In the 1967 movie “The Graduate,” a family friend famously tells the title character “I just want to say one word to you. Just one word. Plastics. There’s a great future in plastics. Think about it.” Well, those of us engaged in the plastic space have been thinking about it. And we have a response.

While a recent review found consistent evidence of harm to human health from plastic chemicals, another study, still in peer review, suggests that the risks of exposure of humans to secondary microplastic particles themselves  – i.e., shards, curly fibers, tire shred and other particles fractured and shed from plastic products that do not meaningfully degrade –  may be unnervingly high. These results are quite different from the findings of previous studies, which have indicated that exposure of humans to manufactured plastic microbeads used in personal care products may not have significant adverse effects on health. While it has been a challenge to develop specific epidemiological studies to clearly assess the risk of exposure to environmental microplastics, we may now be closer than we thought to the microplastic smoking gun. Data in this still-under-peer-review study suggest that as plastic breaks down, non-degrading plastic particles apparently prefer to go to our brains. Yes, our brains.

This National Institutes of Health-funded study, completed at the University of New Mexico with  additional independent data analysis by Oklahoma State University, has demonstrated significant accumulation of nanoplastic shards in human brain tissue. Autopsy samples taken by the Albuquerque Office of the Medical Investigator in 2016 and 2024 included  samples from the frontal cortex of the brain.

• In the 2016 brain samples, the average concentration of microplastic was 3,057 μg/g (micrograms per gram, or parts per million), 10 to 20 times greater than the concentrations measured in samples from liver and kidney tissue,
• But in the 2024 brain samples, the average concentration of microplastic increased by about 50%, going up to 4,806 μg/g (about 0.5% by weight), with a maximum of 8,861 ug/g.

I discussed this study with author Dr. Matthew J. Campen, who noted that this study utilized a sodium hydroxide digestion process first, followed by separation of solid materials from the aqueous fraction (which includes the lipids that are transformed into lipid salts) to ensure just the remaining solids were analyzed, minimizing the possibility of overcounting or false positives. This result appears to be both significant and generally reliable. Importantly, the methods are internally consistent, thus comparisons between liver, kidney, and brain have great confidence.  Furthermore, the concentrations measured are consistent with other recent studies that have used complementary approaches to isolate the microplastics.

For context, consider that plastic is technically a form of hydrocarbon, generally originating from petroleum.  Then consider that a total petroleum hydrocarbon (TPH) concentration of 2,500 ppm is generally identified as an acceptable TPH concentration in industrial soils.  The concentration of microplastics in the 2024 brain tissue samples is  over three times the TPH concentration acceptable in industrial soils. Making matters potentially worse, microplastic  can carry up to 16,000 different chemical additives, thousands of which are as toxic as, or more toxic than, the  petroleum constituents upon which the TPH industrial soil threshold is based. And these microplastics  are  attracted to fat. Also, the surface of plastic can be electrochemically active. Thus, it is not shocking that they are concentrating in the fattiest human organ with the most electrical activity: our brains.

From a regulatory perspective, how might we address the risks of microplastic exposure ? Could we build upon what we have learned from having addressed the risks of asbestos exposure? Asbestos fibers – like many types of microplastic particles – are sharp, small, bioaccumulative and nondegrading.  And like many types of microplastic particles, asbestos was for decades used to make multitudes of products.  That high level use of asbestos came to an end after the 1964 publication of the Journal of American Medical Association article “Asbestos Exposure and Neoplasia,” which demonstrated strong associations between cancer and asbestos exposure. The 1964 article reviewed the medical histories of 632 individuals working with asbestos insulation in the 1920s and 1930s, from 1943 to 1962, 20 to 30 years after exposure, finding alarming increases in disease for those asbestos workers compared to the normal population. Asbestos is still in use (with bans), but we control the release of asbestos fibers with strict management requirements.

The similarities between asbestos and microplastic particles were pointed out in comments that several of us Global Council for Science and Environment Fellows sent to the docket for EPA’s Draft National Strategy to Prevent Plastic Pollution and in which we proposed how microplastic could be regulated more like asbestos using existing environmental regulatory authority (see also ELI’s more recent comprehensive report). We make just about everything out of plastic now, particularly consumer products. Unlike  asbestos, which affected some populations (e.g., shipbuilders) more than others, we have been making so much plastic for so long, that microplastic is now saturating our planet, and us. We are all significantly exposed to plastic, and thus microplastic. We are all the ship builders now.

So, where do we currently stand? The recent studies from NIH show how significantly brain tissue appears to accumulate microplastic. Is this enough of a smoking gun to force us to address plastic particles now?

Currently, the world is preparing to meet for INC5, to finalize an international legally binding instrument to end plastic pollution. The Road to Busan is an effort to enlist support to cap primary plastic production, problematic chemicals and plastic products of concern as part of the solution to plastic pollution. The United States has indicated it will now support such a cap of primary plastic production as well as caps for problematic chemicals and plastic products of concern. In addressing our plastic issues, we must mitigate our exposure to microplastic.