Why the human-health evidence is still thin, according to the people who review it
A Nature Medicine review from Vrije Universiteit Amsterdam concludes there are strong indications that micro- and nanoplastics harm health, and that the studies so far are too small and too poorly measured to say how much.
By Timothy Li
This site labels human-health claims as still uncertain more often than any other topic. The clearest statement of why comes from a review published in Nature Medicine in September 2025 by Marja Lamoree, Majorie van Duursen, and colleagues at Vrije Universiteit Amsterdam, who work on both the chemistry of detecting particles and the toxicology of what they do.
What the review concludes
- Micro- and nanoplastics are increasingly documented inside the human body, and experimental models show they can cross barriers in the lung and gut, enter circulation, and reach the placenta, reproductive tissues, and brain.
- Early clinical studies point to possible links with immune modulation, reproductive effects, and cardiovascular effects. Animal and cell studies broadly support those signals.
- Those human studies typically have low patient numbers and inadequate measurement of exposure, which makes real risk assessment impossible so far.
Why measurement is the bottleneck
The authors list what a particle's effect depends on: polymer, size, shape, and the biological coating it acquires in the body. Each of those has to be measured before a dose can be linked to an outcome, and each places heavy demands on the analytical method. The review formally scores the quality of the human exposure studies and the cell studies, and its reference list is dense with papers on contamination control, blank samples, and quality criteria for methods such as pyrolysis-GC/MS and micro-FTIR. Data quality is the central theme.
What they recommend
Standardise the methods for measuring exposure and for assessing effects, then run larger, better-characterised cohorts with proper exposure quantification. They call improved research on health impacts urgently needed. That is different from calling the danger established, and the difference is the whole point of the evidence labels on this site.
How to read a health headline
When a new study reports plastic in a human tissue, ask three questions. How many people, and were they selected for being ill? How was exposure measured, and were blanks run to rule out lab contamination? Did the study measure an outcome, or only presence? The carotid plaque study on the human-health page passes more of these than most, and even it is observational and unreplicated. Most tissue-detection studies answer the third question with presence alone.
Read the review in Nature Medicine · Lamoree et al., 2025