Microplastics and health: what we know and what we don't

In brief

• In 2019 the WHO said microplastics in drinking water do not appear to pose a health risk at current levels, while stressing that the evidence is limited [5].
• According to a summary of the WHO's 2022 report, the available data are of only very limited use for assessing risk to humans [7].
• A 2024 study found higher rates of heart attack, stroke and death in patients whose artery plaque contained microplastics, but its authors stress that this does not prove causation [8].

News stories about microplastics turning up in blood, arteries or other organs appear regularly. This post looks at where the evidence behind those stories actually stands: what we can say with reasonable confidence, and what we don’t know.

What we know

We are exposed

We take in micro- and nanoplastic particles through food, drinking water and the air we breathe. In 2022 the World Health Organization (WHO) published a report that looks at all three routes together [6].

Larger particles are unlikely to be absorbed

According to the WHO’s 2019 assessment of drinking water, microplastics larger than 150 micrometres are not likely to be absorbed by the human body [5]. Absorption may be higher for smaller particles, especially nano-sized ones, but the WHO describes the data on this as “extremely limited” [5].

Official assessments remain cautious

In 2019 the WHO said that microplastics in drinking water do not appear to pose a health risk at current levels, while noting that this conclusion rests on limited information [5]. Its 2022 report took a wider view, covering studies published up to December 2021 [6]. According to a summary that quotes the report directly, the authors concluded that the available data are of only very limited use for assessing risk to humans, and that this limited data provides little evidence of adverse effects in people [7].

That is not the same as “proven harmless”. The same summary says the data are of limited use mainly because study methods vary so widely. It also reports that, despite the limited evidence, the report recommends using less plastic, improving waste management and preventing plastic products from shedding particles [7].

What we don’t know

A gap in the data on small particles

The same summary describes a mismatch the report points to: exposure studies rarely measure particles under 10 micrometres, yet effect studies concentrate on exactly that size range [7]. In other words, data on how much of these particles people are exposed to are scarce.

How reliable are the measurements?

Measurement quality varies a great deal between studies. A review of 50 studies on drinking water and freshwater found that only four met all of the proposed quality criteria [10].

Measurements in human samples raise a further question. A study published in 2025 tested pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS), a technique used to measure microplastics in human blood. The authors concluded that the technique is not currently a suitable method for polyethylene (PE) or PVC in biological samples. Fats break down under heat into products like those of polyethylene, and PVC’s breakdown products are non-specific [9]. The study was on blood; its authors note that the method has also been used on arterial tissue and plaque [9].

I go into measurement in a separate post: How are microplastics measured?

Association or cause?

A study published in the New England Journal of Medicine in 2024 followed patients who had plaque surgically removed from their carotid (neck) arteries for an average of about 34 months; 257 completed follow-up. Patients whose plaque contained micro- and nanoplastics had more heart attacks, strokes and deaths from any cause [8]. The authors state plainly that their results do not prove causation, and that laboratory contamination cannot be firmly ruled out [8]. For a detailed summary, see: Microplastics in artery plaque: what the NEJM study found, and what it didn’t

References

1. [5]World Health Organization (22 August 2019). WHO calls for more research into microplastics and a crackdown on plastic pollution. https://www.who.int/news/item/22-08-2019-who-calls-for-more-research-into-microplastics-and-a-crackdown-on-plastic-pollution
2. [6]World Health Organization (2022). Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health. https://www.who.int/publications/i/item/9789240054608 (The full report was not read; cited from the WHO’s publication page.)
3. [7]Food Packaging Forum (23 September 2022). WHO report on potential human health implications of microplastics. https://www.foodpackagingforum.org/news/who-report-on-potential-human-health-implications-of-microplastics (Secondary source: a news summary of the WHO 2022 report that quotes it directly.)
4. [8]Marfella, R. et al. (2024). Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. New England Journal of Medicine, 390(10), 900–910. https://doi.org/10.1056/NEJMoa2309822
5. [9]Rauert, C. et al. (2025). Assessing the Efficacy of Pyrolysis-Gas Chromatography-Mass Spectrometry for Nanoplastic and Microplastic Analysis in Human Blood. Environmental Science & Technology, 59(4), 1984–1994. https://doi.org/10.1021/acs.est.4c12599 (Open-access full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC11800385/)
6. [10]Koelmans, A. A. et al. (2019). Microplastics in freshwaters and drinking water: Critical review and assessment of data quality. Water Research, 155, 410–422. https://doi.org/10.1016/j.watres.2019.02.054

How to cite this post

Mikroplastikveri. (2026, November 2). Microplastics and health: what we know and what we don't. https://mikroplastikveri.com/en/posts/microplastics-and-health/

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