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)
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.
What exactly was a commonly cited technique and where is this citation?
Regardless, you said "invalid methodology due to not recording baseline microplastic levels" when that was not the case and wasn't the letter's objection to the study's methodology.
> Thanks for calling me weird :) I guess the suggestion though is I'm paid by big plastic or something, no infact I'm just a guy reading papers who is scared of death like everyone else.
I said the trend was weird, but feel free to pick another adjective. Self contradictory, for instance. Sick of people overextrapolating from these "bombshell" microplastic papers, I will now overextrapolate from these "bombshell" methodological papers.
Look at the publications of the author of that letter and Cassandra Rauert, the lead author of the paper on detecting plastics in human blood that you linked below. Both of them have several publications on the almost universal contamination of the planet with microplastics and are clearly worried about the impact of this. Them insisting on and helping with better science from their colleagues is not laying the question to rest, it's a call to more rigorous action (literally[2]). It is scientific malpractice to call that "growing evidence that there is much less to worry about on microplastics".
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".
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)
Is there any indication on how bad this really is?
— Segregationist, Isaac Asimov, 1967: <https://archive.org/details/Fantasy_Science_Fiction_v035n04_...>
