Researchers analysed 191 brain tissue samples, 156 from 113 living patients undergoing tumour surgery and 35 from five healthy post-mortem donors, using laser direct infrared imaging and electron microscopy to count and identify individual plastic particles, and a heating test (pyrolysis–gas chromatography/mass spectrometry) to measure how much plastic there was by weight.
Plastic particles were present in 100% of healthy samples and 99.4% of diseased samples. Healthy brain tissue had a median of 50.3 micrograms per gram (23 samples tested by weight). Brain tissue next to gliomas had more, a median of 129.4 micrograms per gram in six samples, while the tumours themselves had less (medians of 20.1 in gliomas and 58.4 in meningiomas). PET, polyethylene, nylon and PVC were the main polymers.
This is a useful source for 'plastic in the brain' statements because it counts and identifies actual particles as well as measuring weight. Its weight measurements use the same kind of heating test as the contested 2025 Nature Medicine study, but its concentrations are about 100 times lower, a gap the study's peer reviewers also noted.
The healthy-donor group is tiny (five people), most samples came from people with brain tumours, and the study shows presence, not harm.