In September 2025, Nature Medicine published the most rigorous summary yet of what microplastics do to the human body. Its conclusion is unusual for a topic this loud: the indications are strong, and the evidence base is still not good enough. That gap is not a reason to ignore the issue it is a reason to be precise about which claims you accept.
The paper
| Title | Health impacts of microplastic and nanoplastic exposure |
| Type | Review Article a critical synthesis of the field, not a new experiment |
| Journal | Nature Medicine, volume 31, pages 2873–2887 |
| Published | 11 September 2025 |
| DOI | 10.1038/s41591-025-03902-5 |
| Authors | Marja H. Lamoree, Jeske van Boxel, Federica Nardella, Kas J. Houthuijs, Sicco H. Brandsma, Frederic Béen, Majorie B. M. van Duursen |
| Reach | 21,000+ accesses, 195 citations, 502 Altmetric |
| Access | Subscription (the abstract and figure list are public) |
A word on sourcing: this article is paywalled, so everything we attribute to it below comes from its published abstract and its public figure list not from its internal sections. Where we use specific numbers, they come from open-access companion papers, cited individually. If you have institutional access, read the review in full; the citation is above.
What the review concludes
The abstract opens by acknowledging the problem plainly: as evidence of microplastics and nanoplastics (MNPs) in the human body accumulates, so do concerns about what they do. It then makes three claims that deserve to be separated, because they carry very different weights.
| Claim | Status in the review |
|---|---|
| MNPs can cross biological barriers and reach tissues | Established in experimental models. The review states that MNPs “can cross cell barriers in the human lung and intestine and reach systemic circulation and subsequently tissues such as reproductive organs, placenta and brain.” |
| MNPs are associated with adverse health outcomes | Indicated, not proven. “Early clinical findings indicate that MNPs may be associated with adverse health outcomes, including immune modulation, reproductive effects and cardiovascular effects.” |
| The clinical studies are strong enough to support risk assessment | No. They “typically suffer from low patient numbers and inadequate MNP exposure assessment, which precludes adequate risk assessment.” |
Animal and cell-based work does point the same direction as the human findings the review says those outcomes “generally support the preliminary clinical findings.” But support is not equivalence, and the review does not treat it as such.
“There are strong indications that MNP exposure negatively impacts human health, but a robust evidence base is lacking.”
That sentence is the most useful thing in the paper, and it is the sentence most coverage omitted. It is not a dismissal the authors call the need for better research “urgent.” It is an admission that the field’s current tools cannot yet produce the answer everyone wants.
Why the evidence is weak — the two figures worth knowing
The review’s public figure list tells you how it is structured, and it is more revealing than most abstracts:
- Figure 1 — MNP exposure and cellular effects
- Figure 2 — Scoring of human exposure assessment studies
- Figure 3 — Scoring of in vitro studies
Figures 2 and 3 are an audit. Rather than stacking up findings, the review scores the existing studies against methodological criteria which means its central message is about the quality of the evidence, not just its direction.
The abstract names two hard problems driving that weakness. The first is exposure assessment: many human studies cannot say how much plastic a person was actually exposed to, which makes it impossible to connect a measured tissue burden to a cause. The second is a concept almost entirely absent from consumer-facing microplastic content the biocorona. The review lists polymer type, size, shape “and the presence of a biocorona, among others” as the factors determining how an MNP behaves. When a particle enters a biological fluid, proteins coat it. That coating changes how the particle is recognised, where it goes and what it does.
The practical implication of the biocorona point is uncomfortable for anyone selling certainty: a particle’s effect is not a property of the particle alone. It is a property of the particle plus the biological context it lands in. Any claim of the form “polymer X does Y in the body” is, strictly, incomplete.
What the detection evidence does show
Where the field is genuinely solid is in measuring where particles end up. The review cites the 2025 decedent study by Nihart and colleagues, published in the same journal, which used pyrolysis gas chromatography–mass spectrometry alongside electron microscopy — two independent methods — to quantify MNPs in human liver, kidney and brain tissue.
| Tissue | Median total plastics | Notes |
|---|---|---|
| Liver (2024 samples) | 433 µg/g | Comparable to kidney |
| Kidney (2024 samples) | 404 µg/g | — |
| Placenta (prior literature) | 63.4 µg/g | Included for scale |
| Testes (prior literature) | 299 µg/g | Included for scale |
| Brain (2016 samples) | 3,345 µg/g | Median; interquartile range 1,267–5,213 |
| Brain (2024 samples) | 4,917 µg/g | Median; interquartile range 4,026–5,608 |
| Brain, earlier specimens (1997–2013) | 1,254 µg/g | From eastern US brain banks |
Three further findings from that study matter for how the risk conversation should be framed:
- Brain concentrations were significantly higher than liver or kidney (P < 0.0001), and polyethylene made up roughly 75% of the polymer mass in brain tissue a higher PE proportion than in liver or kidney.
