more human organs "raises a lot of concerns" given what we know about the health effects of microplastics in animals, studies of human cells in labs, and other epidemiological studies. "It's scary, I'd say."

"Studies like this offer a sobering reminder of how intertwined population health is with environmental health," said Advisory Board's Ellie Wiles. "The healthcare industry produces an estimated 1.7 million tons of plastic waste per year in the United States alone. The consequences of this waste manifest not only within ecosystems, but also within our bodies," she added.

"The appearance of microplastics in human brains is just one example of many that illustrates the need for healthcare industry stakeholders to mitigate wasteful practices as a step toward improving health outcomes," Wiles said.

However, other experts said there's no cause for alarm just yet. Currently, FDA says in a statement on its website that "current scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in foods pose a risk to human health."

Phoebe Stapleton, an associate professor of pharmacology and toxicology at Rutgers University, said the increase in microplastics found in the study only shows exposure and doesn't provide information about brain damage.

"It is unclear if, in life, these particles are fluid, entering and leaving the brain, or if they collect in neurological tissues and promote disease," she said. "Further research is needed to understand how the particles may be interacting with the cells and if this has a toxicological consequence."

"Studies have found these plastics in the human heart, the great blood vessels, the lungs, the liver, the testes, the gastrointestinal tract and the placenta," said Philip Landrigan, director of the Program for Global Public Health and the Common Good and the Global Observatory on Planetary Health at Boston College.

"It's important not to scare the hell out of people, because the science in this space is still evolving, and nobody in the year 2024 is going to live without plastic," Landrigan added.

Kimberly Wise White, VP of regulatory and scientific affairs for the American Chemistry Council, said research is underway that "not only helps address current data gaps in our understanding of exposure to microplastics but it also aims to develop improved tools to measure the toxicity of microplastics to humans."

How to reduce your microplastics exposure

Experts say that it's not possible to eliminate exposure to microplastics, but you can take some steps to reduce your exposure.

"I say to people, 'Listen, there are some plastics that you can't escape. You're not going to get a cell phone or a computer that doesn't contain plastic,'" Landrigan said. "But do try to minimize your exposure to the plastic that you can avoid, such as plastic bags and bottles."

Landrigan said it's important to take food out of the plastic wrapping before you cook it or put it in the microwave. "When you heat plastic, that accelerates the movement of the microplastics out of the wrapping into the food," he said.

The Natural Resources Defense Council, an environmental advocacy group, suggests investing in a zippered fabric bag and asking your dry cleaner to return your clothes in that instead of thin, plastic sheets. It also recommends bringing a travel mug to coffee shops for takeout and silverware to the office to avoid using plastic cups and utensils.

"Don't use plastic bags when you go shopping," Landrigan said. "Use a cloth bag or a paper bag or a recycle bag. Try to avoid plastic water bottles, if you can possibly do so."

Landrigan added that you can "use a metal or glass drinking cup instead of a plastic cup. Store your food in glass containers instead of in plastic ones. Work in your local community to ban plastic bags, as many communities around the United States have now done. There is a lot you can do." (LaMotte, CNN, 8/25; Main, The Guardian, 8/21)