A longer excerpt that sheds light on the measurement problems which research into microplastics is facing.

A key way of measuring the mass of MNPs in a sample is, perhaps counterintuitively, vaporising it, then capturing the fumes. But this method, dubbed Py-GC-MS, has come under particular criticism. “[It] is not currently a suitable technique for identifying polyethylene or PVC due to persistent interferences,” concluded a January 2025 study led by Dr Cassandra Rauert, an environmental chemist at the University of Queensland in Australia.

“I do think it is a problem in the entire field,” Rauert told the Guardian. “I think a lot of the concentrations [of MNPs] that are being reported are completely unrealistic.”

“This isn’t a dig at [other scientists],” she added. “They use these techniques because we haven’t got anything better available to us. But a lot of studies that we’ve seen coming out use the technique without really fully understanding the data that it’s giving you.” She said the failure to employ normal quality control checks was “a bit crazy”.

Py-GC-MS begins by pyrolysing the sample – heating it until it vaporises. The fumes are then passed through the tubes of a gas chromatograph, which separates smaller molecules from large ones. Last, a mass spectrometer uses the weights of different molecules to identify them.

The problem is that some small molecules in the fumes derived from polyethylene and PVC can also be produced from fats in human tissue. Human samples are “digested” with chemicals to remove tissue before analysis, but if some remains the result can be false positives for MNPs. Rauert’s paper lists 18 studies that did not include consideration of the risk of such false positives.

I can only conclude that a better measurement method is needed. Either the vaporization of samples or the chemical digestion will have to be replaced - but what that method will be, I can't guess.

Petroleum industry-sponsored criticism, or is it legit?

That was my impression for a long time. Microplastic everywhere, all at once, suddenly? Or just plastic from pipettes, probe containers, plastic tubes in test equipment?

So, just science being science then? Disagreements have always been a part of science, and always will be. The only important factor is how they are handled. Think a study is flawed? Repeat it, and change the flaws to see if the results differ significantly. But openly discrediting any evidence (for or against a case) without testing is as unscientific as it gets. I believe the person at the end also has a point: yeah, we don't know if microplastics are as bad as they say, but better safe than sorry.

I don't get the downvotes. The article explains that many researchers pointed out methodological issues in the tests measuring microplastics and the implausibility of some results. An the criticism was made writing letters to the respective journals that published the results, i.e. at the highest level, even some authors admitted the possibility of mistakes in the results. Sounds good news to me and honestly having microplastics in the brain equivalent to a credit card was hard to believe.

And this is why the current system (the tabloidisation) of publishing is a danger to science itself, because people might lose trust in it.