I Suspected As Much

 The Guardian, ‘A bombshell’: doubt cast on discovery of microplastics throughout human body

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.

 

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.

 

“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 rising trend in micro- and nanoplastics (MNPs) in brain tissue from dozens of postmortems carried out between 1997 and 2024.

However, by November, the study had been challenged by a group of scientists with the publication of a “Matters arising” letter in the journal. In the formal, diplomatic language of scientific publishing, the scientists said: “The study as reported appears to face methodological challenges, such as limited contamination controls and lack of validation steps, which may affect the reliability of the reported concentrations.”

One of the team behind the letter was blunt. “The brain microplastic paper is a joke,” said Dr Dušan Materić, at the Helmholtz Centre for Environmental Research in Germany. “Fat is known to make false-positives for polyethylene. The brain has [approximately] 60% fat.” Materić and his colleagues suggested rising obesity levels could be an alternative explanation for the trend reported in the study.

What we learn from history is that we don't learn from history. My own field of science (trace element biogeochemistry) was plagued with problems of false positives. It turned out that to get accurate trace element measurement require fanatical attention to anti-contamination  efforts.

A particularly telling example is the saga of Fritz Haber his attempt to pay off Germany's WWI debt by extracting gold from seawater. Now, Fritz Haber is a giant among chemists. His development of the  Haber process for making ammonia from nitrogen gas and methane allows mankind to sustain it's current population. Of course, for him it was a method to make nitric acid for gun powder and explosives, but it did earn him a Nobel Prize.

His preliminary attempts to extract gold from seawater suggest that it might be a viable method to get gold and pay off post-Versailles war debt. Via Google AI, "The German Atlantic Expedition (1925–1927) on the research vessel Meteor aimed to study the South Atlantic, famously utilizing sonar to map the seabed and revealing the Mid-Atlantic Ridge. Chemist Fritz Haber initiated this effort, hoping to extract gold from seawater to pay off Germany's post-WWI war debts." Of course, it turned out that the initial attempts were false positives, and that it didn't work on a large scale. Seawater contains so little dissolved gold it is almost impossible to measure, even today. 

We relearned those lessons in the 1980s when reliable measurement of some elements in seawater began to be made. I assume the people who measure low levels of organic contaminants went through the same learning curve.