Newsletter #177 Microplastics: Our brains now contain more than two plastic bags worth

Newsletter about nature and science

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M.P.Gerkema

Jul 15, 2025

Microplastics: Our brains now contain more than two plastic bags worth

It once seemed like such a fantastic invention: the development of plastics. Linking simple chemical compounds from the hydrocarbon group into so-called polymers. The applications were—and still are—endless: in textiles, cosmetics, car tires, the packaging industry, construction. But by now, we’ve begun to see synthetic plastics in a different light. Their breakdown products, in the form of microplastics, are everywhere: in the oceans, on Antarctica, and in virtually all plants and animals on Earth. And recently, it was found that the human brain contains about five grams of microplastics. In dementia patients, that number is five to six times higher. Does that indicate harmful effects? That remains a topic of ongoing debate.

There are two additional problems associated with microplastics. Most are created by the weathering of synthetic polymers, but a quarter are produced directly as tiny granules: microbeads. These are used as fillers and abrasives in cosmetics, toothpaste, and industrial applications. The second issue is that many microplastics are now breaking down even further into nanoplastics, smaller than a thousandth of a millimeter. These tiny particles can penetrate intestinal and lung tissue, and even pass through the blood-brain barrier.

An estimated 200,000 tons of microplastics float in the world’s oceans. A Dutch study from July this year showed that the North Atlantic alone contains ten times as much nanoplastic—about 2.7 million tons, found both at the surface and at depths of up to 1,000 meters. According to researchers, this shocking amount cannot be cleaned up. But it does explain where the massive amount of plastic produced on Earth has ended up—until now, we couldn’t account for it. “A large part is now drifting through the oceans as minuscule particles.”

Most microplastics consist of polyethylene waste, but also many other compounds—from PET (as in PET bottles) to styrene-butadiene, i.e., synthetic rubber. Especially due to increasingly heavy SUVs, massive amounts of micro-rubber particles end up in the environment.

Today, micro- and nanoplastics are in our drinking water, in plants and animals, and in much of our food—in fish, honey, and beer, to name a few. Many particles are also now airborne. In national parks in the western United States, 1,000 tons of plastic per year were found falling from the sky in 2020.

Are these small plastic particles harmful? For now, we only have suspicions and early indications. In fish and shellfish, they disrupt reproduction. Research in Groningen showed that lung tissue stops growing due to small nylon particles. Immune cells seem to struggle with their defensive functions due to nanoplastics. There’s even a chance that dangerous viruses may hitch a ride on these nanoplastics.

This year, a major comparative study was published on the presence of microplastics in deceased individuals. Over eight years, the amount of particles in the liver and kidneys, but especially in the brain, increased significantly. In dementia patients, the increase was dramatic—about 25 grams of microplastics in the brain.

What can we do? Some hope lies in micro-organisms that might clean up our mess, but that could be an illusion. A shift to biodegradable biopolymers—which may be more expensive but break down without harmful residues—seems the logical path. For some easily avoidable uses, like microbeads in cosmetics and toothpaste, an immediate ban is inevitable. Strong efforts must be made to find alternatives, as the current situation is becoming untenable. Finally, we must rethink waste management—clean up where possible, and fully incinerate the rest, ideally with ultrafilters to capture what’s left.

Five Tips to Avoid Microplastics

Don’t drink water from plastic bottles; don’t give babies drinks from plastic bottles either.
Avoid plastic packaging—use paper bags and buy loose vegetables.
Protest against supermarkets’ packaging obsession (like cucumbers in plastic condoms). Watch for unnecessary packaging and complain.
Rinse vegetables, fruit, and any food that has been wrapped in plastic.
Avoid toothpaste or cosmetics that contain microbeads.

Menno en Erwin about Nature and Science

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