Pen's Nest

https://www.science.org/content/blog-post/are-there-accumulating-microplastics-human-tissue-or-not

I haven’t blogged on the microplastics-in-human-tissue reports, but they have certainly been disturbing. Over the last few years, there have been studies suggesting that such species have been accumulating in human brain tissue, the cardiovascular system, testicular tissue and more. There are obviously a lot of microplastic particles out there, considering the environmental wear on so many years of plastic packinging, etc., and it seems unlikely that they’re improving anything. But I will admit to being surprised at the idea of them accumulating in human tissues to this extent.

Well, it looks like these results are becoming the site of an analytical-techniques dispute, at least according to the Guardian. Here, for example, is a “Matters Arising” communication about the brain microplastics paper, and its authors say that the original paper does not have enough controls for its methods (pyrolysis GC/MS). They note that the sample preparation techniques used are especially tricky for brain tissue, with its very high lipid content, and that long-chain fatty acids (found naturally in such tissue) can produce polyethylene-like fragments in the GC/MS analysis. They refer to “broader, ongoing gaps in analytical rigor” in this area, and call for researchers to use standardized methods with plenty of internal controls, blank experiments, background corrections, and so on.

Similarly, the cardiovascular microplastics paper has come under similar criticism. Those authors point out that the risk of contamination of surgical tissue samples with microplastics during their collection is high, and the paper makes no mention of safeguards to deal with that problem. There were also no blank samples tested, as far as can be seen. Furthermore, the size of the particles noted was much smaller than those seen in other literature reports, with no explanation of how these differences might have come about, and the authors believe that these and other factors could make the paper’s data and conclusions unreliable. Other such criticisms accompany other prominent papers in the field.

There seems to be a general problem of groups publishing in this area who have not been sufficiently aware of all the ways that such analyses (which are getting close to the limits of detection) might go wrong. Or perhaps they haven’t been burned enough in the past! This is a tricky area, because you don’t want to see legitimate scientific criticisms used by various yahoos to proclaim that the whole idea of microplastic contamination is bogus. But if we’re going to get a handle on how much of a problem it is in biological systems -  and we certainly should - we need numbers that we can trust. 

Discussing analytical techniques and standards - disagreeing about them very much included - is an essential part of doing good analytical chemistry. That’s how science is supposed to work. Your methods, results, and ideas need to be strong enough to stand up under informed criticism, and if they aren’t, you go back and fix them or you withdraw your claims. Let’s see how this one shakes out!

https://www.science.org/content/blog-post/are-there-accumulating-microplastics-human-tissue-or-not