Over the past few years, studies have suggested that plastic particles from bottles, food packaging and waste have been detected in human blood, lungs, placentas, arteries and even the brain. But a recent investigation by the Guardian suggests that some of these claims may be less robust than they first appeared.
Authors
- Michael Richardson
Professor of Animal Development, Leiden University
- Le Yang
PhD Candidate, Biological Effects of Nanomaterials, Leiden University
The idea that tiny fragments of plastic might be accumulating in human bodies is unsettling. This concern stems largely from evidence that nanoplastics - the very smallest plastic fragments - can harm animal embryos and human cells grown in the laboratory. Slightly larger particles, called microplastics, are not known to be as harmful to living things when ingested. At least, we are not aware of any studies to this effect.
The Guardian report found that some scientists think that these reports of plastics in the human body may be false alarms. They are not suggesting any scientific misconduct. Rather, they suggest that the tissue samples were unintentionally contaminated in the laboratory or, in another example, that natural body fat in the samples produced readings that looked like plastic.
For instance, in February 2025, the journal Nature Medicine published a paper in which the authors suggested "a trend of increasing MNP [microplastics and nanoplastics] concentrations in the brain and liver". But in November 2025, the same journal published a letter from another group of scientists criticising the methods used in that original paper.
Controversies such as this raise an awkward question: are small plastic particles really present throughout the human body, or is the science still too uncertain to support such claims?
Plastic pollution in our environment is not in dispute. Small plastic particles are everywhere, and so exposure is inevitable. However, detecting these particles, especially nanoparticles, in human tissue is no easy task and typically requires advanced analytical tools.
Most studies follow a similar path. A biological sample, such as blood or tissue, is collected as a biopsy during surgery or at a postmortem. The sample is then analysed using sensitive instruments designed to identify plastics based on their chemical fingerprints.
Contamination is a major challenge. Plastic fibres and fragments are everywhere: in laboratory air, operating theatres, clothing and equipment. Most problematically, plastic particles are probably in disposable labware, such as syringes, pipettes and centrifuge tubes - the very equipment used to process the tissue samples.
Even tiny amounts of plastic contaminants can overwhelm a signal when researchers are looking for extremely small particles in equally small numbers.
Standard practice in analytics is to run blank samples alongside real ones, or use tissue samples that are less likely to contain plastics (such as chicken embryos sealed inside the egg) to show how much background contamination is in the laboratory. Critics argue that some studies did not always compare the human samples with such "controls".
We have to remember that the studies criticised by some scientists in the Guardian article were sincere attempts to answer an urgent question in a rapidly growing field. Regardless of the particular debate over each study criticised, the issues raised highlight that the entire field of detecting microplastics inside the human body is still very new, and many teams are working hard to find the best analytical techniques.
Disagreement and correction are part of how science works, and controversies are to be expected - especially when a topic attracts such intense public attention.
Scientists may be studying the wrong type of plastic particle
As noted earlier, small plastic particles fall into two broad categories: microplastics (typically the size of pollen grains) and the much smaller nanoplastics (the size of some viruses). Microplastics are fairly easy to detect, but nanoplastics are so small that only the most advanced techniques can identify them.
Most studies reporting plastic particles in the human body have focused on microplastics because they are easier to detect. Yet nanoplastics may be far more relevant to human health. Nanoplastics can cross biological barriers, are toxic to human cells grown in petri dishes and, in studies we have conducted, have been shown to harm developing embryos in animal studies.
Nanoplastics can also be taken up by cells, causing cellular damage or cell death . By contrast, microplastics are mostly too large to be taken up into cells.
This does not mean that microplastics are harmless, however. It is at least possible that they are recognised as foreign by the immune system and cause inflammation, although more research is needed to explore this possibility. Microplastics can also act like tiny sponges, soaking up toxic chemicals, such as persistent organic pollutants, from the environment and potentially carrying them into the body.
Controversies about the true risks posed by small plastic particles may create the false impression that the entire field is in question - which it is not. That is why researchers who work on measurement methods have been especially vocal about the need for higher standards. The good news is that those standards are improving quickly.
Laboratories are becoming more aware of contamination risks. Multiple analytical techniques are increasingly being used on the same samples to cross-check results. Hopefully, researchers will be able to develop standard operating procedures for analysing microplastics in human tissues and other biological samples.
If you have read alarming headlines about small plastic particles, the current state of knowledge calls for caution rather than panic. There is no clear evidence yet that large amounts of plastic are building up in human organs, or that reported increases over time reflect real biological trends rather than methodological errors.
At the same time, it may be sensible to reduce everyday exposure to plastic particles where practical. We can try to avoid food and drink that has come into contact with plastic packaging or containers, improve indoor ventilation, and use simple water filtration, such as charcoal filters, to reduce exposure .
The intense debate about these studies may feel unsettling, but it reflects an emerging scientific field finding its footing. As methods improve and human tissues are tested more rigorously, the picture will become clearer. What matters most is that claims about plastics in the human body are backed by robust evidence.
Michael Richardson receives funding from Nederlands Wetenschappelijk Organisatie (Duch Government Funding Agency).
Le Yang receives funding from China Scholarship Council and Nederlands Wetenschappelijke Organisatie (Dutch Government Funding Agency) .
