The news continues to be bad — a new study reveals that brain samples collected in 2024 contain much higher levels of microplastics than found in similar samples collected 10 years ago. This may indicate that these tiny plastic particles may accumulate in our vital organs over time.

Scientific research has increased lately to not only find out how microplastics affect the environment and ecosystems but also to determine how they affect animals, including humans.

This post will examine what are microplastics along with the paper that examined their accumulation in the human brain.

What are microplastics?

Microplastics are fragments of any type of plastic that are less than 5.0 mm in length, according to the US National Oceanic and Atmospheric Administration and the European Chemicals Agency. The US Environmental Protection Agency defines microplastics as plastic particles ranging from 1 nm to 5 mm. They enter natural ecosystems from a variety of sources including cosmetics, clothing, construction, food packaging, and various industrial processes.

Humans consume between 39,000 and 121,000 microplastic particles per year. Individuals whose water intake is only from bottled sources may be ingesting an additional 90,000 microplastics annually, compared to 4,000 microplastics for those who consume only tap water.

A yet-to-be-published study has linked these plastics in the placenta to premature births. Microplastics have been linked to cerebral thrombosis in mouse brains. Another study showed that exposure to chemical additives found in plastics (including microplastics) may be associated with millions of deaths.

Microplastics and brain paper

In a paper published on 3 February 2025 in Nature Medicine, Alexander J Nihart, Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences, Albuquerque, NM, and colleagues investigated tissue samples from 52 human bodies that underwent autopsies in 2016 and 2024. Every single sample they tested contained microplastic particles.

Here are the key results:

• Plastic concentrations in the tissues were not influenced by age, sex, race/ethnicity, or cause of death.
• Samples from livers and kidneys had similar amounts of microplastics, the researchers found the brain samples had up to 30 times higher concentrations.
• The time of death (2016 versus 2024) was a significant factor, with increasing microplastic concentrations over time in both liver and brain samples.

Summary

The most important thing about this study is that they just showed that there were more microplastics in brain samples versus 10 years. It does not show that there are any health consequences from it, so we do not know if this is a serious problem or not.

Moreover, the small sample size means that it’s really difficult to find a correlation between the microplastics and anything, let alone causation.

What is troubling to me is that the liver and kidneys help filter and break down waste in the body, potentially increasing their contact with circulating particles. I would not be surprised if there were higher concentrations of microplastics in those tissues.

On the other hand, our brains have extra protection against contaminants – the blood-brain barrier – which ought to prevent the passage of such material. This amount of plastic in the brain is very concerning to me, especially if we find out that it has a biological effect.

Further research will be required before we overreact, but this research is very concerning. Given the ubiquity of microplastics in the environment, it’s very difficult to avoid them. It’s in the air, water, and food supply. Of course, the worldwide demand for plastics keeps growing, so we aren’t close to finding a way to rid ourselves of them.

Stay tuned. I’m sure more news about this topic is just around the corner. I just want to make sure that when you read news articles about this study, you know what it says and doesn’t say.

Citations

• Cox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. Human Consumption of Microplastics. Environmental Science & Technology 2019 53 (12), 7068-7074. DOI: 10.1021/acs.est.9b01517.
• Cropper M, Dunlop S, Hinshaw H, Landrigan P, Park Y, Symeonides C. The benefits of removing toxic chemicals from plastics. Proc Natl Acad Sci U S A. 2024 Dec 24;121(52):e2412714121. doi: 10.1073/pnas.2412714121. Epub 2024 Dec 16. PMID: 39680769; PMCID: PMC11670057.
• Huang H, Hou J, Li M, Wei F, Liao Y, Xi B. Microplastics in the bloodstream can induce cerebral thrombosis by causing cell obstruction and lead to neurobehavioral abnormalities. Sci Adv. 2025 Jan 24;11(4):eadr8243. doi: 10.1126/sciadv.adr8243. Epub 2025 Jan 22. PMID: 39841831; PMCID: PMC11753373.
• Nihart AJ, Garcia MA, El Hayek E, Liu R, Olewine M, Kingston JD, Castillo EF, Gullapalli RR, Howard T, Bleske B, Scott J, Gonzalez-Estrella J, Gross JM, Spilde M, Adolphi NL, Gallego DF, Jarrell HS, Dvorscak G, Zuluaga-Ruiz ME, West AB, Campen MJ. Bioaccumulation of microplastics in decedent human brains. Nat Med. 2025 Feb 3. doi: 10.1038/s41591-024-03453-1. Epub ahead of print. PMID: 39901044.