Scientists cast doubt on the discovery of microplastics throughout the human body

Calling out questionable methodology is a good thing. I want to add that the takeaway isn't that all of the research about microplastics is false. I say this because perception often seems to swing dramatically... "eggs are good for you this week, last week they were bad". The reality of course is more nuanced than what you get from headlines. Except with eggs, that's actually straightforward: they were always good.

Plastic is still bad. Particularly some of the chemicals that leach out of it as it degrades. So far no one has claimed there was anything wrong with the bulk of that science. Even without the science though, turning oil into gigatons of synthetic polymers and making a valiant effort to completely suffuse the planet with it was never a good idea.

Some of the key points of criticism from the article:

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.

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.

While analytical chemistry has long-established guidelines on how to accurately analyse samples, these do not yet exist specifically for MNPs, said Dr Frederic Béen, at Vrije Universiteit Amsterdam: “But we still see quite a lot of papers where very standard good laboratory practices that should be followed have not necessarily been followed.”

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.

Rauert also argues that studies reporting high levels of MNPs in organs are simply hard to believe: “I have not seen evidence that particles between 3 and 30 micrometres can cross into the blood stream,” she said. “From what we know about actual exposure in our everyday lives, it is not biologically plausible that that mass of plastic would actually end up in these organs.”

This is actually some of the best news I've heard in a while, given the low-key constant dread of believing we were already screwed in unknowable ways.

To me, this feels like a somewhat substantial blow to what I already viewed as fairly weak evidence of the threat of microplastics.

I had seen study after study testing for whether microplastics are present, but so few actually trying to identify the harmful results of said microplastics. I know it’s not the biggest red flag or anything, because it’s not like there are zero studies showing negative effects, but it’s definitely coloured my worldview how much the studies are weighted towards “is it present” without much “is it harmful” to be of any concern.

Knowing that this is at the edge of what we’re reliably able to detect means I’ll keep an open mind for if things shift in the next few years/decades. Maybe the same trend (studies detecting presence overwhelmingly more than studies identifying harm) was the same for tobacco or leaded fuel or asbestos, and I just wasn’t around when those discoveries were being made.