This story originally appeared in The Guardian as an exclusive and is republished here as part of the Climate Desk collaboration.

High-profile studies reporting the presence of microplastics throughout the human body have been thrown into doubt by scientists who say the discoveries are probably the result of contamination and false positives. One chemist called the concerns “a bombshell.”

Studies claiming to have revealed micro and nanoplastics in the brain, testes, placentas, arteries and elsewhere were reported by media across the world, including The Guardian. There is no doubt that plastic pollution of the natural world is ubiquitous and present in the food and drink we consume and the air we breathe. But the health damage potentially caused by microplastics and the chemicals they contain is unclear, and an explosion of research has taken off in this area in recent years.

Key takeaways

• Claims that microplastics are widespread throughout the human body are now being questioned. Microplastics are real — but measuring them in human tissue is extremely hard. Scientists say many detections may be due to contamination or analytical errors, not plastic particles embedded in organs.
• Several high-profile studies have been formally challenged. Researchers have raised concerns in scientific journals about missing contamination controls, weak validation steps, and biologically implausible results. But this doesn’t mean plastic pollution isn’t a serious problem. Plastic is ubiquitous in the environment, and exposure through air, food, and water is undisputed. What remains unclear is how much ends up inside the body — and what it does there.
• Overstated findings can backfire. Weak evidence risks scaring the public, distorting policy decisions, and giving industry lobbyists ammunition to dismiss legitimate environmental concerns. Scientists agree the field is still young. Better methods, clearer standards, and collaboration between medical researchers and analytical chemists are needed before firm conclusions can be drawn.
• For now, experts recommend modest precautions — not panic. Reducing plastic use around food, ventilating indoor spaces, and filtering drinking water can lower exposure, even as the science catches up.

However, micro- and nanoplastic particles are tiny and at the limit of today’s analytical techniques, especially in human tissue. There is no suggestion of malpractice, but researchers told The Guardian of their concern that the race to publish results, in some cases by groups with limited analytical expertise, has led to rushed results and routine scientific checks sometimes being overlooked.

The Guardian has identified seven studies that have been challenged by researchers publishing criticism in the respective journals, while a recent analysis listed 18 studies that it said had not considered that some human tissue can produce measurements easily confused with the signal given by common plastics.

There is an increasing international focus on the need to control plastic pollution but faulty evidence on the level of microplastics in humans could lead to misguided regulations and policies, which is dangerous, researchers say. It could also help lobbyists for the plastics industry to dismiss real concerns by claiming they are unfounded.

While researchers say analytical techniques are improving rapidly, the doubts over recent high-profile studies also raise the questions of what is really known today and how concerned people should be about microplastics in their bodies.

“The paper is a joke”

“Levels of microplastics in human brains may be rapidly rising” was the shocking headline reporting a widely covered study in February. The analysis, published in a top-tier journal and covered by The Guardian, said there was a........

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