- Time of death was a significant factor (P = 0.01), with higher concentrations in 2024 than 2016 samples while age, sex, race/ethnicity and cause of death were not significant influences. Rising environmental concentrations over time, not personal demographics, tracked with tissue burden.
- Dementia cases showed far higher concentrations (median 26,076 µg/g), with visible deposition along cerebrovascular walls and in immune cells. The authors explicitly assume no causality here atrophy, impaired blood–brain barrier integrity and poor clearance would all be expected to raise measured concentrations. The direction of that relationship is not established.
On particle size, electron microscopy found that brain particulates were overwhelmingly sub-micron, with transmission electron microscopy resolving largely 100–200 nm shards or flakes. This is nanoplastic, not microplastic and it is the fraction that conventional detection methods most often miss.
The two absences that matter most in practice
A separate systematic review, published in 2025 and available open access via PubMed Central, synthesised 30 human studies 22 observational, 5 clinical trials, 3 systematic reviews using the GRADE framework. Two of its conclusions are the ones a buyer should hold onto:
There is no safe exposure threshold — and there is no established intervention
- “No established Acceptable Daily Intake (ADI) or safe exposure threshold currently exists for humans.” Without a threshold, no one can tell you whether your personal burden is high, low, or meaningful.
- “No established medical interventions are available to reduce microplastic accumulation in the human body.” This is the sentence the supplement industry does not quote. It is also the honest starting point for evaluating anything sold for this purpose.
The same review graded evidence certainty as moderate for inflammatory and endocrine biomarkers (CRP, IL-6, TNF-α, thyroid hormones, cortisol, 8-OHdG, MDA) and low for neurocognitive and chronic-disease outcomes and emphasised that its biomarker findings are “recurrent statistical associations… rather than evidence of biological causation.”
Two structural gaps sit behind those absences. First, no standardised method exists to quantify a person’s internal plastic burden, and reporting units differ across studies which is why published tissue concentrations vary so widely between research groups. Second, longitudinal studies are scarce; most work is cross-sectional and cannot follow outcomes over time.
So what follows from all this?
Reading these papers carefully produces a set of conclusions that are less dramatic than the headlines and more actionable than the panic.
1. The burden is real and rising; the specific harms are not yet pinned down
Detection is robust multiple independent methods now confirm MNPs in human tissue, and the 2016-versus-2024 comparison in brain tissue is one of the clearest signals in the field. What remains unresolved is which of those particles, at what burden, in whom, produce which outcomes. Both halves of that sentence are true at once, and honesty requires holding both.
2. Exposure reduction is the highest-confidence action available
It does not depend on resolving the causality question. Fewer particles entering the body is fewer particles that need clearing, regardless of what they would have done. That means filtered drinking water over single-use bottles (bottled water vs tap water), keeping plastic out of heat contact with food (what heating food in plastic does), ventilation against airborne fibres, and attention to where exposure concentrates at mealtimes (reducing exposure during meals). The full route-by-route picture is in microplastics in food and water.
3. Gut-compartment clearance is the only support mechanism with a direct study behind it
Because no intervention removes particles from tissue, the defensible scope for any oral product is the digestive tract particles still present there, before absorption. That is where the 2025 chitosan excretion research sits, and where its limits are equally clear. Our breakdown is in can chitosan bind microplastics and the excretion study analysis; the specification question is covered in the most effective form of chitosan, and the charge mechanism in the positive charge of chitosan.
4. Scepticism should be aimed at confident claims in both directions
Just as no supplement should claim organ detoxification, no one should claim the question is settled in either direction. A 2020 survey cited in the systematic review found only 38% of participants believed microplastics were harmful to human health meaning most people are still forming a view. The right posture is neither reassurance nor alarm, but a clear-eyed position on what is measured and what is inferred.
How to read any microplastic health claim
- Ask what was measured. Tissue detection studies measure presence, not harm. They cannot tell you an outcome was caused by plastic.
