Comment by reedf1
5 hours ago
There is growing evidence that there is much less to worry about on microplastics on several fronts.
1. A whole cohort of core studies have been judged to have invalid methodology due to not recording baseline microplastic levels (https://www.pnas.org/doi/10.1073/pnas.2411099121)
2. Young-onset cancers (especially colorectal cancer) which were inferred to be caused by a rise in microplastics are being linked explicitly to other mechanisms and cohorts. (https://ascopubs.org/doi/10.1200/JCO.2025.43.16_suppl.3619)
> A whole cohort of core studies have been judged to have invalid methodology due to not recording baseline microplastic levels (https://www.pnas.org/doi/10.1073/pnas.2411099121)
This does not say that and it's irresponsible to summarize it that way. That's a letter addressing a specific study from 2024 (which did record baseline levels because that's a standard experimental design step), arguing that it used an inadequate control so may have had background contamination when reporting the level of microplastics found in bottled water.
A "cohort of core studies" were not involved, and nothing was "judged to have invalid methodology". The study authors also replied, arguing that their choice of blanks was actually the better one: https://www.pnas.org/doi/10.1073/pnas.2415874121
There's been a slightly weird trend of people on HN that seem so eager to judge the microplastic story as overblown and unsupported that they're overstating and overextrapolating the smallest counter evidence into its own competing narrative, as if what we needed were more narratives. Resist this! That's not how good science or science communication is done.
"Exercise induced gastrointestinal injury"!
Can't read the full study, but it seems to be specifically about people who run ultramarathons. Which sounds like a very small subset of the general population. I doubt that tiny cohort is in any way responsible for the overall increase in bowel cancer in younger people.
I think those papers mostly show that parts of the microplastics literature were overstated or methodologically weak, not that microplastics are harmless.
The PNAS paper is a pretty good critique of contamination/baseline issues, and I agree some of the “microplastics are causing young-onset cancer” claims got ahead of the evidence.
But the broader concern still exists: people are clearly exposed constantly, particles are being found in human tissue, and there are plausible mechanisms for harm. So no, there is not "much less to worry".
I agree that there is not evidence to "not worry", but many explicit worries are being accounted for.
Also - in terms of human tissue:
"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." (https://www.theguardian.com/environment/2026/jan/13/micropla...)
and Rauert's paper (https://pubs.acs.org/doi/10.1021/acs.est.4c12599)