The real microplastics problem isn’t in your brain

FD Flam, Tribune News Service

In the realm of horror, it was hard to beat the headlines last February that you were carrying around the equivalent of a plastic spoon’s worth of microplastics in your brain. The findings, reported in Nature Medicine, generated lots of outrage on morning talk shows and were even repeated as fact by would-be surgeon general Casey Means. A number of chemists were initially skeptical of the study, which was based on analysing brains from a small sample of cadavers. In a rebuttal published last month in Nature, a group of chemists argued that the technique used couldn’t accurately distinguish fat particles that are a normal part of the brain from microplastics, and that the study didn’t include the necessary validation steps to ensure they weren’t simply seeing post-mortem contamination or otherwise misleading themselves.

When I wrote to chemist Fazel Monikh at the University of Padua in Italy, an author of the rebuttal, he responded that the initial claim was extraordinary because, “such particle loads would cause catastrophic occlusion, inflammation, and tissue destruction incompatible with life.” And the analysis didn’t constitute extraordinary evidence — or even reasonably good evidence. That’s not to say the proliferation of tiny plastic particles isn’t a serious problem. A review paper published last month lists ways microplastic particles might damage your brain and increase the risk of Alzheimer’s and Parkinson’s diseases. However, it also lost credibility by citing the plastic-spoon claim without caveats.

This raises an important ethical question: Is it OK for scientists, science journals and journalists to be less rigorous or critical of extraordinary results if they raise awareness of serious problems or otherwise contribute to the greater good? Mark Jones, a retired chemist who has independently studied microplastics, drew my attention to the Nature follow-up, which the journal did not publicise as heavily as it had promoted the initial findings with a splashy press release. Jones said he’s deeply concerned about scientists and journals failing to maintain high standards of evidence. He is worried about eroding public trust, as evidenced by the rising resistance to essential vaccines. Before the plastic spoon image, there was another alarming statistic: that the average person ingests enough plastic each week to make up a credit card. That claim was based on a 2019 study that used several models to estimate that the average person consumes either 0.1 g, 0.3 g, or 5 g (the credit card amount) per week.

Jones noted that other scientists questioned the assumptions in that model, and a couple of studies found that the 5-gramme figure was about a factor of a million too high, meaning it would take roughly 23,000 years to consume the amount of plastic in a credit card. Nevertheless, the credit card estimate continues to be propagated in popular media, policy circles and other studies. In the “plastic spoon” study, the initial intentions were good. Researchers from the University of New Mexico designed the study to solve a significant problem. There’s longstanding evidence that our food and water are contaminated with microplastics, but scientists don’t know where they go in the body, whether they’re excreted or get lodged in our organs, and how they affect our health.

Those questions have been difficult to answer because plastic inside the body is tough to measure. The team approached the problem by taking samples of organs from cadavers and dissolving them, removing presumably normal tissue and leaving behind a residue of what might be plastic. They analysed the residue with a technique called pyrolysis-gas chromatography-mass spectrometry — a way to identify what’s there by the masses of broken-up fragments. The end result was a wide range of plastic concentrations in the different bodies. It was surprising that the brain appeared to take up much more plastic than the other organs, as if it were preferentially absorbing it. Almost all the plastic was one type — polyethylene — with a notable absence of other common forms, such as polyethylene terephthalate (PET), which makes up plastic water and soda bottles.

The analysis could have been described as a good start — a first attempt at answering a difficult question. Some skeptical chemists were quoted in the media, but most of the public just saw clickable headlines or TV outrage, taking these very preliminary findings as fact. “Who bears responsibility when extraordinary claims enter science and policy without solid evidence?” Monikh wrote in a LinkedIn post. The journals Nature and Nature Medicine deserve some blame for the way they publicized the paper on the plastic spoon, but not for the follow-up. Journalists also deserve blame for uncritically promoting a single study as fact. In the end, there’s no ethical justification for selective hype by journals or for the lack of skepticism among journalists and researchers. We don’t need to exaggerate claims to generate concern over microplastics and their potential harm to us and other living things. And promoting studies lacking rigor could backfire and breed cynicism or a sense of doom, rather than care or action. None of us is in a position to judge which falsehoods might benefit people. We should stick to the truth as best we understand it, and still do what we can to fight the pollution of our environment by plastic.