- Ask about exposure assessment. If a study cannot quantify how much plastic the subjects encountered, its health associations are weak by construction — this is the review’s core criticism.
- Watch for causation smuggled into correlation. The dementia finding is the clearest example: higher concentrations in diseased tissue may be a consequence of the disease, not a cause.
- Be sceptical of both extremes. “Proven dangerous” and “nothing to worry about” are equally unsupported by the current base.
- Treat tissue-removal claims as disqualifying. If a product promises to clear plastic from organs or blood, the published evidence does not support it — and the systematic review above says so directly.
Frequently asked questions
Has science proven that microplastics harm human health?
No. The 2025 Nature Medicine review states there are “strong indications” of negative health impacts but that “a robust evidence base is lacking.” Human clinical studies are limited by small patient numbers and inadequate exposure assessment.
What is already established?
That MNPs are present in human tissue confirmed by multiple independent analytical methods in liver, kidney, brain, blood, placenta and other tissues and that they can cross cellular barriers in experimental models. Rising concentrations are documented over time in the same tissue types.
Is there a safe level of microplastic exposure?
No accepted threshold exists. A 2025 systematic review of 30 human studies concluded that no established Acceptable Daily Intake or safe exposure threshold currently exists for humans which means no one can currently tell you what a “safe” body burden is.
Can anything remove microplastics already in the body?
Not according to the published evidence. The same systematic review states that no established medical interventions are available to reduce microplastic accumulation in the human body. Claims to the contrary from supplements, cleanses or devices are ahead of the data. The demonstrated scope for an oral binding fibre is the gastrointestinal tract.
Why do different studies report such different tissue concentrations?
Because methods are not standardised. Detection techniques, sample preparation, reporting units and tissue sampling sites all vary, and no consensus method exists for quantifying internal burden. The review identifies method maturation as a prerequisite for better human studies.
What does the “biocorona” mean for me?
It means a plastic particle’s biological behaviour is shaped by the proteins that coat it after it enters the body not by polymer type, size and shape alone. It is one reason broad claims about what a given plastic does in the body are incomplete by nature.
The bottom line
The value of the Nature Medicine review is not that it settles the debate. It is that it draws the line between what is measured and what is inferred and then says the field needs better tools before it can move that line. For anyone navigating this topic, that is more useful than a headline, because it tells you exactly which claims to accept now, which to hold loosely, and which to reject outright.
Reduce exposure, because that is certain to help and carries no downside. Support gut-compartment clearance if you choose to, understanding precisely what that can and cannot do — see how to remove microplastics from your body and the step-by-step microplastic detox protocol. And decline to buy certainty from anyone including us. Our supplement comparison and buyer’s checklist sets out the documentation standard we hold ourselves to, and our ingredient disclosure shows what that looks like in practice.
References
- Lamoree, M. H., van Boxel, J., Nardella, F., Houthuijs, K. J., Brandsma, S. H., Béen, F. & van Duursen, M. B. M. — Health impacts of microplastic and nanoplastic exposure. Nature Medicine 31, 2873–2887 (2025). DOI 10.1038/s41591-025-03902-5. Subscription access; abstract and figure list public. The primary source for this article.
- Nihart, A. J. et al. — Bioaccumulation of microplastics in decedent human brains. Nature Medicine 31, 1114–1119 (2025). Source of the tissue concentration data and the 2016-versus-2024 comparison.
- Ririe, A. K. et al. — Impact of Microplastic Exposure on Human Health (systematic review, 30 human studies, GRADE assessment). PubMed Central, open access, 2025.
- Li, X., Wang, Y., Feng, Z., Zhang, J., Xing, B., Ding, T. et al. — Microplastics and nanoplastics in matched human blood, bone, and intervertebral discs. npj Emerging Contaminants 2, 22 (2026). Open access. Cited as the tissue-accumulation follow-up to the review’s call for better human data.
- Marfella, R. et al. — Microplastics and nanoplastics in atheromas and cardiovascular events. New England Journal of Medicine 390, 900–910 (2024). PubMed record. Cited within the review for the cardiovascular association.
About this article. Chitosan Global manufactures and supplies chitosan materials across food, agricultural, environmental and specialty applications, with published specifications and third-party testing. Our position on microplastics is evidence-led: we publish what the research shows, including its limits, and we do not claim outcomes the data cannot support. We update this article as new research publishes.
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These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. This article summarises published research and is general information, not medical advice.